Lactobacillus Rhamnosus & Lactobacillus Salivarius Modulate Planktonic and Biofilm State of Cariogenic Streptococcus Mutans

Streptococcus mutans is one of the early colonizers of the oral cavity and contributes to dental caries and decays. Therefore, any intervention that reduces their number in the oral cavity is considered helpful in reducing dental infections. Probiotics confer health benefits and several studies highlighted their curative effects in the oral cavity. In this study, the antimicrobial and biofilm inhibiting potential of Lactobacillus rhamnosus and Lactobacillus salivarius in co-culture with cariogenic bacterium S. mutans was evaluated. S. mutans formed significant biofilm both in the presence and absence of sucrose with OD > 3-4 at 48h and 72h. On the contrary, L. rhamnosus and L. salivarius made weak biofilm as compared to S. mutans. Both the Lactobacillus strains significantly reduced the bacterial load up to 4-5 folds with 70 – 80% biofilm formation of S. mutans in co-culture experiments. The cell-free supernatant of both the Lactobacillus strains also reduced the biofilm formation and bacterial load. Propidium monoazide (PMA) assays also showed a significant reduction of S. mutans count when co-cultured with L. rhamnosus and L. salivarius. Gene expression analysis showed the downregulation of the quorum sensing (LuxS) gene when co-cultured with the Lactobacillus strains. We conclude that L. rhamnosus and L. salivarius can be used to control cariogenic bacteria i.e., S. mutans.