Dissemination of the Fosfomycin Resistance Gene fosA3 with CTX-M β-Lactamase Genes and rmtB Carried on IncFII Plasmids among Escherichia coli Isolates from Pets in China

The presence and characterization of plasmid-mediated fosfomycin resistance determinants among Escherichia coli isolates collected from pets in China between 2006 and 2010 were investigated. Twenty-nine isolates (9.0%) were positive for fosA3, and all of them were CTX-M producers. The fosA3 genes were flanked by IS26 and were localized on F2:A-:B- plasmids or on very similar F33:A-:B- plasmids carrying both bla(CTX-M-65) and rmtB. These findings indicate that the fosA3 gene may be coselected by antimicrobials other than fosfomycin.