Gastrointestinal Infections

Question 1

Most common viral cause of foodborne illness

Answer 1

Norovirus 5.4 million/year 26% foodborne

Question 2

Viral causes of foodborne illness

Answer 2

1. Norovirus (5.4/1.4M)
2. Rotavirus (15K/<1)
3. Astrovirus (15K<1)
4. Sapovirus (15K<1)
5. Hepatitis A virus (1.5K/109/0.31/0.02)

Question 3

Most common bacterial causes of foodborne illness

Answer 3

1. Salmonella (1M/0.27)
2. Clostridium perfringens (965K)
3. Campylobacter (845/675K/0.17)
4. Staph aureus (241K/0.06)

Question 4

Most common parasitic causes of foodborne illness

Answer 4

1. Toxoplasma gondii (86/43K/0.02)

Question 5

Inflammatory diarrhea, agents (foodborne)

Answer 5

1. Salmonella
2. Campylobacter
3. Shigella
4. E. coli, enterohemorrhagic
5. Yersinia
6. Vibrio parahemolyticus
7. Entamoeba histolytica

Question 6

Watery diarrhea, agents (foodborne)

Answer 6

1. Norovirus
2. Clostridioides
3. Clostridium perfringens
4. E. coli, enterotoxigenic
5. Rota, astro, sapo, adenovirus
6. Giardia lamblia
7. Cryptosporidium parvum
8. Listeria monocytogenes

Question 7

Norovirus seasonality

Answer 7

Anytime, highest Nov-April

Question 8

Norovirus inoculum transmission required

Answer 8

<100 viral particles

Question 9

Norovirus routes

Answer 9

1. Fecal-oral
2. Airborne vomitus droplets
3. Fomites
4. Contaminated foods and water (greens, fresh fruit, shellfish)

Question 10

Norovirus stability

Answer 10

Extreme environmental stability, resists freezing and heating to 60ºC and chlorine and EtOH

Question 11

Noroviral shedding period

Answer 11

⬆︎risk first 24-48HR post-onset; mean duration 4WK

Question 12

Norovirus outbreaks

Answer 12

Cruise ships
Resorts
Community/education settings
Hospitals
Restaurants/catering
Prisons

Question 13

Norovirus immunity

Answer 13

Some immunity = same genogroup; less immunity = diff genogroup

Question 14

Norovirus symptoms

Answer 14

May be asymptomatic carrier (esp after repeated exposure)

1. Nausea, vomiting (explosive) (nonbloody, nonbilious)
2. Watery diarrhea (explosive)(nonbloody)
3. Abdominal pain

Question 15

Norovirus return to activity

Answer 15

Isolate until 48-72HR post sx resolution

Question 16

First line management for traveler’s diarrhea

Answer 16

Oral rehydration, dietary modification as needed (BRAT or to tolerance)

Question 17

Typical course for traveler’s diarrhea

Answer 17

3-5 days

Question 18

Predominant pathogen implicated in traveler’s diarrhea

Answer 18

Enterotoxigenic Escherichia coli (ETEC)

Question 19

Home recipe for oral rehydration solution

Answer 19

0.5 tsp table salt, 0.5 tsp baking soda, 4 Tbsp sugar, 1 liter water

Question 20

BRAT diet for GI disorders?

Answer 20

Limited evidence, should eat or not eat to tolerance, which often means mild, bland diet such as BRAT, oral fluids most important

Question 21

First line antibiotic for traveler’s diarrhea

Answer 21

Azithromycin 1 g PO once; or azithromycin 500 mg PO daily x3

Question 22

Fluoroquinolones for traveler’s diarrhea

Answer 22

No longer recommended d/t increased microbial resistance; use selectively; teratogenic

Question 23

Antimotility agent use in diarrhea

Answer 23

Loperamide only if non-dysenteric (blood, mucus) diarrhea

Question 24

Possible sequela of antimotility agents in invasive inflammatory diarrhea

Answer 24

Toxic megacolon

Question 25

Other microbes implicated in traveler's diarrhea

Answer 25

Giardia, Shigella, Campylobacter, Entamoeba, Strongyloides

Question 26

When to suspect less common causes of traveler's diarrhea

Answer 26

Persistent diarrhea \>10-14 days despite standard care

Question 27

Important diarrheal pathogens in MSM

Answer 27

Giardia, Shigella, E.histolytica

Question 28

Alternative antimicrobial agents for traveler's diarrhea

Answer 28

Rifaximin and rifamycin; avoid in invasive diarrhea

Question 29

Infectious causes of toxic megacolon

Answer 29

Clostridioides difficile; Salmonella; Shigella; Campylobacter; Yersinia; Entamoeba histolytica; Cryptosporidium; CMV; Kaposi sarcoma

Question 30

Most common non-infectious causes of toxic megacolon

Answer 30

Ulcerative colitis \> Crohn's disease

Question 31

Helicobacter pylori testing

Answer 31

Stool antigen; urea breath testing

Question 32

Testing for active H. pylori infection

Answer 32

Stool antigen and urea breath testing have comparable performance; antigen testing is typically easier to collect and more cost effective; UBT fails often during collection, storage or transportation due to lab tech unfamiliarity

Question 33

Leptospirosis incidence in US

Answer 33

Low incidence, 100-200 cases/year; \>half in Hawaii

Question 34

Leptospirosis distribution

Answer 34

Tropics; Australia, South America, Africa,

Question 35

Considerations for empiric treatment for dysenteric/bloody diarrhea

Answer 35

Recommend azithromycin 500 mg PO x3 days (not 1 g once); consider adding metronidazole to cover anaerobes and protozoans