High prevalence of international ESBL CTX-M-15-producing Enterobacter cloacae ST114 clone in animals

The objective of this study was to characterize ESBL-producing Enterobacter cloacae isolated from animals and to compare their clonal distribution with that of human-related isolates.

Among 635 clinical E. cloacae from horses, dogs and cats collected in France between 2010 and 2013, 36 were resistant to ceftiofur as determined by disc diffusion. ESBL genes were identified by sequencing. Plasmids carrying ESBL-encoding genes were characterized by PCR-based replicon typing, S1-PFGE and Southern blotting. IncHI2 plasmids were subtyped using the plasmid double-locus sequence typing scheme and multiplex amplification of the hipA, smr0092 and smr0183 genes. All E. cloacae were typed by PFGE and MLST. ST clustering was analysed by eBURST.

All 36 ceftiofur-resistant E. cloacae produced an ESBL. Their PFGE patterns formed 23 clusters of high similarity and 13 STs and were isolated from epidemiologically unrelated animals (14 horses, 11 dogs and 11 cats) distributed throughout France. ST114, the most prevalent clone in humans, was over-represented in animals (16/36) compared with other human-related clones detected here. The blaCTX-M-15 gene was dominant (66.7%) and mostly carried on IncHI2 plasmids (ST1 subtype). ST114 isolates always produced CTX-M-15.

Most ESBL-producing E. cloacae from animals studied here (69.4%) belonged to potentially high-risk clones in humans, in particular ST114 (44.4%). These data raise questions and potential concerns about the transfer of E. cloacae between animals and humans.