A Comparative Analysis of Antimicrobial Resistance Patterns and Genes in <i>Staphylococcus aureus</i> From Humans and Animals in Veterinary Clinics Across Thailand

<b>Background:</b> Antimicrobial resistance (AMR) in <i>Staphylococcus aureus</i> (<i>S. aureus</i>) poses critical public health challenges by limiting treatment efficacy and elevating morbidity, mortality, and healthcare costs. <b>Methods:</b> This study examined the prevalence and characteristics of AMR in <i>S. aureus</i> 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 <i>S. aureus</i> isolates were recovered and subjected to antimicrobial susceptibility testing and resistance gene detection. <b>Results:</b> 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 <i>bla</i>Z was prevalent in all groups, whereas <i>mec</i>A was predominantly detected in veterinarians and dogs, emphasizing the occupational risk and zoonotic transmission potential. The aminoglycoside resistance gene <i>aac</i>A<i>-aph</i>D was common in cats, and quinolone resistance genes <i>gyr</i>A and <i>grl</i>A were identified in veterinarians and dogs. Macrolide resistance genes <i>msr</i>A and <i>erm</i>A, lincosamide resistance gene <i>lin</i>A, and tetracycline resistance gene <i>tet</i>K were widely distributed across the groups. <i>Agr</i> typing of <i>S. aureus</i> isolates revealed diverse group distributions, with <i>agr</i> group I was predominant in human samples and associated with the highest AMR gene expression, while <i>agr</i> group III was most prevalent in animal samples and also exhibited elevated AMR gene expression within that group. <b>Conclusions:</b> 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.