Growth and acid production profile of Streptococcus mutans 6715 in the presence of tannic acid.

Salvadora persica (Miswak) and certain related Nigerian chewing stick plants are used as a toothbrush substitute for oral hygiene. One of the proposed active substances in these chewing sticks is tannic acid, which has been shown to possess antibacterial and antifungal properties. This study was carried out to investigate the effect of tannic acid (TA) on the growth and acid production of Streptococcus mutans 6715. Various concentrations of TA prepared with trypticase soy broth were inoculated with Streptococcus mutans 6715 and incubated at 37oC. Growth was monitored by OD measured at specific intervals. In acid production experiment, cells of the bacterium were used as non-growing cell suspension in a combined buffer solution of 40 mM NaHCO3 and 6 mM K2HPO4 to which various concentrations of TA were added. Data showed that TA was bacteriostatic at concentrations of 10, 100, 200 and 300 mg/ml and bactericidal at 500 mg/ml. However, acid production of Streptococcus mutans 6715 was not affected by presence of TA. Growth inhibition of Streptococcus mutans 6715 demonstrated by this study suggests that tannic acid may play an important role in restricting plaque accumulation and hence dental caries.King Saud Universit