ABSTRACT
The prevalence of Methicillin Resistant S. aureus [MRSA] strains with reduced susceptibility to vancomycin among local nosocomial isolates from Mansoura University Hospitals and their susceptibilities to various antibiotics were determined. A 957 clinical samples from nosocomial infections patients collected over 6-month periodduring 2004yielded'203 S. aureus isolates [21.21%], out of which 66 [34.7%] were identified as MRSA. MRSA isolates were tested for any reduced susceptibility to vancomycin by different methods. No VISA or VRSA strains were detected by either disc diffusion method or ability to grow on BHI agar containing 6 ug/mL. Among the nine potential hVISA isolates [13.6%] that could grow on BHI agar containing 4ug/ml of vancomycin, five could be identified by the Macro E-test hVISA. However, the population analysis tests confirmed only 3 [4.5%] of these isolates as hVISA. Transmission electron micrographs of one hVISA isolate demonstrates thickened cell wall as a possible mechanism of resistance