Determination of Vancomycin and Methicillin Resistance in Clinical Isolates of Staphylococcus aureus in Iranian Hospitals
Abbas Farhadian
Department of Bacteriology, School of Medical Science, Tarbiat Modares University, Iran.
Qorban Behzadian Nejad
Department of Bacteriology, School of Medical Science, Tarbiat Modares University, Iran.
Shahin Najar peerayeh
Department of Bacteriology, School of Medical Science, Tarbiat Modares University, Iran.
Mohammad Rahbar *
Department of Microbiology, Iranian Reference Health Laboratory Ministry of Health and Medical Education, Tehran, Iran and Antimicrobial Resistance center, Iran University of Medical sciences, Tehran, Iran.
Farzam Vaziri
Department of Bacteriology, School of Medical Science, Tarbiat Modares University, Iran.
*Author to whom correspondence should be addressed.
Abstract
Aims: The aim of this study was to determine the prevalence of methicillin resistant S. aureus (MRSA), vancomycin resistant or vancomycin intermediate resistant S. aurues (aureus) (VRSA/VISA) among clinical isolates.
Study Design: S.aureus isolates used in this study were randomly collected from in-patient and outpatient of several hospitals of 7 cities in Iran (Tehran, Shiraz, Zahedan, Tabriz, Sannandaj, Sari, and Ahvaz) during 2006-2008.
Methodology: Antibiotic susceptibility of 250 strains of Staphylococcus aureus isolated from Iranian hospitals were determined by disk diffusion method. Minimum inhibitory concentration (MICs) were determined for oxacillin and vancomycin by E-test. PCRs were used by specific primers (PCR used specific primers) for detection of mecA, vanA, vanB genes.
Results: The percentage of resistance by disk diffusion method was as below: methicillin 46%, vancomycin 0%, penicillin 86%, erythromycin 42%, ciprofloxacin 29%, gentamicin 39% and clindamycin 33%. E-test MIC method showed that 43% isolates were resistant to methicillin and 4% isolates were VISA (≤ 8µg/ml). The prevalence of resistance genes in the clinical isolates were: mecA 44%, vanA 0%, vanB 0%.
Conclusion: This study revealed that clinical isolates have rather high resistance to methicillin, erythromycin, gentamicin, penicillin and clindamycin We did not observe resistance to vancomycin. In order to avoid a possible outbreak involving VISA), vancomycin should be used carefully as a drug for treatment of S. aureus infections.
Keywords: S. aureus, MRSA, VRSA, VISA, E-test, PCR