Department of Global Health, University of Washington, Seattle, Washington, USA.
Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, Washington, USA.
J Infect Dis. 2021 Apr 23;223(8):1488-1496. doi: 10.1093/infdis/jiaa548.
Group B streptococci (GBS) are β-hemolytic, Gram-positive bacteria associated with fetal injury, preterm birth, spontaneous abortion, and neonatal infections. A key factor promoting GBS virulence is the β-hemolysin/cytolysin, a pigmented ornithine rhamnolipid (also known as granadaene) associated with the bacterial surface.
A previous study indicated that GBS produce small structures known as membrane vesicles (MVs), which contain virulence-associated proteins. In this study, we show that GBS MVs are pigmented and hemolytic, indicating that granadaene is functionally active in MVs.
In addition, MVs from hyperhemolytic GBS induced greater cell death of neutrophils, T cells, and B cells compared with MVs from isogenic nonhemolytic GBS, implicating MVs as a potential mechanism for granadaene-mediated virulence. Finally, hemolytic MVs reduced oxidative killing of GBS and aggravated morbidity and mortality of neonatal mice infected with GBS.
These studies, taken together, reveal a novel mechanism by which GBS deploy a crucial virulence factor to promote bacterial dissemination and pathogenesis.
B 群链球菌（GBS）是一种β-溶血性、革兰氏阳性细菌，与胎儿损伤、早产、自然流产和新生儿感染有关。促进 GBS 毒力的一个关键因素是β-溶血素/细胞毒素，这是一种与细菌表面相关的色素鸟氨酸鼠李糖脂（也称为格兰纳丁）。
先前的一项研究表明，GBS 会产生称为膜泡（MVs）的小结构，其中包含与毒力相关的蛋白质。在这项研究中，我们表明 GBS MVs 是色素沉着和溶血的，表明格兰纳丁在 MVs 中具有功能活性。
此外，与同源非溶血 GBS 的 MVs 相比，高溶血 GBS 的 MVs 诱导更多的中性粒细胞、T 细胞和 B 细胞死亡，这表明 MVs 是格兰纳丁介导的毒力的潜在机制。最后，溶血 MVs 降低了 GBS 的氧化杀伤作用，并加重了感染 GBS 的新生小鼠的发病率和死亡率。
这些研究共同揭示了 GBS 部署关键毒力因子以促进细菌传播和发病机制的新机制。
