Antibiotic Resistance and mecA Gene among Methicilin Resistant Staphylococcus aureus Isolated from Tehran Hospitals-2008-2011

Staphylococcus aureus is a common cause of infections among human and animals and known as community-acquired and nosocomial pathogen. MRSA infection has recently become a serious problem in anti-microbial chemotherapy. The aim of the study was to detect and analyze the antibiotic resistance pattern among MRSA isolated from six hospitals in Tehran in 2008-2011.

Totally 396 isolates of MRSA from clinical samples were collected from six hospitals in Tehran. All isolates were identified at the species level using specific primers. Susceptibility to seventeen antibiotics was determined using disc diffusion method. MIC of oxacillin and vancomycin in MRSA isolates was also done using Etest according to CLSI recommendation. PCR was used to detect mecA gene.

Using PCR all isolates were confirmed as MRSA. The highest level of resistance was observed to oxacillin, penicillin, ciprofloxacin, kanamycin, erythromycin, tobramycin and amikacin respectivelyMIC results showed that 86% of isolates showed high level resistant to oxacillin (MIC≥256 μg/ml). None of the MRSA isolates were resistant to vancomycin. One hundred percent of the isolates contained mecA gene.

This study showed that the prevalence of MRSA isolates is lower than the other studies in Iran. MRSA isolates showed resistance to broad spectrum of antibiotics. Synercid, linezolid, vancomycin and chloramphenicol are the most effective antibiotics against MRSA infections. Detection of mecA gene is a rapid and reliable method for identification of MRSA isolates.