Prevalence and accessory gene regulator (agr) analysis of vancomycin-intermediate Staphylococcus aureus among...

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in nosocomial staphylococcal infections in Taiwan has exceeded 50% since 2000. However, little relevant data has been available concerning vancomycin-intermediate S. aureus (VISA) and heteroresistant VISA (hVISA). We collected 1,000 MRSA isolates from ten medical center hospitals in Taiwan during 2003. All were initially screened for reduced susceptibility to vancomycin on brain heart infusion (BHI) agar containing 5 mg/L vancomycin. Among 34 MRSA isolates that grew on the screening plates, two VISA isolates (0.2%) and seven hVISA isolates (0.7%) were evident. Vancomycin-resistant S. aureus was not detected. The accessory gene regulator (agr) typing of all 1,000 MRSA strains were typed by multiplex polymerase chain reaction (PCR); 919 strains (91.9%) including the VISA and hVISA isolates belonged to agr group I, 78 strains (7.8%) were agr group II, two strains (0.2%) were agr group III, and one isolate (0.1%) was agr group IV. There was no relationship between sample sites and agr typing. In 2003, the incidence of hVISA and VISA in Taiwan was low. Continued surveillance is recommended, given the implementation of new Clinical and Laboratory Standards Institute (CLSI) criteria for S. aureus and the increasing clinical use of glycopeptides.