Methicillin-resistant Staphylococcus aureus (MRSA) is still recognized as one of the most important nosocomial pathogens. These isolates are usually resistant to all currently available β-lactam antibiotics (penicillins, cephalosporins and carbapenems). Vancomycin has historically been the drug of choice and sometimes the last resort for the treatment of serious MRSA infections, providing empirical coverage and definitive therapy. However, its increased use has now become questionable. Moreover, its increased use has already led to emergence of vancomycin-intermediate S. aureus (VISA) as well as vancomycin-resistant S. aureus (VRSA) in certain parts of the world.
In the early 1990s, MRSA was reported to account for 20 – 25 % of S. aureus isolates in hospitalized, worldwide. By the middle of the current decade, many hospitals experienced MRSA percentages in the range of 50-70% of total S. aureus isolates from clinical cultures. Recent studies have found that an increasing proportion of hospital-onset invasive MRSA infections are caused by community strains. The clinical scenario has been more dramatic by MRSA colonization which increases the risk of infection, and infecting strains match colonizing strains in as many as 50–80% of cases. Methicillin-resistant Staphylococcus aureus may persist within the hospital environment for a long time, complicating attempts of eradication. Besides, colonization is not static, as strains have been found to evolve and even to be replaced within the same host. Poor infection control measures as well as continues and indiscriminate use of antibiotics have resulted in this huge problem of acquisition and dissemination of MRSA.