The Prevalence of Resistance to Methicillin in Staphylococcus aureus Strains Isolated from Patients by PCR Method for Detec-tion of mecA and nuc Genes

Methicillin-resistant Staphylococcus aureus (MRSA) is the main cause of hospital infection emerged over the last decades. Rapid detection of MRSA is important for patient care and proper usage of infection control. Detection of mecA genes (encoding resistance to methicillin and other similar antibiotics) and nuc genes (encoding staphylococcal thermostable nuclease) by PCR method is now considered for rapid identification of MRSA strain. The aim of this study was to determine the prevalence of MRSA isolated from patients in Tehran, Iran by PCR method for detection of mecA and nuc genes. Phenotypic method such as microscopic and colony morphology and catalase and coagulase tests were used for identification of S. aureus isolates. DNA was extracted from all isolates and the presence of nuc and mecA gene was detected by PCR method. For determination of MRSA by phenotypic methods, oxacillin disk diffusion test were used. Data were analyzed by SPSS software. Out of 126 clinical sample identified by phenotypic method, 101 isolates had nuc gene. In disk diffusion tests by oxacillin disk, 78.2% of isolates were considered to be MRSA, but in PCR method for mecA gene, 69% isolates were positive. The results showed a high prevalence of methicillin-resistance among S. aureus isolates. Identifying MRSA strains, isolating MRSA-positive patients and carrier’s treatment in a hospital to prevent MRSA infection is important in limiting the spread of MRSA. The PCR method for detection of nuc and mecA genes has potential for rapid and accurate diagnosis of MRSA strains.