Study of vancomycin susceptibility in methicillin-resistant Staphylococcus aureus isolated from clinical samples

Background : Staphylococcus aureus is one of the most commonly isolated organisms in nosocomial infections. While the prevalence of methicillin--resistant Staphylococcus aureus (MRSA) continues to increase worldwide, there is a concern about an increase in vancomycin minimum inhibitory concentrations (MIC,s) among S. aureus strains. An attempt was, therefore, made to study vancomycin susceptibility in 156 MRSA isolates from various clinical samples during the period of February 2008 to January 2009. Materials and Methods: A total of 156 isolates of S. aureus were collected from various clinical specimens. MIC of vancomycin was detected by agar dilution method. Results : Out of 156 MRSA isolates all were susceptible to vancomycin by disc diffusion method. By agar dilution method, 138 isolates were susceptible to vancomycin (VISA MIC 0.5-2 mu gm/ml) and 18 isolates showed intermediate susceptibility to vancomycin (VISA MIC 4-8 mu gm/ml). No vancomycin resistant S. aureus (VRSA) with MIC >= 16 mu gm/ml was detected. Conclusion : The present study reveals the emergence of MRSA with reduced susceptibility to vancomycin and indicates the magnitude of antibiotic resistance in and around Davangere.