Review Cards - Microbiology Flashcards
Biosafety levels - Level I - risk
minimal
Biosafety levels - Level I - types of agents
those not known to cause disease in healthy adults
Biosafety levels - Bacillus subtilis
Level I
Biosafety levels - Mycobacterium gordonae
Level I
Biosafety levels - soil microbes
Level I
Biosafety levels - Level I - precautions
-standard microbiological practices
-no special equipment
Biosafety levels - Level II - risk
moderate
Biosafety levels - Level II - types of agents
common human pathogens
Biosafety levels - Enterohemorrhagic E. coli
Level II
Biosafety levels - Salmonella
Level II
Biosafety levels - HIV
Level II
Biosafety levels - HBV
Level II
Biosafety levels - influenza
Level II
Biosafety levels - Level II - precautions
-biological safety cabinet (BSC) I or II
-PPE
-autoclave must be available
-limited access
-most micro labs fall in this category
Biosafety levels - Level III - risk
high
Biosafety levels - Level III - types of agents
those that may cause serious or lethal disease via inhalation.
-effective treatment available
Biosafety levels - Bacillus anthracis
Level III
Biosafety levels - Francisella
Level III
Biosafety levels - Brucella
Level III
Biosafety levels - Mycobacterium tuberculosis
Level III
Biosafety levels - Rickettsia rickettsii
Level III
Biosafety levels - Coxiella burnetii
Level III
Biosafety levels - mold stages of systemic fungi
Level III
Biosafety levels - Level III - precautions
-biological safety cabinet (BSC) I or II
-PPE
-autoclave must be available
-limited access
-negative air flow
-sealed windows
Biosafety levels - Level IV - risk
extreme
Biosafety levels - Level IV - types of agents
those that pose a high risk of life-threatening disease
-may be transmitted by aerosols
-no vaccine or therapy
Biosafety levels - Ebola virus
Level IV
Biosafety levels - Lassa virus
Level IV
Biosafety levels - hemorrhagic fevers
Level IV
Biosafety levels - Level IV - precautions
-class III BSC
-full-body, air-supplied positive pressure suit
-independent unit with specialized ventilation & waste management to prevent release into environment
CDC Classification of Biological Agents - Category A - priority
highest
CDC Classification of Biological Agents - Category A - spread
easily disseminated or transmitted from person to person
CDC Classification of Biological Agents - Category A - impact
high mortality, potential for major public health impact
CDC Classification of Biological Agents - Category B - priority
2nd highest
CDC Classification of Biological Agents - Category B - spread
moderately easy to disseminate
CDC Classification of Biological Agents - Category B - impact
moderate illness, low death rate
CDC Classification of Biological Agents - Category C - priority
3rd highest
CDC Classification of Biological Agents - Category C - spread
could be engineered for mass dissemination
CDC Classification of Biological Agents - Category C - impact
high morbidity/mortality, major public health impact
CDC Classification of Biological Agents - Bacillus anthracis
Category A
CDC Classification of Biological Agents - Yersinia pestis
Category A
CDC Classification of Biological Agents - Francisella tularensis
Category A
CDC Classification of Biological Agents - Clostridium botulinum toxin
Category A
CDC Classification of Biological Agents - smallpox
Category A
CDC Classification of Biological Agents - hemorrhagic fever viruses (Ebola, Marburg, Lassa, Machupo)
Category A
CDC Classification of Biological Agents - Brucella
Category B
CDC Classification of Biological Agents - Salmonella
Category B
CDC Classification of Biological Agents - Shigella
Category B
CDC Classification of Biological Agents - E.coli 0157:H7
Category B
CDC Classification of Biological Agents - Burkholderia mallei
Category B
CDC Classification of Biological Agents - Burkholderia pseudomallei
Category B
CDC Classification of Biological Agents - Chlamydia psittaci
Category B
CDC Classification of Biological Agents - Coxiella burnetii
Category B
CDC Classification of Biological Agents - Clostridium perfringens toxin
Category B
CDC Classification of Biological Agents - ricin toxin
Category B
CDC Classification of Biological Agents - staphylococcal enterotoxin B
Category B
CDC Classification of Biological Agents - Rickettsia prowazekii
Category B
CDC Classification of Biological Agents - viral encephalitis viruses
Category B
CDC Classification of Biological Agents - Vibrio cholerae
Category B
CDC Classification of Biological Agents - Cryptosporidium parvum
Category B
CDC Classification of Biological Agents - Nipah virus
Category C
CDC Classification of Biological Agents - hantavirus
Category C
Biological Safety Cabinets - open front; unsterilized room air enters; air passes through high efficiency particulate air (HEPA) filter before being exhausted - class of BSC?
Class I
Biological Safety Cabinets - laminar flow cabinets with variable sash opening; air passes through 1 HEPA filter before reaching work surface & 2nd one before being exhausted - class of BSC?
Class II
Biological Safety Cabinets - completely enclosed; negative pressure; air is filter sterilized comin in & going out; gloves are attached to front - class of BSC?
Class III
Which class of BSC is most commonly used in hospital micro labs?
Class II
Which class of BSC provides minimal personnel protect and doesn’t protect work surface?
Class I
Which class of BSC provides protection for the worker & work?
Class II
Which class of BSC provides maximum protection and is used in labs that work with extremely hazardous organisms?
Class III
Sterilization & Disinfection - Temperature - steam under pressure
-autoclave
-most widely utilized in clinical labs
-15 lb of pressure for 15 min (for media)
-121C/250F
-Kills spores
-may not kill prions
Sterilization & Disinfection - Temperature - boiling
-not reliable
-spores may not be killed
Sterilization & Disinfection - Temperature - pasteurization
-used in food industry to kill foodborne pathogens
-doesn’t sterilize
-liquid is heated to 71.7*C for 15 minutes
Sterilization & Disinfection - Temperature - hot air sterilization
-used when steam may damage or fail to penetrate
-2 hours at 170*C
-kills spores
Sterilization & Disinfection - Temperature - incineration
-used to sterilize inoculating loops & biomedical wastes
Sterilization & Disinfection - Filtration
-used to sterilize liquids that are thermolabile (e.g., urea broth)
-HEPA air filters are used in BSC
Sterilization & Disinfection - Radiation
UV light wavelengths in the 200-320 nm range are used for surface disinfection both in the lab and patient rooms
Sterilization & Disinfection - Chemicals - alcohols
-ethyl & isopropyl (70-80%) frequently used as antiseptics & disinfectant
-does NOT kill spores
Sterilization & Disinfection - Chemicals - chlorine compounds
-sodium hypochlorite (household bleach)
-one of the most effective agents against HIV & HBV
-10% solution
-CAN kill spores
Sterilization & Disinfection - Chemicals - Glutaraldehyde
-effective against most vegetative cells other than mycobacteria
-used for cold sterilization of items damaged by heat, e.g., inhalation therapy equipment, equipment with optical lenses such as endoscopes
Sterilization & Disinfection - Chemicals - Hydrogen peroxide
3%-6% solution used as disinfectant
Sterilization & Disinfection - Chemicals - iodine & iodophors
-iodophors (e.g., providone-iodine) release iodine slowly & are less irritating & nonstaining
-effective skin disinfectant
-used with alcohol on skin prior to collection of blood for blood culture
Sterilization & Disinfection - Chemicals - Phenolic compounds
0.5%-3% solution for disinfecting
-does NOT kill spores
Sterilization & Disinfection - Chemicals - Quaternary ammonium compounds
-effective against wide range of vegetative bacteria
-NOT effective against spores, mycobacteria, or non-enveloped viruses
-used to disinfect floors, walls, furniture
Sterilization & Disinfection - Gases - ethylene oxide
widely used in hospitals to sterilize materials that can’t withstand steam
Anaerobes - preservative or transport device
Aspirates preferred to swabs.
Anaerobic transport system to eliminate O2.
Anaerobes - storage temperature (unpreserved)
25*C
do not refrigerate
CSF - preservative or transport device
None
CSF - storage temperature (unpreserved)
Storage not recommended, process immediately
Neisseria gonorrhoeae - preservative or transport device
Amies transport medium with charcoal, JEMBEC plates, Gono-Pak, BioBag (best to inoculate medium directly)
Neisseria gonorrhoeae - storage temperature (unpreserved)
25*C
don’t refrigerate
Sputum - preservative or transport device
None
Sputum - storage temperature (unpreserved)
4*C
Stool for culture - preservative or transport device
Transport media - e.g., Cary-Blair transport medium (has high pH and sodium thioglycollate added) I’d specimen can’t be cultured within 2 hrs of collection
Stool for culture - storage temperature (unpreserved)
4*C
-best to process without delay
-refrigeration may kill Shigella
Stool for ova & parasites - preservative or transport device
Depending on procedures to be performed: polyvinyl alcohol (PVA), 10% formalin, sodium acetate-acetic acid-formalin (SAF), merthiolate-iodine-formalin (MIF), others without formaldehyde or mercury (e.g., Ecofix, Parasafe)
Stool for ova & parasites - storage temperature (unpreserved)
Can hold formed specimens at 4*C
-soft or liquid specimens should be examined immediately or preserved
Urine - preservative or transport device
Transport tubes with boric acid-glycerol if specimen can’t be processed within 2 hrs of collection
Urine - storage temperature (unpreserved)
4*C for not more than 24 hrs
Viruses - preservative or transport device
Collect during acute phase of infection (2-3 days)
-use viral transport medium (VTM)
Viruses - storage temperature (unpreserved)
4C
-for delay >24 hrs, freeze at -70C
Criteria for rejection of specimens in microbiology - unlabeled or improperly labeled specimen - reject?
reject
Criteria for rejection of specimens in microbiology - improper collection site - reject?
reject
Criteria for rejection of specimens in microbiology - prolonged transit time (over 2 hrs without preservation) - reject?
reject
Criteria for rejection of specimens in microbiology - improper temperature during transport or storage - reject?
reject
Criteria for rejection of specimens in microbiology - leaking specimens - reject?
reject
Criteria for rejection of specimens in microbiology - specimens in non-sterile containers - reject?
reject
Criteria for rejection of specimens in microbiology - dry swab - reject?
reject
Criteria for rejection of specimens in microbiology - improper swab, e.g., wood or calcium alginate for viruses or Chlamydia - reject?
reject
Criteria for rejection of specimens in microbiology - syringes with needles attached - reject?
reject
Criteria for rejection of specimens in microbiology - culture for anaerobes requested on inappropriate sources or not received in anaerobic transport tube - reject?
reject
Criteria for rejection of specimens in microbiology - specimens received in formalin - reject?
reject
Criteria for rejection of specimens in microbiology - saliva instead of sputum - reject?
reject
Criteria for rejection of specimens in microbiology - foley catheter tip - reject?
reject
Criteria for rejection of specimens in microbiology - insufficient quantity - reject?
reject
Criteria for rejection of specimens in microbiology - formed stool for C. difficile toxin testing - reject?
reject
Criteria for rejection of specimens in microbiology - swab for acid-fast bacilli (AFB) or fungal smear and culture - reject?
reject
List organisms that frequently require special collection and processing.
- Anaerobes
- Chlamydia
- Haemophilus influenzae
- Neisseria gonorrhoeae
- Neisseria meningitidis
- Salmonella
- Shigella
- Shigella
- Streptococcus pneumoniae
- Viruses
- Parasites
Gram stain - reagent - crystal violet:
-Function?
-Outcome?
Function: primary dye
Outcome: stains all bacteria purple
Gram stain - reagent - Iodine:
-Function?
-Outcome?
Function: mordant
Outcome: reacts with crystal violet to form a complex that incorporates into peptidoglycan
Gram stain - reagent - 95% ethyl alcohol or acetone or combination:
-Function?
-Outcome?
Function: decolorizer
Outcome: removes crystal violet from gram-negative (neg) bacterial cells
Gram stain - reagent - Safranin:
-Function?
-Outcome?
Function: counterstain
Outcome: stains gram-negative bacterial cells pink
Staining properties of gram-positive & gram negative bacteria - Gram Positive - cell wall
Thick peptidoglycan layer with teichoic acid & lipoteichoic acid.
-teichoic acid cross-links prevent decolorization in Gram stain
Staining properties of gram-positive & gram negative bacteria - Gram Positive:
Stained by?
Color in gram stain?
Stained by crystal violet.
Color in gram stain: purple
Staining properties of gram-positive & gram negative bacteria - Gram Negative - cell wall
Thin peptidoglycan layer covered with proteins, phospholipids, & lipopolysaccharides.
-decolorizing agent causes increased permeability of lipid-rich cell wall
-primary stain (crystal violet) washes out
Staining properties of gram-positive & gram negative bacteria - Gram Negative - cell wall
Thin peptidoglycan layer covered with proteins, phospholipids, & lipopolysaccharides.
-decolorizing agent causes increased permeability of lipid-rich cell wall
-primary stain (crystal violet) washes out
Staining properties of gram-positive & gram negative bacteria - Gram Negative:
Stained by?
Color in gram stain?
Stained by safranin.
Color in gram stain: pink
Types of culture media - nutritive
-supports growth of most non-fastidious bacteria
Types of culture media - nutrient agar
nutritive
Type of culture media - trypticase soy agar
nutritive
Type of culture media - sheep blood agar (SBA)
enrichment
Type of culture media - chocolate agar (CHOC)
enrichment
Type of culture media - brain-heart infusion
enrichment
Type of culture media - buffered charcoal-yeast extract (BCYE) agar
enrichment
Type of culture media - Columbia colistin-nalidixic acid (CNA) agar
selective
Type of culture media - eosin methylene blue (EMB)
selective and differential
Type of culture media - MacConkey (MAC)
selective and differential
Type of culture media - Hektoen enteric (HE)
selective and differential
Type of culture media - xylose lysine deoxychocolate (XLD)
selective and differential
Type of culture media - Thayer-Martin
selective
Type of culture media - enrichment
-contains added growth factors, e.g., blood, vitamins, yeast extract
Type of culture media - selective
-contains additives such as dyes, bile salts, alcohols, acids, or antibiotics to inhibit growth of certain bacteria (e.g., gram pos)
Type of culture media - differential
-contains compounds that allow certain bacteria (or even species) to be visually differentiated (e.g., lactose fermentation, hydrogen sulfide [H2S], production)
Routine media for aerobes and facultative anaerobes - sheep blood agar (SBA) - type?
-enrichment
-differential
Routine media for aerobes and facultative anaerobes - sheep blood agar (SBA) - for isolation of?
-most non-fastidious bacteria
Routine media for aerobes and facultative anaerobes - sheep blood agar (SBA):
Composed of?
Allow differentiation of?
tryptic soy agar with 5% sheep blood
-allows differentiation of hemolysis
Routine media for aerobes and facultative anaerobes - chocolate agar (CHOC) - type?
enrichment
Routine media for aerobes and facultative anaerobes - chocolate agar (CHOC) - for isolation of?
fastidious organisms including Haemophilus & Neisseria
Routine media for aerobes and facultative anaerobes - chocolate agar (CHOC):
Supplies what factors?
Incubated?
supplies X (hemin) & V (NAD) factors
-incubate in 5% CO2
Routine media for aerobes and facultative anaerobes - Columbia colistin-nalidixic acid (CNA) agar - type?
selective
Routine media for aerobes and facultative anaerobes - Columbia colistin-nalidixic acid (CNA) agar - for isolation of?
gram-positive cocci (GPC), especially from wound & stool culture
Routine media for aerobes and facultative anaerobes - Columbia colistin-nalidixic acid (CNA) agar - what does colistin & nalidixic acid do?
Colistin & nalidixic acid suppress most gram-negative (GN)
-contains 5% sheep blood but should not be used to observe hemolytic reactions.
Routine media for aerobes and facultative anaerobes - Phenylethyl alcohol agar (PEA) - type?
selective
Routine media for aerobes and facultative anaerobes - Phenylethyl alcohol agar (PEA) - for isolation of?
gram-positive cocci (GPC) & anaerobic gram-negative rods (GNR)
Routine media for aerobes and facultative anaerobes - Phenylethyl alcohol agar (PEA) - what does phenylethyl alcohol do?
Phenylethyl alcohol inhibits enteric GNR
-contains 5% sheep blood
Routine media for aerobes and facultative anaerobes - brain heart infusion agar - type?
enrichment & selective
Routine media for aerobes and facultative anaerobes - brain heart infusion agar - for isolation of?
fastidious and non-fastidious organisms (anaerobes included)
Routine media for aerobes and facultative anaerobes - brain heart infusion agar - useful for culturing?
useful for culturing streptococci, pneumococci, and meningococci
Routine media for aerobes and facultative anaerobes - brain heart infusion agar - what can be added to detect VRE?
vancomycin
VRE = vancomycin-resistant enterococci
Routine media for aerobes and facultative anaerobes - eosin methylene blue (EMB) - type?
selective & differential
Routine media for aerobes and facultative anaerobes - eosin methylene blue (EMB) - for isolation of?
enteric gram negative rods (GNR)
Routine media for aerobes and facultative anaerobes - eosin methylene blue (EMB):
Function of eosin and methylene blue?
Lactose fermenters?
E.coli?
Non-lactose fermenter?
-eosin & methylene blue inhibit gram positive (GP)
-LF = green-black or purple
-E.coli = green metallic sheen
-NLF = colorless or light purple
Routine media for aerobes and facultative anaerobes - MacConkey (MAC) agar - type?
selective & differential
Routine media for aerobes and facultative anaerobes - MacConkey (MAC) agar - for isolation of?
enteric gram negative rods (GNR)
Routine media for aerobes and facultative anaerobes - MacConkey (MAC) agar:
-Function of bile salts & crystal violet?
-Lactose fermenters?
-Non-lactose fermenters?
-bile salts & crystal violet inhibits most GP
-LF = pink
-NLF = colorless
Routine media for aerobes and facultative anaerobes - Sorbitol MacConkey (SMAC) agar - type?
selective
Routine media for aerobes and facultative anaerobes - Sorbitol MacConkey (SMAC) agar - for isolation of?
E. coli 0157:H7
Routine media for aerobes and facultative anaerobes - Sorbitol MacConkey (SMAC) agar:
-E. coli 0157:H7?
-Doesn’t ferment sorbitol = colorless colonies
-Some labs have stopped using because non-0157 serotypes can be pathogens
Routine media for aerobes and facultative anaerobes - Hektoen enteric (HE) - type?
selective & differential
Routine media for aerobes and facultative anaerobes - Hektoen enteric (HE) - for isolation of?
Salmonella & Shigella in stool
Routine media for aerobes and facultative anaerobes - Hektoen enteric (HE):
-Function of bile salts, bromothymol blue, & acid fusion?
-Nonpathogens?
-Non-lactose fermenters?
-H2S positive?
-Bile salts, bromothymol blue, & acid fuchsin inhibit normal GI flora
-Nonpathogens = orange to salmon pink
-NLF = green to blue-green
-H2S pos colonies = black precipitate
Routine media for aerobes and facultative anaerobes - xylose lysine deoxycholate (XLD) - type?
selective & differential
Routine media for aerobes and facultative anaerobes - xylose lysine deoxycholate (XLD) - for isolation of?
Salmonella & Shigella in stool
Routine media for aerobes and facultative anaerobes - xylose lysine deoxycholate (XLD):
-Function of deoxycholate?
-4 types of colonies?
-Deoxycholate inhibits many GNR & GP
-4 types of colonies:
1. yellow (e.g., E. coli)
2. yellow with black centers (e.g., some Proteus species)
3. colorless or red colonies (e.g., Shigella)
4. red colonies with black centers (e.g., Salmonella)
-Some shigellae may be inhibited.
-Some salmonellae may not produce H2S
Routine media for aerobes and facultative anaerobes - Salmonella-Shigella (SS) agar - type?
selective
Routine media for aerobes and facultative anaerobes - Salmonella-Shigella (SS) agar - for isolation of?
Salmonella & Shigella in stool
Routine media for aerobes and facultative anaerobes - Salmonella-Shigella (SS) agar:
-Function of brilliant green & bile salts?
-Ferment lactose?
-Produce H2S (black center)?
-brilliant green & bile salts inhibit other enterics.
-Salmonella & Shigella DO NOT ferment lactose - colorless colonies
-Salmonella produces H2S (black center)
Routine media for aerobes and facultative anaerobes - Deoxycholate-citrate agar - type?
selective
Routine media for aerobes and facultative anaerobes - Deoxycholate-citrate agar - for isolation of?
Salmonella & Shigella
Routine media for aerobes and facultative anaerobes - Deoxycholate-citrate agar - inhibits?
other non-pathogenic enterics
Routine media for aerobes and facultative anaerobes - Thioglycolate medium - type?
enrichment
Routine media for aerobes and facultative anaerobes - Thioglycolate medium - for isolation of?
Campylobacter from stool, wound cultures
Routine media for aerobes and facultative anaerobes - Thioglycolate medium - subculture to?
Campy-selective agar after overnight incubation at 4*C
Routine media for aerobes and facultative anaerobes - Campylobacter blood agar (Campy BAP) - type?
Enrichment & selective
Routine media for aerobes and facultative anaerobes - Campylobacter blood agar (Campy BAP) - for isolation of?
Campylobacter from stool
Routine media for aerobes and facultative anaerobes - Campylobacter blood agar (Campy BAP) - incubation?
Incubate plates in 5% CO2 at 42*C
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - Modified Thayer-Martin (MTM) - composed of?
Vancomycin
Colistin
Nystatin
Trimethoprim (TMP)
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - Modified Thayer-Martin (MTM) - function of Vancomycin, colistin, nystatin, and trimethoprim?
inhibit growth of normal genital flora
-some N. gonorrhoeae may be inhibited
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - Modified Thayer-Martin (MTM) - incubation?
incubate in increased CO2
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - Martin-Lewis - similar to?
similar to Thayer-Martin, but different antibiotics - inhibits YEAST better
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - Martin-Lewis - incubation?
incubate in increased CO2
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - New York City medium (NYC) - incubation?
incubate in increased CO2
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - New York City medium (NYC) - inhibited? Growth?
Some N. gonorrhoeae are inhibited by antibiotics.
Genital mycoplasmas will grow.
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - GC-LECT - antibiotics?
Contains antibiotics to inhibit gram positive & gram negative bacteria and yeast
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - JEMBEC plates - function?
For transportation & growth of N. gonorrhoeae
Selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis - JEMBEC plates - contain?
Plates contain Neisseria-selective medium & come with resealable polyethylene bag & CO2-generating tablet.
–NO need to transfer to a culture plate.
List the selective media for isolation of Neisseria gonorrhoeae and Neisseria meningitidis.
- Modified Thayer-Martin (MTM)
- Martin-Lewis
- New York City medium (NYC)
- GC-LECT
- JEMBEC plates
Special bacteriologic media - Cystine-tellurite blood agar - use?
Differential medium for isolation of Corynebacterium diphtheriae
Special bacteriologic media - Cystine-tellurite blood agar - colonies on agar?
C. diphtheriae produces dark grey to black colonies.
Special bacteriologic media - Loeffler medium - use?
Enrichment medium for C. diphtheriae
Special bacteriologic media - Loeffler medium - function?
promotes development of metachromatic granules
Special bacteriologic media - Tindale agar - use?
selective differential medium for C. diphtheriae
Special bacteriologic media - Tindale agar - colonies?
Corynebacterium spp. produce gray to black colonies due to reduction of tellurite.
-C. diphtheriae colonies are surrounded by a brown halo.
Special bacteriologic media - Bismuth sulfite agar:
-selective for?
-function of bismuth sulfite & brilliant green?
-selective for Salmonella
-inhibits most others
Special bacteriologic media - Bismuth sulfite agar - S. typhi colonies?
S. typhi colonies are black, surrounded by metallic sheen.
-others are light green
-Some salmonellae may be inhibited
Special bacteriologic media - Cefsulodin-Irgasan-novobiocin (CIN) agar - use?
Selective medium for Yersinia enterocolitica, Aeromonas, & Plesiomonas shigelloides
Special bacteriologic media - Cefsulodin-Irgasan-novobiocin (CIN) agar:
-Function of crystal violet?
-Function of novobiocin?
-Function of Cefsulodin?
-Crystal violet inhibits most gram negatives.
-Novobiocin inhibits gram positive cocci
-Cefsulodin inhibits most gram positives & gram negatives
Special bacteriologic media - Cefsulodin-Irgasan-novobiocin (CIN) agar - Y. enterocolitica colonies?
Y. enterocolitica ferments mannitol, appears as red “bull’s-eye” colonies surrounded by colorless halo.
Special bacteriologic media - Alkaline peptone water (APW) - use?
Enrichment media for recovery of Vibrio from stool
Special bacteriologic media - Alkaline peptone water (APW):
-Function of alkaline pH?
-Subculture to?
-Alkaline pH suppresses commensals
-Subcultured to thiosulfate citrate bile salts sucrose (TCBS)
Special bacteriologic media - Thiosulfate Citrate Bile Salts Sucrose (TCBS) agar - use?
Selective for Vibrio
Special bacteriologic media - Thiosulfate Citrate Bile Salts Sucrose (TCBS) agar - function of high pH?
inhibits most bacteria
Special bacteriologic media - Thiosulfate Citrate Bile Salts Sucrose (TCBS) agar:
-V. cholerae colonies?
-V. parahaemolyticus and V. vulnificus colonies?
-V. cholerae ferments sucrose, produces yellow colonies
-V. parahaemolyticus & V. vulnificus DO NOT ferment sucrose; usually produce blue-green colonies
Special bacteriologic media - Bordet-Gengou agar - use?
Selective enrichment medium for isolation of Bordetella pertussis
Special bacteriologic media - Bordet-Gengou agar:
-composed of?
-function of methicillin?
-Potato-glycerol-based medium enriched with blood.
-Contaminants inhibited by methicillin.
Special bacteriologic media - Bordet-Gengou agar - Bordetella colonies?
Bordetella colonies resemble mercury droplets.
Special bacteriologic media - Bordet-Gengou agar - what is the plate also known as?
“Cough plate.”
Special bacteriologic media - Regan-Lowe agar - use?
Selective for B. pertussis
Special bacteriologic media - Regan-Lowe agar - composed of?
Charcoal agar supplemented with horse blood, cephalexin, & amphotericin B.
Special bacteriologic media - BYCE agar - use?
Enrichment medium for isolation of Legionella
Special bacteriologic media - BYCE agar:
-Function of yeast extract & L-cysteine?
-Function of charcoal?
-Yeast extract & L-cysteine enhance growth of Legionella.
-Charcoal absorbs toxic compounds.
Special bacteriologic media - V agar - use?
Selective & differential for G. vaginalis
Special bacteriologic media - V agar - incubation?
Incubate in increased CO2 for 48 hours.
Special bacteriologic media - V agar - G. vaginalis colonies?
G. vaginalis colonies are beta hemolytic.
Special bacteriologic media - CHROMagar or chromID - use?
Detect emerging antibiotic-resistant pathogens such as extended-spectrum beta-lactamase (ESBL) - producing E.coli, methicillin-resistant Staphylococcus aureus (MRSA), and carbapenemase-producing Enterobacteriaceae
Special bacteriologic media - CHROMagar or chromID - function of chromogens?
Chromogens are released if specific enzymes produced by target organism are present.
Aerotolerance test - Aerobe:
-blood agar incubated aerobically?
-blood agar incubated anaerobically?
-CHOC incubated in CO2 incubator?
-Growth
-No growth
-Growth
Aerotolerance test - Capnophilic aerobe:
-blood agar incubated aerobically?
-blood agar incubated anaerobically?
-CHOC incubated in CO2 incubator?
-No growth
-No growth
-Growth
Aerotolerance test - Facultative anaerobe:
-blood agar incubated aerobically?
-blood agar incubated anaerobically?
-CHOC incubated in CO2 incubator?
-Growth
-Growth
-Growth
Aerotolerance test - Obligate anaerobe:
-blood agar incubated aerobically?
-blood agar incubated anaerobically?
-CHOC incubated in CO2 incubator?
-No growth
-Growth
-No growth
Aerotolerance test - Aerotolerant anaerobe:
-blood agar incubated aerobically?
-blood agar incubated anaerobically?
-CHOC incubated in CO2 incubator?
-No growth
-Growth
-Growth
List the organisms requiring incubation in increased CO2.
- Campylobacter (10-15% CO2)
- Haemophilus (5-10% CO2)
- Helicobacter (5-10% CO2)
- Moraxella catarrhalis (5% CO2)
- Mycobacterium (5-10% CO2)
- Pathogenic Neisseria (5-10% CO2)
Hemolytic reactions on sheep blood agar - Alpha hemolysis:
-description
-explanation
-examples
-green zone around colony; may be narrow or wide
-partial lysis of RBCs
-Streptococcus pneumoniae & viridans streptococci
Hemolytic reactions on sheep blood agar - Beta hemolysis:
-description
-explanation
-examples
-clear zone around colony; may be narrow or wide
-complete lysis of RBCs
-Group A strep (GAS), group B strep (GBS), Listeria monocytogenes
Hemolytic reactions on sheep blood agar - Gamma (non-hemolytic):
-description
-explanation
-examples
-no zone of hemolysis
-no lysis of RBCs
-Enterococcus faecalis
Staphylococcaceae - Staphylococcus spp. - gram stain
gram positive cocci - usually in clusters
Staphylococcaceae - Staphylococcus spp. - colonies of SBA
1-3 mm
round
smooth
convex
glistening
opaque
entire edge
butyrous (butter-like)
Staphylococcaceae - Staphylococcus spp. - key characteristics
-catalase positive
-fermentative
-modified oxidase (microdase) negative
-resistant to bacitracin
-Matrix-assisted laser desorption ionization-time of flight (MALD-TOF) mass spectrometry routinely used for ID of isolates
Staphylococcaceae - Staphylococcus spp. - normal flora of?
skin
mouth
pharynx
vagina
urethra
GI tract
Staphylococcaceae - Staphylococcus spp. - aerotolerance
facultative anaerobe
Staphylococcaceae - Staphylococcus spp. - growth on media
Grows on most non-selective media
Staphylococcaceae - Staphylococcus spp. - salt tolerance
salt tolerant
Staphylococcaceae - S. aureus - pathogenicity
Causes suppurative cutaneous infections, toxic shock syndrome, food poisoning
Staphylococcaceae - S. aureus - gram stain
gram positive cocci - usually in clusters
Staphylococcaceae - S. aureus - colonies on SBA
-most are beta hemolytic (small zone)
-may be golden
Staphylococcaceae - S. aureus - key characteristics
-coagulase positive
-ferments mannitol (yellow color with mannitol salt agar (MSA))
-usually DNase positive
Staphylococcaceae - S. aureus - penicillin
85-90% resistant to penicillin
Staphylococcaceae - S. aureus - MRSA
-strains are common
-methicillin resistance is mediated by the mecA gene or its homologs and is the most important resistance mechanism
Which staphylococcaceae species is the second leading cause of health-care-associated infections, spread by direct contact with personnel and contaminated objects?
A. S. saprophyticus
B. S. aureus
C. S. epidermidis
D. Micrococcus
B. S. aureus
Staphylococcaceae - S. epidermidis - pathogenicity
-opportunistic pathogen
-causes nosocomial infections due to contamination of inserted or implanted medical devices
Staphylococcaceae - S. epidermidis - gram stain
gram positive cocci - usually in clusters
Staphylococcaceae - S. epidermidis - colonies on SBA
-white to slightly yellow
-usually non-hemolytic
Staphylococcaceae - S. epidermidis - key characteristics
-coagulase negative
-grows on MSA but does NOT ferment mannitol
-sensitive to novobiocin
Which staphylococcaceae is frequently recovered from blood cultures but not usually clinically significant in adults?
A. S. aureus
B. S. epidermidis
C. S. saprophyticus
D. Micrococcus
B. S. epidermidis
Staphylococcaceae - S. saprophyticus - pathogenicity
-UTI in young sexually active females
-Urethritis & prostatitis in males
Staphylococcaceae - S. saprophyticus - gram stain
gram positive cocci - usually in clusters
Staphylococcaceae - S. saprophyticus - colonies on SBA
-white to slightly yellow
-non-hemolytic
Staphylococcaceae - S. saprophyticus - key characteristics
-coagulase negative
-resistant to novobiocin
-may ferment mannitol
Which of the following characteristics can help differentiate between S. epidermidis and S. saprophyticus?
A. coagulase
B. mannitol fermentation
C. novobiocin sensitivity
D. none of the above
C. novobiocin sensitivity
-S. epidermidis is sensitive to novobiocin
-S. saprophyticus is resistant to novobiocin
-*S. saprophyticus may or may not ferment mannitol; S. epidermidis does NOT ferment mannitol.
-Both are coagulase negative
Staphylococcaceae - S. saprophyticus - when is novobiocin sensitivity performed?
Only when coagulase-negative staphylococci (CNS) are isolated from the urine of a female.
Staphylococcaceae - Micrococcus - pathogenicity
-usually non-pathogenic
-found in environment and on skin & mucous membranes
Staphylococcaceae - Micrococcus - gram stain
Large gram positive cocci in pairs or tetrads (predominant arrangement)
Staphylococcaceae - Micrococcus - colonies on SBA
-often pigmented (bright yellow, orange, pink, tan)
-high-domed colonies
Staphylococcaceae - Micrococcus - key characteristics
-catalase positive
-coagulase negative
-oxidative
-Modified oxidase (microdase) positive
-most urease positive
-resistant to furazolidone & lysostaphin (in contrast to most staphylococci)
How would you differentiate Micrococcus from staphylococci?
A. coagulase
B. modified oxidase (microdase)
C. All of the above
D. None of the above
B. modified oxidase (microdase)
Staphylococcaceae - Micrococcus - aerotolerance
usually grow aerobically
Staphylococcaceae - Micrococcus - species in this genus
Micrococcus luteus
Micrococcus lylae
List the tests used in the identification of staphylococci.
- Catalase
- Coagulase
- Slide agglutination tests for S. aureus
- MSA
- Rapid latex and hemagglutinin assays
- MALDI-TOF
Tests for identification of staphylococci - Catalase - principle
Enzyme catalase converts 3% hydrogen peroxide (H2O2) to oxygen & water. Immediate bubbling.
Tests for identification of staphylococci - Catalase - key reactions
Staphylococcus & micrococcus are catalase positive
Tests for identification of staphylococci - Catalase - bubbling
Bubbles after 20-30 seconds are NOT considered a positive reaction.
Catalase from RBCs in blood agar may produce weak bubbles.
Tests for identification of staphylococci - Coagulase - principle
Enzyme coagulase causes coagulation (tube test) or agglutination (slide test) in plasma.
Tests for identification of staphylococci - Coagulase - key reactions
S. aureus is coagulase positive.
Tests for identification of staphylococci - Coagulase - slide test vs. tube test
Slide test is a screening test - detects bound coagulase (clumping factor).
-If negative, a tube test should be performed - detects free coagulase.
Largely replaced by latex agglutination tests
Tests for identification of staphylococci - Slide agglutination tests for S. aureus - principle
Agglutination of latex beads coated with fibrinogen & antibodies to protein A (protein in cell wall of S. aureus).
Tests for identification of staphylococci - Slide agglutination tests for S. aureus - key reactions
S. aureus positive
Tests for identification of staphylococci - Slide agglutination tests for S. aureus - reporting by labs
Most labs report positive organisms as S. aureus.
Tests for identification of staphylococci - Mannitol Salt agar (MSA) - principle
Fermentation of mannitol results in color change from pink to yellow.
Tests for identification of staphylococci - Mannitol Salt agar (MSA) - key reactions
S. aureus positive
Tests for identification of staphylococci - Mannitol Salt agar (MSA) - what component inhibits most organisms other than staph?
7.5% salt
Tests for identification of staphylococci - Mannitol Salt agar (MSA) - do all staph grow on MSA?
They all can grow on MSA.
Tests for identification of staphylococci - Mannitol Salt agar (MSA) - why is it rarely used for ID of S. aureus today?
because other species ferment mannitol
Tests for identification of staphylococci - Rapid latex and hemagglutination assays - principle
Latex agglutination slide-card tests to detect coagulase and/or protein A associated with S. aureus & MRSA
Tests for identification of staphylococci - Rapid latex and hemagglutination assays - key reactions
S. aureus positive
Tests for identification of staphylococci - Rapid latex and hemagglutination assays - sensitivity & specificity
High sensitivity but relatively low specificity.
-May get false-positive with coagulase-negative staph.
Tests for identification of staphylococci - MALDI-TOF - principle
A type of mass spectrometry good for analyzing biomolecules like peptides, lipids, and saccharides.
Tests for identification of staphylococci - MALDI-TOF - key reactions
Rapid and specific ID of staphylococci and other catalase-positive cocci.
Tests for identification of staphylococci - MALDI-TOF - % of identification
ID of staphylococci at species levels is >97% but lower for coagulase-negative staph.
Streptococci - Streptococcus spp. - gram stain
Oval gram positive cocci in chains & pairs
Streptococci - Streptococcus spp. - colonies on SBA
-<1mm
-white to gray
-translucent or semi-opaque
-variable hemolysis
Streptococci - Streptococcus spp. - key characteristics
Catalase negative
-differentiates for staph
Streptococci - Streptococcus spp. - aerotolerance
Facultative anaerobes
Streptococci - Streptococcus spp. - growth media
-require enriched media
-chaining best in broth cultures
Streptococci - Group A Strep (GAS) - pathogenicity
-causes 90% of strep infections
-Strep sore throat
-rheumatic fever
-glomerulonephritis
-scarlet fever
-erysipelas
-puerperal sepsis
-impetigo
Streptococci - Group A Strep (GAS) - gram stain
oval gram positive cocci in chains
Streptococci - Group A Strep (GAS) - colonies on SBA
-pinpoint
-grayish white
-translucent
-usually beta hemolytic (wide zone)
Streptococci - Group A Strep (GAS) - key characteristics
-sensitive to bacitracin
-pyrrolidonyl aminopeptidase (PYR) positive
Streptococci - Group A Strep (GAS) - most common GAS?
S. pyogenes
Streptococci - Group A Strep (GAS) - hemolysis due to?
O2-stable streptolysin S & O2-labile streptolysin O.
Streptococci - Group A Strep (GAS) - definitive diagnosis
Immunoassay for Lancefield group A or MALDI-TOF
Streptococci - Group B Strep (GBS), S. agalactiae - pathogenicity
-normal flora of female genital tract
-most common cause of neonatal septicemia & meningitis
Streptococci - Group B Strep (GBS), S. agalactiae - gram stain
oval gram positive cocci in chains
Streptococci - Group B Strep (GBS), S. agalactiae - colonies on SBA
-slightly larger than GAS
-gray-white
-narrow zone of diffuse beta hemolysis
-may be non-hemolytic
Streptococci - Group B Strep (GBS), S. agalactiae - key characteristics
-resistant to bacitracin
-sodium hippurate positive
-CAMP positive
Streptococci - Group B Strep (GBS), S. agalactiae - pregnant women
Vaginal & rectal swabs collected from pregnant women at 35-37 weeks gestation
Streptococci - Group B Strep (GBS), S. agalactiae - growth media
Inoculated in selective broth, e.g., LIM, GBS broth
Streptococci - Group B Strep (GBS), S. agalactiae - test recommended for ID after culture enrichement?
Nucleic acid amplification tests (NAATs)
Streptococci - Streptococcus pneumoniae - pathogenicity
-colonizes upper respiratory tract of some children
-most common cause of community acquired pneumonia
-major cause of otitis media & meningitis in adults
-infects sinuses and eyes
Streptococci - Streptococcus pneumoniae - gram stain
-football-shaped (lancet-shaped) gram positive cocci
-usually in pairs
-may be single or in short chains
-frequently encapsulated
Streptococci - Streptococcus pneumoniae - colonies on SBA
-round
-translucent
-glistening
-dome-shaped when young
-central depression with age (umbilicate) due to autolysis
-Alpha hemolytic
-Encapsulated strains are mucoid
Streptococci - Streptococcus pneumoniae - key characteristics
-bile solubility positive
-sensitive to optochin
Streptococci - Streptococcus pneumoniae - Lancefield group
None
Streptococci - Streptococcus pneumoniae - tests used for ID
MALDI-TOF can be used
Streptococci - Group C/G streptococci - S. dysgalactiae subsp equisimilis - pathogenicity
-normal flora of upper respiratory tract but can cause pharyngitis (throat infection)
Streptococci - Group C/G streptococci - S. dysgalactiae subsp equisimilis - gram stain
oval gram positive cocci in clusters & pairs
Streptococci - Group C/G streptococci - S. dysgalactiae subsp equisimilis - colonies on SBA
beta-hemolytic
Streptococci - Group C/G streptococci - S. dysgalactiae subsp equisimilis - key characteristics
-resistant to bacitracin
-PYR positive
Streptococci - Group C/G streptococci - S. dysgalactiae subsp equisimilis - indistinguishable from?
Indistinguishable from pharyngitis caused by S. pyogenes.
Streptococci - Viridans streptococci (S. mitis group, S. mutans group, S. salivarius group, & S. bovis group) - pathogenicity
-normal in oral, respiratory, & GI mucosa
-opportunistic pathogens
-frequent cause of subacute bacterial endocarditis, bacteremia, sepsis, and abscesses.
Streptococci - Viridans streptococci (S. mitis group, S. mutans group, S. salivarius group, & S. bovis group) - gram stain
gram positive cocci in chains
Streptococci - Viridans streptococci (S. mitis group, S. anginosus group, S. mutans group, S. salivarius group, & S. bovis group) - colonies on SBA
-alpha hemolytic (S. mitis group)
-non-hemolytic (S. salivarius and S. bovis group)
-beta-hemolytic (S. anginosus group)
Streptococci - Viridans streptococci (S. mitis group, S. mutans group, S. salivarius group, & S. bovis group) - key characteristics
-S. mutans group - ferments sorbitol
-Bile solubility negative
-S. bovis is bile esculin positive
Enterococcus - E. faecium & E. faecalis - pathogenicity
-normal in mouth, GI tract, & male genital tract
-causes nosocomial UTI, wound infections, endocarditis, & bacteremia
Enterococcus - E. faecium & E. faecalis - gram stain
oval gram positive cocci in pairs, chains
Enterococcus - E. faecium & E. faecalis - colonies on SBA
E. faecium - alpha or non-hemolytic
-Some strains of E. faecalis may be beta-hemolytic
Enterococcus - E. faecium & E. faecalis - key characteristics
-catalase negative
-hydrolyzes esculin
-grows in 6.5% NaCl broth
-PYR positive
Enterococcus - E. faecium & E. faecalis - what antibiotic is E. faecalis resistant to?
Vancomycin
-VRE are a significant public health concern.
-VRE fecal surveillance culture is often done for early detection
Enterococcus - E. faecium & E. faecalis - media used for ID of VRE
chromogenic agar
Lists the test used for the identification of beta-hemolytic streptococci.
- Bacitracin disk
- MALDI-TOF
- PYR test
- CAMP test
- Hippurate hydrolysis
- Slide agglutination tests
Tests for identification of beta-hemolytic streptococci - Bacitracin disk - principle
Zone of inhibition after overnight incubation = susceptibility to bacitracin
Tests for identification of beta-hemolytic streptococci - Bacitracin disk - key reactions
-Group A strep susceptible
-Group B strep resistant
Tests for identification of beta-hemolytic streptococci - Bacitracin disk:
-also known as?
-media performed on?
-no longer recommended - why?
-replaced by?
-also known as A disk
-performed on SBA
-no longer recommended because some groups C & G are susceptible
-replaced by PYR & serogrouping by latex agglutination
Tests for identification of beta-hemolytic streptococci - MALDI-TOF - principle
A type of mass spectrometry good for identifying biomolecules like peptides, lipids, and saccharides.
Tests for identification of beta-hemolytic streptococci - MALDI-TOF - key reactions
Reliable for S. pyogenes, S. agalactiae, & S. pneumoniae
Tests for identification of beta-hemolytic streptococci - PYR test - principle
If PYR is hydrolyzed = red color after addition of color developer
Tests for identification of beta-hemolytic streptococci - PYR test - key reactions
group A strep are positive
Tests for identification of beta-hemolytic streptococci - PYR test - more specific than what other test for group A strep?
bacitracin disk test
True or False. Group A strep is the only beta-hemolytic strep that is PYR positive.
True
Tests for identification of beta-hemolytic streptococci - CAMP test - principle
Group B strep produces extracellular protein that enhances hemolysis of beta-hemolytic S. aureus on SBA
Tests for identification of beta-hemolytic streptococci - CAMP test - key reactions
group B strep is positive
Tests for identification of beta-hemolytic streptococci - CAMP test - classic method
-unknown is streaked perpendicular to a streak of beta-lysin producing S. aureus.
-incubated in ambient air overnight
-FALSE POSITVE in CO2
-Arrowhead hemolysis - where inoculum lines meet
-Disk containing beta-lysin can be used instead of S. aureus
Tests for identification of beta-hemolytic streptococci - CAMP test - rapid test
A drop of beta-lysin on colonies on SBA.
-only requires 20 minute incubation
List the tests used for identification of beta-hemolytic streptococci.
- Hippurate hydrolysis
- Slide agglutination tests
Tests for identification of beta-hemolytic streptococci - Hippurate hydrolysis - principle
Organisms that produce hippuricase (hippurate hydrolase) hydrolyze sodium hippurate to benzoate & glycine.
Tests for identification of beta-hemolytic streptococci - Hippurate hydrolysis - key reactions
group B strep positive
Tests for identification of beta-hemolytic streptococci - Hippurate hydrolysis - alternative to?
Alternative to CAMP.
-2 hr test available
Tests for identification of beta-hemolytic streptococci - Slide agglutination tests - principle
Latex particles coated with group-specific antibodies agglutinate in the presence of bacterial antigens.
Tests for identification of beta-hemolytic streptococci - Slide agglutination tests - key reactions
Organisms agglutinate in corresponding antisera
Tests for identification of beta-hemolytic streptococci - Slide agglutination tests - tests commercially available for rapid ID of?
groups A, B, C, D, F, G strep, & S. pneumoniae
List the tests used for identification of alpha-hemolytic streptococci.
- Optochin disk
- Bile solubility
Tests for identification of alpha-hemolytic streptococci - Optochin disk - principle
Zone of inhibition >=14 mm with 6-mm disk OR >=16 mm with 10-mm disk = susceptibility to optochin
Tests for identification of alpha-hemolytic streptococci - Optochin disk - key reactions
-S. pneumoniae susceptible
-Viridans strep resistant
Tests for identification of alpha-hemolytic streptococci - Optochin disk:
-also known as?
-contains?
-method?
-also known as P disk
-contains ethylhydrocupreine hydrochloride
-Method: Placed on lawn of inoculum on SBA. Plates incubated overnight in CO2. If zone of inhibin is <14 mm, ID organisms as S. pneumoniae only if bile soluble.
Tests for identification of alpha-hemolytic streptococci - Bile solubility - principle
Bile salts (e.g., sodium deoxycholate) causes lysis of some organisms
Tests for identification of alpha-hemolytic streptococci - Bile solubility - key reactions
S. pneumoniae positive
Tests for identification of alpha-hemolytic streptococci - Bile solubility - performed on? positive?
-can be performed in broth or on colony
-POS = clearing of broth or disappearance of colony
-results in 30 seconds or less
Antibiograms of gram-positive cocci - Methicillin-sensitive Staphylococcus aureus - susceptibility
-resistant to penicillin
-susceptible to cephalosporin & vancomycin
Antibiograms of gram-positive cocci - Methicillin-sensitive Staphylococcus aureus - routine susceptibility testing?
yes
Antibiograms of gram-positive cocci - Methicillin-resistant Staphylococcus aureus (MRSA) - susceptibility
-resistant to all beta-lactams (penicillin, ampicillin, and cephalosporin)
Antibiograms of gram-positive cocci - Methicillin-resistant Staphylococcus aureus (MRSA) - routine susceptibility testing?
yes
Antibiograms of gram-positive cocci - Group A Strep (GAS) - susceptibility
-universally susceptible to penicillin, cephalosporins, vancomycin
Antibiograms of gram-positive cocci - Group A Strep (GAS) - routine susceptibility testing?
no
Antibiograms of gram-positive cocci - Group B Strep (GBS) - susceptibility
Susceptible to penicillin, cephalosporins, vancomycin
Antibiograms of gram-positive cocci - Group B Strep (GBS) - routine susceptibility testing?
variable - may be done when isolated from baby
Antibiograms of gram-positive cocci - Streptococcus pneumoniae - susceptibility
-increasingly resistant to penicillin
-Susceptible to vancomycin
Antibiograms of gram-positive cocci - Streptococcus pneumoniae - routine susceptibility testing?
yes
Antibiograms of gram-positive cocci - Enterococcus - susceptibility
E. faecium
-usually resistant to penicillin & several other commonly used antibiotics
-most are susceptible to vancomycin
*E. faecium
-vancomycin resistant (VRE)
Antibiograms of gram-positive cocci - Enterococcus - routine susceptibility testing?
yes
Aerobic spore-forming gram-positive rods - Bacillus spp. - pathogenicity
usually contaminants
Aerobic spore-forming gram-positive rods - Bacillus spp. - gram stain
-large with square ends
-may be in chains
-oval, central to subterminal spores that aren’t swollen
-looks like bamboo
-spores may not be seen in direct smear
Aerobic spore-forming gram-positive rods - Bacillus spp. - culture
-large spreading beta-hemolytic colonies with irregular edges (MEDUSA HEAD)
-whitish gray
-may be pigmented
Aerobic spore-forming gram-positive rods - Bacillus spp. - key characteristics
-catalase positive
-most are motile
Aerobic spore-forming gram-positive rods - Bacillus spp. - what must be ruled out? how?
Must rule out B. anthracis
-often done via PCR
Aerobic spore-forming gram-positive rods - Bacillus anthracis - pathogenicity
-one of the most highly pathogenic microorganisms
-causes anthrax
-contracted from contaminated hides, wool, meat
Aerobic spore-forming gram-positive rods - Bacillus anthracis - gram stain
-large with square ends
-may be in chains
-oval, central to subterminal spores that aren’t swollen
-looks like bamboo
-spores may not be seen in direct smear
Aerobic spore-forming gram-positive rods - Bacillus anthracis - culture
-large
-adherent
-NON-HEMOLYTIC
-flat to slightly convex
-irregular border
-GROUND GLASS appearance
-comma shaped projections
-stands up like BEATEN EGG WHITE when touched with loop
Aerobic spore-forming gram-positive rods - Bacillus anthracis - key characteristics
-NON-HEMOLYTIC (beta-hydrolysis rules out)
-catalase positive
-NON-MOTILE
-capsules are seen in CSF & blood smears
Aerobic spore-forming gram-positive rods - Bacillus anthracis - antibotic susceptibility
Most strains are susceptible to penicillin.
Aerobic spore-forming gram-positive rods - Bacillus cereus - pathogenicity
-often environmental contaminant
-can cause focal & systemic infections, food poisoning
Aerobic spore-forming gram-positive rods - Bacillus cereus - gram stain
-large with square ends
-may be in chains
-oval, central to subterminal spores that aren’t swollen
-looks like bamboo
-spores may not be seen in direct smear
Aerobic spore-forming gram-positive rods - Bacillus cereus - culture
-large
-adherent
-HEMOLYTIC
-flat to slightly convex
-irregular border
-GROUND GLASS appearance
-comma shaped projections
-stands up like BEATEN EGG WHITE when touched with loop
Aerobic spore-forming gram-positive rods - Bacillus cereus - key characteristics
-hemolytic
-motile
Aerobic NON-spore-forming gram-positive rods - Corynebacterium spp. - pathogenicity
-normal on skin & mucous membranes
-opportunistic pathogen
Aerobic NON-spore-forming gram-positive rods - Corynebacterium spp. - gram stain
-irregular
-slightly curved
-non-paralleled sides
-CLUB-SHAPED ends
-if taken from fluid, they can arrange in PALLISADES or clusters with angular V-shaped forms
Aerobic NON-spore-forming gram-positive rods - Corynebacterium spp. - culture
-facultative anaerobes
-grow on most media
Aerobic NON-spore-forming gram-positive rods - Corynebacterium spp. - also known as?
DIPTHEROIDS - because they resemble C. diphtheriae
Aerobic NON-spore-forming gram-positive rods - Corynebacterium spp. - key characteristics
-catalase positive
-non-motile
Aerobic NON-spore-forming gram-positive rods - Corynebacterium diphtheriae - pathogenicity
Diphtheria
Aerobic NON-spore-forming gram-positive rods - Corynebacterium diphtheriae - gram stain
-irregular
-slightly curved
-non-paralleled sides
-CLUB-SHAPED ends
-if taken from fluid, they can arrange in PALLISADES or clusters with angular V-shaped forms
Aerobic NON-spore-forming gram-positive rods - Corynebacterium diphtheriae- culture
-Tindale agar: gray-black colonies with brown halos
-Cystine tellurite agar: black colonies
Aerobic NON-spore-forming gram-positive rods - Corynebacterium diphtheriae - key characteristics
-catalase positive
-non-motile
-toxin producing
Aerobic NON-spore-forming gram-positive rods - Corynebacterium diphtheriae - requirements for ID
-demonstration of toxin production
PCR or MALDI-TOFF are used for ID but must be followed up with ELEK immunoprecipitation test to confrim toxin production
Aerobic NON-spore-forming gram-positive rods - Corynebacterium diphtheriae - Corynebacterium ulcerans
-closely releated to C. diphtheriae
-also contains the TOX gene and can cause diphtheriae
Aerobic NON-spore-forming gram-positive rods - Corynebacterium jeikeium - pathogenicity
hospital-acquired pathogen
Aerobic NON-spore-forming gram-positive rods - Corynebacterium jeikeium - gram stain
-irregular
-slightly curved
-non-paralleled sides
-CLUB-SHAPED ends
-if taken from fluid, they can arrange in PALLISADES or clusters with angular V-shaped forms
Aerobic NON-spore-forming gram-positive rods - Corynebacterium jeikeium - culture
Same as other commensal corynebacteria
Aerobic NON-spore-forming gram-positive rods - Corynebacterium jeikeium - key characteristics
-catalase positive
-rapid sucrose urea (RSU) negative
Aerobic NON-spore-forming gram-positive rods - Corynebacterium jeikeium - antibiotic susceptibility
multidrug resistant (MDR)
Which diphtheroid is the most commonly isolated?
A. C. diphtheriae
B. C. ulcerans
C. C. jeikeium
D. None of the above
C. C. jeikeium
Aerobic NON-spore-forming gram-positive rods - Listeria monocytogenes - pathogenicity
-able to cross the placenta and can infect the fetus causing preterm labor and other complications resulting in fetal loss up to 24%
-meningitis & septicemia in newborns & immunocompromised
-food poisoning with mortality ranges up to 50%
Aerobic NON-spore-forming gram-positive rods - Listeria monocytogenes - gram stain
-parallel sides
-rounded ends
-coccobacillary
-singles or short chain arrangement
Aerobic NON-spore-forming gram-positive rods - Listeria monocytogenes - culture
-tiny colonies with narrow zone of indistinct beta hemolysis
-translucent, gray
Aerobic NON-spore-forming gram-positive rods - Listeria monocytogenes - key characteristics
-catalase positive
-hippurate hydrolysis positive
-esculin positive
-CAMP positive (hemolysis looks like SHOVEL, not arrowhead)
-TUMBLING motility on wet mount
-UMBRELLA growth in motility agar at room temperature but not at 35*C.
Aerobic NON-spore-forming gram-positive rods - Listeria monocytogenes:
-growth temp?
-enrichment?
-differentiation from group B strep?
-differentiation from diphtheroids?
-MALDI-TOF?
-grows from 0.5C-45C
-cold enrichment may be used
-catalase differentiates from group B strep
-motility (tumbling) differentiates from diphtheroids (non-motile)
-MALDI-TOF can be used for ID
Aerobic NON-spore-forming gram-positive rods - Nocardia - pathogenicity
-immunocompetent: skin infection
-immunocompromised: invasive pulmonary & disseminated infections
Aerobic NON-spore-forming gram-positive rods - Nocardia - gram stain
-aerobic actinomycetes
-fine branching filaments with fragmentation
-often beaded
Aerobic NON-spore-forming gram-positive rods - Nocardia - culture
-slow growing
-SBA:
–wrinkled
–dry
–crumbly
–chalky white to orange-tan
–beta hemolytic
Aerobic NON-spore-forming gram-positive rods - Nocardia - key characteristics
-catalase positive
-partially ACID FAST
-SULFUR granules
Aerobic NON-spore-forming gram-positive rods - Nocardia - frequently isolated species
N. brasiliensis
N. pseudobrasiliensis
N. abscessus
Aerobic NON-spore-forming gram-positive rods - Nocardia - reporting
Nocardia isolates may be identified and reported at “complex” or “group” level.
Neisseria & Moraxella - Neisseria spp. - gram stain
-gram negative DIPLOCOCCI (GNDC) OR single COFFEE-BEAN shaped
Neisseria & Moraxella - Neisseria spp. - culture
-aerobic OR facultative
-pathogens are CAPNOPHILIC
Neisseria & Moraxella - Neisseria spp. - key characteristics
-catalase positive
-oxidase positive
Neisseria & Moraxella - Neisseria gonorrhoeae - pathogenicity
-gonorrhea
-salpingitis
-ophthalmia of newborn
Neisseria & Moraxella - Neisseria gonorrhoeae - gram stain
-intracellular & extracellular GNDC
–diagnostic in urethral discharge from symptomatic males
–culture confirmation required for females
Neisseria & Moraxella - Neisseria gonorrhoeae - culture
-requires increased CO2
-usually does NOT grow on SBA
-grows on CHOC & Neisseria-selective media
-colonies are small, grayish white or tan
-may look like mixed culture
Neisseria & Moraxella - Neisseria gonorrhoeae - key characteristics
-oxidase positive
-carbohydrate utilization: GLUCOSE only
Neisseria & Moraxella - Neisseria gonorrhoeae:
-susceptible to what conditions?
-culture used for?
-definitive ID?
-NAATs?
-susceptible to drying & cold
-culture used for presumptive ID
-definitive ID: monoclonal antibodies
-NAATs can be used on male urine specimens with high sensitivity but should NOT be used with oropharyngeal, rectal, ocular, or pediatric patients
Neisseria & Moraxella - Neisseria meningitidis - pathogenicity
-normal flora in upper respiratory tract
-always pathogenic when recovered from usually sterile body fluids such as blood or CSF
-common cause of meningitis in young adults
Neisseria & Moraxella - Neisseria meningitidis - gram stain
-intracellular & extracellular GNDC
-a gram stain of CSF is required for all cases of suspected bacterial meningitis sent to the lab
Neisseria & Moraxella - Neisseria meningitidis - culture
-grows on SBA, CHOC, & Neisseria-selective media
-colonies are grey, convex, glistening, & occasionally mucoid
Neisseria & Moraxella - Neisseria meningitidis - key characteristics
-carbohydrate utilization: GLUCOSE & MALTOSE
-O-nitrophenyl-beta-D-galactopyranoside (ONPG) NEGATIVE
Neisseria & Moraxella - Commensal Neisseria spp. - pathogenicity
-normal in upper respiratory tract
-rarely cause disease
Neisseria & Moraxella - Commensal Neisseria spp. - gram stain
GNDC
Neisseria & Moraxella - Commensal Neisseria spp. - culture
-grow on SBA & CHOC at RT
-grow on nutrient agar at 35*C
-some grow on Neisseria-selective media
-DO NOT require increased CO2
-may be pigmented
Neisseria & Moraxella - Commensal Neisseria spp. - key characteristics
varies with species
Neisseria & Moraxella - Commensal Neisseria spp.:
-speciation?
-must differentiate from?
-N. lactamica?
-not speciated if from respiratory tract
-must differentiate from pathogenic Neisseria when isolated on selective media or from normally sterile body site
-N. lactamica is easily confused with N. meningitidis but N. lactamica acidifies lactose in addition to glucose
Neisseria & Moraxella - Moraxella catarrhalis - pathogenicity
-normal in upper respiratory tract
-causes respiratory infections in young, old, & immunocompromised
-causes otitis media & sinusitis in children
Neisseria & Moraxella - Moraxella catarrhalis - gram stain
GNDC
Neisseria & Moraxella - Moraxella catarrhalis - culture
-grows on SBA & CHOC
-some may grow at RT &/or on Neisseria-selective media
-“HOCKEY PUCK colonies” - colonies can be pushed over agar surface with a loop
Neisseria & Moraxella - Moraxella catarrhalis - key characteristics
-catalase positive
-oxidase positive
-carbohydrate utilization: NEG for all sugars
-ONPG negative
-DNase positive
-butyrate esterase positive
Neisseria & Moraxella - Moraxella catarrhalis - differentiation from Neisseria spp.
DNase & butyrate esterase differentiate from Neisseria spp.
Characteristics of Enterobacterales - gram stain
Non-spore-forming GNRs
Characteristics of Enterobacterales - gram stain
Non-spore-forming GNRs
Characteristics of Enterobacterales - growth characteristics
facultative anaerobes
Characteristics of Enterobacterales - colonies on SBA
most are large, dull, gray, non-hemolytic
Characteristics of Enterobacterales - colonies on MAC
-lactose fermenters = pink
-non-lactose fermenters = colorless
Characteristics of Enterobacterales - Biochemicals
-ferment GLUCOSE
-oxidase negative
-most reduce nitrates to nitrites
-most are catalase positive
List the biochemical tests used for identification of Enterobacterales. (14)
- Oxidase
- nitrate reduction
- carbohydrate fermentation
- ONPG
- H2S production
- Triple sugar iron (TSI) agar
- Indole
- Methyl red (MR)
- Voges-Proskauer (VP)
- Citrate
- Urease
- Phenylalanine deaminase (PD)
- Decarboxylase reactions
- motility
Biochemical tests for identification of Enterobacterales - oxidase - principle
tetramethyl-para-phenylenediamine dihydrochloride reacts with cytochrome C to produce a blue or purple color
Biochemical tests for identification of Enterobacterales - oxidase - interpretation
Positive = blue or purple color
Biochemical tests for identification of Enterobacterales - oxidase:
-test used to differentiate?
-false pos?
-good test to differentiate Enterobacterales from non-fermenters
-false positive from iron-containing wire - use platinum or wooden stick
Biochemical tests for identification of Enterobacterales - nitrate reduction - principle
If organism reduces nitrates to nitrites, a RED color develops when sulfanic aicd & N,N-dimethyl-L-naphthylamine added
Biochemical tests for identification of Enterobacterales - nitrate reduction - interpretation
Positive = red, OR no color after addition of zinc dust
Biochemical tests for identification of Enterobacterales - nitrate reduction - zinc dust
If no color develops (red = pos), zinc dust is added. It reduces nitrates.
-RED color AFTER zinc dust = presence of nitrates (NEG REACTION)
-NO COLOR after zinc dust means nitrates reduces to N2 or NO2 (POS REACTION)
Biochemical tests for identification of Enterobacterales - carbohydrate fermentation - principle
when carbohydrate is fermented, acidic end products cause color change in pH indicator
Biochemical tests for identification of Enterobacterales - carbohydrate fermentation - interpretation
with phenol red indicator = change from red to yellow
Biochemical tests for identification of Enterobacterales - carbohydrate fermentation:
-frequently tested carbohydrates?
-all Enterobacterales ferment?
-frequently tested carbohydrates are glucose, lactose, sucrose, mannose, sorbitol, mannitol, xylose, adonitol, cellobiose, dulcitol, trehalose
-All Enterobacterales ferment GLUCOSE
Biochemical tests for identification of Enterobacterales - ONPG - principle
ONPG is changed to orthonitrophenol by beta-galactosidase
Biochemical tests for identification of Enterobacterales - ONPG - interpretation
positive = yellow
Biochemical tests for identification of Enterobacterales - ONPG:
-test for?
-differentiation of?
-test for slow lactose fermentation
-helpful in differentiating Citrobacter (positive) from most Salmonella (negative).
Biochemical tests for identification of Enterobacterales - H2S production - principle
-organisms that possess H2S-producing enzymes produce colorless H2S gas from sulfur containing compounds
-H2S reacts with iron salt in medium to form black ferrous sulfide
Biochemical tests for identification of Enterobacterales - H2S production - interpretation
black precipitate
Biochemical tests for identification of Enterobacterales - H2S production:
-sulfur-containing compounds?
-differentiates?
-sulfur-containing compounds = sodium thiosulfate, cystine, methionine
-good test to differentiate Salmonella (H2S positive) from Shigella (H2S negative).
Biochemical tests for identification of Enterobacterales - Triple sugar iron (TSI) agar - principle
sugar fermentation produces acid = changes color of pH indicator
Biochemical tests for identification of Enterobacterales - Triple sugar iron (TSI) agar - interpretation
Yellow = acid (A)
Pink = alkaline (K)
Pink butt = glucose NOT fermented
Yellow butt = glucose fermented
Pink slant = lactose/sucrose NOT fermented
Yellow slant = lactose and/or sucrose fermented
Black precipitate = H2S produced
Bubbles = gas production
Biochemical tests for identification of Enterobacterales - Triple sugar iron (TSI) agar:
-contains?
-how to leave cap to tube?
-record as?
-Kligler iron agar (KIA)?
-contains 0.1% glucose, 1% lactose, 1% sucrose, phenol red, sodium thiosulfate, iron salt
-leave cap slightly loose
-record as slant/butt, e.g., K/A [some record NC = no change (for pink butt]
-Kligler iron agar (KIA) is same except NO sucrose
Biochemical tests for identification of Enterobacterales - Indole - principle
-tryptophanase deaminates tryptophan = indole produced
-Kovacs reagent (paradimethylaminobenzaldehyde) forms pink-colored complex with indole
Biochemical tests for identification of Enterobacterales - Indole - interpretation
positive = pink
Biochemical tests for identification of Enterobacterales - Indole - spot indole test
-commercially available
-need source of tryptophan
-use colonies from SBA or CHOC agar, not MAC
-positive = blue
-E. coli & Proteus vulgaris are positive
Biochemical tests for identification of Enterobacterales - methyl red (MR) - principle
-acid products formed when glucose is metabolized by mixed acid fermentation pathway
-color changes pH indicator
Biochemical tests for identification of Enterobacterales - methyl red (MR) - interpretation
positive = red color after addition of MR (pH indicator)
Biochemical tests for identification of Enterobacterales - methyl red (MR) - pH at which test becomes positive?
4.5
Biochemical tests for identification of Enterobacterales - Voges-Proskauer (VP) - principle
acetoin is produced from alternate pathway for glucose metabolism
Biochemical tests for identification of Enterobacterales - Voges-Proskauer (VP) - interpretation
positive = red color when alphanaphthol & KOH added
Biochemical tests for identification of Enterobacterales - Voges-Proskauer (VP) - VP vs. MR
organisms that are VP positive are usually MR negative & vice versa
Biochemical tests for identification of Enterobacterales - Citrate - principle
if organism can use citrate as sole source of carbon, pH increases, and pH indicator changes color
Biochemical tests for identification of Enterobacterales - Citrate - interpretation
positive = green to blue, or growth
Biochemical tests for identification of Enterobacterales - Citrate - false negatives
false negative if cap is NOT loose
Biochemical tests for identification of Enterobacterales - Citrate - positive bacteria
Klebsiella & Enterobacter are positive
Biochemical tests for identification of Enterobacterales - Urease - principle
-urease breaks down to urea
-ammonia released, pH increased, pH indicator changes color
Biochemical tests for identification of Enterobacterales - Urease - interpretation
positive = yellow to pink
Biochemical tests for identification of Enterobacterales - Urease - rapid urease producers
Proteus & Morganella
Biochemical tests for identification of Enterobacterales - Phenylalanine deaminase (PD) - principle
PD deaminates phenylalanine to phenylpyruvic acid, which reacts with ferric chloride to produce a green color.
Biochemical tests for identification of Enterobacterales - Phenylalanine deaminase (PD) - interpretation
positive = green color after addition of ferric chloride
Biochemical tests for identification of Enterobacterales - Phenylalanine deaminase (PD) - positive organisms
-Proteus
-Providencia
-Morganella
Biochemical tests for identification of Enterobacterales - Decarboxylase reactions - principle
if organism has enzyme to decarboxylate amino acid (e.g., ornithine, lysine, arginine), pH increases, pH indicator changes color
-Ornithine decarboxylase (ODC)
Biochemical tests for identification of Enterobacterales - Decarboxylase reactions - interpretation
positive = yellow to purple
Biochemical tests for identification of Enterobacterales - Motility - interpretation
motile organisms grow away from stab line in motility medium
Biochemical tests for identification of Enterobacterales - Motility - interpretation
positive:
-movement away from stab line OR
-hazy appearance throughout medium after overnight incubation
Biochemical tests for identification of Enterobacterales - Motility - positive organisms
most Enterobacterales are positive, EXCEPT Klebsiella & Shigella
Biochemical tests for identification of Enterobacterales - Motility - differentiates?
Differentiates:
-Klebsiella (neg) from Enterobacter (pos)
AND
-Shigella (neg) from Salmonella (pos)
Antigens of Enterobacterales - O antigen:
-alternate name
-location
-characteristics
-used for serological grouping of?
-somatic antigen
-cell wall
-lipopolysaccharide, heat stable
-used for serological grouping of Salmonella & Shigella
Antigens of Enterobacterales - H antigen:
-alternate name
-location
-characteristics
-used to serotype?
-flagellar antigen
-flagella
-proteins, heat labile
-used to serotype Salmonella
Antigens of Enterobacterales - K antigen:
-alternate name
-location
-characteristics
-role in preventing what?
-Vi antigen
-capsular antigen
-capsule
-polysaccharide, heat labile, may mask O antigen; removed by heating
-role in preventing phagocytosis = increased virulence
-Vi antigen is K antigen produced by S. typhi
Escherichia, Shigella, and Salmonella Enterobacterales - E. coli - pathogenicity
-UTI
-septicemia
-neonatal sepsis
-meningitis
-diarrhea (some)
Escherichia, Shigella, and Salmonella Enterobacterales - E. coli - key reactions - POSITIVE
-lactose
-gas
-indole
-MR
-motility
Escherichia, Shigella, and Salmonella Enterobacterales - E. coli - key reactions - NEGATIVE
-H2S
-VP
-citrate
-PD
-urease
Which of the following is the predominant aerobe in the GI tract?
A. Shigella
B. Salmonella
C. E. coli
D. None of the above
C. E. coli
Which of the following is the most common cause of UTI?
A. E. coli
B. Salmonella
C. Shigella
D. None of the above
A. E. coli
Escherichia, Shigella, and Salmonella Enterobacterales - E. coli - EMB media
green metallic sheen
Escherichia, Shigella, and Salmonella Enterobacterales - E. coli - presumptive ID
-lactose positive
-dry colony on MAC
-oxidase negative
-indole positive
Escherichia, Shigella, and Salmonella Enterobacterales - E. coli - E. coli 0157:H7
-does NOT ferment sorbitol
-colorless colonies on SMAC
Escherichia, Shigella, and Salmonella Enterobacterales - Shigella - pathogenicity
-dysentery (shigellosis)
-most communicable of bacterial diarrheas
-found primarily in crowded or substandard conditions, e.g., day-care centers, jails, prisons
Escherichia, Shigella, and Salmonella Enterobacterales - Shigella - key reactions - POSITIVE
MR
Escherichia, Shigella, and Salmonella Enterobacterales - Shigella - key reactions - NEGATIVE
-lactose
-gas
-H2S
-citrate
-PD
-urease
-motility
Escherichia, Shigella, and Salmonella Enterobacterales - Shigella - what is found in the stool of patients positive for Shigella
-blood
-mucus
-neutrophils
Escherichia, Shigella, and Salmonella Enterobacterales - Shigella - most severe species?
S. dysenteriae
Escherichia, Shigella, and Salmonella Enterobacterales - Shigella - most common species in the US?
S. sonnei
Escherichia, Shigella, and Salmonella Enterobacterales - Shigella - serogrouped by what antigens?
O antigens
Escherichia, Shigella, and Salmonella Enterobacterales - Shigella - serogroups?
A, B, C, D
Escherichia, Shigella, and Salmonella Enterobacterales - Shigella - closely related to what organism on a molecular basis?
Escherichia
Escherichia, Shigella, and Salmonella Enterobacterales - Salmonella - pathogenicity
-Typhoid (enteric) fever
-bacteremia
-enterocolitis
Escherichia, Shigella, and Salmonella Enterobacterales - Salmonella - key reactions - POSITIVE
-H2S
-MR
-motility
-lysine decarboxylase (LDC)
Escherichia, Shigella, and Salmonella Enterobacterales - Salmonella - key reactions - NEGATIVE
-lactose
-indole
-VP
-PD
-urease
-ONPG
Escherichia, Shigella, and Salmonella Enterobacterales - Salmonella - what type of meat is it found in?
poultry
Escherichia, Shigella, and Salmonella Enterobacterales - Salmonella - may be transmitted by what type of animal?
reptiles
Escherichia, Shigella, and Salmonella Enterobacterales - Salmonella - S. typhi
-Vi antigen
-only trace H2S
-citrate negative
Escherichia, Shigella, and Salmonella Enterobacterales - Salmonella - grouped by? serotyped by?
-grouped by O antigens (e.g., A, B, C)
-serotyped by H antigens (e.g., 1, 2)
Diarrheagenic Escherichia coli - Enterohemorrhagic (EHEC) - pathogenicity
*also known as Shiga toxin-producing (STEC) OR verotoxin-producing (VTEC)
-diarrhea
-hemorrhagic colitis
-hemolytic uremic syndrome (HUS)
-most common cause of renal failure in children in the US
-may be fatal, especially in young or elderly
Diarrheagenic Escherichia coli - Enterohemorrhagic (EHEC) - transmission
-undercooked meat
-raw milk
-apple cider
Diarrheagenic Escherichia coli - Enterohemorrhagic (EHEC) - disease mechanism
toxins (verotoxins or Shiga toxins)
Diarrheagenic Escherichia coli - Enterohemorrhagic (EHEC) - gram stain of stool
RBCs but usually no segmented neutrophils
Diarrheagenic Escherichia coli - Enterohemorrhagic (EHEC) - E. coli 0157:H7
-most common isolate of group
-pathogen most often isolated from bloody stools
Diarrheagenic Escherichia coli - Enterohemorrhagic (EHEC) - DNA probes
ID genes that code for toxins
Diarrheagenic Escherichia coli - Enterotoxigenic (ETEC) - pathogenicity
-traveler diarrhea
-diarrhea in infants
Diarrheagenic Escherichia coli - Enterotoxigenic (ETEC) - transmission
contaminated food or water
Diarrheagenic Escherichia coli - Enterotoxigenic (ETEC) - disease mechanism
toxins
Diarrheagenic Escherichia coli - Enterotoxigenic (ETEC) - gram stain of stool
no segmented neutrophils or RBCs
Diarrheagenic Escherichia coli - Enterotoxigenic (ETEC) - type of stool
profuse, watery stool
Diarrheagenic Escherichia coli - Enterotoxigenic (ETEC) - DNA probes
detect toxins or toxin genes
Diarrheagenic Escherichia coli - Enteroinvasive (EIEC) - pathogenicity
-bloody diarrhea
-dysentery-like
-usually in young children in areas of poor sanitation
Diarrheagenic Escherichia coli - Enteroinvasive (EIEC) - transmission
contaminated food or water
Diarrheagenic Escherichia coli - Enteroinvasive (EIEC) - disease mechanism
invasiveness
Diarrheagenic Escherichia coli - Enteroinvasive (EIEC) - gram stain of stool
-segmented neutrophils
-RBCs
-mucus
Diarrheagenic Escherichia coli - Enteropathogenic (EPEC) - pathogenicity
-diarrhea in infants
-major pathogen in infants in developing countries
Diarrheagenic Escherichia coli - Enteropathogenic (EPEC) - transmission
formula & food contaminated with fecal material
Diarrheagenic Escherichia coli - Enteropathogenic (EPEC) - disease mechanism
adherence-attachment
Diarrheagenic Escherichia coli - Enteropathogenic (EPEC) - gram stain of stool
no segmented neutrophils or RBCs
Diarrheagenic Escherichia coli - Enteropathogenic (EPEC) - type of stool
watery diarrhea with mucus
Diarrheagenic Escherichia coli - Enteroaggregative (EAEC) - pathogenicity
-diarrhea in developing countries
-chronic diarrhea in HIV-infected patients
Diarrheagenic Escherichia coli - Enteroaggregative (EAEC) - transmission
nosocomial & community acquired
Diarrheagenic Escherichia coli - Enteroaggregative (EAEC) - disease transmission
adherence-attachment
Diarrheagenic Escherichia coli - Diffusely adherent (DAEC) - pathogenicity
-diarrhea & UTI
-most common in children in developing countries
Diarrheagenic Escherichia coli - Diffusely adherent (DAEC) - transmission
little known about epidemiology
Diarrheagenic Escherichia coli - Diffusely adherent (DAEC) - disease mechanism
adherence-attachment
Klebsiella and other commonly isolated Enterobacterales - Klebsiella pneumoniae - pathogenicity
-pneumonia
-UTI
-septicemia
-Carbapenem-resistant
-significant pathogen in both community and hospital settings
Klebsiella and other commonly isolated Enterobacterales - Klebsiella pneumoniae - key reactions - POSITIVE
-lactose
-gas
-VP
-citrate
-urease (slow)
Klebsiella and other commonly isolated Enterobacterales - Klebsiella pneumoniae - key reactions - NEGATIVE
-H2S
-indole
-MR
-PD
-motility
-ODC
Klebsiella and other commonly isolated Enterobacterales - Klebsiella pneumoniae - encapsulated?
yes
Klebsiella and other commonly isolated Enterobacterales - Klebsiella pneumoniae - colonies on agar
colonies are usually mucoid
Klebsiella and other commonly isolated Enterobacterales - Klebsiella pneumoniae - K. oxytoca
similar to K. pneumoniae EXCEPT indole positive
Klebsiella and other commonly isolated Enterobacterales - Klebsiella pneumoniae - differentiation from Enterobacter
-motility
-ODC
Klebsiella and other commonly isolated Enterobacterales - Citrobacter - pathogenicity
-nosocomial infections
-UTI is most common site of infection
Klebsiella and other commonly isolated Enterobacterales - Citrobacter - key reactions - POSITIVE
-gas
-H2S
-MR
-citrate
-motility
-ONPG
Klebsiella and other commonly isolated Enterobacterales - Citrobacter - key reactions - NEGATIVE
-VP
-PD
-LDC
Klebsiella and other commonly isolated Enterobacterales - Citrobacter - lactose?
lactose variable
Klebsiella and other commonly isolated Enterobacterales - Citrobacter - differentiation from Salmonella?
-ONPG
-LDC
Klebsiella and other commonly isolated Enterobacterales - Edwardsiella tarda - pathogenicity
-opportunistic
-can cause bacteremia, wound, and GI infections
-environmental risk factors include exposure to brackish water or undercooked fish
Klebsiella and other commonly isolated Enterobacterales - Edwardsiella tarda - key reactions - POSITIVE
-gas
-H2S
-indole
-MR
-motility
Klebsiella and other commonly isolated Enterobacterales - Edwardsiella tarda - key reactions - NEGATIVE
-lactose
-VP
-citrate
-PD
-urease
Klebsiella and other commonly isolated Enterobacterales - Edwardsiella tarda - primarily what type of pathogen?
fish
Klebsiella and other commonly isolated Enterobacterales - Edwardsiella tarda - differentiation from Salmonella
positive indole
Klebsiella and other commonly isolated Enterobacterales - Klebsiella aerogenes - pathogenicity
-opportunistic & nosocomial infections
-UTI
-respiratory tract infection (RTI)
-wound infections
Klebsiella and other commonly isolated Enterobacterales - Klebsiella aerogenes - key reactions - POSITIVE
-VP
-ONPG
-ODC
-citrate
-motility
-gas
Klebsiella and other commonly isolated Enterobacterales - Klebsiella aerogenes - key reactions - NEGATIVE
-H2S
-indole
-MR
-PD
Klebsiella and other commonly isolated Enterobacterales - Klebsiella aerogenes - colonies on agar
colonies may be mucoid
Klebsiella and other commonly isolated Enterobacterales - Enterobacter cloacae - pathogenicity
-nosocomial infections from contaminated medical devices and instruments
Klebsiella and other commonly isolated Enterobacterales - Enterobacter cloacae - key reactions - POSITIVE
-ODC
-VP
-sucrose
Klebsiella and other commonly isolated Enterobacterales - Enterobacter cloacae - key reactions - NEGATIVE
-oxidase
-H2S
-indole
Klebsiella and other commonly isolated Enterobacterales - Enterobacter cloacae - antibiotic susceptibility
frequently antibiotic resistant (intrinsic and plasma-based)
Other commonly isolated Enterobacterales - Serratia marcescens - pathogenicity
-opportunistic pathogen
-UTI (indwelling catheters)
-ocular
-GI tract in children
Other commonly isolated Enterobacterales - Serratia marcescens - key reactions - POSITIVE
-VP
-citrate
-motility
Other commonly isolated Enterobacterales - Serratia marcescens - key reactions - NEGATIVE
-lactose
-H2S
-indole
-PD
-urease
Other commonly isolated Enterobacterales - Serratia marcescens - pigment produced when incubated at RT
red pigment
Other commonly isolated Enterobacterales - Proteus vulgaris & Proteus mirabilis - pathogenicity
-UTI
-wound infections
-septicemia
Other commonly isolated Enterobacterales - Proteus vulgaris & Proteus mirabilis - key reactions - POSITIVE
-H2S
-MR
-PD
-urease
-motility
Other commonly isolated Enterobacterales - Proteus vulgaris & Proteus mirabilis - key reactions - NEGATIVE
-lactose
Other commonly isolated Enterobacterales - Proteus vulgaris & Proteus mirabilis - colonies on agar
-swarming
-burned chocolate odor
Other commonly isolated Enterobacterales - Proteus vulgaris & Proteus mirabilis - indole
P. mirabilis - indole negative
P. vulgaris - indole positive
Other commonly isolated Enterobacterales - Proteus vulgaris & Proteus mirabilis - P. vulgaris on TSI
A/A - because of sucrose fermentation
Other commonly isolated Enterobacterales - Morganella morganii - pathogenicity
-mainly nosocomial infections
-UTI
-wound infections
Other commonly isolated Enterobacterales - Morganella morganii - key reactions - POSITIVE
-indole
-MR
-PD
-urease (weak)
-motility
-ODC
Other commonly isolated Enterobacterales - Morganella morganii - key reactions - NEGATIVE
-lactose
-H2S
-VP
-citrate
Other commonly isolated Enterobacterales - Providencia - pathogenicity
-UTI
-diarrhea
Other commonly isolated Enterobacterales - Providencia - key reactions - POSITIVE
-indole
-MR
-citrate
-PD
-motility
Other commonly isolated Enterobacterales - Providencia - key reactions - NEGATIVE
-lactose
-H2S
-VP
Other commonly isolated Enterobacterales - Providencia - urease
P. rettgeri is urease positive
Other commonly isolated Enterobacterales - Providencia - which species is most commonly isolated?
P. stuartii
Other commonly isolated Enterobacterales - Yersinia enterocolitica - pathogenicity
diarrhea
Other commonly isolated Enterobacterales - Yersinia enterocolitica - key reactions - POSITIVE
-MR
-urease
-ONDC
Other commonly isolated Enterobacterales - Yersinia enterocolitica - key reactions - NEGATIVE
-lactose
-H2S
-VP (variable)
-citrate
-PD
Other commonly isolated Enterobacterales - Yersinia enterocolitica - gram stain
-gram negative coccobacilli
-bipolar staining
Other commonly isolated Enterobacterales - Yersinia enterocolitica - optimal temp for growth
25-30*C
Other commonly isolated Enterobacterales - Yersinia enterocolitica - motility
motile at 25C but NOT 35C
Other commonly isolated Enterobacterales - Yersinia enterocolitica - agar
-CIN agar is selective
-incubate 48 hours
-red “BULL’S EYE” colonies surrounded by colorless halo
What species of Yersinia causes plague?
Y. pestis
Summary of key reactions for Enterobacterales - lactose negative
-Shigella
-Edwardsiella
-Salmonella
-Citrobacter (some)
-Serratia
-Proteus
-Morganella
-Providencia
-Yersinia
Summary of key reactions for Enterobacterales - H2S positive
-Edwardsiella
-Salmonella
-Citrobacter
-Proteus
Summary of key reactions for Enterobacterales - VP positive
-Klebsiella
-Enterobacter
-Serratia
Summary of key reactions for Enterobacterales - PD positive
-Proteus
-Morganella
-Providencia
-Klebsiella (slow)
Summary of key reactions for Enterobacterales - Urease positive
-Proteus
-Morganella
-Providencia rettgeri
-some species of Citrobacter
Summary of key reactions for Enterobacterales - nonmotile at 35*C
-Shigella
-Klebsiella
-Yersinia (motile at 22*C)
Appearance of Enterobacterales on selected media - Escherichia coli - TSI
A/A, gas
Appearance of Enterobacterales on selected media - Escherichia coli - MAC
flat, dry pink colony with darker pink halo
Appearance of Enterobacterales on selected media - Escherichia coli - HE
yellow
Appearance of Enterobacterales on selected media - Escherichia coli - XLD
yellow
Appearance of Enterobacterales on selected media - Shigella - TSI
K/A
Appearance of Enterobacterales on selected media - Shigella - MAC
colorless
Appearance of Enterobacterales on selected media - Shigella - HE
green
Appearance of Enterobacterales on selected media - Shigella - XLD
colorless
Appearance of Enterobacterales on selected media - Edwardsiella - TSI
K/A, gas, H2S
Appearance of Enterobacterales on selected media - Edwardsiella - MAC
colorless
Appearance of Enterobacterales on selected media - Edwardsiella - HE
colorless
Appearance of Enterobacterales on selected media - Edwardsiella - XLD
red, yellow, or colorless with or without black centers
Appearance of Enterobacterales on selected media - Citrobacter - TSI
A/A or K/A, gas, with or without H2S
Appearance of Enterobacterales on selected media - Citrobacter - MAC
-colorless at 24 hrs
-may become pink at 48 hrs
Appearance of Enterobacterales on selected media - Citrobacter - HE
colorless
Appearance of Enterobacterales on selected media - Citrobacter - XLD
red, yellow, or colorless with or without black centers
Appearance of Enterobacterales on selected media - Salmonella - TSI
K/A, gas, H2S
Appearance of Enterobacterales on selected media - Salmonella - MAC
colorless
Appearance of Enterobacterales on selected media - Salmonella - HE
green
Appearance of Enterobacterales on selected media - Salmonella - XLD
red with black center
Appearance of Enterobacterales on selected media - Klebsiella - TSI
A/A, gas
Appearance of Enterobacterales on selected media - Klebsiella - MAC
pink, mucoid
Appearance of Enterobacterales on selected media - Klebsiella - HE
yellow
Appearance of Enterobacterales on selected media - Klebsiella - XLD
yellow
Appearance of Enterobacterales on selected media - Enterobacter - TSI
A/A, gas
Appearance of Enterobacterales on selected media - Enterobacter - MAC
pink, may be mucoid
Appearance of Enterobacterales on selected media - Enterobacter - HE
yellow
Appearance of Enterobacterales on selected media - Enterobacter - XLD
yellow
Appearance of Enterobacterales on selected media - Serratia - TSI
K/A
Appearance of Enterobacterales on selected media - Serratia - MAC
-colorless at first, turning pink
-S. marcescens may have red pigment at RT
Appearance of Enterobacterales on selected media - Serratia - HE
colorless
Appearance of Enterobacterales on selected media - Serratia - XLD
yellow or colorless
Appearance of Enterobacterales on selected media - Proteus - TSI
-K/A (P. mirabilis)
-A/A (P. vulgaris)
-gas, H2S
Appearance of Enterobacterales on selected media - Proteus - MAC
colorless, may swarm
Appearance of Enterobacterales on selected media - Proteus - HE
colorless
Appearance of Enterobacterales on selected media - Proteus - XLD
yellow or colorless, with or without black centers
Appearance of Enterobacterales on selected media - Morganella - TSI
K/A, gas
Appearance of Enterobacterales on selected media - Morganella - MAC
colorless
Appearance of Enterobacterales on selected media - Morganella - HE
colorless
Appearance of Enterobacterales on selected media - Morganella - XLD
red or colorless
Appearance of Enterobacterales on selected media - Providencia - TSI
K/A
Appearance of Enterobacterales on selected media - Providencia - MAC
colorless
Appearance of Enterobacterales on selected media - Providencia - HE
colorless
Appearance of Enterobacterales on selected media - Providencia - XLD
yellow or colorless
Appearance of Enterobacterales on selected media - Yersinia - TSI
Yellow/orange
Appearance of Enterobacterales on selected media - Yersinia - MAC
colorless to peach
Appearance of Enterobacterales on selected media - Yersinia - HE
salmon
Appearance of Enterobacterales on selected media - Yersinia - XLD
yellow or colorless
Characteristics of non-fermenting gram-negative rods - aerotolerance
obligate aerobes
Characteristics of non-fermenting gram-negative rods - TSI
K/K - they do NOT ferment carbohydrates
Characteristics of non-fermenting gram-negative rods - oxidizer/non-oxidizer
may be oxidizers or non-oxidizers (asaccharolytic)
Characteristics of non-fermenting gram-negative rods - oxidation-fermentation (OF) medium
either open tube pos/closed tube neg (oxidizer) OR open tube neg/closed tube neg (non-oxidizer)
Characteristics of non-fermenting gram-negative rods - SBA & CHOC
grow in 24-48 hours
Characteristics of non-fermenting gram-negative rods - MAC
appear as non-lactose-fermenters
Characteristics of non-fermenting gram-negative rods - oxidase
-most are oxidase positive
-differentiates from Enterobacterales
Characteristics of non-fermenting gram-negative rods - antibiotic susceptibility
resistant to a variety of antibiotics
Commonly isolated non-fermenting gram-negative rods - Pseudomonas aeruginosa - pathogenicity
-usually not normal flora-important cause of nosocomial infections, e.g., burn, wound, RTI, UTI, bacteremia
-causes SWIMMER’S EAR & contact lens KERATITIS
-predominant respiratory pathogen in patients with CYSTIC FIBROSIS
Commonly isolated non-fermenting gram-negative rods - Pseudomonas aeruginosa - gram stain
-long, thin, pale-staining GNR
-slightly pointed or rounded ends
Commonly isolated non-fermenting gram-negative rods - Pseudomonas aeruginosa - culture
SBA:
-flat spreading colonies
-usually beta hemolytic
-dull gray or blue-green
-METALLIC SHEEN
Grows on MAC & EMB (lactose neg)
Commonly isolated non-fermenting gram-negative rods - Pseudomonas aeruginosa - key characteristics
-oxidase positive
-catalase positive
-motile
-grows at 42*C
-GRAPE-LIKE odor
-only non-fermenter to produce PYOCYANIN (4% don’t)
-also produces pyoverdin (fluorescent pigment)
-resistant to many antibiotics
Commonly isolated non-fermenting gram-negative rods - Acinetobacter spp. - pathogenicity
-part of normal flora of skin, pharynx in some
-opportunistic pathogen
-nosocomial infections, e.g., UTI, pneumonia, septicemia, meningitis
-2nd to P. aeruginosa in frequency
-most common = A. baumannii
Commonly isolated non-fermenting gram-negative rods - Acinetobacter spp. - gram stain
-pleomorphic gram-negative coccobacilli (GNCB) in singles, pairs, short chains
-can be confused with N. gonorrhoeae, Moraxella
-may retain crystal violet in broths & direct smears & be confused with GPC
Commonly isolated non-fermenting gram-negative rods - Acinetobacter spp. - culture
-can grow on most media, including MAC
-some produce purplish colonies (might be mistaken for lactose fermenter)
Commonly isolated non-fermenting gram-negative rods - Acinetobacter spp. - key characteristics
-oxidase negative (differentiates from N. gonorrhoeae)
-catalase positive
-non-motile
-resistant to many antibiotics
Commonly isolated non-fermenting gram-negative rods - Stenotrophomonas maltophilia - pathogenicity
-NOT part of normal flora
-common cause of wound infections from agricultural machinery
-colonizes immunocompromised patients
-common in hospital
-nosocomial infections, e.g., pneumonia
Commonly isolated non-fermenting gram-negative rods - Stenotrophomonas maltophilia - gram stain
straight or slightly curved slender GNR in singles or pairs
Commonly isolated non-fermenting gram-negative rods - Stenotrophomonas maltophilia - culture
SBA:
-large, non-hemolytic
-may be light yellow
-agar may have lavender-green discoloration in areas of heavy growth
Grows on MAC
Commonly isolated non-fermenting gram-negative rods - Stenotrophomonas maltophilia - key characteristics
-most often oxidase negative
-catalase positive
-motile
-rapid oxidation of maltose
-weaker oxidation of glucose
-AMMONIA odor
-resistant to many antibiotics
-disk diffusion can give false results
-broth dilution recommended
Campylobacter & Helicobacter - Campylobacter jenuni - pathogenicity
-most common cause of bacterial diarrhea
-sources of infection: chickens, raw milk, pets
Campylobacter & Helicobacter - Campylobacter jenuni - gram stain
-curved, slender, gram negative rods
-“GULL WING-shaped”
-loose spirals
-S shaped
-stain faintly
Campylobacter & Helicobacter - Campylobacter jenuni - culture
-microaerophilic & capnophilic
-grow on CAMPY-BAP at 42C in increased CO2 (can grow at 37C; normal enteric flora inhibited by 42*C incubation)
-slow growing - hold plate 3 days
-NAATs can be used for faster ID
Campylobacter & Helicobacter - Campylobacter jenuni - key characteristics
-DARTING CORKSCREW motility
-oxidase positive
-catalase positive
-hippurate hydrolysis positive
Campylobacter & Helicobacter - Campylobacter coli - pathogenicity
-similar to C. jejuni, but less severe
-usually foodborne
Campylobacter & Helicobacter - Campylobacter coli - gram stain
-curved, slender GNR
-“GULL WING-shaped”
-loose spirals
-S shaped
-stain faintly
Campylobacter & Helicobacter - Campylobacter coli - culture
-microaerophilic & capnophilic
-grow on CAMPY-BAP at 42C in increased CO2 (can grow at 37C; normal enteric flora inhibited by 42*C incubation)
-slow growing - hold plate 3 days
-NAATs can be used for faster ID
Campylobacter & Helicobacter - Campylobacter coli - key characteristics
-hippurate hydrolysis NEGATIVE
-a MALDI-TOF can be used to differentiate from C.jejunu
Campylobacter & Helicobacter - Campylobacter fetus - pathogenicity
-causes bacteremia in immunocompromised & elderly
-uncommon stool isolate
Campylobacter & Helicobacter - Campylobacter fetus- gram stain
-curved, slender, gram negative rods
-“GULL WING-shaped”
-loose spirals
-S shaped
-stain faintly
Campylobacter & Helicobacter - Campylobacter fetus- culture
-most often isolated in blood cultures
-hold for 2 weeks
-inhibited on Campy agar
-grows on routine media at 37C but NOT at 42C
Campylobacter & Helicobacter - Campylobacter fetus - key characteristics
-oxidase positive
-catalase positive
-hippurate hydrolysis NEGATIVE
Campylobacter & Helicobacter - Helicobacter pylori - pathogenicity
-gastritis
-duodenal & peptic ulcers
-possible risk factor for gastric carcinoma
Campylobacter & Helicobacter - Helicobacter pylori - gram stain
-curved, slender, GNR
Campylobacter & Helicobacter - Helicobacter pylori - culture
-grows on non-selective media incubated at 37C in same atmosphere as Campy
-does NOT grow at 42C
-slow growing
Campylobacter & Helicobacter - Helicobacter pylori - key characteristics
-rarely cultured
-rapid urease tests on gastric biopsy, urea breath test, histology, PCR, serology, and ELISA all can be used for ID
Vibrio and related organisms - Vibrio cholerae - pathogenicity
-Cholera (acute diarrhea, dehydration, electrolyte imbalance)
-transmitted by contaminated water, seafood
-uncommon in the US, but may be seen in coastal areas
Vibrio and related organisms - Vibrio cholerae - gram stain
-small, COMMA-shaped GNR in direct smears
-straight pleomorphic GNR in culture
Vibrio and related organisms - Vibrio cholerae - culture
-non-halophilic (doesn’t require NaCl for growth)
-grows on SBA, CHOC, MAC (NLF)
-large yellow colonies on TCBS (ferments sucrose)
-alkaline peptone water can be used for enrichment
Vibrio and related organisms - Vibrio cholerae - key characteristics
-“RICE WATER” stools
-oxidase positive
-serological ID with anti sera to O ag.
-01 & 0139 strains cause epidemics
-01 strains are divided into 2 serotypes (Inaba and Ogawa) and 2 biotypes (El Tor and classical)
Vibrio and related organisms - Vibrio vulnificus - pathogenicity
-2nd most serious type of vibrio infection
-causes primary septicemia and wound infections most often following consumption of raw oysters
-patients usually have preexisting conditions such as liver disease or immunosuppression
-seen in the US
Vibrio and related organisms - Vibrio vulnificus - gram stain
Straight or curved GNR
Vibrio and related organisms - Vibrio vulnificus - culture
-HALOPHILIC (salt-loving, requires addition of sodium)
-most are green on TCBS; some are yellow
-May look like enteric on MAC because some are lactose positive
Vibrio and related organisms - Vibrio vulnificus - key characteristics
-oxidase positive
-motile
Vibrio and related organisms - Vibrio parahaemolyticus - pathogenicity
-most common cause of bacterial foodborne intestinal infection in Asia
-contaminated seafood
-water-associated wound infections
-seen in US
Vibrio and related organisms - Vibrio parahaemolyticus - gram stain
straight or curved GNR
Vibrio and related organisms - Vibrio parahaemolyticus - culture
-requires 1% NaCl for growth
-grows on SBA, MAC (NLF)
-blue-green colonies on TCBS (doesn’t ferment sucrose)
Vibrio and related organisms - Vibrio parahaemolyticus - key characteristics
-oxidase positive
-motile
Vibrio and related organisms - Aeromonas spp. - pathogenicity
-gastroenteritis & wound infections, often related to aquatic exposure
-septicemia
-meningitis
Vibrio and related organisms - Aeromonas spp. - gram stain
straight or curved GNR with rounded ends
Vibrio and related organisms - Aeromonas spp. - culture
-grows on routine media
-most are beta-hemolytic on SBA
-NLF on MAC
-does NOT grow on TCBS
-CIN agar & APW can be used for selective isolation
Vibrio and related organisms - Aeromonas spp. - key characteristics
-oxidase positive
-motile
-NAATs and MALDI-TOF can be used for ID
Vibrio and related organisms - Plesiomonas shigelloides - pathogenicity
-gastroenteritis from contaminated water or seafood
-bacteremia & meningitis in immunocompromised & neonates
Vibrio and related organisms - Plesiomonas shigelloides - gram stain
pleomorphic GNR in singles, pairs, short chains, or long filaments
Vibrio and related organisms - Plesiomonas shigelloides - culture
-grows on SBA, CHOC
-most grow on MAC, appear as NLF
-does NOT arrow on TCBS
Vibrio and related organisms - Plesiomonas shigelloides - key characteristics
-biochemical & antigenic similarities to Shigella
-oxidase positive
-motile
Haemophilus - H. influenzae - pathogenicity
-normal flora of upper respiratory tract
-causes: sinusitis, otitis media, pneumonia, bronchitis, often in elderly & immunocompromised
-type b - common cause of pneumonia & meningitis in children where Hib vaccine not available
Haemophilus - H. influenzae - gram stain
-small, pleomorphic GNCB to long filaments
-capsules may be seen
Haemophilus - H. influenzae - culture
-grows on CHOC in 5-10% CO2
-medium for optimum recovery should contain at least 10 mcg/mL of free X and V factors
-translucent, moist, tannish colonies
-encapsulated strains form larger & more mucoid colonies
-MOUSY or BLEACH-like odor
-may demonstrate SATELLITISM with staph on SBA
Haemophilus - H. influenzae:
-porphyrin & porphobilinogen
-NAATs
-porphyrin & porphobilinogen negative
-NAATs can be used to detect from CSF, plasma, serum, and whole blood
Haemophilus - H. influenzae biotype aegyptius & H. aegyptius - pathogenicity
-both cause conjunctivitis (pink eye)
-H. influenzae biotype aegyptius also causes Brazilian purpuric fever
Haemophilus - H. influenzae biotype aegyptius & H. aegyptius - gram stain
-small, pleomorphic GNCB to long filaments
-capsules may be seen
Haemophilus - H. influenzae biotype aegyptius & H. aegyptius - culture
-grows on CHOC in 5-10% CO2
-medium for optimum recovery should contain at least 10 mcg/mL of free X and V factors
-translucent, moist, tannish colonies
-encapsulated strains form larger & more mucoid colonies
-MOUSY or BLEACH-like odor
-may demonstrate SATELLITISM with staph on SBA
Haemophilus - H. influenzae biotype aegyptius & H. aegyptius:
-characteristics are similar to?
-characteristics are similar to H. influenzae
-difficult to differentiate unless molecular methods are employed
Haemophilus - H. parainfluenzae, H. haemolyticus, & H. parahaemolyticus - pathogenicity
-normal flora of upper respiratory tract
-low incidence of pathogenicity
Haemophilus - H. parainfluenzae, H. haemolyticus, & H. parahaemolyticus - gram stain
small, pleomorphic GNCB to long filaments
Haemophilus - H. parainfluenzae, H. haemolyticus, & H. parahaemolyticus - culture
colonies are larger, dry, & tannish
Haemophilus - H. parainfluenzae, H. haemolyticus, & H. parahaemolyticus - which species is porphyrin positive?
H. parainfluenzae
Haemophilus - H. ducreyi - pathogenicity
-NEVER normal flora
-causes chancroid (STD)
-rare
Haemophilus - H. ducreyi - gram stain
-small GNCB
-bipolar staining
-may resemble SCHOOL OF FISH or RAILROAD TRACKS
Haemophilus - H. ducreyi - culture
difficult to culture without the use of many growth factors in the media
(can identify by PCR)
Speciation of Haemophilus - H. influenzae & H. aegyptius:
-requires X factor (hemin)?
-requires V factor (NAD)?
-hemolysis on rabbit or horse blood agar/
-porphyrin/delta-aminolevulinic acid (ALA)?
-X factor? YES
-V factor? YES
-hemolysis? NO
-porphyrin/delta-ALA? NO
Speciation of Haemophilus - H. parainfluenzae:
-requires X factor (hemin)?
-requires V factor (NAD)?
-hemolysis on rabbit or horse blood agar/
-porphyrin/delta-aminolevulinic acid (ALA)?
-X factor? NO
-V factor? YES
-hemolysis? NO
-porphyrin/delta-ALA? YES
Speciation of Haemophilus - H. haemolyticus:
-requires X factor (hemin)?
-requires V factor (NAD)?
-hemolysis on rabbit or horse blood agar/
-porphyrin/delta-aminolevulinic acid (ALA)?
-X factor? YES
-V factor? YES
-hemolysis? YES
-porphyrin/delta-ALA? NO
Speciation of Haemophilus - H. parahaemolyticus:
-requires X factor (hemin)?
-requires V factor (NAD)?
-hemolysis on rabbit or horse blood agar/
-porphyrin/delta-aminolevulinic acid (ALA)?
-X factor? NO
-V factor? YES
-hemolysis? YES
-porphyrin/delta-ALA? YES
Speciation of Haemophilus - H. parahaemolyticus:
-requires X factor (hemin)?
-requires V factor (NAD)?
-hemolysis on rabbit or horse blood agar/
-porphyrin/delta-aminolevulinic acid (ALA)?
-X factor? YES
-V factor? NO
-hemolysis? NO
-porphyrin/delta-ALA? NO
Misc. gram-negative rods - Bartonella - pathogenicity
-trench fever
-relapsing fever
-bacteremia
-endocarditis
-CAT-SCRATCH disease
Misc. gram-negative rods - Bartonella - gram stain
gram-negative pleomorphic rods
Misc. gram-negative rods - Bartonella - culture
-not practical
-takes 9-40 days to grow
-requires heme for growth
Misc. gram-negative rods - Bartonella - key characteristics
-identify by nucleic acid technique
Misc. gram-negative rods - Bordetella pertussis - pathogenicity
-whooping cough in children and adults
-DTaP vaccine is available
Misc. gram-negative rods - Bordetella pertussis - gram stain
small GNCB
Misc. gram-negative rods - Bordetella pertussis - culture
grows on Bordet-Gengou & Regan-Lowe (charcoal, horse’s blood) after 3-7 days
Misc. gram-negative rods - Bordetella pertussis - key characteristics
MALDI-TOF or agglutination with specific antibodies for ID
Misc. gram-negative rods - Brucella - pathogenicity
-Brucellosis (undulent fever)
-from unpasteurized milk or contact with infected goats, cows, hogs, dogs
Misc. gram-negative rods - Brucella - gram stain
tiny, faintly staining GNCB
Misc. gram-negative rods - Brucella - culture
-most often isolated from blood cultures or biopsies of reticuloendothelial (RE) tissue
-blood cultures incubated in increased CO2 for 3 weeks
-culture is not sensitive
Misc. gram-negative rods - Brucella - key characteristics
-oxidase positive
-catalase positive
-urease positive
-potential bioterrorism agent
-reportable disease
-slide agglutination test with specific antibodies used for ID
Misc. gram-negative rods - Francisella - pathogenicity
-Tularemia (rabbit fever)
-human infected by tick or handling infected animal
Misc. gram-negative rods - Francisella - gram stain
-pale staining, small, pleomorphic, INTRACELLULAR GNCB with bipolar staining
Misc. gram-negative rods - Francisella - culture
-grows on special media enriched with glucose & cystine (e.g., blood cystine glucose agar), Thayer-Martin (TM), & BCYE
-small, transparent colonies after 3 days
Misc. gram-negative rods - Francisella - key characteristics
-level 3 pathogen
-direct fluorescent antibody methods for ID
-send to public health lab for confirmation
Misc. gram-negative rods - Gardnerella - pathogenicity
-normal flora of female genital tract
-associated with bacterial vaginosis (BV) when it & anaerobic GNR are predominant & Lactobacillus is absent
-linked to maternal & neonatal infections, bacteremia, rarely UTI
Misc. gram-negative rods - Gardnerella - gram stain
small, pleomorphic gram-variable rods
Misc. gram-negative rods - Gardnerella - culture
-not recommended for diagnosis of BV
-grows on SBA, PEA, CNA, human blood Tween (HBT) agar, V agar
-produces diffuse beta hemolysis only on media containing human blood
-requires increased CO2 & 48-72 hour incubation
Misc. gram-negative rods - Gardnerella - key characteristics
-catalase negative
-oxidase negative
-tests for Dx of BV: CLUE CELLS (vaginal epithelial cells covered with gram-variable rods), whiff test (10% KOH added to vaginal secretion => fish-like odor)
Misc. gram-negative rods - Legionella - pathogenicity
-Legionnaire disease
-Pontiac fever
-found in water (e.g., air conditioners, shower-heads, whirlpools)
-contracted by inhalation of aerosol
Misc. gram-negative rods - Legionella - gram stain
small, pleomorphic, weakly staining GNR (sometimes filamentous)
Misc. gram-negative rods - Legionella - culture
-grows on BCYE in 3-4 days
-pale yellow-green fluorescence with WOOL LAMP
Misc. gram-negative rods - Legionella - key characteristics
-oxidase positive
-ID by immunofluorescent stain or agglutination methods
-MALDI-TOF can also be used
Misc. gram-negative rods - Pasteurella multicoda - pathogenicity
-contracted by bite or scratch of cat or dog or contact with infected carcass
-wound & soft tissue infection
Misc. gram-negative rods - Pasteurella multicoda - gram stain
pleomorphic GNCB with bipolar staining
Misc. gram-negative rods - Pasteurella multicoda - culture
-grows on SBA & CHOC, but NOT MAC
-MUSTY odor
Misc. gram-negative rods - Pasteurella multicoda - key characteristics
-oxidase positive
-catalase positive
-indole positive
-weak oxidase reaction after 30 minutes of being characteristic of Pasteurella
-MALDI-TOF can also be used for ID
Specimens for anaerobic culture - bile - acceptable or unacceptable?
Acceptable
Specimens for anaerobic culture - blood - acceptable or unacceptable?
Acceptable
Specimens for anaerobic culture - body fluids - acceptable or unacceptable?
Acceptable
Specimens for anaerobic culture - bone marrow - acceptable or unacceptable?
Acceptable
Specimens for anaerobic culture - percutaneous lung aspirate or biopsy - acceptable or unacceptable?
Acceptable
Specimens for anaerobic culture - suprapubic bladder aspirates - acceptable or unacceptable?
Acceptable
Specimens for anaerobic culture - tissue - acceptable or unacceptable?
Acceptable
Specimens for anaerobic culture - transtracheal aspirate - acceptable or unacceptable?
Acceptable
Specimens for anaerobic culture - wound - acceptable or unacceptable?
Acceptable
Specimens for anaerobic culture - expectorated sputum - acceptable or unacceptable?
Unacceptable
Specimens for anaerobic culture - feces - acceptable or unacceptable?
Unacceptable
Specimens for anaerobic culture - gastric juice - acceptable or unacceptable?
Unacceptable
Specimens for anaerobic culture - swabs - acceptable or unacceptable?
Unacceptable
Specimens for anaerobic culture - voided or catheterized urine - acceptable or unacceptable?
Unacceptable
Specimens for anaerobic culture - bronchial washings (unless obtained with double lumen plugged catheter) - acceptable or unacceptable?
Unacceptable
Media for culture of anaerobes - Anaerobic blood agar-CDC - use? contains?
-non-selective enrichment medium that grows obligate & facultative anaerobes
-contains yeast extract, L-cysteine, hemin, & vitamin K
Media for culture of anaerobes - Bacteroides bile-esculin (BBE) agar - use? contains? function? B. fragilis colonies?
-selective differential medium for Baceteroides fragilis
-bile salts & gentamicin act as inhibitors
-B. fragilis colonies are black with dark halos due to esculin hydrolysis
Media for culture of anaerobes - Brucella blood agar - use?
enrichment medium that grows obligate & facultative anaerobes
Media for culture of anaerobes - CNA blood agar - use?
selective medium that grows obligate anaerobes & GP facultative anaerobes
Media for culture of anaerobes - Cycloserine cefoxitin fructose egg yolk (CCFA) agar - use? colonies? fluorescence?
-selective & differential for Clostridium difficile
-C. diff colonies are yellow due to fermentation of fructose
-Chartreuse fluorescence
Media for culture of anaerobes - Egg-yolk agar (EYA) - use?
-for determination of lecithinase & lipase production by clostridia & fusobacteria
Media for culture of anaerobes - Kanamycin-vancomycin laked blood (KVLB) agar - use? also known as?
-selective medium for isolation of anaerobic GNRs, especially Bacteroides & Prevotella
-also known as laked blood kanamycin-vancomycin (LKV) agar
Media for culture of anaerobes - PEA agar - use?
-selective medium:
—inhibits enteric GNRs
—grows obligate anaerobes & GP facultative anaerobes
Media for culture of anaerobes - Thioglycolate (THIO) broth - use? function? growth? storage? requirements before use?
-all-purpose medium that supports growth of most aerobes & anaerobes; can be used as backup broth to detect organisms present in small numbers or anaerobes
-THIO acts as a reducing agent
-Growth:
—aerobes grow at the top
—strict anaerobes grow at the bottom
—facultative anaerobes grow throughout
-store at RT
-boil & cool before use
Methods to identify anaerobes - gram stain - how does it help ID? GN anaerobes & safranin? GP anaerobes?
-gram reaction; morphology; presence, location, & shape of spores
-some GN anaerobes stain faintly with safranin; extend time of counter staining to 3-5 minutes or use 0.1% basic fuchsin
-some GP anaerobes, e.g., Clostridium, May stain pink
Methods to identify anaerobes - growth on media - how it helps ID
-which media organism grows on
-pigmentation
-hemolysis
-colony morphology
Methods to identify anaerobes - special-potency antimicrobial disks - how does it help ID
-kanamycin, vancomycin, & colistin disks help differentiate anaerobes & ensure that over-decolorized Clostridium is not misidentified as GNR
-the disk is placed on the first quadrant of the plate; after incubation , observe if organism is susceptible or resistant
Methods to identify anaerobes - rapid tests - how do they help ID
-presumptive ID, e.g., fluorescence; catalase; spot indole; urease; motility; sodium polyanethanol sulfonate (SPS), nitrate, & bile disks; lecithinase, lipase, & proteolytic reaction on EYA
Methods to identify anaerobes - conventional tubes biochemicals
-test tubes containing variety of media inoculated & incubated in anaerobic environment
-reaction leads to change in pH
-expensive & time consuming
-largely replaced by multitest systems
Methods to identify anaerobes - preformed enzyme-based systems
-detect preexisting enzymes
-panels or cards are inoculated & incubated in room air
-color changes are read in 4 hours
-code number obtained & ID determined from code book
-only contains codes for most commonly isolated anaerobes
Methods to identify anaerobes - gas-liquid chromatography (GLC)
-analysis of metabolic end products or cellular fatty acids
-not frequently used
Methods to identify anaerobes - 16S ribosomal RNA gene sequencing
-DNA extracted from organism, amplified by PCR, sequenced on automated sequencer
-nucleotide sequence compared with known sequences in database
Methods to identify anaerobes - MALDI-TOF
-extremely sensitive method requiring little sample volume for ID
-the mass spectra generated are compared to known databases
Anaerobic gram-positive cocci - Finegoldia magna (formerly Peptostreptococcus magnus) - pathogenicity
-normal flora on skin & in mouth, intestines, female genital tract
-most commonly isolated & most pathogenic anaerobic GPC
-associated with skin infections, decubitus ulcers, septic arthritis, bone infection following orthopedic surgery, oral & female genital tract infections, bacteremia
Anaerobic gram-positive cocci - Finegoldia magna (formerly Peptostreptococcus magnus) - gram stain
-GPC in singles, pairs, retreads, clusters
-resembles staph
Anaerobic gram-positive cocci - Finegoldia magna (formerly Peptostreptococcus magnus) - characteristics
-small colonies
-May take 48 hours to grow
-catalase negative
-indole negative
-resistant to SPS
Anaerobic gram-positive cocci - Peptostreptococcus anaerobius - pathogenicity
-normal flora on skin& mouth, GI, & genitourinary (GU) tracts
-mixed infections of skin, soft tissues, GI tract, female genital tract, bones, joints, lungs, brain
Anaerobic gram-positive cocci - Peptostreptococcus anaerobius - gram stain
-tiny GPC in chains
-resembles strep
Anaerobic gram-positive cocci - Peptostreptococcus anaerobius - characteristics
-small gray-white colonies in 24-48 hours
-SWEET odor
-sensitive to SPS
Anaerobic gram-positive cocci - Peptoniphilus asaccharolyticus (formerly *Peptostreptococcus assaccharolyticus) - pathogenicity
-normal on skin & in GI & GU tracts
-associated with obstetric & gynecological infections
Anaerobic gram-positive cocci - Peptoniphilus asaccharolyticus (formerly *Peptostreptococcus assaccharolyticus) - characteristics
-yellow colonies
-MUSTY odor
-resistant to SPS
-indole positive
Anaerobic gram-positive cocci - Peptoniphilus asaccharolyticus (formerly *Peptostreptococcus assaccharolyticus) - gram stain
-GPC in pairs, short chains, tetrads, clusters
-some strains decolorize easily and can be confused with gram-negative anaerobes
Anaerobic gram-positive rods - Actinomyces - pathogenicity
-normal inhabitants of mucosal surfaces throughout the body
-infects brain, face, lungs, genitals
Anaerobic gram-positive rods - Actinomyces - gram stain
-short or long gram-positive rods (GPR)
-branched or unbranched
-BANDED appearance
-can break into club-shaped rods resembling diphtheroids
Anaerobic gram-positive rods - Actinomyces - characteristics
-sulfur granules may be seen in discharge
-crush & stain to reveal characteristic gram-stain morphology
-“MOLAR TOOTH” colonies
Anaerobic gram-positive rods - *Clostridium botulinum * - pathogenicity
-botulism due to ingestion of toxin in inadequately cooked or improperly canned foods
-infant botulism due to ingestion of spores in honey
-wound botulism from injection drug use
Anaerobic gram-positive rods - *Clostridium botulinum * - gram stain
-GPR with oval subterminal spores
Anaerobic gram-positive rods - *Clostridium botulinum * - characteristics
-reportable disease
-toxin testing at public health labs
Anaerobic gram-positive rods - Clostridioides difficile - pathogenicity
-antibiotic-associated diarrhea
-pseudomembranous colitis
Anaerobic gram-positive rods - Clostridioides difficile - gram stain
-thin GPR
-May form chains
-rare oval subterminal spores
Anaerobic gram-positive rods - Clostridioides difficile - characteristics
-yellow GROUND GLASS colonies on CCFA
-usually not cultured
-must demonstrate toxin production
-toxins A & B
-tissue culture molecular methods or enzyme immunoassay (EIA) to confirm
Anaerobic gram-positive rods - Clostridium perfringens - pathogenicity
-normal in GI tract
-causes gas gangrene
-most common bacterial cause in US
-can produce more than 16 different toxins and is classified by toxinotype
Anaerobic gram-positive rods - Clostridium perfringens - gram stain
-large GPR with BLUNT ends in chains
-“BOX CARS”
-tendency to stain gram negative
-usually no spores seen
Anaerobic gram-positive rods - Clostridium perfringens - characteristics
-most commonly isolated Clostridium
-double zone of beta hemolysis on SBA
Anaerobic gram-positive rods - Clostridium tetani - pathogenicity
-causes tetanus
-deep wounds infected with soil
Anaerobic gram-positive rods - Clostridium tetani - gram stain
-GPR with swollen terminal spores
-“DRUMSTICK”
-“TENNIS RACQUET”
-becomes gram-negative after 24 hours
Anaerobic gram-positive rods - Clostridium tetani - characteristics
-rare in US because of DTap vaccine but common worldwide
-lab confirmation rarely required
Anaerobic gram-positive rods - Cutibacterium (formerly Propionibacterium) - pathogenicity
-normal skin flora
-common contaminant of blood cultures
-causes acne
-infections associated with artificial joints, cathethers, shunts, artificial heart valves
-keratitis
-bacteremia
-endocarditis
Anaerobic gram-positive rods - Cutibacterium (formerly Propionibacterium) - gram stain
-CLUB-shaped, pleomorphic GPR
-diphtheroid-like
Anaerobic gram-positive rods - Cutibacterium (formerly Propionibacterium) - characteristics
-most common anaerobic GPR
-catalase positive
-indole positive
Anaerobic gram-positive rods - Lactobacillus - pathogenicity
-normal in mouth, GI tract
-predominant & beneficial flora of vagina during reproductive years
-produces lactic acid, maintains vaginal pH
-absence in vagina predisposes to BV & yeast infections
-rare cause of endocarditis, septicemia in immunocompromised
-
Anaerobic gram-positive rods - Lactobacillus - gram stain
-pleomorphic, long, thin, non-spore-forming GPR, often in chains
-chains of rods in THIO
Anaerobic gram-positive rods - Lactobacillus - characteristics
-aerotolerant anaerobes
-grow better under anaerobic conditions
-colonies vary greatly
-may resemble S. viridans
-catalase negative
Gram-negative anaerobes - GNC - Veillonella - pathogenicity
-normal flora of upper respiratory tract, GI & GU tracts
-usually in mixed culture
-can cause infections in immunocompromised
Gram-negative anaerobes - GNC - Veillonella - gram stain
-tiny GNDC in pairs, clusters, short chains
-can resemble Neisseria
Gram-negative anaerobes - GNC - Veillonella - characteristics
-may show weak red fluorescence under UV light
-does NOT grow on KVLB
-usually doesn’t reduce nitrates
Gram-negative anaerobes - GNR - Bacteroides fragilis - pathogenicity
-main anaerobic organism recovered from intraabdominal infections
-also causes endocarditis
-more virulent and antibiotic resistant than most other anaerobes
Gram-negative anaerobes - GNR - Bacteroides fragilis - gram stain
pleomorphic, pale, irregularly staining GNR
Gram-negative anaerobes - GNR - Bacteroides fragilis - characteristics
-resistant to bile
-hydrolyzes esculin
-turns BBE brown
Gram-negative anaerobes - GNR - Fusobacterium - pathogenicity
-pulmonary infections
-brain abscesses
-oral lesions
Gram-negative anaerobes - GNR - Fusobacterium - gram stain
-GNR
-F. nucleatum is long & thin with tapered ends (SPINDLE-shaped)
Gram-negative anaerobes - GNR - Fusobacterium - characteristics
-indole positive
-most fluoresce CHARTREUSE (green-yellow) under UV light
Gram-negative anaerobes - GNR - Porphyromonas - pathogenicity
head, neck, & pleuropulmonary infections
Gram-negative anaerobes - GNR - Porphyromonas - gram stain
GNCB
Gram-negative anaerobes - GNR - Porphyromonas - characteristics
-slow growing
-brown to black on SBA
-some fluoresce brick-red to orange under UV light
-doesn’t grow on KVLB
Gram-negative anaerobes - GNR - Prevotella - pathogenicity
head, neck, & pleuropulmonary infections
Gram-negative anaerobes - GNR - Prevotella - gram stain
GNCB
Gram-negative anaerobes - GNR - Prevotella - characteristics
-slow growing
-some are pigmented
-brown to black on SBA & KVLB
-some fluoresce brick-red to orange under UV light
-doesn’t grow on BBE
Laboratory ID of Mycobacteria - lab safety
-non-recirculating ventilation system
-negative air pressure
-BS-2 for non-aerosol-producing activities
-BS-3 for manipulation of cultures and susceptibility testing
-electric incinerators instead of flames to sterilize wire loops
-slide-warming trays instead of flames to fix slides
-tuberculocidal disinfectants to clean equipment & BSC (1:10 dilution of household bleach)
-UV light in BSC (only when not in use)
-annual testing of employees for exposure
Laboratory ID of Mycobacteria - specimens requiring digestion/decontamination
Sputum & other specimens with normal flora such as gastric lavage, urine, feces
Laboratory ID of Mycobacteria - specimens NOT requiring digestion/decontamination
Tissue or body fluids collected aseptically
Laboratory ID of Mycobacteria - digestion/decontamination methods
-sodium hydroxide (NaOH) - digestant and decontaminant
-N-acetyl-L-cysteine/NaOH - NALC is a liquefying agent
-benzalkonium chloride
-oxalic acid
Laboratory ID of Mycobacteria - staining
-cell walls have a high lipid content (mycolic acids)
-difficult to stain
-resist decolorization by acid alcohol (acid-fast)
-gram stain poorly
-use carbolfuchsin or fluorochrome acid-fast stains
Laboratory ID of Mycobacteria - media
-agar-based (Middlebrook 7H10 & 7H11)
-egg-based (Löwenstein-Jensen, Petragnani, American Thoracic Society)
-liquid (Middlebrook 7H9)
-combination of a solid-based medium & a liquid-based medium recommended for primary isolation
Laboratory ID of Mycobacteria - incubation
35*C in 5-10% CO2
(EXCEPTION: if M. marinum, M. ulcerans, or M. haemophilum suspected, incubate at 25-30*C)
Laboratory ID of Mycobacteria - rate of growth
-slow
-on solid media, most require 2-6 weeks incubation
-rapid growers = 2-3 days
-more rapid growth in liquid media
Laboratory ID of Mycobacteria - automated systems for recovery
-liquid broth inoculated
-placed in blood culture instrument for automatic or continuous monitoring
-growth indicated by consumption of O2 or production of CO2
-Vitek MS is FDA approved & provides fast turnaround time
Laboratory ID of Mycobacteria - methods of identification
-colony morphology
-growth rate
-optimum temp for growth
-photoreactivity
-biochemical tests
-smear microscopy
-nucleus acid hybridization
-PCR
-automated DNA sequencing
-MALDI-TOF
Acid-fast stains - Ziehl-Neelsen:
-primary stain?
-decolorizer?
-counterstain?
-Primary stain: Carbolfuchsin
-Decolorizer: acid alcohol
-Counterstain: methylene blue
Acid-fast stains - Kinyoun:
-primary stain?
-decolorizer?
-counterstain?
-Primary stain: carbolfuchsin
-Decolorizer: acid alcohol
-Counterstain: methylene blue
Acid-fast stains - Fluorochrome:
-primary stain?
-decolorizer?
-counterstain?
-Primary stain: auramine-rhodamine
-Decolorizer: acid alcohol
-Counterstain: potassium permanganate OR acridine orange
Acid-fast stains - Ziehl-Neelsen - appearance of AFB
-red, slightly curved, beaded rods (2-8 um)
-blue background
Acid-fast stains - Kinyoun - appearance of AFB
-red, slightly curved, beaded rods (2-8 um)
-blue background
Acid-fast stains - Fluorochrome - appearance of AFB
yellow-orange rods against a dark background
Acid-fast stains - Ziehl-Neelsen - technique? modification?
-requires heat
-examine at least 300 OI fields
-wipe lens after positive smears to avoid cross-contamination & false positives
-can be modified for improved detection by adding cytospin and Triton processing
Acid-fast stains - Kinyoun - technique
-cold stain
-examine at least 300 OI fields
-wipe lens after positive smears to avoid cross-contamination & false positives
Acid-fast stains - Fluorochrome - technique
-more sensitive & faster than carbolfuchsin
-can examine at 250X
-read immediately or store at 2-8*C in dark to avoid fading
-examine at least 300 fields
-POSITIVE should be confirmed with carbolfuchsin stain
-rapid 2 minute stain now available
Classification of Mycobacteria based on pathogenicity - Mycobacterium tuberculosis complex (“tubercle bacilli”) - pathogenicity
cause human tuberculosis
Classification of Mycobacteria based on pathogenicity - Mycobacterium tuberculosis complex (“tubercle bacilli”) - species
Most predominant:
-M. tuberculosis
-M. bovis
-M. africanum
-M. microti
Others:
-M. canetti
-M. pinnipedii
Classification of Mycobacteria based on pathogenicity - Atypical mycobacteria, nontuberculous mycobacteria (NTM), or mycobacteria other than tubercle (MOTT) bacilli - pathogenicity
-some cause pulmonary infection similar to TB but not transmitted person to person
-usually in immunocompromised
-contracted from environment (soil, water)
Classification of Mycobacteria based on pathogenicity - Atypical mycobacteria, nontuberculous mycobacteria (NTM), or mycobacteria other than tubercle (MOTT) bacilli - species
-M. avium
-M. intracellulare
-M. kansaii
-M. malmoense
-M. chelonae
-M. xenopi
-M. gordonae
Medically important Mycobacteria - M. tuberculosis - pathogenicity
TB
Medically important Mycobacteria - M. tuberculosis - characteristics
-slow growth
-average recovery time by conventional methods is 21 days
-rough, dry, buff-colored (no pigmentation) colonies
-serpentine cording on smear from culture
-niacin & nitrate positive
-68*C catalase negative
Medically important Mycobacteria - M. bovis - pathogenicity
causes disease similar to M. tuberculosis and is treated accordingly
Medically important Mycobacteria - M. bovis - characteristics
-resistant to pyrazinamide
-Bacille Calmette-Guerin (BCG) is attenuated strain used in vaccine in some parts of the world
-causes false-pos purified protein derivative (PPD) test
Medically important Mycobacteria - M. africanum - pathogenicity
-causes lung infection
-disseminated disease in immunocompromised
Medically important Mycobacteria - M. africanum - characteristics
-spread by respiratory droplets
-endemic in equatorial Africa
-rare in the US
Medically important Mycobacteria - M. avium complex - pathogenicity
-most common NTM to cause lung disease in US
-most common systemic bacterial infection in AIDS patients
-cervical lymphadenitis in children
Medically important Mycobacteria - M. avium complex - characteristics
-M. avium and M. intracellulare most commonly cause lung disease
-contracted from environment
Medically important Mycobacteria - M. haemophilum - pathogenicity
-skin, joint, bone, lung infections in immunocompromised
-lymphadenitis in children
Medically important Mycobacteria - M. haemophilum - characteristics
-requires hemin for growth
-grows Best at 28-30*C
Medically important Mycobacteria - M. ulcerans - pathogenicity
-chronic infection of skin& subcutaneous tissue
-Buruli ulcers
Medically important Mycobacteria - M. ulcerans - characteristics
-endemic in tropics
-3rd most common mycobacterial disease after TB & leprosy
-grows best at 30*C
-molecular techniques aid ID
Medically important Mycobacteria - M. kansaii - pathogenicity
-2nd common NTM to cause lung disease
-causes skin& soft tissue infections, lymphadenitis
-can disseminate in immunocompromised
Medically important Mycobacteria - M. kansaii - characteristics
-often found in tap water
-photochromogen
-can ID by 16sRNA probe
Medically important Mycobacteria - M. marinum - pathogenicity
skin infections
Medically important Mycobacteria - M. marinum - characteristics
-contracted from swimming pools, aquariums
-grows best at 28-30*C
-photochromogen
Medically important Mycobacteria - M. simiae - pathogenicity
-rare but associated with chronic respiratory infection
Medically important Mycobacteria - M. simiae - characteristics
-difficult to treat due to multi drug resistance (MDR)
-high mortality & morbidity
Medically important Mycobacteria - M. gordonae - pathogenicity
rarely causes infection (lab contaminant)
Medically important Mycobacteria - M. gordonae - characteristics
-“tap-water bacillus”
-scotochromogen (does not require light to produce pigment)
Medically important Mycobacteria - M. abscessus - pathogenicity
-in water, soil, dust
-contaminant of medical devices
-skin & soft tissue infections
-lung infections in those with chronic lung disease, e.g., cystic fibrosis
-disseminated infection in immunocompromised
Medically important Mycobacteria - M. abscessus - characteristics
-rapid grower
-tap water reservoir
Medically important Mycobacteria - M. chelonae - pathogenicity
-disseminated cutaneous infections in immunocompromised
-infections of lungs, bone, CNS, prosthetic heart valves
Medically important Mycobacteria - M. chelonae - characteristics
Rapid grower
Medically important Mycobacteria - M. fortuitum - characteristics
-rapid grower
-common in environment
-weakly gram positive
-stains with carbolfuchsin, but may not with fluorescent stain
Medically important Mycobacteria - M. fortuitum - pathogenicity
infection of skin, soft tissues, IV & injection sites, surgical wounds
Medically important Mycobacteria - M. leprae - pathogenicity
Leprosy (Hansen disease)
Medically important Mycobacteria - M. leprae - characteristics
-endemic in Southern hemisphere
-<100 cases per year in US
-most cases in Texas, California, Louisiana, Hawaii, Puerto Rico
-armadillos may be reservoir
-doesn’t grow on artificial media
-can be grown in footpads of mice & armadillos
-Dx by acid-fast stain of tissue
-less acid fast than M. tuberculosis
Chlamydia and Chlamydophila - Chlamydia trachomatis - pathogenicity
-most common STD bacterial infection in US
-trachoma
-lymphogranuloma venereum
-non-gonococcal urethritis
-pelvic inflammatory disease
-pneumonia & conjunctivitis in newborns
Chlamydia and Chlamydophila - Chlamydia trachomatis - laboratory diagnosis
-Giemsa stain
-direct fluorescent antibody stain
-NAATs (most common)
Chlamydia and Chlamydophila - Chlamydia trachomatis - characteristics
-obligate intracellular parasite
-need epithelial cells for culture
-wooden swabs are toxic
-NAAT preferred for genital and first-catch urine specimens
-commercial systems available for simultaneous detection of M. gonorrhoeae
Chlamydia and Chlamydophila - Chlamydia pneumoniae - pathogenicity
3rd most common cause of acute RTI
Chlamydia and Chlamydophila - Chlamydia pneumoniae - laboratory diagnosis
serological or molecular tests are method of choice
Chlamydia and Chlamydophila - Chlamydia pneumoniae - characteristics
-obligate intracellular parasite
-risk factor for Guillain-Barre syndrome
Chlamydia and Chlamydophila - Chlamydia psittaci - pathogenicity
-Psittacosis (“PARROT FEVER”)
-rare in the US
Chlamydia and Chlamydophila - Chlamydia psittaci - laboratory diagnosis
serological or molecular tests
Chlamydia and Chlamydophila - Chlamydia psittaci - characteristics
-obligate intracellular parasite
-spread by BIRDS
Spirochetes - Borrelia recurrentis - pathogenicity
Relapsing fever
Spirochetes - Borrelia recurrentis - laboratory diagnosis
-Giemsa-or Wright-stained blood smears
-thrombocytopenia is common
Spirochetes - Borrelia recurrentis - characteristics
-transmitted by ticks & lice
-there are over 20 species in the relapsing fever Borrelia group but B. recurrentis causes the most cases
Spirochetes - Borrelia burgdorferi sensu lato - pathogenicity
-Lyme disease (erythema chronicum migrans, neurological & cardiac abnormalities, arthritis)
Spirochetes - Borrelia burgdorferi sensu lato - laboratory diagnosis
-grows on modified Kelly medium
-ELISA is most common method
Spirochetes - Borrelia burgdorferi sensu lato - vector
Ixodes tick
What is the most commonly reported tick-borne infection in the United State?
Borrelia burgdorferi (Lyme disease)
Spirochetes - Treponema pallidum subspecies pallidum - pathogenicity
Syphilis
Spirochetes - Treponema pallidum subspecies pallidum -laboratory diagnosis
-doesn’t grow on artificial media
-darkfield microscopy, fluorescent stain
-serology (EIA) is most common method
Spirochetes - Leptospira interrogans - pathogenicity
Weil disease (infectious jaundice, leptospirosis)
Spirochetes - Leptospira interrogans - laboratory diagnosis
-PCR or serological tests
-can culture: growth = turbidity below surface of semisolid media such as Ellinghausen-McCullough-Johnson-Harris (EMJH)
-hold cultures for 13 weeks
Spirochetes - Leptospira interrogans - characteristics
-zoonotic disease
-transmitted by urine of infected animal
-organism in blood & CSF during first week, then urine
-common in tropical regions
Mycoplasma/Ureaplasma - Mycoplasma pneumoniae - pathogenicity
primary atypical pneumonia (walking pneumonia)
Mycoplasma/Ureaplasma - Mycoplasma pneumoniae - characteristics
-smallest free-living cells
-LACK CELL WALL
-pleomorphic
-not visible by Gram staining
-difficult to grow
-culture rarely performed
-may take 21 days or more
-usually Dx by serology
Mycoplasma/Ureaplasma - Mycoplasma hominis - pathogenicity
urogenital tract disease
Mycoplasma/Ureaplasma - Mycoplasma hominis - characteristics
-only species that will grow on SBA & CHOC but may require 4 days
-PINPOINT translucent colonies easily overlooked
-“FRIED-EGG” colonies seen with stereomicroscope after staining with methylene blue
-serological methods available
Mycoplasma/Ureaplasma - Ureaplasma urealyticum - pathogenicity
urogenital tract disease
Mycoplasma/Ureaplasma - Ureaplasma urealyticum - characteristics
-granular brown appearance on A8 agar because of urease production
-serological methods available
Rickettsia, Ehrlichia, and Coxiella - Rickettsia - pathogenicity
-Rocky mountain spotted fever
-rickettsial pox
-epidemic typhus
-murine typhus
-scrub typhus
Rickettsia, Ehrlichia, and Coxiella - Rickettsia - laboratory diagnosis
-don’t grow on artificial media
-grow in lice, ticks, tissue culture, eggs
-usually Dx by serology
-immunohistologic & molecular methods available
Rickettsia, Ehrlichia, and Coxiella - Rickettsia - characteristics
-obligate intracellular parasite
-transmitted by ticks, mites, lice, fleas
-Rocky mountain spotted fever is most common rickettsial infection in the US - caused by R. rickettsii
-BSL-3 biohazard
Rickettsia, Ehrlichia, and Coxiella - Coxiella - pathogenicity
Q fever
Rickettsia, Ehrlichia, and Coxiella - Coxiella - laboratory diagnosis
-usual Dx by NAATs and serology
-IFA and imaging available
Rickettsia, Ehrlichia, and Coxiella - Coxiella - characteristics
-obligate intracellular parasite
-zoonotic disease
-found in cattle, sheep, goats
-highly contagious
-BSL-3 biohazard
-reportable disease
-potential bioterrorism agent
Rickettsia, Ehrlichia, and Coxiella - Ehrlichia - pathogenicity
Ehrlichiosis
Rickettsia, Ehrlichia, and Coxiella - Ehrlichia - laboratory diagnosis
-morulae (clusters of organisms that resemble blackberry) in WBCs
-usual Dx by serology, molecular amplification, and blood smear examination
Rickettsia, Ehrlichia, and Coxiella - Ehrlichia - characteristics
-obligate intracellular parasites
-infects WBCs
-transmitted by ticks
-disease similar to Rocky Mountain spotted fever
Routine culture setup and interpretation - Throat/nasopharynx - media
-SBA
-CHOC
-Streptococcus-selective agar may be used
Routine culture setup and interpretation - Throat/nasopharynx - normal flora
-alpha & gamma strep
-commensal Neisseria
-CNS
-diphtheroids
-S. pneumoniae
-Candida
Routine culture setup and interpretation - Throat/nasopharynx - common pathogens
-GAS (S. pyogenes)
Routine culture setup and interpretation - Throat/nasopharynx - diagnosis
-stab streaking to detect beta strep that only produce streptolysin-O
-direct antigen tests for GAS
-negative result should be cultured
Routine culture setup and interpretation - Sputum, bronchial washings/aspirates, transtracheal aspirates - media
-SBA
-CHOC
-MAC
Routine culture setup and interpretation - Sputum, bronchial washings/aspirates, transtracheal aspirates - normal flora
-CNS
-non-beta hemolytic strep
-diphtheroids
-commensal Neisseria
-Haemophilus
-yeast
-ASPIRATES: none
Routine culture setup and interpretation - Sputum, bronchial washings/aspirates, transtracheal aspirates - common pathogens
-S. pneumoniae
-H. influenzae
-S. aureus
-Enterobacterales
-Pseudomonas
-M. catarrhalis
-C. albicans
Routine culture setup and interpretation - Sputum, bronchial washings/aspirates, transtracheal aspirates - diagnosis
-gram stain
-acceptable sputum:
–<10 epi cells/LPF
–>25 seg. neutrophils/LFP
-NOTE: neutropenic patients may not produce seg. neutrophils
Routine culture setup and interpretation - Urines - media
-SBA
-MAC
Use 0.01 mL or 0.001 mL calibrated loop
Routine culture setup and interpretation - Urines - normal flora
-clean catch: few skin flora
-catheterized or aspirate: NONE
Routine culture setup and interpretation - Urines - common pathogens
-E. coli
-Klebsiella
-Enterobacter
-Proteus
-Pseudomonas
-S. aureus
-S. saprophyticus
-CNS
-GBS
Routine culture setup and interpretation - Urines - diagnosis
-rapid screen for UTI: 1 or more bacteria/OI field on Gram stain of uncentrifuged urine
-low counts are significant in catheterized urines & aspirates
-3 or more organisms with none predominant = probable contamination
Routine culture setup and interpretation - Stool - media
-SBA
-MAC
-EMB
-XLD or HE
-Campy blood
-possible CIN and/or TCBS
Routine culture setup and interpretation - Stool - normal flora
-anaerobes
-Enterobacterales
-enterococci
-strep
-yeast
Routine culture setup and interpretation - Stool - common pathogens
-Salmonella
-Shigella
-Campylobacter
-diarrheagenic E. coli
-Aeromonas
-Plesiomonas
-Y. enterocolitica
Vibrio
Routine culture setup and interpretation - Stool - diagnosis
-seg. neutrophils = invasive diarrhea; e.g., Salmonella, Shigella, Campylobacter, EIEC, C. difficile
-no seg. neutrophils = enterotoxin-mediated diarrhea; e.g., ETEC, Vibrio
-RBCs with EHEC
Routine culture setup and interpretation - Genital - media
-SBA
-CHOC
-MAC
-Thayer-Martin
-add THIO & anaerobic media for tissue & aspirates
Routine culture setup and interpretation - Genital - normal flora
-Urethra: CNS, diphtheroids
-Vagina, pre-pubescent/postmenopausal: yeast, GNR, GPC
-Vagina, reproductive years: Lactobacillus, PGC
-Surgical/aspirates: NONE
Routine culture setup and interpretation - Genital - common pathogens
-N. gonorrhoeae
-C. albicans
-GBS
-S. aureus
-Surgical/aspirates: also anaerobes
Routine culture setup and interpretation - Genital - diagnosis
Gram stain
Routine culture setup and interpretation - CSF - media
-SBA
-CHOC
-MAC
-some add THIO
Routine culture setup and interpretation - CSF - normal flora
NONE
Routine culture setup and interpretation - CSF - common pathogens
-GBS (infants)
-Listeria (infants, elderly)
-H. influenzae (unimmunized children)
-N. meningitidis
-*S. pneumoniae
-GNR
Any isolate is significant.
Routine culture setup and interpretation - CSF - diagnosis
-use tube 2
-handle STAT
-DO NOT refrigerate
-use of cytocentrifuge to concentrate specimen increases sensitivity of Gram stain
-ID all isolates
Routine culture setup and interpretation - Blood - media
-most labs inoculate an aerobic & anaerobic bottle
-some use 2 aerobic bottles, no anaerobic
Routine culture setup and interpretation - Blood - normal flora
NONE
-common contaminants: CNS, Micrococcus, alpha strep, diphtheroids, Cutibacterium
Routine culture setup and interpretation - Blood - common pathogens
any isolate potentially significant
-GPC are most common
Routine culture setup and interpretation - Blood - diagnosis
-skin prep: 80-95% ethanol or isopropyl alcohol followed by povidone-iodine or tincture of iodine
-optimum volume: adult, 20 mL; child, 1 mL per year of life
-blood-to-broth ratio: 1:5 to 1:10
-usually draw 2 sets in 24 hours
-automated systems used for monitoring
-growth indicated by consumption of O2 or production of CO2
-Gram stain & subculture required for ID
Routine culture setup and interpretation - Wound - media
-SBA
-CHOC
-MAC
-surgical, aspirate, or tissue: add anerobic blood, KVLB, THIO
Routine culture setup and interpretation - Wound - normal flora
-CNS
-diphtheroids
-Cutibacterium
-surgical, aspirate, or tissue: NONE
Routine culture setup and interpretation - Wound - common pathogens
-S. aureus
-beta-hemolytic strep
-Enterobacterales
-P. aeruginosa
-surgical, aspirate, or tissue: also anaerobes
-human bite: alpha-hemolytic strep, S. aureus, S. pyogenes, Eikenella corrodens, anaerobes
Routine culture setup and interpretation - Wound - diagnosis
Gram stain
Routine culture setup and interpretation - Eye - media
-SBA
-CHOC
Routine culture setup and interpretation - Eye - normal flora
-CNS
-diphtheroids
-Cutibacterium
Routine culture setup and interpretation - Eye - common pathogens
-H. influenzae
-S. pneumoniae
-S. aureus
-Enterobacterales
-Pseudomonas
Routine culture setup and interpretation - Eye - diagnosis
-Gram stain - if POS, call
-Keratitis = EMERGENCY - loss of eye can occur
Routine culture setup and interpretation - Ear - media
-SBA
-CHOC
-MAC
Routine culture setup and interpretation - Ear - normal flora
normal skin flora
Routine culture setup and interpretation - Ear - common pathogens
-S. pneumoniae
-H. influenzae
-GAS
-M. catarrhalis
-S. aureus
-Pseudomonas
Routine culture setup and interpretation - Ear - diagnosis
Gram stain
Fecal pathogens - OXIDASE positive
-Campylobacter
-Vibrio
-Aeromonas
-Plesiomonas
Fecal pathogens - OXIDASE negative
-Escherichia coli
-Salmonella
-Shigella
-Yersinia
Major classes of antibiotics - Natural penicillins - representative antibiotics
-Penicillin V
-Penicillin G
Major classes of antibiotics - Natural penicillins - mode of action
inhibit cell wall synthesis
Major classes of antibiotics - Natural penicillins - spectrum of activity
-narrow
-GPs other than staph
-some GN
Major classes of antibiotics - Natural penicillins - characteristics
-beta-lactam
-bactericidal
-allergic reaction common side effect
Major classes of antibiotics - Synthetic penicillins - representative antibiotics
-methicillin
-oxacillin
-ampicillin
-carbenicillin
-piperacillin
Major classes of antibiotics - Synthetic penicillins - mode of action
inhibit cell wall synthesis
Major classes of antibiotics - Synthetic penicillins - spectrum of activity
-broader spectrum of activity than natural penicillins
-GPs (not MRSA) & GNs
Major classes of antibiotics - Synthetic penicillins - characteristics
-beta-lactam
-bactericidal
-penicillinase-resistant penicillins = oxacillin, methicillin, nafcillin, cloxacillin, dicloxacillin
-drug class of choice for STAPH infections
Major classes of antibiotics - Cephalosporins - representative antibiotics
-cephalexin
-cefotoxin
-ceftriaxone
-cefepime
Major classes of antibiotics - Cephalosporins - mode of action
inhibit cell wall synthesis
Major classes of antibiotics - Cephalosporins - spectrum of activity
-GPs & GNs
-each generation has broader spectrum of activity than previous
Major classes of antibiotics - Cephalosporins - characteristics
-beta-lactam
-bactericidal
Major classes of antibiotics - Carbapenems - representative antibiotics
Imipenem
Major classes of antibiotics - Carbapenems - mode of action
inhibit cell wall synthesis
Major classes of antibiotics - Carbapenems - spectrum of activity
-widest spectrum
-GPs & GNs, including P. aeruginosa & anaerobes, but NOT MRSA or VRE
Major classes of antibiotics - Carbapenems - characteristics
-beta-lactam
-bactericidal
-reserved for IV use in serious infections
Major classes of antibiotics - Monobactams - representative antibiotics
Aztreonam
Major classes of antibiotics - Monobactams - mode of action
inhibit cell wall synthesis
Major classes of antibiotics - Monobactams - spectrum of activity
-P. aeruginosa & other GNR
-low activity against GPs & anaerobes
Major classes of antibiotics - Monobactams - characteristics
-beta-lactam
-bactericidal
Major classes of antibiotics - Glycopeptides - representative antibiotics
Vancomycin
Major classes of antibiotics - Glycopeptides - mode of action
inhibit cell wall synthesis
Major classes of antibiotics - Glycopeptides - spectrum of activity
-GPs
-drug of choice for MRSA
-some strain of Enterococcus are now resistant (VRE)
Major classes of antibiotics - Glycopeptides - characteristics
-bactericidal
-used for serious infections
Major classes of antibiotics - Macrolides - representative antibiotics
-erythromycin
-clarithromycin
-azithromycin
Major classes of antibiotics - Macrolides - mode of action
inhibit RNA-dependent protein synthesis
Major classes of antibiotics - Macrolides - spectrum of activity
-GPs & some GNs
-intracellular organisms
-atypical mycobacteria
Major classes of antibiotics - Macrolides - characteristics
bacteriostatic
Major classes of antibiotics - Tetracyclines - representative antibiotics
-tetracycline
-doxycycline
Major classes of antibiotics - Tetracyclines - representative antibiotics
-tetracycline
-doxycycline
Major classes of antibiotics - Tetracyclines - mode of action
inhibit protein synthesis
Major classes of antibiotics - Tetracyclines - spectrum of activity
-GPs & GNs
-intracellular organisms
-spirochetes
-MRSA
-VRE
Major classes of antibiotics - Tetracyclines - characteristics
-bacteriostatic
-used less often than B-lactams
-NOT given to children or pregnant women due to staining of teeth, abnormal bone growth
Major classes of antibiotics - Aminoglycosides - representative antibiotics
-gentamycin
-tobramycin
-amikacin
Major classes of antibiotics - Aminoglycosides - mode of action
inhibit protein synthesis by binding irreversibly to 30S ribosomal subunit
Major classes of antibiotics - Aminoglycosides - spectrum of activity
-used primarily for GNs (including P. aeruginosa)
-ineffective against anaerobes
Major classes of antibiotics - Aminoglycosides - characteristics
-bactericidal
-toxic to kidneys & ears
-only used to treat serious GN infections
Major classes of antibiotics - Sulfonamides - representative antibiotics
-Sulfamethoxazole (SMZ)
-Trimethoprim (TMP)
Major classes of antibiotics - Sulfonamides - mode of action
inhibit folic acid synthesis
Major classes of antibiotics - Sulfonamides - spectrum of activity
broad spectrum of activity against Enterobacterales
Major classes of antibiotics - Sulfonamides - characteristics
-bacteriostatic
-used primarily for UTI
Major classes of antibiotics - Quinolones - representative antibiotics
-ciprofloxacin
-levofloxacin
-ofloxacin
Major classes of antibiotics - Quinolones - mode of action
inhibit DNA synthesis
Major classes of antibiotics - Quinolones - spectrum of activity
broad spectrum
Major classes of antibiotics - Quinolones - characteristics
-bactericidal
-used to treat serious infections
-ciprofloxacin used for anthrax
What antibiotic is used to treat anthrax?
anthrax
Major classes of antibiotics - Lincosamides - representative antibiotics
clindamycin
Major classes of antibiotics - Lincosamides - mode of action
inhibit protein synthesis
Major classes of antibiotics - Lincosamides - spectrum of activity
-GPC (including MRSA)
-anaerobes
Major classes of antibiotics - Lincosamides - spectrum of activity
-GPC (including MRSA)
-anaerobes
Major classes of antibiotics - Lincosamides - characteristics
one of the most effective antibiotics against ANAEROBES but resistance is increasing
Disk diffusion susceptibility method (Kirby Bauer) - organisms
-rapidly grow aerobes & facultative anaerobes
-NOT for slow growers, anaerobes, or fastidious organisms (except with modifications)
Disk diffusion susceptibility method (Kirby Bauer) - inoculum
-18-24 hour pure culture
-1.5 x 10^8 CFU/mL
-compare to 0.5 McFarland standard
-too heavy = smaller zones/false resistant
-too light = larger zones/false susceptible
Disk diffusion susceptibility method (Kirby Bauer) - medium
-Mueller-Hinton (MH) agar
-swab entire surface evenly to achieve solid lawn of growth
Disk diffusion susceptibility method (Kirby Bauer) - disks
-store in refrigerator or freezer in sealed, desiccated container
-warm to RT before use
-check expiration dates
-place within 15 minutes of inoculation
-no more than 12 per 150-mm plate
Disk diffusion susceptibility method (Kirby Bauer) - incubation
-within 15 minutes of disk placement
-inverted
-ambient air
-35*C for 16-18 hours
-<16 hours = increased zone, false susceptible
->18 hours = decreased zone, false resistant
EXCEPTION: MRSA may require 24 hours
Disk diffusion susceptibility method (Kirby Bauer) - modifications for fastidious bacteria
-Streptococcus: use MH supplemented with 5% sheep blood; incubate in 5-7% CO2
-Haemophilus: use Haemophilus test medium (HTM); incubate in 5-7% CO2
Disk diffusion susceptibility method (Kirby Bauer) - reading
-routine: measure zones from back side of plate using ruler or calipers
-media containing blood: read from top with lid removed
Disk diffusion susceptibility method (Kirby Bauer) - situations/actions
-sparse growth: repeat with standardized inoculum
-mixed culture: repeat with pure inoculum
-colonies within zone: subculture & retest
-slight growth in zone for TMP & sulfonamides: disregard
-swarming of Proteus into zone: ignore
Disk diffusion susceptibility method (Kirby Bauer) - reporting
resistant, intermediate, or susceptible based on zone of inhibition in mm
Disk diffusion susceptibility method (Kirby Bauer) - quality control (QC)
-test QC strains of E.coli, S.aureus, P.aeruginosa, Enterococcus faecalis for 20-30 consecutive days
-if results are acceptable, frequency may be reduced to weekly if all other guidelines are followed
Other susceptibility tests - Minimal inhibitory concentration (MIC)
-standard inoculum added to serial dilutions of antibiotics & incubated
-MIC = least amount of antibiotic (highest dilution) that prevents visible growth
-can be done in tubes, microtiter trays, or automated systems
Other susceptibility tests - Minimal bacterial concentration
-clear tubes from MIC are subcultured to agar
-MBC = concentration of antibiotic that results in 99.9% decrease in CFU per mL
Other susceptibility tests - Beta-Lactamase
-detects enzyme that cleaves beta-lactam ring, rendering penicillin & cephalosporins ineffective
-test Haemophilus, N.gonorrhoeae, Moraxella
-bacteria applied to moistened disk impregnated with cephalosporin nitrocefin (Cefinase disk)
-RED color if beta-lactam ring is broken, i.e., organism produces beta-lactamase
Other susceptibility tests - screen for penicillin susceptibility in S. pneumoniae
-test with oxacillin disk instead of penicillin disk
-more sensitive in detecting resistance
-Mueller-Hinton with 5% sheep blood inoculated with organism
-oxacillin sick (1 mcg) placed
-incubated overnight in 5-7% CO2
-zone of inhibition >=20 mm = susceptible to penicillin
-zone of inhibition <20 mm = perform MIC
Other susceptibility tests - tests for oxacillin- (methicillin-) resistant S.aureus (MRSA)
-oxacillin used as class representative for penicillinase-resistant penicillins
-organism resistant to it is resistant to all
-oxacillin screen plate: Mueller-Hinton with 4% NaCl & oxacillin (6 mcg/mL) inoculated & incubated overnight
-any growth = resistant
-not suitable for testing CNS
-CLSI recommends cefoxitin disk diffusion method for both S.aureus & CNS
Other susceptibility tests - vancomycin screen
-for detection of VRE
-brain-heart infusion agar plus 6 mcg vancomycin/mL inoculated & incubated overnight
-growth = resistance
-can also be used for * S.aureus*
Other susceptibility tests - E test
-plastic strip containing concentration gradient placed on inoculum lawn on Mueller-Hinton plate & incubated overnight
-MIC = point where border or growth inhibition intersects strip
-useful for testing fastidious organisms such as S.pneumoniae, other strep, H. influenzae, & anaerobes
Other susceptibility tests - D test (inducible clindamycin resistance)
-to detect inducible clindamycin resistance in MRSA isolated that are resistant to erythromycin & susceptible to clindamycin on initial testing
-erythromycin & clindamycin disks placed 15-26 mm apart on Mueller-Hinton agar inoculated with organism
-after overnight incubation, flattened zone between disks (D-shaped zone of inhibition aground clindamycin disk) means erythromycin induces clindamycin resistance = clindamycin reported as resistant
-similar procedure for beta-hemolytic strep except Mueller-Hinton with sheep blood used & disks placed 12 mm apart
Automated susceptibility testing - susceptibility
-broth with various dilutions of antibiotics are inoculated & incubated
-growth is determined by photometry, turbidity, or fluorescence, depending on system
Automated susceptibility testing - features
-walk-away capability
-LIS interface
-generation of institutional antibiograms
-epidemiology reportz
Automated susceptibility testing - advantages
-accuracy
-short TAT
-frees tech for other duties
Automated susceptibility testing - limitations
-only for rapidly growing organisms
-not all microorganisms are in databases
Examples of quality control in microbiology labs - autoclave - requirements
-spore test weekly (B. stearothermophilus
-must reach 121*C/15 psi
Examples of quality control in microbiology labs - balances - requirements
check for accuracy annually
Examples of quality control in microbiology labs - biosafety cabinet - requirements
check airflow annually
Examples of quality control in microbiology labs - centrifuges - requirements
check rpm every 6 months
Examples of quality control in microbiology labs - CO2 incubator - requirements
check CO2 & temperature daily
Examples of quality control in microbiology labs - gas pack - requirements
check for anaerobiosis with methylene blue strip each use (white = no O2; blue = O2)
Examples of quality control in microbiology labs - microscopes - requirements
clean & adjust 4 times per year
Examples of quality control in microbiology labs - temperatures - requirements
daily checks of incubators, heating blocks, water baths, refrigerators, freezers
Examples of quality control in microbiology labs - thermometers - requirements
must be checked against reference thermometer from National Bureau of Standards
Examples of quality control in microbiology labs - instrument logs - requirements
document routine function checks, preventive maintenance service
-maintain for life of instrument
Examples of quality control in microbiology labs - Gram stain - requirements
control slide weekly (E. coli & S.aureus)
Examples of quality control in microbiology labs - reagents - requirements
most are tested each day of use with positive & negative controls
Examples of quality control in microbiology labs - media - requirements
-most are exempt from retesting if purchased from manufacturer who follows CLSI guidelines
-obtain & retain statement of QC
-retesting required for CHOC, selective media for Neisseria & Campylobacter
Examples of quality control in microbiology labs - procedure manual - requirements
-must be reviewed & signed annually by lab director
-changes must be approved & signed by lab director
-obsolete procedures must be removed & retained for 2 years
Examples of quality control in microbiology labs - employee competency - requirements
verification on hiring & annually
Examples of quality control in microbiology labs - proficiency testing - requirements
-test unknowns exactly as patient specimens
-must maintain an average score of 80%
-document corrective action
Stool specimens for Ova & Parasites - consistency - liquid:
-max time between collection & examination?
-parasites recovered?
-30 minutes
-trophozoites (trophs), helminth eggs, larvae
Stool specimens for Ova & Parasites - consistency - semisolid:
-max time between collection & examination?
-parasites recovered?
-1 hour
-trophs, helminth eggs, larvae
Stool specimens for Ova & Parasites - consistency - formed:
-max time between collection & examination?
-parasites recovered?
-24 hours
-cysts, helminth eggs, larvae
Ova and parasite fresh stool examination - number of specimens
-1-3 for routine workup
-patients should submit 3 stool specimens, one every other day
Ova and parasite fresh stool examination - interfering substances
-antibiotics
-antiseptics
-barium
-laxatives
-mineral oil
-soap
-water
-urine
Ova and parasite fresh stool examination - preservation
-PVA
-5-10% formalin
-MIF
-SAF
Formed stools may be refrigerated for 1-2 days
Ova and parasite fresh stool examination - direct smear, saline
-on fresh liquid stools
-to observe motility of trophs
Ova and parasite fresh stool examination - direct smear, iodine
-1% D’Antoni or Lugol iodine
-to observe nuclei of cysts
-trophs will be killed
Ova and parasite fresh stool examination - concentration
to concentrate parasites & separate from fecal debris
Ova and parasite fresh stool examination - concentration - sedimentation method
-Formalin-ethyl acetate
-recovers eggs, larvae, cysts
Ova and parasite fresh stool examination - concentration - flotation method
-33% zinc sulfate
-specific gravity 1.18
-parasites float to top
-may miss operculated eggs, unfertilized Ascaris
Ova and parasite fresh stool examination - permanent stained slides
-for Dx of protozoa
-PVA fixed or fresh specimen
-iron hematoxylin or trichrome stain
Intestinal amebae - Entamoeba histolytica - nucleus
-round
-fine, even peripheral chromatin
-small, delicate, central karyosome
Intestinal amebae - Entamoeba histolytica - troph
-10-60 um, average 20 um
-1 nucleus
-delicate, finely granular cytoplasm
-ingested RBCs
-seldom contains bacteria
-single, long, finger-like pseudopod
-directional motility
Intestinal amebae - Entamoeba histolytica - cyst
-round
-10-20 um
-2-4 nuclei
-10% have cigar-shaped chromatoid bodies
-may have glycogen vacuoles
Intestinal amebae - Entamoeba histolytica - pathogenicity
-causes acute amebic dysentery
-can cause extraintestinal amebiasis
What intestinal ameba is the only ameba that ingests RBCs?
Entamoeba histolytica
Intestinal amebae - Entamoeba histolytica - diagnosis
-EIA for antigen detection
-molecular testing available
Intestinal amebae - Entamoeba hartmanni - nucleus
-round
-fine, even peripheral chromatin
-small, delicate, central karyosome
Intestinal amebae - Entamoeba hartmanni - troph
-5-12 um
-1 nucleus
-delicate, finely granular cytoplasm
-ingests bacteria
-single, long, finger-like pseudopod
-directional motility
Intestinal amebae - Entamoeba hartmanni - cyst
-round
-5-9 um
-2-4 nuclei
-10% have cigar-shaped chromatoid bodies
-may have glycogen vacuoles
Intestinal amebae - Entamoeba hartmanni - pathogenicity
non-pathogenic
Intestinal amebae - Entamoeba coli - nucleus
-coarse, irregular peripheral chromatin
-eccentric karyosome
Intestinal amebae - Entamoeba coli - troph
-15-50 um
-coarse cytoplasm with many vacuoles & ingested bacteria
-short, blunt, multiple pseudopods
-sluggish non-directional motility
Intestinal amebae - Entamoeba coli - cyst
-round
-10-35 um
-2-8 nuclei
-occasional chromatoid bodies with splintered ends
-may have glycogen vacuoles
Intestinal amebae - Entamoeba coli - pathogenicity
non-pathogenic
Intestinal amebae - Endolimax nana - nucleus
-no peripheral chromatin
-large, irregular karyosome
Intestinal amebae - Endolimax nana - troph
-2-12 um
-single nucleus
-finely granular vacuolated cytoplasm
-blunt pseudopods
-sluggish, non-progressive motility
Intestinal amebae - Endolimax nana - cyst
-5-10 um
-round to oval
-usually 4 nuclei
-no chromatoid bodies
-may have poorly defined glycogen mass
Intestinal amebae - Endolimax nana - pathogenicity
non-pathogenic
What intestinal ameba is on eof the smallest amoeba?
Endolimax nana
Intestinal amebae - Iodamoeba butschlii - nucleus
-no peripheral chromatin
-large karyosome surrounded by layer of small granules
Intestinal amebae - Iodamoeba butschlii - troph
-8-20 um
-coarsely granular cytoplasm with vacuoles & bacteria
-blunt pseudopod
-sluggishly progressive motility
Intestinal amebae - Iodamoeba butschlii - cyst
-5-20 um
-ovoid
-1 nucleus
-prominent glycogen vacuole
-“Iodine cyst”
Intestinal amebae - Iodamoeba butschlii - pathogenicity
non-pathogenic
What intestinal ameba is the only ameba with just one nucleus in cyst?
Iodamoeba butschlii
Intestinal amebae - Blastocystis hominis - nucleus
up to 4, pushed to the side
Intestinal amebae - Blastocystis hominis - troph
-round
-6-40 um
-large central body
Intestinal amebae - Blastocystis hominis - cyst
NONE
Intestinal amebae - Blastocystis hominis - pathogenicity
-uncertain
-does cause diarrhea, fever, abdominal pain, & vomiting
True or False. Blastocystis hominis should be quantitated.
True
What intestinal ameba was formerly classified as a yeast?
Blastocystis hominis
Flagellates of the intestinal and urogenital tracts - GI tract - Dientamoeba fragilis - troph
-5-15 um
-80% have 2 nuclei
-no peripheral chromatin
-karyosome is mass of 4-8 granules
Flagellates of the intestinal and urogenital tracts - GI tract - Dientamoeba fragilis - cyst
-rarely observed
-contains 2 nuclei, each with a large karyosome, in the center of the cell
Flagellates of the intestinal and urogenital tracts - GI tract - Dientamoeba fragilis - transmission
-fecal-oral
-oral-anal
Flagellates of the intestinal and urogenital tracts - GI tract - Dientamoeba fragilis - pathogenic?
Yes
Flagellates of the intestinal and urogenital tracts - GI tract - Dientamoeba fragilis - flagella
only visible with an electron microscope
Flagellates of the intestinal and urogenital tracts - GI tract - Giardia intestinalis (also known as G. lamblia or G. duodenalis) - troph
-pear-shaped
-10-20 um
-2 nuclei with large central karyosomes
-4 pairs of flagella
-anterior & ventral sucking disks
-2 axostyles
-2 median bodies
-“Old man in glasses”
-FALLING LEAF motility
Flagellates of the intestinal and urogenital tracts - GI tract - Giardia intestinalis (also known as G. lamblia or G. duodenalis) - cyst
-ovoid
-8-19 um
-thick double wall
-cytoplasm shrinks away from cell wall
-2-4 nuclei at anterior end
-median bodies & axostyles
Flagellates of the intestinal and urogenital tracts - GI tract - Giardia intestinalis (also known as G. lamblia or G. duodenalis) - transmission
ingestion of cyst in contaminated water, oral-anal, pets
Flagellates of the intestinal and urogenital tracts - GI tract - Giardia intestinalis (also known as G. lamblia or G. duodenalis) - pathogenic?
Yes
Flagellates of the intestinal and urogenital tracts - GI tract - Giardia intestinalis (also known as G. lamblia or G. duodenalis) - Enterotest
-patient swallows capsule attached to string
-string withdrawn after 4 hours and mucus is examined
-antigen detected
Flagellates of the intestinal and urogenital tracts - GI tract - Chilomastix mesnili - troph
-6-24 um
-broad anterior, tapering posterior
-3 flagella at anterior
-1 flagella posterior
-spiral groove running length of body
-prominent cytostome bordered by fibrils
-single nucleus at anterior
-stiff rotary motility
Flagellates of the intestinal and urogenital tracts - GI tract - Chilomastix mesnili - cyst
-6-10 um
-round with bulge at anterior
-single large nucleus
-hourglass-shaped cytostome & prominent fibrils
-“Lemon cyst”
Flagellates of the intestinal and urogenital tracts - GI tract - Chilomastix mesnili - transmission
ingestion of cyst
Flagellates of the intestinal and urogenital tracts - GI tract - Chilomastix mesnili - pathogenic?
No
Flagellates of the intestinal and urogenital tracts - GI tract - Pentatrichomonas hominis - troph
-6-14 um
-prominent axostyle extending through posterior
-4 anterior flagella
-undulating membrane entire length of body along costa
-1 oval nucleus with small karyosome
-rotary motion
Flagellates of the intestinal and urogenital tracts - GI tract - Pentatrichomonas hominis - cyst
NONE
Flagellates of the intestinal and urogenital tracts - GI tract - Pentatrichomonas hominis - transmission
ingestion of fecally contaminated material
Flagellates of the intestinal and urogenital tracts - GI tract - Pentatrichomonas hominis - pathogenic?
No
Flagellates of the intestinal and urogenital tracts - Urogenital tract - Trichomonas vaginalis - troph
-5-18 um
-4 anterior flagella
-undulating membrane that extends half the body
Flagellates of the intestinal and urogenital tracts - Urogenital tract - Trichomonas vaginalis - cyst
NONE
Flagellates of the intestinal and urogenital tracts - Urogenital tract - Trichomonas vaginalis - transmission
sexual
Flagellates of the intestinal and urogenital tracts - Urogenital tract - Trichomonas vaginalis - pathogenic?
Yes
What flagellate is the only flagellate in the urogenital tract?
Trichomonas vaginalis
Flagellates of the intestinal and urogenital tracts - Urogenital tract - Trichomonas vaginalis - diagnosis
-wet mount (jerky motility)
-culture
-rapid antigen tests
-PCR
Intestinal ciliates - Balantidium coli (Neobalantidium coli) - troph
-ovoid
-usually 40-50 um, but can reach 200 um
-covered with cilia
-funnel-shaped cytostome
-macronucleus & micronucleus
-vacuoles
-rapid rotary motion
Intestinal ciliates - Balantidium coli (Neobalantidium coli) - cyst
-round
-45-65 um
-thick refractile cell wall
-no cilia
Intestinal ciliates - Balantidium coli (Neobalantidium coli) - transmission
ingestion of cyst
Intestinal ciliates - Balantidium coli (Neobalantidium coli) - pathogenic?
Yes
What ciliate is the only ciliate that is pathogenic to humans?
Balantidium coli (Neobalantidium coli)
What is the largest protozoan of humans?
Balantidium coli (Neobalantidium coli)
Which intestinal ciliate is common in pigs?
Balantidium coli (Neobalantidium coli)
Intestinal sporozoans - Cystoisospora (Isospora) belli - transmission
ingestion of oocysts in fecally contaminated food or water
Intestinal sporozoans - Cystoisospora (Isospora) belli - diagnosis
-oocysts in feces
-30 x 12 um
-transparent
-stain well with iodine
-1-2 sporoblasts
Intestinal sporozoans - Cystoisospora (Isospora) belli - definitive host
human
Intestinal sporozoans - Cystoisospora (Isospora) belli - symptoms
-anorexia
-nausea
-abdominal pain
-diarrhea
-possible malabsorption
Intestinal sporozoans - Cryptosporidium parvum and Cryptosporidium hominis - transmission
-ingestion of oocysts from food or water contamination with animal feces
-oral/anal route
-direct contact with infected individual or animal
Intestinal sporozoans - Cryptosporidium parvum and Cryptosporidium hominis - diagnosis
-modified acid-fast stain of feces
-red spherical bodies 3-6 um
-4 sporozoites
-immunoassay kits
Intestinal sporozoans - Cryptosporidium parvum and Cryptosporidium hominis - fecal oocysts of both species
indistinguishable by routine microscopy
Intestinal sporozoans - Cryptosporidium parvum and Cryptosporidium hominis - symptoms
-chronic diarrhea in immunocompromised or those with AIDS
-acute self-limited diarrhea in immunocompetent
Intestinal sporozoans - Cyclospora cayetanensis - transmission
contaminated food & water
Intestinal sporozoans - Cyclospora cayetanensis - diagnosis
-oocysts in direct wet mount
-8-10 um
-variable staining with modified acid-fast stain
-autofluorescence under UV light
-bright blue at 365 nm
-mint green at 450-490 nm
-antigen-based immunoassay kits during outbreaks
-PCR
Intestinal sporozoans - Cyclospora cayetanensis - symptoms
prolonged diarrhea
Intestinal sporozoans - Microsporidia - transmission
ingestion of spores
Intestinal sporozoans - Microsporidia - diagnosis
-histology on tissue using acid-fast and periodic acid-schiff (PAS) stains
-chromotrophic stains also
True or False. Microsporidia are small obligate intracellular parasites.
True
Intestinal sporozoans - Microsporidia - symptoms
-causes prolonged diarrhea
-can disseminate
Opportunistic pathogen, mainly in AIDS patients.
Intestinal sporozoans - Microsporidia - molecular studies indicate?
related to fungi
Intestinal nematodes - Trichuris trichiura - route of infection
ingestion of infective egg
Intestinal nematodes - Trichuris trichiura - diagnostic stage
-undeveloped eggs in feces
-barrel-shaped ovum
-50 x 23 um
-brown or yellow
-clear plug at either end
Intestinal nematodes - Trichuris trichiura - also called?
Whip worm
Intestinal nematodes - Trichuris trichiura - what is required before the eggs become infective?
eggs require a developmental period in warm soil before infective
Intestinal nematodes - Trichuris trichiura - causes?
eosinophilia
Intestinal nematodes - Enterobius vermicularis - route of infection
ingestion of infective egg
Intestinal nematodes - Enterobius vermicularis - diagnostic stage
-ovoid ovum
-50 x 20 um
-1 side flattened
-colorless
-larva inside
Intestinal nematodes - Enterobius vermicularis - also called?
Pinworm
Intestinal nematodes - Enterobius vermicularis - causes?
itching when adult female migrates out of anus at night to deposit eggs
Intestinal nematodes - Enterobius vermicularis - diagnosis (tape)
cellophane tape prep taken early in the morning when the patient first wakes
Intestinal nematodes - Necator americanus - route of infection
skin penetration or ingestion of filariform larva
Intestinal nematodes - Necator americanus - diagnostic stage
-ovoid ovum
-40 x 60 um
-colorless
-contains segmented embryo 2- to 8-cell stage surrounded by clear outer zone
Intestinal nematodes - Necator americanus - also called?
New World hookworm
Intestinal nematodes - Necator americanus - causes?
-severe allergic itching can develop - “Ground itch”
-eosinophilia
-can lead to anemia
Intestinal nematodes - Necator americanus - larval migration
through lungs
Intestinal nematodes - Ancylostoma duodenale - route of infection
skin penetration or ingestion of filariform larva
Intestinal nematodes - Ancylostoma duodenale - diagnostic stage
-ovoid ovum
-40 x 60 um
-colorless
-contains segmented embryo 2- to 8-cell stage surrounded by clear outer zone
Intestinal nematodes - Ancylostoma duodenale - also called?
Old World hookworm
Intestinal nematodes - Strongyloides stercoralis - route of infection
-skin penetration by filariform larva
-sexual transmission
-autoreinfection
Intestinal nematodes - Strongyloides stercoralis - diagnostic stage
-rhabditiform larvae
-200-250 um long x 16 um in diameter
-short buccal cavity
-large bulb in esophagus
-prominent genital primordium
Intestinal nematodes - Strongyloides stercoralis - also called?
Threadworm
Intestinal nematodes - Strongyloides stercoralis - larval migration
through lungs
Intestinal nematodes - Strongyloides stercoralis - diagnosis (tests)
-duodenal aspirates and/or Enterotest
-serology (EIA)
Intestinal nematodes - Strongyloides stercoralis - must differentiate from?
hookworm larvae
Intestinal nematodes - Strongyloides stercoralis - immunocompromised patients
can disseminate & be fatal
Intestinal nematodes - Strongyloides stercoralis - causes?
eosinophilia
True or False. Strongyloides stercoralis is not infectious to laboratorians.
False
Intestinal nematodes - Ascaris lumbricoides - route of infection
ingestion of infective ovum
Intestinal nematodes - Ascaris lumbricoides - diagnostic stage
Fertilized ovum:
-ovoid
-50-75 um x 40-60 um
-yellow to brown
-granular yolk
-clear zones at either end
-may have mammillated covering or be decorticated
Nonfertilized ovum:
-larger & more elongated
-thinner shell
-no concentric clear zones
-can be mammillated or decorticated
Intestinal nematodes - Ascaris lumbricoides - also called?
Roundworm
What is the most common helminth worldwide?
Ascaris lumbricoides
Intestinal nematodes - Ascaris lumbricoides - often seen with?
Trichuris
Intestinal nematodes - Ascaris lumbricoides - requirements for egg to become infective
eggs require several weeks in soil to become infective
Intestinal nematodes - Ascaris lumbricoides - larval migration
through lungs
Intestinal nematodes - Ascaris lumbricoides - the adult resembles?
earthworms
Intestinal nematodes - Ascaris lumbricoides - may pass from?
-anus
-mouth
-nose
Intestinal nematodes - Ascaris lumbricoides - causes?
eosinophilia
Intestinal nematodes - Ascaris lumbricoides - diagnosis (test)
ELISA
Intestinal cestodes - Taenia saginata - scolex
-tetragonal
-4 cup-shaped suckers
-no hooklets
Intestinal cestodes - Taenia saginata - gravid proglottid
-longer than wide
-15-30 uterine branches per side
-irregularly alternating genital pores
Intestinal cestodes - Taenia saginata - ovum
-spherical
-35-45 um
-yellow or brown
-thick radially striated shell
Intestinal cestodes - Taenia saginata - intermediate host
cow
Intestinal cestodes - Taenia saginata - transmission
ingestion of larva in undercooked beef
Intestinal cestodes - Taenia saginata - diagnostic stage
ova in feces
Intestinal cestodes - Taenia saginata - also called?
beef tapeworm
True or False. Taenia saginata ova are infective to cattle, but not humnas.
True
Intestinal cestodes - Taenia solium - scolex
-4 cup-shaped suckers
-2 rows of hooklets around rounded rostellum
Intestinal cestodes - Taenia solium - gravid proglottid
-longer than wide
-7-13 uterine branches per side
-regularly alternating genital pores
Intestinal cestodes - Taenia solium - ovum
-spherical
-35-45 um
-yellow or brown
-thick radially striated shell
Intestinal cestodes - Taenia solium - intermediate host
pig
Intestinal cestodes - Taenia solium - transmission
ingestion of larva in undercooked pork
Intestinal cestodes - Taenia solium - diagnostic stage
ova in feces
Intestinal cestodes - Taenia solium - also called?
pork tapeworm
The ova of which intestinal cestode is infective to humans?
A. Taenia saginata
B. Diphyllobothrium latum
C. Taenia solium
D. Echinococcus granulosus
C. Taenia solium
Intestinal cestodes - Taenia solium - causes?
cysticercosis
Intestinal cestodes - Diphyllobothrium latum - scolex
-almond shaped
-lateral groove on each side
-no hooklets
Intestinal cestodes - Diphyllobothrium latum - gravid proglottid
-wider than long
-central rosette-shaped uterus
Intestinal cestodes - Diphyllobothrium latum - ovum
-ovoid
-45-70 um
-yellow-brown
-operculum
-small knob at posterior
Intestinal cestodes - Diphyllobothrium latum - intermediate host
1st: crustacean
2nd: fish
Intestinal cestodes - Diphyllobothrium latum - transmission
ingestion of larva in undercooked freshwater fish
Intestinal cestodes - Diphyllobothrium latum - diagnostic stage
ova in feces
Intestinal cestodes - Diphyllobothrium latum - also called?
Broad fish tapeworm
Intestinal cestodes - Diphyllobothrium latum - can cause?
vitamin B12 deficiency
Intestinal cestodes - Echinococcus granulosus - transmission
ingestion of fecal material from infected dog or cat
Intestinal cestodes - Echinococcus granulosus - diagnostic stage
radiologic ID of cysts in organs (liver/lungs)
-can also ID with serology
Intestinal cestodes - Echinococcus granulosus - accidental host?
humans
Intestinal cestodes - Hymenolepis nana - scolex
-diamond-shaped
-4 suckers
-single row of hooklets around short rostellum
Intestinal cestodes - Hymenolepis nana - gravid proglottid
-wider than long
-uterine branches obliterated by eggs
-3 ovoid irregularly spaced testes
Intestinal cestodes - Hymenolepis nana - ovum
-round
-40 um
-colorless
-2 distinct walls
-slight bulge at each pole of inner wall with 4-8 hair-like polar filaments
Intestinal cestodes - Hymenolepis nana - intermediate host
NONE
Intestinal cestodes - Hymenolepis nana - transmission
ingestion of eggs in feces of infected mice/rats
Intestinal cestodes - Hymenolepis nana - diagnostic stage
ova in feces
Intestinal cestodes - Hymenolepis nana - also called?
Dwarf tapeworm
Intestinal cestodes - Hymenolepis nana - adult
2.5-4 cm long
What is the most common tapeworm?
Hymenolepis nana
What is the only tapeworm without an intermediate host?
Hymenolepis nana
Trematodes - Fasciolopsis buski - route of infection
ingestion of metacercariae on aquatic plants
Trematodes - Fasciolopsis buski - location of adult
duodenum
Trematodes - Fasciolopsis buski - diagnostic stage
-ova in feces
-135 x 80 um
-yellow-brown
-thin shell
-small operculum
-granular contents evenly distributed
-clear zone between shell & yolk
Trematodes - Fasciolopsis buski - also called?
large intestinal fluke
Trematodes - Fasciolopsis buski - symptoms of infection
bowel mucosal ulcers
Trematodes - Fasciola hepatica - route of infection
ingestion of metacercariae on aquatic plants
Trematodes - Fasciola hepatica -location of adult
bile duct
Trematodes - Fasciola hepatica -diagnostic stage
Similar to F. buski:
-ova in feces
-135 x 80 um
-yellow-brown
-thin shell
-small operculum
-granular contents evenly distributed
-clear zone between shell & yolk
Trematodes - Fasciola hepatica -also called?
Sheep liver fluke
Trematodes - Clonorchis sinensis - route of infection
ingestion of metacercariae in raw, undercooked, dried, salted, or pickled fish
Trematodes - Clonorchis sinensis - location of adult
-bile ducts
-gallbladder
-pancreatic ducts
Trematodes - Clonorchis sinensis - diagnostic stage
-ova in feces
-29 x 16 um
-bulbous
-opercular shoulders
-small comma-shaped protuberance at posterior
-thick shell with tiny spines
-ciliated miracidium inside
Trematodes - Clonorchis sinensis - also called?
Chinese liver fluke
True or False. Clonorchis sinensis eggs are one of the smallest passed by humans.
True
True or False. Clonorchis sinensis eggs are one of the smallest passed by humans.
True
Trematodes - Paragonimus westermani - route of infection
ingestion of undercooked crabs or crayfish
Trematodes - Paragonimus westermani - location of adult
lungs
Trematodes - Paragonimus westermani - diagnostic stage
-ova in feces or bloody sputum
-80-120 um x 48-60 um
-yellow-brown
-thick shelled
-flattened operculum
Trematodes - Paragonimus westermani - also called?
Oriental lung fluke
Trematodes - Schistosoma mansoni - route of infection
skin penetration
Trematodes - Schistosoma mansoni - location of adults
intestinal venules
Trematodes - Schistosoma mansoni - diagnostic stage
-ova in feces
-elongated
-155 x 65 um
-pronounced lateral spine
Trematodes - Schistosoma mansoni - also called?
Blood fluke
Trematodes - Schistosoma japonicum - route of infection
skin penetration
Trematodes - Schistosoma japonicum - location of adult
intestinal venules
Trematodes - Schistosoma japonicum - diagnostic stage
-ova in feces or rectal biopsy
-ovoid
-90 x 70 um
-minute lateral spine
Trematodes - Schistosoma japonicum - also called?
Blood fluke
Trematodes - Schistosoma japonicum - diagnosis (test)
serology
Trematodes - Schistosoma haematobium - route of infection
skin penetration
Trematodes - Schistosoma haematobium - location of adult
bladder venules
Trematodes - Schistosoma haematobium - diagnostic stage
-ova in concentrated urine
-elongated
-140 x 60 um
-terminal spine
Trematodes - Schistosoma haematobium - also called?
Blood fluke
What is the only parasite of urinary system?
Schistosoma haematobium
Differentiation of Plasmodium - P. falciparum - name of disease
malignant malaria
Differentiation of Plasmodium - P. falciparum - paroxysm cycle
36-48 hours
Differentiation of Plasmodium - P. falciparum - infected RBCs
not enlarged
Differentiation of Plasmodium - P. falciparum - stages seen
-ring forms (trophs)
-gametocytes
Differentiation of Plasmodium - P. malariae - name of disease
quartan malaria
Differentiation of Plasmodium - P. malariae - paroxysm cycle
72 hours
Differentiation of Plasmodium - P. malariae - infected RBCs
not enlarged
Differentiation of Plasmodium - P. malariae - stages seen
all
Differentiation of Plasmodium - P. ovale - name of disease
ovale malaria
Differentiation of Plasmodium - P. ovale - paroxysm cycle
48 hours
Differentiation of Plasmodium - P. ovale - infected RBCs
-sometimes enlarged
-frequently oval with ragged margins
-Schuffner dots
Differentiation of Plasmodium - P. ovale - stages seen
all
Differentiation of Plasmodium - P. vivax - name of disease
tertian malaria
Differentiation of Plasmodium - P. vivax - paroxysm cycle
44-48 hours
Differentiation of Plasmodium - P. vivax - infected RBCs
-enlarged
-Schuffner dots
Differentiation of Plasmodium - P. vivax - stages seen
all
Differentiation of Plasmodium - P. falciparum - merozoites per mature schizont
not seen in peripheral blood
Differentiation of Plasmodium - P. malariae - merozoites per mature schizont
6-12
Differentiation of Plasmodium - P. ovale - merozoites per mature schizont
8-12
Differentiation of Plasmodium - P. vivax - merozoites per mature schizont
12-24
Differentiation of Plasmodium - P. falciparum - shape of gametocytes
sausage- or crescent-shaped
Differentiation of Plasmodium - P. malariae - shape of gametocytes
ovoid
Differentiation of Plasmodium - P. ovale - shape of gametocytes
round
Differentiation of Plasmodium - P. vivax - shape of gametocytes
round
Differentiation of Plasmodium - P. falciparum - multiple parasites per cell?
YES
Differentiation of Plasmodium - P. malariae - multiple parasites per cell?
NO
Differentiation of Plasmodium - P. ovale - multiple parasites per cell?
NO
Differentiation of Plasmodium - P. vivax - multiple parasites per cell?
rare
Differentiation of Plasmodium - P. falciparum - double chromatin dots?
YES
Differentiation of Plasmodium - P. falciparum - double chromatin dots?
YES
Differentiation of Plasmodium - P. malariae - double chromatin dots?
NO
Differentiation of Plasmodium - P. ovale - double chromatin dots?
NO
Differentiation of Plasmodium - P. vivax - double chromatin dots?
rare
Differentiation of Plasmodium - P. falciparum - other characteristics
-high mortality
-medical emergency
Differentiation of Plasmodium - P. malariae - other characteristics
-rarely fatal
-band-shaped trophs
-similar morphology to newly emerging P. knowlesi species - differentiate by symptoms and PCR
Differentiation of Plasmodium - P. ovale - other characteristics
-least common
-rarely fatal
-may cause relapses
Which Plasmodium species is the least common?
P. ovale
Differentiation of Plasmodium - P. vivax - other characteristics
-most common
-rarely fatal
-may cause relapses
Which Plasmodium species is the most common?
P. vivax
Blood and tissue protozoa - Acanthamoeba spp. - classification
ameba
Blood and tissue protozoa - Acanthamoeba spp. - transmission
-swimming in contaminated water
-inadequately disinfected contact lenses
Blood and tissue protozoa - Acanthamoeba spp. - diagnosis
trophozoites and cysts from brain or skin biopsy or corneal scraping
Blood and tissue protozoa - Acanthamoeba spp. - causes?
-granulomatous amebic encephalitis (GAE)
-ulcerative acanthamoeba keratitis in contact lens wearers
Usually in immunocompromised or debilitated
Blood and tissue protozoa - Naegleria fowleri - classification
ameba
Blood and tissue protozoa - Naegleria fowleri - transmission
swimming in contaminated ponds or streams
Blood and tissue protozoa - Naegleria fowleri - diagnosis
-stained smears of culture material
-trophs in CSF
Blood and tissue protozoa - Naegleria fowleri - causes?
primary amebic meningoencephalitis (PAM)
Blood and tissue protozoa - Plasmodium - classification
sporozoan
Blood and tissue protozoa - Plasmodium - transmission
Anopheles mosquito
Blood and tissue protozoa - Plasmodium - diagnosis
-Wright-stained thick & thin blood smears
-draw blood just before paroxysm
-rapid immunochromatographic dipsticks for antigen detection and fluorescent DNA/RNA stained films also used
Blood and tissue protozoa - Plasmodium - causes?
malaria
Blood and tissue protozoa - Babesia - classification
sporozoan
Blood and tissue protozoa - Babesia - transmission
-tick bite
-blood transfusion
Blood and tissue protozoa - Babesia - diagnosis
-Wright-stained thick & thin blood smears
-parasites in RBCs
-2-4 um
-trophozoites are usually pear-shaped, usually in pairs (most common) or tetrads
Blood and tissue protozoa - Babesia - symptoms resemble?
malaria
Blood and tissue protozoa - Toxoplasma gondii - classification
coccidian
Blood and tissue protozoa - Toxoplasma gondii - transmission
-ingestion of undercooked meat or oocysts from cat feces
-transplacental
-organ transplants
Blood and tissue protozoa - Toxoplasma gondii - diagnosis
-serological tests
-ELISA
-PCR
Blood and tissue protozoa - Toxoplasma gondii - definitive host
cat
Blood and tissue protozoa - Toxoplasma gondii - congenital infection
causes birth defects
Blood and tissue protozoa - Toxoplasma gondii - AIDS patients
major cause of encephalitis
Blood and tissue protozoa - Leishmania spp. complexes L. tropica (Old World), L. mexicana (New World), L. braziliensis, and L. donovani - classification
flagellate
Blood and tissue protozoa - Leishmania spp. complexes L. tropica (Old World), L. mexicana (New World), L. braziliensis, and L. donovani - transmission
sand flies
Blood and tissue protozoa - Leishmania spp. complexes L. tropica (Old World), L. mexicana (New World), L. braziliensis, and L. donovani - diagnosis
amastigote forms in WBCs & cells of the RE system
Blood and tissue protozoa - Leishmania spp. complexes L. tropica (Old World), L. mexicana (New World), L. braziliensis, and L. donovani - what type of parasite?
obligate intracellular parasite
Blood and tissue protozoa - Leishmania spp. complexes L. tropica (Old World), L. mexicana (New World), L. braziliensis, and L. donovani - causes?
Kalaazar, cutaneous & mucocutaneous leishmaniasis
Blood and tissue protozoa - Trypanosoma - classification
flagellate
Blood and tissue protozoa - Trypanosoma - transmission
-T. brucei gambiense & T. brucei rhodesiense: tsetse fly
-T. cruzi: reduviid or kissing bug
Blood and tissue protozoa - Trypanosoma - diagnosis
-T. brucei gambiense & T. brucei rhodesiense: trypomastigote in blood, lymph nodes, CSF
-T. cruzi: trypomastigote in blood; amastigote in RE cells, myocardium, CNS
Blood and tissue protozoa - Trypanosoma - T. brucei rhodesiense - causes?
East African sleeping sickness
Blood and tissue protozoa - Trypanosoma - T. brucei gambiense - causes?
West African sleeping sickness
Blood and tissue protozoa - Trypanosoma - T. cruzi - causes?
Chagas disease
-found in Southern US
Blood and tissue helminths - Toxocara - classification
nematode (in dogs/cats)
Blood and tissue helminths - Toxocara - transmission
ingestion of eggs from dog/cat feces
Blood and tissue helminths - Toxocara - diagnosis
serological tests
Blood and tissue helminths - Toxocara - accidental hosts
humans
Blood and tissue helminths - Toxocara - larvae location
tissues
Blood and tissue helminths - Toxocara - causes?
visceral & ocular larva migrams (toxocariasis)
Blood and tissue helminths - Trichinella spiralis - classification
nematode
Blood and tissue helminths - Trichinella spiralis - transmission
undercooked pork
-bear
Blood and tissue helminths - Trichinella spiralis - diagnosis
-larvae encysted in muscle
-serological tests (ELISA)
Blood and tissue helminths - Trichinella spiralis - symptoms
-eosinophilia
-edema of upper eyelids
-fever
-myalgia
Blood and tissue helminths - Wuchereria bancrofti - classification
nematode
Blood and tissue helminths - Wuchereria bancrofti - transmisson
mosquitos
Blood and tissue helminths - Wuchereria bancrofti - diagnosis
-microfilariae in blood
-Giemsa-stained thick & thin smears
Blood and tissue helminths - Wuchereria bancrofti - causes?
chronic infection causes elephantiasis (lymphatic filariasis)
Blood and tissue helminths - Brugia malayi - classification
nematode
Blood and tissue helminths - Brugia malayi - transmission
mosquitos
Blood and tissue helminths - Brugia malayi - diagnosis
-microfilariae in blood
-Giemsa-stained thick & thin smears
Blood and tissue helminths - Brugia malayi - causes?
elephantiasis
Blood and tissue helminths - Brugia malayi - periodicity
nocturnal
Blood and tissue helminths - Loa loa - classification
nematode
Blood and tissue helminths - Loa loa - transmission
Mango fly (Chrysops)
Blood and tissue helminths - Loa loa - diagnosis
-microfilariae in blood
-Giemsa-stained thick & thin smears
Blood and tissue helminths - Loa loa - also called?
African eye worm
Blood and tissue helminths - Loa loa - periodicity
nocturnal
Blood and tissue helminths - Onchocerca volvulus - classification
nematode
Blood and tissue helminths - Onchocerca volvulus - transmission
Black fly
Blood and tissue helminths - Onchocerca volvulus - diagnosis
-microfilariae from skin snips or aspirates of fibrous nodules on body
Blood and tissue helminths - Onchocerca volvulus - causes?
River blindness
Stains used in mycology - KOH - used for?
-skin
-hair
-nails
Stains used in mycology - KOH - dissolves?
keratin
Stains used in mycology - KOH - function
makes fungal elements more visible
Stains used in mycology - Calcofluor white - used for
-tissues
-sputum
-body fluids
-skin scrapings
-corneal scrapings
Stains used in mycology - Calcofluor white - type of stain
fluorescent stain, optimal fluorescence occurs with UV excitation
Stains used in mycology - Lactophenol cotton blue - used for
microscopic exam of fungal culture
Stains used in mycology - Lactophenol cotton blue - function
-lactic acid = preserves
-phenol = kills
-cotton blue = stains
Stains used in mycology - Gram stain - used for
yeast
Stains used in mycology - Gram stain - does fungi stain gram positive or gram negative?
gram positive
Stains used in mycology - Acid-fast - used for
Nocardia
(partially acid-fast)
Stains used in mycology - Colloidal carbon wet mount (India ink) - used for
CSF sediment if Cryptococcus is suspected
Stains used in mycology - Colloidal carbon wet mount (India ink) - diagnosis
halos around yeast due to wide capsule
-insensitive
-direct antigen test preferred
Stains used in mycology - Giemsa - used for
blood & bone marrow
Stains used in mycology - Giemsa -useful for?
Histoplasma
List the fungal culture media used for isolation.
- Sabouraud dextrose agar (SDA)
- SDA with antibiotics
- Brain-heart infusion agar
- Inhibitory mold agar
- Dermatophyte test medium
List the fungal culture media used for identification.
- Potato dextrose agar
- Cornmeal agar with Tween 80
- Urea agar
- Birdseed agar (niger seed or caffeic agar)
- Chromogenic agar
Fungal culture media - for isolation - Sabouraud dextrose agar (SDA) - use
-general medium
-pH 5.6 inhibits bacteria
-grows most molds & yeasts
-can also be made with glucose (SGA)
Fungal culture media - for isolation - Sabouraud dextrose agar (SDA) with antibiotics- use
-antibiotics inhibit fungal contaminants & bacteria
-dermatophytes & most fungal pathogens grow
Fungal culture media - for isolation - Brain-heart infusion agar - use
-used for the isolation of all fungi including fastidious dimorphic fungi
-10% sheep blood is added for enrichment
-antibiotics can be added to make the medium selective by inhibiting bacteria
Fungal culture media - for isolation - Inhibitory mold agar - use
-for recovery of fungi from specimens contaminated with bacteria
-contains chloramphenicol & gentamicin to inhibit bacteria
-more sensitive than SDA
Fungal culture media - for isolation - Dermatophyte test medium - use
-for recovery of dermatophytes from skin, hair, and nails
-turn agar from yellow to red
-antibiotics added to inhibit bacteria
Fungal culture media - for identification - Potato dextrose agar - use
-stimulates sporulation of molds
-good for slide cultures
Fungal culture media - for identification - Cornmeal agar with Tween 80 - use
-allows for enhanced formation of hyphae, blastospores, & chlamydoconidia, to differentiate Candida species
-C. albicans produces chlamydospores
Fungal culture media - for identification - Urea agar - use
detects urease for presumptive ID of Cryptococcus and Trichophyton
Fungal culture media - for identification - Birdseed agar (niger seed or caffeic agar) - use
-isolation of Cryptococcus species
-black-brown colonies in 4-7 days
Fungal culture media - for identification - Chromogenic agar - use
-allows rapid ID and detection
-contains chromogenic substrates hydrolyzed by species-specific enzymes
Dermatophytes - Microsporum - infects
-skin
-hair
-rarely nails
Dermatophytes - Microsporum -macroconidia
-large
-spindle or cylinder shaped
-thick walled
-multi-septate
-rough
-spiny
-borne singly on short conidiophores
Dermatophytes - Microsporum -microconidia
-few or absent
-small, club shaped
Dermatophytes - Microsporum -hair
-ectothrix hair invasion
-some species cause hair to fluoresce under UV light
Dermatophytes - Microsporum -lab ID
direct microscopic examination
Dermatophytes - Microsporum -most common species
-M. canis
-Nannizzia gypsea
-M. audouinii
Dermatophytes - Trichophyton -infects
-hair
-skin
-nails
Dermatophytes - Trichophyton -macroconidia
-rare
-pencil shaped
-multiseptate
-thin walled
-smooth
-borne singly on conidiophore
Dermatophytes - Trichophyton -microconidia
-predominant
-spherical, tear shaped, or clavate
Dermatophytes - Trichophyton -hair
-hair infections endothrix or ectothrix
-hair usually doesn’t fluoresce
Dermatophytes - Trichophyton -other characteristics
may have spirals, nodular bodies, chlamydospores, faviform mycelia
Dermatophytes - Trichophyton -T. rubrum colonies on agar
red on reverse side
Dermatophytes - Trichophyton -most common species
-T. mentagrophytes
-T. rubrum
-T. tonsurans
Which dermatophytes cause epidemic tinea capitis in children?
*T. tonsurans and M. audouinii
Dermatophytes - Epidermophyton - infects
-skin
-sometimes nails
-rarely hair
Dermatophytes - Epidermophyton - macroconidia
-club shaped
-septate
-thin walled
-smooth
-borne in singles or clusters of 2-3 per conidiophore
Dermatophytes - Epidermophyton - microconidia
absent
Dermatophytes - Epidermophyton - chlamydospores
numerous
Dermatophytes - Epidermophyton - most common species
E. floccosum is the only species
Dermatophytes - identification
-colony characteristics on SGA and microscopic morphology
-MALDI-TOF
Dimorphic fungi - Blastomyces spp. (i.e., dermatitidis) - infection
blastomycosis
Dimorphic fungi - Blastomyces spp. (i.e., dermatitidis) - mold phase
-white to gray-brown colony
-hyaline, septate hyphae with small oval conidia borne singly at tips of conidiophores
-“Lollipops”
Dimorphic fungi - Blastomyces spp. (i.e., dermatitidis) - yeast phase
-8-15 um
-round, thick walled
-single bud connected by wide neck
Dimorphic fungi - Blastomyces spp. (i.e., dermatitidis) - endemic
Ohio & Mississippi River valleys
Dimorphic fungi - Blastomyces spp. (i.e., dermatitidis) - most commonly infected
farmers - contract from soil
Dimorphic fungi - Blastomyces spp. (i.e., dermatitidis) - infection location
-begins in lungs
-may become systemic
Dimorphic fungi - Paracoccidioides spp. (i.e., brasiliensis) - infection
paracoccidioidomycosis
Dimorphic fungi - Paracoccidioides spp. (i.e., brasiliensis) - mold phase
resembles Blastomyces:
-white to gray-brown colony
-hyaline, septate hyphae with small oval conidia borne singly at tips of conidiophores
-“Lollipops”
Dimorphic fungi - Paracoccidioides spp. (i.e., brasiliensis) - yeast phase
-10-30 um
-round, double walled
-multiple buds pinched at attachment
-“Mariner’s wheel”
Dimorphic fungi - Paracoccidioides spp. (i.e., brasiliensis) - mainly found
-Brazil
-Argentina
-S. Mexico
Dimorphic fungi - Paracoccidioides spp. (i.e., brasiliensis) - infection location
-begins in lungs
-can become systemic
Dimorphic fungi - Coccidioides spp. (C. immitis and C. posadasii*) - infection
Valley fever
Dimorphic fungi - Coccidioides spp. (C. immitis and C. posadasii*) - mold phase
-fluffy or powdery white to gray-tan colonies
-barrel-shaped arthrospores
Dimorphic fungi - Coccidioides spp. (C. immitis and C. posadasii*) - yeast phase
-spherule
-20-80 um
-contains numerous endospores
Dimorphic fungi - Coccidioides spp. (C. immitis and C. posadasii*) - where is it found
California and fixed desert of Southwest US
Dimorphic fungi - Coccidioides spp. (C. immitis and C. posadasii*) - primarily infects
diagnosed more in males than females (15:1 ratio)
Dimorphic fungi - Coccidioides spp. (C. immitis and C. posadasii*) - how does it infect
-spores are inhaled or contaminate injured skin
-affects respiratory tract 1st
-can spread to other organs
Dimorphic fungi - Coccidioides spp. (C. immitis and C. posadasii*) - highly infectious
arthrospores
Dimorphic fungi - Coccidioides spp. (C. immitis and C. posadasii*) - diagnosis
serological tests
Dimorphic fungi - Histoplasma capsulatum - infection
Histoplasmosis
Dimorphic fungi - Histoplasma capsulatum - mold phase
-silky, white to gray-tan colonies
-thick-walled spherical macroconidia, 7-16 um, surrounded by finger-like projections
-“Tuberculate chlamydospores”
Dimorphic fungi - Histoplasma capsulatum - yeast phase
-1-4 um
-round to oval
-intracellular in phagocytes of blood or bone marrow
Dimorphic fungi - Histoplasma capsulatum - endemic
Ohio & mississippi River valleys
Dimorphic fungi - Histoplasma capsulatum - where does it grow
(Soil saprophyte)
-grows best in soils enriched with bird or bat droppings
Dimorphic fungi - Histoplasma capsulatum - infection location
acute pulmonary disease (esp. dangerous to immunocompromised)
-predilection for RE system
Dimorphic fungi - Sporothrix schenckii - infection
Sporotrichosis (rose gardener’s disease)
Dimorphic fungi - Sporothrix schenckii - mold phase
-white to yellow colonies
-clusters of pear-shaped conidia at tips of conidiophores
-“flowers”
Dimorphic fungi - Sporothrix schenckii - yeast phase
-gram positive
-cigar-shaped cells
-usually not seen in direct smears unless by immunofluorescence
Dimorphic fungi - Sporothrix schenckii - endemic
Mississippi & Missouri River valleys
Dimorphic fungi - Sporothrix schenckii - where does it grow
-rose bushes
-barberry bushes
-sphagnum moss
-mulch
Dimorphic fungi - Sporothrix schenckii - usually infects
farmers or florists
-introduced by trauma, usually to the hand
Dimorphic fungi - Sporothrix schenckii - cutaneous lesions
spread along lymphatics
Yeast - Candida albicans - infections
-thrush (mouth)
-vulvovaginitis
-diaper rash
-onychomycosis (nails)
-paronychomycosis (cuticles)
-endocarditis
-meningitis
-UTI
-pulmonary infections
-candidemia
Yeast - Candida albicans - important characteristics - agar type
grows on SBA, EMB (spider-like projections), SDA
Yeast - Candida albicans - important characteristics - gram stain
gram positive cells, 2-4 um
Yeast - Candida albicans - important characteristics - conidia
blastoconidia or pseudohyphae (no constrictions)
Yeast - Candida albicans - important characteristics - serum
produces germ tubes
Yeast - Candida albicans - important characteristics - cornmeal agar
produces round terminal chlamydospores
Yeast - Candida albicans - important characteristics - agar used for ID
chromogenic agar
Yeast - Candida albicans - normal flora of
-GI tract
-mucocutaneous areas
Yeast - Candida albicans - AIDS
-onychomycosis (nails)
-esophagitis
Yeast - Candida albicans - tests available for ID
-serological (antigen & antibody)
-nucleic acid tests
Yeast - Candida tropicalis - infections
-vaginitis
-UTI
-GI
-pulmonary
-systemic infections
Yeast - Candida tropicalis - cornmeal agar
blastoconidia produced randomly along pseudohyphae
Yeast - Candida tropicalis - germ tubes
may produce constricted germ tubes (true germ tubes lack constrictions)
Yeast - Candida tropicalis - usually infects
immunosuppressed
Yeast - Candida glabrata - infections
-UTI
-systemic infections
Yeast - Candida glabrata - important characteristics
-no true- or pseudomycelium
-small budding cells only
Yeast - Candida glabrata - often resistant to?
fluconazole
Which yeast is the predominant non-C. albicans cause of candidemia?
C. glabrata
Yeast - Candida krusei - infections
-endocarditis
-ocular
Yeast - Candida krusei - important characteristics
-forms true/pseudophyphae
-does not produce germ tube
Yeast - Candida krusei - resistant to?
fluconazole
Yeast - Geotrichum candidum - infections
uncommon cause of wound infections & oral thrush
Yeast - Geotrichum candidum - cornmeal agar
forms hockey stick-shaped arthroconidia
Yeast - Geotrichum candidum - blastoconidia
none
True or False. Geotrichum candidum is not actually a yeast, but rather a yeast-like organism.
True
Yeast - Cryptococcus neoformans - infections
lung infections that can disseminate to brain
Yeast - Cryptococcus neoformans - cells
-irregularly sized
-spherical
-surrounded by a capsule
Yeast - Cryptococcus neoformans - niger seed agar
maroon to brown-black colonies
Yeast - Cryptococcus neoformans - urease, phenol oxidase
positive
Yeast - Cryptococcus neoformans - found
-bird & bat droppings
-decaying vegetation
-fruit
-milk
Yeast - Cryptococcus neoformans - India Ink prep
capsule seen in about 50% of cases
Yeast - Cryptococcus neoformans - AIDS
disseminated cryptococcosis
Yeast - Malassezia furfur - infections
Tinea versicolor
Yeast - Malassezia furfur - cells
-oval or bottle-shaped budding yeast
-3-8 um in diameter
-characteristic collar between mother & daughter cells
Yeast - Malassezia furfur - skin scrapings
chains of short, slightly curved septate hyphae may be seen
Yeast - Malassezia furfur - lab ID
KOH prep of skin scrapings
Yeast - Pneumocystis jirovecii - infections
atypical interstitial plasma cell pneumonia (PCP)
Yeast - Pneumocystis jirovecii - cysts
cysts are 4-12 um spheres with intracystic bodies
Yeast - Pneumocystis jirovecii - culture
can’t be cultured
Yeast - Pneumocystis jirovecii - diagnosis
histopathological staining
Yeast - Pneumocystis jirovecii - opportunistic infection
-preterm infants
-immunocompromised
Contaminants/Opportunistic Fungi - Rhizopus - classification
mucorales
Contaminants/Opportunistic Fungi - Rhizopus - significance
-common lab contaminant
-propensity to attack vascular system of immunocompromised
-rapidly spreading
-often fatal
Contaminants/Opportunistic Fungi - Rhizopus - colonial morphology
-mature within 4 days
-“Lid lifter”
-FRONT: dense cotton candy-like growth, white at first, turning gray or yellow-brown
-REVERSE: white
Contaminants/Opportunistic Fungi - Rhizopus - microscopic morphology
-Hyphae: large, broad, nonseptate
-produces horizontal stolons that attach by rhizoids
-sporangiophores in clusters opposite rhizoids
-terminate in dark, round sporangia containing sporangiospores
Contaminants/Opportunistic Fungi - Mucor - classification
Mucorales
Contaminants/Opportunistic Fungi - Mucor - significance
-common lab contaminant
-propensity to attack vascular system of immunocompromised
-rapidly spreading
-often fatal
Contaminants/Opportunistic Fungi - Mucor - colonial morphology
-mature within 4 days
-“Lid lifter”
-FRONT: dense cotton candy-like growth, white at first, turning gray
-REVERSE: white
Contaminants/Opportunistic Fungi - Mucor - microscopic morphology
-Hyphae: large, broad, nonseptate
-produces horizontal stolons
-sporangiophores in clusters or branched
-NO rhizoids
-terminate in dark, round sporangia containing sporangiospores
Contaminants/Opportunistic Fungi - Aspergillus - classification
hyaline
Contaminants/Opportunistic Fungi - Aspergillus - most common species
A. fumigatus
Contaminants/Opportunistic Fungi - Aspergillus - significance
-common contaminant
-can cause invasive infection, colonization, toxicosis, allergy
Contaminants/Opportunistic Fungi - Aspergillus - colonial morphology
-mature within 3 days
-FRONT: fluffy, granular, or powdery texture; white at first, then color depends on species:
A. fumigatus - white to blue-green
A. niger - black
A. flavus - yellow to green
A. terreus - tan to cinnamon
-REVERSE: white, goldish, or brown
Contaminants/Opportunistic Fungi - Aspergillus - microscopic morphology
-septate hyphae, branching at 45* angle
-unbranched conidiophore arises from foot cell
-expands into large, spherical vesicle covered with phialides that produce chains of round conidia
Contaminants/Opportunistic Fungi - Acremonium - classification
hyaline mold
Contaminants/Opportunistic Fungi - Acremonium - significance
-can be a contaminant
-can cause mycetoma, corneal & nail infections
Contaminants/Opportunistic Fungi - Acremonium - colonial morphology
-mature within 5 days
-FRONT: white, spreading, moist, colorless; becomes cottony with gray top
-REVERSE: yellow or rose
Contaminants/Opportunistic Fungi - Acremonium - microscopic morphology
-small, hyaline, septate hyphae
-unbranched phialides
-oblong, 1- to 2-celled conidia in clusters at tips of phialides
Contaminants/Opportunistic Fungi - Fusarium - classification
hyaline mold
Contaminants/Opportunistic Fungi - Fusarium - significance
-can be a contaminant
-can cause eye, skin, nail, systemic infections
Contaminants/Opportunistic Fungi - Fusarium - colonial morphology
-mature within 4 days
-FRONT: white & cottony, developing a pink or violet center
-REVERSE: light
Contaminants/Opportunistic Fungi - Fusarium - microscopic morphology
-septate hyphae
-unbranched conidiophores
-large, canoe-shaped, multiseptate macroconidia
-small 1- to 2-celled oval or cylindrical conidia in singles or clusters on simple conidiophores
Contaminants/Opportunistic Fungi - Penicillium - classification
hyaline mold
Contaminants/Opportunistic Fungi - Penicillium - significance
-can be a contaminant
-can cause keratitis, external ear infections, endocarditis with artificial heart valves
Contaminants/Opportunistic Fungi - Penicillium - colonial morphology
-matures within 4 days
-FRONT: white at first; becomes powdery, blue-green with white border
-REVERSE: usually white
Contaminants/Opportunistic Fungi - Penicillium - microscopic morphology
-septate hyphae
-branched or unbranched conidiophores
-“brush-like”
-flask-shaped phialides bearing unbranched chains of round conidia
Contaminants/Opportunistic Fungi - Alternaria - classification
Dematiaceous
Contaminants/Opportunistic Fungi - Alternaria - significance
-can be contaminant
-can cause subcutaneous infection
Contaminants/Opportunistic Fungi - Alternaria - colonial morphology
-mature within 5 days
-FRONT: gray-white & wooly at first; becomes green-black or brown with light border
-REVERSE: black
Contaminants/Opportunistic Fungi - Alternaria - microscopic morphology
-dark septate hyphae
-conidiophores of variable length, sometimes branched
-large brown, drumstick-shaped conidia with transverse & longitudinal septations, in singles or chains
Contaminants/Opportunistic Fungi - Cladosporium - classification
Dematiaceous
Contaminants/Opportunistic Fungi - Cladosporium - significance
non-pathogenic
Contaminants/Opportunistic Fungi - Cladosporium - colonial morphology
-mature within 7 days
-FRONT: green-brown or black with velvety nap; becomes heaped & slightly folded
-REVERSE: black
Contaminants/Opportunistic Fungi - Cladosporium - microscopic morphology
-dark septate hyphae
-dark branching conidiophores producing 2 or more chains of oval brown conidia
Contaminants/Opportunistic Fungi - Curvularia - classification
Dematiaceous
Contaminants/Opportunistic Fungi - Curvularia - significance
-can be a contaminant
-can cause sinusitis, keratitis
Contaminants/Opportunistic Fungi - Curvularia - colonial morphology
-mature within 5 days
-FRONT: dark olive green to brown or black with pink-gray wooly surface
-REVERSE: black
Contaminants/Opportunistic Fungi - Curvularia - microscopic morphology
-dark septate hyphae
-simple or branched conidiophores, bent where conidia attach
-large, 4-celled, curved conidia
-central cell is larger & darker
Fungal pathogens by site - blood/bone marrow
-Histoplasma capsulatum
Cryptococcus neoformans
-Candida spp.
-Blastomyces dermatitidis
-Malassezia furfur
Fungal pathogens by site - CSF
-Cryptococcus neoformans
-Coccidioides spp.
-Histoplasma capsulatum
-Candida spp.
Fungal pathogens by site - hair
-Trichophyton
-Microsporum
Fungal pathogens by site - nail
-Trichophyton
-Epidermophyton
-Candida
-Aspergillus
Fungal pathogens by site - sputum, bronchial washings, transtracheal aspirates
-Candida
-Aspergillus
-Rhizopus
-Mucor
-Penicillium
-Blastomyces dermatitidis
-Coccidioides spp.
-Paracoccidioides brasiliensis
-Histoplasma capsulatum
-Sporothrix schenckii
Fungal pathogens by site - skin
-Candida
-Trichophyton
-Microsporum
-Epidermophyton
Fungal pathogens by site - throat
Candida albicans
Fungal pathogens by site - urine
-Candida
-Blastomyces dermatitidis
-Coccidioides spp.
-Histoplasma capsulatum
-Cryptococcus neoformans
Fungal pathogens by site - vaginal/cervical
Candida albicans
Viral structure
- virion
- nucleocapsid
- nucleic acid
- capsid
- envelope
Viral structure - virion
complete virus particle
Viral structure - nucleocapsid
nucleic acid & capsid
Viral structure - nucleic acid
-DNA or RNA
-single- or double-stranded
-linear or circular
Viral structure - capsid
-protein coat that encloses genetic material
-may be helical (rod-like) or icosahedral (cuboid)
-composed of protein subunits called capsomers
-protects nucleic acid
-enables virus to attach to & enter host cell
Viral structure - envelope
-outer membrane surrounding capsid in some viruses
-aids in attachment to host cell
-viruses without called naked nucleocapsids
Viral replication - adsorption
attachment of virus to host cell receptor
Viral replication - penetration
virus enters host cell by direct penetration, endocytosis (entering in a vacuole), or fusion with cell membrane
Viral replication - eclipse/synthesis
-eclipse: several hours during which virions can’t be detected
-synthesis: mRNA is produced; directs synthesis of viral particles
Viral replication - uncoating
-loss of capsid
-genome enters cytoplasm (most RNA viruses) or nucleus (most DNA viruses)
Viral replication - maturation/release
-genetic material assembled into protein coat-virions migrate to cytoplasmic membrane
-released by budding off, leaking out, or lysing host cell with enzymes
Human DNA viruses - Adenoviruses - representative viruses
-adenoviruses
->60 serotypes divided into subgroups
Human DNA viruses - Adenoviruses - infections
-mild respiratory, urinary tract, GI, & eye infections
-can cause highly contagious pink eye (conjunctivitis)
Human DNA viruses - Hepadnaviruses - representative viruses
HBV
Human DNA viruses - Hepadnaviruses - infections
Hepatitis B
Human DNA viruses - Herpes viruses - representative viruses
-Herpes simplex viruses (HSV-1, HSV-2)
-Varicella-zoster virus (VZV)
-Epstein-Barr virus (EBV)
-Cytomegalovirus(CMV)
-Human herpesviruses 6-8
Human DNA viruses - Herpes viruses - infections
-Herpes simplex viruses (HSV-1, HSV-2): oral, genital, neonatal, & ocular herpes, HSV encephalitis
-Varicella-zoster virus (VZV): Chicken pox (varicella), shingles (zoster)
-Epstein-Barr virus (EBV): infectious mononucleosis
-Cytomegalovirus(CMV): infections in newborns & immunocompromised
-Human herpesviruses 6-8: Roseola, Kaposi sarcoma
Human DNA viruses - Papillomaviruses - representative viruses
Human papilloma virus (HPV)
Human DNA viruses - Papillomaviruses - infections
warts, including genital warts that are linked to cervical cancer
Human DNA viruses - Parvoviruses - representative viruses
Parvovirus B19
Human DNA viruses - Parvoviruses - infections
Fifth disease (erythema infectiosum)
Human DNA viruses - Poxviruses - representative viruses
Variola
Human DNA viruses - Poxviruses -infections
Smallpox
Human RNA viruses - Arenaviruses - representative viruses
-Lymphocyte choriomeningitis virus (LCM)
-Lassa fever virus
Human RNA viruses - Arenaviruses - infections
-LCM: aseptic meningitis or meningoencephalitis
-Lassa fever virus: Lassa fever
Human RNA viruses - Astroviruses - representative viruses
Astrovirus
Human RNA viruses - Astroviruses - infections
gastroenteritis in children, elderly, and immunocompromised
Human RNA viruses - Hantaviridae - representative viruses
Hantavirus (Sin Nombre virus)
Human RNA viruses - Hantaviridae - infections
Hantavirus pulmonary syndrome (HPS)
Human RNA viruses - Caliciviruses - representative viruses
Noroviruses
Human RNA viruses - Caliciviruses - infections
most common cause of infectious gastroenteritis in the US
Human RNA viruses - Coronaviruses - representative viruses
Coronavirus
Human RNA viruses - Coronaviruses - infections
-severe acute respiratory syndrome (SARS)
-cold-like infections
-pediatric diarrhea
-COVID-19
Human RNA viruses - Filoviruses - representative viruses
-Marburg
-Ebola
Human RNA viruses - Filoviruses - infections
hemorrhagic fever
Human RNA viruses - Filoviruses - infections
hemorrhagic fever
Human RNA viruses - Flaviviruses - representative viruses
-Yellow fever virus
-Japanese encephalitis virus
-dengue virus
-West Nile virus
-Zika virus
(Note: above viruses are arboviruses - arthropod-borne viruses)
-Hepatitis C virus (HCV)
Human RNA viruses - Flaviviruses - infections
-Yellow fever virus: yellow fever
-Japanese encephalitis virus: Japanese encephalitis
-dengue virus: dengue fever
-West Nile virus: West Nile virus infection
-Zika virus: Zika
(Note: above viruses are arboviruses - arthropod-borne viruses)
-Hepatitis C virus (HCV): Hepatitis C
Human RNA viruses - Orthomyxoviruses - representative viruses
Influenzae A, B, & C
Human RNA viruses - Orthomyxoviruses - infections
Influenzae
Human RNA viruses - Paramyxoviruses - representative viruses
-Measles virus
-Mumps virus
-Parainfluenza virus
-Respiratory syncytial virus (RSV)
-Human metapneumovirus (HMPV)
Human RNA viruses - Paramyxoviruses - infections
-Measles virus: measles (rubeola)
-Mumps virus: mumps
-Parainfluenza virus: RTI in children
-Respiratory syncytial virus (RSV): RTI in infants, elderly, immunocompromised
-Human metapneumovirus (HMPV): RTI
Human RNA viruses - Picornaviruses - representative viruses
-Enteroviruses (polioviruses, coxsackieviruses A & B, echoviruses, enteroviruses)
-Hepatitis A virus (HAV)
-Rhinovirus
Human RNA viruses - Picornaviruses - infections
-Enteroviruses (polioviruses, coxsackieviruses A & B, echoviruses, enteroviruses): Polio, hand-foot-mouth disease, aseptic meningitis, others
-Hepatitis A virus (HAV): Hepatitis A
-Rhinovirus: common cold
Human RNA viruses - Reoviruses - representative viruses
Rotavirus
Human RNA viruses - Reoviruses - infections
Rotavirus: most common cause of gastroenteritis in infants & children
Human RNA viruses - Retroviruses - representative viruses
-HIV-1, HIV-2
-Human T-lymphotropic viruses (HTLV-1, HTLV-2)
Human RNA viruses - Retroviruses - infections
-HIV-1, HIV-2: AIDS
-Human T-lymphotropic viruses (HTLV-1, HTLV-2): T-cell leukemia & lymphoma, tropical spastic paraparesis
Human RNA viruses - Rhabdoviruses - representative viruses
Rabies virus
Human RNA viruses - Rhabdoviruses - infections
Rabies virus: rabies
Human RNA viruses - Togaviruses - representative viruses
-Rubella virus
-Eastern, Western, & Venezuelan equine encephalitis viruses
Human RNA viruses - Togaviruses - infections
-Rubella virus: rubella (German measles)
-Eastern, Western, & Venezuelan equine encephalitis viruses: Eastern, Western, & Venezuelan encephalitis
Common viruses by site - CNS - specimens
-CSF
-throat swab
-stool
-brain tissue
-blood
Common viruses by site - CNS - common viruses
-Enteroviruses
-HSV
-arboviruses
Common viruses by site - Eye - specimens
-conjunctival swab
-corneal scraping
Common viruses by site - Eye - common viruses
-HSV
-adenoviruses
Common viruses by site - Genital tract - specimens
-genital swab
-vesicle swab or fluid
-lesion biopsy
Common viruses by site - Genital tract - common viruses
-HSV
-HPV
Common viruses by site - GI tract - specimens
-stool
-rectal swab
Common viruses by site - GI tract - common viruses
Adults: noroviruses, adenoviruses, enteroviruses
Infants/children: rotavirus, adenoviruses
Common viruses by site - Respiratory tract - specimens
-nasal aspirate
-throat swab
-nasopharyngeal swab
-bronchoalveolar lavage
-lung biopsy
Common viruses by site - Respiratory tract - common viruses
-Influenzae A & B
-parainfluenza virus
-adenoviruses
-RSV
-HMPV
-rhinovirus
-enteroviruses
-coronavirus
Common viruses by site - Skin - specimens
vesicle fluid or scrapings
Common viruses by site - Skin - common viruses
-HSV
-VZV
-measles
-rubella
-enterovirus
-parvovirus B19
Common viruses by site - Skin - common viruses
-HSV
-VZV
-measles
-rubella
-enterovirus
-parvovirus B19
Common viruses by site - Urinary tract - specimens
urine
Common viruses by site - Urinary tract - common viruses
-adenoviruses
-HSV
-CMV
Viral specimen collection and transport - time of collection
during acute phase (1st 3-5 days)
Viral specimen collection and transport - site of collection
site of infection, entry & exit sites
Viral specimen collection and transport - collection containers
sterile, leak-proof, nonbreakable
Viral specimen collection and transport - swabs
-dacron
-rayon
-other polyester tips
-plastic or aluminum shafts
-calcium alginate, cotton, wood are inhibitory for some viruses
Viral specimen collection and transport - transport media
-VTM
-Amies
-Stuart transport media
(NOT required for blood, CSF, or urine)
Viral specimen collection and transport - transport
-deliver immediately
-if not possible, keep at 2-8*C & deliver within 2 hours
-EXCEPTION: keep whole blood at room temperature
Viral specimen collection and transport - storage
-best to process upon arrival
-if not possible, hold at 2-8C for up to 48 hours
->48 hours, freeze at -70C (not recommended)
Methods for diagnosis of viral infections - cytology/histology
microscopic examination of specimen for viral cytopathic effect (CPE)
Methods for diagnosis of viral infections - electron microscopy
-rarely used
-labor intensive, expensive
Methods for diagnosis of viral infections - direct fluorescent antibody stain
-fluorescent-labeled antibody added to patient cells fixed to slide
-if viral antigen present, antibody binds
-fluorescence seen with fluorescent microscope
Methods for diagnosis of viral infections - antigen detection
solid-phase & membrane ELISAs
Methods for diagnosis of viral infections - shell vial culture
-rapid modification of conventional cell culture
-detection in 1-2 days
-specimen centrifuged onto monolayer of cells growing on coverslip
-coverslips stained with viral-specific immunofluorescent conjugate
-used primarily by reference labs
Methods for diagnosis of viral infections - molecular methods
-PCR
-real-time PCR
-branched DNA
-nucleic acid hybridization
-faster & more sensitive than cell culture
-can detect multiple viruses simultaneously
Methods for diagnosis of viral infections - serology
-detects antibodies in serum
-presence of antibodies isn’t always indicative of current infection
-useful in evaluating immune status or diagnosing
-alternatively, can detect antigen from swabbed site
Which of the following specimen collection scenarios would be cause for rejection?
A. use of JEMBEC plate for Neisseria gonorrhoeae
B. the use of calcium alginate swab for Chlamydia
C. collection tubes with boric acid for urine culture
D. viral swab collected during acute infection
B. the use of calcium alginate swab for Chlamydia
Select the media of choice for culturing fastidious organisms such as Haemophilus & Neisseria.
A. MAC agar
B. Hektoen agar
C. CHOC agar
D. Eosin methylene blue agar
C. CHOC agar
Xylose lysine deoxycholate (XLD) agar is used for the recovery of which of the following organisms?
A. *Staphylococcus spp.
B. Yeast
C. Salmonella & Shigella
D. Clostridium difficile
C. Salmonella & Shigella
Which nonfermenting GNR is most often associated with cystic fibrosis?
A. Pseudomonas aeruginosa
B. Morganella morganii
C. Helicobacter pylori
D. Yersinia pestis
A. Pseudomonas aeruginosa
Which of the following organisms is both motile and produces urease?
A. Streptococcus spp.
B. Proteus vulgaris
C. Serratia marcescens
D. Francisella
B. Proteus vulgaris
Which of the following Haemophilus spp. requires X-factor?
A. Haemophilus parainfluenzae
B. Haemophilus parahaemolyticus
C. Haemophilus influenzae
D. All of the above
C. Haemophilus influenzae
Which of the following tests is used to differentiate micrococci from staphylococci?
A. modified oxidase (microdase)
B. catalase
C. Voges-Proskauer (VP)
D. Gram stain
A. modified oxidase (microdase)
Which antibiotic is used to screen for penicillin susceptibility in S. pneumoniae?
A. ampicillin
B. imipenem
C. tetracycline
D. oxacillin
D. oxacillin
Which of the following flagellates is sexually transmitted and recovered from the urogenital tract?
A. Chilomastix mesnili
B. Giardia
C. Trichomonas vaginalis
D. Pentatrichomonas hominis
C. Trichomonas vaginalis
KOH is used for the examination of fungal elements from which of the following specimens?
A. blood
B. skin and nails
C. sputum
D. bone marrow
B. skin and nails