Distinct molecular epidemiology of resistances to extended-spectrum cephalosporins and carbapenems in Enterobacter hormaechei in cats and dogs versus horses in France.

BACKGROUND

Enterobacter hormaechei is an important pathogen in humans and animals, which, in addition to its intrinsic AmpC, can acquire a wide variety of genes conferring resistances to extended-spectrum cephalosporins (ESCs) and carbapenems (CPs). In France, human clinical outbreaks of E. hormaechei resistant to ESC or carbapenem were reported.

OBJECTIVES

To study E. hormaechei isolates from cats and dogs (=59) as well as from horses (n = 55) presenting a non-susceptible phenotype to beta-lactams in order to determine which clones, resistance genes and plasmids are circulating in France.

MATERIAL AND METHODS

E. hormaechei isolates (n = 114) were short-read sequenced and five isolates were long-read sequenced to better characterize the plasmids carrying ESC- and CP-resistance determinants. Phenotypes were characterized by antibiograms using the disc diffusion method.

RESULTS

A clear divergence in the molecular epidemiology was observed depending on the host. In cats and dogs, most of the isolates presented an overexpressed ampC gene or the blaCTX-M-15 gene carried by an IncHI2 plasmid, and eight isolates (8/59, 13.6%) presented the blaOXA-48 carbapenemase gene. Thirty-two isolates (32/59, 54.2%) belonged to the human high-risk clones ST78, ST114 and ST171. Contrarily, in horses, ESC resistance was mostly due to the blaSHV-12 and blaCTX-M-15 genes carried by an IncHI2 plasmid, and high-risk clones were rarely identified (5/55, 9.0%).

DISCUSSION

Potential selection by antibiotic use (which is on an increasing trend in France for cats, dogs and horses), the dissemination capacities of both conjugative IncHI2 plasmids and high-risk clones, and possible transfers of resistant bacteria between humans and animals strongly indicate that E. hormaechei should be closely monitored.