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ORIGINAL ARTICLE
Changing Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Isolated from Children in the University Hospital Kyoto Prefectural University of Medicine over a Ten-Year Period
1)Department of Clinical Laboratory, Kyoto Prefectural University of Medicine, 2)Department of Infection Control and Laboratory Medicine, Kyoto Prefectural University of Medicine, 3)Department of Pediatrics, Kyoto Prefectural University of Medicine, 4)AMR Clinical Reference Center, Center Hospital of the National Center for Global Health and Medicine
Takeshi KIMURA1), Towa YASUMOTO1), Satoko KURAHASHI1), Yukiji YAMADA1), Yoko TANINO1), Noriko KYOTANI1), Yuri HIROSE1), Toshiaki KOMORI1), Mai KODAMA2), Yumiko FUJITOMO2)4), Masaki NAKANISHI2), Tomoko IEHARA3) & Naohisa FUJITA2)
(Received February 13, 2018)
(Accepted August 6, 2018)
Key words: Community-acquried MRSA, Staphylococcal cassette chromosome mec, sequence type, PCR-based open reading frame typing (POT)
Abstract

Since the 1990s, the prevalence of community-acquired MRSA (CA-MRSA) has begun to emerge worldwide as a cause of infection in community-based individuals without healthcare contact. In recent years, an increase in CA-MRSA in healthcare settings has been reported, and we also confirmed the predominance of presumed CA-MRSA strains in pediatric inpatients after the introduction of the PCR-based ORF typing (POT) method. However, its epidemiology remains unclear. To obtain an understanding of the molecular epidemiology of the MRSA clone, we then surveyed MRSA strains isolated from hospitalized children in 2003, 2008 and 2013, and examined their molecular characteristics with SCCmec typing, multilocus sequence typing (MLST) and so on. The type of SCCmec has been shifting from type II, mainly the NewYork/Japan clone, to type IV since 2003, and the proportion of type IV in inpatient strains rose to 78.6% in 2013. Of the inpatient type IV 46 strains, ST8 snd CC8 accounted for 82.6%, and 93.5%, respectively, and at least 7 types of clones were estimated. PVL-producing strains were not observed, but tst was detected from 10 (21.7%) out of 46 type IV strains. All of the tst(+) strains were ST8 and 9 of the strains were presumed to be potentially pathogenic ST8 CA-MRSA/J. With regard to the POT method, some sort of relationship was found between POT1 scores and SCCmec type II, type IV, CC5, and CC8, respectively. It is thought that analyzing the trend ofz clones will become more important in clinical practice and infection control. Although the POT method has certain limitations, it appears to be usuful as a molecular analysis method complementing others as routine examinations.

[ Kansenshogaku Zasshi 92: 855-862, 2018 ]

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