Enterotoxigenic Escherichia coli: Scientific letter

Abstract

Enterotoxigenic Esherichia coli (ETEC) is a major cause of diarrhea in infants and tourists in underdeveloped countries. It is transmitted by ingestion of contaminated food and water. Enterotoxigenic E. coli produces a heat-labile toxin (LT) and a heat-stable toxin (ST). The genes of these toxins are encoded by plasmids. The disease requires colonization of bacteria and elaboration of one or more enterotoxins. The bacteria colonize the gastrointestinal tract by means of a fimbrial adhesin, i.e. colonization factor Antigen I and II (CFA I and CFA II). ETEC is a noninvasive pathogen. The LT enterotoxin is very similar to cholera toxin. It binds to the same intestinal receptors. Enzymatic activity of LT is identical to that of the cholera toxin. While LT causes an increase in cyclic AMP in the host cell, ST increases cyclic GMP levels in the host cell cytoplasm. Cellular cyclic AMP and GMP lead to increased secretion of electrolytes and fluid, which results with diarrhea without fever. ETEC infection is diagnosed by determination of toxins in stool samples. Oral rehydration therapy is often lifesaving in children. Most patients recover with appropriate supportive therapy. Antibiotics are usually not required. ETEC infection can be prevented by avoiding foods and beverages that may be contaminated with bacteria. Adults in endemic areas evidently develop immunity. Toxin- and CFA-based vaccines are the major tools for immunization.