A Comparative Analysis of Antimicrobial Resistance Patterns and Genes in Staphylococcus aureus From Humans and Animals in Veterinary Clinics Across Thailand.

Background: Antimicrobial resistance (AMR) in Staphylococcus aureus (S. aureus) poses critical public health challenges by limiting treatment efficacy and elevating morbidity, mortality, and healthcare costs. Methods: This study examined the prevalence and characteristics of AMR in S. aureus isolated from humans (veterinarians, veterinary assistants, and pet owners) and animals (dogs and cats) in veterinary clinics across five provinces in Thailand. A total of 882 samples were collected from which 188 S. aureus isolates were recovered and subjected to antimicrobial susceptibility testing and resistance gene detection. Results: Substantial variations in AMR profiles were observed across host categories, with veterinarians and veterinary assistants exhibiting higher resistance rates than pet owners. The β-lactam resistance gene blaZ was prevalent in all groups, whereas mecA was predominantly detected in veterinarians and dogs, emphasizing the occupational risk and zoonotic transmission potential. The aminoglycoside resistance gene aacA-aphD was common in cats, and quinolone resistance genes gyrA and grlA were identified in veterinarians and dogs. Macrolide resistance genes msrA and ermA, lincosamide resistance gene linA, and tetracycline resistance gene tetK were widely distributed across the groups. Agr typing of S. aureus isolates revealed diverse group distributions, with agr group I was predominant in human samples and associated with the highest AMR gene expression, while agr group III was most prevalent in animal samples and also exhibited elevated AMR gene expression within that group. Conclusions: This study underscored the diverse distribution of AMR genes, with veterinarians and veterinary assistants facing higher occupational risks. The findings highlighted the importance of integrated antimicrobial stewardship and surveillance within a One Health framework to mitigate the spread of AMR in veterinary and community settings.