Reducing Dental Plaque Formation with a Novel Bacterial Nuclease

Methods: Biofilms were developed on the surface of polystyrene microtitre plates from strains of oral bacteria or from natural microbial populations in human saliva. Salivary inoculae from 6 volunteers were used for establishing mixed-species biofilm populations. Mixed species biofilms were incubated for up to 20 hours at 37oC either aerobically in the presence of 2% sucrose or anaerobically. Single strains were incubated anaerobically. NucB (1 µg ml-1) was applied to cultures either before or after biofilm development. Residual biofilm was quantified by staining with crystal violet.

Results: NucB inhibited and/or dispersed a variety of single strain and mixed-species oral biofilms. In mixed-species cultures, reductions in biofilm biomass of up to 66% were observed when NucB was added prior to biofilm formation compared with untreated controls. Addition of NucB to preformed biofilms resulted in up to 42% reduction of the attached biofilm. Certain individual bacterial strains were extremely sensitive to NucB; biofilm extent was reduced by up to 90% in the presence of the enzyme. Nuclease sensitivity of biofilms from natural salivary inoculae was dependent on incubation conditions (anaerobic versus aerobic with sucrose) and the time span of biofilm development.

Conclusions: We have shown that the addition of nuclease inhibits and disperses biofilms grown in vitro, suggesting that eDNA may play a role in oral biofilm formation in vivo. Therefore, microbial nucleases such as NucB may be highly effective at controlling the accumulation of dental plaque.