SNP Scanning in mecA Gene for Methicillin-Resistant Staphylococcus aureus

BACKGROUND: Staphylococcus aureus (SA) is known as an important human pathogen, which is responsible for many cases of both hospital and community-acquired infections all over the world. Studying on drug resistance is regarded as an important prevention strategy regarding these types of infections. OBJECTIVES: The current study is aimed to assess the association between the single-nucleotide polymorphism (SNP) and resistance to antibiotics in the methicillin-resistant Staphylococcus aureus (MRSA) strains as well as the molecular typing of isolates, collected from the clinical samples. MATERIALS AND METHODS: We used the disc-diffusion method to test the isolates antibiotic resistance. In addition, the genotypes of staphylococcal cassette chromosome mec (SCCmec) in the Methicillin-resistant Staphylococcus aureus isolates were determined by multiplex -polymerase chain reaction (PCR). SNP was identified in the mecA gene using sequencing and amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) method. RESULTS: The highest resistance was shown against oxacillin, and erythromycin and cephalexin. The most sensitive antibiotic was vancomycin (97%) and resistance to at least three antibiotic classes were identified in all isolates. Eighty six percent of isolates were positive for mecA gene and more than 50% of which were healthcare-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA). Moreover, SCCmec type 3, 1were the predominant strains of the identified MRSA. Also, 23 isolates (23%) were non-typable. By using the ARMS-PCR method, it was found that 10% of the clinical specimens had SNP in the mecA gene. CONCLUSION: According to the Chi-square test (χ2), it reveals that the association between SNP in the mecA gene and oxacillin, cefoxitin, and erythromycin resistance was confirmed among clinical MRSA. Furthermore, there is a 95%probability of association between SNP and resistance to more than three antibiotics in MRSA strains.