Abstract

Objective: To determine the prevalence and some genetic characteristics of clinical isolates of Staphylococcus aureus (S. aureus) with reduced susceptibility to vancomycin. Methods: A total of 414 isolates of S. aureus were collected from clinical specimens from hospitals in Tehran. Vancomycin-intermediate S. aureus (VISA) was determined by brain heart infusion agar containing 4 μg/mL vancomycin screening plate and confirmed via E-test. VISA isolates were analysed for vanA, vanB, mecA, staphylococcal cassette chromosome mec types, surface protein A (Spa) types and agr specific groups. Results: Brain heart infusion agar containing 4 μg/mL vancomycin screening tests revealed that 17.14% (n = 71) of S. aureus isolates were VISA phenotype. Ten of the 71 isolates were confirmed by E-test method (minimal inhibitory concentration was 4 to 8 μg/mL). All VISA isolates were susceptible to linezolid and 6 isolates (60%) were methicillin-resistant S. aureus. Five isolates belonged to agr Group II, 4 belonged to agr Group I and 1 belonged to agr Group III. Spa type t030, and staphylococcal cassette chromosome mec Type III were dominant among VISA isolates. Conclusions: This study provides further evidence of the global dissemination of VISA isolates and emphasizes to vancomycin susceptibility testing prior to antibiotic therapy.

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