Inhibitory effect of plant flavonoid cyanidin on oral microbial biofilm.

UNLABELLED

As primary colonizers of the tooth surface, oral streptococci play a crucial role in dental caries development. Numerous natural compounds, including flavonoids, are emerging as promising agents for inhibiting dental biofilm formation without compromising bacterial viability, underscoring their potential in non-bactericidal antibiofilm strategies. This study investigated the effects and mechanism of action of the unmodified plant flavonoid cyanidin on the growth and sucrose-dependent biofilm formation of oral streptococci, with a particular focus on the cariogenic pathogen . At concentrations above 100 µg/mL, cyanidin significantly inhibited biofilm formation by without impacting bacterial viability. The flavonoid reduced the biomass of surface-associated bacteria and exopolysaccharides (EPS), particularly by inhibiting water-insoluble glucan (WIG) production mediated by the glucosyltransferases GtfB and GtfC. While cyanidin did not exhibit a bactericidal effect on early colonizer streptococci, such as , , , and , it showed a significant inhibitory effect on bacterial acidogenicity and mixed-species streptococcal biofilms in the presence of . Remarkably, cyanidin gradually reduced the proportion of in the mixed biofilm, suggesting a selective impact that may promote a more commensal-dominant community by disrupting glucan production and biofilm competitiveness.

IMPORTANCE

The identification of compounds with potent antibiofilm effects that do not compromise bacterial viability presents a promising strategy for oral health management. By preventing biofilm formation and keeping bacteria in a planktonic state, such agents could enhance bacterial susceptibility to targeted therapies, including probiotics or phage-based treatments. Cyanidin, which exhibits strong antibiofilm activity against oral streptococcal biofilms, reduces bacterial acidogenicity and may promote a more commensal-dominant biofilm , potentially hindering the maturation of cariogenic biofilms.