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 Original Research Article British Microbiology Research Journal, 4(4): 454-461, 2014 455 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.
Highlights
Staphylococcus aureus, as a major cause of potentially life-threatening infections acquired in health care settings and in the community, has developed resistance to most classes of antimicrobial agents soon after their introduction into clinical use
methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria that are resistant to certain antibiotics
The first vanA-mediated, vancomycin-resistant Staphylococcus aureus (VRSA) strain was isolated from the catheter tip of a diabetic, renal dialysis patient in a Michigan hospital in 2002 .Since several additional occurrences have been reported [1]
Summary
Staphylococcus aureus, as a major cause of potentially life-threatening infections acquired in health care settings and in the community, has developed resistance to most classes of antimicrobial agents soon after their introduction into clinical use. Resistance to methicillin in S.aureus is caused by the expression of penicillin-binding protein PBP2a (PBP2 ́), which is encoded by the mecA gene. This gene is located on a genetic element called the staphylococcal cassette chromosome [4,5,6,7].Since the emergence of MRSA, options for treatment of S.aureus infection have been significantly limited. The emergence of vancomycin-intermediate S. aureus (VISA) in 1996 evoked great concern between health care workers around the world These bacterial strains present a thickening of the cell wall, which is believed to deplete the vancomycin available to kill the bacteria. The VISA strains do not carry the enterococcal vancomycin-resistance gene vanA, vanB or vanC 1–3, these strains become resistant to vancomycin by producing a thick cell wall [8]
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