Oxacillin- and methicillinresistant S. aureus (MRSA) has been rapidly increasing in incidence. MRSA and methicillin-sensitive S. aureus (MSSA) coexist in heterologous populations. Treatment of a patient harboring this heterologous population may provide a selective environment for the MRSA. Prior to changing therapy, the susceptibility of the isolate should be determined. Vancomycin has often been used effectively for MRSA, but it is expensive and nephrotoxic. There is no evidence that MRSA is any more virulent or invasive than susceptible strains. Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition