Gram negative rods - Lactose non-fermenters

Question 1

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

Answer 1

Oxidase + = Pseudomonas

Question 2

Where is psuedomonas found?

Answer 2

Nosocomial infections! Highly drug resistant.

Question 3

Is pseudomonas aerobic?

Answer 3

Yes.

Question 4

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

Answer 4

Pyocyanin, pyoverdin.

Question 5

What characteristic odor does Pseudomonas produce?

Answer 5

Sweet, grape-like odor.

Question 6

What toxins does psuedomonas produce?

Answer 6

Endotoxin: fever/shock

Exotoxin A: inactivates EF-2 like diphtheria toxin

Question 7

What clinical presentations are pseudomonas associated with?

Answer 7

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

Question 8

In what scenarios does Pseudomonas cause folliculitis?

Answer 8

Hot tubs!

Question 9

How can psuedomonas manifest in CF patients?

Answer 9

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

Question 10

Treatment?

Answer 10

Heavy duty abx. All the crazy ones.

Question 11

Treatment for multi-drug resistant strains:

Answer 11

Colistin, polymyxin B.

Question 12

What is ecthyma gangrenosum?

Answer 12

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

Question 13

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

Answer 13

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

If does produce H2S–> Salmonella, Proteus, Yersinia

Question 14

What is the reservoir of shigella?

Answer 14

Humans only.

Question 15

How is shigella transmitted?

Answer 15

Fecal-oral transmission.

Question 16

How does shigella spread in the body?

Answer 16

Cell to cell only, no hematogenous spread.

Question 17

Is shigella motile?

Answer 17

No - no flagella, no H antigen.

Question 18

What toxins does shigella produce?

Answer 18

1. Shiga entertoxin : inactivates host 60S.

2. Endotoxin - fever, shock.

Question 19

Does Shigella require a large or small infectious dose?

Answer 19

Low. Very small amount, resistant to gastric acid.

Question 20

What is the presentation of Shigella?

Answer 20

Bloody diarrhea with mucus and pus.

Question 21

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

Answer 21

Shortens duration.

Question 22

What immune response does shigella generate?

Answer 22

Primarily neutrophils.

Question 23

Is there a vaccine for shigella?

Answer 23

No.

Question 24

What are the four Fs of shigella?

Answer 24

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

Question 25

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

Answer 25

Dystenteriae Flexneri Boydii Somnei

Question 26

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

Answer 26

Invasion.

Question 27

What are the two types of Salmonella?

Answer 27

Typhi and Non-typhi

Question 28

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

Answer 28

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

Question 29

What are common sources of non-typhi salmonella?

Answer 29

Poultry, eggs, pets, turtles.

Question 30

How does salmonella spread?

Answer 30

Can disseminate hematogenously (unlike shigella).

Question 31

Are salmonella motile?

Answer 31

Yes. (Salmon swim).

Question 32

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

Answer 32

Endotoxin

Question 33

What additional virulence factor does Salmonella typhi have?

Answer 33

Vi capsule - protects from intracellular killing

Question 34

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

Answer 34

High. Organism inactivated by gastric acid.

Question 35

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

Answer 35

Prolongs duration, not recommended.

Question 36

What is the immune response to salmonella typhi?

Answer 36

Primarily monocytes

Question 37

What is the immune response to salmonella non-typhi?

Answer 37

PMNs in disseminated disease

Question 38

Which salmonella type has a vaccine available?

Answer 38

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

Question 39

What is the presentation of typhoid fever?

Answer 39

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

Question 40

How is typhoid fever treated?

Answer 40

Ceftriaxone or fluoroquinolone.

Question 41

What does non-typhii Salmonella cause?

Answer 41

Bloody diarrhea.

Question 42

Which salmonella is associated with a carrier state?

Answer 42

Typhi. Gallbladder colonization.

Question 43

How is yersinia enterocolitica transmitted?

Answer 43

Zoonotic - from puppy feces, pigs, contaminated milk.

Question 44

What is special about yersinia's virulence factors?

Answer 44

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

Question 45

What are the names of the yersinia's antigens?

Answer 45

V and W antigens.

Question 46

Is Yersinia motile?

Answer 46

Yes.

Question 47

What kind of enterotoxin does yersinia have?

Answer 47

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

Question 48

What are the sx of yersinia?

Answer 48

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

Question 49

What is distinctive about proteus mirabilis's metabolic properties?

Answer 49

Lactose neg, oxidase neg, indole neg. | Urease! Splits Urea into NH3 and CO2

Question 50

What is the clinical manifestation of proteus?

Answer 50

UTI, urine has high pH due to urease. | Stones (ammonia magnesium phosphate).

Question 51

What is the the Weil-felix test?

Answer 51

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