Enterotoxigenic E. coli Infection

Enterotoxigenic Escherichia coli (ETEC) causes secretory diarrhoea through colonisation factors and heat-labile (LT) and heat-stable (ST) enterotoxins.

• It is the leading cause of travellers' diarrhoea and a major cause of watery diarrhoea in children under 5 years in low income settings.
• Spread is faecal-oral via contaminated water and food; the infective dose is high (10^6 to 10^8 organisms).
• Incubation is 1 to 3 days.

Sudden watery diarrhoea without blood, abdominal cramps, nausea, low grade or no fever, lasting 3 to 5 days.

• Severe cases mimic mild cholera with rapid dehydration.
• Differential diagnosis: cholera, rotavirus, norovirus, other diarrhoeagenic E coli, Giardia, Cryptosporidium, Cyclospora, food poisoning.
• Complications: dehydration with hypokalaemia and acidosis, malnutrition and growth faltering in children, rarely persistent diarrhoea, and post-infectious irritable bowel syndrome.

Clinical in most cases; electrolytes and creatinine if dehydrated.

• Stool PCR for LT and ST genes; ordinary culture cannot distinguish ETEC from commensal E coli.
• Exclude cholera and invasive pathogens in outbreaks or severe illness.

Supportive

• Oral rehydration with low osmolarity solution, 50 to 100 mL/kg over 4 hours then replacement of losses; Ringer lactate for severe dehydration.
• Continue feeding. Zinc in children: 20 mg daily for 10 to 14 days (10 mg under 6 months).

Pharmacological

• Antibiotics shorten illness by about a day and are used for moderate to severe disease or travellers.
• Azithromycin 1 g single dose (or 500 mg once daily for 3 days; children 10 mg/kg once daily for 3 days).
• Rifaximin 200 mg three times daily for 3 days (non-invasive, age 12 years and over).
• Ciprofloxacin 500 mg twice daily for 3 days where resistance is low.
• Loperamide 4 mg then 2 mg after each loose stool (maximum 16 mg daily) in adults.
• Prophylaxis during high risk travel: rifaximin 200 mg once or twice daily (for up to 14 days), not routinely recommended.

Special groups: pregnancy (azithromycin), children (avoid fluoroquinolones except in dysentery or multi-drug resistant illness).

Red flags: severe dehydration, blood in stool (consider alternative pathogen), age under 6 months.

Follow-up: none for mild illness; safe water and food hygiene; oral cholera vaccine where cholera is co-endemic offers partial ETEC cross protection.