The hospital epidemiology of Methicillin-Resistant Staphylococcus aureus (MRSA) has changed in the past few years due to the infiltration of community associated MRSA (CA-MRSA) strains into health care settings. A total of 100 clinical isolates of Staphylococcus aureus strains were isolated from various clinical samples, identified by standard biochemical tests. Antibiotic susceptibility testing was done by the Kirby Bauer disc diffusion method and Vancomycin screen agar (6µg/ml) was used to detect Vancomycin resistance. Patient data were collected and all the isolates were found to be hospital acquired MRSA (HA-MRSA) strains based on CDC definition. To detect mec A gene, fem A gene and pvl gene; triplex PCR was used. SCCmec typing was done by a multiplex PCR. Four different SCCmec types were detected, of which 42% of all isolates belonged to SCCmec type I (n=22) and III (13), whereas SCCmec type II was completely absent, while 39% MRSA (n=33) carried SCCmec type V. Thirty isolates (36%) carried the genes for PVL of which (67%) were strongly associated with SCCmec type V, (10%) SCCmec type I, (10%) SCCmec type III, (3%) SCCmec type IV and (17 %) were Non-Typeable. The high proportion of HA -MRSA strains carrying SCCmec types V, together with the considerable occurrence of PVL positive MRSA strains suggest strong infiltration of CA-MRSA into the hospital set up. The presence of PVLamong HA-MRSArequires further research to confirm whether PVL can be considered as a surrogate marker for CA-MRSA.
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Distribution of various SCCmec types and PVL amongst the MRSA isolates
