Microbiology: Enteric Bugs - Bacteria 4

Question 1

Fever + watery diarrhea –> Bloody diarrhea + pseudomembranous colitis. What is the causative agent?

Answer 1

Clostridium difficile

Question 2

What are the microbiological characteristics of C. difficile?

Answer 2

Gram+. spore forming bacilli

Can be found in normal flora.

Question 3

What virulence factors are associated with C. difficile?

Answer 3

Toxin A - causes diarrhea (enterotoxin)

Toxin B - Kills colon cells (Cytotoxin)

Question 4

What is the epidemiological background of the C. difficile patient?

Answer 4

Hospitalized and on antibiotics

most common nosocomial infection

Question 5

What is the pathogenesis of C. difficile infections?

Answer 5

Rx clears out normal flora –> C. difficile overgrowth –> Toxin mediated damage –> watery diarrhea –> bloody diarrhea + pseudomembranous colitis

Question 6

How is C. difficile diagnosed?

Answer 6

RADT for Tox A and Tox B in stool

Tox B is cytotoxic in stool culture

Question 7

How is C. difficile treated?

Answer 7

1. Stop inciting antibiotic –> give metronidazole

2. Must wash hands with soap because spores are resistant to alcohol.

Question 8

What is the most likely cause of persistant diarrhea > 10-14 days?

Answer 8

Parasite

Question 9

Which Enteric bacteria are non-motile?

Answer 9

Klebsiella and Shigella

Question 10

What are H antigen, O-antigen, and K-antigen?

Answer 10

H-antigen = flagella
O-antigen = LPS
K-antigen = capsule

Question 11

What are common causes of diarrhea in Aids patients?

Answer 11

Mycobacterium avium

CMV

Question 12

What is usually the underlying cause of long term chronic diarrhea?

Answer 12

HIV

Question 13

What is the feared complication of EHEC infection?

Answer 13

HUS

Question 14

What is the feared complication of C. jejuni infection?

Answer 14

Guillain-Barre syndrome

Question 15

What enteric bacteria can cause Reiter’s syndrome?

Answer 15

Shigella
C. jejuni
Yersinia
Salmonella

Question 16

For which enteric infection are antibiotics contraindicated?

Answer 16

EHEC due to the risk of HUS

Question 17

Gram- bacilli, Lac+, glucose fermenter w/H2 gas, does not produce H2S. What is the species?

Answer 17

E. coli

Question 18

What is the usual cause of neonatal septicemia and meningitis?

Answer 18

E. coli

Question 19

How is the diagnosis of E. coli infection made?

Answer 19

Culture on KIA;
Yellow (glu+/lac+)
No H2S
H2+