In addition, the ability of S. mutans to utilize some extra- and intracellular polysaccharides as short-term storage compounds offers an additional ecological benefit, and simultaneously, increases the amount of acid production and the extent of acidification. The persistence of this aciduric environment leads to selection of highly acid tolerant (and acidogenic) flora [1, 2, 10]; the low pH environment within the biofilm’s matrix results in dissolution of enamel, thus initiating the pathogenesis of dental caries. Clearly, EPS (e.g. glucans) and acidification of the matrix

by S. mutans (and other acidogenic and aciduric organisms) could be primary targets for chemotherapeutic intervention to prevent the formation of cariogenic biofilms. Strategies of controlling biofilm aimed at disrupting bacterial BMN 673 cell line virulence offer an attractive and alternative approach to the traditional antimicrobial therapy based on use of broad spectrum microbiocides [11].

We have followed a novel combination MG-132 solubility dmso therapy using specific naturally occurring compounds and fluoride aiming at disrupting EPS-matrix formation and acidogenicity of S. mutans within biofilms [12, 13]. The strategy is based on their interconnected biological activities; the bioflavonoids (e.g. apigenin or myricetin) are potent inhibitors of glucan synthesis by Gtf enzymes [12, 14] whereas the terpenoids(e.g. tt-farnesol) and fluoride disrupts the proton permeability of S. mutans membrane, affecting its glycolytic activity, production-secretion of Gtfs and acidurance

[10, 15, 16]; fluoride, of course, has additional physicochemical effects [17, 18]. The combination of natural agents with 250 ppm fluoride resulted in enhanced cariostatic science properties of fluoride in vivo, without suppressing the resident oral flora [12, 13]. In this study, we further investigated whether the biological actions of the combination of agents can influence the expression of specific genes of Streptococcus mutans during biofilm formation, and the spatial distribution of bacterial cells and exopolysaccharides in the biofilm’s matrix. Methods Test compounds Myricetin was obtained from Extrasynthese Co. (Genay-Sedex, France). tt-Farnesol and sodium fluoride were purchased from Sigma-Aldrich Co. (St Louis, MO). For this study, we tested 1.0 mM myricetin and 2.5 mM tt-farnesol in combination with sodium fluoride (125 ppm F or 250 ppm F). The concentrations of the natural agents were selected based on data from our previously published and unpublished response to dose studies [13, 19, 20]. Fluoride at 225-250 ppm is a clinically proven anticaries agent, and is the concentration found in most of the currently commercially available fluoride-based mouth rinses as reviewed in Marinho et al. [17] and Zero [18].