Staphylococcus aureus is an important human bacterial pathogen causing wide range of diseases both by nosocomial and community-acquired infections. The organism produces a number of virulent toxins and proteins which are responsible for serious infections damaging host cells and tissues thereby involving in pathogenesis. Due to the continuous use of antibiotics, the organism show resistant to most of the available antibiotics and thereby creating a major problem and threaten to human and public health. In this present study, six S. aureus strains and clinical isolates (S1, S2, C1, C2, S2 Mut and MTCC 737) were compared for the antibiotics susceptibility test in which all the strains were found to be resistant to one of the most important antibioticsvancomycin. Plasmid curing analysis was done to know if the antibiotic resistance was plasmid-mediated or chromosome-mediated. The result showed the presence of zone of inhibition even after treating the strains with acridine orange thus inferring it as chromosome mediated. The strains were assayed for the activity of three important virulence factors produced by the organism such as protease, lipase and biofilms by plate assays which have specific roles in causing disease in host. The results showed that among the six tested strains the clinical isolate C1 and MTCC strain were found to be more virulent since all the three studied virulence factors lipase, protease and biofilm were produced in them when compared to other strains S1, S2 C2 and S2 mut. © Copyright protected.