Antibiotic susceptibility pattern among Staphylococcus spp. with emphasis on detection of mecA gene in methicillin resistant Staphylococcus aureus isolates

Background: Staphylococcus aureus is a major pathogen in hospital setting and in the community and causes a wide range of diseases. MRSA infection has recently become a serious problem in anti-microbial chemotherapy. The aim of the study was to detect and analyze the antibiotic diversity and isolation of methicillin resistance gene (mecA) of S. aureus isolated from Tehran hospitals as a rapid and reliable method. Patients and methods: We studied 585 isolates of staphylococcus spp. recovered from patients at 3 clinical centers in Tehran from October 2005 to October 2006. Antibiotic susceptibility test of isolates was achieved with 13 antibiotics by disc diffusion. The MIC of methicillin was also performed by broth micro dilution assay. PCR was used for detection of mecA gene. Results: Totally, 321 (54.7%) isolates were identified as S. aureus. 66, 65, 88, 88, 100, 41, 38, 41, 0, 40, 93, 20 and 64% of S. aureus isolates were resistant to kanamycin, cephotaxim, methicillin, oxacillin, ampicillin, erythromycin, clindamycin, sulphamethoxazole-trimethoprime, vancomycin, chloramphenicol, ciprofloxacin, gentamicin and tetracycline, respectively. All MRSA and 63% of intermediate isolates carried mecA gene. Conclusion: In contrary to other studies in Iran, the prevalence of methicillin resistance is rising up in Tehran and most of MRSA isolates were resistance to 5 antibiotics at least. Vancomycin, chloramphenicol, gentamicin and clindamycin are the most effective antibiotics. All MRSA isolates had mecA gene with different expression. Detection of mecA gene is a rapid and reliable method for identification of MRSA isolates