Institute of Clinical Epidemiology and Molecular Biology (EpiGen), Akershus University Hospital, Lørenskog, Norway.
Clin Microbiol Infect. 2009 Dec;15(12):1139-45. doi: 10.1111/j.1469-0691.2009.02745.x. Epub 2009 Apr 23.
Reports of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) causing hospital infections are increasing, and it is questionable whether the existing molecular definition of CA-MRSA is suitable for the characterization of all strains involved. The 821 methicillin-resistant S. aureus (MRSA) isolates recovered from patients in Health Region East, Norway during the period 1991-2006 were characterized by multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) gene typing, and their content of exotoxin-encoding genes. Cluster analysis based on exotoxin-encoding gene content was performed to separate the MRSA isolates into valid clusters with respect to microbiological characteristics. The analysis gave a four-cluster structure, and the four toxin clusters differed in the genetic lineages they included and in the diversity of the genetic lineages. A few genetic lineages were present in several toxin clusters. These results support the theory that mobile genetic elements encoding virulence genes do not move randomly among genetic lineages, but are restricted by the clonal lineages' genetic background. Using the molecular criteria, MLST type, SCCmec type and the presence of the lucS/F-Panton-Valentine leukocidin (PVL) gene to define a CA-MRSA isolate, it was found that the CA-MRSA isolates mainly grouped together in two toxin clusters with a low prevalence of exotoxin-encoding genes. Statistical analyses supported the conclusion that toxin clusters with CA-MRSA genetic lineages were characterized by a low prevalence of exotoxin-encoding genes, whereas toxin clusters with hospital-acquired MRSA genetic lineages were characterized by a higher prevalence of exotoxin-encoding genes.
社区获得性耐甲氧西林金黄色葡萄球菌（CA-MRSA）引起医院感染的报告正在增加，现有的 CA-MRSA 分子定义是否适用于所有相关菌株的特征描述值得怀疑。1991-2006 年期间，从挪威东部卫生区的患者中分离出 821 株耐甲氧西林金黄色葡萄球菌（MRSA），采用多位点序列分型（MLST）、葡萄球菌盒式染色体 mec（SCCmec）分型、葡萄球菌蛋白 A（spa）基因分型以及产毒素编码基因的含量对其进行了特征描述。基于产毒素编码基因含量的聚类分析将 MRSA 分离株分为具有微生物学特征的有效聚类。分析得到了一个四聚类结构，四个毒素聚类在包含的遗传谱系和遗传谱系的多样性方面存在差异。少数遗传谱系存在于几个毒素聚类中。这些结果支持这样一种理论，即编码毒力基因的可移动遗传元件并非在遗传谱系之间随机移动，而是受到克隆谱系遗传背景的限制。使用分子标准，包括 MLST 型、SCCmec 型和 lucS/F-杀伤白细胞素（PVL）基因的存在，来定义 CA-MRSA 分离株，发现 CA-MRSA 分离株主要聚集在两个毒素聚类中，产毒基因的流行率较低。统计分析支持这样的结论，即具有 CA-MRSA 遗传谱系的毒素聚类的产毒基因流行率较低，而具有医院获得性 MRSA 遗传谱系的毒素聚类的产毒基因流行率较高。
