Molecular Characterization of Community-Associated Methicillin-Resistant Staphylococcus aureus Isolated from Skin and Pus Samples of Outpatients in Japan.

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is now endemic in the United States. In Japan, CA-MRSA infections and CA-MRSA surveillance have been scarcely reported. In this study, we conducted a nationwide survey of CA-MRSA in Japan. We collected MRSA strains isolated from outpatients with skin and soft-tissue infection (SSTI) at 107 medical facilities from 24 prefectures in 2010 and 2012. Among 10,385 clinical samples from SSTI patients, 3,581 S. aureus isolates (35%) were obtained and 673 of the S. aureus strains (19%) were identified as MRSA. Among 625 MRSA strains tested in this study, 266 strains (43%) and 114 strains (18%) were classified as SCCmec types IV and V, respectively. Detection of virulence genes was as follows: Panton-Valentine leukocidin (PVL) gene (57 strains, 9%), exfoliative toxin (ET) gene (179 strains, 29%), toxic shock syndrome toxin-1 (TSST-1) gene (195 strains, 31%), or none. PVL-positive strains were classified into eight sequence types (STs) (i.e., ST1, ST5, ST8, ST22, ST30, ST452, ST59, and ST154) and six clonal complexes (i.e., CC1, CC5, CC8, CC22, CC30, and CC59). Only 10 PVL-positive strains (2%) were pulsed-field type USA300 clone. There were a wide variety of CA-MRSA clones in Japan, which were different from the situation in the United States.