Frequency of Methicillin- Resistance among Clinical Isolates of Staphylococcus Aureus by Phenotypic and Molecular Methods in Yazd

Abstract

Introduction: Staphylococcus aureus is an important human pathogen which can cause a broad spectrum of diseases including minor skin disease to more severe and aggressive infections. Therefore, this study intended to assess the frequency of methicillin-resistance among clinical isolates of S.aureus by phenotypic and PCR methods in Yazd, Iran. Methods: In this descriptive-cross sectional study, a total of 114 S. aureus isolates were collected from Different specimens of patients admitted to shahid sadoughi hospital in Yazd, Iran. Antimicrobial susceptibility testing was determined by disk diffusion method (Kirby-Bauer) and minimum inhibitory concentration of oxacillin (MIC) was performed by E.test method. Moreover, PCR method was performed in order to detect mecA gene using specific primers. Results: Susceptibility testing by disk diffusion method showed that 43 samples (37/7%) and 49 samples(42/1%) were resistant to oxacillin and cefoxitin respectively. MIC results demonstrated that 47(42/1%) samples were resistant to oxacillin. Moreover, 54 samples(47/4%) were found to carry mecA gene using PCR. Highest resistances to antibiotics belonged to ampicillin(99/1 %), penicillin(98/2%), tetracycline(55/3%), erythromycin(37/7%), clindamycin(32/5%), ciprofloxacin (32/5%), ofloxacin (31/6%), gentamicin (26/3%), respectively. Conclusion: The study findings revealed that the multi-drug resistance (MDR) is prevalent among S.aureus isolates. Furthermore, cefoxitin disks were more useful than oxacillin disks to determine methicillin-resistance by disk diffusion method. However mecA gene was also detected in some samples susceptible to disk diffusion method. PCR technique was proved to be the best method to rapidly identify MRSA.

Keywords

• Disk diffusion
• Drug resistant
• Staphylococcus aureus