Sucrose substitutes affect the cariogenic potential of Streptococcus mutans biofilms

Characterizations of biogenic selenium nanoparticles and their anti-biofilm potential against Streptococcus mutans ATCC 25175

INTRODUCTION

S. mutans has been identified as the primary pathogenic bacterium in biofilm-mediated dental caries. The biogenic selenium nanoparticles (SeNPs) produced by L. plantarum KNF-5 were used in this study against S. mutans ATCC 25175.

OBJECTIVES

The aims of this study were: (1) the biosynthesis of SeNPs by L. plantarum KNF-5, (2) the characterization of SeNPs, (3) the investigation of the inhibitory effect of biogenic SeNPs against S. mutans ATCC 25175, and (4) the determination of the anti-biofilm potential of SeNPS against S. mutans ATCC 25175.

METHODOLOGY

3 mL of the culture was added to 100 mL of MRS medium and incubated. After 4 h, Na2SeO3 solution (concentration 100 μg/mL) was added and incubated at 37 °C for 36 h. The color of the culture solution changed from brownish-yellow to reddish, indicating the formation of SeNPs. The characterization of SeNPs was confirmed by UV-Vis spectrophotometry, FTIR, SEM-EDS and a particle size analyzer. The antibacterial activity was determined by the disk diffusion method, the MIC by the micro-double dilution method, and the biofilm inhibitory potential by the crystal violet method and the MTT assay. The effect of SeNPs on S. mutans ATCC 25175 was determined using SEM and CLSM spectrometry techniques. The sulfate-anthrone method was used to analyze the effect of SeNPs on insoluble extracellular polysaccharides. The expression of genes in S. mutans ATCC 25175 was analyzed by real-time quantitative polymerase chain reaction (RT-qPCR).

PREPARATION OF NANOPARTICLES

SeNPs produced by probiotic bacteria are considered a safe method. In this study, L. plantarum KNF-5 (probiotic strain) was used for the production of SeNPs.

RESULTS

The biogenic SeNPs were spherical and coated with proteins and polysaccharides and had a diameter of about 270 nm. The MIC of the SeNPs against S. mutans ATCC 25175 was 3.125 mg/mL. Biofilm growth was also significantly suppressed at this concentration. The expression of genes responsible for biofilm formation (GtfB, GtfC, BrpA and GbpB,) was reduced when S. mutans ATCC 25175 was treated with SeNPs.

CONCLUSION

It was concluded that the biogenic SeNPs produced by L. plantarum KNF-5 was highly effective to inhibit the growth of S. mutans ATCC 25175.

NOVELTY STATEMENT

The application of biogenic SeNPs, a natural anti-biofilm agent against S. mutans ATCC 25175. In the future, this study will provide a new option for the prevention and treatment of dental caries.

Interplay between dental caries pathogens, periodontal pathogens, and sugar molecules: approaches for prevention and treatment

Globally, oral diseases affect nearly 3.5 billion people, accounting for 4.6% of the healthcare expenditure. Common oral diseases include dental caries and periodontal disease, associated with biofilms formed by cariogenic pathogens. Epidemiological studies associate carbohydrates with these diseases due to  the sugars metabolized by cariogenic pathogens. This review focuses on dental caries and periodontal pathogens, quorum sensing, lectin-carbohydrate interactions, and various sugar molecules. Cariogenic sugars significantly influence biofilms by enhancing pathogen adhesion, viability, and gene expressions associated with biofilm formation. Moreover, lectin-carbohydrate interactions contribute to biofilm stability. Disrupting these interactions is a potential strategy for oral disease prevention. The use of nanoparticles, such as quantum dots, provides novel insights into lectin-sugar interactions and the development of inhibitors. Additionally, nanomaterials like calcium phosphate nanoparticles neutralize acids and inhibit microbial growth. This overview emphasizes understanding the relationships between oral diseases, microbial communities, and sugars to devise preventive and therapeutic strategies against oral diseases.

Time-lapse confocal microscopy to study in vitro Streptococcus mutans surface colonization

The cariogenicity of Streptococcus mutans relates to its ability to form biofilms on dental surfaces. The aim of this work was to develop a flowcell system compatible with time-lapse confocal microscopy to compare the adhesion and accumulation of S. mutans cells on surfaces in unsupplemented media against media containing sucrose or sucralose (a non-metabolized sweetener) over a short period of time. Fluorescent S. mutans 3209/pVMCherry was suspended in unsupplemented media or media supplemented with 1% sucrose or 1% sucralose and passed through a 3D-printed flowcell system. Flowcells were imaged over 60 minutes using a confocal microscope. Image analysis was performed, including a newly developed object-movement-based method to measure biomass adhesion. Streptococcus mutans 3209/pVMCherry grown in 1% sucrose-supplemented media formed small, dense, relatively immobile clumps in the flowcell system measured by biovolume, surface area, and median object centroid movement. Sucralose-supplemented and un-supplemented media yielded large, loose, mobile aggregates. Architectural metrics and per-object movement were significantly different (P < 0.05) when comparing sucrose-supplemented media to either unsupplemented or sucralose-supplemented media. These results demonstrate the utility of a flowcell system compatible with time-lapse confocal microscopy and image analysis when studying initial biofilm formation and adhesion under different nutritional conditions.

The inhibitory effect of berberine chloride hydrate on Streptococcus mutans biofilm formation at different pH values

Streptococcus mutans (S. mutans) is one of the major cariogenic bacteria of dental caries owing to its ability to adhere to tooth surfaces and biofilm formation. Berberine chloride hydrate (BH), a quaternary ammonium salt alkaloid, has diverse pharmacological efforts against microorganisms. However, the effect of BH on S. mutans biofilm has not been reported. Considering that berberine is a quaternary ammonium salt alkaloid, which needs to adapt to a large variation in pH values and the acid resistance of S. mutans, we employed three groups including pH 5 (acidic), pH 8 (alkaline), and unprocessed group (neutral) to examine the antibiofilm activities of BH against S. mutans during different pH values. In this study, we found BH effectively suppresses S. mutans biofilm formation as well as its cariogenic virulence including acid production and EPS synthesis significantly, and the inhibitory effort was reduced under acidic condition whereas elevated under alkaline condition. In addition, we preliminarily explored the influence of pH values on the structural stability and biosafety of BHas well as the underlying mechanism of inhibition of S. mutans biofilm formation with BH. Our study showed BH could maintain a good structural stability and low toxicity to erythrocytes at different pH values. And BH could downregulate the expression of srtA, spaP, and gbpC, which play critical roles in the adhesion process, promoting bacterial colonization and biofilm formation. Furthermore, comX and ldh expression levels were downregulated in BH-treated group, which might explain its inhibitory effect on acid production.IMPORTANCEDental caries is a common chronic detrimental disease, which could cause a series of oral problem including oral pain, difficulties in eating, and so on. Recently, many natural products have been considered as fundamental sources of therapeutic drugs to prevent caries. Berberine as a plant extract showed good antibiofilm abilities against microorganism. Our study focuses on its antibiofilm abilities against S. mutans, which was defined as major cariogenic bacterium and explored the role of pH values and possible underlying mechanisms in the inhibitory effect of BH on S. mutans biofilm formation. This study demonstrated a promising prospect for BH as an adjuvant drug in the prevention and management of dental caries.

Microbiological evaluation in invisible aligner chemical cleaning methods against Candida albicans and Streptococcus mutans

INTRODUCTION

This study aimed to assess the efficacy of chemical agents in removing Candida albicans and Streptococcus mutans biofilm from invisible aligners.

METHODS

The samples were made of EX30 Invisalign trays, biofilm was cultured by standardized suspensions of C. albicans ATCC strain and S. mutans clinical strain on the sample. The treatments used were 0.5% sodium hypochlorite (NaClO) (20 minutes), 1% NaClO (10 minutes), chlorhexidine (5 minutes), peroxide (15 minutes), and orthophosphoric acid (15 seconds). The control group received phosphate-buffered saline for 10 minutes. The colony-forming units per milliliter of each microorganism were determined by serial dilutions seeded in plates with selective culture mediums for each one. Data were analyzed by the Kruskal-Wallis and Conover-Iman tests at an α of 0.05.

RESULTS

For the C. albicans biofilm group, the control group had 9.7 Log10 of microorganism growth, and all treatment groups had statistically significant biofilm reduction, in which chlorhexidine presented the highest inhibition of 3 Log10, followed by alkaline peroxide and orthophosphoric acid both with 2.6 Log10, 1% NaClO (2.5 Log10), and 0.5% NaClO (2 Log10). As for S. mutans, the control group had 8.9 Log10 of growth, and a total microorganism inhibition was reached by chlorhexidine, 1% NaClO, and orthophosphoric acid, whereas alkaline peroxide inhibited growth to 7.9 Log10 and 0.5% NaClO 5.1 Log10.

CONCLUSIONS

Within the limitations, chlorhexidine and orthophosphoric acid had greater efficacy in both biofilms. In addition, 1% NaClO and alkaline peroxide also had significant effects; therefore, their incorporation aligners disinfection protocols are valid.

Potential oral probiotic Lactobacillus pentosus MJM60383 inhibits Streptococcus mutans biofilm formation by inhibiting sucrose decomposition

Streptococcus mutans is known as a contributor to dental caries. In this work, Lactobacillus pentosus MJM60383 was selected for its strong antagonistic activity against S. mutans and was characterized by good oral probiotic properties including lysozyme tolerance, adhesive ability to oral cells, good aggregation (auto-aggregation, co-aggregation) ability, hydrogen peroxide production and inhibition of biofilm formation of S. mutans. L. pentosus MJM60383 also exhibited safety as a probiotic characterized by no hemolytic activity, no D-lactate production, no biogenic amine production, and susceptibility to antibiotics. Furthermore, the biofilm formation of S. mutans was also significantly inhibited by the supernatant of L. pentosus MJM60383. An anti-biofilm mechanism study revealed that sucrose decomposition and the production of water-insoluble exopolysaccharides by S. mutans were inhibited by the treatment with L. pentosus MJM60383 supernatant. Real-time PCR analysis indicated that the supernatant of L. pentosus MJM60383 significantly inhibited the mRNA expression of S. mutans glycosyltransferases, which synthesize glucan to construct biofilm architecture and mediate bacterial adherence. Our study demonstrated L. pentosus MJM60383 as a potential oral probiotic and revealed its anti-biofilm mechanism.

Lactobacillus cell envelope-coated nanoparticles for antibiotic delivery against cariogenic biofilm and dental caries

Background

Due to their prevalence, dental caries ranks first among all diseases endangering human health. Therefore, the prevention of caries is of great significance, as caries have become a serious public health problem worldwide. Currently, using nanoscale drug delivery systems to prevent caries has received increased attention. However, the preventive efficacy of these systems is substantially limited due to the unique physiological structure of cariogenic biofilms. Thus, novel strategies aimed at combating cariogenic biofilms to improve preventive efficiency against caries are meaningful and very necessary. Herein, inspired by cell membrane coating technology and Lactobacillus strains, we coated triclosan (TCS)-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (TCS@PLGA-NPs) with an envelope of Lactobacillus (LA/TCS@PLGA-NPs) and investigated their potential as a nanoparticle delivery system against cariogenic biofilms and dental caries.

Results

LA/TCS@PLGA-NPs were successfully prepared with favorable properties, including a coated envelope, controllable size, negative charge, sustained drug-release kinetics and so on. The LA/TCS@PLGA-NPs inherited native properties from the source cell surface, thus the LA/TCS@PLGA-NPs adhered to S. mutans, integrated into the S. mutans biofilm, and interfered with the biofilm formation of S. mutans. The nanoparticles significantly inhibited the activity, biomass and virulence gene expression of S. mutans biofilms in vitro. Additionally, LA/TCS@PLGA-NPs exhibited a long-lasting inhibitory effect on the progression of caries in vivo. The safety performance of the nanoparticles is also favorable.

Conclusions

Our findings reveal that the antibiofilm effect of LA/TCS@PLGA-NPs relies not only on the inheritance of native properties from the Lactobacillus cell surface but also on the inhibitory effect on the activity, biomass and virulence of S. mutans biofilms. Thus, these nanoparticles could be considered feasible candidates for a new class of effective drug delivery systems for the prevention of caries. Furthermore, this work provides new insights into cell membrane coating technology and presents a novel strategy to combat bacterial biofilms and associated infections.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01563-x.

Efficiency of Bacillus subtilis metabolism of sugar alcohols governs its probiotic effect against cariogenic Streptococcus mutans

Bacillus subtilis is a Gram-positive probiotic bacterium that successfully colonises plant roots due to its ability to utilise various sugars. The vast probiotic potential of B. subtilis has been recently demonstrated in numerous host organisms under different environmental conditions. We examined the probiotic potential of B. subtilis against the pathogenic bacterium Streptococcus mutans, which is involved in various oral disorders due to its robust biofilm-forming capability. B. subtilis cells attenuated biofilm formation by S. mutans during their dual growth in the presence of sugar alcohols. Transcription of genes encoding key enzymes in the metabolism of sugar alcohols by B. subtilis were highly induced. Moreover, growth-curve analysis suggested that B. subtilis is more efficient at early utilising sugar alcohols than S. mutans, as supported by the bacterial metabolic activity rates. Similarly, a comparison of secondary metabolites of mono and mixed cultures of B. subtilis and S. mutans indicated that B. subtilis is more active metabolically in the dual culture. Finally, knock-out mutations of the genes encoding key enzymes in the central metabolic pathway significantly reduced B. subtilis' ability to mitigate biofilm formation by S. mutans. We conclude that effective metabolism of sugar alcohols by B. subtilis reinforces the probiotic potential of this bacterium against pathogenic species such as S. mutans.

The Effects of Nonnutritive Sweeteners on the Cariogenic Potential of Oral Microbiome

Nonnutritive sweeteners (NNSs) are sugar substitutes widely used to reduce the negative health effects of excessive sugar consumption. Dental caries, one of the most prevalent chronic diseases globally, results from a pathogenic biofilm with microecological imbalance and frequent exposure to sugars. Some research has shown that certain NNSs possess less cariogenic potential than sucrose, indicating their putative effect on oral microbiome. To uncover the alterations of acidogenic pathogens and alkali-generating commensals, as well as the biofilm cariogenic potential under the influence of NNSs, we selected four common NNSs (acesulfame-K, aspartame, saccharin, and sucralose) and established single-, dual-, and multispecies in vitro culture model to assess their effects on Streptococcus mutans (S. mutans) and/or Streptococcus sanguinis (S. sanguinis) compared to sucrose with the same sweetness. The results showed that NNSs significantly suppressed the planktonic growth, acid production, and biofilm formation of S. mutans or S. sanguinis compared with sucrose in single-species cultures. Additionally, decreased S. mutans/S. sanguinis ratio, less EPS generation, and higher pH value were observed in dual-species and saliva-derived multispecies biofilms with supplementary NNSs. Collectively, this study demonstrates that NNSs inhibit the cariogenic potential of biofilms by maintaining microbial equilibrium, thus having a promising prospect as anticaries agents.

Streptococcus mutans Membrane Vesicles Harboring Glucosyltransferases Augment Candida albicans Biofilm Development

Candida albicans, as the most common fungus in the oral cavity, is often detected in early childhood caries. Streptococcus mutans is the major etiological agent of dental caries, but the role of S. mutans on C. albicans growth and biofilm development remains to be elucidated. Membrane vesicles (MVs) are a cell-secreted subcellular fraction that play an important role in intercellular communication and disease progression. In the present study, we investigated whether MVs from S. mutans augment C. albicans growth and biofilm development. The results indicated that S. mutans MVs augmented C. albicans biofilm development but had no significant effect on C. albicans growth under planktonic conditions. Subsequently, we labeled S. mutans MVs with PKH26 and used confocal laser scanning microscopy (CLSM) to track S. mutans MVs, which were observed to be located in the C. albicans biofilm extracellular matrix. Monosaccharide tests showed that S. mutans MVs contribute to sucrose metabolism in C. albicans. Polysaccharides were significantly enriched in the S. mutans MV-treated group. MVs from ΔgtfBC mutant strains were compared with those from the wild-type S. mutans. The results revealed that MVs from the ΔgtfBC mutant had no effect on C. albicans biofilm formation and exopolysaccharide production. In addition, C. albicans biofilm transcriptional regulators (Ndt80, Als1, Mnn9, Van1, Pmr1, Gca1, and Big1) expression were upregulated in S. mutans MV-treated group. In summary, the results of the present study showed that S. mutans MVs harboring glucosyltransferases involved in exopolysaccharide production augment C. albicans biofilm development, revealing a key role for S. mutans MVs in cross-kingdom interactions between S. mutans and C. albicans.

Effect of Rubusoside, a Natural Sucrose Substitute, on Streptococcus mutans Biofilm Cariogenic Potential and Virulence Gene Expression In Vitro

Dental caries is a biofilm-mediated disease in which Streptococcus mutans is the main pathogenic microorganism, and its incidence is closely related to sucrose. Rubusoside is a natural nonnutritive sweetener isolated from Rubus suavissimus S. Lee. This study was designed to determine the effect of this sucrose substitute on the cariogenic properties and virulence gene expression of S. mutans biofilms. S. mutans was exposed to brain heart infusion (BHI) medium (as a control), 1% sucrose-supplemented medium, 1% rubusoside-supplemented medium, and 1% xylitol-supplemented medium. The growth curve of the biofilm was monitored by crystal violet staining, and the pH was measured every 24 h. After 5 days, the biofilms formed on the glass coverslips were recovered to determine the biomass (dry weight and total amount of soluble proteins), numbers of CFU, and amounts of intra- and extracellular polysaccharides. Biofilm structural imaging was performed using a scanning electron microscope (SEM). Virulence gene expression (gtfB, gtfC, gtfD, ftf, spaP, gbpB, ldh, atpF, vicR, and comD) was determined by reverse transcription-quantitative PCR. Growth in rubusoside resulted in lower levels of acid production than observed during growth in sucrose, xylitol, and the control, while it also reduced the level of biofilm accumulation and bacterial viability and even reduced the level of production of extracellular polysaccharides. By SEM, the levels of biofilm formation and extracellular matrix during growth in rubusoside were lower than these levels during growth in sucrose and xylitol. From the perspective of virulence genes, growth in rubusoside and xylitol significantly inhibited the expression of virulence genes compared with their levels of expression after growth in sucrose. Among these genes, gtfB, gtfC, gbpB, ldh, and comD downregulation was found with growth in rubusoside compared with their expression with growth in xylitol. Therefore, rubusoside appears to be less potentially cariogenic than sucrose and xylitol and may become an effective sucrose substitute for caries prevention. Further studies are needed to deepen these findings.IMPORTANCE Dental caries is a major public health challenge and places heavy biological, social, and financial burdens on individuals and health care systems. To palliate the deleterious effect of sucrose on the virulence factors of S. mutans, massive commercial efforts have been oriented toward developing products that may act as sucrose substitutes. Rubusoside, a natural sucrose substitute, is a plant extract with a high level of sweetness. Although some studies have shown that rubusoside does not produce acids or inhibit the growth of S. mutans, little attention has been paid to its effect on dental biofilm and the underlying mechanisms. Our study focuses on the effect of rubusoside on the formation and structure of biofilms and the expression of virulence genes. The results confirm that rubusoside can inhibit accumulation, bacterial viability, polysaccharide production by the biofilm, and related gene expression. These results provide further insight into the cariogenicity of S. mutans biofilms and demonstrate a new perspective for studying the impact of sucrose substitutes on caries.

Antibacterial and Antibiofilm Activity of Temporin-GHc and Temporin-GHd Against Cariogenic Bacteria, Streptococcus mutans

Temporin-GHc (GHc) and temporin-GHd (GHd) produced by the frog Hylarana guentheri had shown broad-spectrum antibacterial activities against bacteria and fungi. In this study, we investigated whether they exert antibacterial and antibiofilm activities against cariogenic bacteria, Streptococcus mutans. GHc and GHd adopt the random coil conformation in aqueous solution and convert to α-helix in membrane mimetic environments by using circular dichroism spectroscope. They are positively charged by histidine, with the polar and nonpolar amino acids on opposing faces along the helix. The amphipathicity enabled the peptides to target at bacterial membrane, leading to an increase in membrane permeation and disruption of S. mutans, which allowed the peptides to bind with genomic DNA. GHc and GHd completely impeded the initial attachment of biofilm formation and disrupted preformed S. mutans biofilms. The expression of exopolysaccharide (EPS) biosynthesis genes which synthesize glucosyltransferases in S. mutans was downregulated by exposing to GHc or GHd, contributing to the decrease of soluble and insoluble EPS. GHc and GHd exhibited selectivity toward S. mutans in the presence of human erythrocytes, and no cytotoxicity toward human oral epithelial cells was observed at a concentration of 200 μM. These results laid the foundation for the development of GHc and GHd as potential anti-caries agents.

Insight into the Effect of Small RNA srn225147 on Mutacin IV in Streptococcus mutans

Streptococcus mutans (S. mutans) is a serious microbe causing dental caries. Mutacin IV is an effective bacteriocin produced by S. mutans to antagonize numerous non-mutans streptococcal species. However, the posttranscriptional regulation of mutacin IV remains unclear. This study aimed to analyze the effect of small RNA srn225147 on mutacin IV. The functional prediction suggested that srn225147 is involved in the production of mutacin IV, an important secondary metabolite. According to RNAhybrid and RNAPredator prediction, the mutacin IV formation-associated gene comD is a target of srn225147. We further analyzed the roles of srn225147 and comD in 20 S. mutans clinical strains with high production of mutacin IV (High-IV group) and lacking mutacin IV (None-IV group). Levels of comD expression were significantly higher in the High-IV group, whereas the Non-IV group showed relatively higher expression of srn225147, with a negative correlation observed between srn225147 and comD. Moreover, compared to the mimic negative control (NC) group, comD expression was decreased at 400-fold srn225147 overexpression but increased at approximately 1400-fold overexpression. Although the production of mutacin IV in the 1400-fold change srn225147 mimic group was larger than that in the 400-fold change mimic group, there was no significant difference in the production of mutacin IV between the srn225147 mimic group and mimic NC group. These results indicate that srn225147 has a two-way regulation effect on the expression of comD but that its regulation in the production of mutacin IV is weak.

Carious status and supragingival plaque microbiota in hemodialysis patients

Objective

The aim of this study was to evaluate the carious status and the microbial profiles of supragingival plaque in patients with chronic kidney disease undergoing hemodialysis.

Methods

This study included 30 patients with chronic kidney disease undergoing hemodialysis as well as 30 control subjects. Dental examination was performed and the decayed-missing-filled-teeth was recorded. Supragingival plaque was taken and analyzed using 16S rRNA gene amplicon by Illumina MiSeq sequencing to detect microbial composition and community diversity and structure.

Results

The level of decayed-missing-filled-teeth was higher in the hemodialysis group than that in the control group. Microbial analysis showed a decrease in α diversity and a increase in relative abundance and prevalence of many acidogenic and aciduric caries related species in the supragingival plaque samples of the hemodialysis patients, including Streptococcus mutans, Lactobacillus salivarius, Lactobacillus fermentum, Lactobacillus vaginalis, Scardovia wiggsiae F0424, and Actinomyces naeslundii.

Conclusion

Our results suggested that the hemodialysis patients were more susceptible to caries. More attentions for caries prevention and treatment should be paid to improve their life quality, and even to reduce their cardiovascular events and survival.

Analysis of sucrose-induced small RNAs in Streptococcus mutans in the presence of different sucrose concentrations

Streptococcus mutans (S. mutans) is the major pathogen contributing to dental caries. Sucrose is an important carbohydrate source for S. mutans and is crucial for dental caries. Small RNAs (sRNAs) are key post-transcriptional regulators of stress adaptation and virulence in bacteria. Here, for the first time, we created three replicate RNA libraries exposed to either 1 or 5% sucrose. The expression levels of sRNAs and target genes (gtfB, gtfC, and spaP) related to virulence were assessed. In addition, some phenotypic traits were evaluated. We obtained 2125 sRNA candidates with at least 100 average reads in 1% sucrose or 5% sucrose. Of these candidates, 2 were upregulated and 20 were downregulated in 1% sucrose. Six of these 22 differentially expressed sRNAs were validated by qRT-PCR. The expression level of target gene gtfB was higher in 1% sucrose. The adherence ratio of S. mutans was higher in 1% sucrose than in 5% sucrose. The synthesis of water-insoluble glucans (WIGs) was significantly higher in 5% sucrose than in 1% sucrose. These data suggest that a series of sRNAs can be induced in response to sucrose, and that some sRNAs might be involved in the regulation of phenotypes, providing new insight into the prevention of caries.

Streptococcus gordonii LuxS/autoinducer-2 quorum-sensing system modulates the dual-species biofilm formation with Streptococcus mutans

Dental plaques are mixed-species biofilms that are related to the development of dental caries. Streptococcus mutans (S. mutans) is an important cariogenic bacterium that forms mixed-species biofilms with Streptococcus gordonii (S. gordonii), an early colonizer of the tooth surface. The LuxS/autoinducer-2(AI-2) quorum sensing system is involved in the regulation of mixed-species biofilms, and AI-2 is proposed as a universal signal for the interaction between bacterial species. In this work, a S. gordonii luxS deficient strain was constructed to investigate the effect of the S. gordonii luxS gene on dual-species biofilm formed by S. mutans and S. gordonii. In addition, AI-2 was synthesized in vitro by incubating recombinant LuxS and Pfs enzymes of S. gordonii together. The effect of AI-2 on S. mutans single-species biofilm formation and cariogenic virulence gene expression were also assessed. The results showed that luxS disruption in S. gordonii altered dual-species biofilm formation, architecture, and composition, as well as the susceptibility to chlorhexidine. And the in vitro synthesized AI-2 had a concentration-dependent effect on S. mutans biofilm formation and virulence gene expression. These findings indicate that LuxS/AI-2 quorum-sensing system of S. gordonii plays a role in regulating the dual-species biofilm formation with S. mutans.

Optical analysis of enamel and dentin caries in relation to mineral density using swept-source optical coherence tomography

The aim of this study was to evaluate the signal intensity and signal attenuation of swept source optical coherence tomography (SS-OCT) for dental caries in relation to the variation of mineral density. SS-OCT observation was performed on the enamel and dentin artificial demineralization and on natural caries. The artificial caries model on enamel and dentin surfaces was created using Streptococcus mutans biofilms incubated in an oral biofilm reactor. The lesions were centrally cross sectioned and SS-OCT scans were obtained in two directions to construct a three-dimensional data set, from the lesion surface (sagittal scan) and parallel to the lesion surface (horizontal scan). The integrated signal up to [Formula: see text] in depth (IS200) and the attenuation coefficient ([Formula: see text]) of the enamel and dentin lesions were calculated from the SS-OCT signal in horizontal scans at five locations of lesion depth. The values were compared with the mineral density obtained from transverse microradiography. Both enamel and dentin demineralization showed significantly higher IS200 and [Formula: see text] than the sound tooth substrate from the sagittal scan. Enamel demineralization showed significantly higher IS200 than sound enamel, even with low levels of demineralization. In demineralized dentin, the [Formula: see text] from the horizontal scan consistently trended downward compared to the sound dentin.

Enhancement of immunogenic response and protection in model rats by CSTM nanoparticles anticaries DNA vaccine

AIM

To construct anticaries DNA vaccine and evaluate its ability to elicit mucosal and systemic immune responses in rats.

MATERIALS & METHODS

wapA fragment was cloned into pVAX1 plasmid to generate pVAX1-wapA. The pVAX1-wapA/trimethyl chitosan nanoparticles were prepared by complex coacervation method.

RESULTS

Significantly higher specific IgG antibody titers were observed in rats immunized with nanoparticles compared with rats immunized with naked pVAX1-wapA. Anti-WapA IgA and IgG antibody levels after intranasal immunization were significantly higher than those following intramuscular delivery of nanoparticles or naked pVAX1-wapA. Furthermore, fewer enamel, slight dentin and dentin moderate lesions were observed in rats immunized with nanoparticles.

CONCLUSION

The results implicate WapA as an excellent candidate for anticaries vaccine development and nanoparticles as an effective delivery system.

Intraspecies Variability Affects Heterotypic Biofilms of Porphyromonas gingivalis and Prevotella intermedia: Evidences of Strain-Dependence Biofilm Modulation by Physical Contact and by Released Soluble Factors

It is well known that strain and virulence diversity exist within the population structure of Porphyromonas gingivalis. In the present study we investigate intra- and inter-species variability in biofilm formation of Porphyromonas gingivalis and partners Prevotella intermedia and Prevotella nigrescens. All strains tested showed similar hydrophobicity, except for P. gingivalis W83 which has roughly half of the hydrophobicity of P. gingivalis ATCC33277. An intraspecies variability in coaggregation of P. gingivalis with P. intermedia was also found. The association P. gingivalis W83/P. intermedia 17 produced the thickest biofilm and strain 17 was prevalent. In a two-compartment system P. gingivalis W83 stimulates an increase in biomass of strain 17 and the latter did not stimulate the growth of P. gingivalis W83. In addition, P. gingivalis W83 also stimulates the growth of P. intermedia ATCC25611 although strain W83 was prevalent in the association with P. intermedia ATCC25611. P. gingivalis ATCC33277 was prevalent in both associations with P. intermedia and both strains of P. intermedia stimulate the growth of P. gingivalis ATCC33277. FISH images also showed variability in biofilm structure. Thus, the outcome of the association P. gingivalis/P. intermedia seems to be strain-dependent, and both soluble factors and physical contact are relevant. The association P. gingivalis-P. nigrescens ATCC33563 produced larger biomass than each monotypic biofilm, and P. gingivalis was favored in consortia, while no differences were found in the two-compartment system. Therefore, in consortia P. gingivalis-P. nigrescens physical contact seems to favor P. gingivalis growth. The intraspecies variability found in our study suggests strain-dependence in ability of microorganisms to recognize molecules in other bacteria which may further elucidate the dysbiosis event during periodontitis development giving additional explanation for periodontal bacteria, such as P. gingivalis and P. intermedia, among others, to persist and establish chronic infections in the host.

Effect of sucrose concentration on sucrose-dependent adhesion and glucosyltransferase expression of S. mutans in children with severe early-childhood caries (S-ECC)

Sucrose, extracellular polysaccharide, and glucosyltransferases (GTFs) are key factors in sucrose-dependent adhesion and play important roles in the process of severe early-childhood caries (S-ECC). However, whether sucrose concentration regulates gtf expression, extracellular polysaccharide synthesis, and sucrose-dependent adhesion is related to the different genotypes of S. mutans isolated from ECC in children and still needs to be investigated. In this study, 52 strains of S. mutans were isolated from children with S-ECC and caries-free (CF) children. Water-insoluble glucan (WIG) synthesis was detected by the anthrone method, adhesion capacity by the turbidimetric method, and expression of gtf by RT-PCR in an in vitro model containing 1%–20% sucrose. The genotypes of S. mutans were analyzed by AP-PCR. The results showed that WIG synthesis, adhesion capacity, and gtf expression increased significantly when the sucrose concentration was from 1% to 10%. WIG synthesis and gtfB as well as gtfC expression of the 1% and 5% groups were significantly lower than those of the 10% and 20% groups (p < 0.05). There were no significant differences between the 10% and 20% groups. The fingerprints of S. mutans detected from individuals in the S-ECC group exhibited a significant difference in diversity compared with those from CF individuals (p < 0.05). Further, the expression of gtfB and gtfC in the S-ECC group was significantly different among the 1- to 5-genotype groups (p < 0.05). It can be concluded that sucrose-dependent adhesion might be related to the diversity of genotypes of S. mutans, and the 10% sucrose level can be seen as a “turning point” and essential factor for the prevention of S-ECC.

Antibacterial and Antibiofilm Activities of Makaluvamine Analogs

Streptococcus mutans is a key etiological agent in the formation of dental caries. The major virulence factor is its ability to form biofilms. Inhibition of S. mutans biofilms offers therapeutic prospects for the treatment and the prevention of dental caries. In this study, 14 analogs of makaluvamine, a marine alkaloid, were evaluated for their antibacterial activity against S. mutans and for their ability to inhibit S. mutans biofilm formation. All analogs contained the tricyclic pyrroloiminoquinone core of makaluvamines. The structural variations of the analogs are on the amino substituents at the 7-position of the ring and the inclusion of a tosyl group on the pyrrole ring N of the makaluvamine core. The makaluvamine analogs displayed biofilm inhibition with IC50 values ranging from 0.4 μM to 88 μM. Further, the observed bactericidal activity of the majority of the analogs was found to be consistent with the anti-biofilm activity, leading to the conclusion that the anti-biofilm activity of these analogs stems from their ability to kill S. mutans. However, three of the most potent N-tosyl analogs showed biofilm IC50 values at least an order of magnitude lower than that of bactericidal activity, indicating that the biofilm activity of these analogs is more selective and perhaps independent of bactericidal activity.