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 blaCTX-M belonging to group 1. blaCTX-M-15/28 was the predominant type, and it was associated with plasmids of several different inc/rep types. In addition, blaCTX-M-1 and blaCTX-M-3 were also detected. Plasmids encoding the blaCTX-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 blaCTX-M carrying plasmids were positive by polymerase chain reaction for an ISEcp1-like element.