161b - Microbial Pathogens of the GI Tract (Only including things not in sketchy)

Question 1

All of the following cause an inflammatory diarrhea EXCEPT:

A. Salmonella enterica

B. Shigella flexneri

C. Campylobacter jejuni

D. Cryptosporidium

E. Entamoeba histolytica

Answer 1

D. Cryptosporidium

• Vibrios; Enterotoxigenic E.coli (ETEC), C. perfringens, B. cereus, S. aureus, Rotavirus, Norovirus, Giardia = Non-inflammatory*
• Salmonella, Shigella, Campylobacter, Histolytica, Enterohemmorhagic E. coli (EHEC), Yersinia = Inflammatory*

Question 2

Describe the mechanism of cholera toxin

Answer 2

A1 subunit of the cholera’s AB toxin ADP ribosylates the regulatory component of host cell adenylate cyclase

• -> upregulation adenylate cyclase
• -> Increased cAMP
• -> Activates CFTR
• -> Increased Cl- secretion, decreased Na+ uptake
• -> Water follows
• -> Watery diarrhea (secretory diarrhea)

Question 3

Which bacteria causes inflammatory diarrhea followed by Guillain-Barre syndrome?

Answer 3

Campylobacter

Question 4

What signs/symtpoms would lead you to suspect S. aureus as a cause of food poisoning?

Answer 4

Lots of vomiting

Rapid onset

Question 5

What food is associated with bacillus cereus?

Answer 5

Re-heated rice

Question 6

How is cholera diagnosed?

Answer 6

Culture organisms on TCBS agar

Question 7

Vomiting, diarrhea, and respiratory symptoms in children are most likely caused by which virus?

Answer 7

Rotavirus

Question 8

What organism is this?

Answer 8

Giardia

Question 9

What cells will be found in inflammatory diarrhea?

Answer 9

Leukocytes and/or red blood cells

Question 10

Does shigella casue bacteremia?

Answer 10

Not usually

(even though it is invasive)

Question 11

For which of the intestinal pathogens does an ADP-ribosylating toxin play a crucial role in disease?

Answer 11

Vibrio cholera

Question 12

Which vibrio is most likely to cause bacteremia?

Answer 12

Vulnificus

Especially in people with a history of alcohol use disorder

(V. cholerae isn’t invasive; won’t caues bacteremia)

Question 13

Which enzymes are inactivated by C. diff toxins?

What is the physiological consequence?

Answer 13

Rho GTPases

-> Cell death, loss of barrier function

Question 15

How is clostridium perfringens acquired?

Answer 15

Wounds (inoculation from spores in the soul)

Ingestion of meat and poultry

Question 16

Describe the mechanism of entamoeba histolytica’s toxin

Answer 16

Pore forming -> epithelial cell lysis -> flask-shaped ulcer