Use of d-galactose to regulate biofilm growth of oral streptococci

In the oral microbial community, commensals can compete with pathogens and reduce their colonization in the oral cavity. A substance that can inhibit harmful bacteria and enrich beneficial bacteria is required to maintain oral health. The purpose of this study was to examine the effect of d-galactose on the biofilm formation of the cariogenic bacteria Streptococcus mutans and oral commensal streptococci and to evaluate their use in solution and in paste form. Biofilms of S. mutans, Streptococcus oralis, and Streptococcus mitis were formed on saliva-coated glass slips in the absence or presence of d-galactose and evaluated by staining with 1 % crystal violet. d-Galactose significantly inhibited the biofilm formation of S. mutans at concentrations ranging from 2 μM to 200 mM but increased the biofilm formation of S. oralis and S. mitis at concentrations of 2-200 mM. d-Galactose significantly inhibited three glucosyltransferase genes, gtfB, gtfC, and gtfD. The effect of d-galactose in the form of solution and paste was evaluated using bovine teeth. Pretreatment with 100 mM d-galactose on bovine teeth resulted in significantly reduced S. mutans biofilm formation. Our results suggest that d-galactose can be a candidate substance for the development of oral hygiene products to prevent caries by inhibiting the biofilm formation of S. mutans and simultaneously increasing the biofilm formation of commensal oral streptococci.