Plasmid-borne florfenicol and ceftiofur resistance encoded by the floR and blaCMY-2 genes in Escherichia coliisolates from diseased cattle in France

摘要

This study was designed to determine the genetic basis of florfenicol and ceftiofur resistance in Escherichia coli isolates recovered from French cattle. In these isolates, ceftiofur resistance was conferred by bla CMY-2 located on three distinct conjugative plasmids on a specific DNA fragment, ISEcp1-bla CMY-2-blc-sugE. Two of the plasmids also carried the floR gene conferring resistance to florfenicol. The floR gene was shown to be associated with the insertion sequence ISCR2. Mobile elements appear to contribute to the mobilization of floR and bla CMY-2 genes in E. coli. The presence of bla CMY-2 and floR on the same plasmid highlights the potential risk for a co-selection of the bla CMY-2 gene through the use of florfenicol in food animal production.