Occurrence of hlyA and sheA genes in extraintestinal Escherichia coli strains

The association of a hemolytic phenotype with the carriage of the alpha-hemolysin gene (hlyA) and/or the silent hemolysin gene (sheA or clyA) among 540 extraintestinal clinical isolates of Escherichia coli and 110 fecal isolates from healthy individuals was investigated. Though HlyA is an important virulence factor in extraintestinal E. coli infection, the role of SheA is not completely clarified. Two hemolytic sheA(+) E. coli strains that lacked hlyA and possessed no other hemolysin genes were identified. No hlyA(+) sheA(+) strains were identified, suggesting that there is possible incompatibility between hlyA and sheA in the chromosome of E. coli.