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CP Board Review - Microbiology > Bacteriology > Flashcards

Bacteriology Flashcards

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1
Q

Fastidious Gram negative rods

A

 Haemophilus influenza cause of CNS, pulmonary, eye, ear infections

 Growth factor requirement (X = hemin and V= NAD)
 Growth on choc agar not BAP, requires high level C02
 15 – 20% resistance to Ampicillin by beta lactamase production
 H. parainfluenza – requires V, usually NF

 H. aphrophilus- does not require X or V factor, cause of abscesses (liver, lung, brain) & endocarditis
 H. ducreyi – requires X factor (Chancroid - venereal disease)

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2
Q

Listeria monocytogenes

A

Listeria monocytogenes – small gram positive rod

catalase positive

beta hemolytic colony

intracellular pathogen in macrophages

tumbling motility

more motile at 25*C than 35*C

cold loving – grows well at 4*C can use to enrich cultures

source of infection = dairy products, deli case foods, can be carried in feces,

pathogen of pregnant – can cause stillbirths or immune suppressed (CNS and sepsis)

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3
Q

Glucose Fermenters/Oxidase +

A

Vibrio cholerae

 Rice water stools – mucus flecks in liquid stool

 Toxin – receptor on epithelial cell –activates adenylate cyclase – increases cAMP – hyper secretion of NaCl and H20

 Halophilic – salt loving , 1% salt enhances growth

 Alkaline peptone water enhancement

 Selective media – TCBS = thio citrate bile sucrose agar, turns yellow due to sucrose fermentation

 01 most virulent – classic & El Tor – toxin +

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4
Q

Selective and differentiation media for salmonella

A

Salmonella Shigella Agar -Salmonella and Shigella are colorless

Hektoen agar – Salmonella produces H2S on media - black colored

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5
Q

Beta hemolytic Streptococcus

A

Grouping of Streptococcus using the “C” carbohydrate in the cell wall of the bacteria

 Latex agglutination - Lancefield grouping system defining A,B,C,F, and G, the human Strep

 Strep pyogenes – Group A beta Streptococcus

 Bacitracin –susceptible, inhibited (zone ng @ disk)

 SXT - resistant (Bactrim)

 PYR – positive (pyrrolidonyl arylmidase)

 No resistance to Penicillin – drug of choice

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6
Q

Clostridium species

A

 Gram positive bacilli (boxcar shaped) with spores
 Clostridium perfringens –

 double zone of beta hemolysis
 predominant gram positive anaerobic pathogen found in intestine
 reverse camp test +

 C. botulinum –

 food borne toxin ingestion in adults
 spore ingestion in small children
 toxin causes muscles to go flaccid

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7
Q

Catalase Positive

A

Staphylococcus spp.

Micrococcus spp.

Bacillus spp.

Listeria monocytogenes

Corynebacterium spp.

Yersinia pestis

Anaerobic non-spore form Gram positive bacilli

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8
Q

Pasteurella multocida

A

Cat and Dog bites/NF in animal’s mouth
 Small gram negative coccobacilli
 Grows on blood / not MacConkey agar
 Sensitive to penicillin / Oxidase positive
 Other dog bite organism– Capnocytophaga canimorsus – very pleomorphic gram negative rod

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9
Q

Facultative anaerobes

A

grow in aerobic and anaerobic conditions, most bacteria are facultative

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10
Q

Yersinia pestis - Plague

A

Possible organism of bioterrorism

 Obligate flea rodent flea cycle

 Flea bite leads to Bubonic form with painful buboes (lymph node swelling)

 Pneumonic form- bacteremic spread or patient to patient fatality >=50%

 Southwestern part of USA

 Grows on BAP, catalase +, oxidase -

 Bipolar staining “safety pin” gram negative

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11
Q

Aerotolerant anaerobes

A

anaerobes that are not killed by exposure to oxygen (clostridium tertium)

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12
Q

Staphylococcus aureus

A

Virulence factors – Protein A, capsular polysaccharides,

enzymes (coagulase), toxins, and hemolysins

 Diseases:

 toxic shock syndrome (TSST-1)

 scalded skin syndrome (Exfoliatin (SSS)

 soft tissue infection (Panton valentine leucocidin – PVL)

 food poisoning (Enterotoxins)

 bacteremia and endocarditis

 Furazolidone susceptible (Microcossus resistant)

 Unique susceptibility issues:

 MRSA (Methicillin resistant Staph aureus)

 Penicillin binding protein (PBP) produced by mec A gene codes for resistance to oxacillin

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13
Q

Oxidase Positive

A

Neisseria spp

Moraxella spp

Pseudomonas spp

Aeromonas spp

Helicobacter pylori

Campylobacter jejuni

Vibrio cholerae

Plesiomonas spp

Burkholderia cepacia

Achromobacter

Alkaligenes

Brucella spp.

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14
Q

Spirochetes

A

 Borrelia burgdorferi - Lyme’s disease

 tick vector (Ixodes)

 Borrelia recurrentis - relapsing fever - human body louse
 Leptospira interrogans - Leptospirosis, rats and other animals, water association
 Treponema pallidum – syphilis

 RPR
 VDRL

 Serologic or molecular diagnosis

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15
Q

Culture Media

A

Agar media –

Blood agar- 5% sheep’s blood agar - hemolysis

Chocolate agar – “cooked” blood agar – enriched

MacConkey agar – gram negative bacilli – fermentation of lactose

Concepts of Selective and Differential media –

Selective – compound/antibiotic added to media to select for a particular organism.

PEA – Phenylethyl alcohol – selects for gram positive cocci (obligate anaerobes)

Differential – compound added to media to differentiate organisms based on color.

ChromAgar = chromogenic substrates

Differential and Selective = MacConkey agar selects for gram negative bacilli and differentiates lactose fermenters.

Tubes of broth are used to detect low#’s of bacteria that might not grow on agar media – sterile body fluids

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16
Q

Catalase Enzyme Reaction

A

Hydrogen Peroxide plus bacteria

Positive if you see bubbles

Avoid blood agar – blood has innate catalase activity

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17
Q

Clostridium continued

A

 Clostridium tetani – tennis racket looking organism due to spore at the end. Toxin enters due to penetrating skin injury.
 C. septicum – organism in the blood associated with cancer.
 C. difficile – Produces enterotoxin A and Cytotoxin B, Glutamate dehydrogenase antigen

 Can detect B with cell culture and
 A and B with EIA or latex agglutination –
 cause of antibiotic associated colitis – post antibiotic therapy

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18
Q

Campylobacter

A

 Small curved bacilli – shaped like sea gull wings
 C. jejuni – agent of diarrhea

 Related to undercooked poultry ingestion
 requires selective media containing antibiotics -Skirrow’s blood agar
 42*C in microaerophilic atmosphere
 Significant % Guillain barre syndrome as sequelae

 Only Campylobacter spp with hippurate hydrolysis

C fetus – blood culture pathogen in the immune suppressed host

C. jejuni – grows at 37*C and 42*C
C. fetus - grows at 37*C and 25*C

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19
Q

Other Corynebacterium spp

A

Corynebacterium jeikeium –

 patients with plastic catheters and indwelling devices,

 normal skin flora (lipophilic)

 Very resistant to most antibiotics

 Susceptible to vancomycin and tetracycline

 Corynebacterium urealyticum –

 Rapidly urease positive diphtheroid found in urine cultures

 alkaline encrusted cystitis

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20
Q

Moraxella catarrhalis

A

 Gram negatibve dipplococci

Pneumonia, eye, sinus, otitis media

 Direct gram stain of sputum can be helpful in diagnosing pneumonia

 Polys and gram negative diplococci

 Hockey puck colony oxidase positive

 DN’ase enzyme positive

 Resistant to ampicillin by beta lactamase enzyme production

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21
Q

Shigella

A

Diarrhea, +/-vomiting, fluid loss, blood in stool

 Human to human transmission

 Low #’s of organisms to make you ill – 10 – 100 org

 Non motile and No H2S produced (differ from Salmonella)

 Non lactose fermenter

 4 species based on somatic antigen

 S. boydii Group C

 S. dysenteriae Group A

 S. flexneri Group B

 S. sonnei Group D

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22
Q

Salmonella typhi

A

Typhoid fever – sepsis and fever

 Vi capsular antigen and D somatic antigen

 Can boil solution of organism for 15 minutes to destroy the VI and expose the somatic D antigen

 Moustache of H2S in the TSI tube

 Carrier state in gallbladder

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23
Q

Alpha hemolytic Streptococcus - The anginosis group

A

The anginosis group

 S. anginosus S. constellatus S. intermedius

 Human normal flora in mouth

 More virulent than “normal” viridans Strep perhaps due to capsule

 Cause deep tissue abscesses, bacteremia, endocarditis, intra abdominal infections…

 Variable susceptibilities

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24
Q

Brucella

A

 Very small gram negative coccobacilli
 Castaneda biphasic blood culture historically used for culture – hold 14-21 day – now use BACTEC automated system with 5 days of incubation
 Specimens: blood and bone marrow
 Disease – Fever of unknown origin, joint pain
 Species related to animal spp exposure

 B. abortus – raw cow milk
 B. melitensis – raw goat milk, feta cheese
 B. suis – pigs B. canis - dogs

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25
Q

Bacterial Stains

A
  1. Gram stain –

Gram negative (red) and positive (blue) – describe morphology

— Crystal violet – primary stain

— Gram’s iodine – mordant -

– Acetone/Alcohol – decolorizer*

— Safranin – counterstain 

How to judge quality of a gram stain- are the polys blue? If so, slide is under-decolorized.

 Are the polys washed out? If so, the slide is overdecolorized

 Poor quality stains must be repeated

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26
Q

Yersinia enterocolitica

A

Cause of diarrhea

 Major reservoir – swine

 Human usually infected by non pasteurized milk

 Septicemia in iron overload syndromes

 Mesenteric adenitis – RLQ pain mimics apy

 Grows well at 4*C (like Listeria)

 CIN agar (Cefsulodin-irgasan-novobiocin)

 Has been associated with banked blood

infections – Transfusion related infection

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27
Q

Bacillus species

A

Gram + bacillus

Bacillus species –

boxcar shaped gram positive rods

catalase enzyme +

spores

B. Anthracis cause of Anthrax

Infection of herbivores

bioterrorism - due to highly resistant spores easily disseminated into the environment

Infections – skin, pulmonary and GI

black eschar skin lesions

Culture:

medusa head colonies on BAP, non-hemolytic, non-motile, Pen SS

B. cereus – food poisoning rapid onset (1 – 6 hr)

(cereulide = emetic exotoxin)

Fried rice, beta hemolytic and motile

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28
Q

Criteria for rejected sputum

A

Expectorated sputum specimens are rejected for bacterial culture based on this criteria:

 Cells observed on 10X objective (low power field)

 >= 25 epithelial cells /field

 Sputum is judged to be spit / not sputum

 This is not an acceptable specimen for bacterial culture

 Can accept for AFB , fungus, etc.

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29
Q

Coagulase negative Staph

A

@ 15 species in humans

 Staph epidermidis –

 major skin normal flora,

 major cause of subacute bacterial endocarditis.

 Pathogenicity from cell adhesion factors forming biofilms on biologics and plastic

 Staph saprophyticus –

 urinary tract infections in the child bearing age female,

 this species adheres in greater #’s to epithelial cells than other SCNG.

 Novobiocin resistant by KB disk test

 Staph hemolyticus –

 line related sepsis,

 this CNS is hemolytic on blood agar, do not confuse with Staph aureus (which is coagulase positive)

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30
Q

Actinomyces

A

 Branching gram positive bacilli that do not form spores, capable of forming sulfur granules in tissue – often found on normal tonsil

 Actinomyces israelii – associated with oral, thoracic, and abdominal infections, IUD infections.

 Bread crumb colonies in broth, molar tooth colony on agar plates.

 Penicillin susceptible.

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31
Q

Indole positive

A

E. coli

Klebsiella oxytoca (pneumoniiae is negative)

Citrobacter koseri (freundii is negative)

Plesiomonas shigelloides

most Aeromonas spp

Proteus vulgaris

Pasteurella spp

Cardiobacterium spp.

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32
Q

Staphylococcus

A

Gram positive cocci in clusters

Positive for Catalase Enzyme

Two main groups: Staphylococcus aureus (coagulase +) AND Coagulase Negative Staph (S. epidermidis, S. saprophyticus, S. hemolyticus)

Coagulase test = Rabbit plasma + organism incubated at

35*C and checked at 4 hr and 24 hr

33
Q

Anaerobic Bacteria

A

 Bacteroides fragilis group –

 growth in the presence or bile,
 esculin positive,
 main organism in human bowel,
 pleomorphic gram negative rod
 B. fragilis B. ovatus
 B. thetaiotamicron – indole positive
 B. uniformis
 B. vulgatus

34
Q

Neisseria gonorrhoeae

A

Gram - diplococci

 Acute urethritis, endocervix, ocular, rectal, oropharynx

 10 – 20 % female ascend to PID 0.5% disseminate

 Direct Gram stain useful for males

 Transport important – charcoal swabs

 Amplification methods increases detection

 PPNG = treat with ceftriaxone or quinolones

35
Q

Glucose non-fermenter/oxidase +

A

Psuedomonas aeruginosa

 fluorescent pigment and blue green pigment (pyocyanin)
 Grape like odor
 Growth at 42*C (Ps fluorescens/putida – no growth at 42*)
 Major pathogen in cystic fibrosis – in combination with Burkholderia cepacia can cause major lung damage
 Nosocomial pathogen – associate with water

36
Q

Coagulase Test

A

Negative test means no clot

Must check at 4 hours and 24 hours

If positive at 4 hours, no need to look at it again in 24 hours

Can become negative after initial positive at 4 hours because the isolate produces fibrinolysin later which dissolves the clot. This is why it is important to look at it at 4 hours.

37
Q

Other glucose non fermenters

A

 Burkholderia cepacia

 Dry , yellow colony , oxidase negative
 Problem organism in cystic fibrosis

 Alkaligenes species

 sweet fruity odor
 Nosocomial / environment

 Flavobacterium (Chryseobacterium)

 F. meningosepticum is associated with fatal septicemia in the neonate

38
Q

Capnocytophaga

A

Fusiform shaped gram negative rods – very pleomorphic
 Oxidase negative, Catalase negative
 Gliding motility, fingerlike projections from colonies
 C. canimorsus – dog bites and bacteremia
 Other Capnocytophyaga spp in the human mouth cause bacteremia in cancer patients on chemotherapy

39
Q

Streptococcus pyogenes - Virulence factors and Dz

A

Virulence factors

 M protein – resistance to phagocytosis

 Capsule – hyaluronic acid – resists complement dependent killing

 Streptolysin O and Streptolysin S – cell toxins O is oxygen labile S is oxygen stable

 Streptococcal pyrogenic exotoxins

 Diseases –

 Pharyngitis Impetigo Erysipelas

 Cellulitis Puerperal sepsis Toxic Shock

 Sequelae: Rheumatic fever and Glomerulonephritis

40
Q

Propionibacterium acnes

A

 Anaerobic diphtheroid – pleomorphic gram positive rod, does not branch
 Can be pathogen in cerebral shunt infections – can cause shunt nephritis

41
Q

Growth phases

A

Lag Phase - slowing down- not good for biochemical or susceptibility testing, > 24 hours on agar plate

Exponential or Log phase - good for all testing, usually 16-24 hr on agar

Stationary phase - good for transporting specimens, ie. Boric acid in urine for culture

42
Q

Helicobacter pylori

A

 Small curved bacilli
 Cause of acute gastritis
 Rapidly!! And strongly urease positive – this test is used for identification from antral biopsy tissue
 Difficult to grow
 Stool antigen and serum antibody can aid in diagnosis and avoid biopsy

43
Q

Triple Sugar Iron Agar

A

detect fermentation of glucose, lactose and Or Sucrose and the production of hydrogen sulfide

44
Q

Erysipelothrix rhusiopathiae

A

catalase negative, gram + rods

alpha hemolytic colony

only G+R that produces H2S (TSI)

Skin infection acquired from swine - erysipeloid

Isolated in blood cultures – strongly associated with endocarditis in drug addicts - extensive damage to valve

45
Q

Streptococcus agalactiae

A

Group B - Beta Hemolytic (faintly)

Gram positive cocci in short chains

Catalase negative

Camp test positive – Staph aureus strain with camp factor perpendicular to group B Strep – intensifies toxin production of group B Strep (old don’t use much)

 Bacitracin resistant

 Rapid hippurate hydrolysis (4 hr) = positive

 Serology to demonstrate group B carbohydrate

 Pathogen of neonate – assoc with in utero or perinatal organism acquisition during birth (early onset – 7 days) or late (7 – 28 days) from birth process. Pregnant women screened at 35 – 37 weeks using enrichment methods for GBS.

 Pathogen of the elderly – bacteremia, urinary tract , etc.

 GBS is susceptible to Penicillin.

46
Q

Streptococci

A

Gram positive cocci in chains and or pairs

Catalase enzyme negative (important! for differentiating from Staph)

 Identified by hemolytic pattern on sheep’s blood agar

 Alpha – greening of agar, partial hemolysis of rbc

 Viridans Strep, Strep pneumoniae, Abiotrophia

 Beta – clearing of agar, complete hemolysis of rbc

 Beta hemolytic Strep groups A - G

 Gamma – no clearing of agar

 Enterococci and Streptococcus Group D

47
Q

More Enteric gram negative rods

A

Non lactose fermenters – clear on MAC

 Proteus – swarming colonies

 Indole positive – P. vulgaris

 Indole negative – P. mirabilis

 Serratia marcescens – has red pigment/ infection in immune suppressed

48
Q

Microaerophilic

A

require increased CO2 and reduced oxygen to grow

49
Q

Legionella

A

 More than 30 species, L. pneumophila most important
 Requires cysteine for growth – media of choice “Buffered Charcoal Yeast Extract agar”
 Does not gram stain in direct specimens, use silver impregnation stains in tissue
 Pulmonary disease associated with water, cooling towers, shower heads, etc.
 Urinary antigen test to detect L. pneumophila type I infection only
 Treatment: Erythromycin

50
Q

HACEK group

A

 Oral flora – pathogens of endocarditis, can require 2-4 days to grow in blood cultures
 Haemophilus aphrophilus = oxidase neg, catalase neg
 Actinobacillus actinomycetom-comitans = oxidase neg, catalase pos
 Cardiobacterium hominis = oxidase pos
 Eikinella corrodens = oxidase pos, pits BAP
 Kingella kingii = oxidase pos, hemolytic on BAP

51
Q

Corynebacterium species

A

Gram positive bacilli

Chinese letter arrangement

Corynebacterium species

 Catalase +,

 diphtheroid morphology,

 no spores

 C. diphtheriae – cause of Diphtheria

 Disease is caused by a phage mediated toxin

 Detected by Elek immunoprecipitation procedure

 Diphtheritic pseudo membrane adherent in throat

 Culture

 Cysteine tellurite agar (modified Tinsdale) for isolation –

 black colonies with brown halos

 Grow on egg containing Loeffler slant then stain with methylene blue to look for metachromatic granules

52
Q

Gram negative Bacilli

A

Enterobacteriaceae

 Glucose fermented,

 Oxidase = negative

 Nitrate is reduced to nitrite

 Lactose fermentation on MacConkey Agar

 1. E.coli – Lactose positive and indole positive (green sheen on EMB agar)*

 2. Klebsiella pneumoniae – mucoid colony /currant jelly sputum*

 3. Enterobacter

53
Q

Bacteria without cell walls

A

 Mycoplasma and Ureaplasma – have cell membrane only!

 Media and transport must contain sterols to protect the membrane.

 Do not form discreet colonies – read plates under microscope
 M. pneumoniae –

 community acquired pneumonia
 PPLO = pleuropneumonia-like organism

 Genital mycoplasmas

 M. hominis – fried egg colony, vaginitis, cervicitis, postpartum sepsis, neonatal infections , pre rupture of membranes
 U. urealyticum – rapid urea hydrolysis in broth, NGU, upper genital tract infection, spontaneous abortion, neonatal infections

54
Q

Bordetella pertussis

A

 Direct detection or ID by Fluorescent antibody stain
 PCR for diagnosis
 Charcoal containing media for transport and culture – Regan Lowe Charcoal agar
 Tiny gram negative coccobacillus
 3 stages of disease –(1)Prodromal (2) Catarrhal (3) Paroxysmal Prodromal most contagious
 Cough caused by toxin adhering to bronchial epithelial cells, can last for months, esp deadly to young children
 Nasopharyngeal swab for culture
 Reservoir - adult

55
Q

Arcanobacterium haemolyticum

A

gram + rods

beta hemolytic, catalase negative

causes pharyngitis*

trick - could be confused with Strep pyogenes

56
Q

Obligate Anaerobe

A

will not grow in the presence of oxygen, oxygen is toxic

57
Q

Gram Negative Cocci

A

Neisseria species and Moraxella catarrhalis

 Small kidney bean shaped - pairs

 Oxidase positive

 CTA sugar fermentations for identification

 N. gonorrhoeae Gluc + Mal - Lac - Suc -

 N. meningitidis Gluc + Mal + Lac - Suc -

 N. lactamica Gluc + Mal + Lac+ Suc-

 M. catarrhalis all negative, Dna’ase +

Don’t confuse with Acinetobacter species, have very similar morphology. This is why you must culture for women, do you don’t tell them they have gonorrhea with all they have is Acinetobacter (normal flora of female genital tract). Don’t need to culture for men.

58
Q

Francisella tularensis

A

 Possible agent of bioterrorism, hazard in lab
 Fastidious small gram negative cocco bacillus
 Reservoir – rabbits, rodents… infected by ticks and flies.
 Humans infected by bites or directly from animal blood
 Strongly associated with skinning rabbits with bare hands.
 Bacteria can penetrate small breaks in skin/intracellular pathogen
 Can cause painful skin lesions – lymph nodes - leading to bacteremia (ulcerogladular tularemia) Pneumatic
 Culture media must have cysteine*

59
Q

Selective and Differential agars for Staph aureus

A

ChromAgar - S aureus is mauve

Mannitol salt agar

S aureus tolerates the high % of Salt (7.5%) and ferments mannitol and turns yellow

60
Q

Obligate Aerobe

A

requires oxygen to grow

61
Q

Micrococcus species

A

Gram positive cocci in tetrads

 Bright yellow pigment

 Bacitracin susceptible by KB disk test

 Furazolidone resistant (S. aureus is susceptible)

 Modified oxidase reaction positive- Microdase test is positive (main test)

 Does not ferment Glucose (Staph ferments glucose)

 Normal flora & in the environment

 Rare!! Infection in immune compromised

62
Q

Fusobacterium

A

 Fusiform gram negative bacilli, spindle shaped with pointed ends
 Associated with mouth and respiratory tract abscess
 Fusobacterium necrophorum is the type species

63
Q

MacConkey agar

A

MacConkey agar – Differential and Selective

Pink = lactose fermentation

Clear = lactose non fermentation

Differential

Only Gram negative bacilli will grow

64
Q

Specimen collection

A

What requires special transport conditions;

 Anaerobes – eSwab or vial (port o cult)/ no oxygen

N. gonorrhoeae– Charcoal swab, DO NOT refrigerate (charcoal - protects from harsh environment)

 Swabs – Stuart’s or Aimes transport – buffers with peptones etc – preserve viability but not promote growth

 Urine – boric acid to promote stationary phase / or refrigerate within one hour, do not culture >24 hr

 CSF – sterile container – keep at room temp or incubate at 35* C for bacterial culture (for pcr then refrigerate)

 Usually refrigerate if can

65
Q

Unable or difficult to grow

A

 Bartonella henselae –

 cat scratch disease,
 bacillary angiomatosis

 Bartonella quintana – trench fever

 Chlamydiae trachomatis –

 trachoma
 STD- spin down shell vial culture, probe, amplification

 C trachomatis Serovars L1,L2,& L3 =

 Lymphogranuloma venereum

 C. pneumoniae (TWAR)- PCR, cell culture
 C. psittaci- psittacosis, pneumonia, parrots

66
Q

Organism/Disease

A

Francisella tularensis – tularemia
 Bordetella pertussis – whopping cough
 Haemophilus ducreyi – chancroid
 Pasteurella multocida – dog bite
 Capnocytophaga canimorsus – dog bite
 Legionella pneumophila – Legionnaire’s
 Gardnerella vaginalis – Bacterial vaginosis, can use human blood to culture, hemolytic colonies

 Helicobacter pylori – gastritis, ulcer

 Calymmatobacterium granulomatis – granuloma inguinale
 Streptobacillus moniliformis –rat bite fever
 Bartonella henselae– cat scratch, bacillary angiomatosis
 Borrelia burgdorferi – Lyme disease
 B. recurrentis - Borreliosis

Treponema pallidum – syphilis

 T. whippelii – Whipple’s disease

 Bacillus anthracis – anthrax
 Erysipelothrix rhusiopathiae – erysipeloid
 Beta Strep group A - erysipelas

67
Q

Gamma hemolytic Streptococcus

A

Enterococcus and Group D Strep not enterococcus

Enterococcus (major spp = E. faecium and E. faecalis)

 Bile esculin positive

 6.5% salt positive

 PYR positive (Gp. A beta Strep also)*

 E. faecium = arabinose fermentation pos E. faecalis = arabinose neg

 No well defined virulence factors

 Natural resistance to cephalosporins

 Ampicillin/Vancomycin drugs of choice

 Acquired resistance to vancomycin – VRE

 Faecium - resistant to ampicillin, more resistant to vancomycin

 Faecalis - resistant to synercid, less resistant to vancomycin

 Can use bile esculin agar with vancomycin to screen for VRE

 Variety of infections – pathogen of opportunity, NF in intestine, cause UTI, bacteremia, abdominal infections

68
Q

Nutritionally variant Strep

A

Vitamin B6 deficient – pyridoxal dependent

 Will grow in a blood culture bottle – but not on the blood agar plate sub – needs Staph aureus streak to grow “satellite” or media supplemented with vit B6

 Speciated:

 Abiotrophia

 Granulacatilla

 Can cause endocarditis –

 more resistant to antibiotics than “normal” viridans strep

69
Q

Streptococcus Group D not enterococcus

A

Streptococcus bovis

 Bile esculin - positive

 6.5% NaCl - negative (Enterococcus = +)

 PYR - negative

 When found in blood associated with Bowel

carcinoma. Increased % in bowel due to higher

levels of bile or underlying colonic disease

 Always susceptible to Penicillin

70
Q

Oxidative / Fermentative sugar reactions

A

 To determine if a gram negative rod
ferments, assimilates or oxidizes a sugar

 Two tubes containing glucose (green
indicator) one tube layered with oil/ one tube
without oil
 It both tubes turn yellow = fermentation
 If only tube w/o oil turns yellow =
assimilation
 If no tubes yellow = oxidizer

71
Q

Other Vibrio species

A

Vibrio parahemolyticus

 Sucrose negative – green on TCBS

 Diarrhea from ingestion of raw fish and shellfish

 Vibrio vulnificus – highly virulent

 Causes painful skin lesions with muscle necrosis on lower extremities and septicemia in patients with pre existing liver disease

 50% fatality rate

 Ingestion of raw oysters and shellfish from coastal waters

 Lactose positive Vibrio – Green or yellow on TCBS

72
Q

Catalase Negative

A

Streptococcus spp.

Clostridium spp.

Erysipelothrix spp.

Arcanobacterium haemolyticum

Anaerobic Gram positive cocci

73
Q

Glu nonfermenters/oxidase -

A

Acinetobacter – hospital environment and human skin

 Major nosocomial pathogen

 Acquires antibiotic resistance with pressure

 Gram negative cocco baccilli – big diplococci

 Acinetobacter baumannii – glucose oxidizer

 Acinetobacter lwoffi – glucose non oxidizer

 Stenotrophomonas maltophilia

 rapid maltose oxidizer

 Gram negative bacillus

 Resistant to many antibiotics

 Nosocomial pathogen – super-colonizer when on long term Imipenem therapy Steno is naturally resistant to Imp

74
Q

N. meningitidis

A

Neisseria meningitidis – meningitis in young adult hallmark petechiae,

Gram negative cocci in pairs

 Capsular polysaccharide

 Complement deficiencies in 7,8,and 9 can predispose to chronic type disease

 Adrenal necrosis is referred to Waterhouse Friedrichsen syndrome

 Type C is the current endemic strain in the USA – problem in college Freshmen living in dorms recommend immunization

 prophylaxis = rifampin carriage in human NP

 Therapy = penicillin

75
Q

Alpha hemolytic Streptococcus - Viridans streptococci

A

Group of alpha hemolytic Strep found as NF in mouth and upper respiratory tract

S. mutans S. salivarius S. sanguis S. mitis

 Bile esculin negative

 Not bile soluble

 Optochin resistant - <=13 mm

 cause 30 – 40% sub acute endocarditis in pre-exisitng native valve disease

 Variable susceptibility patterns

76
Q

Alpha hemolytic Streptococcus - Strep Pneumococcus

A

Streptococcus pneumonia

vs. viridans Streptococcus

Streptococcus pneumoniae

Gram stain = gram positive lancet shaped cocci with a capsul (polysaccharide capsule is virulence factor)

 Bile soluble (autolytic in sodium deoxycholate)

 Optochin sensitive – 14mm or greater zone around the 6mm disk,

 optochin = ethyl hydrocupreine hydrochloride

 Pathogen of pneumonia, sepsis & CSF. Vaccinate to prevent

 Acquired Resistance to Pen by Pen binding proteins (PBP) I

 Quellung reaction to type the 80+ serotypes

77
Q

More Unable or difficult to grow

A

 Ehrlichia – intracellular pathogen, tick

 fever, leukopenia, thrombocytopenia, elevated serum aminotransferases, no rash (differs from Rocky Mountain Spotted Fever)

 E. chaffeensis – human monocytes
 Ehrlichia spp. – human granulocytes
 found in the midwest, PCR and serology for diagnosis,

78
Q

Bacteria antigens tests on CSF (looking for adequate specimen)

A

Test CSF (containing bacterial antigen) to a battery of latex coated antibodies provided in the test kit .

Designed to look for bacterial antigens in CSF. Most useful in patients partially treated with antibiotics with suspected meningitis – so the culture and even gram stain might be negative.

Always do culture for confirmation of a negative or positive result.

 Neisseria meningitidis B, C, Y, W135 serotypes

 Haemophilus influenzae B (best one, but not needed much because of immunization)

 Streptococcus pneumoniae

 Group B Streptococcus

 Lost popularity - expensive, low sensitivity and specificity

79
Q

Salmonella species

A

Diarrhea +/- fever – polys in the stool

 Associated with food – large #’s of organisms to make you ill

 Can become bacteremic in immune suppressed (HIV)

 Selective media – Hektoen and SS

 Does not ferment lactose/ produces H2S

 Identification based on biochemical reactions and serologic typing “Kaufman White typing scheme”

 O Somatic antigen – cell wall

 H flagellar antigens – 2 phases h1 h2

 Vi capsular antigen –Found in S. typhi only

CP Board Review - Microbiology (6 decks)

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