ABSTRACT
OBJECTIVE: Effects of tea catechin epigallocatechin-3-gallate (EGCG) against biofilm formation by Streptococcus mutans and probiotic Lactobacillus casei in Yakult® (LcY) were examined. DESIGN: Biofilms were formed by S. mutans alone (Sm) and co-culture of S. mutans and LcY (Smâ¯+â¯LcY) in the absence or presence of EGCG. The biomass of biofilms, which were sonicated or not, was measured by the crystal violet assay. Biofilm morphology was observed by scanning electron microscopy. Bacterial viability and extracellular polysaccharides were determined by SYTO9/propidium iodide and dextran-conjugated fluorescein staining, respectively, and confocal microscopy. Gene expression of glucosyltransferase was determined by quantitative polymerase chain reaction. RESULTS: While 250⯵g/ml EGCG significantly decreased the biomass and acid production of Sm biofilms, 500⯵g/ml EGCG was required to inhibit Smâ¯+â¯LcY biofilm formation and acid production. EGCG decreased the amount of live bacteria present in both Sm and Smâ¯+â¯LcY biofilms. The level of dead bacteria in Smâ¯+â¯LcY biofilms was higher than in Sm biofilms when formed in the presence of 250⯵g/ml EGCG. EGCG decreased levels of extracellular polysaccharides in Sm and Smâ¯+â¯LcY biofilms. The extent of biofilm removal by sonication was not different between Sm and Sm+LcY biofilms formed in the absence or presence of 62.5 or 125⯵g/ml EGCG. The level of Sm gtfB and gtfD expression in Smâ¯+â¯LcY biofilms was higher than those in the Sm biofilms when formed in the presence of EGCG at 250⯵g/ml. CONCLUSION: The results indicated that LcY might interfere the inhibitory effects of EGCG against biofilm formation by S. mutans.
