A retrospective study on methicillin-resistant Staphylococcus spp. isolated from horses admitted to a Canadian veterinary teaching hospital between 2008 and 2018.

The goals of this retrospective study were to: determine the frequency of methicillin-resistant Staphylococcus spp. (MRS) isolated from horses admitted to an equine veterinary teaching hospital in Quebec from 2008 to 2018, investigate the patterns of antimicrobial resistance (AMR), and evaluate the distribution of MRS and methicillin-sensitive Staphyloccocus spp. (MSS) by body site. During this period, 311 Staphylococcus spp. were isolated from 273 horses and 127 of these isolates were submitted to antimicrobial susceptibility testing. Of these 127 isolates, 24 (18.9%) were MRS, and among the S. aureus (n = 76), 19 (25%) were MRS. The odds of detecting an MRS increased (25%) each year [95% confidence interval (CI) (1% to 55%), P = 0.039]. The highest frequencies of resistance were to tetracycline and gentamicin. Among the MRS isolates, 12% were susceptible to both tetracycline and gentamicin. The most frequently sampled body sites were "soft-tissues." There was no significant difference (P = 0.93) in the body site distribution of MRS and MSS isolates. Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.