Nationwide surveillance for Staphylococcus aureus with reduced susceptibility to vancomycin in Korea

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) accounts for more than 70% of S. aureus isolates from tertiary hospitals in Korea. Clinical isolates of S. aureus were collected from eight provincial, university-affiliated hospitals during the period from June 1999 to January 2001 for nationwide surveillance. All isolates were screened for reduced susceptibility to vancomycin by using brain heart infusion agar containing 4 micro g of vancomycin per milliliter. Population analysis and the determination of the MIC of vancomycin were done for the isolates which grew on the screening agar plates. Of 682 total isolates, MRSA accounted for 64% (439 of 682). Of 27 (4%) isolates that grew on the screening agar plates, none showed the heteroresistance phenotype. No strains with reduced susceptibility to vancomycin were identified.

FIG. 1.

Result of the nationwide surveillance study for S. aureus with reduced susceptibility to vancomycin. Among 682 S. aureus isolates from eight university-affiliated hospitals, 27 (4%) isolates grew on BHI-V4 agar after incubation for 48 h at 37°C. None revealed the heteroresistance phenotype upon population analysis. MICs of vancomycin, determined by the broth microdilution method, ranged from 1 to 2 μg/ml.