Microbiology

Question 1

(T/F) Corynebacterium pseudotuberculosis is the only bacteria that causes caseous abscesses.

Answer 1

(F)

Question 2

(T/F) You need an anaerobic culture to diagnose Corynebacterium pseudotuberculosis.

Answer 2

(F, aerobic since it is a gram positive aerobe, also don’t need susceptibility testing bc do not tx with systemic abx)

Question 3

What is the optimal way to collect a caseous lymphadenitis sample for culture?

Answer 3

(FNA with sterile prep with a large gauge, long needle; lance and draining = environmental contamination)

Question 4

What are the routes of infection for C. pseudotuberculosis?

Answer 4

(Through broken skin, inhalation, or ingestion; maybe flies as mechanical vector)

Question 5

If a small ruminant had internal C. pseudotuberculosis abscesses, what are the possible outward signs?

Answer 5

(Wasting/weight loss)

Question 6

(T/F) Animals vaccinated against C. pseudotuberculosis will always be serologically positive.

Answer 6

(T)

Question 7

Why is C. pseudotuberculosis treatment difficult?

Answer 7

(Abscesses have a fibrous capsule and the bacteria are intracellular)

Question 8

What are the pros and cons of a Salmonella PCR?

Answer 8

(Pros → rapid results; Cons → cost, may be less sensitive, no susceptibility info)

Question 9

What are the pros and cons of a Salmonella culture?

Answer 9

(Pros → less expensive, may be more sensitive, can perform susceptibility testing; Cons → can take more time)

Question 10

(T/F) Antimicrobial treatment of Salmonella colitis does not decrease Salmonella shedding nor change the course of colitis.

Answer 10

(T, and abx treatment in humans with salmonella has been shown to prolong fecal shedding; but antimicrobial treatment may decrease the risk of septicemia)

Question 11

What is the primary route of transmission for Salmonella?

Answer 11

(Fecal-oral)

Question 12

How do patients become carriers of Salmonella?

Answer 12

(Salmonella is facultative intracellular → can infect and persist in macrophages)

Question 13

(T/F) Colic is a risk factor for Salmonella shedding.

Answer 13

(T, so should isolate horses after a significant colic episode)

Question 14

What are the three testing options for Johne’s disease?

Answer 14

(ELISA, culture, and PCR)

Question 15

What are the pros and cons of Johne’s PCR?

Answer 15

(Pros → rapid results, high sensitivity; cons → cost (only costs a bit more than culture), slightly lower sensitivity (?))

Question 16

What are the pros and cons of Johne’s culture?

Answer 16

(Pros → less expensive (not by much), high sensitivity; Cons → Takes months and normal flora overgrowth can lead to false negatives)

Question 17

Is the sensitivity or the specificity low for the Johne’s ELISA test?

Answer 17

(Sensitivity i.e. there are lots of false negatives; has really good specificity tho)

Question 18

When are animals typically infected with Johne’s?

Answer 18

(At or shortly after birth via milk or feces but adult infections can occur as well, clinical signs do not develop for years)

Question 19

What test is performed on renal biopsy tissue when attempting to confirm an FIP diagnosis?

Answer 19

(IHC)

Question 20

What are the cons of the Rivalta POC test for FIP?

Answer 20

(Not all FIP + cats will be positive and other causes of effusion can lead to a false positive)

Question 21

What are the cons of serological testing for FIP?

Answer 21

(Many cats are seropositive, you cannot differentiate b/w response to coronavirus and FIP nutant, and false negatives are possible)

Question 22

(T/F) PCR testing of abdominal fluid cannot distinguish between feline coronavirus and feline infectious peritonitis mutant.

Answer 22

(T)

Question 23

What is the issue with PCR testing fecal material for FIP?

Answer 23

(Lots of healthy cats shed feline coronavirus in their feces, doesn’t mean they have FIP)

Question 24

What determines if a cat gets FIP?

Answer 24

(They have an enteric infection with feline coronavirus, that feline coronavirus mutations to have a macrophage tropism, and they have a lack of a strong cell mediated immune response to the mutated virus; only then will they develop FIP)

Question 25

Why is the leptospirosis IgM lateral flow assay more useful than the leptospira SNAP test?

Answer 25

(SNAP test tests for IgG which can be positive d/t vaccination, also looking for acute infection which IgM will be better for)

Question 26

Why is the leptospira PCR performed on EDTA whole blood not a good test option?

Answer 26

(Leptospiremia is very quick and low, chances of a positive are extremely low)

Question 27

The leptospirosis microagglutination test mostly detects IgM/IgG (choose).

Answer 27

(IgM)