Molecular characterization of Escherichia coli O157:H7 strains isolated from different sources and geographic regions

ABSTRACT

Escherichia (E.) coli serotype O157H7 is a globally distributed human enteropathogen and is comprised of microorganisms with closely related genotypes. The main reservoir for this group is bovine bowels, and infection mainly occurs after ingestion of contaminated water and food. Virulence genetic markers of 28 O157H7 strains were investigated and multilocus enzyme electrophoresis (MLEE) was used to evaluate the clonal structure. O157H7 strains from several countries were isolated from food, human and bovine feces. According to MLEE, O157H7 strains clustered into two main clonal groups designated A and B. Subcluster A1 included 82% of the O157H7 strains exhibiting identical MLEE pattern. Most enterohemorrhagic E. coli (EHEC) O157H7 strains from Brazil and Argentina were in the same MLEE subgroup. Bovine and food strains carried virulence genes associated with EHEC pathogenicity in humans.