Molecular Epidemiology of Community-Associated MRSA

金黄色葡萄球菌（Staphylococcus aureus）是一种多功能病原体，它成功地适应并进化， 多种毒力因子使其能够定殖并随后在人类中引起多种疾病。 耐甲氧西林表皮葡萄金黄色葡萄球菌（MRSA），曾经是现代医院的主要祸害，已经在 社区环境中没有任何已知的风险因素的人。我们的长期研究目标是了解 影响社区相关MRSA（CA-1）流行病学变化的遗传因素 MRSA）。我们对这一提议的具体假设是，1998年的高毒力“原型”CA-MRSA菌株， MW 2（1998年在美国北达科他州的一名16个月大的美国印第安女孩中引起致命性败血症）， 从1992年首次分离的特异性威斯康星州CA-MRSA主要克隆群-2（MCG-2）进化而来 在威斯康星州的一个美国土著社区（NAC）。我们进一步假设MCG-2菌株具有 从甲氧西林敏感的S.金黄色葡萄球菌（MSSA）菌株在NAC中， 使它们成为适应性更强、更成功、更致命的病原体。具体目标是： 1)确定属于MCG-2的早期（1992年）CA-MRSA菌株是否是 成功的CA-MRSA菌株MW 2.具体来说，我们将确定是否有两个美洲土著CA- 来自威斯康星州的MRSA菌株WI-34和WI-99是MW 2的祖菌株。我们将比较 WI-34和WI-99的基因组，以及使用定制的“原型”CA-MRSA、MW 2菌株的基因组 MW 2基因芯片，来自Affyssin Inc.此外，我们还将通过几种方法对WI-34和WI-99进行彻底的基因分型。 基因型方法 2)确定当代CA-MRSA菌株是否属于克隆组MCG-2 从威斯康星州的五个NAC中流行的MSSA菌株进化而来。我们将对以下进行基因分型： MCG-2（回顾性采集），ii）75株NAC-MSSA菌株（回顾性采集），iii）75株MSSA菌株 来自非NAC（回顾性收集），iv）75例最近收集的NAC-CA-MRSA（2002-04年） 和v）20种过渡性MRSA菌株（回顾性收集），其具有CA的一些但不是全部特征- MRSA脉冲场凝胶电泳（PFGE）、多位点序列分型（MLST）、葡萄球菌 盒式染色体mec（SCCmec）、spa和coa分型。 3)确定当代CA-MRSA是否已经进化或继续进化， 从其他MRSA/MSSA中获得额外的毒力因子， 病原体我们将确定所有320个中是否存在40种不同的毒力因子基因 目的2中列出的分离株，并确定当代CA-MRSA中毒力因子基因的进化。

Staphylococcus aureus is a versatile pathogen that has successfully adapted and evolved to produce a variety of virulence factors that allow it to colonize and subsequently cause a variety of diseases in humans. Methicillin-resistant S. aureus (MRSA), once a scourge of modern hospitals primarily, has found a niche in community settings in people without any known risk factors. Our long-term research goal is to understand the genetic factors that are influencing the changing epidemiology of community-associated MRSA (CA- MRSA). Our specific hypothesis for this proposal is that the 1998 hypervirulent 'prototype' CA-MRSA strain, MW2 (caused fatal septicemia in a 16-month old American Indian girl in 1998 in North Dakota, USA), evolved from a specific Wisconsin CA-MRSA major clonal group-2 (MCG-2), which was first isolated in 1992 in a Native American community (NAC) in Wisconsin. We further hypothesize that the MCG-2 strains have evolved to acquire specific genetic traits from methicillin-sensitive S. aureus (MSSA) strain in NACs that allowed them to become more adaptable, successful, and virulent pathogens. The specific aims are to: 1) Determine if the early (1992) CA-MRSA strains belonging to the MCG-2 are the progenitors of the successful CA-MRSA strain, MW2. Specifically, we will determine if the two Native American CA- MRSA strains, WI-34 and WI-99, from Wisconsin were the progenitor strains of MW2. We will compare the genomes of WI-34 and WI-99, with that of the 'prototype' CA-MRSA, MW2 strain using a custom-made MW2 GeneChip¿ from Affymetrix Inc. Additionally, we will thoroughly genotype WI-34 and WI-99 by several genotypic methods. 2) Determine whether or not contemporary CA-MRSA strains belonging to clonal group, MCG-2 evolved from MSSA strains circulating in five NACs in Wisconsin. We will genotype: i) 75 MRSA from MCG-2 (retrospective collection), ii) 75 NAC-MSSA strains (retrospective collection), iii) 75 MSSA strains from a non-NAC (retrospective collection), iv) 75 most recently collected NAC-CA-MRSA (years 2002-04) and v) 20 transitional MRSA strains (retrospective collection) that have some but not all features of CA- MRSA by pulsed-field gel electrophoresis (PFGE), multilocus sequence type (MLST), staphylococcal cassette chromosome mec (SCCmec), spa and coa typing. 3) Determine whether or not the contemporary CA-MRSA have evolved or continue to evolve by acquiring additional virulence factors from other MRSA/MSSA to become awidely successful pathogen. We will determine the presence or absence of 40 different virulence factor genes in all 320 isolates listed in aim 2 and determine evolution of virulence factor genes in contemporary CA-MRSA.