Diep Binh An, Carleton Heather A, Chang Richard F, Sensabaugh George F, Perdreau-Remington Francoise
Division of Infectious Diseases, Department of Medicine, University of California, San Francisco, USA.
J Infect Dis. 2006 Jun 1;193(11):1495-503. doi: 10.1086/503777. Epub 2006 Apr 21.
The extent to which the horizontal transfer of virulence genes has contributed to the emergence of contemporary virulent strains of methicillin-resistant Staphylococcus aureus (MRSA) in hospital and community settings is poorly understood.
Epidemiologically well-characterized MRSA isolates collected over 8.5 years were genotyped and tested for the presence of 34 virulence genes.
Six strain types accounted for 88.2% of all MRSA infections. The evolution of contemporary hospital and community phenotypes within the CC8 and CC30 lineages--2 background genomes that produced historical pandemic MRSA clones--were associated with multiple horizontal acquisitions of virulence genes. The epidemic community phenotype of a CC8 strain, designated ST8:USA300, was linked to the acquisition of staphylococcal cassette chromosome (SCC)mec type IV, the genes for Panton-Valentine leukocidin (PVL), and the enterotoxin Q and K genes. Similarly, the epidemic community phenotype of a CC30 strain, ST30:USA1100, was linked to the acquisition of SCCmec type IV and the pvl genes. In contrast, the epidemic hospital phenotype of another CC30 strain, ST36:USA200, was associated with the acquisition of SCCmec type II, the enterotoxin A gene, and the toxic shock syndrome toxin 1 gene. The pvl genes appear not to be essential for the evolution OF other community-associated strains of mrsa, including ST8:USA500 and ST59:USA1000.
The horizontal transfer of virulence genes, although infrequent, is epidemiologically associated with the emergence of new virulent strains of MRSA.
毒力基因的水平转移在多大程度上促成了医院和社区环境中耐甲氧西林金黄色葡萄球菌（MRSA）当代毒力菌株的出现，目前尚不清楚。
对8.5年期间收集的流行病学特征明确的MRSA分离株进行基因分型，并检测34种毒力基因的存在情况。
六种菌株类型占所有MRSA感染的88.2%。CC8和CC30谱系内当代医院和社区表型的演变——这两个背景基因组产生了历史上的大流行MRSA克隆——与毒力基因的多次水平获得有关。CC8菌株的流行社区表型，即ST8:USA300，与葡萄球菌盒式染色体（SCC）mec IV型、杀白细胞素（PVL）基因、肠毒素Q和K基因的获得有关。同样，CC30菌株ST30:USA1100的流行社区表型与SCCmec IV型和pvl基因的获得有关。相比之下，另一个CC30菌株ST36:USA200的流行医院表型与SCCmec II型、肠毒素A基因和中毒性休克综合征毒素1基因的获得有关。pvl基因似乎对于其他社区相关的MRSA菌株的进化并非必不可少，包括ST8:USA500和ST59:USA1000。
毒力基因的水平转移虽然不常见，但在流行病学上与新的MRSA毒力菌株的出现有关。
