Resistance To Extended-Spectrum Cephalosporins In Escherichia Coli And Other Enterobacterales From Canadian Turkeys

The goal of this study was to determine the frequency of resistance to extended-spectrum cephalosporins (ESCs) inEscherichia coliand otherEnterobacteralesfrom turkeys in Canada and characterize the associated resistance determinants. Pooled fecal samples were collected in 77 turkey farms across British Columbia, Quebec, and Ontario. Isolates were obtained with and without selective enrichment cultures and compared to isolates from diagnostic submissions of suspected colibacillosis cases in Ontario. Isolates were identified using MALDI-TOF and susceptibility to ESCs was assessed by disk diffusion. The presence ofbla(CMY),bla(CTX-M),bla(TEM,)andbla(SHV)was tested by PCR. Transformation experiments were used to characterizebla(CMY)plasmids. Genome sequencing with short and long reads was performed on a representative sample ofbla(CTX-M)-positive isolates to assess isolates relatedness and characterizebla(CTX-M)plasmids. For the positive enrichment cultures (67% of total samples), 93% (587/610) were identified asE.coli, with only a few otherEnterobacteralesspecies identified. The frequency of ESC resistance was low inE.coliisolates from diagnostic submission (4%) and fecal samples without selective enrichment (5%). Of the ESC-resistantEnterobacteralesisolates from selective enrichments, 71%, 18%, 14%, and 8% were positive forbla(CMY),bla(TEM,)bla(CTX-M,)andbla(SHV), respectively. IncI1 followed by IncK were the main incompatibility groups identified forbla(CMY)plasmids. Thebla(CTX-M-1)gene was found repeatedly on IncI1 plasmids of the pMLST type 3, whilebla(CTX-M-15),bla(CTX-M-55), andbla(CTX-M-65)were associated with a variety of IncF plasmids. Clonal spread of strains carryingbla(CTX-M)genes between turkey farms was observed, as well as the presence of an epidemicbla(CTX-M-1)plasmid in unrelatedE.colistrains. In conclusion,Enterobacteralesresistant to ESCs were still widespread at low concentration in turkey feces two years after the cessation of ceftiofur use. Althoughbla(CMY-2)is the main ESC resistance determinant inE.colifrom Canadian turkeys,bla(CTX-M)genes also occur which are often carried by multidrug resistance plasmids. Both clonal spread and horizontal gene transfer are involved in parallel in the spread ofbla(CTX-M)genes inEnterobacteralesfrom Canadian turkeys.