A comparison of human and bovine Escherichia coli O157:H7 isolates by toxin genotype, plasmid profile, and bacteriophage lambda-restriction fragment length polymorphism profile.

Foods of bovine origin have been linked to human disease outbreaks caused by Escherichia coli O157:H7 and may be linked to the more common sporadic cases as well. In this study, E. coli O157:H7 from the bovine reservoir (22 isolates: 12 from dairy and 10 from beef breed cows) and from human patients (50 isolates from sporadic human infections) were compared using Shiga-like toxin genotypes, plasmid profiles, and DNA restriction fragment length polymorphisms identified with a bacteriophage lambda probe (lambda-RFLP). Twenty-three lambda-RFLP profiles, 4 Shiga-like toxin genotypes, and 8 plasmid profiles were identified among the isolates tested. Together the typing methods distinguished 43 strains, of which 3 were isolated from both humans (5 isolates) and cattle (6 isolates; 5 from dairy herds). These data demonstrate the value of lambda-RFLP as a means of strain identification for E. coli O157:H7.