Genomic and proteomic investigation of the mechanism of antibiotic resistance in methicillin resistant Staphylococcus aureus isolated from clinical samples

The study was aimed at isolating methicillin resistant Staphylococcus aureus from clinical samples and elucidating the molecular mechanism behind antibiotic resistance. S. aureus was isolated from 249 clinical samples, including wound, blood, ear swabs, pus, nasal swabs, sputum, and HVS. Also, the isolates were tested for methicillin resistance by antibiotic sensitivity assay. All the 96 MRSA isolates were subjected to DNA isolation and screening for the presence of target genes such as mecA , norA and qacA . In addition, the proteins from MRSA were analysed by SDS PAGE, 2D gel electrophoresis, MALDI-TOF analysis and structural elucidation was done. The results revealed that a total of 130 samples tested positive for S. aureus among which 96 samples were found to be methicillin resistant. Genomic analysis suggests the presence of mecA gene in 90 MRSA isolates and norA gene in the remaining 6 MRSA isolates. It is to be noted that qacA gene expression wasn’t detected in any of the 96 MRSA isolates. Finally proteomic studies revealed the presence of two distinct proteins including the zinc finger protein that is involved in β-lactamase activity. The findings of our study thus shows that mecA and norA genes and zinc finger protein are present in the S. aureus isolates leading to methicillin resistance.