Epigallocatechin gallate reduces the virulence of cariogenic Streptococcus mutans biofilm by affecting the synthesis of biofilm matrix components

Introduction There have been reports on the effects of epigallocatechin gallate (EGCG) against Streptococcus mutans viability and acidogenesis. However, the effects of EGCG on the virulence of S. mutans biofilm development have yet to be fully investigated using validated cariogenic biofilm models. Objective Thus, this study aimed to evaluate the effects of EGCG on S. mutans biofilm virulence using a validated cariogenic model and clinically relevant treatment regimens, twice a day for 1.5minutes. Methods The effects of EGCG on the morphology and 3D structure of the biofilms were evaluated by scanning electron (SEM) and confocal laser scanning microscopy, respectively. Results No significant change in S. mutans viability or culture medium pH were observed when comparing EGCG-treated and NaCl treated biofilms. EGCG significantly reduced the accumulation of soluble and insoluble polysaccharides, resulting in the formation of a biofilm with interspaced exopolysaccharide-microcolony complexes unevenly distributed on enamel. The SEM images of the biofilm treated with EGCG depict multilayers of cells arranged in short chains of microorganisms adhered to an unstructured matrix, which is not continuous and does not enmesh or protect the microorganisms entirely. Importantly, confocal images demonstrated that treatment with EGCG affected the 3D structure and organization of S. mutans biofilm, which presented a biofilm matrix more confined to the location of the microcolonies. Conclusion In conclusion, EGCG lowered the virulence of S. mutans matrix-rich biofilm by reducing the synthesis of biofilm matrix components, altering the biofilm matrix structure, organization, and distribution.