The USA300 clone, which produces Panton–Valentine leukocidin (PVL), is a major pathogenic community‐acquired methicillin‐resistant Staphylococcus aureus (CA‐MRSA) clone that causes intractable skin infections. Recently, PVL‐positive CA‐MRSA, including USA300 clones, have emerged in both communities and hospitals in Japan. To prevent an outbreak of PVL‐positive MRSA, infected patients should be treated with effective antimicrobial agents at community clinics. Herein, we investigate molecular epidemiological characteristics of PVL‐positive MRSA isolated from outpatients with skin and soft tissue infections (SSTI), which are common community‐onset infectious diseases. The detection rate of MRSA was 24.9% (362 strains) out of 1455 S. aureus strains isolated between 2013 and 2017. Among the MRSA strains, 15.5% (56 strains) were PVL‐positive strains and associated with deep‐seated skin infections. Molecular epidemiological analyses of PVL‐positive MRSA showed that USA300 was the predominant clone (53.6%, 30 strains) and was identified in Kanto (18 strains), Kagawa (nine strains), Tohoku (two strains) and Hokkaido (one strain). Notably, minocycline and fusidic acid were effective against all PVL‐positive MRSA strains. Hence, our data reveals the current status of PVL‐positive MRSA isolated from patients with SSTI in Japan. Continuous surveillance of CA‐MRSA is necessary to monitor latest prevalence rates and identify effective antimicrobial agents for PVL‐positive MRSA strains.

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Recently, the USA300 clone, which is a Panton–Valentine leukocidin (PVL)‐positive clonal complex 8‐staphylococcal cassette chromosome mec type IV (CC8‐IV) community‐acquired methicillin‐resistant Staphylococcus aureus (CA‐MRSA) strain, emerged in community and hospital settings in Japan. Hence, clonal types of CA‐MRSA strains are predicted to be changing. Nonetheless, long‐term surveillance of CA‐MRSA has not been conducted in Japan. Here, we investigated the transition and current status of CA‐MRSA strains isolated from outpatients with impetigo; the samples were collected between 2007 and 2016 in Kagawa, Japan. The detection rate (22.8%, 488/2139 strains) of MRSA slightly decreased in these 10 years. Molecular epidemiological analyses showed that the prevalence of the CC89‐II clone, which is a typical CA‐MRSA genotype of causative agents of impetigo, significantly decreased from 48.0% (48/100 strains) in 2007–2009 to 21.9% (16/73 strains) in 2013–2016. By contrast, a non‐USA300 CC8‐IV clone, which is a highly pathogenic CA‐MRSA/J clone, significantly increased in prevalence from 9.0% (9/100 strains) to 32.9% (24/73 strains). The prevalence of PVL‐positive CA‐MRSA strains increased annually from 2012 (0%) to 2015 (6.7%), whereas only one of these strains turned out to be the USA300 clone. Antibiotic susceptibility data revealed that the rates of resistance to gentamicin and clindamycin among CA‐MRSA strains decreased along with the decreased prevalence of the CC89‐II clone and increased prevalence of the CA‐MRSA/J clone. Our data strongly suggest that the clonal types and antibiotic susceptibility of CA‐MRSA isolated from patients with impetigo dramatically changed during the last 10 years in Japan.