Common origin of plasmid encoded alpha-hemolysin genes in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Background  

Alpha (α)-hemolysin is a pore forming cytolysin and serves as a virulence factor in intestinal and extraintestinal pathogenic strains of E. coli. It was suggested that the genes encoding α-hemolysin (hlyCABD) which can be found on the chromosome and plasmid, were acquired through horizontal gene transfer. Plasmid-encoded α-hly is associated with certain enterotoxigenic (ETEC), shigatoxigenic (STEC) and enteropathogenic E. coli (EPEC) strains. In uropathogenic E. coli (UPEC), the α-hly genes are located on chromosomal pathogenicity islands. Previous work suggested that plasmid and chromosomally encoded α-hly may have evolved independently. This was explored in our study.