Characterization of plasmids encoding cefotaximases group 1 enzymes in Escherichia coli recovered from cattle in England and Wales.

In the study, we examined the molecular characteristics of cattle-associated Escherichia coli carrying CTX-M genes and their plasmids. Between July 2006 and July 2007, 18 E. coli were collected from cattle that were found to possess a bla(CTX-M) belonging to group 1. bla(CTX-M-15/28) was the predominant type, and it was associated with plasmids of several different inc/rep types. In addition, bla(CTX-M-1) and bla(CTX-M-3) were also detected. Plasmids encoding the bla(CTX-M) genes belonged to incompatibility groups I1, F, and A/C. Analysis of the non-beta-lactam resistance genes associated with each CTX-M-bearing plasmid demonstrated that F plasmids frequently carried a larger number of resistance genes than IncI1 plasmids, which rarely carried additional resistance genes. All bla(CTX-M) carrying plasmids were positive by polymerase chain reaction for an ISEcp1-like element.