Molecular Epidemiology of Nosocomial Infection Caused by Methicillin-Resistant Staphylococcus aureus

在MRSA医院感染的流行病学研究中，使用了噬菌体类型、凝固酶类型、抗生素模式或生物学特征。我们对临床分离的MRSA菌株进行了流行病学研究，使用分子生物学技术和DNA分析。为了阐明实际医院感染的细节，我们调查了名古屋大学医院住院患者中MRSA分离的频率和MRSA感染的发生率，并通过脉冲场凝胶电泳确定了分离的MRSA的基因型。此外，为研究MRSA的地域分布差异，对563株从国立大学医院收集的MRSA菌株进行了基因型测定，并对这些基因型进行了总结，建立了一个DNA分型系统，即MRSA分离株的计算机化目录。使用该系统，不仅可以比较医院内的细菌，还可以比较日本与其他国家之间的细菌。根据MRSA菌株的不同，致病程度也不同。特别是，从严重MRSA感染患者中分离的菌株进行了仔细检查，以确定这些菌株中是否存在特征性基因型。在名古屋大学医院引起严重MRSA感染如败血症的菌株集中于几种基因型。其他医院引起术后重症肠炎的菌株也有一定的基因型。如果能够预先知道可能导致严重感染的MRSA菌株的基因型，就有可能采取预防措施。

In epidemiologic studies of MRSA nosocomial infection, phage types, coagulase types, antibiotic patterns, or biological features have been used. We conduct epidemiologic studies of clinically isolated MRSA strains, using molecular biological techniques with DNA analysis.In order to clarify details of actual nosocomial infections, the frequency of MRSA isolation and the incidence of MRSA infection in inpatients of the Nagoya University Hospital are investigated and the genotype of isolated MRSA is determined by pulsed-field gel electrophoresis.Moreover, the genotypes of 563 MRSA strains collected from national university hospitals were also determined to study the regional differences of MRSA spread.These genotypes were summarized and a DNA typing system, a computerized catalog of isolated MRSA strains, was created. Use of this system enables comparison of bacteria among the hospitals or between Japan and other countries as well as comparison of bacteria within the hospital.The degree of pathogenesis differs according to each MRSA strain. Especially, strains isolated from patients with severe MRSA infection were examined carefully to determine whether or not there were characteristic genotypes in those strains. The strains causing severe MRSA infection such as sepsis in the Nagoya University Hospital were concentrated to several genotypes. The strains causing postoperative severe enteritis in other hospitals were also certain genotypes. It will become possible to take preventive measures if MRSA strains which may cause severe infection from the genotypes can be known in advance.