Search Results (27)

The purpose of this study was to evaluate the gene expression pattern of the caries-inhibiting effect of Cudrania tricuspidata (C. tricuspidata) extract on cariogenic bacteria Streptococcus mutans (S. mutans). We examined bacterial growth, tooth surface attachment, biofilm formation, acid production, free calcium release, and toxicity gene expression. The major components of the extract were investigated by UPLC-Q-TOF-MS analysis. Exposure to C. tricuspidata inhibited bacterial growth and attachment at concentrations of ≥15 μg/mL. Inhibition effects on biofilm formation, acid production, and free calcium release due to acid production were observed at concentrations ≥ 30 μg/mL. S. mutans virulence gene expression analysis showed that it inhibited the expression of gbpB and spaP, which mediate bacterial attachment to the tooth surface, and that of genes contributing to biofilm formation (gtfB, gtfC, and gtfD) and acid resistance (brpA and relA), and regulation (vicR). Analysis using UPLC–Q–TOF–MS/MS showed that the main component was phenylpropanoids. These results suggest that C. tricuspidata may inhibit the cariogenic properties associated with the expression of caries-related genes in S. mutans. Full article

This study aimed to identify the inhibitory effect of Agastache rugosa essential oil (AREO) on the cariogenic properties of Streptococcus mutans, which causes dental caries and dental plaque formation. After extracting the AREO, their effects on the growth and acid production of S. mutans were examined. Furthermore, S. mutans biofilm formation was observed on the resin teeth surface. The effect on the expression of biofilm-related genes of S. mutans was measured using real-time PCR. AREO components were analyzed using gas chromatography (GC) and GC-mass spectrometry (MS). The growth and acid production of S. mutans were significantly inhibited at concentrations of 0.02 mg/mL or higher of AREO. At 0.04 mg/mL, inhibition was similar to that of the positive control, 0.1% NaF. AREO suppressed the expression of virulence factors such as gtfB, gtfC, gtfD, gbpB, SpaP, brpA, relA, and vicR at concentrations of 0.02 mg/mL or higher. As a result of GC and GC-MS analyses, the main components of AREO included estragole, limonene, and β-caryophyllene. These results suggest that A. rugosa may be a useful agent for inhibiting the cariogenic properties of S. mutans. Full article

Streptococcus mutans (S. mutans) antisense vicK RNA (ASvicK) is a non-coding RNA that regulates cariogenic virulence and metabolic activity. Dimethylaminohexadecyl methacrylate (DMAHDM), a quaternary ammonium methacrylate used in dental materials, has strong antibacterial activity. This study examined the effects of S. mutans ASvicK on DMAHDM susceptibility and their combined impact on inhibiting S. mutans biofilm formation and protecting enamel hardness. The parent S. mutans UA159 and ASvicK overexpressing S. mutans (ASvicK) were tested. The minimum inhibitory concentration (MIC) and minimum bactericidal concentrations for planktonic bacteria (MBC-P) and biofilms (MBC-B) were measured. As the ASvicK MBC-B was 175 μg/mL, live/dead staining, metabolic activity (MTT), colony-forming units (CFUs), biofilm biomass, polysaccharide, and lactic acid production were investigated at 175 μg/mL and 87.5 μg/mL. The MIC, MBC-P, and MBC-B values for DMAHDM for the ASvicK strain were half those of the UA159 strain. In addition, combining S. mutans ASvicK with DMAHDM resulted in a significant 4-log CFU reduction (p < 0.05), with notable decreases in polysaccharide levels and lactic acid production. In the in vitro cariogenic model, the combination achieved the highest enamel hardness at 67.1% of sound enamel, while UA159 without DMAHDM had the lowest at 16.4% (p < 0.05). Thus, S. mutans ASvicK enhanced DMAHDM susceptibility, and their combination effectively inhibited biofilm formation and minimized enamel demineralization. The S. mutans ASvicK + DMAHDM combination shows great potential for anti-caries dental applications. Full article

Streptococcus mutans is a major cariogenic organism because of its ability to form biofilms on tooth surfaces. Bacteriocins produced by S. mutans (known as mutacins) are indirect pathogenic factors that play a role in the persistence of this microbe in the oral environment. Nattokinase, a subtilisin-like alkaline serine protease, potently inhibits biofilm formation without affecting S. mutans growth. However, effective strategies utilizing nattokinase to control mutacin production by S. mutans are lacking. In this study, we evaluated the effect of nattokinase on mutacin activity in 46 strains of S. mutans with different mutacin genotypes isolated from the dental plaques of pediatric patients with caries. Nattokinase reduced the activity of mutacin against oral streptococci at a concentration of 1 mg/mL in all clinical isolates. Furthermore, nattokinase reduced the expression of non-lantibiotic mutacin structural genes (nlmABCD) and inactivated the extracellular competence-stimulating peptide involved in comDE activation, which regulates non-lantibiotic mutacin gene expression. These results suggest that nattokinase may reduce the virulence of S. mutans and could potentially be used as a new caries-preventive agent as an alternative to conventional drug treatments. Full article

Ramulus mori has been widely used in traditional Chinese medicine because of its physiological activities, including antibacterial, anti-inflammatory, and antioxidant activities. Antimicrobial properties of Ramulus mori extract have been well described. However, no information is available regarding on Ramulus mori oligosaccharides (RMOS). The aim of this study was to investigate the effects of RMOS on the growth and virulence properties of the cariogenic bacterium Streptococcus mutans. The effects of RMOS on the biofilm structure and virulence gene expression of S. mutans were also evaluated, and the results were compared with the effects of commercial prebiotic galactooligosaccharides. RMOS were found to have an antibacterial effect against S. mutans, resulting in significant reductions in acid production, lactate dehydrogenase activity, adhesion, insoluble extracellular polysaccharide production, glucosyltransferase activity, and biofilm formation in a dose-dependent manner. Moreover, the biofilm structure was visibly damaged. A quantitative real-time PCR assay revealed downregulation of virulence gene-regulated acid production, polysaccharide production, adhesion, biofilm formation, and quorum sensing. These findings suggest that RMOS may be a promising natural product for the prevention of dental caries. Full article

We previously developed a novel lactotransferrin-derived antimicrobial peptide, LF-1, with selective antibacterial activity against the characteristic cariogenic bacterium Streptococcus mutans. This study further investigated the effects of LF-1 on the cariogenic virulence factors of S. mutans and evaluated the changes in virulence-associated enzymes and genes; the viability, acidogenicity, and aciduricity of planktonic S. mutans; and initial colonisation and biofilm formation after treatment with LF-1. The method of qRT-PCR was used to evaluate S. mutans virulence-associated gene expression. LF-1 interfered with the cell viability of S. mutans within 6 h. LF-1 inhibited the acidogenicity and aciduricity of S. mutans, with reduced lactic acid production and survival in a lethal acidic environment, and inactivated lactate dehydrogenase and F₁F₀-ATPase activity. LF-1 decreased surface-adherent S. mutans within 60 min and inhibited S. mutans biofilm formation, where scanning electron microscopy and confocal laser scanning microscopy showed reduced extracellular matrix and bacteria. LF-1 downregulates S. mutans virulence-associated gene expression. LF-1 inhibited the growth and cariogenic virulence factors of S. mutans in vitro with a reduction in key enzymatic activity and downregulation of virulence-associated gene expression. LF-1 has promising application prospects in the fight against S. mutans and dental caries. Full article

Bacteria can communicate through an intercellular signaling system referred to as quorum sensing (QS). The QS system involves the production of autoinducers that interact with their respective receptors, leading to the induction of specific signal transduction pathways. The QS systems of the oral cariogenic Streptococcus mutans regulate the maturation of biofilms and affect its virulent properties. We have previously shown that the non-psychoactive compound cannabigerol (CBG) of the Cannabis sativa L. plant has anti-bacterial and anti-biofilm activities towards S. mutans. Here we were interested in investigating the effect of the two QS systems ComCDE and LuxS on the susceptibility of S. mutans to CBG and the anti-QS activities of CBG. This was assessed by using various comCDE and luxS mutant strains and complementation with the respective autoinducers, competence stimulating peptide (CSP) and (S)-4,5-dihydroxy-2,3-pentandione (DPD, pre-AI-2). We found that S. mutans comCDE knockout strains were more sensitive to the anti-bacterial actions of CBG compared to the WT strain. Exogenously added 21-CSP prevented the anti-bacterial actions caused by CBG on the ΔcomC, ΔcomE and ΔluxS mutants, while having no effect on the susceptibility of the WT and ΔcomCDE strains to CBG. Exogenously added DPD increased the susceptibility of WT and ΔluxS to CBG. Vice versa, CBG significantly reduced the 21-CSP-induced expression of comCDE genes and ComE-regulated genes and suppressed the expression of luxS with concomitant reduction in AI-2 production. DPD induced the expression of comCDE genes and ComE-regulated genes, and this induction was repressed by CBG. 21-CSP alone had no significant effect on luxS gene expression, while ΔcomCDE strains showed reduced AI-2 production. In conclusion, our study shows that the susceptibility of S. mutans to CBG is affected by the ComCDE and LuxS QS pathways, and CBG is a potential anti-QS compound for S. mutans. Additionally, we provide evidence for crosstalk between the ComCDE and LuxS QS systems. Full article

The effects of extracts, fractions, and molecules of Casearia sylvestris to control the cariogenic biofilm of Streptococcus mutans were evaluated. First, the antimicrobial and antibiofilm (initial and pre-formed biofilms) in prolonged exposure (24 h) models were investigated. Second, formulations (with and without fluoride) were assessed for topical effects (brief exposure) on biofilms. Third, selected treatments were evaluated via bacterium growth inhibition curves associated with gene expression and scanning electron microscopy. In initial biofilms, the ethyl acetate (AcOEt) and ethanolic (EtOH) fractions from Brasília (BRA/DF; 250 µg/mL) and Presidente Venceslau/SP (Water/EtOH 60:40 and Water/EtOH 40:60; 500 µg/mL) reduced ≥6-logs vs. vehicle. Only the molecule Caseargrewiin F (CsF; 125 µg/mL) reduced the viable cell count of pre-formed biofilms (5 logs vs. vehicle). For topical effects, no formulation affected biofilm components. For the growth inhibition assay, CsF yielded a constant recovery of surviving cells (≅3.5 logs) until 24 h (i.e., bacteriostatic), and AcOEt_BRA/DF caused progressive cell death, without cells at 24 h (i.e., bactericidal). CsF and AcOEt_BRA/DF damaged S. mutans cells and influenced the expression of virulence genes. Thus, an effect against biofilms occurred after prolonged exposure due to the bacteriostatic and/or bactericidal capacity of a fraction and a molecule from C. sylvestris. Full article

Probiotics interfere with pathogenic microorganisms or reinstate the natural microbiome. Streptococcus mutans and Candida albicans are well-known emerging pathogenic bacteria/fungi for dental caries. In this study, three probiotic Lactobacilli strains (Lactobacillus plantarum 8014, L. plantarum 14917, and Lactobacillus salivarius 11741) were tested on S. mutans and C. albicans clinical isolates using a multispecies biofilm model simulating clinical cariogenic conditions. The ten pairs of clinical isolates of S. mutans and C. albicans were obtained from children with severe early childhood caries. Our study findings show a remarkable inhibitory effect of L. plantarum 14917 on S. mutans and C. albicans clinical isolates, resulting in significantly reduced growth of S. mutans and C. albicans, a compromised biofilm structure with a significantly smaller microbial and extracellular matrix and a less virulent microcolony structure. FurTre, plantaricin, an antimicrobial peptide produced by L. plantarum, inhibited the growth of S. mutans and C. albicans. The mechanistic assessment indicated that L. plantarum 14917 had a positive inhibitory impact on the expression of S. mutans and C. albicans virulence genes and virulent structure, such as C. albicans hypha formation. Future utilization of L. plantarum 14917 and/or its antimicrobial peptide plantaricin could lead to a new paradigm shift in dental caries prevention. Full article

Aims: Mutans streptococci include Streptococcus mutans and Streptococcus sobrinus, which can cause tooth decay. The current study aimed to compare their virulence genes with each other and to correlate them with the clinical data of patients. Materials and methods: Altogether 21 S. mutans and 19 S. sobrinus strains were investigated, originating from 24 children (age 2.7 ± 0.4 years) and 13 mothers (27.3 ± 3.7). The PCR method was applied to detect 11 virulence genes. Caries indices (dmf, decayed/missing/filled; DMFT, decayed/missing/filled teeth) and SM score (Mutans streptococci amount in saliva) were recorded. Results: Most of the S. mutans strains harbored all the virulence genes studied, while S. sobrinus had significantly fewer genes. The genes gbpA, gbpB, wapA and ftf were present in all isolates of S. sobrinus, the spaP, gtfB, vicR, SMU.1037c and SMU.105 genes were present in 41–88% of the isolates, while gtfD and SMU.104 genes were absent in S. sobrinus strains studied. A positive correlation appeared between the biofilm-related vicR and polysaccharide-production-related gtfD genes. In contrast, another polysaccharide-production-related gtfB gene was present in some cases in strains lacking the vicR or gtfD gene. Positive association was found between the presence of adhesion-related spaP gene in pediatric-derived S. sobrinus strains and an increase in SM score. Conclusions: Differences exist between the two common species of mutans streptococci: strains of S. mutans have more virulence genes than that of S. sobrinus, both crucial and virulence enhancing. Deeper research is needed to clarify the mechanisms behind the increased cariogenicity in cohabitation. Full article

Background: Dental caries commonly occurs during orthodontic treatment because fixed appliances can impede effective oral hygiene practices. This study investigated the effects of fixed orthodontic treatment on dental biofilm maturity and virulence gene (gtfB, ldh, brpA, spaP, luxS, and gbpB) expression. Methods: Dental biofilms and virulence gene expression were determined in 24 orthodontic patients before and after treatment of ≥6 months. A three-tone disclosing gel was used to stain dental biofilm and assess its maturity by its color change—pink (new dental biofilm), purple (mature dental biofilm), and light blue (cariogenic dental biofilm). Gene expression levels were determined using real-time PCR. Results: After fixed orthodontic appliance insertion, the percentage of new dental biofilm decreased, whereas that of cariogenic dental biofilm significantly increased (p < 0.05). There was no significant difference in the percentage of mature dental biofilm (p > 0.05). Fixed orthodontic appliances increased gtfB, ldh, brpA, and gbpB gene expression above 1.5-fold in dental biofilm. In contrast, there was no change in spaP or luxS gene expression after treatment. Conclusions: Fixed orthodontic appliance insertion induced ecological changes and cariogenic virulence gene expression in dental biofilm. Full article

Background: Secondary caries often result in a high failure rate of resin composite restoration. Herein, we studied the dodecylmethylaminoethyl methacrylate–modified resin adhesive (DMAEM@RA) to investigate its pH-responsive antimicrobial effect on Streptococcus mutans and Candida albicans dual-species biofilms and on secondary caries. Methods: Firstly, the pH-responsive antimicrobial experiments including colony-forming units, scanning electron microscopy and exopoly-saccharide staining were measured. Secondly, lactic acid measurement and transverse microradiography analysis were performed to determine the preventive effect of DMAEM@RA on secondary caries. Lastly, quantitative real-time PCR was applied to investigate the antimicrobial effect of DMAEM@RA on cariogenic virulence genes. Results: DMAEM@RA significantly inhibited the growth, EPS, and acid production of Streptococcus mutans and Candida albicans dual-species biofilms under acidic environments (p < 0.05). Moreover, at pH 5 and 5.5, DMAEM@RA remarkably decreased the mineral loss and lesion depth of tooth hard tissue (p < 0.05) and down-regulated the expression of cariogenic genes, virulence-associated genes, and pH-regulated genes of dual-species biofilms (p < 0.05). Conclusions: DMAEM@RA played an antibiofilm role on Streptococcus mutans and Candida albicans dual-species biofilms, prevented the demineralization process, and attenuated cariogenic virulence in a pH-dependent manner. Full article

Numerous in vitro studies highlight the role of quorum sensing in the pathogenicity and virulence of biofilms. This narrative review discusses general principles in quorum sensing, including Gram-positive and Gram-negative models and the influence of flow, before focusing on quorum sensing and quorum quenching in cariogenic and periodontopathic biofilms. In cariology, quorum sensing centres on the role of Streptococcus mutans, and to a lesser extent Candida albicans, while Fusobacterium nucleatum and the red complex pathogens form the basis of the majority of the quorum sensing research on periodontopathic biofilms. Recent research highlights developments in quorum quenching, also known as quorum sensing inhibition, as a potential antimicrobial tool to attenuate the pathogenicity of oral biofilms by the inhibition of bacterial signalling networks. Quorum quenchers may be synthetic or derived from plant or bacterial products, or human saliva. Furthermore, biofilm inhibition by coating quorum sensing inhibitors on dental implant surfaces provides another potential application of quorum quenching technologies in dentistry. While the body of predominantly in vitro research presented here is steadily growing, the clinical value of quorum sensing inhibitors against in vivo oral polymicrobial biofilms needs to be ascertained. Full article

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. Full article

Based on the ecological plaque hypothesis, suppressing opportunistic pathogens within biofilms, rather than killing microbes indiscriminately, could be a biofilm control strategy for managing dental caries. The present study aimed to evaluate the effects of irresistin-16 (IRS-16) on competitive dual-species biofilms, which consisted of the conditional cariogenic agent Streptococcus mutans (S. mutans) and oral commensal bacteria Streptococcus sanguinis (S. sanguinis). Bacterial growth and biofilm formation were monitored using growth curve and crystal violet staining, respectively. The microbial proportion was determined using fluorescence in situ hybridization. A 2, 5-diphenyltetrazolium bromide assay was used to measure the metabolic activity of biofilms. Bacterial/extracellular polysaccharide (EPS) dyeing, together with water-insoluble EPS measurements, were used to estimate EPS synthesis. A lactic acid assay was performed to detect lactic acid generation in biofilms. The cytotoxicity of IRS-16 was evaluated in mouse fibroblast L929 cells using a live/dead cell viability assay and cell counting kit-8 assay. Our results showed that IRS-16 exhibited selective anti-biofilm activity, leading to a remarkable survival disadvantage of S. mutans within competitive dual-species biofilms. In addition, the metabolic activity, EPS synthesis, and acid generation of dual-species biofilms were significantly reduced by IRS-16. Moreover, IRS-16 showed minimal cytotoxicity against mouse fibroblast L929 cells. In conclusion, IRS-16 exhibited remarkable regulatory effects on dual-species biofilms composed of S. mutans and S. sanguinis with low cytotoxicity, suggesting that it may have potential for use in caries management through ecological biofilm control. Full article