Effect of arginine on the growth and biofilm formation of oral bacteria

BackgroundAlkali production via arginine deiminase system (ADS) of oral bacteria plays a significant role in oral ecology, pH homeostasis and inhibition of dental caries. ADS activity in dental plaque varies greatly between individuals, which may profoundly affect their susceptibility to caries.ObjectiveTo investigate the effect of arginine on the growth and biofilm formation of oral bacteria.Methods and resultsPolymicrobial dental biofilms derived from saliva were formed in a high-throughput active attachment biofilm model and l-arginine (Arg) was shown to reduce the colony forming units (CFU) counts of such biofilms grown for various periods or biofilms derived from saliva of subjects with different caries status. Arg hardly disturbed bacterial growth of Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinis and Streptococcus gordonii in BHI medium, but only inhibited biofilm formation of S. mutans. Scanning electron microscope (SEM) showed S. mutans biofilms harboured fewer cells grown with Arg than that without Arg, even in the initial 2 h and 8 h phase. Confocal laser scanning microscope (CLSM) images of poly-microbial dental and S. mutans biofilms revealed the biofilms grown with Arg had lower exopolysaccharide (EPS)/bacteria ratios than those without Arg (P = 0.004, 0.002, respectively). Arg could significantly reduce the production of water-insoluble EPS in S. mutans biofilms (P < 0.001); however, quantitative real-time PCR (qRT-PCR) did not show significantly influence in gene expression of gtfB, gtfC or gtfD (P = 0.32, 0.06, 0.44 respectively).ConclusionsArg could reduce the biomass of poly-microbial dental biofilms and S. mutans biofilms, which may be due to the impact of Arg on water-insoluble EPS. Considering the contribution to pH homeostasis in dental biofilms, Arg may serve as an important agent keeping oral biofilms healthy thus prevent dental caries.     

Comparative effect of a stannous fluoride toothpaste and a sodium fluoride toothpaste on a multispecies biofilm

ObjectivesThis paper aimed to compare the mode of action of a stannous fluoride-containing toothpaste with a conventional sodium fluoride-containing toothpaste on anti-biofilm properties.MethodsA three-species biofilm model that consists of Streptococcus mutans, Streptococcus sanguinis and Porphyromonas gingivalis was established to compare the anti-biofilm properties of a stannous fluoride-containing toothpaste (CPH), a conventional sodium fluoride-containing toothpaste (CCP) and a negative control (PBS). The 48 h biofilms were subjected to two-minute episodes of treatment with test agents twice a day for 5 consecutive days. Crystal violet staining and XTT assays were used to evaluate the biomass and viability of the treated biofilm. Live/dead staining and bacteria/extracellular polysaccharides (EPS) double-staining were used to visualize the biofilm structure and to quantify microbial/extracellular components of the treated biofilms. Species-specific fluorescent in situ hybridization and quantitative polymerase chain reaction (qPCR) were used to analyze microbial composition of the biofilms after treatment.ResultsThe biomass and viability of the biofilms were significantly reduced after CPH toothpaste treatment. The inhibitory effect was further confirmed by the live/dead staining. The EPS amounts of the three-species biofilm were significantly reduced by CCP and CPH treatments, and CPH toothpaste demonstrated significant inhibition on EPS production. More importantly, CPH toothpaste significantly suppressed S. mutans and P. gingvalis, and enriched S. sanguinis in the three-species biofilm. In all experiments CPH had a significantly greater effect than CCP (p < 0.05) and CCP had a greater effect than PBS (p < 0.05).ConclusionsStannous fluoride-containing toothpaste not only showed better inhibitory effect against oral microbial biofilm, but was also able to modulate microbial composition within multi-species biofilm compared with conventional sodium fluoride-containing toothpaste.     

Inhibitory effects of tea catechin epigallocatechin-3-gallate against biofilms formed from Streptococcus mutans and a probiotic lactobacillus strain

ObjectiveEffects of tea catechin epigallocatechin-3-gallate (EGCG) against biofilm formation by Streptococcus mutans and probiotic Lactobacillus casei in Yakult^® (LcY) were examined.DesignBiofilms were formed by S. mutans alone (Sm) and co-culture of S. mutans and LcY (Sm + LcY) in the absence or presence of EGCG. The biomass of biofilms, which were sonicated or not, was measured by the crystal violet assay. Biofilm morphology was observed by scanning electron microscopy. Bacterial viability and extracellular polysaccharides were determined by SYTO9/propidium iodide and dextran-conjugated fluorescein staining, respectively, and confocal microscopy. Gene expression of glucosyltransferase was determined by quantitative polymerase chain reaction.ResultsWhile 250 μg/ml EGCG significantly decreased the biomass and acid production of Sm biofilms, 500 μg/ml EGCG was required to inhibit Sm + LcY biofilm formation and acid production. EGCG decreased the amount of live bacteria present in both Sm and Sm + LcY biofilms. The level of dead bacteria in Sm + LcY biofilms was higher than in Sm biofilms when formed in the presence of 250 μg/ml EGCG. EGCG decreased levels of extracellular polysaccharides in Sm and Sm + LcY biofilms. The extent of biofilm removal by sonication was not different between Sm and Sm+LcY biofilms formed in the absence or presence of 62.5 or 125 μg/ml EGCG. The level of Sm gtfB and gtfD expression in Sm + LcY biofilms was higher than those in the Sm biofilms when formed in the presence of EGCG at 250 μg/ml.ConclusionThe results indicated that LcY might interfere the inhibitory effects of EGCG against biofilm formation by S. mutans.     

Influence of Streptococcus mutans on Enterococcus faecalis Biofilm Formation

IntroductionAn important virulence factor of Enterococcus faecalis is its ability to form biofilms. Most studies on biofilm formation have been carried out by using E. faecalis monocultures. Given the polymicrobial nature of root canal infections, it is important to understand biofilm formation of E. faecalis in the presence of other microorganisms.MethodsEight clinical strains of E. faecalis were tested for biofilm formation on hydroxyapatite disks in the presence and absence of a Streptococcus mutans biofilm.ResultsSignificantly more E. faecalis viable cells were found in biofilms in the presence of S. mutans. This phenomenon was, however, strain-dependent. Of the 8 strains tested, biofilm formation of strains AA-OR34, ER5/1, and V583 was not influenced by S. mutans biofilms.ConclusionsThe results from this study, especially the strain difference, underline the importance of studying biofilm formation in a more realistic multispecies setting.     

Effects of sub-minimum inhibitory concentrations of lemon essential oil on the acid tolerance and biofilm formation of Streptococcus mutans

ObjectivesLemon essential oil (LEO) is a kind of secondary metabolite from lemon peels and has been found to inhibit cariogenic bacteria for decades. However, its effects on main cariogenic virulence factors are rarely reported. The present study aimed to investigate the effects of sub-minimum inhibitory concentrations (sub-MICs) of LEO on the acid tolerance and biofilm formation of Streptococcus mutans (S. mutans) and preliminarily reveal the possible underlying mechanisms.DesignsEffects of LEO on the acid tolerance and biofilm formation of S. mutans were investigated by the broth dilution method and crystal violet staining method respectively. The expression of luxS, srtA and spaP gene was also determined to explore the underlying mechanism. In addition, Tea polyphenols (TP), a major natural inhibitor of cariogenic virulence factors, and limonene (LIM), the major component of LEO, were selected as comparisons to evaluate the effects of LEO.ResultsSub-MICs of LEO, LIM and TP exhibited a dose-dependent inhibition of growth of S. mutans at pH ranging from 4.0 to 7.0. The formation of S. mutans biofilm was remarkably inhibited and the inhibitory rates of LEO, LIM and TP were 97.87%, 94.88% and 96.01% respectively at 1/2 MIC. Similarly, a down-regulation was observed in the expression of luxS, srtA and spaP gene at sub-MIC levels.ConclusionsEffects of LEO were similar or slightly stronger than LIM and TP, suggesting that LEO might represent a novel, natural anticarious agent that inhibited the specific genes associated with bacterial acid tolerance and biofilm formation without necessarily affecting the growth of oral bacteria.     

Inhibitory effects of β-caryophyllene on Streptococcus mutans biofilm

ObjectiveThe biofilm of Streptococcus mutans is associated with induction of dental caries. Also, they produce glucan as an extracellular polysaccharide through glucosyltransferases and help the formation of cariogenic biofilm. β-caryophyllene has been used for therapeutic agent in traditional medicine and has antimicrobial activity. The purpose of this study was to investigate the effect of β-caryophyllene on S. mutans biofilm and the expression of biofilm-related factor.DesignThe susceptibility assay of S. mutans for β-caryophyllene was performed to investigate inhibitory concentration for S. mutans growth. To evaluated the effect of β-caryophyllene on S. mutans biofilm, β-caryophyllene was treated on S. mutans in the various concentrations before or after the biofilm formation. Live S. mutans in the biofilm was counted by inoculating on Mitis-salivarius agar plate, and S. mutans biofilm was analyzed by confocal laser scanning microscope after staining bacterial live/dead staining kit. Finally, the expression of glucosyltransferases of S. mutans was investigated by real-time RT-PCR after treating with β-caryophyllene at the non-killing concentration of S. mutans.ResultsThe growth of S. mutans was inhibited by β-caryophyllene in above concentration of 0.078%, S. mutans biofilm was inhibited by β-caryophyllene in above 0.32%. Also, 2.5% of β-caryophyllene showed anti-biofilm activity for S. mutans biofilm. β-caryophyllene reduced the expression of gtf genes at a non-killing concentration for S. mutans. On the basis on these results, β-caryophyllene may have anti-biofilm activity and the inhibitory effect on biofilm related factor.Conclusionsβ-caryophyllene may inhibit cariogenic biofilm and may be a candidate agent for prevention of dental caries.     

Inhibitory effects of fruit berry extracts on Streptococcus mutans biofilms

Dark‐colored fruit berries are a rich source of polyphenols that could provide innovative bioactive molecules as natural weapons against dental caries. High‐quality extracts of cranberry, blueberry, and strawberry, and a combination of the three berry extracts (Orophenol), were used to treat 24‐h‐old Streptococcus mutans biofilms. The grown biofilms were treated with the berry extracts at concentrations ranging from 62.5 to 500 μg ml^?1. Treated biofilms were assessed for metabolic activity, acidogenicity, biovolumes, structural organization, and bacterial viability. The biofilms treated with the cranberry and Orophenol extracts exhibited the most significant reductions in metabolic activity, acid production, and bacterial/exopolysaccharide (EPS) biovolumes, while their structural architecture appeared less compact than the control‐treated biofilms. The blueberry extract produced significant reductions in metabolic activity and acidogenicity only at the highest concentration tested, without significantly affecting bacterial/EPS biovolumes or biofilm architecture. Strawberry extracts had no significant effects on S. mutans biofilms. None of the berry extracts were bactericidal for S. mutans. The results indicate that cranberry extract was the most effective extract in disrupting S. mutans virulence properties without significantly affecting bacterial viability. This suggests a potential ecological role for cranberry phenols as non‐bactericidal agents capable of modulating pathogenicity of cariogenic biofilms.     

Curcumin reduces Streptococcus mutans biofilm formation by inhibiting sortase A activity

BackgroundSortase A is an enzyme responsible for the covalent attachment of Pac proteins to the cell wall in Streptococcus mutans. It has been shown to play a role in modulating the surface properties and the biofilm formation and influence the cariogenicity of S. mutans. Curcumin, an active ingredient of turmeric, was reported to be an inhibitor for Staphylococcus aureus sortase A. The aim of this study was to investigate the inhibitory ability of curcumin against S. mutans sortase A and the effect of curcumin for biofilm formation.MethodsThe antimicrobial activity of the curcumin to the S. mutans and inhibitory ability of the curcumin against the purified sortase A in vitro were detected. Western-blot and real-time PCR were used to analysis the sortase A mediated Pac protein changes when the S. mutans was cultured with curcumin. The curcumin on the S. mutans biofilm formation was determined by biofilm formation analysis.ResultsCurcumin can inhibit purified S. mutans sortase A with a half-maximal inhibitory concentration (IC₅₀) of (10.2 ± 0.7) μmol/l, which is lower than minimum inhibitory concentration (MIC) of 175 μmol/l. Curcumin (15 μmol/l) was found to release the Pac protein to the supernatant and reduce S. mutans biofilm formation.ConclusionsThese results indicated that curcumin is an S. mutans sortase A inhibitor and has promising anti-caries characteristics through an anti-adhesion-mediated mechanism.     

Optimization of a real-time high-throughput assay for assessment of Streptococcus mutans metabolism and screening of antibacterial dental adhesives

ObjectiveThe present work shows the optimization of a high-throughput bioluminescence assay to assess the metabolism of intact Streptococcus mutans biofilms and its utility as a screening method for nanofilled antibacterial dental materials.MethodsThe assay was optimized by monitoring changes in bioluminescence mediated by variation of the experimental parameters investigated (growth media and sucrose concentration, inoculum:D-Luciferin ratio, dilution factor, inoculum volume, luminescence wavelength, replicate and luciferase metabolic activity). Confocal microscopy was then used to demonstrate the impact of biofilm growth conditions on the 3-D distribution of extracellular polymeric substance (EPS) within Streptococcus mutans biofilms and its implications as confounding factors in high-throughput studies (HTS).ResultsRelative Luminescence Unit (RLU) values from the HTS optimization were analyzed by multivariate ANOVA (α = 0.05) and coefficients of variation, whereas data from 3-D structural parameters and RLU values of biofilms grown on experimental antibacterial dental adhesive resins were analyzed using General Linear Models and Student–Newman–Keuls post hoc tests (α = 0.05). Confocal microscopy demonstrated that biofilm growth conditions significantly influenced the quantity and distribution of EPS within the 3-D structures of the biofilms. An optimized HTS bioluminescence assay was developed and its applicability as a screening method in dentistry was demonstrated using nanofilled experimental antibacterial dental adhesive resins.SignificanceThe present study is anticipated to positively impact the direction of future biofilm research in dentistry, because it offers fundamental information for the design of metabolic-based assays, increases the current levels of standardization and reproducibility while offering a tool to decrease intra-study variability.     

Incorporation of Apigenin and tt-Farnesol into dental composites to modulate the Streptococcus mutans virulence

ObjectivesThe aim of this in vitro study was to incorporate two anti-caries agents, Apigenin and tt-Farnesol, to resin composite and resin cement to reduce the virulence of Streptococcus mutans around dental restorations.MethodsApigenin (Api, 5 mM) and tt-Farnesol (Far, 5 mM) were added alone, together, and combined with fluoride (F). Biofilm of S. mutans was grown on composite discs, and the dry-weight, bacterial viability, and the polysaccharides (alkali-soluble, intracellular and water-soluble) were quantified. CLSM images of the S. mutans biofilm were obtained after three years of water-storage. The effect of the additions on the physicochemical properties and the composite colorimetric parameters were also analyzed.ResultsThe additions did not affect bacterial viability. Api alone and combined with Far or combined with Far and F decreased the bacterial dry-weight, alkali-soluble and intracellular polysaccharides. After three years, the composites containing the additions presented a greater EPS matrix on the top of biofilm. Statistical difference was obtained for the degree of conversion; however, the maximum polymerization rate and curing kinetics were unaffected by the additions. No difference was observed for the water-soluble polysaccharides, flexural strength, and elastic modulus. Api increased the yellowness of the composites.SignificanceApi, alone and combined, reduced the expression of virulence of S. mutans without jeopardizing the physicochemical properties of the composites.     

Effect of sodium fluoride on the virulence factors and composition of Streptococcus mutans biofilms

Objective

This study aimed to evaluate the influence of NaF (2, 10, 50 and 125 ppm F⁻) on the virulence factors and composition of Streptococcus mutans biofilms.

Methods

S. mutans UA159 biofilms were formed on saliva-coated hydroxyapatite discs. To assess the influence of NaF on the virulence factors of S. mutans biofilm cells, glycolytic pH drop, proton-permeability and F-ATPase activity assay were performed using 74 h old S. mutans biofilms. Glucosyltransferase (GTF) activity assay in suspension was also performed. To examine the influence of NaF on S. mutans biofilm composition, the biofilms were treated twice daily (5 min exposure/treatment) a total of five times during biofilm formation. After a total of 5 treatments, the biomass, colony forming unit (CFU) and polysaccharide composition of the treated 74 h old S. mutans biofilms were analysed by microbiological and biochemical methods, and scanning electron microscopy.

Results

NaF showed inhibitory effects on the acid production and acid tolerance of S. mutans biofilm cells at 10, 50 and 125 ppm F⁻, compared to the vehicle control (P < 0.05) and the treatments at these concentrations also affected the biomass, water-insoluble extracellular polysaccharides and intracellular iodophilic polysaccharides of the biofilms, compared to the vehicle control (P < 0.05).

Conclusions

These results indicate that NaF (10, 50 and 125 ppm F⁻) has inhibitory effects on the virulence factors and composition of S. mutans biofilms, suggesting the potential use of these concentrations as an effective measure for controlling dental biofilms.     

Effects of S. mutans gene-modification and antibacterial monomer dimethylaminohexadecyl methacrylate on biofilm growth and acid production

ObjectivesAntibacterial quaternary ammonium monomers (QAMs) are used in resins. The rnc gene in Streptococcus mutans (S. mutans) plays a key role in resisting antibiotics. The objectives of this study were to investigate for the first time: (1) the effects of rnc deletion on S. mutans biofilms and acid production; (2) the combined effects of rnc deletion with dimethylaminohexadecyl methacrylate (DMAHDM) on biofilm-inhibition efficacy.MethodsParent S. mutans strain UA159 (ATCC 700610) and the rnc-deleted S. mutans were used. Bacterial growth, minimum inhibitory concentration (MIC), and minimal bactericidal concentration (MBC) were measured to analyze the bacterial susceptibility of the parent and rnc-deleted S. mutans against DMAHDM, with the gold-standard chlorhexidine (CHX) as control. Biofilm biomass, polysaccharide and lactic acid production were measured.ResultsThe drug-susceptibility of the rnc-deleted S. mutans to DMAHDM or CHX was 2-fold higher than parent S. mutans. The drug-susceptibility did not increase after 10 passages (p < 0.05). Deleting the rnc gene increased the biofilm susceptibility to DMAHDM or CHX by 2-fold. The rnc-deletion in S. mutans reduced biofilm biomass, polysaccharide and lactic acid production, even at no drugs. DMAHDM was nearly 40 % more potent than the gold-standard CHX. The combination of rnc deletion + DMAHDM treatment achieved the greatest reduction in biofilm biomass, polysaccharide synthesis, and lactic acid production.SignificanceGene modification by deleting the rnc in S. mutans reduced the biofilm growth and acid production, and the rnc deletion + DMAHDM method showed the greatest biofilm-inhibition efficacy, for the first time. The dual strategy of antibacterial monomer + bacterial gene modification shows great potential to control biofilms and inhibit caries.     

Evaluation of Streptococcus mutans biofilms formed on fluoride releasing and non fluoride releasing resin composites

Objectives

The aim of this study was to evaluate the acid production, acid tolerance and composition of Streptococcus mutans biofilms formed on fluoride releasing and non fluoride releasing resin composites.

Methods

S. mutans biofilms were formed on saliva-coated discs prepared from fluoride releasing (Unifil Flow and F2000) or non fluoride releasing materials (Filtek Z350, GRADIA DIRECT and hydroxyapatite). To assess the level of acid production and acid tolerance, glycolytic pH drop and proton permeability assays were performed using 94 h old S. mutans biofilms. To evaluate the biofilm composition, the biomass (total dry-weight), colony forming unit (CFU), water-insoluble extracellular polysaccharides (EPS), water-soluble EPS and intracellular iodophilic polysaccharides (IPS) of 94 h old S. mutans biofilms were analysed. The amount of fluoride of old culture medium released from the materials during the experimental period was also determined. Each assay was performed in duplicate in at least four different experiments (n = 8).

Results

All biofilms showed similar initial rates of acid production (0.083–0.089 pH drop/min) and proton permeability (0.025–0.036 pH increase/min), irrespective of fluoride release from the materials. On the other hand, the amount of biomass, water-insoluble EPS and IPS of the biofilms on Unifil Flow, which releases a larger amount of fluoride in the early stages of biofilm formation, were significantly lower than those on the other materials (up to 27%, 38% and 36% reduction in biomass, water-insoluble and IPS, respectively).

Conclusions

Our finding suggests that fluoride releasing resin composites might contribute to the decrease in cariogenic composition of S. mutans biofilms if an appropriate amount of fluoride is released in the early stages of biofilm formation.     

Antimicrobial and antibiofilm action of Casbane Diterpene from Croton nepetaefolius against oral bacteria

ObjectiveThe antibacterial activity of Casbane Diterpene (CD) was evaluated in vitro against Streptococcus oralis, S. mutans, S. salivarius, S. sobrinus, S. mitis and S. sanguinis. The viability of planktonic cells was analysed by susceptibility tests (MIC and MBC) and antibiofilm action was assayed.MethodsThe minimal inhibitory and bactericidal concentrations (MIC and MBC) of oral Streptococcus were evaluated through microdilution tests. To assay antibiofilm activity, biofilms were generated on 96-wells polystyrene plates under the presence of CD and quantified by a crystal violet technique and colonies forming units counting.ResultsThe CD isolated from Croton nepetaefolius showed antimicrobial effect on planktonic forms and biofilms of oral pathogens, with MIC values of 62.5 μg/mL against Streptococcus oralis and values between 125 and 500 μg/mL against S. mutans, S. salivarius, S. sobrinus, S. mitis and S. sanguinis. CD showed an inhibitory effect on S. mutans biofilm formation at 250 μg/mL, and a decrease on viable cell of 94.28% compared to the normal biofilm growth.ConclusionsThe compound CD can be considered as a promising molecule for the treatment against oral pathogens responsible for dental biofilm.     

Dual-functional adhesive containing amorphous calcium phosphate nanoparticles and dimethylaminohexadecyl methacrylate promoted enamel remineralization in a biofilm-challenged environment

ObjectiveThe cariogenic biofilm on enamel, restoration, and bonding interface is closely related to dental caries and composite restoration failure. Enamel remineralization at adhesive interface is conducive to protecting bonding interface and inhibiting secondary caries. This study intended to assess the remineralization efficiency of adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) on initial caries lesion of biofilm-coated enamel.MethodsArtificial initial carious lesion was created via 72-hour immersion in demineralization solution and cariogenic biofilm was formed after 24-hour culture of Streptococcus mutans (S. mutans). Specimens were then divided into 4 groups: enamel control, enamel treated with NACP, DMAHDM and NACP+DMAHDM respectively. Samples next underwent 7-day cycling, 4 h in BHIS (brain heart infusion broth containing 1 % sucrose) and 20 h in AS (artificial saliva) per day. The pH of BHIS was tested daily. So did the concentration of calcium and phosphate in BHIS and AS. Live/dead staining, colony-forming unit (CFU) count, and lactic acid production of biofilms were measured 7 days later. The enamel remineralization efficiency was evaluated by microhardness testing and transverse microradiography (TMR) quantitatively.ResultsEnamel of NACP+DMAHDM group demonstrated excellent remineralization effectiveness. And the NACP+DMAHDM adhesive released a great number of Ca²⁺ and PO₄^3- ions, increased pH to 5.81 via acid neutralization, decreased production of lactic acid, and reduced CFU count of S. mutans (P < 0.05).SignificanceThe NACP+DMAHDM adhesive would be applicable to preventing secondary caries, strengthening enamel-adhesive interface, and extending the lifespan of composite restoration.     

Characterization of the clustered regularly interspaced short palindromic repeats sites in Streptococcus mutans isolated from early childhood caries patients

ObjectiveThe aim of this study was to analyze the characteristics of the clustered regularly interspaced short palindromic repeats (CRISPR) sites in 45 clinical Streptococcus mutans strains and their relationship to the clinical manifestations of early childhood caries (ECC).MethodsForty-five S. mutans strains were isolated from the plaque samples taken from sixty-three children. CRISPR sites were sequenced and BLAST was used to compare these sites to those in the CRISPRTarget database. The association between the distribution of CRISPR sites and the manifestation of caries was analyzed by Chi-Square test. Further, biofilm formation (by crystal violet staining) and the synthesis of polysaccharide (by anthrone-sulfuric method) of all clinical isolated S. mutans strains with both CRISPR sites and no CRISPR site were comapared. Finally, acidogenicity and acidurity of two typical strains were determined using pH drop and acid tolerance assays. Biofilm formation and EPS synthesis by two typical strains were compared by 3D CLSM (Confocal Laser Scanning Microscope) assays and the expression of gtf genes were evaluated using qPCR.ResultsWe found that most of the spacers in the clinical S. mutans strains were derived from Streptococcus phages APCM01 and M102. The number of CRISPR sites in these strains was associated with the clinical manifestations of ECC. Moreover, we found that the biofilm formation and EPS synthesis ability of the S. mutans strains with both CRISPR sites was significant improved.ConclusionsAn association was found between the distribution of CRISPR sites and the clinical manifestations of caries. The CRISPR sites might contribute to the cariogenic potential of S. mutans.     

Influence of orthodontic brackets design and surface properties on the cariogenic Streptococcus mutans adhesion

ObjectiveTo compare the surface properties of self-ligating metallic (SLM), ceramic esthetic, and conventional metallic (CM) brackets, and evaluate the adhesion of Streptococcus mutans biofilms to their surface, attempting to interpret the correlation between bracket type and enamel demineralization from a microbiological perspective.Materials and methodsTwenty-two brackets of each group were used. The brackets’ surface roughness was defined and the bacterial adhesion was performed using the strain S. mutans ATCC25175 with 8 h or 24 h of incubation time. The total bacterial adhesion (TBA) of biofilms was assessed using optical density (OD) methodology. To quantify bacteria viability (BV), the colony forming units (CFU) were counted. A scanning electron microscopy (SEM) observation of biofilms was also performed. Results: Ceramic brackets exhibited significantly higher roughness (0.304) compared to CM (0.090) and SLM (0.067) ones (C > CM = SLM). The data obtained with the TBA and BV tests showed that S. mutans biofilm formed on bracket groups exhibited similar results for both incubation periods. From the SEM images it is possible to observe that biofilm structure formed for 24 h was denser than that for 8 h of incubation with significantly more aggregates and cells for three groups.ConclusionThis in vitro study suggests that despite the higher surface roughness of ceramic brackets, this alone does not influence the adhesion of the S. mutans biofilms.Clinical relevanceFrom a microbiological perspective, the bracket's design may be more relevant than its surface roughness with respect to the adhesion of cariogenic bacteria biofilm with potential risk to dental enamel integrity.     

Candida tropicalis biofilm inhibition by ZnO nanoparticles and EDTA

ObjectiveBiofilm of Candida tropicalis denote as a complex cellular congregation with major implication in pathogenesis. This lifestyle of fungus as a biofilm can inhibit immune system and antifungal therapy in treatment of infectious disease especially medical device associated chronic disease. In this study effects of Zinc Oxide (ZnO) nanoparticles and EDTA were evaluated on C. tropicalis biofilm by using different techniques. ZnO nanoparticles were synthesized from Egg albumin.DesignTo assay the formation of biofilm of yeast cells like Fluconazole-susceptible C. tropicalis (ATCC 13,803) and fluconazole-resistant standard strains of C. tropicalis (ATCC 750) were grown in 24 well plates and antifungal effect of ZnO and EDTA were evaluated on C. tropicalis biofilm using ATP bioluminescence and tetrasodium salt (XTT) reduction assays.ResultsSynthesized ZnO NPs and EDTA had effective antifungal properties at the concentration of 5.2, 8.6 μg/ml for Fluconazole susceptible strain and 5.42, 10.8 μg/ml Fluconazole resistant strains of C. tropicalis biofilms compared to fluconazole drug.ConclusionIn present study we conclude, ZnO considered as a new agent in field of prevention C. tropicalis biofilms especially biofilms formed surface of medical device.