Genotypic Identification Of Streptococcus Sanguis Group And The Relationship With Coronary Heart Disease

BACGROUND&OBJECTIVE: Supragingival dental plaque includes large numbers of viridans streptococci belonging to a taxonomic subdivision described by various authors as the "streptococcus sanguis group". That group now is known to show high levels of genotypic diversity. At least four oral species have been defined, including Streptococcus gordonii, Streptococcus sanguis, Streptococcus oralis and Streptococcus mitis. The distribution of those species varies between oral sites. Each may appear at different times in plaque development, and multiple strains may be present in the same mouth. Streptococcus sanguis group generally are considered commensal. They have been the objects of considerable investigationas predominant colonizers of the tooth surface, which may facilitate or inhibit the later establishment of oral pathogens. For example, streptococcus sanguis can bind to proteins in the salivary pellicle, and in turn provide binding sites for the periodontal pathogen Porphyromonas gingivalis. On the other hand, they may compete with mutans streptococci, the group of acidogenic species considered responsible for dental caries.Recent work suggests that oral streptococcus sanguis group species may become of greater clinical importance of to dentistry and medicine. They may play a direct role in caries, since strains recovered from caries-prone individuals can produce almost as much acid as mutans streptococci. However, it is not known whether particular streptococcus sanguis group species are more likely to include acidogenic strains. Oral streptococcus sanguis group species have long been recognized as potential causative agents for endocarditis. They now have been identified as an emerging source of septicemia in neutropenic cancer patients. Platelet aggregation can be caused by collagen and thrombin, as well as streptococcus sanguis, the microorganism found in the oral cavity. Investigations showed that this organism has a collagenlike molecule, the platelet-aggregation-associated protein(PAAP), on its surface. But only the strains with Agg+ phenotype induce platelets to aggregate, while strains with Agg-phenotype do not. For above reasons, this paper showed some investigations on the character of oral streptococcus sanguis group.METHODS: Blood agar plates, NAYS-B agar plates and automation identification instrument for microorganisms were applied in this test to account and classify the Streptococcus sanguis group between coronary heart disease group and the control group. The indirect-ELISA was applied to measure the antibody to Streptococcus sanguis in serum between coronary heart disease group and control group. The ability of platelet aggregation induced by the members of Streptococcus sanguis group was tested through the instrument of platelet aggregation. Chromosome DNA extracted by three different methods for the same species was expanded through Arbitrary Primed Polymerase Chain Reaction (AP-PCR) and used in the genotypic identification of Streptococcus Sanguis Group(SSG). All the data were analyzed by SPSS statistical software.RESULTS: The chromosome DNA of same strains was extracted in 3 different methods, and the same electrophoretic bands were got by arbitrary primed polymerase chain reaction (AP-PCR). The level of S.sanguis group and the positive rate of S.sanguis/S.gordonii in saliva and supragingival dental plaque are significantly higher in CHD group than control group, the positive rate of S.oralis and S.mitis in saliva and supragingival dental plaque are similar between the two groups.The serum antibody levels to whole cell body antigens of Streptococcus sanguis 133-79 have no significant difference between CHD group and control group, and the antibody was common in these two groups. Of the members of SSG, S.sanguis 133-79 strain was the only one that induced the platelets to aggregate in vitro, but the rate of aggregation was not great.CONCLUSIONS: The applying of AP-PCR in the identification of SSG is not associated with the methods of DNA extraction.