a Institute of Medical Microbiology, Virology and Hygiene, Rostock University Medical Center , Rostock , Germany.
b Nutrition and Health, Laboratory of Food Biotechnology, Institute of Food, ETH Zürich , Zürich , Switzerland.
Virulence. 2018 Jan 1;9(1):248-261. doi: 10.1080/21505594.2017.1393600. Epub 2017 Dec 26.
Streptococcus gallolyticus subsp. gallolyticus, formerly classified as S. bovis biotype I, is an increasing cause of bacteremia and infective endocarditis in the elderly. The physiopathology of infective endocarditis is poorly understood and involves immune and coagulation systems. In this study, we found that S. gallolyticus subsp. gallolyticus activates the human contact system, which in turn has two consequences: cleavage of high-molecular-weight kininogen (HK) resulting in release of the potent pro-inflammatory peptide bradykinin, and initiation of the intrinsic pathway of coagulation. S. gallolyticus subsp. gallolyticus was found to bind and activate factors of the human contact system at its surface, leading to a significant prolongation of the intrinsic coagulation time and to the release of bradykinin. High-affinity binding of factor XII to the bacterial Pil1 collagen binding protein was demonstrated with a K of 13 nM. Of note, Pil1 expression was exclusively found in S. gallolyticus subsp. gallolyticus, further supporting an essential contribution of this pilus in virulence.
牛链球菌亚种（以前归类为牛型生物型 I）是老年人菌血症和感染性心内膜炎日益增加的病因。感染性心内膜炎的病理生理学尚未完全了解，涉及免疫和凝血系统。在这项研究中，我们发现牛链球菌亚种（以前归类为牛型生物型 I）激活了人体接触系统，这反过来又有两个后果：高分子量激肽原（HK）的裂解导致强效促炎肽缓激肽的释放，以及内源性凝血途径的启动。发现牛链球菌亚种（以前归类为牛型生物型 I）在其表面结合并激活人体接触系统的因子，导致内源性凝血时间显著延长，并释放缓激肽。用 13 nM 的 K 值证明了因子 XII 与细菌 Pil1 胶原蛋白结合蛋白的高亲和力结合。值得注意的是，仅在牛链球菌亚种（以前归类为牛型生物型 I）中发现 Pil1 的表达，这进一步支持该菌毛在毒力中的重要作用。
