The prevalence of vanA gene in clinical isolates of vancomycin-resistant Staphylococcus aureus in a hospital in Mazandaran, Iran

Staphylococcus aureus is one of the most important causes of infections in hospitals. Although vancomycin is often prescribed for the treatment of methicillin-resistant S. aureus (MRSA), vancomycin-resistant S. aureus (VRSA) isolates remain a major problem in hospitals. In this study, we investigated the prevalence of vancomycin-resistant S. aureus isolates and also vanA gene in these clinical isolates in a hospital in Mazandaran Province, Iran. In this cross-sectional study, a total number of 60 S. aureus samples were identified from different clinical specimens after standard biochemical and microbiological tests. Disk agar diffusion test using Kirby-Bauer method was applied for antibiotics against S. aureus isolates. The presence of vanA gene was investigated in VRSA and intermediate resistance (VISA) isolates by PCR method using specific primers. Over 40% of isolates were resistant to commonly-used antibiotics, including gentamicin (46.67%), ceftazidime (45%) and carbenicillin (43.34%). Only few, however, were sensitive to gentamicin (33.33%) and ceftazidime (35%). Vancomycin was the most effective antibiotic against S. aureus isolates (56.66% sensitivity). Eleven isolates (18.34%) were resistant (VRSA) and 15 isolates (25%) were intermediate resistance (VISA) to vancomycin. Molecular analysis of vanA gene in 11 VRSA and 15 VISA showed that 8 VRSA (72.72%) and 6 VISA (40%) isolates were positive for vanA gene. The incidence of VRSA and VISA strains, as well as the frequency of vanA gene in these isolates are high and emerging in Mazandaran hospitals. There is a need to keep the emergence and spread of these strains to a minimum level.