Why is S. aureus so virulent?
S. aureus has developed drug resistance in the usual ways: mutations in genome followed by selection of resistant strains and acquisition of virulence genes in the form of plasmids, transducing particles, transposons, or other DNA inserts. (2) Since the introduction of penicillin in the 1940s, S. aureus has been very quick to adapt to the introduction of new drugs. There are strains that have become resistant to most normal antibiotics, and there is fear that a new drugs are not on the horizon. Therefore, pharmaceutical companies are looking at drugs that would block certain molecular targets (i.e. active sites for enzyme binding) to combat the emerging resistant strains of S. aureus. (2) A plasmid associated with vancomycin resistance has been found in enterococci that can be transferred to S. aureus in the laboratory, which may occur in the Gastrointestinal tract between S. aureus and normal flora.