This document discusses infectious causes of diarrhea. It begins by noting important history details for infectious diarrhea cases, such as location, duration, symptoms, and risk factors. It then discusses specific pathogens that can cause acute (less than 14 days) infectious diarrhea like norovirus, salmonella, campylobacter, shigella, ETEC, and C. difficile. It provides details on the pathogenesis and typical inoculum sizes of these pathogens. The document concludes by discussing workup, differential diagnosis, and special considerations for persistent, chronic, and resource-limited setting diarrhea.

1. Poop and Belly Pain
(oh my)
[ENTERIC INFECTIONS]
Sophie Woolston MD
Infectious Disease
1/22/19

3. Acknowledgements
• We are all adults here
• You all are eating lunch
• Nevertheless, I shall persist…

4. Important History Details for Infectious
Diarrhea
• Location, location (where in the world; camping with beavers vs
nursing home vs restaurant vs pet turtle exposure)
• Duration
• As many descriptors as possible (frequency, consistency, bloody/non
bloody, mucus)
• Associated symptoms (f/c/leukocytosis)
• Preceding events/exposures (pets, hobbies, travel, occupation)
• Assessment of volume status (dark/scant urine, sxs or orthostasis) &
immune status

5. Acute diarrhea
• Defined by duration of symptoms:
• 14 days of fewer in duration
• ~11-12K deaths/year
• CDI most common cause of death
• Norovirus in elderly; salmonella; listeria

6. Acute (Infectious) Diarrhea - etiology
• Most cases are self limited (i.e., resolve without treatment!!)
• Most cases are caused by viruses (norovirus, rotavirus, adenoviruses,
astrovirus, etc.)
• For all cases, stool cultures positive <5% of the time; even though
most cases are likely infectious
• For severe diarrhea, bacterial causes more likely:
(Salmonella, Campylobacter, Shigella, enterotoxigenic Escherichia
coli, Clostridium difficile, and others)
• Protozoa ( (Cryptosporidium, Giardia, Cyclospora, Entamoeba, and
others) least likely cause of acute GI illness

8. Acute Infectious Diarrhea Pathogenesis:
The Nitty Gritty
• Norovirus: (1/2 of all foodborne illnesses), secondary attack common, NH, cruise ships,
SCT
• Salmonella: food, exotic pets, chicks. Bacteremia in healthy pts: 8%
• Campylobacter: food (poultry), RF travel, recent abx. Cipro R, complicated by GBS, IBS,
RA
• Shigella: low dose pathogen; secondary attack, dysentery 50%; reactive arthritis, iritis
persistent illness
• ETEC: major cause of diarrhea in children and travelers (enterotoxins)
• EAEC: persistent diarrhea in tropics (kids), AIDS-associated chronic diarrhea. Now seen
more in US kid diarrhea cases (contaminated school lunches)
• Shiga toxin-producing e coli: cattle is reservoir. Sear don’t grind! Wash your produce!
Avoid wading pools
• [0157: 85% bloody stools; 9% HUS
• [non-0157: 13% blood stools, 9% HUS

9. Causes of Bloody diarrhea
• (rule out GIB!)
• Bacteria: c. jejuni, salmonella, ecoli 0157:H7 (and STEC), v.
parahaemolyticus, shigella, Yersinia, aremonas, ? C diff
• Viruses: CMV
• Parasite: Entamoeba histolytica, schistosomiasis

10. Pathogen Group Expected Inoculum Size
Norovirus and Shigella spp 10-100 organisms
Giardia, cryptosporidium, shiga toxin producing e coli,
salmonella
80-100K organisms
Campylobacter, EIEH, ETEC, v. cholera 500->1million organisms
The lower the inoculum size, easier to spread!

11. Acute Diarrhea Workup
• History and physical examination
• Stool culture
• Ova and parasite
• Stool WBCs – demonstrating inflammatory diarrhea (shigella,
campylobacter, salmonella, shigella) -predictor for invasive disease
(sort of)
• colonoscopy

12. Acute Diarrhea Workup
• Stool culture: costs ~$100-200 out of pocket, positive <5% of time
• Perform for limited # of patients:
• Any patient w/ symptoms>7days
• Severe illness (dehydration, > 7 stools/24h, severe abd pain, hospitalization)
• c/for inflammatory diarrhea (bloody BMs, fever>101.3F)
• High risk host: immunocompromised (HIV, SCT/SOT, malignancy) comorbidities [CHF,
ESRD] affected by severe dehydration, IBD, age >70, pregnancy
• Public health concerns: (food handlers, healthcare workers, daycare workers)
• Main purpose of stool culture: identify a treatable (usually bacterial)
condition, identify potential for complications
• Don’t send stool cx for most hospitalized patients who develop diarrhea after
72 hr post-admission (consider c diff)

13. Stool culture (ctned)
• Routine cx IDs: salmonella, campy, shigella (3 most common causes of
bacterial diarrhea in US)
• E coli 0157:H7 needs sorbitol-MacConkey plates (automatic at VM)
• Campylobacter is fastidious, needs special selective media, temp,
environment (automatic at VM)
• NOTIFY lab if suspecting aeremonas, yersinia (traveler’s diarrhea,
foodborne outbreaks, infants); grown on nl culture but often can be
overlooked.
• NOTIFY if suspect vibrio (needs selective media to suppress growth of other
organisms
• Bacterial are excreted continuously; o&p intermittently. (-) stool cultures
are usually true negatives, o&p need to be repeated if (-) test but high
suspicion

14. Stool culture
• At VM, our stool culture includes PCRs for viruses

15. Question One:
• Healthy 31 M traveler to S. Africa, Botswana. Developed watery
diarrhea non-responsive to 3 days of BID ciprofloxacin. Significant
cramping.
• What’s your differential diagnosis? What is it less likely to be?

16. • Differential dx:
• Giardiasis, Cipro-R bacteria (like campylobacter enteritis, s. typhi), C
diff, Cryptosporidium species, Entamoeba histolytica, Isospora belli,
Microsporidia, Dientamoeba fragilis, and Cyclospora cayetanensis.
• Less likely to be:
• Cholera (sensitive to Cipro), ETEC

17. Persistent diarrhea in the returning traveler
History clues:
• Upper GI symptoms: (bloating, gas, nausea): giardia, cyclospora,
isospora
• Systemically ill: s. typhus (stepwise fever): chills, rose spots on
abdomen
• Fever and colitic symptoms (bloody diarrhea, abd cramping): campy
or shigella, ETEC, STEC
• Antibiotic use: c diff

18. Question Two
• Same healthy young guy goes to S. Africa, has traveler’s diarrhea.
Takes Cipro. Some improvement, then develops worsening diarrhea,
some cramping.
• Differential Dx?

19. Differential Dx
• C diff….or much, much more likely:
• Post-infectious IBS – up to 1/3 of patients will have chronic mucosal
immunologic dysregulation with changed permeability and motility.
• Loperimide
• Simethicone, hyoscyamine for bloating
• TCA and SSRI; chronic IBS pain (and TCAs slow transit time)
• Probiotic rich food – KEFIR, sauerkraut, miso, etc.

20. Question Three
• Mother starts feeling nauseated a day after her 17 month old twins
develop episodic vomiting
• Most likely etiology (and less likely ones)
• Best medical advice

21. Question Three
• Norovirus most likely
• ?rotavirus (if not vaccinated)
• Enteric adenovirus
• S. aureus (mayonnaise) (classic: church picnic in June)
• Stay home at least for 24 hours after last episode of vomiting (still
infectious!), fluids, fluids

22. Question 3.b
• Same rascally twins develop bloating and diarrhea after enjoying s’mores and some river
water while camping…what gives?
(not a true story…thankfully)

24. Question Four
• 42 M relatively healthy develops non blood diarrhea. Relatively
healthy. Social hx: patient works as a tennis pro, is MSM (and
recently single), no illicit

25. Question Four
• RAI or OAI increases risk for direct inoculation with shigella, giardia,
or e. histolytica. Or possibly STI from proctitis: chlamydia, gonorrhea,
syphilis, HSV

26. Question Five
• In which patient populations should CMV colitis be considered?

27. Question Five
• HIV CD4 <50 cells/microL, SOT, SCT

28. Question Six
• With the Easter holiday coming up, what is one diarrheal etiology that
will likely become more common?

29. Question Six
• Salmonellosis

30. Resource limited settings
• diarrhea may also occur in the context of other systemic infections,
such as influenza, HIV infection, dengue fever, and malaria. Non-
infectious etiologies of diarrhea are often missed and should be
considered in patients with repeated episodes of self-limiting or acute
diarrhea or chronic diarrhea. Such causes include inflammatory bowel
disease and malabsorptive syndromes.
• Epidemic: v. cholera and shigella dysentariae serotype 1 (Sd1)

31. Chronic Diarrhea
• > 30 days in duration
• Much less likely to be infections
• Most likely c diff or giardia
• Could also be aeromonas, plesiomonas, campylobacter, amebae,
cryptosporidium, cyclosporidium, whipples disease

32. Flynn, P. Emerging Diarrheal Pathogens: C. parvum, I belli, C sp, Microsporidia. Pediatric Annals. V 25 Issue 9: 480-87 1996.

33. Questions?