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Microbio. (MEDI2003) > Gram neg. bacteria > Flashcards

Gram neg. bacteria Flashcards

1
Q

List properties/charact. of gram neg. endotoxins. (5)

A
  • Lipid A (Gneg. cell wall)
  • Heat stable
  • no antigen ≠ IR ≠ anitbody made
  • activate coagulation, fibrinolysis, complement
  • less potent than exotoxins (not strong in effects)
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2
Q

Which genera of Enterobacteriaceae are always non-motile? (2)

A

Klebsiella & Shigella

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3
Q

What genera of Enterobacteriaceae is TDA (Tryptophan deaminase) pos?

A

Proteus, Providencia & Morganella (morganii)

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4
Q

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?

A 
Oxidase test (paper turn purple): 
\+ve = Pseudomonas, Aeromonas, Vibrio
-ve= Enterobacteriaceae
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5
Q

Where is Pseudomonas aeruginosa normally found?

A

Soil, plants, water supply

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6
Q

What does zoonoses mean?

A

diseases of animals which may be transmitted to humans

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7
Q

Where are O, H, K, F antigens located

A

O: on LPS of cell wall
H: on flagella
K: capsule
F: fimbrae

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8
Q

How can you tell if the organism growing on the plate is encapsulated?

A

Colonies will have a slimy/mucous morphology from the mucoid

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9
Q

Where are members of the genera Haemophilus, Neisseria and Moraxella found as normal flora?

A

Haemophilus: URT
Neisseria: URT [except N. gonorrhea NOT NF (pathogen)]
Moraxella: URT

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10
Q

What type of infections are Haemophilus and Moraxella usually associated with?

A

RT infections:

  • Pneumonia
  • Otitis media
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11
Q

Which species of Haemophilus requires both X and V factors but can grow readily on blood agar?

A

Haemophilus haemolyticus

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12
Q

Why are CHOC plates always incubated in CO2?

A

Because most organisms that grow on a CHOC plate are Capnophilic (/carboxyphilic)

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13
Q

Name the two pigments produced by Pseudomonas aeruginosa and identify which one is fluorescent under UV light?

A
  • Green pyocyanin

- Yellow (fluoroscein) pyoverdin = can light up under UV light

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14
Q

Compare the infectious dose required for human cholera, salmonellosis and shigellosis. Where are these organisms acquired from?

A
  • 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
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15
Q

What would the presence of Gram Neg. Intracell. Diplo Cocci (GNIDC) indicate if seen in a throat swab?

A

Intracell.= Gneg bact. engulfed & is in neutrophil (WBC)

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16
Q

What primary test results would you expect for a member of the enterobacteriaceae?

A
  • 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
17
Q

How could you differentiate between the two swarming strains of Proteus? What would be the results for each?

A

Indole test: detect production of tryptophanase (break down tryptophan)

  • Pr. vulgaris: +ve
  • Pr. mirabilis: neg
18
Q

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?

A

Motility test via hanging drop method

  • Klebsiella: non-motile
  • Enterobacter: motile
19
Q

List characteristic laboratory features of Pseudomonas aeruginosa. (4-7)

A
  • GNB
  • Non-fastidous
  • Obligate anaerobe
  • Motile
  • catalase +ve
  • Oxidase: +ve
  • O-F: Oxidative
  • Colony morphology: Flat, matte, uneven/rough border
20
Q

Features of Klebsiella

A
  • non-motile
  • Mucoid capsules = like stringy cheese
  • Idole +ve = K. oxytoca
  • Indole -ve= K. pneumonia
21
Q

What’s x and v factor?

A

X: haematin, haemin
V: NADP, NAD

22
Q

Concept of Indole test

A

test for tryptophanase : tryptophan -> indole -> reacts w/ Kovak’s reagent => pink colour (+ve) for < 10sec
*colonies from BA! bc growing colonies => enzyme

23
Q

Concept of urease test

A

test for urease: incubated overnight @ 35ºC -> urease breakdown urea = pink (+ve)

24
Q

Concept of TDA test

A

Test for tryptophan deaminase/Phenylalanine deaminase: grow in agar w/ FeCl => green (+ve)

Microbio. (MEDI2003) (16 decks)

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