Enlist the bacteria causing diarrhoea
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I now have comprehensive information from Harrison's Principles of Internal Medicine (22nd Ed), Textbook of Family Medicine, and Frameworks for Internal Medicine. Here is the full answer:
Bacteria Causing Diarrhoea
Bacteria cause diarrhoea through three main mechanisms: toxin production (enterotoxins, cytotoxins, neurotoxins), mucosal invasion, and adherence/effacement. They are best classified by mechanism and the type of diarrhoea they produce.
1. Noninflammatory (Secretory/Watery) Diarrhoea
Mechanism: Enterotoxin production in the proximal small bowel → increased secretion, no mucosal destruction. Stools are watery with no fecal leukocytes.
| Organism | Key Features |
|---|---|
| Vibrio cholerae | Cholera toxin (ADP-ribosylates Gs protein → ↑cAMP); profuse "rice-water" stools; life-threatening dehydration |
| Enterotoxigenic E. coli (ETEC) | Heat-labile (LT) and/or heat-stable (ST) toxins; leading cause of traveler's diarrhoea |
| Enteroaggregative E. coli (EAEC) | Aggregative adherence; persistent watery diarrhoea, especially in children and travellers |
| Clostridium perfringens | Preformed toxin from contaminated meat/poultry; short-lived watery diarrhoea |
| Bacillus cereus (diarrhoeal type) | Heat-labile enterotoxin; associated with rice and fried foods |
| Staphylococcus aureus | Preformed neurotoxin (acts on CNS/vagus); rapid-onset vomiting + diarrhoea (1-6 h); food poisoning |
| Aeromonas hydrophila | Aquatic environments; watery or bloody diarrhoea |
| Plesiomonas shigelloides | Contaminated water/raw shellfish; watery diarrhoea |
2. Inflammatory (Invasive/Bloody) Diarrhoea - Dysentery Syndrome
Mechanism: Mucosal invasion or cytotoxin production in the colon → destruction of enterocytes, fecal leukocytes, blood and mucus in stool, fever.
| Organism | Key Features |
|---|---|
| Shigella spp. (esp. S. dysenteriae type 1) | Prototype of dysentery ("sekiri"/red diarrhoea); Shiga toxin (cytotoxin); low infectious dose; person-to-person spread |
| Salmonella spp. (nontyphoidal) | Watery or bloody diarrhoea; from poultry, eggs, beef; self-limited; can cause enteric fever (S. typhi, S. paratyphi) |
| Campylobacter jejuni | Most common bacterial cause of acute diarrhoea in many developed countries; raw poultry; can trigger Guillain-Barre syndrome (ascending paralysis post-gastroenteritis) |
| Enterohemorrhagic E. coli (EHEC) - O157:H7 | Shiga toxin; hemorrhagic colitis; risk of hemolytic-uremic syndrome (HUS); from undercooked beef |
| Enteroinvasive E. coli (EIEC) | Invades colonic mucosa like Shigella; dysentery syndrome |
| Yersinia enterocolitica | Contaminated pork; pseudo-appendicitis picture; can be associated with reactive arthritis |
| Vibrio parahaemolyticus | Raw shellfish (oysters); watery or bloody diarrhoea |
| Clostridioides (Clostridium) difficile | Antibiotic-associated; pseudomembranous colitis; toxins A and B destroy colonic mucosa |
3. Food Poisoning / Preformed Toxin (Rapid Onset)
| Organism | Key Features |
|---|---|
| Staphylococcus aureus | Onset within 1-6 h; vomiting prominent; contaminated dairy, meats |
| Bacillus cereus (emetic type) | Onset 1-6 h; contaminated rice; preformed cereulide toxin |
| Clostridium perfringens | Onset 8-16 h; watery diarrhoea without vomiting; meat dishes |
Quick Summary Table by Type
| Type | Prototype Bacteria |
|---|---|
| Noninflammatory (watery) | V. cholerae, ETEC |
| Inflammatory (bloody/dysentery) | Shigella, EHEC, Campylobacter |
| Food poisoning (preformed toxin) | S. aureus, B. cereus |
| Antibiotic-associated colitis | C. difficile |
| Traveler's diarrhoea | ETEC (most common), EAEC |
Sources:
- Harrison's Principles of Internal Medicine 22E, Table 138-1 (Gastrointestinal Pathogens Causing Acute Diarrhoea)
- Textbook of Family Medicine 9e, Chapter 15 (Infectious Diarrhea)
- Frameworks for Internal Medicine (Invasive vs. Noninvasive Infectious Diarrhoea)
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Here is a concise summary of the bacteria causing diarrhoea:
Bacteria Causing Diarrhoea - Summary
Bacterial diarrhoea is caused through 3 main mechanisms:
Watery (Non-inflammatory) Diarrhoea
Toxin-producing bacteria acting on the small bowel:
- Vibrio cholerae - rice-water stools, severe dehydration
- ETEC (E. coli) - #1 cause of traveler's diarrhoea
- Clostridium perfringens, Bacillus cereus, Staphylococcus aureus - food poisoning (preformed toxins, rapid onset)
- Aeromonas, Plesiomonas - water/shellfish-associated
Bloody (Inflammatory) Diarrhoea / Dysentery
Invasive bacteria or cytotoxin producers affecting the colon:
- Shigella - classic dysentery, very low infectious dose
- Campylobacter jejuni - most common bacterial cause in developed countries; raw poultry; can trigger Guillain-Barre syndrome
- Salmonella - poultry/eggs; can cause typhoid fever (S. typhi)
- EHEC E. coli O157:H7 - undercooked beef; risk of HUS (hemolytic-uremic syndrome)
- Yersinia enterocolitica - pork; mimics appendicitis
- Vibrio parahaemolyticus - raw shellfish
Antibiotic-Associated
- Clostridioides difficile - post-antibiotic colitis; toxins A & B; pseudomembranous colitis
One-liner: Watery = toxin (Cholera, ETEC); Bloody = invasion (Shigella, Campylobacter, Salmonella, EHEC); Post-antibiotic = C. difficile.
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