Putative Prebiotics Can Disrupt 3D Architecture and Modulate the Microbial Population to Prevent Cariogenic Biofilm Build-Up In Vitro

Background/Objective(s)/Introduction: Prebiotics are substances that metabolically favor certain microorganisms of a microbiome, promoting homeostasis. Dental biofilm microorganisms are enmeshed in a matrix of extracellular polymeric substances that they produce. A diet rich in sucrose can lead to a dysbiotic biofilm associated with microbial acid production and a change in the matrix’s composition (mostly water-insoluble glucans), which allows acids to accumulate within biofilms and contribute to teeth demineralization. Thus, the effects of putative prebiotics were evaluated to verify their impact on exopolysaccharides, the microbial population, and biofilm formation. Materials and methods: Five potential prebiotics (N-acetyl-d-glucosamine, arginine, proline, sodium nitrate, and urea) were evaluated compared with a substance-free control. A Streptococcus mutans biofilm model on polystyrene plates was used to determine the concentrations of substances that would inhibit sucrose-derived biofilm formation. Selected concentrations were then used to verify the production of insoluble glucans by glucosyltransferase B. Afterward, S. mutans and mixed-species (S. mutans, Actinomyces naeslundii, and Streptococcus gordonii) biofilms were grown on saliva-coated hydroxyapatite discs with sucrose to evaluate the microbial population and 3D biofilm structure (exopolysaccharides and bacterial biovolume). Lastly, a microcosm biofilm formed on polystyrene plates was used to assess the effects of the substances on biomass and the proportion of distinct viable microbial populations. Results: Only arginine inhibited insoluble glucan production and S. mutans biofilm accretion (≅ 90%). Arginine and proline inhibited a biofilm build-up in mixed-species and microcosm models and modulated microbial counts of species associated with cariogenic biofilms. In the microcosm biofilm, urea hindered biomass accretion in initial biofilms and the counts of aciduric microbiota and fungi, but N-acetyl-d-glucosamine stimulated microbial growth. Sodium nitrate affected the size and shape of microcolonies in S. mutans and mixed-species biofilms. Conclusion(s): Among the substances tested, arginine and proline modulated the microbial population and hindered biofilm accretion, especially arginine, which hampered glucan production. However, urea is the only substance able to impede fungal growth.