Diversity of CTX-M-positive Escherichia coli recovered from animals in Canada

Abstract Historically, extended-spectrum cephalosporin resistance in bacteria from animals in Canada has been attributed to the SHV and CMY β-lactamase families. This pattern is beginning to change with the emergence of the bla CTX-M gene family among Escherichia coli recovered from various animal species. Here we analyze and compare whole genome sequences of bla CTX-M -positive E. coli isolates (n = 173) from dogs, chicken, swine, horses and beef cattle in Canada. Ten bla CTX-M variants were identified with bla CTX-M-1,-14, -15, -27 and bla CTX-M-55 being identified in most animal species. These variants occurred across many sequence types, suggesting that mobile genetic elements mediate the spread of bla CTX-M . The variants bla CTX-M-14, -15, -27 and bla CTX-M-55 are associated with the global spread of bla CTX-M in human clinical isolates and their presence could be indicative of transfer between humans and animals. These variants were also the principal variants identified among sequence type 131 isolates, which were not associated with any other species than dogs. These isolates carried the same bla CTX-M variants as E. coli isolates found in humans. Close contact may promote the transmission of these isolates between humans and companion animals.