Experimental infective endocarditis induced by human supragingival dental plaque

人类牙菌斑由多种微生物组成，被认为不仅是口腔中的病原体，也是身体其他部位的病原体。然而，人类牙菌斑本身在全身性疾病中的致病性还没有得到充分的研究。用大鼠模型检测人牙菌斑诱导感染性心内膜炎的能力。从感染部位分离出细菌，并评估其诱导心内膜炎的能力。静脉注射含3×10~(-6)菌落的人牙菌斑悬液后，27只插管大鼠中有15只存活，除1只大鼠外，其余大鼠均形成受感染的菌斑。与各自接种的牙菌斑相比，受感染植物的微生物组成非常简单。在所有受感染的植物中，口腔链球菌占大多数。在感染感染性心内膜炎的大鼠中，主动脉窦内充满了含有细菌的纤维蛋白植被。大量炎性细胞渗入主动脉瓣及其邻近的主动脉。从感染的植物中分离的口腔葡萄球菌细胞悬液，在每只大鼠接种5×106CFU时，能在所有插管的大鼠中引起心内膜炎病变。这些结果表明，人类牙菌斑是引起感染性心内膜炎的病原体传播的重要来源。

Human dental plaque, which consists of numerous species of microorganisms, is thought to work as a pathogen not only in the oral cavity but also in other body sites. However, the pathogenicity of human dental plaque itself in systemic disease is not fully examined. The ability of human supragingival dental plaque to induce infective endocarditis was examined using the rat model. The bacteria were isolated from the locus of infection and the ability of the isolate to induce endocarditis was evaluated. In total, 15 out of 27 catheterized rats survived after intravenous injections with human supragingival dental plaque suspensions containing 3×10^6 CFU of bacterial cells In surviving rats, infiected vegetations were formed in all except one rat. The microbial composition of the infected vegetations was very simple compared to the respective dental plaque inoculates. In all infected vegetations examined, Streptococcus oralis comprised the majority of the isolates. In rats affected with infective endocarditis, the aortic sinus was filled with fibrinous vegetation containing bacteria. Numerous inflammatory cells infiltrated the aortic valve and the aorta adjacent to the valve. A cell suspension of S.oralis isolated from the infected vegetation was capable of inducing endocarditis lesions in all catheterized rats when inoculated at 5×10^6 CFU per rat. The results suggest that human supragingival dental plaque is an important source of dissemination of pathogen, which causes infective endocarditis.