A COMPARATIVE STUDY OF PHENOTYPIC AND GENOTYPIC METHODS FOR DETECTION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
Background: Methicillin resistant Staphylococcus aureus (MRSA) has been emerged as a nosocomial and community acquired pathogen worldwide. There are many challenges for laboratory detection of MRSA. The aim of this study was to compare different phenotypic methods with PCR based method as a gold standard for detection of mecA gene. Methods: A total of 158 clinical isolates of S. aureus isolated from various clinical specimens over the period of 1 year in Sharda Hospital, Greater Noida, were included in our study. Methicillin resistance was determined by cefoxitin disks, oxacillin screen agar, Automated Vitek -2 compact, results of these methods were compared with mecA gene based PCR method as a gold standard method. Results: Among 158 isolates from S. aureus, 59 (37.47%) isolates were positive for mecA gene by PCR method. Cefoxitin disk diffusion method identified 58 isolates as MRSA with mec A gene . The results of cefoxitin disk diffusion method when compared with PCR method has sensitivity of 98.3% and the specificity of 97.9%. Oxacillin agar medium has 100% sensitivity and 94.9 % specificity. Vitek-2 compact has sensitivity of 96.7% and 97.9% specificity respectively. Conclusion: Result of cefoxitin disk diffusion method with 98.3 % sensitivity and 97.9% specificity is comparatively more precise to PCR method for detection mecA gene in MRSA than any other phenotypic method. Cefoxitin disk diffusion method can be considered as an alternative phenotypic method of PCR for detection of MRSA.
Methicillin-Resistant Staphylococcus Aureus, mecA Gene, Oxacillin Screen Agar.