SENSITIVITY OF PHENOTYPIC METHODS TO DETECT METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS USING MEC A GENE DETECTION BY POLYMERASE CHAIN REACTION AS GOLD STANDARD

• SONY SOMAN,*  
• SAHIRA HANEEFA,  
• MANJUSREE SURESH

Abstract

Background: It is crucial to employ precise, reliable, and rapid methicillin resistant Staphylococcus aureus detection methods to avoid the indiscriminate use of antimicrobial drugs and make informed decisions regarding appropriate treatment and the execution of efficient measures to prevent infections. Materials and Methods: A group of 112 Staphylococcus aureus isolates from different clinical specimens, initially identified as MRSA using the cefoxitin disc diffusion test, underwent additional phenotypic tests such as the Oxacillin E strip and MRSA CHROM agar. These methods were then evaluated and compared with mec A gene detection via PCR, which is regarded as the gold standard. Results: Of the 112 MRSA isolates identified by the cefoxitin disc diffusion test, 101 (90.2%) tested positive for the mec A gene. The Oxacillin E strip had a sensitivity of 98% and a specificity of 91%, while MRSA CHROM agar showed a sensitivity of 96.03% and a specificity of 82%. Among the 101 mec A-positive MRSA isolates, 44.5% met the CDC definition criteria for HA MRSA. Conclusion: Our study concludes that phenotypic methods, including the cefoxitin disc diffusion test, are not completely reliable in detecting methicillin resistance in S. aureus. According to our results, combining the cefoxitin disc diffusion test with the oxacillin E strip is an effective approach for detecting MRSA in resource-constrained settings. Given the advantages of PCR, it is recommended to perform PCR for mec A gene detection on a regular basis to identify MRSA strains in important clinical specimens.

Keywords

Methicillin -Resistant Staphylococcus aureus; Cefoxitin; mecA gene; Polymerase Chain Reaction