Micro Quiz 2 (GNR, GPC) Flashcards
Phenotypic features of Enterobacteriaceae
Gram neg bacilli or coocobacilli
Facultative anaerobes
No spores
Glucose fermenter, Catalase pos, Oxidase neg
Can reduce nitrates to nitrite, can grow on Mac Conkey
Why do stool cultures?
To rule out enteric pathogens (salmonella, shigella, campylobacter, E. coli O157:H7, yersinia, aeromonas, and vibrio)
Stool collection/transport
Plated immediately, or add preservatives and hold on ice for 2 hrs, or in transport medium for up to 4 days (usually Cary-Blair, Amies, or Staurt)
Enterobacteriaceae culture media
Main set up: Blood, Chocolate, Mac Conkey, PEA
Secondary: HE or XLD (use secondary to rule out salmonella)
Enrichment broth to enhance pathogen recovery
E. coli identification
Gram neg bacillus/coocobacillus Lactose-fermenter (pink on MAC)
A/A on TSI and KIA w/ or w/out gas
IMViC = + + - -
Oxidase neg, PYR neg, Nitrate pos, MUG pos
EHEC
Enterohemorrhagic E. coli, “shiga-toxin producing E. coli”
Causes hemorrhagic colitis and hemolytic-uremic syndrome
Nonmotile, MUG neg
Use SMAC media, produces colorless colonies (cannot ferment sorbitol)
What are O and H antigens?
O = somatic/cell wall antigens (seen in all)
H = flagellar antigens (not seen in non-motile strains)
Klebsiella spp. identification
Non-motile* Gram neg bacillus
Lactose-fermenter (pink on MAC)
Encapsulated (mucoid colonies)
A/A on TSI and KIA w/ gas
IMViC = - - + + (opposite E. coli)*
Serratia spp. identification
Motile Gram-neg bacillus (found in soil, water, etc)
Produces red pigment*
Late lactose-fermenter (may take 48 hrs)
A/A on TSI and KIA
Proteus spp. identification
Motile Gram neg bacillus/coccobacillus (“swarmers”)*
Non-lactose fermenter
K/A on TSI and KIA w/ H2S pos
PAD pos (rules out salmonella, shigella, etc)
Morganella morganii identification
Motile Gram neg bacillus/coccobacillus
Similar to Proteus but not “swarmers” and no H2S*
K/A on TSI and HIA
PAD pos
Providencia spp. identification
Motile Gram neg bacillus/coccobacillus
Similar to Moganella, slight difference in IMViC
No H2S, no swarming, PAD pos, K/A on TSI and KIA
Salmonella enterica - serotype Typhi
Passed person to person, can have asymptomatic carriers
High prolonged fever, involvement of RE system of liver, spleen, and intestines
Salmonella spp. identification
Motile Gram neg bacillus
Non-lactose fermenter, colorless on MAC, green/black on HE, red w/ black centers on XLD
K/A on TSI and KIA w/ H2S
IMViC = - + - V
Test with group and type specific antisera (O, H, and Vi)
Shigella spp.
No animal resevoir, 4 serogroups
Nonmotile, Gram neg bacilli
Non lactose fermenter, colorless on MAC, green on HE, colorless on XLD
K/A on TSI and KIA
IMViC = V + - -
Yersinia spp.
More growth at RT
Non motile Gram neg bacillus, bipolar staining (“safety pin”)
Slow grower, pinpoint colonies at 24 hrs, colonies have raised “fried egg” appearance
Non lactose fermenter
K/A on TSI and KIA
IMViC = - + - -
Microaerophile
Low O2 concentration and increased CO2
Capnophiles
Increased CO2
Differential media vs selective media
Differential = still grows several organisms but differentiates between them
Selective = only grows specific organisms
Gram stain procedure
Crystal violet (rinse)
Iodine (rinse)
Decolorizer (rinse)
Safranin (rinse)
GNR characteristics of whole group
1) Glucose utitilization
- fermenters, oxidizers, asaccharolytic (no sugar utilization)
2) Oxidase reaction
- pos and neg
3) Growth on MAC
- pos and neg
Group 1 Bioterrorism species
Brucella spp., Francisella tularensis, Yersinia pestis
Brucella spp.
“Udulant fever”/”Mediterranean fever”
Infects humans and animals, transmission via wound/mucous membrane contact with contaminated food/dairy/birthing or inhalation
Granulomas of liver, bone marrow, spleen, lungs, lymph nodes, testes, kidneys, brain
Slow growers (72 hrs, better on choc, blood cultures kept for 4 wks*)
Look Gram pos, tough to decolorize
Oxidase pos, nitrate pos, urease pos, catalase pos
Francisella tularensis
“Tick fever”, spread by water/soil, handling ill/dead animals, tick/flea bites
Lives in macrophages, require cysteine for growth (grow on choc, Thayer-Martin, BCYE, not blood), poor grower
Catalase pos, oxidase neg, urease neg
Group II: Glucose ferment, MAC pos, Oxidase pos
Aeromonas hydrophila
Pleisiomonas shigelloides
Vibrio spp.
Aeromonas hydrophila
Gastroenteritis, HUS, wound infections, septicemia
Selective media = CIN
Beta hemolytic on blood, oxidase pos, indole pos, not halophilic
Pleisiomonas shigelloides
Same as Aeromonas
Oxidase pos, pos for decarboxylase of lysine, ornithine, and arginine
Not halophilic
Vibrio spp.
Cholera, gastroenteritis, some sucrose fermenters, some not, oysters
Halophilic (grow on TCBS)
String test differentiates V. cholerae from others (draw string from slide when mixed with bile salts)
Group III: GNR Non-fermenters (oxidizers), MAC pos, Oxidase var.
Pseudomonas spp.
Acinetobacter spp.
Burkholderia spp.
P. aeruginosa
Thin GNR, pigmented on blood (blueish-green), fluorescent, pleasent smell, metallic sheen, serated edges, beta hemolytic on blood
Ubiquitious, serious for CF patients
Oxidase pos, TSI = K/No change, grow at 42C, do AST
P. fluorescens/putida
Can’t grow at 42C
Fluorescent, no distinctive odor or morphology
Acinetobacter spp.
Can survive in dry or moist
Non hemolytic, gray colonies, may be lightly pink on MAC (oxidation of lactose)
Oxidase neg, catalase pos
Burkholderia cepacia
Found in animals, water, soil
Transmitted aerosols, skin contact, ingestion
Can be drug resistant, infects CF patients
Selective media = BCSA
Yellow on iron containing media (TSI), earthy dirt odor
Burkholderia pseudomallei
Pneumonia, UTI, genital infections, may be dormant and reactivate
SE Asia and Australia
Oxidase pos, Gram neg bipolar staining
Group IV: GNR Fastidious (“difficult”)
Bartonella spp.
Pasturella spp.
C. jejuni
H. pylori
Bordetella spp.
Legionella spp.
Haemophilus spp.
HACEK
Bartonella spp.
B. henselae = “cat scratch”
Skin has red, berry lesions, collar of scaling
Nomal flora in cat mouth, passed by scratch
Culture on fresh choc agar, 5-10% CO2 (capnophilic)
Oxidase neg, urease neg, catalase neg
Pasteurella spp.
In cat/dog mouth, passed by bite, abcess, septicemia, arthritis, peritonitis
P. multocida most common
Non-hemolytic, shiny colonies, capnophilic, don’t grow on MAC, earthy odor
Use selective media w/ vancomycin, clindamycin, and amikacin
Oxidase pos, catalase pos, indole pos, nitrate pos
Campylobacter
Gastroenteritis, transmitted by contaminated food/poultry/milk/water, infected animals (cats/dogs)
Use Campy blood agar w/ 5 antibiotics, at 42C for 72 hrs, microaerophilic
Curved GNR, “gull wings” ,Oxidase pos, perform AST
Helicobacter pylori
Lives in gastric mucosa of lumen, causes gastritis, ulcers, gastric cancer
Use urease to neutralize acid in stomach, small neutral area around them
Diagnose via biopsy, endoscopy, breath test, EIA
Bordetella pertussis
Vaccine preventable
Nasopharyngeal swab, innoculate bedside
Selective media = Bordet Gengou, Regan-Lowe (charcol and horse blood)
Use DFA or PCR to confirm culture, slow grower
Legionella pneumophila
“Legionnaire’s disease”, pneumoniae, can disseminate to other organs
Survives in moist environments
Selective media = BCYE
HACEK
Haemphophilus aphrophilis
Actinobacillus actinomycetemcomitans
Cardiobacterium hominis
Eikenella corrodens
Kingella spp.
Usual flora of mouth, can cause endocarditis, capnophilic
Abnormal morphology on blood plates
Gram positive cocci
Staphyloccocus
Streptococcus
Enterococcus
Staphylococcus aureus
Causes food poisoning, toxic shock, boils, pneumonia, etc.
Has protein A in cell wall to prevent phagocytosis
Yellow/gold colonies, buttery, usually beta hemolytic, grape like clusters
Catalase pos, coagulase pos
Perform AST, can be highly resistant (MRSA - use oxacillin salt plate for screening)
Coagulase neg Staphylococcus
S. epidermidis, S. saprophyticus, S. lugdeninsis
Normal flora, can be pathogens
S. saprophyticus = UTI, S. epidermidis/lugdeninsis = biofilm attach to plastic (catheter infections, heart valve endocarditis)
White, non-hemolytic
Test AST, S. saprophytics = Novobiocin resistant
Micrococcus spp.
Considered contaminate, looks like staph but w/ tetrad
Coagulase neg, lemon yellow colonies
Differentiate from staph by Bacitracin susceptible, oxidase pos
How to differentiate Streptococcus spp.?
1) Hemolysis pattern
2) Lancefield classification (based on cell wall antigens)
- groups A-H
3) Size ( < or > 0.5 mm)
Beta hemolytic Streptococcus spp.
S. pyogenes
S. dysgalactiae
S. angiosus
S. agalactiae
S. pyogenes
Group A, beta hemolysis, white colonies, large (>0.5mm), Catalase neg, PYR pos, Bacitracin sus., agglutinate in Lancefield type A serum
Pharyngitis, leads to rheumatic fever (autoimmune attacks on heart), and glomerulonephritis
Stab and streak on sheep blood agar w/ Trimeth/sulfa disk (makes media Strep selective), incubate w/ CO2
S. agalactiae
Group B, weak beta hemolytic, white colonies, small
Catalase neg, CAMP pos, Hippurate pos, bile esculin neg, not hapnophilic
GBS issue in pregnant women, neonatal meningitis/pneumoniae
Can look like Listeria, catalase differentiates
S. pneumoniae
Alpha hemolytic, gray colonies, tiny, doughnut shaped
Catalase neg, Optochin sensitive, bile soluble
Causes pnumonia, meningitis, sinusitis, otitis media
Gram pos dipplococci
Streptococcus viridans group
Alpha hemolytic, slow grower, white colonies
Catalase neg, Esculin neg, Optochin resistant, not bile soluble (Makes it different from S. pneumoniae)
Enterococcus spp. (E. faecalis/faecium)
White/gray, not usually hemolytic
Catalase neg (weak bubbles), hapnophilic, Bile esculin pos, PYR pos, Lancefield Group D
E.faecalis/faecium can be vancomycin resistant
