Accurate detection of methicillin-resistant Staphylococcus aureus in day to day practice: a great help to clinicians

Methicillin-resistant Staphylococcus aureus (MRSA) infections are difficult and expensive to treat, therefore early detection is essential to avoid treatment failure. Several phenotypic and genotypic methods are used to detect MRSA; however, the method of choice remains problematic. For detection of MRSA we have evaluated 3 different phenotypic methods with the genotypic method ie, polymerase chain reaction (PCR). Detection of mecA gene by PCR is a gold standard for detection of MRSA strains. Methicillin resistance was detected in 280 clinical Staphylococcus aureus isolates by PCR, oxacillin (1 microg) disc diffusion (ODD), oxacillin screen agar (OSA), and cefoxitin (30 microg) disc diffusion (CDD) methods. Out of 280 Staphylococcus aureus strains 145 (51.8%) were mecA gene positive PCR. Sensitivity and specificity of the ODD, OSA and CDD methods were detected as follows: 97.2% and 95.9%, 100% and 94.8%, and 97.8% and 100%, respectively, when compared to PCR for mecA gene. Amongst all 3 phenotypic methods, cefoxitin disc diffusion (CDD) method was best correlated with mecA-PCR. CDD methods could be a good choice for detecting methicillin resistance in S aureus strains in day to day practice where mecA PCR cannot be performed.