Aims: To evaluate the ability of the broad-spectrum lantibiotic, lacticin 3147, to prevent Streptococcus mutans biofilm formation and disrupt existing biofilms. Methods and Results: Minimum inhibitory concentrations (MIC) and minimum biofilm inhibitory concentrations of purified lacticin 3147 were determined using a microdilution method. Lacticin 3147 effectively inhibited planktonic Strep. mutans, with MIC of 1.9-3.8 mu mol l(-1). Time-kill kinetic studies confirmed that lacticin 3147 exhibited bactericidal activity against Strep. mutans at 38 mu mol l(-1) (or 10x MIC). The effect of lacticin 3147 on biofilm formation and reduction was also determined. Exposure to 6 3-mu mol l(-1) lacticin 3147 (2x MIC) resulted in substantial reductions in Strep. mutans biofilm formation while lacticin 3147 was less effective against 1-day-old biofilms. Culture-based analyses revealed that lacticin 3147 (50 mu mol l(-1)) significantly inhibited Streptococcus spp. present in human saliva (P < 0.05) with an approximate 4-log reduction in viability compared with the control. Conclusions: These results indicate that lacticin 3147 may be an effective therapy against Strep. mutans and was shown to substantially attenuate its ability to form a biofilm. Significance and Impact of the Study: Lacticin 3147 has the potential to be a useful adjunct to traditional oral therapeutic approaches in addition to its use as a bioactive ingredient for food applications.