Enterotoxigenic E.coli It is the most impoant cause of traveler's diarrhea in visitors to developing countries. Transmission is by consumption of food and water contaminated by infected human or convalescent carriers. Uncooked foods such as salads or marinated meats and vegetables are associated with the greatest risk. ETEC produce diarrhea in infants, but not commonly. There is no invasion or inflammation. The bacteria remain on the surface, where the adenylate cyclase-stimulating action of the toxins creates the flow of water and electrolytes from the enterocyte into the intestinal lumen. The mucosa becomes hyperemic but is not injured in the process. Also know: ETEC diarrhea is caused by strains of E coli that produce LT and/or ST enterotoxins in the proximal small intestine. Adherence to surface microvilli mediated by the colonizing factor (CF) pili is essential for the efficient delivery of toxin to the target enterocytes. The genes encoding the ST, LT, and the CF pili are borne in plasmids. Ref: Ray C.G., Ryan K.J. (2010). Chapter 33. Enterobacteriaceae. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.