EGCG Effect on Nicotine-Induced Streptococcus Mutans Anaerobic Biofilm Formation

Objectives: The effect of green tea and an important anti-oxidant in tea, epigallocatechin gallate (EGCG), on Streptococcus mutans in the presence of nicotine has demonstrated inhibition of biofilm formation under aerobic conditions. We have also demonstrated that S. mutans forms more biofilm mass when grown anaerobically compared to aerobic incubation. The present study aimed to determine the effect of green tea and EGCG on S. mutans biofilm formation anaerobically in the presence of nicotine and compare that to aerobic incubation.
Methods: The strain used in our experiment was S. mutans UA159 serotype c. We assessed S. mutans ability to form sucrose-induced biofilm. We inoculated S. mutans into sterile 96-well flat bottom microtiter plates; half for aerobic and anaerobic incubation with EGCG and half with green tea. The nicotine concentrations investigated in this study ranged between 0-32 mg/ml. A Gas-Pak jar was used to provide an anaerobic growth environment. Biofilm formation was established by crystal violet staining. The absorbance was recorded using a microplate reader at 490 nm.
Results: Aerobically, we found a statistically significant reduction in biofilm formation with the addition of EGCG up to 8 mg/ml of nicotine. A similar reduction was observed anaerobically at 0.25, 1, 4, 8 and 16 mg/ml. In contrast, biofilm formation was higher with the addition of green tea at nicotine levels 0.5-4 mg/ml aerobically, and 1 and 2 mg/ml anaerobically. Compared to EGCG, biofilm formation with green tea was found statistically significant at 2 mg/ml of nicotine.
Conclusions: While EGCG inhibits S. mutans biofilm under both aerobic and anaerobic conditions, green tea increased biofilm formation suggesting the importance of EGCG in modulating oral bacterial growth.