Antibiotic Resistance Patterns of <i>Staphylococcus aureus</i> Isolates from Two Healthcare Facilities in Qazvin, Iran: A Retrospective Study

Abstract

Background: Staphylococcus aureus is a common cause of healthcare-associated infections. The increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) has reduced treatment options and remains a major challenge for infection control. Local surveillance of antimicrobial resistance is necessary to guide empiric therapy and support antibiotic stewardship. Objectives: This study evaluated the antimicrobial resistance patterns of S. aureus clinical isolates collected from two tertiary healthcare facilities in Qazvin, Iran, and determined the prevalence of MRSA. Methods: This retrospective, descriptive-analytical, cross-sectional laboratory surveillance study included 565 S. aureus isolates collected from hospitalized patients at Bou-Ali Hospital and Velayat Center between 2021 and 2024. Isolates were identified using standard microbiological methods. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method in accordance with the Clinical and Laboratory Standards Institute (CLSI) 2020 guidelines. Cefoxitin resistance was used as a phenotypic marker for MRSA. Molecular confirmation by mecA or mecC detection was not performed. The antimicrobial panel included cefoxitin, gentamicin, clindamycin, ciprofloxacin, erythromycin, trimethoprim-sulfamethoxazole, penicillin, and doxycycline. Inducible clindamycin resistance was not evaluated because D-testing was unavailable. Statistical analyses were performed using SPSS version 27. Associations were assessed using the chi-square test, and temporal trends were assessed using the Cochran-Armitage trend test. Results: MRSA accounted for 24.4% of all isolates (138/565, 95% CI: 20.9%–28.0%). Blood cultures were the most common specimen source (30.6%), followed by wound swabs (23.5%), urine (13.0%), sputum (10.1%), respiratory secretions (9.7%), and other clinical specimens (12.9%). Resistance was highest to penicillin (96.1%), erythromycin (61.1%), clindamycin (57.4%), and ciprofloxacin (55.1%), whereas gentamicin showed the lowest resistance rate (8.0%). Wound isolates exhibited higher resistance to ciprofloxacin (66.1%), erythromycin (69.0%), and trimethoprim-sulfamethoxazole (45.2%) than isolates from other specimen types. Significant differences between hospitals were observed for erythromycin (P = 0.004) and trimethoprim-sulfamethoxazole (P < 0.001). Compared with methicillin-sensitive S. aureus (MSSA), MRSA isolates showed significantly higher resistance to ciprofloxacin, erythromycin, gentamicin, and trimethoprim-sulfamethoxazole (all P < 0.05). Resistance to erythromycin and trimethoprim-sulfamethoxazole also differed significantly by specimen source. No significant temporal changes in resistance were detected over the study period. Conclusions: MRSA remains common among hospitalized patients in the participating healthcare facilities. High resistance to several commonly prescribed antibiotics underscores the need for continued surveillance, evidence-based antimicrobial stewardship, and regular review of empiric treatment protocols.