Background: Methicillin-resistant Staphylococcus aureus (MRSA) continues to pose a formidable challenge to clinicians and infection-control practitioners across the globe owing to its resistance to most beta-lactam antibiotics, the production of an array of virulence factors, and its propensity for both healthcare- and community-associated dissemination. Reliable and rapid detection of MRSA is critical for guiding therapy and instituting timely infection-prevention measures. Objective: The present investigation was designed to determine the prevalence of MRSA among clinical S. aureus isolates, to compare phenotypic methods of MRSA detection (cefoxitin disc diffusion and oxacillin screen agar) with molecular detection of the mecA gene by polymerase chain reaction (PCR), and to characterize the antibiotic susceptibility profile of MRSA isolates. Methods: A prospective study was carried out over fourteen months (February 2012 to March 2013) at a 1,200-bedded tertiary care teaching hospital in South India. A total of 412 non-duplicate S. aureus isolates obtained from various clinical specimens were subjected to phenotypic MRSA detection using the 30 μg cefoxitin disc, oxacillin screen agar, and chromogenic MRSA agar. All isolates were further analyzed by conventional PCR targeting the mecA gene. Antibiotic susceptibility testing was performed by the Kirby–Bauer disc diffusion technique following CLSI 2024 recommendations. Results: Of the 412 S. aureus isolates evaluated, 168 (40.8%) were identified as MRSA. The cefoxitin disc diffusion method demonstrated a sensitivity of 98.8% and specificity of 99.6% when compared with the gold-standard mecA PCR. MRSA isolates exhibited high resistance to ciprofloxacin (74.4%), erythromycin (69.6%), clindamycin (52.4%), and gentamicin (48.2%), whereas glycopeptides (vancomycin, teicoplanin) and linezolid retained 100% susceptibility. Inducible clindamycin resistance was observed in 22 isolates (13.1%).

MRSA; mecA gene; cefoxitin disc diffusion; PCR; vancomycin; antibiotic susceptibility; nosocomial infection