Detection and characterization of pCT-like plasmid vectors for blaCTX-M-14 in Escherichia coli isolates from humans, turkeys and cattle in England and Wales

Objectives - To detect and characterize Escherichia coli strains and pCT-like plasmids implicated in the dissemination of the CTX-M-14 gene in animals and humans, in England and Wales. Methods UK CTX-M-14-producing E. coli (n¿=¿70) from cattle (n¿=¿33), turkeys (n¿=¿9), sheep (n¿=¿2) and humans (n¿=¿26) were screened using multiplex PCR for the detection of a previously characterized plasmid, pCT. Isolates found to be carrying two or more pCT genetic markers were further analysed using PFGE. Their antimicrobial-resistance genes and virulence genes were also determined. These plasmids were transferred to Salmonella enterica serotype Typhimurium 26R and further examined for incompatibility type, genetic environment of the blaCTX-M-14 gene, size, restriction fragment length polymorphism (RFLP) and nikB sequence. Results - The 25 E. coli isolates carrying pCT genetic markers generated 19 different PFGE profiles, and 23 isolates had different virulence and antimicrobial-resistance gene patterns. One isolate from cattle was a verotoxigenic E. coli (‘VTEC’); the rest were commensal or extra-intestinal pathogenic E. coli. pCT-like plasmids with similar molecular characteristics (size, replicon type, RFLP pattern, pCT markers and genetic environment of the blaCTX-M-14 gene) were detected in 21/25 of the field isolates, which comprised those from cattle (n¿=¿9), turkeys (n¿=¿8) and humans (n¿=¿4). All pCT-like plasmids were conjugative, and most were IncK (n¿=¿21) and had the same local genetic environment flanking the blaCTX-M-14 gene (n¿=¿23). RFLP analysis demonstrated =75% similarity among most plasmids (n¿=¿22). Conclusions - pCT-like plasmids were common vectors for horizontal dissemination of 30% of the blaCTX-M-14 genes t