Methicillin-resistant Staphylococcus aureus with Reduced Susceptibility to Vancomycin in Sanprasitthiprasong Hospital
Pawana Panomket PhD*, Suthinee Thirat MD* Surasak Wanram PhD*, Rungnapa Pankla Sranujit PhD**
Affiliation : * College of Medicine and Public Health, Ubon Ratchathani University, Ubon Ratchathani, Thailand ** Department of Medical Technology, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok, Thailand
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 μg/mL. Only two MRSA isolates (2.9%) were able to grow on brain heart infusion agar supplemented with
vancomycin 4 μg/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.
Keywords : Methicillin-resistant Staphylococcus aureus (MRSA), Vancomycin, Heterogeneous vancomycin-intermediate S. aureus (hVISA), Vancomycin-intermediate S. aureus (VISA), High level vancomycin-resistant S. aureus (VRSA)
