Dissemination of methicillin-resistant staphylococci among Japanese Students

本研究では,地域間格差の少ないと考えられる成人集団として大学生を対象に,市中におけるメチシリン耐性黄色ブドウ球菌(methicillin- resistant Staphylococcus aureus MRSA ))およびメチシリン耐性表皮ブドウ球菌(methicillin― resistant Staphylococcus epidermidis : MRSE)の保有率とその薬剤耐性の状況,それらのSCCmec ( Staphylococcal cassette chromosome mec )タイプについて検討した.その結果,MRSAの保有率は1.4%(146名中2名)であり,MRSEについては13.0%(146名中19名)であった。このことから,市中ではMRSAよりもMRSEの拡散が進んでいることが明らかとなった。また,耐性化についても表皮ブドウ球菌の進行が顕著であり,その割合は黄色ブドウ球菌のおよそ4倍であった。 分離されたMRSAおよびMRSEについて,薬剤感受性のパターンは様々であつたが,一般に用いられる多くの抗菌薬に対して感受性を示す菌株が大多数であった。 SCCmecのタイプを調べたところ,2011年に分離されたMRSAおよびMRSEの10菌株では,その8菌株が市中で分離されるメチシリン耐性ブドウ球菌に多く見られるタイプⅣを有していた。残り2菌株についてはタイプの特定ができなかった。We investigated staphylococcal strains isolated from college students of a Japanese community to evaluate the prevalence and characteristics of methicillin-resistant staphylococci. Of the 146 students examined, 2 (1.4%) and 19 (13.0%) were colonized with methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE), respectively. These observations suggested that, compared with MRSA strains, MRSE strains were highly disseminated among Japanese college students. Moreover, these MRSE strains accounted for 18.3% of all isolated S. epidermidis strains, and 4.3% of S. aureus isolates possessed mecA gene that confers methicillin resistance in staphylococci. S. epidermidis was more predominant than S. aureus with regard to acquisition of the resistance gene. Antimicrobial susceptibility was tested by the disk diffusion method, and minimum inhibitory concentrations (MICs) were determined by the E-test. The wide range of MICs, 0.19 to 64 ng/ml, was observed to oxacillin, and most of MRSE and MRSA strains were still susceptible to the various kinds of antibiotics used in this study. To determine the clonal compositions of the MRSA and MRSE isolates, 10 strains were subjected to SCCmec PCR typing. Eight strains were found to harbor SCCmec type IV elements, although the other 2 strains were not classified. This type of the element appeared to be mainly distributed among the resistant staphylococci in the Japanese community studied.departmental bulletin pape