Construction and Isolation of streptococci useful for caries-prevention by replacement therapy

变形链球菌、变形链球菌和远缘链球菌被认为是龋病的主要病原菌。这些生物的定植程度与人类和实验动物携带牙齿的流行程度有关。变形链球菌促进龋病发生的一个重要毒力因素是在蔗糖存在下能在牙面上牢固定植并在现场产生致龋性生物膜的能力。本研究的目的是构建或分离抗致龋性I类链球菌，通过替代疗法预防龋病。结果表明，从一名无龋生中分离到一株变形链球菌MKM33，可在大鼠体内定植且不致龋性；从荷兰儿童分离的两株类远缘链霉菌(HG1006和HG988)经鉴定为环状链球菌，均可在大鼠体内定植且不致龋性；这些发现表明，临床分离的菌株。MKM33、HG1006和HG988可能是一种有效的替代防龋剂。此外，还建立了一些有效的分离变形链球菌的微生物学方法，从没有或没有龋病经历的学生中分离到了许多变形链球菌，而远缘链球菌则没有分离到。

Mutans streptococci, Streptococcus mutans and Streptococcus sobrinus, have been considered the principal etiological agents of dental caries. The degree of colonization of these organisms correlates with the prevalence of dental carries in, human and experimental animals. An important virulence factor of mutans streptococci promoting caries development is the abilities to colonize firmly to the tooth surface in the presence of sucrose and produce the cariogenic biofilm in situ.The purpose of this research project was to construct or to isolate anti-cariogenic I streptococci useful for caries prevention by replacement therapy. The results have shown that a S. mutans MKM33 isolated from a caries-free student was colonizable and non-cariogenic in rats, that two S. sobrinus like isolates (HG1006 and HG988) from Dutch childs were identified as S. cricetus and both isolates also were colonizable and non-cariogenic in rats, and that a S. gordonii transformant expressing a cyclodextran-synthesizing enzyme gene was colonizable in mice. These findings suggest that the clinical isolates. MKM33, HG1006 and HG988 might be useful for caries prevention by replacement therapy. In addition, some useful microbiological methods for isolation of mutans streptococci were established, and many S. mutans were isolated from students with zero or low of caries experience, but S. sobrinus did not.