<prompt> Most common cause of Travellers diarrhoea:Enterotoxigenic E. coliEnterohemorrhagic E. coliEnteropathogenic E. coliEnteroinvasive E. coli  <response>: ETEC are the most impoant cause of travelers diarrhea in visitors to developing countries. ETEC also produce diarrhea in infants native to these countries, where they are a leading cause of morbidity and moality during the first 2 years of life. Repeated bouts of diarrhea caused by ETEC and other infectious agents are an impoant cause of growth retardation, malnutrition, and developmental delay in third-world countries where ETEC are endemic. ETEC disease is rare in industrialized nations, although recent outbreaks suggest that it may be underestimated. Also Know: Transmission is by consumption of food and water contaminated by infected human or convalescent carriers. ETEC diarrhea is caused by strains of E coli that produce LT andor ST enterotoxins in the proximal small intestine. Strains that elaborate both LT and ST cause more severe illness. Adherence to surface microvilli mediated by the colonizing factor CF pili is essential for the efficient delivery of toxin to the target enterocytes.LT andor ST cause fluid outpouring in small intestine. Infections with ETEC can stimulate immunity. This natural immunity is presumably mediated by sIgA specific for LT and CFs. Ref: Ray C.G., Ryan K.J. 2010. Chapter 33. Enterobacteriaceae. In C.G. Ray, K.J. Ryan Eds, Sherris Medical Microbiology, 5e. 