ETEC

Enterotoxigenic Escherichia coli (ETEC) is a pathovar of E. coli that causes watery diarrhea. ETEC strains are noninvasive and colonize the small intestine. They adhere via colonization factors and produce enterotoxins, notably the heat-labile toxin (LT) and heat-stable toxin (ST). LT is similar to cholera toxin in increasing cAMP; ST increases intracellular cGMP; both induce a secretory diarrheal illness. Some strains also express colonization factor antigens (CFAs) that promote intestinal attachment.

Transmission occurs via the fecal-oral route, through contaminated water or foods, and is associated with poor sanitation and crowding. Clinically, ETEC causes abrupt onset of watery, non-bloody diarrhea, often with cramps, nausea, and low-grade fever; dehydration is common, particularly in young children and travelers. Incubation is typically 1–3 days.

Diagnosis is made by isolation of ETEC from stool with confirmation of toxin genes (elt for LT, est for ST) or detection of toxins; many laboratories use multiplex PCR panels; culture alone cannot distinguish ETEC from other E. coli. Diagnosis can be challenging in settings with limited resources.

Treatment emphasizes rehydration and electrolyte replacement; zinc supplementation is recommended for children. Antibiotics may shorten illness and reduce shedding in moderate to severe cases; options include azithromycin, rifaximin, or fluoroquinolones in areas with low resistance, guided by local patterns.

Prevention focuses on safe water and food practices, sanitation, hand hygiene, and vaccination research. Several vaccine candidates are in development, including multivalent formulations targeting CF antigens and LT toxin. ETEC remains a leading cause of traveler's diarrhea and an important cause of infant diarrhea in low-income regions.