Antimicrobial susceptibility and molecular characteristics of 857 methicillin-resistant Staphylococcus aureus isolates from 16 medical centers in Japan (2008-2009): nationwide survey of community-acquired and nosocomial MRSA.

This study is a nationwide survey of all clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates, including community-acquired MRSA (CA-MRSA), in Japan. A total of 857 MRSA clinical isolates were collected from the 16 institutions throughout Japan that participated in the survey (2008-2009). The drug susceptibility and staphylococcal cassette chromosome mec (SCCmec) typing and the presence of specific pathogenic genes were evaluated. The isolates comprised SCCmec type II (73.6%), type IV (20%), and type I (6%). The percentage of SCCmec type IV isolates was significantly higher in outpatients than in inpatients. Most of the isolated strains were sensitive to vancomycin (VCM, MIC ≤2 μg/mL), linezolid (MIC ≤4 μg/mL), and teicoplanin (MIC ≤8 μg/mL). Although most strains were sensitive to VCM, the MIC value of VCM for SCCmec type II strains was higher than that for SCCmec type IV strains. Only 4 (2.3%) of 171 SCCmec type IV strains were Panton-Valentine leukocidin (lukS/F-PV)-positive. Thus, this result indicates a unique feature of SCCmec type IV strains in Japan. The information in this study not only is important in terms of local public health but will also contribute to an understanding of epidemic clones of CA-MRSA.