Evaluation of surface roughness, wettability and adhesion of multispecies biofilm on 3D-printed resins for the base and teeth of complete dentures.

OBJECTIVE: This study evaluated the surface roughness, wettability and adhesion of multispecies biofilms (Candida albicans, Staphylococcus aureus and Streptococcus mutans) on 3D-printed resins for complete denture bases and teeth compared to conventional resins (heat-polymerized acrylic resin; artificial pre-fabricated teeth). METHODOLOGY: Circular specimens (n=39; 6.0 mm Ø × 2.0 mm) of each group were subjected to roughness (n=30), wettability (n=30) and biofilm adhesion (n=9) tests. Three roughness measurements were taken by laser confocal microscopy and a mean value was calculated. Wettability was evaluated by the contact angle of sessile drop method, considering the mean of the three evaluations per specimen. In parallel, microorganism adhesion to resin surfaces was evaluated using a multispecies biofilm model. Microbial load was evaluated by determining the number of Colony Forming Units (CFU/mL) and by scanning electron microscopy (SEM). Data were subjected to the Wald test in a generalized linear model with multiple comparisons and Bonferroni adjustment, as well as two-way ANOVA (α=5%). RESULTS: The roughness of the conventional base resin (0.01±0.04) was lower than that of the conventional tooth (0.14±0.04) (p=0.023) and 3D-printed base (0.18±0.08) (p<0.001). For wettability, conventional resin (84.20±5.57) showed a higher contact angle than the 3D-printed resin (60.58±6.18) (p<0.001). Higher microbial loads of S. mutans (p=0.023) and S. aureus (p=0.010) were observed on the surface of the conventional resin (S. mutans: 5.48±1.55; S. aureus: 7.01±0.57) compared to the 3D-printed resin (S. mutans: 4.11±1.96; S. aureus: 6.42±0.78). The adhesion of C. albicans was not affected by surface characteristics. The conventional base resin showed less roughness than the conventional dental resin and the printed base resin. CONCLUSION: The 3D-printed resins for base and tooth showed less hydrophobicity and less adhesion of S. mutans and S. aureus than conventional resins.

Measurement and analysis of microbial fluoride resistance in dental biofilm models.

The interactions between communities of microorganisms inhabiting the dental biofilm is a major determinant of oral health. These biofilms are periodically exposed to high concentrations of fluoride, which is present in almost all oral healthcare products. The microbes resist fluoride through the action of membrane export proteins. This chapter describes the culture, growth and harvest conditions of model three-species dental biofilm comprised of cariogenic pathogens Streptococcus mutans and Candida albicans and the commensal bacterium Streptococcus gordonii. In order to examine the role of fluoride export by S. mutans in model biofilms, procedures for generating a strain of S. mutans with a genetic knockout of the fluoride exporter are described. We present a case study examining the effects of this mutant strain on the biofilm mass, acid production and mineral dissolution under exposure to low levels of fluoride. These general approaches can be applied to study the effects of any gene of interest in physiologically realistic multispecies oral biofilms.

Immunorecognition of Streptococcus mutans secreted proteins protects against caries by limiting tooth adhesion.

INTRODUCTION: Childhood caries, a prevalent chronic disease, affects 60-90 % of children in industrialized regions, leading to lesions in both primary and permanent teeth. This condition precipitates hospital admissions, emergency room visits, elevated treatment costs, and missed school days, thereby impeding the child's academic engagement and increasing the likelihood of caries into adulthood. Despite multiple identified risk factors, significant interpersonal variability remains unexplained. The immune system generates a unique antibody repertoire, essential for maintaining a balanced and healthy oral microbiome. Streptococcus mutans is a primary contributor to the development of caries. METHODS: Employing mass spectrometry, we investigated the S. mutans proteins targeted by antibodies in children both with and without caries, delineating a fundamental suite of proteins discernible by the immune systems of a majority of individuals. Notably, this suite was enriched with proteins pivotal for bacterial adhesion. To ascertain the physiological implications of these discoveries, we evaluated the efficacy of saliva in thwarting S. mutans adherence to dental surfaces. RESULTS: Antibodies in most children recognized a core set of ten S. mutans proteins, with additional proteins identified in some individuals. There was no significant difference in the proteins identified by children with or without caries, but there was variation in antibody binding intensity to some proteins. Functionally, saliva from caries-free individuals, but not children with caries, was found to hinder the binding of S. mutans to teeth. These findings delineate the S. mutans proteome targeted by the immune system and suggest that the inhibition of bacterial adherence to teeth is a primary mechanism employed by the immune system to maintain oral balance and prevent caries formation. CONCLUSIONS: These findings enhance our knowledge of the immune system's function in oral health maintenance and caries prevention, shedding light on how immunoglobulins interact with S. mutans proteins. CLINICAL SIGNIFICANCE: Targeting S. mutans proteins implicated in bacterial adhesion could be a promising strategy for preventing childhood caries.

Epithelial responses and Candida albicans pathogenicity are enhanced in the presence of oral streptococci.

Experimental models that consider host-pathogen interactions are relevant for improving knowledge about oral candidiasis. The aim of this study was to assess the epithelial immune responses, Candida penetration of cell monolayers, and virulence during mixed species culture infections. Single species cultures of Candida albicans and mixed cultures (C. albicans, Streptococcus mutans, and Streptococcus sanguinis) were used to infect monolayers of HaCaT and FaDu ATCC HTB-43 cells for 12 h. After infection, IL-18 and IL-34 gene expression was measured to assess epithelial cell immune responses, and lactate dehydrogenase (LDH) activity was measured as an indicator of cell damage. Microscopy determined C. albicans morphology and penetration of fungal cells through the keratinocyte monolayer. Monolayers devoid of infection served as controls. Data were analyzed by an ANOVA one-way test followed by Tukey's post-hoc test (α = 0.05). The results found that IL-18 and IL-34 gene expression and LDH activity were significantly (p < 0.05) upregulated for both cell lines exposed to mixed species cultures compared with C. albicans alone. Candida albicans yeast and hyphae were evident in C. albicans only infections. In contrast, monolayers infected by C. albicans, S. mutans, and S. sanguinis exhibited higher microbial invasion with several hyphal aggregates detected. The presence of streptococci in C. albicans infection enhances the virulence and pathogenicity of the fungus with associated increased immune responses and tissue damage. Extrapolation of these findings to oral infection would indicate the added potential benefit of managing bacterial components of biofilms during treatment.

Adjunctive role of Q10 with Ligilactobacillus salivarius, and Lactiplantibacillus plantarum probiotic Bacteria on the HEp-2 cells viability and adhesion of Streptococcus mutans.

Objective: Various studies have indicated the application of Coenzyme Q10 and probiotic bacteria such as Ligilactobacillus salivarius (L. salivarius) and Lactiplantibacillus plantarum (L. plantarum) in combating periodontal disease. Considering the positive effect of these two on oral health, and the destructive effect of S. mutans, in this study, we investigate the outcomes of the administration of probiotics and Q10 on infected HEp-2 cell viability and S. mutans adhesion in different settings. Methods: A 3-week-old human epidermoid laryngeal (HEp-2) cell line was cultured and exposed to two different probiotics and 3 different doses of Q10 doses. Samples were contaminated by S. mutans immediately (therapeutic setting) and after 3 hours (preventive setting). Eventually, the viability of HEp-2 cells was investigated by MTT. Also, the number of adhered S. mutans was explored by direct and indirect adhesion assays. Results: L. plantarum and L. salivarius protect epithelial cells against S. mutans in both therapeutic and preventive settings, albeit not fully. In contrast, Q10 completely preserves the viability of infected Her HEp-2 cells at all concentrations. The effects of the coexistence of Q10 and probiotics were not quite equal, among which L. salivarius and 5 µg of Q10 form the best results. The microscopic adherence assay of S. mutans revealed that samples containing Q10 had significantly lower adhesion of probiotics and S. mutans to HEp-2 cells. Similarly, plates containing L. salivarius with 5µg or L. plantarum with 1µg Q10 or sole presence of L. salivarius had the lowest S. mutans adherence among others. Also, L. salivarius with 5µg Q10 had one of the highest probiotic adherences. Conclusion: In conclusion, co-administration of Q10 and probiotics especially in presence of L. salivarius with 5µg Q10 could have remarkable effects on HEp-2 cell viability, S. mutans, and probiotic adherence. Nevertheless, our study, for the first time, showed that Q10 might have an anti-bacterial activity by suppressing the adhesion of tested bacteria to HEp-2 cells. This hypothesis, if correct, suggests that due to their different mechanisms, co-prescription of Q10 and probiotics may lead to better clinical responses, especially in the mentiond dose.

Streptococcus salivarius as an Important Factor in Dental Biofilm Homeostasis: Influence on Streptococcus mutans and Aggregatibacter actinomycetemcomitans in Mixed Biofilm.

A disturbed balance within the dental biofilm can result in the dominance of cariogenic and periodontopathogenic species and disease development. Due to the failure of pharmacological treatment of biofilm infection, a preventive approach to promoting healthy oral microbiota is necessary. This study analyzed the influence of Streptococcus salivarius K12 on the development of a multispecies biofilm composed of Streptococcus mutans, S. oralis and Aggregatibacter actinomycetemcomitans. Four different materials were used: hydroxyapatite, dentin and two dense polytetrafluoroethylene (d-PTFE) membranes. Total bacteria, individual species and their proportions in the mixed biofilm were quantified. A qualitative analysis of the mixed biofilm was performed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results showed that in the presence of S. salivarius K 12 in the initial stage of biofilm development, the proportion of S. mutans was reduced, which resulted in the inhibition of microcolony development and the complex three-dimensional structure of the biofilm. In the mature biofilm, a significantly lower proportion of the periodontopathogenic species A. actinomycetemcomitans was found in the salivarius biofilm. Our results show that S. salivarius K 12 can inhibit the growth of pathogens in the dental biofilm and help maintain the physiological balance in the oral microbiome.

pH-activated antibiofilm strategies for controlling dental caries.

Dental biofilms are highly assembled microbial communities surrounded by an extracellular matrix, which protects the resident microbes. The microbes, including commensal bacteria and opportunistic pathogens, coexist with each other to maintain relative balance under healthy conditions. However, under hostile conditions such as sugar intake and poor oral care, biofilms can generate excessive acids. Prolonged low pH in biofilm increases proportions of acidogenic and aciduric microbes, which breaks the ecological equilibrium and finally causes dental caries. Given the complexity of oral microenvironment, controlling the acidic biofilms using antimicrobials that are activated at low pH could be a desirable approach to control dental caries. Therefore, recent researches have focused on designing novel kinds of pH-activated strategies, including pH-responsive antimicrobial agents and pH-sensitive drug delivery systems. These agents exert antibacterial properties only under low pH conditions, so they are able to disrupt acidic biofilms without breaking the neutral microenvironment and biodiversity in the mouth. The mechanisms of low pH activation are mainly based on protonation and deprotonation reactions, acids labile linkages, and H+-triggered reactive oxygen species production. This review summarized pH-activated antibiofilm strategies to control dental caries, concentrating on their effect, mechanisms of action, and biocompatibility, as well as the limitation of current research and the prospects for future study.

The effect of argon cold atmospheric plasma on the metabolism and demineralization of oral plaque biofilms.

Objective: The aim of this study was to design and optimize a cold atmospheric plasma (CAP) device that could be applied in an oral environment and to study its effects on plaque biofilm metabolism and regrowth, as well as microbial flora composition and enamel demineralization. Method: CAP was obtained through a dielectric barrier discharge device; the optical properties were analyzed using emission spectroscopy. The electrochemical analysis of plasma devices includes voltametric characteristic curves and Lissajous. The Streptococcus mutans (UA159) and saliva biofilms were treated in vitro, and the effects of CAP on biofilm metabolism were investigated using MTT and lactate dehydrogenase assays. The duration of antibacterial activity on biofilms was examined, scanning electron microscopy was used to observe the morphology of biofilms, and 16S rRNA sequencing was used to explore the influence of CAP on the microbial flora composition of saliva biofilms. An in vitro model of biofilm-enamel demineralization was designed, and the effect of CAP on enamel demineralization was evaluated by micro surface hardness and micro-CT analysis. Results: CAP had antibacterial proliferative ability toward Streptococcus mutans biofilms and saliva biofilms and was stronger than ultraviolet under the same tested conditions. After 24 h, the antibacterial effect disappeared, which proved the short-term timeliness of its bactericidal ability. CAP can inhibit the acid production of biofilms, and its inhibitory effect on saliva biofilms can be extended to 24 h. CAP had a strong ability to regulate the composition of plaque biofilms, especially for Lactococcus proliferation, a major acid-producing bacterium in microcosm biofilms. The CAP-treated enamels were more acid-tolerant than non-treated controls. Conclusion: CAP had an explicit bactericidal effect on caries-related biofilms, which is a short-term antibacterial effect. It can inhibit the acid production of biofilms and has a downregulation effect on Lactococcus in saliva biofilms. CAP can help reduce demineralization of enamel.

Inhibition of Polymicrobial Biofilms of Candida albicans-Staphylococcus aureus/Streptococcus mutans by Fucoidan-Gold Nanoparticles.

The polymicrobial proliferation and development of complex biofilm morphologies by bacterial and fungal pathogens in the host are some of the key factors contributing to the failure of antimicrobial treatments. The polymicrobial interaction of Candida albicans and some bacterial species has been extensively studied in both in vitro and in vivo model systems. Alternative strategies for disrupting polymicrobial interaction and biofilm formation are constantly needed. Among several alternative strategies, the use of nanoparticles synthesized using a natural product in the treatment of microbial infection has been considered a promising approach. The current study aimed to synthesize gold nanoparticles (AuNPs) using a natural product, fucoidan, and to test their efficacy against mono and duo combinations of fungal (Candida albicans) and bacterial (Staphylococcus aureus/Streptococcus mutans) biofilms. Several methods were used to characterize and study Fu-AuNPs, including UV-vis absorption spectroscopy, FTIR, FE-TEM, EDS, DLS, zeta potential, and XRD. The concentration-dependent inhibition of early-stage biofilms and the eradication of mature biofilms of single species of C. albicans, S. aureus, and S. mutans have been observed. Early biofilms of a dual-species combination of C. albicans and S. aureus/S. mutans were also suppressed at an increasing concentration of Fu-AuNPs. Furthermore, Fu-AuNPs significantly eradicated the established mature biofilm of mixed species. The treatment method proposed in this study, which involves the use of marine-bioinspired nanoparticles, is a promising and biocompatible agent for preventing the growth of polymicrobial biofilms of bacterial and fungal pathogens.

In vitro anti-inflammatory and antibiofilm activities of bacterial lysates from lactobacilli against oral pathogenic bacteria.

Postbiotics are functional biological compounds, such as bacterial lysates (BLs) released from probiotic bacteria. Although postbiotics exert various bioactivities, the anti-inflammatory and antibiofilm activities of BLs against oral pathogenic bacteria have not been investigated. In the present study, pretreatment with BLs extracted from Lactobacillus plantarum and L. rhamnosus GG suppressed the mRNA and protein expression levels of inflammatory mediators induced by the lipopolysaccharide (LPS) of Porphyromonas gingivalis in RAW 264.7 cells. Both BLs attenuated P. gingivalis LPS-induced phosphorylation of mitogen-activated protein kinases (MAPKs) and activation of nuclear factor-κB (NF-κB), suggesting that BLs inhibit periodontal inflammatory responses by regulating the MAPK and NF-κB signaling pathways. Moreover, both BLs interfered with biofilm formation by Streptococcus mutans; however, they did not eradicate the established S. mutans biofilm. Furthermore, both BLs downregulated gtfB, gtfC, and gtfD responsible for biofilm formation by S. mutans, suggesting that BLs reduce the synthesis of extracellular polysaccharide and thereby reduce S. mutans biofilm. Taken together, these results suggest that BLs of L. plantarum and L. rhamnosus GG can attenuate periodontal inflammation and dental caries and thus contribute to the improvement of oral health.

[Materials for Selective Inhibition of Streptococcus mutans and Progress in Relevant Research].

Dental caries is a disease in which chronic progressive destruction of the hard dental tissues occurs under the influence of multiple factors, among which, bacterial infection being the most important one. Dental plaque biofilm is a key factor in the pathogenesis of dental caries. Under normal circumstances, microorganisms within the biofilm maintain a dynamic balance through coordination, competition, and antagonism. However, when the environment changes, the balance in the biofilm will be disrupted, and the number of cariogenic bacteria, especially Streptococcus mutans ( S. mutans), will increase significantly, thereby causing the production of large amounts of organic acids on the tooth surface, tooth demineralization, and the formation of dental caries. Therefore, finding ways to restore the dynamic balance of oral microorganisms through selective inhibition of S. mutans is key to the prevention and treatment of dental caries. Herein, we reviewed the research progress of recent years in the development of materials with selective antibacterial effect, intending to provide references for the further development of drugs for the prevention and treatment of dental caries. Future studies should focus on the following aspects, mechanism, clinical efficacy, chemical modification, and safety, to supplement and make improvements on the existing relevant research, and to promote progress in research and development of drugs for the prevention and treatment of dental caries.

Antagonistic interactions by a high H2 O2 -producing commensal streptococcus modulate caries development by Streptococcus mutans.

Dental caries (tooth-decay) is caused by biofilms harboring polymicrobial communities on teeth that leads to the onset of localized areas of enamel demineralization. Streptococcus mutans has been clinically associated with severe caries in childhood. Although commensal bacteria can combat S. mutans using self-generated antimicrobials such as hydrogen peroxide (H2 O2 ), constant sugar-rich diet consumption disrupts microbial homeostasis shifting toward cariogenic community. Recently, Streptococcus oralis subsp. tigurinus strain J22, an oral isolate, was identified as a uniquely potent H2 O2 producer. Here, we assess whether a high H2 O2 -producing commensal streptococcus can modulate the spatial organization and virulence of S. mutans within biofilms. Using an experimental biofilm model, we find that the presence of S. oralis J22 can effectively inhibit the clustering, accumulation, and spatial organization of S. mutans on ex vivo human tooth surface, resulting in significant reduction of enamel demineralization. Notably, the generation of H2 O2 via pyruvate oxidase (SpxB) from S. oralis J22 is not repressed by sugars (a common repressor in other mitis group streptococci), resulting in enhanced inhibition of S. mutans growth (vs. Streptococcus gordonii). We further investigate its impact on biofilm virulence using an in vivo rodent caries model under sugar-rich diet. Coinfection of S. mutans with S. oralis results in reduced caries development compared to either species infected alone, whereas coinfection with S. gordonii has negligible effects, suggesting that the presence of an efficient, high H2 O2 -producer can disrupt S. mutans virulence. This work demonstrates that oral isolates with unusual high H2 O2 production may be capable of modulating biofilm cariogenicity in vivo. The findings also highlight the importance of bacterial antagonistic interactions within polymicrobial communities in health and in disease-causing state.

The oral bacterium Streptococcus mutans promotes tumor metastasis by inducing vascular inflammation.

Recent studies have demonstrated a relationship between oral bacteria and systemic inflammation. Endothelial cells (ECs), which line blood vessels, control the opening and closing of the vascular barrier and contribute to hematogenous metastasis; however, the role of oral bacteria-induced vascular inflammation in tumor metastasis remains unclear. In this study, we examined the phenotypic changes in vascular ECs following Streptococcus mutans (S. mutans) stimulation in vitro and in vivo. The expression of molecules associated with vascular inflammation and barrier-associated adhesion was analyzed. Tumor metastasis was evaluated after intravenous injection of S. mutans in murine breast cancer hematogenous metastasis model. The results indicated that S. mutans invaded the ECs accompanied by inflammation and NF-κB activation. S. mutans exposure potentially disrupts endothelial integrity by decreasing vascular endothelial (VE)-cadherin expression. The migration and adhesion of tumor cells were enhanced in S. mutans-stimulated ECs. Furthermore, S. mutans-induced lung vascular inflammation promoted breast cancer cell metastasis to the lungs in vivo. The results indicate that oral bacteria promote tumor metastasis through vascular inflammation and the disruption of vascular barrier function. Improving oral hygiene in patients with cancer is of great significance in preventing postoperative pneumonia and tumor metastasis.

Anti-Biofilm Activities of Chinese Poplar Propolis Essential Oil against Streptococcus mutans.

Streptococcus mutans (S. mutans) is a common cariogenic bacterium that secretes glucosyltransferases (GTFs) to synthesize extracellular polysaccharides (EPSs) and plays an important role in plaque formation. Propolis essential oil (PEO) is one of the main components of propolis, and its antibacterial activity has been proven. However, little is known about the potential effects of PEO against S. mutans. We found that PEO has antibacterial effects against S. mutans by decreasing bacterial viability within the biofilm, as demonstrated by the XTT assay, live/dead staining assay, LDH activity assay, and leakage of calcium ions. Furthermore, PEO also suppresses the total of biofilm biomasses and damages the biofilm structure. The underlying mechanisms involved may be related to inhibiting bacterial adhesion and GTFs activity, resulting in decreased production of EPSs. In addition, a CCK8 assay suggests that PEO has no cytotoxicity on normal oral epithelial cells. Overall, PEO has great potential for preventing and treating oral bacterial infections caused by S. mutans.

Discovery of Novel Iminosugar Compounds Produced by Lactobacillus paragasseri MJM60645 and Their Anti-Biofilm Activity against Streptococcus mutans.

The oral cavity contains a number of microbes. They interact with each other and play an important role in human health. Among oral cariogenic microbes, Streptococcus mutans is recognized a major etiological bacteria of dental caries. Lactobacilli strains have been promoted as possible probiotic agents against S. mutans. However, their inhibitory mechanism has not been well elucidated yet. In the present study, two new compounds with strong antibiofilm activities were purified from the culture supernatant of Lactobacillus paragasseri MJM60645, which was isolated from the human oral cavity. These compounds showed strong inhibitory activities against S. mutans biofilm formation, with IC50 (concentration at which 50% biofilm was inhibited) of 30.4 µM for compound 1 and 18.9 µM for compound 2. However, these compounds did not show bactericidal activities against S. mutans. Structure elucidation by nuclear magnetic resonance (NMR) and mass spectrometry showed that compound 1 was composed of two arabinofuranose iminosugars jointed with one glycerol and oleic acid, and compound 2 was composed of two arabinofuranose iminosugars jointed with one glycerol and nervonic acid. To the best of our knowledge, these structures were discovered for the first time in this study. Treatment of S. mutans with compound 1 strongly downregulated expression levels of genes related to biofilm formation, including gtfB, gtfC, gtfD, gbpB, brpA, spaP, ftf, and smu0630 without affecting the expression of comDE or relA. This study provides new insights into novel molecules produced by Lactobacillus to regulate the pathogenesis of S. mutans, facilitating a better understanding of the mechanism for interactions between Lactobacillus and S. mutans. IMPORTANCE In this study, we isolated lactic acid bacteria that inhibit streptococcal biofilm from the oral cavity of infants and identified two novel compounds from the supernatant of their culture broth. The two compounds are structurally similar, and both consist of iminosugars, glycerol, and unsaturated fatty acid. A search of the SciFinder database revealed that these structures are novel and were discovered for the first time in this study. Mechanism studies have shown that these compounds can inhibit the expression of biofilm synthesis-related genes. This is the first report that lactic acid bacteria inhibit streptococcal biofilms by small molecules with new chemical structures. This study not only expands the understanding of natural products derived from lactic acid bacteria but also provides a new paradigm for the understanding of the interaction of bacteria in the oral microbiota.

Inhibition of Biofilm Formation and Virulence Factors of Cariogenic Oral Pathogen Streptococcus mutans by Shikimic Acid.

Streptococcus mutans is known as an important oral pathogen causing dental caries, a widespread oral infectious disease. S. mutans synthesize exopolysaccharide (EPS) using glucosyltransferases (Gtfs), resulting in biofilm formation on the tooth surface. Bacterial cells in the biofilms become strongly resistant to a harsh environment, such as antibiotics and host defense mechanisms, making biofilm-based infections difficult to eliminate. Discovering novel antibiofilm agents, especially from natural products, helps to develop effective strategies against this kind of diseases. The present study investigated the inhibitory effect of shikimic acid (SA), one abundant compound derived from Illicium verum extract, on the biofilm formation of S. mutans. We found SA can reduce the EPS synthesized by this oral pathogen and modulate the transcription of biofilm formation related genes, leading to fewer bacterial cells in its biofilm. SA also interacted with cell membrane and membrane proteins, causing damage to bacterial cells. Ex vivo testing of biofilm formation on bovine teeth showed SA strongly decreased the number of S. mutans cells and the number of EPS accumulated on dental enamel surfaces. Moreover, SA exhibits almost no toxicity to human oral cells evaluated by in vitro biocompatibility assay. In conclusion, shikimic acid exhibits remarkable antibiofilm activity against S. mutans and has the potential to be further developed as a novel anticaries agent. IMPORTANCE Natural products are an important and cost-effective source for screening antimicrobial agents. Here, we identified one compound, shikimic acid, from Illicium verum extract, exhibiting antimicrobial activity against S. mutans proliferation. It also inhibits biofilm formation of this bacteria through decreasing Gtf expression and EPS synthesis. Furthermore, this compound exhibits no significant cytotoxicity at its MIC against S. mutans, providing evidence for its clinical application.

Dual Action Nitric Oxide and Fluoride Ion-Releasing Hydrogels for Combating Dental Caries.

Demineralization and breakdown of tooth enamel are characterized by a condition called dental caries or tooth decay, which is caused by two main factors: (1) highly acidic food intake without proper oral hygiene and (2) overactive oral bacteria generating acidic metabolic byproducts. Fluoride treatments have been shown to help rebuild the hydroxyapatite structures that make up 98% of enamel but do not tackle the bacterial overload that continues to threaten future demineralization. Herein, we have created a dual-function Pluronic F127-alginate hydrogel with nitric oxide (NO)- and fluoride-releasing capabilities for the two-pronged treatment of dental caries. Analysis of the hydrogels demonstrated porous, shear-thinning behaviors with tunable mechanical properties. Varying the weight percent of the NO donor S-nitrosoglutathione (GSNO) within the hydrogel enabled physiologically actionable NO release over 4 h, with the fabricated gels demonstrating storage stability over 21 days. This NO-releasing capability resulted in a 97.59% reduction of viable Streptococcus mutans in the planktonic state over 4 h and reduced the preformed biofilm mass by 48.8% after 24 h. Delivery of fluoride ions was confirmed by a fluoride-sensitive electrode, with release levels resulting in the significant prevention of demineralization of hydroxyapatite discs after treatment with an acidic demineralization solution. Exposure to human gingival fibroblasts and human osteoblasts showed cytocompatibility of the hydrogel, demonstrating the potential for the successful treatment of dental caries in patients.

E-Cigarette Aerosol Exposure Favors the Growth and Colonization of Oral Streptococcus mutans Compared to Commensal Streptococci.

E-cigarettes (e-cigs) have drastically increased in popularity during the last decade, especially among teenagers. While recent studies have started to explore the effect of e-cigs in the oral cavity, little is known about their effects on the oral microbiota and how they could affect oral health and potentially lead to disease, including periodontitis and head and neck cancers. To explore the impact of e-cigs on oral bacteria, we selected members of the genus Streptococcus, which are abundant in the oral cavity. We exposed the commensals Streptococcus sanguinis and Streptococcus gordonii and the opportunistic pathogen Streptococcus mutans, best known for causing dental caries, to e-liquids and e-cig aerosols with and without nicotine and with and without menthol flavoring and measured changes in growth patterns and biofilm formation. Our results demonstrate that e-cig aerosols hindered the growth of S. sanguinis and S. gordonii, while they did not affect the growth of S. mutans. We also show that e-cig aerosols significantly increased biofilm formation by S. mutans but did not affect the biofilm formation of the two commensals. We found that S. mutans exhibits higher hydrophobicity and coaggregation abilities along with higher attachment to OKF6 cells than S. sanguinis and S. gordonii. Therefore, our data suggest that e-cig aerosols have the potential to dysregulate oral bacterial homeostasis by suppressing the growth of commensals while enhancing the biofilm formation of the opportunistic pathogen S. mutans. This study highlights the importance of understanding the consequences of e-cig aerosol exposure on selected commensals and pathogenic species. Future studies modeling more complex communities will provide more insight into how e-cig aerosols and vaping affect the oral microbiota. IMPORTANCE Our study shows that e-cigarette aerosol exposure of selected bacteria known to be residents of the oral cavity hinders the growth of two streptococcal commensals while enhancing biofilm formation, hydrophobicity, and attachment for the pathogen S. mutans. These results indicate that e-cigarette vaping could open a niche for opportunistic bacteria such as S. mutans to colonize the oral cavity and affect oral health.

Effect of acid-alkali treatment on serum protein adsorption and bacterial adhesion to porous titanium.

Modification of the titanium (Ti) surface is widely known to influence biological reactions such as protein adsorption and bacterial adhesion in vivo, ultimately controlling osseointegration. In this study, we sought to investigate the correlation of protein adsorption and bacterial adhesion with the nanoporous structure of acid-alkali-treated Ti implants, shedding light on the modification of Ti implants to promote osseointegration. We fabricated nontreated porous Ti (NTPT) by powder metallurgy and immersed it in mixed acids and NaOH to obtain acid-alkali-treated porous Ti (AAPT). Nontreated dense sample (NTDT) served as control. Our results showed that nanopores were formed after acid-alkali treatment. AAPT showed a higher specific surface area and became much more hydrophilic than NTPT and NTDT (p < 0.001). Compared to dense samples, porous samples exhibited a lower zeta potential and higher adsorbed protein level at each time point within 120 min (p < 0.001). AAPT formed a thicker protein layer by serum precoating than NTPT and NTDT (p < 0.001). The main adsorbed proteins on AAPT and NTPT were albumin, α1 antitrypsin, transferrin, apolipoprotein A1, complement C3 and haptoglobin α1 chain. The amounts of bacteria adhering to the serum-precoated samples were lower than those adhering to the nonprecoated samples (p < 0.05). Lower-molecular-weight proteins showed higher affinity to porous Ti. In conclusion, acid-alkali treatment facilitated protein adsorption by porous Ti, and the protein coating tended to prevent bacteria from adhering. These findings may be utilized for Ti implant modification aimed at reducing bacterial adhesion and enhancing osseointegration. Graphical abstract.

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

Dental caries is caused by the formation of cariogenic biofilm, leading to localized areas of enamel demineralization. Streptococcus mutans, a cariogenic pathogen, has long been considered as a microbial etiology of dental caries. We hypothesized that an antagonistic approach using a prebiotic collagen peptide in combination with probiotic Lactobacillus rhamnosus would modulate the virulence of this cariogenic biofilm. In vitro S. mutans biofilms were formed on saliva-coated hydroxyapatite discs, and the inhibitory effect of a combination of L. rhamnosus and collagen peptide on S. mutans biofilms were evaluated using microbiological, biochemical, confocal imaging, and transcriptomic analyses. The combination of L. rhamnosus with collagen peptide altered acid production by S. mutans, significantly increasing culture pH at an early stage of biofilm formation. Moreover, the 3D architecture of the S. mutans biofilm was greatly compromised when it was in the presence of L. rhamnosus with collagen peptide, resulting in a significant reduction in exopolysaccharide with unstructured and mixed bacterial organization. The presence of L. rhamnosus with collagen peptide modulated the virulence potential of S. mutans via down-regulation of eno, ldh, and atpD corresponding to acid production and proton transportation, whereas aguD associated with alkali production was up-regulated. Gly-Pro-Hyp, a common tripeptide unit of collagen, consistently modulated the cariogenic potential of S. mutans by inhibiting acid production, similar to the bioactivity of a collagen peptide. It also enhanced the relative abundance of commensal streptococci (S. oralis) in a mixed-species biofilm by inhibiting S. mutans colonization and dome-like microcolony formation. This work demonstrates that food-derived synbiotics may offer a useful means of disrupting cariogenic communities and maintaining microbial homeostasis.