Survey of the antimicrobial susceptibility of Escherichia coli isolated from horses admitted to the Western College of Veterinary Medicine, Saskatoon, Saskatchewan.

Objective: Antimicrobial resistance is a serious threat in human and veterinary medicine. Among the most problematic resistant organisms are the extended-spectrum β-lactamase (ESBL)-producing Enterobacterales, which are resistant to the 3rd-generation cephalosporins. The purpose of this study was to determine the frequency of colonization of horses admitted to the Western College of Veterinary Medicine with resistant Escherichia coli.

Animals and procedure: Rectal swabs were collected from 60 horses admitted between November 2021 and March 2022. Swabs were selectively cultured for E. coli, which was identified using standard biochemical tests. The antimicrobial susceptibility of isolates was determined, and resistant isolates were screened using PCR for the presence of ESBL.

Results: Escherichia coli was isolated from all 60 horses. Although pansusceptibility was the most commonly identified phenotype, multidrug-resistant isolates possessing a CTX-M-type ESBL were recovered from 1 horse. Resistance to trimethoprim + sulfamethoxazole was the most commonly encountered resistant phenotype.

Conclusion and clinical relevance: Although resistance was uncommon, the identification of ESBL-producing isolates highlighted the importance of continued surveillance to monitor the emergence of resistance in equine populations.