The tea catechin epigallocatechin gallate suppresses cariogenic virulence factors of Streptococcus mutans.

Streptococcus mutans, the primary etiologic agent of dental caries, possesses a series of virulence factors associated with its cariogenicity. Alternatives to traditional antimicrobial treatment, agents selectively inhibiting the virulence factors without necessarily suppressing the resident oral species, are promising. The anticariogenic properties of tea have been suggested in experimental animals and humans. Tea polyphenols, especially epigallocatechin gallate (EGCg), have been shown to inhibit the growth and glucosyltransferases activity of S. mutans. However, their effects on biofilm and cariogenic virulence factors of oral streptococci other than glucosyltransferases have not been well documented. In this study, we investigated the biological effect of EGCg on the virulence factors of S. mutans associated with its acidogenicity and acidurity. The antimicrobial effects of EGCg on S. mutans biofilm grown in chemically defined medium were also examined. EGCg inhibited growth of S. mutans planktonic cells at an MIC of 31.25 µg/ml and a minimal bactericidal concentration (MBC) of 62.5 µg/ml. EGCg also inhibited S. mutans biofilm formation at 15.6 µg/ml (minimum concentration that showed at least 90% inhibition of biofilm formation) and reduced viability of the preformed biofilm at 625 µg/ml (sessile MIC80). EGCg at sub-MIC levels inhibited acidogenicity and acidurity of S. mutans cells. Analysis of the data obtained from real-time PCR showed that EGCg significantly suppressed the ldh, eno, atpD, and aguD genes of S. mutans UA159. Inhibition of the enzymatic activity of F1F0-ATPase and lactate dehydrogenase was also noted (50% inhibitory concentration between 15.6 and 31.25 µg/ml). These findings suggest that EGCg is a natural anticariogenic agent in that it exhibits antimicrobial activity against S. mutans and suppresses the specific virulence factors associated with its cariogenicity.

Tea catechin epigallocatechin gallate inhibits Streptococcus mutans biofilm formation by suppressing gtf genes.

OBJECTIVE: The anti-cariogenic properties of tea have been suggested for decades. Tea polyphenols, especially epigallocatechin gallate (EGCG), have been shown to inhibit dental plaque accumulation, but the exact mechanisms are not clear at present. We hypothesise that EGCG suppresses gtf genes in Streptococcus mutans at the transcriptional level disrupting the initial attachment of S. mutans and thus the formation of mature biofilms. DESIGN: In this study, the effect of EGCG on the sucrose-dependent initial attachment of S. mutans UA159 in a chemically defined medium was monitored over 4 h using a chamber slide model. The effects of EGCG on the aggregation and gtf B, C, D gene expression of S. mutans UA159 were also examined. RESULTS: It was found that EGCG (7.8-31.25 µg/ml) exhibited dose-dependent inhibition of the initial attachment of S. mutans UA159. EGCG did not induce cellular aggregation of S. mutans UA159 at concentrations less than 78.125 µg/ml. Analysis of data obtained from real-time PCR showed that EGCG at sub-MIC level (15.6 µg/ml) significantly suppressed the gtf B, C, D genes of S. mutans UA159 compared with the non-treated control (p < 0.05). CONCLUSIONS: These findings suggest that EGCG may represent a novel, natural anti-plaque agent that inhibits the specific genes associated with bacterial biofilm formation without necessarily affecting the growth of oral bacteria.