Methicillin-resistant Staphylococcus aureus with reduced susceptibility to vancomycin in Sanprasitthiprasong Hospital.

BACKGROUND: Staphylococcus aureus is a species of bacteria that causes a number of diseases and more than 60% of it is presently resistant to methicillin. Vancomycin is the drug of choice for the eradication of methicillin-resistant S. aureus (MRSA). OBJECTIVE: This study aimed to investigate the susceptibility of heterogeneous vancomycin intermediate S. aureus (hVISA) and vancomycin intermediate S. aureus (VISA) to vancomycin by standard disk diffusion, microbroth dilution, a one-point population assay, and a population analysis profile. MATERIAL AND METHOD: Sixty-eight MRSA isolates from patients admitted to Sanprasitthiprasong Hospital between November 2010 and November 2011 were tested. RESULTS: Standard disk diffusion showed that all the MRSA isolates were susceptible to vancomycin. Vancomycin MICs for all isolates were 1-2 microg/mL. Only two MRSA isolates (2.9%) were able to grow on brain heart infusion agar supplemented with vancomycin 4 microg/mL and were confirmed by a population analysis as hVISA. CONCLUSION: This study showed the effect of vancomycin on MRSA and the need for early detection and controlled planning.