Prevalence and antimicrobial susceptibility pattern of methicillin-resistant, vancomycin-resistant, and Panton-Valentine leukocidin positive Staphylococcus aureus in a tertiary care hospital Dhaka, Bangladesh

ObjectivesTo observe the prevalence of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant S. aureus (VRSA), and Panton-Valentine leukocidin (PVL)-positive S. aureus, this study was carried out in a tertiary care hospital in Dhaka, Bangladesh.Materials and methodsS. aureus strains were recovered from 200 postoperative wound swab samples from patients hospitalized in Dhaka Medical College Hospital between July 2011 and June 2012. Methicillin resistance was determined by the oxacillin and cefoxitin disc diffusion method, the minimum inhibitory concentration (MIC) of oxacillin, and mecA gene detection. VRSA resistance was determined by the disc diffusion method, the MIC of vancomycin, and screening for the vanA and vanB genes. The PVL gene was also detected in MRSA strains.ResultsFifteen of the 44 isolated strains of S. aureus were MRSA (2 of them were VRSA) and 29 were methicillin-sensitive S. aureus. All MRSA isolates were highly resistant to oxacillin (MIC ≥ 256 μg/mL). When compared with polymerase chain reaction (PCR), the sensitivity and specificity of the oxacillin disc diffusion method were 93.33% and 100% respectively; for the cefoxitin disc diffusion method and MIC of oxacillin both the sensitivity and specificity were 100%. Four (26.67%) MRSA isolates were positive for PVL genes which were also mecA positive. The MRSA strains were highly resistant to ciprofloxacin (93.33%), ceftriaxone (86.63%), azithromycin (73.33%), gentamycin (73.33%), and amoxiclav (66.67%). All (100%) MRSA strains were sensitive to linezolid and 86.67% were sensitive to vancomycin. The VRSA strains had an MIC ≥256 μg/mL for vancomycin and were positive for the vanB gene but negative for the vanA gene.ConclusionThe results of this study provide insight into the high proportion of MRSA and presence of VRSA in Bangladesh.