Objective: This study was conducted to update the prevalence of methicillin-resistant S. aureus (MRSA) isolates among human clinical S. aureus isolates recovered from Northern Palestine, to evaluate the possible presence of vancomycin-Resistant S. aureus (VRSA) and vancomycin- intermediate resistant S. aureus strains (VISA) and to determine the antimicrobial susceptibilities of these clinical isolates.
Methods: The in-vitro activities of 11 antibiotics against 204 non-duplicate S. aureus isolates from clinical samples in North of Palestine were determined by the disk-diffusion method. These samples were isolated between June 2006 and December 2007. The minimum inhibitory concentration (MIC) of vancomycin for 115 methicillin resistant Staphylococcus aureus (MRSA) strains was carried out using the agar dilution method.
Results: One hundred and fifteen (56.4%) of these isolates were MRSA and according to their antibiotic profile these are multidrug resistant (resistant to three or more non-β-lactam antibiotics). Ninety nine (43.6%) isolates were methicillin sensitive S. aureus (MSSA), forty four of MSSA isolates (44.4%) were multidrug resistant, while forty five (45.6%) were non multidrug resistant. Our results showed that the most common resistance (95.6%) was to penicillin. Two strains of MRSA have shown to be vancomycin- intermediate resistant, had MIC 4 and 8 μg/ml and these vancomycin- intermediate resistant S. aureus strains (VISA) are resistant to all antibiotics tested.
Conclusion: According to our information this is the first study report about VISA in Palestine.