Typing of HVR, Frequency of blaZ, and Detection of mecA Promoter Mutations in Clinical Isolates of Methicillin- Resistant Staphylococcus aureus

Methicillin resistant Staphylococcus aureus (MRSA) strains are a major contributor to the development of hospital- and community-acquired infections. The aim of this study was to evaluate the polymorphism of mecA gene, frequency of blaZ gene, and detection of mecA promoter mutations in clinical isolates of methicillin-resistant S. aureus strains. Materials & Methods: Susceptibility of 85 S. aureus clinical strains to methicillin was evaluated using disc diffusion method. The polymorphism of mec-associated hypervariable region (HVR), presence of blaZ genes, and mutation in mecA promoter were determined by PCR and sequencing. Findings: A total of 40 (47.1%) out of 85 S. aureus isolates were identified as methicillin resistant by phenotypic assays and PCR-based detection of mecA gene in MRSA strains. Seven different groups of repeats were found among these strains. Also, 39 MRSA strains harbored blaZ gene, and according to the sequence analysis of mecA promoter, R226S mutation was identified in 1 out of 10 isolates tested. Conclusion: According to the obtained results, there was a high variation in the polymorphic region of mecA gene in clinical isolates of S. aureus. In addition, it was appeared that betalactamase enzyme production and antibiotic hydrolysis played an important role in the occurrence of resistance to beta-lactam antibiotics, and the effect of mutation in genes regulating mecA gene expression was negligible.