Mozhgan Pirmoradian, Mohsen Zargar, Razieh Nazari
Staphylococcus aureus (S. aureus) is a clinically significant opportunistic pathogen and a leading cause of healthcare-associated infections, particularly in surgical settings. This study aimed to investigate the antibiotic resistance patterns, biofilm-forming ability, and the distribution of selected virulence and resistance genes among S. aureus isolates collected from healthy orthopedic surgical personnel in Iran. A total of 63 S. aureus isolates, comprising 52 methicillin-resistant (MRSA) and 11 methicillin-susceptible (MSSA) isolates, were recovered from nasal and hand swabs. Antimicrobial susceptibility was determined by the Kirby-Bauer disk diffusion method or broth microdilution for oxacillin. Biofilm formation was quantified using the tissue culture plate assay, and resistance and virulence genes were detected by PCR. All isolates were biofilm producers, with nasal isolates representing the highest proportion of strong producers, although the difference was not statistically significant. High resistance rates were observed to penicillin and ampicillin, and erythromycin resistance was significantly associated with moderate biofilm formation. MRSA, identified by cefoxitin resistance, accounted for 82.5% of the isolates and produced significantly greater biofilm biomass compared to MSSA isolates. Among MRSA isolates, 40.4% exhibited an MDR phenotype and 1.9% were XDR, while all isolates remained susceptible to vancomycin and chloramphenicol. The mecA gene was present in all MRSA isolates, while icaA was exclusive to MRSA and strongly correlated with biofilm biomass. Three agr types were identified, with agrI predominating. The convergence of potent virulence determinants, multidrug resistance, and robust biofilm formation-particularly among MRSA isolates-underscores the potential for silent nosocomial transmission and highlights the need for enhanced infection-control practices and strengthened antimicrobial stewardship.