Methicillin resistant Staphylococcus aureus (MRSA) is an important pathogen that causes hospital acquired infections recorded in the intensive care unit (ICU). Most of the MRSA isolates carry mecA gene which is a molecular marker for Methicilin resistance. There are two types of MRSA , community acquired (CMRSA) and hospital acquired (H-MRSA), both of these contain mecA gene. The Panton-Valentine Leukocidin (PVL) gene is normally present in C-MRSA infections which are now found to be widespread in hospital setting. Our objective was to assess the presence of PVL gene in mecA gene positive MRSA isolates from ICUs. This was a cross sectional study in ICUs of a tertiary care hospital over a period of 8 months (June 2013 to January 2014). Total of two hundred patients admitted in the ICUs who were suspected to have acquired infection 48 hours after admission were included in the study. By routine bacteriological examination and disc diffusion sensitivity testing with 30μg cefoxitin discs, MRSA strains were isolated. Polymerized chain reaction (PCR) was performed to detect mecA gene and PVL gene using specific primers. Cefoxitin disc diffusion screening showed 112 positive MRSA strains among which the mecA gene was detected in 104 strains and was absent in the remaining eight strains of total MRSA. Among the 104 mecA gene positive MRSA strains, 46 (44%) strains contained PVL gene. Our results indicate a higher prevalence of PVL-positive MRSA strains in the ICUs compared to many earlier studies. These strains were susceptible only to very few antibiotics and the empirical treatment options should be planned accordingly. Awareness of intensive care physicians and proper training of health care workers in the ICU could lower the magnitude of this problem.
Key words: C-MRSA, H-MRSA, ICU, mecA gene, PVL gene