Prevalence and genotypic characterization of Methicillin-Resistant Staphylococcus aureus (MRSA) harboring femA and tetM in canine and feline otitis externa

This study investigated the molecular prevalence and antibiotic resistance patterns of Staphylococcus aureus in companion animals with otitis externa in Urmia, Iran. From July 2024 to May 2025, 108 ear swabs were collected from affected dogs (n = 56) and cats (n = 52). Isolates were confirmed using biochemical tests and PCR targeting 16 S rRNA and femA genes. Susceptibility testing followed CLSI standards, and PCR was used to detect mecA and tetM genes. S. aureus was identified in 18 samples (16.66%), with a higher isolation rate in dogs (19.64%) compared to cats (13.46%). Phenotypic analysis revealed alarming resistance levels, particularly in dogs against penicillin (90.91%) and tetracycline (81.8%). Molecular characterization showed that 27.77% of isolates harbored the mecA gene (MRSA), and 55.55% carried the tetM gene. A significant correlation was observed between animals aged > 4 years and the carriage of resistance genes (P < 0.05). These findings highlight a significant prevalence of MRSA and multidrug-resistant strains in the region. The high rate of beta-lactam resistance suggests that empirical therapy is no longer effective. Consequently, routine antimicrobial susceptibility testing and a One Health approach are crucial to manage these infections and mitigate zoonotic transmission risks.