Vol.67 No.2 March 2019
Infective endocarditis induced by a major pathogen of dental caries
Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, 1-8 Yamada-oka, Suita, Osaka, Japan
Abstract
Infective endocarditis is a systemic septic disease characterized by embolization and heart failure, with the formation of bacterial masses called vegetations on the heart valves or endocardium. Bleeding from the oral cavity induced by invasive dental treatments or daily routine tooth brushing is thought to be a risk factor for the occurrence of infective endocarditis. Streptococcus mutans, a major pathogen of dental caries, is also known to be involved in the etiology of infective endocarditis; this bacterium is serologically classified into four serotypes, the c, e, f and k serotypes. Serotype c is the major type in oral isolates, with a distribution frequency of approximately 70% to 80%, followed by serotype e (frequency of approximately 20%); the distribution frequencies of serotypes f and k are lower than 5%. On the other hand, the serotype distribution of S. mutans in the blood or extirpated heart valves taken from patients with bacteremia or infective endocarditis was totally different from that in the oral cavity. Detailed analyses focusing on the cell surface structure of S. mutans revealed that collagen-binding proteins (CBP), such as Cnm and Cbm, were frequently identified in the serotype f and k strains. Some of the CBP-positive S. mutans strains show high levels of adhesion to and invasion of vascular endothelial cells, and induce platelet aggregation in the presence of fibrinogen, resulting in the formation of prominent vegetations in a rat model of infective endocarditis. Furthermore, an ex-vivo model with S. mutans strains adhering to bovine heart valves cut into small pieces was constructed, which may be a useful tool to evaluate the virulence of many bacterial strains for screening purposes. These results suggest that specific S. mutans strains show high virulence for causing infective endocarditis, and that it is therefore important for dentists to prevent invasion of the bloodstream by bacteria from the oral cavity.
Key word
Streptococcus mutans, serotype, collagen-binding protein, infective endocarditis
Received
August 23, 2018
Accepted
October 29, 2018
Jpn. J. Chemother. 67 (2): 176-181, 2019
