**2.2 Vancomycin resistant** *S. aureus*

Vancomycin is a glycopeptide antibiotic which has been used as the first line drug in the treatment of MRSA infections. It was introduced for human use in late 1958 [13] and resistance to Vancomycin was reported in *Enterococci* by 1980s. Thereafter slowly *S. aureus* showed reduced susceptibility to Teicoplanin (structurally similar to Vancomycin) in European countries [14]. The first VRSA (Vancomycin Resistant *S. aureus*) was identified in 2002, in Michigan, USA. In the same year, total 52 isolates carrying Van gene were identified in USA, India, Iran, Pakistan, Brazil and Portugal [15]. *S. aureus* having reduced susceptibility to Vancomycin is classified into 3 groups based on the MIC value by CLSI as follows [16]:

1.Vancomycin Susceptible *S. aureus* (VSSA) with MIC ≤2 μg/ml

2.Vancomycin Resistant *S. aureus* (VRSA) with MIC ≥16 μg/ml

3.Vancomycin Intermediate *S. aureus* (VISA) with MIC 4-8 μg/ml
