Isolation of mecC Gene carrying Methicillin Resistant Staphylococcus aureus in Clinical Samples from a Tertiary Care Institute, Northern India

Introduction: mecC Methicillin Resistant Staphylococcus aureus (MRSA) after its initial recovery in 2007 has been reported with varying frequency from different parts of the world. These isolates assume importance due to the fact that with routine testing platforms available for the detection of MRSA they can be misidentified as being methicillin sensitive which can adversely affect the treatment and outcome of infections due to MRSA harbouring the mecC gene. Aim: Evaluation of mecC gene carrying MRSA in clinical isolates. Materials and Methods: This retrospective study was conducted in the Department of Microbiology, Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India for a period of three months (May-July 2020). A total of 102 laboratory confirmed isolates of MRSA (based on biochemical tests and cefoxitin disc diffusion results) were subjected to screening for the presence of mecA and mecC gene by Polymerase Chain Reaction (PCR). Deoxyribonucleic Acid (DNA) was extracted using an in house extraction method following which mecA and mecC were amplified in a total reaction volume of 25 mu L using 2x PCR master mix, 5 mu L of template and 1 mu L (0.4 mu M final concentration) each of reverse and forward primers specific for the above mentioned genes. Statistical analysis was done using Statistical Package for the Social Sciences (SPSS) software v24.0. Results: All the isolates were confirmed as being methicillin resistant with 96.1% isolates carrying the mecA gene and 3.9% carrying the mecC gene. mecC MRSA were recovered from pus, swab and endotracheal tip in middle aged men. One of the patient from whose sample mecC MRSA was recovered was suffering from hypertension, diabetes and renal faliure. MRSA exhibited high resistance to all the antimicrobial agents tested however all of them were sensitive to vancomycin and linezolid. Conclusion: The presence of mecC gene in clinical isolates of MRSA is a cause of concern and calls for an extensive and continuous surveillance of such isolates as they can in future be implicated in causing severe human infections.