Polycationic Silver Nanoclusters Comprising Nanoreservoirs of Ag+ Ions with High Antimicrobial and Antibiofilm Activity.

Silver-based nano-antibiotics are rapidly developing as promising alternatives to conventional antibiotics. Ideally, to remain potent against a wide range of drug-resistant and anaerobic bacteria, silver-based nano-antibiotics should easily penetrate through the bacterial cell walls and actively release silver ions. In this study, highly monodispersed, ultrasmall (<3 nm), polycationic silver nanoclusters (pAgNCs) are designed and synthesized for the elimination of a range of common Gram-negative and Gram-positive pathogens and their corresponding established and matured biofilms, including those composed of multiple species. The pAgNCs also show greatly enhanced antibacterial efficacy against anaerobic bacteria such as Fusobacterium nucleatum and Streptococcus sanguinis. These results demonstrate that the cationic nature facilitates better penetration to the bacterial cell membrane while the presence of a high percentage (>50%) of silver ions (i.e., Ag+ nanoreservoirs) on the cluster surface maintains their efficiency in both aerobic and anaerobic conditions. Significantly, the pAgNCs showed a strong capacity to significantly delay the development of bacterial resistance when compared to similar-sized negatively charged silver nanoparticles or conventional antibiotics. This study demonstrates a novel design strategy that can lay the foundation for the development of future highly potent nano-antibiotics effective against a broad spectrum of pathogens and biofilms needed in many everyday life applications and industries.

Antimicrobial activity of a novel Spanish propolis against planktonic and sessile oral Streptococcus spp.

Increased bacterial resistance to traditional antimicrobial agents has prompted the use of natural products with antimicrobial properties such as propolis, extensively employed since ancient times. However, the chemical composition of propolis extracts is extremely complex and has been shown to vary depending on the region and season of collection, due to variations in the flora from which the pharmacological substances are obtained, being therefore essential for their antimicrobial activity to be checked before use. For this purpose, we evaluate the in vitro antimicrobial and anti-biofilm activity of a new and promising Spanish ethanolic extract of propolis (SEEP) on Streptococcus mutans and Streptococcus sanguinis, responsible, as dominant 'pioneer' species, for dental plaque. Results reveal that S. sanguinis is more sensitive to SEEP, slowing and retarding its growth considerably with lower concentrations than those needed to produce the same effect in S. mutans. SEEP presents concentration- and time-dependent killing activity and, furthermore, some of the subinhibitory concentrations employed increased biofilm formation even when bacterial growth decreased. Mono and dual-species biofilms were also inhibited by SEEP. Findings obtained clearly show the relevance of using biofilm and subinhibitory concentration models to determine optimal treatment concentrations.

Concentration-Dependent Multi-Potentiality of L-Arginine: Antimicrobial Effect, Hydroxyapatite Stability, and MMPs Inhibition.

This study's objective was to examine L-arginine (L-arg) supplementation's effect on mono-species biofilm (Streptococcus mutans/Streptococcus sanguinis) growth and underlying enamel substrates. The experimental groups were 1%, 2%, and 4% arg, and 0.9% NaCl was used as the vehicle control. Sterilised enamel blocks were subjected to 7-day treatment with test solutions and S. mutans/S. sanguinis inoculum in BHI. Post-treatment, the treated biofilms stained for live/dead bacterial cells were analysed using confocal microscopy. The enamel specimens were analysed using X-ray diffraction crystallography (XRD), Raman spectroscopy (RS), and transmission electron microscopy (TEM). The molecular interactions between arg and MMP-2/MMP-9 were determined by computational molecular docking and MMP assays. With increasing arg concentrations, bacterial survival significantly decreased (p < 0.05). The XRD peak intensity with 1%/2% arg was significantly higher than with 4% arg and the control (p < 0.05). The bands associated with the mineral phase by RS were significantly accentuated in the 1%/2% arg specimens compared to in other groups (p < 0.05). The TEM analysis revealed that 4% arg exhibited an ill-defined shape of enamel crystals. Docking of arg molecules to MMPs appears feasible, with arg inhibiting MMP-2/MMP-9 (p < 0.05). L-arginine supplementation has an antimicrobial effect on mono-species biofilm. L-arginine treatment at lower (1%/2%) concentrations exhibits enamel hydroxyapatite stability, while the molecule has the potential to inhibit MMP-2/MMP-9.

Inhibitory effects of propolis and essential oils on oral bacteria.

INTRODUCTION: Propolis is a natural composite balsam. In the past decade, propolis has been extensively investigated as an adjuvant for the treatment of periodontitis. This study aimed to investigate antimicrobial activities of propolis solutions and plant essential oils against some oral cariogenic (Streptococcus mutans, Streptococcus mitis, Streptococcus sanguis, Lactobacillus acidophilus) and periodontopathic bacteria (Actinomyces odontolyticus, Eikenella corrodens, Fusobacterium nucleatum). METHODOLOGY: Determination of the minimum inhibitory concentration (MIC): The antimicrobial activity of propolis and essential oils was investigated by the agar dilution method. Serial dilutions of essential oils were prepared in plates, and the assay plates were estimated to contain 100, 50, 25 and 12.5 µg/mL of active essential oils. Dilutions for propolis were 50, 25, 12.5 and 6.3 µg/mL of active propolis solutions. RESULTS: Propolis solutions dissolved in benzene, diethyl ether and methyl chloride, demonstrated equal effectiveness against all investigated oral bacteria (MIC=12.5 µg/mL). Propolis solution dissolved in acetone displayed MIC of 6.3 µg/mL only for Lactobacillus acidophilus. At the MIC of 12.5 µg/mL, essential oils of Salvia officinalis and Satureja kitaibelii were effective against Streptococcus mutans and Porphyromonas gingivalis, respectively. For the latter, the MIC value of Salvia officinalis was twice higher. CONCLUSIONS: The results indicate that propolis and plant essential oils appear to be a promising source of antimicrobial agents that may prevent dental caries and other oral infectious diseases.

Antibacterial and Antimicrobial Effects of Xanthorrhizol in the Prevention of Dental Caries: A Systematic Review.

BACKGROUND: Xanthorrhizol is one of the numerous phytochemicals whose pharmacological benefits have been explored for its antibacterial and antimicrobial effects. In light of the role bacteria play for initiating tooth decay, this present systematic review assessed xanthorrhizol's effect against dental caries. METHODS: The electronic databases including Pubmed, Scopus and Embase were searched up to September 2020, Studies examining the antibacterial and antimicrobial effects of xanthorrhizol in the prevention and treatment of dental caries. RESULTS: Eleven studies met the criteria for final inclusion. Findings from these studies showed that xanthorrhizol showed significant inhibition of notable caries causing bacteria including Streptococcus mutans, Streptococcus sanguinis, Enterococcus faecalis and Bacillus cereus. Furthermore, there was no reported toxicity. However, it could not selectively target the growth of cariogenic bacteria. CONCLUSION: So far, studies exploring the use of xanthorrhizol as a potential drug for the prevention and treatment of dental caries have shown promising outcomes. However, more work needs to be done especially in areas such as optimal dose or concentration, in addition, in vitro, in vivo and clinical studies and selective targeting of cariogenic bacteria has been performed.

Novel Amides Derivative with Antimicrobial Activity of Piper betle var. nigra Leaves from Indonesia.

Piper betle var. nigra is a tropical plant closely related to the common piper. P. betle has also been dubbed a promising source of natural antioxidants in herbal health products, antibacterial, antifungal, antimalarial, cytotoxic activity against the cancer cell lines K562 and HL-60, and antileishmanial. The aim of this study to observation Antimicrobial activity and isolation of chemical compound. The antimicrobial activity of P. betle extract was performed by well diffusion method against two oral pathogenic bacteria (Streptococcus mutans and Streptococcus sanguinis) and opportunistic pathogenic yeast (Candida albicans). The inoculum (bacterial and yeast suspension) was prepared from a 24-h culture on NB for bacterial suspension and on TSB for yeast suspension. Extraction and isolation using various method of chromatography. Isolated compounds were characterized by spectroscopic means. Our study showed antimicrobial activity from crude ethanol extract of leaves P. betle L. var. nigra against two oral pathogenic bacteria and opportunistic pathogenic yeast with concentration 0.5% and 1%. The first report of two new amides derivatives, piperenamide A (1) and piperenamide B (2) in P. betle L. var. nigra.

Potential Fatty Acid as Antibacterial Agent Against Oral Bacteria of Streptococcus mutans and Streptococcus sanguinis from Basil (Ocimum americanum): In vitro and In silico Studies.

BACKGROUND: Streptococcus mutans and Streptococcus sanguinis are Gram-positive bacteria that cause dental caries. MurA enzyme acts as a catalyst in the formation of peptidoglycan in bacterial cell walls, making it ideal as an antibacterial target. Basil (Ocimum americanum) is an edible plant that is diverse and has been used as a herbal medicine for a long time. It has been reported that basil has a pharmacological effect as well as antibacterial activity. The purpose of this study was to identify antibacterial compounds in O. americanum and analyze their inhibition activity on MurA enzyme. METHODS: Fresh leaves from O. americanum were extracted with n-hexane and purified by a combination of column chromatography on normal and reverse phases together with in vitro bioactivity assay against S. mutans ATCC 25175 and S. sanguinis ATCC 10556, respectively, while in silico molecular docking simulation of lauric acid (1) was conducted using PyRx 0.8. RESULTS: The structure determination of antibacterial compound by spectroscopic methods resulted in an active compound lauric acid (1). The in vitro evaluation of antibacterial activity in compound 1 showed Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values of 78.13 and 156.3 ppm and 1250 and 2500 ppm against S. sanguinis and S. mutans, respectively. Further analysis and in silico evaluation determined lauric acid (1) as MurA Enzyme inhibitor. Lauric acid (1) showed a binding affinity of -5.2 Kcal/mol, which was higher than fosfomycin. CONCLUSION: Lauric acid showed the potential as a new natural antibacterial agent through MurA inhibition in bacterial cell wall biosynthesis.

Dimethylated acylphloroglucinol meroterpenoids with anti-oral-bacterial and anti-inflammatory activities from Hypericum elodeoides.

Acylphloroglucinol meroterpenoids are adducts of the acylphloroglucinol unit and polyprenylated fragments (terpenoids) with attractive structures and bioactivities. During study of the medicinal molecules of the genus Hypericum, the first example of dimethylated acylphloroglucinol meroterpenoids with pyran-fused 6/6/6 tricyclic skeletons ((+)/(-)-elodeoidols A-F (1-6)), along with three biogenetical homologues (7-9) were isolated from the herbaceous plant of Hypericum elodeoides. Their structures including absolute configurations were then identified by nuclear magnetic resonance (NMR), high resolution electrospray ionization mass spectroscopy (HRESIMS), electronic circular dichroism (ECD) analysis and calculations. The monoterpene moiety of 1-6 were cyclized as two cyclohexanes and fused with a dimethylated acylphloroglucinol unit through an additional ether linkage, which led to an interesting pyran-fused linear or angle type 6/6/6 tricyclic skeleton. Compounds 5, 8 and 9 showed preferable antibacterial activities against three oral bacteria, among the MIC value of (+)-5 was 6.25 µg/ml; Compounds 3, 7 and 8 exhibited significant NO inhibitory activity against LPS induced RAW264.7 cells (IC50: 10.39 ± 0.49 ~ 34.25 ± 2.32 µM).

Potential Allylpyrocatechol Derivatives as Antibacterial Agent Against Oral Pathogen of S. sanguinis ATCC 10,556 and as Inhibitor of MurA Enzymes: in vitro and in silico Study.

BACKGROUND: Streptococcus sanguinis is Gram-positive bacteria that contribute to caries. Many antibacterial agents are resistant against bacteria so that the discovery of new antibacterial agents is a crucial issue. Mechanism of antibacterial agents by disrupting cell wall bacteria is a promising target to be developed. One of the enzymes contributing to the cell wall is MurA enzyme. MurA is an enzyme catalyzing the first step of peptidoglycan biosynthesis in the cell wall formation. Inhibiting MurA is an effective and efficient way to kill the bacteria. Source of bioactive compounds including the antibacterial agent can be found in natural product such as herbal plant. Piper betle L. was reported to contain active antibacterial compounds. However, there is no more information on the antibacterial activity and molecular mechanism of P. betle's compound against S. sanguinis. PURPOSE: The study aims to identify antibacterial constituents of P. betle L. and evaluate their activities through two different methods including in vitro and in silico analysis. MATERIALS AND METHODS: The antibacterial agent was purified by bioactivity-guided isolation with combination chromatography methods and the chemical structure was determined by spectroscopic methods. The in vitro antibacterial activity was evaluated by disc diffusion and dilution methods while the in silico study of a compound binds on the MurA was determined using PyRx program. RESULTS: The antibacterial compound identified as allylpyrocatechol showed inhibitory activity against S. sanguinis with an inhibition zone of 11.85 mm at 1%, together with MIC and MBC values of 39.1 and 78.1 µg/mL, respectively. Prediction for molecular inhibition mechanism of allylpyrocatechols against the MurA presented two allylpyrocatechol derivatives showing binding activity of -5.4, stronger than fosfomycin as a reference with the binding activity of -4.6. CONCLUSION: Two allylpyrocatechol derivatives were predicted to have a good potency as a novel natural antibacterial agent against S. sanguinis through blocking MurA activity that causes disruption of bacterial cell wall.

Adhesion of streptococci to titanium and zirconia.

The purpose of this study was to evaluate the adherence of streptococci to disks of titanium (commercially pure titanium: CpTi) and zirconia (tetragonal zirconia polycrystals: TZP). CpTi and yttria-stabilized TZP disks with a mirror-polished surface were used as specimens. The arithmetic mean surface roughness (Ra and Sa) and the surface wettability of the experimental specimens were measured. For analyzing the outermost layer of the experimental specimens, X-ray photoelectron spectroscopy (XPS) analysis was performed. Streptococcus sanguinis, S. gordonii, S. oralis, and S. mutans were used as streptococcal bacterial strains. These bacterial cultures were grown for 24 h on CpTi and TZP. The number of bacterial adhesions was estimated using an ATP-bioluminescent assay, and scanning electron microscope (SEM) observation of the adhered bacterial specimens was performed. No significant differences in surface roughness or wettability were found between CpTi and TZP. In XPS analyses, outermost layer of CpTi included Ti0 and Ti4+, and outermost layer of TZP included Zr4+. In the cell adhesion assay, the adherences of S. sanguinis, S. gordonii, and S. oralis to TZP were significantly lower than those to CpTi (p < 0.05); however, significant difference was not observed for S. mutans among the specimens. The adherence to CpTi and TZP of S. mutans was significantly lower than that of S. sanguinis, S. gordonii, and S. oralis. These results were confirmed by SEM. S. sanguinis, S. gordonii, and S. oralis adhered less to TZP than to CpTi, but the adherence of S. mutans was similar to both surfaces. S. mutans was less adherent compare with the other streptococci tested in those specimens.

Antibiofilm coatings based on protein-engineered polymers and antimicrobial peptides for preventing implant-associated infections.

Implant-associated infections (IAIs) are one of the leading concerns in orthopedics and dentistry as they commonly lead to implant failure. The presence of biofilms and, increasingly frequently, drug-resistant bacteria further impairs the efficacy of conventional antibiotics. Immobilization of antimicrobial peptides (AMPs) on implant surfaces is a promising alternative to antibiotics for prevention of IAIs. In addition, the use of functional linkers for the AMP tethering enables to increase the antimicrobial potential and the bioactivities of the coating. In this study, an extracellular-matrix-mimicking system based on elastin-like recombinamers (ELRs) has been developed for the covalent anchoring of AMPs and investigated for use as a hybrid antibiofilm coating. A drip-flow biofilm reactor was used to simulate in vivo environmental dynamic conditions, thus showing that the presence of the AMPs in the hybrid coatings provided strong antibiofilm activity against monospecies and microcosm biofilm models of clinical relevance. These results, together with an excellent cytocompatibility towards primary gingival fibroblasts, encourage the use of ELRs as multivalent platforms for AMPs and open up a wide range of possibilities in the biofabrication of advanced coatings combining the antibiofilm potential of AMPs and the outstanding tunability and biomechanical properties of the ELRs.

UV-photofunctionalization of a biomimetic coating for dental implants application.

Photofunctionalization mediated by ultraviolet (UV) rays changes the physico-chemical characteristics of titanium (Ti) and improves the biological activity of dental implants. However, the role of UV-mediated photofunctionalization of biofunctional Ti surfaces on the antimicrobial and photocatalytic activity remains unknown and was investigated in this study. Commercially pure titanium (cpTi) discs were divided into four groups: (1) machined samples without UV light application [cpTi UV-]; (2) plasma electrolytic oxidation (PEO) treated samples without UV light application [PEO UV-]; (3) machined samples with UV light application [cpTi UV+]; and (4) PEO-treated samples with UV light application [PEO UV+]. The surfaces were characterized according to their morphology, roughness, crystalline phase, chemical composition and wettability. The photocatalytic activity and proteins adsorption were measured. For the microbiological assay, Streptococcus sanguinis was grown on the disc surfaces for 1 h and 6 h, and the colony forming units and bacterial organization were evaluated. In addition, to confirm the non-cytotoxic effect of PEO UV +, human gingival fibroblast (HGF) cells were cultured in a monolayer onto each material surface and the cells viability and proliferation evaluated by a fluorescent cell staining method. PEO treatment increased the Ti surface roughness and wettability (p < 0.05). Photofunctionalization reduced the hydrocarbon concentration and enhanced human blood plasma proteins and albumin adsorption mainly for the PEO-treated surface (p < 0.05). PEO UV+ also maintained higher wettability values for a longer period and provided microbial reduction at 1 h of bacterial adhesion (p = 0.012 vs. PEO UV-). Photofunctionalization did not increase the photocatalytic activity of Ti (p > 0.05). Confocal microscopy analyses demonstrated that PEO UV+ had no cell damage effect on HGF cells growth even after 24 h of incubation. The photofunctionalization of a biofunctional PEO coating seems to be a promising alternative for dental implants as it increases blood plasma proteins adsorption, reduces initial bacterial adhesion and presents no cytotoxicity effect.

Availability of Zinc Impacts Interactions between Streptococcus sanguinis and Pseudomonas aeruginosa in Coculture.

Airway infections associated with cystic fibrosis (CF) are polymicrobial. We reported previously that clinical isolates of Pseudomonas aeruginosa promote the growth of a variety of streptococcal species. To explore the mechanistic basis of this interaction, we performed a genetic screen to identify mutants of Streptococcus sanginuis SK36 whose growth was no longer enhanced by P. aeruginosa PAO1. Mutations in the zinc uptake systems of S. sanguinis SK36 reduced growth of these strains by 1 to 3 logs compared to that of wild-type S. sanguinis SK36 when grown in coculture with P. aeruginosa PAO1, and exogenous zinc (0.1 to 10 µM) rescued the coculture defect of zinc uptake mutants of S. sanguinis SK36. Zinc uptake mutants of S. sanguinis SK36 had no obvious growth defect in monoculture. Consistent with competition for zinc driving coculture dynamics, S. sanguinis SK36 grown in coculture with P. aeruginosa showed increased expression of zinc uptake genes compared to that of S. sanguinis grown alone. Strains of P. aeruginosa PAO1 defective in zinc transport also supported ∼2-fold more growth by S. sanguinis compared to that in coculture with wild-type P. aeruginosa PAO1. An analysis of 118 CF sputum samples revealed that total zinc levels varied from ∼5 to 145 µM. At relatively low zinc levels, Pseudomonas and Streptococcus spp. were found in approximately equal abundance; at higher zinc levels, we observed a decline in relative abundance of Streptococcus spp., perhaps as a result of increasing zinc toxicity. Together, our data indicate that the relative abundances of these microbes in the CF airway may be impacted by zinc levels.IMPORTANCE Polymicrobial infections in CF cases likely impact patient health, but the mechanism(s) underlying such interactions is poorly understood. Here, we show using an in vitro model system that interactions between Pseudomonas and Streptococcus are modulated by zinc availability, and clinical data are consistent with this model. Together with previous studies, our work supports a role for metal homeostasis as a key factor driving microbial interactions.

Effects of Norspermidine on Dual-Species Biofilms Composed of Streptococcus mutans and Streptococcus sanguinis.

The present study aimed at investigating the influence of norspermidine on the formation of dual-species biofilms composed of Streptococcus mutans (S. mutans) and Streptococcus sanguinis (S. sanguinis). Crystal violet assay was conducted to assess the formation of single-species biofilms of S. mutans and S. sanguinis, and the growth curve was carefully observed to monitor the growth of these two species of bacteria. Fluorescence in situ hybridization (FISH) and MTT array were used to analyze the composition and metabolic activity of the dual-species biofilms, respectively. Extracellular polysaccharides (EPS)/bacteria staining, anthrone method, and scanning electron microscopy (SEM) imaging were conducted to study the synthesis of EPS by dual-species biofilms. Lactic acid assay and pH were measured to detect dual-species biofilm acid production. We found that norspermidine had different effects on S. mutans and S. sanguinis including their growth and biofilm formation. Norspermidine regulated the composition of the dual-species biofilms, decreased the ratio of S. mutans in dual-species biofilms, and reduced the metabolic activity, EPS synthesis, and acid production of dual-species biofilms. Norspermidine regulated dual-species biofilms in an ecological way, suggesting that it may be a potent reagent for controlling dental biofilms and managing dental caries.

[Influence of environmental factors on the two-species biofilm formed by Streptococcus oligofermentans and Streptococcus mutans].

Objective: To study the influence of environmental factors on the two-species biofilm formed by the combinations of Streptococcus oligofermentans (So) with Streptococcus mutans (Sm) and Streptococcus sanguinis (Ss) with Sm so as to evaluate the role of So in maintaining the microecological balance of the oral cavity. Methods: Single-and two-species biofilms were grown on saliva-coated surfaces (glass tube and 96-well plate). Colony-counting method and safranin staining method were used to measure the biofilms formed under various oxygen conditions (aerobic and anaerobic), sucrose conditions (0%, 1% and 5% sucrose concentrations) and pH conditions (5.5, 6.0, 6.5, 7.0, 7.5 and 8.0). Results: Comparing the numbers of Sm in two co-cultures under various conditions, Sm counts in So+Sm group [(7.70±2.46)×10(8) CFU/ml] were significantly lower than those in Ss+Sm group [(9.00±1.13)×10(8) CFU/ml] in aerobic environment (P<0.05). Sm counts in So+Sm group [(2.80±0.52)×10(8) CFU/ml] were also significantly lower than those in the Ss+Sm group [(4.00±1.25)×10(8) CFU/ml] in anaerobic environment (P<0.05). The Sm counts in So+Sm group [(8.90±0.82)×10(8) CFU/ml] were significantly higher than those in Ss+Sm group [(7.50±1.73)×10(8) CFU/ml] in 0% sucrose environment (P<0.05). The Sm counts in So+Sm group [(5.70±2.94)×10(8) CFU/ml] were significantly lower than those in Ss+Sm group [(10.30±3.21) ×10(8) CFU/ml] in 1% sucrose environment (P<0.05). The Sm counts in So+Sm group [(6.10±1.71)×10(8) CFU/ml] were also significantly lower than those in Ss+Sm group [(7.40±1.20)×10(8) CFU/ml] in 5% sucrose environment (P<0.05). The Sm counts in So+Sm group [(3.50±1.50)×10(8) CFU/ml] were significantly lower than those in Ss+Sm group [(10.70±2.80)×10(8) CFU/ml] in pH7.0 environment (P<0.05). Comparing the formation of biofilm after 24 h cultivation, the Sm counts in So+Sm group were significantly lower than those in Ss+Sm group both in aerobic and anaerobic environments (P<0.05). The Sm counts in So+Sm group were significantly higher than those in Ss+Sm group in 0% sucrose environment (P<0.05). The Sm counts in So+Sm group were significantly lower than those in Ss+Sm group in 1% and 5% sucrose and pH 7.0 environments (P<0.05). Both So and Ss had no inhibitory effect on Sm in pH5.5 and pH8.0 environments. Conclusions: In the in vitro two-species co-culture systems, So showed stronger inhibitory effects than Ss on Sm and its inhibitory ability might influenced by various environmental factors.

Effect of D-cysteine on dual-species biofilms of Streptococcus mutans and Streptococcus sanguinis.

Dental caries is a highly prevalent disease worldwide. It is caused by the cariogenic biofilms composed of multiple dynamic bacteria on dental surface. Streptococcus mutans and Streptococcus sanguinis are resident members within the biofilms and an antagonistic relationship has been shown between these two species. S. mutans, as the major causative microorganism of dental caries, has been reported to be inhibited by free D-cysteine (D-Cys). However, whether D-Cys could affect S. sanguinis and the interspecies relationship between S. mutans and S. sanguinis remains unknown. The aim of the current study was to investigate the effect of D-Cys on the growth and cariogenicity of dual-species biofilms formed by S. mutans and S. sanguinis. We measured dual-species biofilms biomass, metabolic activity, lactate production. We also detected the biofilms structure, the ratio of live/dead bacteria, extracellular polysaccharide (EPS) synthesis and bacterial composition in the dual-species biofilms. We found that D-Cys could reduce the metabolic activity and lactic acid production of dual-species biofilms (p < 0.05). In addition, biofilms formation, the proportion of S. mutans in dual-species biofilms, and EPS synthesis were decreased with D-Cys treatment. The results suggested that D-Cys could inhibit the growth and cariogenic virulence of dual-species biofilms formed by S. mutans and S. sanguinis, indicating the potential of D-Cys in clinical application for caries prevention and treatment.

Inhibitory Effects of Lingonberry Extract on Oral Streptococcal Biofilm Formation and Bioactivity.

Phenolic compounds in fruits such as cranberries have been shown to promote a number of biological activities. The purpose of this study was to investigate the effects of polyphenolic compound-containing lingonberry extract on oral streptococci and compare them with the known anti-cariogenic activity of cranberries. Water-soluble and polyphenol-rich fractions (Fractions I and II, respectively) were isolated from cranberries and lingonberries. The effects of those fractions on the biofilm formation ability and bioactivity of Streptococcus mutans MT8148R, Streptococcus sobrinus 6715, and Streptococcus sanguinis ATCC 10556 were then evaluated. Cranberry or lingonberry Fraction II (at 0.5-1 mg/ml) significantly reduced biofilm formation by S. mutans, S. sobrinus, and S. sanguinis. In contrast, cranberry or lingonberry Fraction I (at 0.5-2 mg/ml) increased biofilm formation by S. mutans and S. sobrinus, but not by S. sanguinis. Fractions I and II (at 1-2 mg/ml) also reduced the bioactivity of S. mutans, while Fraction II (at 0.5 mg/ml) enhanced the bioactivity of all tested strains. The results revealed that lingonberries contained a larger amount of polyphenol than cranberries and that they showed almost the same level of activity against the biofilm formation ability and bioactivity of oral streptococci. This indicates that polyphenol-rich lingonberry fraction offers a promising natural food derivative for prevention of dental caries.

What every dentist should know about antibiotic-resistant bacteria.

The emergence of antibiotic-resistant bacteria has complicated patient treatment and yielded poorer outcomes. This article provides an overview for dental professionals of the challenges posed by resistant microbial strains and the research efforts to overcome this significant obstacle.

Introduction of 5-aminolevulinic acid as a theranostics agent in dentistry.

OBJECTIVE: The aim of this paper is to study the theranostic potential of 5-Aminolevulinic Acid (5-ALA)in dentistry. METHODS: Photodynamic inactivation (PDI) and fluorescence spectroscopy of Streptococcus sanguis, and laser induced fluorescence (LIF) of several decayed teeth were performed using 5-ALA. RESULTS: In the absence of 5-ALA, 15 min illumination of the bacteria by the means of an LED light source led to only 1.16% viability reduction. On the other hand, 5-ALA revealed remarkable dark toxicity at concentrations above 20 µM. Furthermore, the synergistic effects of 10 µM 5-ALA and illumination by the light source for 5 and 15 min intervals led respectivelyto0.74log10 and 1.69log10 reduction of viability. Also, fluorescence spectroscopy of the bacteria showed a direct relationship between emission line intensity at 620 nm and the concentration of 5-ALA. In dental experiments, following exposing tooth with 40 mM 5-ALA, a significant autofluorescence growth was observed just in the decayed parts. CONCLUSION: Based on the strong dual modality of 5-ALA to annihilate cariogenic bacteria through photodynamic inactivation and enhancing LIF intensity for identification of dental caries, 5-ALA is proposed as a theranostic agent in dentistry.

Antimicrobial effects of the ginsenoside Rh2 on monospecies and multispecies cariogenic biofilms.

AIMS: To investigate the effects of the ginsenoside Rh2 on monospecies and multispecies cariogenic biofilms and explore the mechanism of the antibiofilm effect of Rh2 in vitro. METHODS AND RESULTS: Streptococcus mutans, Streptococcus sobrinus and Streptococcus sanguinis were chosen to form the monospecies or multispecies biofilms. Crystal violet staining and laser scanning confocal microscopy were used to observe the effect of Rh2 on biofilms in vitro. Cytotoxicity was examined by the Cell Counting Kit-8. The effects of Rh2 on bacterial membranes were observed via transmission electron microscopy (TEM). The isobaric tags for relative and absolute quantification (iTRAQ) method were used to profile the common differentially expressed proteins. Gene expression was analysed by reverse transcription quantitative polymerase chain reaction. In general, the treatment of cariogenic biofilms with Rh2 significantly decreased biomass accumulation by inhibiting bacterial growth and extracellular polysaccharide synthesis without any cytotoxic effects. TEM imaging showed that Rh2 could disrupt the cell membranes of these bacteria. The iTRAQ results indicated that the levels of mannose-specific IIC/D and acetaldehyde/alcohol dehydrogenase were substantially down-regulated, while the mRNA expression of the corresponding genes were significantly changed. CONCLUSIONS: Our data revealed a potential application for Rh2 in the protection against dental caries via the inhibition of cariogenic biofilms. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes the first application of a ginsenoside against multispecies cariogenic biofilms. Rh2 may serve as an alternative agent to prevent dental caries by effectively modulating the pathogenic potentials of oral biofilms.