Antimicrobial resistance of coagulase-positive Staphylococcus isolated from healthy Crioulo horses and associated risk factors

Abstract Antimicrobial resistance (AMR) is a global concern that must be addressed from a one health perspective. Horses are companion animals and their contact with humans facilitates exchange of resistant bacteria. This study aimed to evaluate AMR of coagulase-positive Staphylococcus (CoPS), including Staphylococcus aureus, isolated from healthy Crioulo horses. Swab samples from nostrils (n = 214) and skin (n =107) of 107 horses from Porto Alegre, South Brazil, were used for CoPS isolation. The isolates were evaluated for AMR and a multivariate logistic regression was applied to identify the risk factors associated to this outcome, using information on horses’ management and installations where they were maintained. A total of 143 CoPS was isolated from 79 horses (73.8%), of which 8 (5.6%) were S. aureus. The isolates showed resistance to seven of ten tested antimicrobials and 38.5% (55/143) of them were resistant to at least one antimicrobial. One isolate (0.7%; 1/143) was classified as multidrug-resistant. Regarding S. aureus, 62.5 % (5/8) showed AMR, but none was methicillin-resistant. The risk factors associated with CoPS’ antimicrobial resistance were lower frequency of bed changing (OR = 6.40; P = 0.001) and non-accumulation of bed materials (OR = 3.47; P = 0.002). The results point that healthy horses have antimicrobial-resistant CoPS and S. aureus in their microbiota, which may be of concern for animal and human health. Moreover, bed management was associated with AMR, which can serve as a guide for best practices to be adopted to avoid the occurrence of resistant bacteria in these animals.