Clonal change of methicillin‐resistant Staphylococcus aureus isolated from patients with impetigo in Kagawa, Japan

Abstract

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.

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