Infectious enterocolitis
- Topic
Germs cause diarrhoea either by making toxins that pump water out, or by invading and inflaming the bowel so blood and pus appear.
What it is
Infectious diarrhoea kills over a million people a year worldwide, half of them children under five. Pathogens vary with age, nutrition, immunity, geography and clean water. Mechanistically there are two broad groups: non-invasive, toxin-producing organisms that cause watery secretory diarrhoea with almost normal biopsies, and invasive or cytotoxic organisms that injure the mucosa and cause dysentery. Acute self-limited colitis keeps the crypt architecture, which separates it from inflammatory bowel disease.
Main bacterial enteric pathogens
| Organism | Usual source | Mechanism | Typical stool | Key complication |
|---|---|---|---|---|
| Vibrio cholerae | Contaminated water, shellfish | Toxin raises cAMP | Rice-water | Dehydration, shock |
| Campylobacter jejuni | Undercooked poultry, raw milk | Motility, adherence, toxins, sometimes invasion | Watery, sometimes bloody | Guillain–Barré, reactive arthritis |
| Shigella | Person to person, low dose | Invades via M cells; Shiga toxin (S. dysenteriae 1) | Bloody | Reactive arthritis, HUS |
| Non-typhoidal Salmonella | Eggs, poultry, meat, milk | Invades epithelium and M cells | Watery or bloody | Bacteraemia in vulnerable hosts |
| Salmonella Typhi | Human carriers, water | Systemic spread via Peyer patches | Bloody diarrhoea or constipation | Perforation, carrier state |
| Yersinia | Pork, raw milk, water | Invades Peyer patches | Variable | Pseudo-appendicitis, erythema nodosum |
| E. coli (EHEC O157:H7) | Undercooked beef, produce | Shiga-like toxin | Bloody | Haemolytic uraemic syndrome |
| Clostridioides difficile | Hospital, after antibiotics | Toxins A and B | Watery | Pseudomembranous colitis, toxic megacolon |
Clinical notes
- Oral rehydration is the life-saving treatment for most acute watery diarrhoea.
- Acute diarrhoeal disease remains a leading cause of illness in Colombian children under five, where viral, bacterial and parasitic agents all contribute.
Test yourself
Think of the answer, then tap the question to see it.
Which histological feature separates acute infectious colitis from inflammatory bowel disease?
Preserved crypt architecture; IBD shows crypt distortion and basal plasmacytosis from chronic injury.
Which two organisms cause watery diarrhoea without invading the mucosa?
Vibrio cholerae and enterotoxigenic E. coli (also norovirus, rotavirus, Giardia).
Which post-infectious complication links Campylobacter with the nervous system?
Guillain–Barré syndrome, through antibodies cross-reacting with nerve gangliosides.
Elsewhere in DurgiPedia
- Water and electrolyte absorption and how diarrhea happens
- Immunity to microbes: which arm defends against what
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Diarrhoeal disease (World Health Organization, 2024); Etiology of acute gastroenteritis among children less than 5 years of age in Bucaramanga, Colombia: A case-control study (PLoS neglected tropical diseases, 2020); Viral Gastroenteritis (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.