Prevalence of vancomycin resistant Staphylococcus aureus (VRSA) in methicillin resistant S. aureus (MRSA) strains isolated from burn wound infections

OBJECTIVES The increase in resistance of methicillin resistant Staphylococcus aureus (MRSA) strains to vancomycin has been perceived as a formidable threat in the therapeutic fields. The present study investigated the vancomycin resistance traits of MRSA isolates [vancomycin resistant S. aureus (VRSA)] collected from burn patients. MATERIALS AND METHODS Twenty-nine of 40 isolates of Staphylococcus spp. were identified as S. aureus which were further tested against 20 commercially available antibiotics to determine antibiotic susceptibility patterns. RESULTS Imipenem was the most potential antibiotic resulting in 90% sensitivity, followed by netilmicin, clindamycin, and nitrofurantoin (80% sensitivity). All isolates were found to be resistant to penicillin. Approximately 75% of them were found to be resistant to methicillin, oxacillin, azithromycin, cipro-floxacin, and tetracycline. Approximately 45% isolates exhibited resistance to amikacin, chloramphenicol, gentamycin, and tobramycin. Twenty-one of the 29 strains of S. aureus were MRSA, of which 11 were resistant to vancomycin when employing the disc diffusion method. However, when the broth micro-dilution procedure was used to measure the minimum inhibitory concentration (MIC) of vancomycin, eight isolates were resistant to vancomycin, six with an MIC of 32 μg/mL and two with an MIC of 64 μg/mL. CONCLUSION A significant fraction of VRSA was found among MRSA strains in this study, revealing the necessity for new and effective drugs against MRSA.