Experimental infective endocarditis induced by human supragingival dental plaque

人类牙菌斑由许多种微生物组成，被认为不仅在口腔中而且在其他身体部位作为病原体起作用。然而，人类牙菌斑本身在系统性疾病中的致病性尚未得到充分研究。用大鼠模型检测人龈上牙菌斑诱发感染性心内膜炎的能力。从感染部位分离细菌，并评价分离株诱导心内膜炎的能力。在静脉注射含有3×10^6 CFU细菌细胞的人龈上牙菌斑悬液后，27只插管大鼠中共有15只存活。在存活的大鼠中，除1只大鼠外，所有大鼠均形成感染性赘生物。与各自的牙菌斑接种物相比，感染赘生物的微生物组成非常简单。在所有受感染的赘生物检查，口腔链球菌组成的大多数菌株。在感染性心内膜炎的大鼠中，主动脉窦充满了含有细菌的细菌性赘生物。大量炎性细胞浸润主动脉瓣和邻近瓣膜的主动脉。当以每只大鼠5×10^6 CFU接种时，从感染赘生物中分离的口腔链球菌细胞悬液能够在所有插管大鼠中诱导心内膜炎病变。结果提示，人龈上菌斑是引起感染性心内膜炎的重要病原传播源。

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.