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Microbiology - Bacteriology > Gram negative rods - Lactose non-fermenters > Flashcards

Gram negative rods - Lactose non-fermenters Flashcards

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1
Q

What is the first step in differentiating gram negative rods that are not lactose fermenters?

A

Oxidase + = Pseudomonas

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2
Q

Where is psuedomonas found?

A

Nosocomial infections! Highly drug resistant.

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3
Q

Is pseudomonas aerobic?

A

Yes.

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4
Q

What is the name of the blue-green pigment pseudomonas produces?

A

Pyocyanin, pyoverdin.

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5
Q

What characteristic odor does Pseudomonas produce?

A

Sweet, grape-like odor.

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6
Q

What toxins does psuedomonas produce?

A

Endotoxin: fever/shock

Exotoxin A: inactivates EF-2 like diphtheria toxin

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7
Q

What clinical presentations are pseudomonas associated with?

A 
BE PSEUDDO:
Burns
Endocarditis
Pneumonia
Sepsis
Externa (otitis - swimmer's ear)
UTIs
Drug use
Diabetes
Osteomyelitis
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8
Q

In what scenarios does Pseudomonas cause folliculitis?

A

Hot tubs!

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9
Q

How can psuedomonas manifest in CF patients?

A

Pnuemonia - mucoid polysaccaride capsule may contribute due to biofilm formation.

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10
Q

Treatment?

A

Heavy duty abx. All the crazy ones.

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11
Q

Treatment for multi-drug resistant strains:

A

Colistin, polymyxin B.

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12
Q

What is ecthyma gangrenosum?

A

Rapidly progressive, necrotic cutaneous lesion caused by Pseudomonas – seen in immunocompromised pts.

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13
Q

If a gram + lactose non fermenter is also oxidase negative, what is the next step in differentiation?

A

TSI agar. If doesn’t produce H2S –> Shigella.

If does produce H2S–> Salmonella, Proteus, Yersinia

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14
Q

What is the reservoir of shigella?

A

Humans only.

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15
Q

How is shigella transmitted?

A

Fecal-oral transmission.

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16
Q

How does shigella spread in the body?

A

Cell to cell only, no hematogenous spread.

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17
Q

Is shigella motile?

A

No - no flagella, no H antigen.

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18
Q

What toxins does shigella produce?

A
  1. Shiga entertoxin : inactivates host 60S.

2. Endotoxin - fever, shock.

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19
Q

Does Shigella require a large or small infectious dose?

A

Low. Very small amount, resistant to gastric acid.

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20
Q

What is the presentation of Shigella?

A

Bloody diarrhea with mucus and pus.

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21
Q

What is the effect of abx on fecal excretion of shigella?

A

Shortens duration.

22
Q

What immune response does shigella generate?

A

Primarily neutrophils.

23
Q

Is there a vaccine for shigella?

A

No.

24
Q

What are the four Fs of shigella?

A

Fingers, Flies, Food, Feces –> transmission routes.

25
Q

What are the four subtypes of shigella, in order of decreasing severity?

A

Dystenteriae
Flexneri
Boydii
Somnei

26
Q

How can shigella organisms cause severe disease without producing a lot of toxin?

A

Invasion.

27
Q

What are the two types of Salmonella?

A

Typhi and Non-typhi

28
Q

What is the difference in reservoirs between S. typhi and non-typhi?

A

S. typhi is in humans only, others can be found in animals as well.

29
Q

What are common sources of non-typhi salmonella?

A

Poultry, eggs, pets, turtles.

30
Q

How does salmonella spread?

A

Can disseminate hematogenously (unlike shigella).

31
Q

Are salmonella motile?

A

Yes. (Salmon swim).

32
Q

What are the virulence factors of Salmonella (non-typhi)?

A

Endotoxin

33
Q

What additional virulence factor does Salmonella typhi have?

A

Vi capsule - protects from intracellular killing

34
Q

Does salmonella require a low or high amount to cause disease?

A

High. Organism inactivated by gastric acid.

35
Q

What is the effect of abx on fecal excretion of salmonella?

A

Prolongs duration, not recommended.

36
Q

What is the immune response to salmonella typhi?

A

Primarily monocytes

37
Q

What is the immune response to salmonella non-typhi?

A

PMNs in disseminated disease

38
Q

Which salmonella type has a vaccine available?

A

Oral vaccine for S. typhi is live attenuated
IM for S. typhi contains Vi capsular polysacch
No vaccine for non-typhi salmonellas.

39
Q

What is the presentation of typhoid fever?

A

Rose spots on abdomen, constipation, diarrhea, abdominal pain, fever.

40
Q

How is typhoid fever treated?

A

Ceftriaxone or fluoroquinolone.

41
Q

What does non-typhii Salmonella cause?

A

Bloody diarrhea.

42
Q

Which salmonella is associated with a carrier state?

A

Typhi. Gallbladder colonization.

43
Q

How is yersinia enterocolitica transmitted?

A

Zoonotic - from puppy feces, pigs, contaminated milk.

44
Q

What is special about yersinia’s virulence factors?

A

Temperature sensitive - expressed at 37 degrees, can survive refrigeration.

45
Q

What are the names of the yersinia’s antigens?

A

V and W antigens.

46
Q

Is Yersinia motile?

A

Yes.

47
Q

What kind of enterotoxin does yersinia have?

A

Enterotoxin similar to heat STABLE toxin on E. coli - increases cGMP levels, prevents resorption of NaCl.

48
Q

What are the sx of yersinia?

A

Acute diarrhea, pseudoappendicitis –> this is due to mesenteric adenitis and/or terminal ileitis.

49
Q

What is distinctive about proteus mirabilis’s metabolic properties?

A

Lactose neg, oxidase neg, indole neg.

Urease! Splits Urea into NH3 and CO2

50
Q

What is the clinical manifestation of proteus?

A

UTI, urine has high pH due to urease.

Stones (ammonia magnesium phosphate).

51
Q

What is the the Weil-felix test?

A

Uses Abs against strains of proteus to diagnose rickettsial disease – certain ricketsiae share similar antigens

Microbiology - Bacteriology (14 decks)

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