Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden.
Mol Microbiol. 2020 Mar;113(3):650-658. doi: 10.1111/mmi.14451.
The Gram-positive bacterium Streptococcus pneumoniae, the pneumococcus, is an important commensal resident of the human nasopharynx. Carriage is usually asymptomatic, however, S. pneumoniae can become invasive and spread from the upper respiratory tract to the lungs causing pneumonia, and to other organs to cause severe diseases such as bacteremia and meningitis. Several pneumococcal proteins important for its disease-causing capability have been described and many are expressed on the bacterial surface. The surface located pneumococcal type-1 pilus has been associated with virulence and the inflammatory response, and it is present in 20%-30% of clinical isolates. Its tip protein RrgA has been shown to be a major adhesin to human cells and to promote invasion through the blood-brain barrier. In this review we discuss recent findings of the impact of RrgA on bacterial colonization of the upper respiratory tract and on pneumococcal virulence, and use epidemiological data and genome-mining to suggest trade-off mechanisms potentially explaining the rather low prevalence of pilus-1 expressing pneumococci in humans.
革兰氏阳性细菌肺炎链球菌（Streptococcus pneumoniae），又称肺炎球菌，是人类鼻咽部的一种重要共生菌。通常情况下，带菌者没有症状，但肺炎链球菌可变为侵袭性的，从呼吸道向上传播至肺部引起肺炎，并扩散至其他器官引起严重疾病，如菌血症和脑膜炎。已描述了一些对其致病能力很重要的肺炎链球菌蛋白，其中许多都在细菌表面表达。位于表面的肺炎链球菌 1 型菌毛与毒力和炎症反应有关，存在于 20%-30%的临床分离株中。其尖端蛋白 RrgA 已被证明是人类细胞的主要黏附素，并可促进通过血脑屏障的入侵。在这篇综述中，我们讨论了 RrgA 对呼吸道上部定植和肺炎链球菌毒力的影响的最新发现，并利用流行病学数据和基因组挖掘来提出可能解释表达菌毛 1 的肺炎球菌在人类中相对低流行率的权衡机制。
