Frequency and Diversity of Staphylococcal Cassette Chromosome mecElements in nasally Carried Methicillin Resistant Staphylococcus Aureus of Healthcare Workers

Objective: To determine the frequency andSCC mec type of nasally carried MRSA in HCWs of a tertiary care hospital. Materials and Methods: Nasal swabs were collected from three hundred and eighty healthcare workers working in various clinical wards of Lahore General Hospital, Lahore. Identification of Staphylococcus aureus was done by observing colony morphology and mannitol fermentation on mannitol salt agar, Gram stain, catalase test and DNase test. The phenotypic resistance to methicillin was determined using Cefoxitin disk 30 µg according to CLSI guidelines. All the isolates showing Cefoxitin resistance were confirmed for the presence of mec A gene and typed for SCC mec I, II, III, IV (a, b, c, d) and V by PCR. For quality control and for the confirmation of the results, DNA sequencing was done for random isolates for all the SCC mec types recovered in the present study. Results: Out of 380 nasal samples, 89 (23.42%) cultures yielded the growth of S. aureus out of which 31 (34.83%) were MRSA. The overall frequency of MRSA among all the HCWs was 8.2%. Overall 47 SCC mec elements were found in total 29 MRSA isolates. Out of 29 MRSA isolates, 13 (44.82%) were hospital acquired, 7 (24.13%) were community acquired and 9 (31.03%) isolates had SCC mec types of both hospital acquired and community acquired origins. Conclusion: The colonized healthcare workers  harboring MRSA are being acting as mixing bowls of different SCC mec genes. Our study emphasizes the need for the formulation of regular nasal decolonization policies for effective infection control within our healthcare setups.