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Bulletin No. 21 - Spring 2005
BacterologyEscherichia coli & Clostridium dificile / perfrigens
VERNOZY-ROZAND C.
Clinique, pathogénie et épidémiologie des infections à Escherichia coli producteurs de Shiga toxines (STEC) [Clinical, pathogenic and epidemiological data on Shiga toxin-producing Escherichia coli infections]
Bulletin de l'Académie Vétérinaire de France, 2004, Volume 157, Nº2, 5-16
Escherichia coli O157:H7 infections in humans are reviewed in a comprehensive way. This E. coli strain produces Shiga-like toxins (Stx) and is now commonly called STEC (Shiga-toxin producing E. coli). In humans, STEC infection most frequently result in hemorrhagic enteritis but can be complicated by a uremic hemolytic syndrome (UHS) in children or a thrombotic thrombocytopenic purpura (TTP) in adults. Several examples of outbreaks due to STEC are reported. Pigs are a particular case since they are the only animals that are susceptible to Stx causing edema disease. As a first step E. coli adheres to intestinal villi and colonizes the digestive tract. Then, the bacteria produce toxins that penetrate the intestinal epithelium, reach the blood system and damage the vessel endothelium, causing edema disease in pigs. Shiga-like toxins have been classified into two classes, Stx1 and Stx2. The Stx2 class is the most pathogenic and comprises five variants (Stx2, Stx2c, Stx2d, Stx2e, Stx2f). The Stx2e variant is almost exclusively found in STEC strains isolated from pigs. Cattle and sheep are the main reservoirs of STEC and their meat result more frequently contaminated by STEC than pork. The persistence of STEC is due to the continuous load of bacteria provided by animal feces and their high resistance in the environment. The contamination of soil and ground water may be followed by that contamination of feed and drinking water.
