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 µgm/ml) and 18 isolates showed intermediate susceptibility to vancomycin (VISA MIC 4-8 µgm/ml). No vancomycin resistant S. aureus (VRSA) with MIC ≥ 16 µgm/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.

BACKGROUND Clindamycin is an effective drug to treat Methicillin-Resistant Staphylococcus Aureus (MRSA). Reporting S. aureus as susceptible to clindamycin without checking for inducible clindamycin resistance may lead to therapeutic failure. Therefore, D-test is used to screen inducible clindamycin resistance. MATERIALS AND METHODS All the S. aureus isolates resistant to erythromycin were taken. Erythromycin (15 μg) disc and clindamycin (2 μg) disc were placed 15 mm apart on Mueller-Hinton agar plates as per CLSI guidelines and incubated at 37°C for 18-24 hours. Flattening of zone (D shape) around clindamycin was taken as D-test positive. RESULTS Out of 270 S. aureus isolates, 80 were resistant to erythromycin. D-test was positive in 29 isolates, out of which 23 were MRSA. These MRSA isolates were also resistant to most of the other routinely used antibiotics. This study showed that inducible clindamycin resistance is as high as 36.2% in erythromycin resistant S. aureus and 10.7% among S. aureus as such. CONCLUSION We conclude that this simple and effective method can be implemented for accurate identification of inducible clindamycin resistance in S. aureus to prevent treatment failure. Clinical laboratories should guide the clinicians about the inducible clindamycin resistance by performing D-test routinely and prevent misuse of antibiotics.