Escherichia coli

Abstract

Most E scherichia coli are a harmless inhabitant of the intestinal tract, and only a small percentage of strains are considered pathogenic. However, a recent surge in the enterohemorrhagic E. coli (EHEC), a highly virulent subset of Shiga toxin-producing E. coli (STEC) outbreaks, suggests a possible increased horizontal or vertical transfer of pathogenic genes among bacterial species. There are six virotypes of E. coli (EHEC, EPEC, ETEC, EIEC, DAEC, and EAEC), of which EHEC, EPEC, and ETEC are known to cause severe disease worldwide. Increased insight into their genetic and phenotypic properties of virulence factors and their pathogenic mechanisms should help in formulating appropriate preventive or therapeutic measures. The common themes shared by all E. coli virotypes include the following: they adhere to the epithelial cells and cause damage to the cells by initiating signaling events that lead to blockage of protein synthesis, alter the cytoskeletal structure leading to attachment and effacement lesion, affect ion pumps, increase fluid loss, or cause cell death. In recent years, however, the research focus is geared more toward EHEC group because of their continued association with serious foodborne outbreaks from a wide variety of foods, including fruits, vegetables, meats, and dairy products. Analysis of recent outbreak strains indicates association of Stx2 and Eae to be the most important virulence factor of EHEC/STEC, causing hemorrhagic colitis (HC), severe hemolytic uremic syndrome (HUS), and kidney damage. Association of this pathogen with fresh vegetables presents a serious problem because these products are minimally processed and, apparently, the processing conditions are inadequate for complete removal or inactivation. Furthermore, these organisms probably have developed strategies to utilize nutrients from plants for prolonged survival inside the plant tissues, and they are resistant to washing and disinfections. Diarrheal diseases are preventable by adopting proper sanitary condition during the preparation of food, by thorough cooking, and by avoiding foods that might be the potential source of the organism. Dehydration and electrolyte loss result from diarrhea, which can be fatal; thus, hydration is the most important therapy against diarrheal diseases. The most severely affected patients suffering from EHEC/STEC require blood transfusion and dialysis therapy.