Toxigenic Escherichia coli and Vibrio cholerae: Classification, pathogenesis and virulence determinants

Escherichia coli and Vibrio cholerae are pathogenic bacteria commonly found in various contaminated sources and pose a major health risk, causing a range of human enteric infections and pandemics, especially among infants in Africa. Virulence and pathogenesis of these organisms is specifically based on the expression of certain virulence determinants, distinctive mucosal interactions as well as the production of enterotoxins or cytotoxins. The E. coli strains that cause human disease are generally grouped into six pathotypes based on their pathogenic mechanisms of which the enterohemorrhagic and enterotoxigenic groups have been shown to be the most severe. Of the V. cholerae pathogens, the 01 and 0139 serotypes have been identified as being toxigenic due to the CTX genetic element and V. cholerae pathogencity Island, possessed by the respective serotype. This article thus provides an overview of both the enterohaemorragic and enterotoxigenic E. coli as well as toxigenic V. cholerae, and their respective virulence genes determinants involved in pathogenicity.   Key words: Diarrhoea, Escherichia coli, pathogenicity, toxigenicity, Vibrio cholerae, virulence determinants