Synopsis
Distinguish four major bacterial diarrhoeal syndromes, recognise invasive and toxin-mediated complications, select public-health testing and use antimicrobials only where benefit outweighs organism-specific harm.
- Campylobacter commonly causes fever, cramping and sometimes bloody diarrhoea after poultry, unpasteurised milk, animal or water exposure; most cases need fluids only.
- Non-typhoidal Salmonella usually produces self-limiting gastroenteritis after food or animal exposure, but bacteraemia can seed arteries, bone and prostheses.
- Shigella has a very low infectious dose and causes fever, cramps, tenesmus and small-volume bloody or mucoid stool with important person-to-person spread.
Key red flags
Bloody diarrhoea with falling platelets, fragmented red cells or rising creatinine suggests STEC-associated haemolytic uraemic syndrome.
Fever, urgency, tenesmus and frequent small-volume stool containing blood or mucus suggest invasive distal colitis and easy transmission.
Investigation priorities
Detect Campylobacter, Salmonella, Shigella and Shiga toxin genes and preserve isolates for susceptibility and public-health typing.
Management branches
An adult has bloody diarrhoea, severe cramping or epidemiological exposure compatible with STEC.
- Isolate, rehydrate and send urgent stool testing that includes Shiga toxin detection and culture.
- Avoid antibiotics and antimotility drugs until STEC is excluded or a specialist identifies a compelling alternative indication.
Key medicines
Azithromycin for selected CampylobacterGive 500 mg orally once daily for three days when severe or prolonged Campylobacter disease or host risk justifies treatment and local guidance supports macrolide therapy.
Ceftriaxone for susceptible invasive SalmonellaGive 2 g intravenously once daily for susceptible invasive non-typhoidal Salmonella when selected by infection specialists; duration depends on bloodstream clearance and seeded focus.