ABSTRACT

Staphylococcus aureus: with the sequence type (ST) 398 was previously associated with livestock carriage. However, in recent years livestock-independent S. aureus ST398 has emerged, representing a potential health risk for humans especially in nosocomial settings. Judged by whole-genome sequencing analyses, the livestock- and human originated strains belong to two different S. aureus ST398 clades but, to date, it was not known to what extent these clades differ in terms of actual virulence. Therefore, the objective of this study was to profile the exoproteomes of 30 representative S. aureus ST398 strains by mass spectrometry, to assess clade-specific differences in virulence factor secretion, and to correlate the identified proteins and their relative abundance to the strains’ actual virulence. Although the human-originated strains are more heterogeneous at the genome level, our observations show that they are more homogeneous in terms of virulence factor production than the livestock-associated strains. To assess differences in virulence, infection models based on larvae of the wax moth Galleria mellonella and the human HeLa cell line were applied. Correlation of the exoproteome data to larval killing and toxicity toward HeLa cells uncovered critical roles of the staphylococcal Sbi, SpA, SCIN and CHIPS proteins in virulence. These findings were validated by showing that sbi or spa mutant bacteria are attenuated in G. mellonella and that the purified SCIN and CHIPS proteins are toxic for HeLa cells. Altogether, we show that exoproteome profiling allows the identification of critical determinants for virulence of livestock-associated and human-originated S. aureus ST398 strains.

 抽象的

金黄色葡萄球菌：序列类型 (ST) 398 以前与牲畜运输有关。然而，近年来出现了不依赖家畜的金黄色葡萄球菌ST398，这对人类尤其是在医院环境中存在潜在的健康风险。通过全基因组测序分析判断，源自牲畜和人类的菌株属于两个不同的金黄色葡萄球菌ST398 分支，但迄今为止，尚不清楚这些分支在实际毒力方面有多大差异。因此，本研究的目的是通过质谱分析 30 种代表性金黄色葡萄球菌ST398 菌株的外蛋白质组，评估毒力因子分泌的进化枝特异性差异，并将鉴定的蛋白质及其相对丰度与菌株的实际毒力。尽管人类来源的菌株在基因组水平上更具异质性，但我们的观察表明，它们在毒力因子产生方面比牲畜相关菌株更加同质。为了评估毒力的差异，应用了基于蜡蛾幼虫和人类 HeLa 细胞系的感染模型。外蛋白质组数据与幼虫杀伤和对 HeLa 细胞的毒性的相关性揭示了葡萄球菌 Sbi、SpA、SCIN 和 CHIPS 蛋白在毒力中的关键作用。这些发现得到了证实，显示sbi或spa突变细菌在大蜡螟中减毒，并且纯化的 SCIN 和 CHIPS 蛋白对 HeLa 细胞有毒。总而言之，我们表明，外蛋白质组分析可以识别与牲畜相关和人类来源的金黄色葡萄球菌毒力的关键决定因素。 金黄色葡萄球菌 ST398 菌株。