Effect of glucose concentrations on initial adherence of Streptococcus mutans

Objectives: To study the effect of different concentration of glucose on the initial adherence of Streptococcus mutans(S. mutans) to saliva-coated hydroxyapatite(SHA), and to compare the initial adherence of S. mutans from caries-active subjects with that of S. mutans from caries-free subjects. Methods: Each 10 clinical isolates of S. mutans from caries - active and caries- free subjects were used in this study. A strain UA159 of S. mutans was also included in this experiment. SHA was used to simulate tooth surface in oral cavity. S. mutans clinical isolates and strain UA159 were cultured in TPY liquid medium containing 3H-TDR in the same radioactive concentration(370KBq/ml)and glucose in 0.2%, 1%, 5% concentration. After being cultured in an anaerobic incubator for 18 hours, S. mutans were radiolabelled by 3H-TDR. SHA and radiolabelled bacterial liquid (A550nm=0.52) were mixed for 90 minutes, samples were assayed by using liquid scintillation counter, and binding abilities of strains were evaluated by the count per minute (CPM). Results: The initial adherence ability of S. mutans from caries- active group was higher than that of S. mutans from caries- free group(P<0.05). And the initial adherence ability of S. mutans cultured in different concentration of glucose was also significantly different(P<0.05), 5% glucose group had the highest adherence ability, and 0.2% glucose group had the lowest adherence ability. Conclusions: (1) Difference of the initial adherence of S. mutans might relate to difference of carious experiences; (2) Glucose may play important roles in S. mutans initial adherence , to some extent, S. mutans cultured in the higher concentration of glucose has the higher initial adherence property.