[Evaluation of cariogenic potential of Streptococcus mutans isolated from caries-free and -active persons: abilities to synthesize water-soluble and -insoluble glucans].

OBJECTIVE

In this study, authors investigated abilities of Streptococcus mutans (serotype c) strains to synthesize water-soluble and water-insoluble glucans.

METHODS

Streptococcus mutans strains were isolated from people with different carious experiences, which were divided into two groups: caries-free (DMFS = 0) group including 19 persons and caries-active group(DMFS > or = 6) including 40 persons. Totally 105 genotypes of Streptococcus mutans strains were obtained, including 22 strains from the caries-free group and 83 strains from the caries-active group. The differences of abilities to synthesize water-soluble and water-insoluble glucans between these two groups were compared in order to find the correlationship between the synthesis of glucans and caries experience. Then, Streptococcus mutans were cultured in TPY liquid medium containing 1% sucrose in an anaerobic incubator at 37 degrees C for 24 hours. Glucans synthesized by Streptococcus mutans was qualified by using infrared spectrophotometry. The amounts of water-soluble and water-insoluble glucans were measured by using the anthron method.

RESULTS

According to the same absorption tops position analysed by infrared spectrophotometry, glucans samples were certified. The amounts of glucans synthesized by Streptococcus mutans strains were different between strains of different genotypes even isolated from the same person. Mostly, the amount of water-insoluble glucans was higher than that of water-soluble glucans between different genotype Streptococcus mutans strains. The oral environments of patients in the caries-active group harbored more Streptococcus mutans strains with higher water-soluble glucans producing ability than those of the caries-free group did (P < 0.05), and patients of the caries-active group also harbored more Streptococcus mutans strains with higher water-insoluble glucans producing ability than those of the caries-free group did(P < 0.01).

CONCLUSIONS

1. Glucosyltranferases of different genotype strains are different in glucans production, and different genotype strains relate to different cariogenic abilities. 2. Glucans was one of cariogenic factors, and water-insoluble glucans was more important than water-soluble glucans in cariogenic ability of Streptococcus mutans. 3. The differences in glucans production of isolated strains might relate to differences in carious experiences.