Gastrointestinal Infections Flashcards
Most common viral cause of foodborne illness
Norovirus 5.4 million/year 26% foodborne
Viral causes of foodborne illness
- Norovirus (5.4/1.4M)
- Rotavirus (15K/<1)
- Astrovirus (15K<1)
- Sapovirus (15K<1)
- Hepatitis A virus (1.5K/109/0.31/0.02)
Most common bacterial causes of foodborne illness
- Salmonella (1M/0.27)
- Clostridium perfringens (965K)
- Campylobacter (845/675K/0.17)
- Staph aureus (241K/0.06)
Most common parasitic causes of foodborne illness
- Toxoplasma gondii (86/43K/0.02)
Inflammatory diarrhea, agents (foodborne)
- Salmonella
- Campylobacter
- Shigella
- E. coli, enterohemorrhagic
- Yersinia
- Vibrio parahemolyticus
- Entamoeba histolytica
Watery diarrhea, agents (foodborne)
- Norovirus
- Clostridioides
- Clostridium perfringens
- E. coli, enterotoxigenic
- Rota, astro, sapo, adenovirus
- Giardia lamblia
- Cryptosporidium parvum
- Listeria monocytogenes
Norovirus seasonality
Anytime, highest Nov-April
Norovirus inoculum transmission required
<100 viral particles
Norovirus routes
- Fecal-oral
- Airborne vomitus droplets
- Fomites
- Contaminated foods and water (greens, fresh fruit, shellfish)
Norovirus stability
Extreme environmental stability, resists freezing and heating to 60ºC and chlorine and EtOH
Noroviral shedding period
⬆︎risk first 24-48HR post-onset; mean duration 4WK
Norovirus outbreaks
Cruise ships
Resorts
Community/education settings
Hospitals
Restaurants/catering
Prisons
Norovirus immunity
Some immunity = same genogroup; less immunity = diff genogroup
Norovirus symptoms
May be asymptomatic carrier (esp after repeated exposure)
- Nausea, vomiting (explosive) (nonbloody, nonbilious)
- Watery diarrhea (explosive)(nonbloody)
- Abdominal pain
Norovirus return to activity
Isolate until 48-72HR post sx resolution
First line management for traveler’s diarrhea
Oral rehydration, dietary modification as needed (BRAT or to tolerance)
Typical course for traveler’s diarrhea
3-5 days
Predominant pathogen implicated in traveler’s diarrhea
Enterotoxigenic Escherichia coli (ETEC)
Home recipe for oral rehydration solution
0.5 tsp table salt, 0.5 tsp baking soda, 4 Tbsp sugar, 1 liter water
BRAT diet for GI disorders?
Limited evidence, should eat or not eat to tolerance, which often means mild, bland diet such as BRAT, oral fluids most important
First line antibiotic for traveler’s diarrhea
Azithromycin 1 g PO once; or azithromycin 500 mg PO daily x3
Fluoroquinolones for traveler’s diarrhea
No longer recommended d/t increased microbial resistance; use selectively; teratogenic
Antimotility agent use in diarrhea
Loperamide only if non-dysenteric (blood, mucus) diarrhea
Possible sequela of antimotility agents in invasive inflammatory diarrhea
Toxic megacolon
Other microbes implicated in traveler’s diarrhea
Giardia, Shigella, Campylobacter, Entamoeba, Strongyloides
When to suspect less common causes of traveler’s diarrhea
Persistent diarrhea >10-14 days despite standard care
Important diarrheal pathogens in MSM
Giardia, Shigella, E.histolytica
Alternative antimicrobial agents for traveler’s diarrhea
Rifaximin and rifamycin; avoid in invasive diarrhea
Infectious causes of toxic megacolon
Clostridioides difficile; Salmonella; Shigella; Campylobacter; Yersinia; Entamoeba histolytica; Cryptosporidium; CMV; Kaposi sarcoma
Most common non-infectious causes of toxic megacolon
Ulcerative colitis > Crohn’s disease
Helicobacter pylori testing
Stool antigen; urea breath testing
Testing for active H. pylori infection
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
Leptospirosis incidence in US
Low incidence, 100-200 cases/year; >half in Hawaii
Leptospirosis distribution
Tropics; Australia, South America, Africa,
Considerations for empiric treatment for dysenteric/bloody diarrhea
Recommend azithromycin 500 mg PO x3 days (not 1 g once); consider adding metronidazole to cover anaerobes and protozoans
