Collagen Peptide in a Combinatorial Treatment with Lactobacillus rhamnosus Inhibits the Cariogenic Properties of Streptococcus mutans: An In Vitro Study

How probiotics, prebiotics, synbiotics, and postbiotics prevent dental caries: an oral microbiota perspective

Dental caries, a highly prevalent oral disease, impacts a significant portion of the global population. Conventional approaches that indiscriminately eradicate microbes disrupt the natural equilibrium of the oral microbiota. In contrast, biointervention strategies aim to restore this balance by introducing beneficial microorganisms or inhibiting cariogenic ones. Over the past three decades, microbial preparations have garnered considerable attention in dental research for the prevention and treatment of dental caries. However, unlike related pathologies in the gastrointestinal, vaginal, and respiratory tracts, dental caries occurs on hard tissues such as tooth enamel and is closely associated with localized acid overproduction facilitated by cariogenic biofilms. Therefore, it is insufficient to rely solely on previous mechanisms to delineate the role of microbial preparations in the oral cavity. A more comprehensive perspective should involve considering the concepts of cariogenic biofilms. This review elucidates the latest research progress, mechanisms of action, challenges, and future research directions regarding probiotics, prebiotics, synbiotics, and postbiotics for the prevention and treatment of dental caries, taking into account the unique pathogenic mechanisms of dental caries. With an enhanced understanding of oral microbiota, personalized microbial therapy will emerge as a critical future research trend.

Anti-Bacterial and Anti-Biofilm Activities of Anandamide against the Cariogenic Streptococcus mutans

Streptococcus mutans is a cariogenic bacterium in the oral cavity involved in plaque formation and dental caries. The endocannabinoid anandamide (AEA), a naturally occurring bioactive lipid, has been shown to have anti-bacterial and anti-biofilm activities against Staphylococcus aureus. We aimed here to study its effects on S. mutans viability, biofilm formation and extracellular polysaccharide substance (EPS) production. S. mutans were cultivated in the absence or presence of various concentrations of AEA, and the planktonic growth was followed by changes in optical density (OD) and colony-forming units (CFU). The resulting biofilms were examined by MTT metabolic assay, Crystal Violet (CV) staining, spinning disk confocal microscopy (SDCM) and high-resolution scanning electron microscopy (HR-SEM). The EPS production was determined by Congo Red and fluorescent dextran staining. Membrane potential and membrane permeability were determined by diethyloxacarbocyanine iodide (DiOC2(3)) and SYTO 9/propidium iodide (PI) staining, respectively, using flow cytometry. We observed that AEA was bactericidal to S. mutans at 12.5 µg/mL and prevented biofilm formation at the same concentration. AEA reduced the biofilm thickness and biomass with concomitant reduction in total EPS production, although there was a net increase in EPS per bacterium. Preformed biofilms were significantly affected at 50 µg/mL AEA. We further show that AEA increased the membrane permeability and induced membrane hyperpolarization of these bacteria. AEA caused S. mutans to become elongated at the minimum inhibitory concentration (MIC). Gene expression studies showed a significant increase in the cell division gene ftsZ. The concentrations of AEA needed for the anti-bacterial effects were below the cytotoxic concentration for normal Vero epithelial cells. Altogether, our data show that AEA has anti-bacterial and anti-biofilm activities against S. mutans and may have a potential role in preventing biofilms as a therapeutic measure.

Effect of Nystatin on Candida albicans - Streptococcus mutans duo-species biofilms

OBJECTIVE

To assess the effect of Nystatin on Candida albicans and Streptococcus mutans duo-species biofilms using an in vitro cariogenic biofilm model.

DESIGN

Biofilms were formed on saliva-coated hydroxyapatite discs under high sugar challenge (1 % sucrose and 1 % glucose), with inoculation of 105CFU/ml S. mutans and 103CFU/ml C. albicans. Between 20 and 68 h, biofilms were treated with 28,000 IU Nystatin solution, 5 min/application, 4 times/day, to mimic the clinical application. Biofilm's three-dimensional structure was assessed using multi-photon confocal microscopy. The expression of C. albicans and S. mutans virulence genes was assessed via real-time PCR. Duplicate discs were used in 3 independent repeats. t-test and Mann-Whitney U test were used to compare outcomes between treatment and control group.

RESULTS

Nystatin treatment eliminated C. albicans in biofilms at 44 h. Nystatin-treated group had a significant reduction of biofilm dry-weight and reduced S. mutans abundance by 0.5 log CFU/ml at 44 and 68 h (p < 0.05). Worth noting that biomass distribution across the vertical layout was altered by Nystatin treatment, resulting in less volume on the substrate layers in Nystatin-treated biofilms compared to the control. Reduction of microcolonies size and volume was also observed in Nystatin-treated biofilms (p < 0.05). Nystatin-treated biofilms formed unique halo-shaped microcolonies with reduced core EPS coverage. Furthermore, Nystatin-treated biofilms had significant down-regulations of S. mutans gtfD and atpD genes (p < 0.05).

CONCLUSIONS

Nystatin application altered the formation and characteristics of C. albicans and S. mutans duo-species biofilms. Therefore, developing clinical regimens for preventing or treating dental caries from an antifungal perspective is warranted.

Biofilm ecology associated with dental caries: Understanding of microbial interactions in oral communities leads to development of therapeutic strategies targeting cariogenic biofilms

A biofilm is a sessile community characterized by cells attached to the surface and organized into a complex structural arrangement. Dental caries is a biofilm-dependent oral disease caused by infection with cariogenic pathogens, such as Streptococcus mutans, and associated with frequent exposure to a sugar-rich diet and poor oral hygiene. The virulence of cariogenic biofilms is often associated with the spatial organization of S. mutans enmeshed with exopolysaccharides on tooth surfaces. However, in the oral cavity, S. mutans does not act alone, and several other microbes contribute to cariogenic biofilm formation. Microbial communities in cariogenic biofilms are spatially organized into complex structural arrangements of various microbes and extracellular matrices. The balance of microbiota diversity with reduced diversity and a high proportion of acidogenic-aciduric microbiota within the biofilm is closely related to the disease state. Understanding the characteristics of polymicrobial biofilms and the association of microbial interactions within the biofilm (e.g., symbiosis, cooperation, and competition) in terms of their potential role in the pathogenesis of oral disease would help develop new strategies for interventions in virulent biofilm formation.