Gram neg. bacteria Flashcards
List properties/charact. of gram neg. endotoxins. (5)
- Lipid A (Gneg. cell wall)
- Heat stable
- no antigen ≠ IR ≠ anitbody made
- activate coagulation, fibrinolysis, complement
- less potent than exotoxins (not strong in effects)
Which genera of Enterobacteriaceae are always non-motile? (2)
Klebsiella & Shigella
What genera of Enterobacteriaceae is TDA (Tryptophan deaminase) pos?
Proteus, Providencia & Morganella (morganii)
What test & result would you use to identify an organism is a member of the family Enterobacteriaceae and not the genera Pseudomonas, Vibrio and Aeromonas?
Oxidase test (paper turn purple): \+ve = Pseudomonas, Aeromonas, Vibrio -ve= Enterobacteriaceae
Where is Pseudomonas aeruginosa normally found?
Soil, plants, water supply
What does zoonoses mean?
diseases of animals which may be transmitted to humans
Where are O, H, K, F antigens located
O: on LPS of cell wall
H: on flagella
K: capsule
F: fimbrae
How can you tell if the organism growing on the plate is encapsulated?
Colonies will have a slimy/mucous morphology from the mucoid
Where are members of the genera Haemophilus, Neisseria and Moraxella found as normal flora?
Haemophilus: URT
Neisseria: URT [except N. gonorrhea NOT NF (pathogen)]
Moraxella: URT
What type of infections are Haemophilus and Moraxella usually associated with?
RT infections:
- Pneumonia
- Otitis media
Which species of Haemophilus requires both X and V factors but can grow readily on blood agar?
Haemophilus haemolyticus
Why are CHOC plates always incubated in CO2?
Because most organisms that grow on a CHOC plate are Capnophilic (/carboxyphilic)
Name the two pigments produced by Pseudomonas aeruginosa and identify which one is fluorescent under UV light?
- Green pyocyanin
- Yellow (fluoroscein) pyoverdin = can light up under UV light
Compare the infectious dose required for human cholera, salmonellosis and shigellosis. Where are these organisms acquired from?
- Shigellosis acquired from Shigella in GIT of mainly animals, less in humans: ID50= 10-100 organisms
- Salmonellosis acquired from Salmonella in animals: >10^5 organisms
- Cholera acwqurired from V. cholera in human GIT: ID50= 10^10orgs/ml
What would the presence of Gram Neg. Intracell. Diplo Cocci (GNIDC) indicate if seen in a throat swab?
Intracell.= Gneg bact. engulfed & is in neutrophil (WBC)
What primary test results would you expect for a member of the enterobacteriaceae?
- Oxidase test: neg
- Catalase test: +ve
- O-F test: fermentative
- Shape: 5mm, grey colonies on BA w/ opaque centers
- Glucose acid: +ve
- motility
- Grow w/ or w/out O2
How could you differentiate between the two swarming strains of Proteus? What would be the results for each?
Indole test: detect production of tryptophanase (break down tryptophan)
- Pr. vulgaris: +ve
- Pr. mirabilis: neg
If you had a mucoid LF (lactose fermenters) growing on CLED or MAC, how could you differentiate this as either an Enterobacter sp. or a Klebsiella sp. without setting up overnight tests?
Motility test via hanging drop method
- Klebsiella: non-motile
- Enterobacter: motile
List characteristic laboratory features of Pseudomonas aeruginosa. (4-7)
- GNB
- Non-fastidous
- Obligate anaerobe
- Motile
- catalase +ve
- Oxidase: +ve
- O-F: Oxidative
- Colony morphology: Flat, matte, uneven/rough border
Features of Klebsiella
- non-motile
- Mucoid capsules = like stringy cheese
- Idole +ve = K. oxytoca
- Indole -ve= K. pneumonia
What’s x and v factor?
X: haematin, haemin
V: NADP, NAD
Concept of Indole test
test for tryptophanase : tryptophan -> indole -> reacts w/ Kovak’s reagent => pink colour (+ve) for < 10sec
*colonies from BA! bc growing colonies => enzyme
Concept of urease test
test for urease: incubated overnight @ 35ºC -> urease breakdown urea = pink (+ve)
Concept of TDA test
Test for tryptophan deaminase/Phenylalanine deaminase: grow in agar w/ FeCl => green (+ve)
