Caries Pathogen Research Articles

Monomelittoside and Dichotomoside D from bark extract of Alstonia scholaris (L.) R. Br. inhibits dental caries pathogen Streptococcus mutans

Dental caries advances to be a significant global health concern, primarily attributed to the virulent actions of Streptococcus mutans. The antibacterial property of the bark extract of Alstonia scholaris was assessed using standard disc diffusion assays, which revealed significant inhibition of S. mutans. Subsequently, we determined the Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) revealed potent antibacterial activity of bark extract against S. mutans, at MIC and MBC values 62.5 and 125 µg/mL, respectively and antibiofilm activity at 125 µg/mL. Furthermore, cytotoxicity assays showed no adverse effects on mammalian cells. Moreover, we employed liquid chromatography–mass spectrometry to identify bioactive compounds in the bark extract and revealed the presence of major active compounds as Monomelittoside and Dichotomoside D effective in targeting the S. mutans. These findings showed that, the promising antibacterial efficacy of Monomelittoside and Dichotomoside D, highlighting their potential as natural therapeutics for combating dental caries.

Streptococcus mutans outer membrane vesicles affect inflammasome activation and the glycolysis of macrophages

Recent studies indicate that bacterial outer membrane vesicles (OMVs) play a significant role in bacterial virulence and pathogenicity. Streptococcus mutans (S. mutans), a principal pathogen in dental caries, secretes a substantial number of OMVs. However, the impact of S. mutans OMVs on oral health and their underlying pathogenic mechanisms remain poorly understood. Macrophages were the initial innate immune cells to respond to bacterial invaders and their products. Therefore, we purified S. mutans OMVs, which stimulated macrophages. Compared to controls, RT-PCR and ELISA analyses revealed that S. mutans OMVs significantly increased the production of IL-1β, IL-6, TNF-α and IL-8, with IL-1β being notably elevated. IL-1β production and secretion are tightly regulated by the inflammasome. Western blot analyses demonstrated that S. mutans OMVs upregulated the expression of inflammasome components, including NLRP3, NLRC4, ASC and AIM2, with a marked increase in NLRP3 expression. Silencing different inflammasome components with siRNA revealed a reduction in IL-1β secretion induced by S. mutans OMVs, particularly through NLRP3. Additionally, ATP production and K+ efflux were found to be crucial for NLRP3 activation. Prolonged stimulation with S. mutans OMVs resulted in increased lactate production and elevated expression of glycolysis-related genes Glut-1, PFKFB3, and HK I, indicating that S. mutans OMVs significantly induce macrophage glycolysis. Furthermore, S. mutans OMVs were shown to enhance biofilm formation, increase S. mutans colonisation on epithelial cells, and inhibit macrophage phagocytosis, thereby improving the survival of S. mutans in the oral cavity. In summary, S. mutans OMVs promote the survival of S. mutans in the mouth through multiple mechanisms, potentially influencing the development of dental caries.

A Strain of Streptococcus mitis Inhibits Biofilm Formation of Caries Pathogens via Abundant Hydrogen Peroxide Production.

Commensal oral streptococci that colonize supragingival biofilms deploy mechanisms to combat competitors within their niche. Here, we determined that Streptococcus mitis more effectively inhibited biofilm formation of Streptococcus mutans within a seven species panel. This phenotype was common amongst all assayed isolates of S. mutans, but was specific to a single strain of S. mitis, ATCC 49456. The growth inhibitory factor was not effectively carried in spent supernatants of S. mitis. However, we documented ATCC 49456 to accumulate 4-5 times more hydrogen peroxide (H2O2) than other species tested, and 5-18 times more than other S. mitis strains assayed. The S. mutans biofilm formation inhibitory phenotype was reduced when grown in media containing catalase or with a S. mitis mutant of pyruvate oxidase (spxB; pox), confirming that SpxB-dependent H2O2 production was the main antagonistic factor. Addition of S. mitis within hours after S. mutans inoculation was effective at reducing biofilm biomass, but not for 24 h pre-formed biofilms. Transcriptome analysis revealed responses for both S. mitis and S. mutans, with several S. mutans differentially expressed genes following a gene expression pattern previously described, while others being unique to the interaction with S. mitis. Finally, we show that S. mitis also affected coculture biofilm formation of several other commensal streptococci. Our study shows that strains with abundant H2O2 production are effective at inhibiting initial growth of caries pathogens like S. mutans, but are less effective at disrupting pre-formed biofilms and have the potential to influence the stability of other oral commensal strains.

Ionic Liquid-Based Silane for SiO2 Nanoparticles: A Versatile Coupling Agent for Dental Resins.

The current longevity of dental resins intraorally is limited by susceptibility to acidic attacks from bacterial metabolic byproducts and vulnerability to enzymatic or hydrolytic degradation. Here, we demonstrate synthesizing an ionic liquid-based antibiofilm silane effective against Streptococcus mutans, a major caries pathogen. Furthermore, we incorporate this silane into dental resins, creating antibiofilm- and degradation-resistant materials applicable across resin types. FTIR, UV-vis, and NMR spectroscopy confirmed the synthesis of the expected ionic liquid-based silane. The characterization of SiO2 after the silanization indicated the presence of the silane and how it interacted with the oxide. All groups achieved a degree of conversion similar to that found for commercial resin composites immediately and after two months of storage in water. The minimum of 2.5 wt % of silane led to lower softening in solvent than the control group (GCTRL) (p < 0.05). While the flexural strength indicated a lower value from 1 wt % of silane compared to GCTRL (p < 0.05), the ultimate tensile strength did not indicate differences among groups (p > 0.05). There was no difference within groups between the immediate and long-term tests of flexural strength (p > 0.05) or ultimate tensile strength (p > 0.05). The addition of at least 5 wt % of silane reduced the viability of S. mutans compared to GCTRL (p < 0.05). The fluorescence microscopy analysis suggested that the higher the silane concentration, the higher the amount of bacteria with membrane defects. There was no difference among groups in the cytotoxicity test (p > 0.05). Therefore, the developed dental resins displayed biocompatibility, proper degree of conversion, improved resistance against softening in solvent, and stability after 6 months of storage in water. This material could be further developed to produce polymeric antimicrobial layers for different surfaces, supporting various potential avenues in developing novel biomaterials with enhanced therapeutic characteristics using ionic liquid-based materials.

Enhancing Dental Material Performance: Tung Oil-Infused Polyurea Microcapsule Coatings for Self-Healing and Antimicrobial Applications.

Within the realm of dental material innovation, this study pioneers the incorporation of tung oil into polyurea coatings, setting a new precedent for enhancing self-healing functionality and durability. Originating from an ancient practice, tung oil is distinguished by its outstanding water resistance and microbial barrier efficacy. By synergizing it with polyurea, we developed coatings that unite mechanical strength with biological compatibility. The study notably quantifies self-healing efficiency, highlighting the coatings' exceptional capacity to mend physical damages and thwart microbial incursions. Findings confirm that tung oil markedly enhances the self-repair capabilities of polyurea, leading to improved wear resistance and the inhibition of microbial growth, particularly against Streptococcus mutans, a principal dental caries pathogen. These advancements not only signify a leap forward in dental material science but also suggest a potential redefinition of dental restorative practices aimed at prolonging the lifespan of restorations and optimizing patient outcomes. Although this study lays a substantial foundation for the utilization of natural oils in the development of medical-grade materials, it also identifies the critical need for comprehensive cytotoxicity assays. Such evaluations are essential to thoroughly assess the biocompatibility and the safety profile of these innovative materials for clinical application. Future research will concentrate on this aspect, ensuring that the safety and efficacy of the materials align with clinical expectations for dental restorations.

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

Globally, oral diseases affect nearly 3.5billion 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 thesugars 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.

Effect of peanut stilbenoids, arachidin-1 and arachidin-3, on Streptococcus mutans growth and acid production

In this study we evaluated the effect of prenylated peanut stilbenoids on the growth, biofilm accumulation and acid production of the dental caries pathogen Streptococcus mutans. Prior research with the non-prenylated stilbenes, resveratrol and piceatannol, has shown that these molecules are active against S. mutans. Here we sought to determine if the addition of a prenyl group to the stilbene backbone increased anti-S. mutans activities. Two prenylated stilbenes, arachidin-1 and arachidin-3, were produced using a peanut hairy root production system. Compared to resveratrol and piceatannol, both arachidin-1 and arachidin-3 led to greater inhibition of S. mutans planktonic growth. This effect also led to reduced biofilm formation, by inhibiting growth, instead of a specific action against biofilm cells. Lastly, sub-MIC concentrations of arachidin-3 reduced the acid production of S. mutans above the ‘critical pH’ that leads to tooth enamel erosion. In summary, stilbenoids have anti-S. mutans activity, and prenylation enhances this activity.

The In Vitro Assessment of Antibacterial and Antioxidant Efficacy in Rosa damascena and Hypericum perforatum Extracts against Pathogenic Strains in the Interplay of Dental Caries, Oral Health, and Food Microbiota.

The rising demand for novel antibiotic agents prompts an investigation into natural resources, notably plant-derived compounds. In this study, various extracts (aqueous, ethanolic, aqueous-ethanolic, and enzymatic) of Rosa damascena and Hypericum perforatum were systematically evaluated against bacterial strains isolated from dental lesions (n = 6) and food sources (raw milk and broiler carcass, n = 2). Minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), antibiofilm activity, and time-kill kinetics were assessed across a range of extract concentrations, revealing a dose-responsive effect. Notably, some extracts exhibited superior antibacterial efficacy compared to standard clinical antibiotics, and the time-kill kinetics demonstrated a rapid elimination of bacterial loads within 24 h. The susceptibility pattern proved strain-specific, contingent upon the extract type, yet all tested pathogens exhibited sensitivity. The identified extracts, rich in phenolic and polyphenolic compounds, as well as other antioxidant properties, contributed to their remarkable antibiotic effects. This comprehensive investigation not only highlights the potential of Rosa damascena and Hypericum perforatum extracts as potent antibacterial agents against diverse bacterial strains including caries pathogens, but also underscores their rapid action and dose-dependent efficacy. The findings suggest a promising avenue for harnessing plant-derived compounds in the development of novel antimicrobial strategies against dental caries and other oral inflammations, bridging the gap between natural resources and antibiotic discovery.

Evaluation and comparison of antibacterial efficacy of different concentrations of Chhattisgarh herbal product-Terminalia chebula fruit extract in opposition to Enterococcus faecalis: An invitro study.

Due to the low cost, natural origin, higher safety margins, and little to negligible adverse effects of herbal medications, the use of plants and plant derivatives in medicine is becoming increasingly widespread. Terminalia chebula is among the most significant medicinal plants in ayurvedic, siddha, unani, and homeopathic remedies. It is ranked first in Ayurvedic material medicine. T. chebula has been shown to have established effects against various bacterial and fungal infections, including dental caries pathogens. In recent years, there has been a rise in interest in dentistry and medicine related to Enterococcus faecalis. The research aimed to assess the antibacterial effectiveness of different concentrations of T. chebula ethanolic fruit extract (10%, 40%, and 100%) in opposition to E. faecalis and compare it with 2% chlorhexidine. For the study, T. chebula ethanolic fruit extracts were obtained and prepared with Group I: -10% concentration, Group II: -40% concentration, Group III: -100% concentration, and Group IV: -2% chlorhexidine. Colonies of E. faecalis were cultivated in brain heart infusion (BHI) broth at 37°C and were inoculated in 16 BHI agar plates. Then, on the petri dishes, four wells were created (8 mm diameter) using a metal borer. The Agar well diffusion method was used to examine the antibacterial activity, and the zones of inhibition around the wells were noted. The obtained data were statistically analyzed using one-way ANOVA and post-hoc tests. The result shows that as the concentration increases, there is an increase in the efficacy of the antibacterial property of the extract before it reaches the saturation point. The decreasing order of antibacterial was chlorhexidine >100% T. chebula >40% T. chebula >10% T. chebula. The production of contemporary pharmaceuticals from T. chebula was addressed, as the global scenario is currently evolving toward using nontoxic plant products with traditional medicinal benefits.

In vitro anticariogenic activity of aqueous extract of Psidium guajava leaf against Streptococcus oralis – A dormant pathogen for dental caries

ABSTRACT Background: Dental caries is a complicated, multifaceted illness that affects teeth and leads to serious cavities both inside and outside the teeth. Aim: This study aims to determine the efficacy of Psidium guajava leaf extract against Streptococcus oralis. Materials and Methods: P. guajava leaves were extracted in water using the Soxhlet technique, and to identify the existence of several beneficial substances, phytochemical screening was carried out. The inhibitory properties of the aqueous extract were tested against S. oralis. Antimicrobial activity was determined by the agar well diffusion method. The minimum inhibitory concentration (MIC) was determined by the liquid dilution method, and the minimum bactericidal concentration (MBC) was determined by the agar plate method. Results: Qualitative analysis of phytochemicals by standard methods showed the presence of various bioactive compounds. Using the well diffusion method, it has been determined that P. guajava leaf extract has antibacterial activity against S. oralis. The determination of the MIC and MBC showed that the extract exhibited an antimicrobial effect against cariogenic bacteria. Conclusion: P. guajava leaf extract contains bioactive compounds that have a significant impact on the avoidance of dental cariogens. P. guajava leaf extract is effective against S. oralis.

CULTURE-DEPENDENT APPROACHES AMONG THE CARIES PATHOGENS ISOLATED FROM THE CARIOUS DENTINE AND THEIR EMERGING DRUG RESISTANCE

Objective: To evaluate the commonest caries pathogens from different type of caries andto screen for the emergence of drug resistance among the caries causing pathogenic bacteria.&#x0D; Methods: A cross-sectional study was conducted in the department of Microbiology. Sample Size was 44 and samples from carious dentine which was immediately transported to the microbiology laboratory. Samples were processed microbiologically to isolate the caries pathogens. Identification of strains were done by standard biochemical characterization studies. The isolates were subjected to antimicrobial sensitivity test. The results were recorded and analyzed for drug resistance.&#x0D; Results: Out of 44 patients, 40 aerobic bacteria, 2 anaerobic bacteria and 2 fungi were isolated. Out of the 40 aerobic bacteria, the most common isolated was Klebsiella pneumoniae followed by Pseudomonas spp. and Streptococcus viridians. Ciprofloxacin, Gentamycin and Linezolid showed excellent activity against Gram-positive Bacteria. The most frequently involved teeth of dental caries were mandibular 1st molar (54.54%) followed by Mandibular 2nd molar (13.63%).&#x0D; Conclusion: In our study we found that Klebsiella pneumoniae, Pseudomonas sp., Streptococcus viridians were the most frequent organisms encountered. The study implicates the need for time to time antimicrobial susceptibility examination of the dental caries pathogens that will help to prevent the emergence of resistance property among the dentinal pathogenic organisms.

Antibacterial mechanism of areca nut essential oils against Streptococcus mutans by targeting the biofilm and the cell membrane.

Dental caries is one of the most common and costly biofilm-dependent oral diseases in the world. Streptococcus mutans is the major cariogenic pathogen of dental caries. S. mutans synthesizes extracellular polysaccharides by autologous glucosyltransferases, which then promotes bacterial adhesion and cariogenic biofilm formation. The S. mutans biofilm is the principal target for caries treatment. This study was designed to explore the antibacterial activity and mechanisms of areca nut essential oil (ANEO) against S. mutans. The ANEOs were separated by negative pressure hydro-distillation. The Kirby-Bauer method and broth microdilution method were carried out to evaluate the antibacterial activity of different ANEOs. The antibacterial mechanism was revealed by crystal violet staining, XTT reduction, microbial adhesion to hydrocarbon test, extracellular polysaccharide production assay, glucosyltransferase activity assay, lactate dehydrogenase leaking, propidium iodide staining and scanning electron microscopy (SEM). The cytotoxicity of ANEOs was determine by MTT assay. The ANEOs separated at different temperatures exhibited different levels of antibacterial activity against S. mutans, and the ANEO separated at 70°C showed the most prominent bacteriostatic activity. Anti-biofilm experiments showed that the ANEOs attenuated the adhesion ability of S. mutans by decreasing the surface hydrophobicity of the bacteria, prevented S. mutans biofilm formation by inhibiting glucosyltransferase activity, reducing extracellular polysaccharide synthesis, and reducing the total biofilm biomass and activity. SEM further demonstrated the destructive effects of the ANEOs on the S. mutans biofilm. Cell membrane-related experiments indicated that the ANEOs destroyed the integrity of the cell membrane, resulting in the leakage of lactic dehydrogenase and nucleic acids. SEM imaging of S. mutans cell showed the disruption of the cellular morphology by the ANEOs. The cytotoxicity assay suggested that ANEO was non-toxic towards normal oral epithelial cells. This study displayed that ANEOs exerted antibacterial activity against S. mutans primarily by affecting the biofilm and disrupting the integrity of the cell membrane. ANEOs has the potential to be developed as an antibacterial agent for preventing dental caries. Additionally, a new method for the separation of essential oil components is presented.

Influence of the orthodontic bonding procedure on biofilm formation.

In orthodontics, white spot lesions are a persistent and widespread problem caused by the demineralization of buccal tooth surfaces around bonded brackets. The remaining adhesive around the brackets leads to surface roughness, which might contribute to demineralization. The present in vitro study aimed to compare a conventional and a modern adhesive system (APC Flash-Free technology) for orthodontic brackets with regard to the adhesion of Streptococcus sobrinus, a leading caries pathogen. This in vitro study included 20 premolar teeth and compared 10 APC Flash-Free adhesive-coated ceramic brackets (FF)with 10 conventionally bonded (CB) ceramic clarity brackets. Specimens were incubated in an S. sobrinus suspension for 3 h. To evaluate the bacterial formation, samples were analysed with a scanning electron microscope (SEM). Imaging software was used to quantify and statistically compare percentage values of colonization (PVC) in both groups' adhesion and transition areas. We found a significant difference in biofilm formation between the groups for the adhesive and transition areas. PVC in the adhesive area was approximately 10.3-fold greater for the CB group compared with the FF group (median: 3.2 vs 0.31; P < 0.0001). For the transition area, median PVC was approximately 2.4-fold greater for the CB group compared with the FF group (median: 53.17 vs 22.11; P < 0.01). There was a significantly lower level of S. sobrinus formation around the FF bracket system than there was surrounding the conventionally bonded group. This study suggests that the FF adhesive bracket system can help reduce the occurrence of bacterial growth around orthodontic brackets.

Antioxidant Activities of Cuminum cyminum Extracts and Their Antibacterial Effects against Some Dental Caries Pathogens

Background: The seeds of cumin (Cuminum cyminum L.) are widely used as the spice for their distinctive aroma, they are also commonly used in traditional medicine to treat a variety of diseases. Methods: The present study aimed to evaluate the antioxidant activities of cumin extracts and their antimicrobial effects against six oral pathogens isolated from dental caries and supragingival plaque. The extracts were obtained by maceration with acetone, ethanol and methanol at 70% (v/v). Result: The greatest content of polyphenols, flavonoids and tannins, was obtained with acetone (42±3.46 mg GAE/g DW), (24.49±1.24 mg EQ/g DW) and (34.95±8.71 mg EC/g DW) respectively. HPLC analysis performed to determine acetonic extract components revealed the presence of p-coumaric acid, diosmin as the most abundant compounds and several apigenins. Antioxidant activity of cumin extracts showed the greatest activity with the acetonic extract (940±42 µg/mL) followed very closely by the ethanolic extract (960±50 µg/mL). The agar well diffusion method has shown that all the extracts have an antimicrobial power against all the Gram+strains. The minimum inhibitory concentration values recorded by the studied extracts vary from 12.5 to 200 mg/mL. These findings suggest that cumin seed extracts might be effective as antibacterial agent against oral pathogens.

Inhibitory effects of Stevioside on Streptococcus mutans and Candida albicans dual-species biofilm.

Streptococcus mutans is the most prevalent biofilm-forming pathogen in dental caries, while Candida albicans is often detected in the presence of S. mutans. We aimed to evaluate the anti-caries effect of stevioside in medium trypticase soy broth (TSB) with or without sucrose supplementation compared with the same sweetness sucrose and xylitol in a dual-species model of S. mutans and C. albicans, based on planktonic growth, crystal violet assay, acid production, biofilm structural imaging, confocal laser scanning microscopy, and RNA sequencing. Our results showed that compared with sucrose, stevioside significantly inhibited planktonic growth and acid production, changed the structure of the mixed biofilm, and reduced the viability of biofilm and the production of extracellular polysaccharides in dual-species biofilm. Through RNA-seq, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway impact analysis showed that stevioside decreased sucrose metabolism and increased galactose and intracellular polysaccharide metabolism in S. mutans, and decreased genes related to GPI-modified proteins and secreted aspartyl proteinase (SAP) family in C. albicans. In contrast to xylitol, stevioside also inhibited the transformation of fungal morphology of C. albicans, which did not form mycelia and thus had reduced pathogenicity. Stevioside revealed a superior suppression of dual-species biofilm formation compared to sucrose and a similar anti-caries effect with xylitol. However, sucrose supplementation diminished the suppression of stevioside on S. mutans and C. albicans. Our study is the first to confirm that stevioside has anticariogenic effects on S. mutans and C. albicans in a dual-species biofilm. As a substitute for sucrose, it may help reduce the risk of developing dental caries.

Dysbiosis of Oral Microbiota and Metabolite Profiles Associated with Type 2 Diabetes Mellitus.

Several previous studies have shown that oral microbial disorders may be closely related to the occurrence and development of type 2 diabetes mellitus (T2DM). However, whether the function of oral microorganisms and their metabolites have changed in patients with T2DM who have not suffered from any oral diseases has not been reported. We performed metagenomic analyses and nontargeted metabolic analysis of saliva and supragingival plaque samples from patients with T2DM who have not suffered any oral diseases and normal controls. We found that periodontal pathogens such as Porphyromonas gingivalis and Prevotella melaninogenica were significantly enriched, while the abundances of dental caries pathogens such as Streptococcus mutans and Streptococcus sobrinus were not significantly different in patients with T2DM compared to those in normal controls. Metabolomic analyses showed that the salivary levels of cadaverine and L-(+)-leucine of patients with T2DM were significantly higher than those of normal controls, while the supragingival plaque levels of N-acetyldopamine and 3,4-dimethylbenzoic acid in patients with T2DM were significantly higher than those in the normal controls. Additionally, we identified the types of oral microorganisms related to the changes in the levels of circulating metabolites, and the oral microorganisms were involved in the dysregulation of harmful metabolites such as cadaverine and n, n-dimethylarginine. Overall, our study first described the changes in the composition of oral microorganisms and their metabolites in patients with T2DM who have not suffered any oral diseases, which will provide a direct basis for finding oral biomarkers for early warning of oral diseases in T2DM. IMPORTANCE The incidence of oral diseases in type 2 diabetic patients might increase, and the severity might also be more serious. At present, the relationship between oral microorganisms and type 2 diabetes mellitus (T2DM) has become a hot topic in systemic health research. However, whether the function of oral microorganisms and their metabolites have changed in patients with T2DM who have not suffered from any oral diseases has not been reported. We found that even if the oral condition of T2DM is healthy, their oral microbes and metabolites have changed, thus increasing the risk of periodontal disease. Our study first described the changes in the composition of oral microorganisms and their metabolites in T2DM who have not suffered any oral diseases and revealed the correlation between oral microorganisms and their metabolites, which will provide a direct basis for finding oral biomarkers for early warning of oral diseases in patients with T2DM.

Anticariogenic potential of tabernaemontana divaricata.

Many parts of Tabernaemontana divaricata (T. divaricata) including its leaf is used for the analgesic and antibacterial purpose by Adivasis of Kerala. To evaluate the antibacterial potential of T. divaricata against common caries pathogens like S. mutans and L. acidophilus. Research is done in Biogenix Research Lab, Thiruvananthapuram. Ethyl alcoholic extract of T. divaricata leaves is tested for its antibacterial action against common caries pathogens at various levels. It includes assessing the leaves' antibacterial activity, acid production of bacteria in the presence of the study sample, Minimum inhibitory concentration (MIC), minimum bacterial concentration (MBC) and colony forming units (CFU) levels in the presence of the leaf extract. In descriptive statistics, mean and standard deviation is used. Mann-Whitney U test, Independent Students T-test, Student Paired T-test, and One-way ANOVA followed by Turkeys Post hoc analysis are the tests used in inferential statistics. It is found that T. divaricata has substantial antibacterial action against S. mutans and L. acidophilus. Our indigenous plants have a lot of medicinal properties. T. divaricata is no exception to this, though it is commonly considered as a garden plant. In the current study, it has been proven that its leaves have antibacterial action against oral pathogens. So, the research has to be taken to a further level for its medicinal application.

Methods to Study Antagonistic Activities Among Oral Bacteria.

Most bacteria in nature exist in multispecies communities known as biofilms. In the natural habitat where resources (nutrient, space, etc.) are usually limited, individual species must compete or collaborate with other neighboring species in order to perpetuate in the multispecies community. The human oral cavity is colonized by >700 microbial species known as the indigenous microbiota. This indigenous flora normally maintains an ecological balance through antagonistic as well as mutualistic interspecies interactions. However, environmental perturbation may disrupt this balance, leading to overgrowth of pathogenic species which could in turn initiate diseases such as dental caries (tooth decay) and periodontitis (gum disease). Understanding the mechanisms of diversity maintenance may help developing novel approaches to manage these "polymicrobial diseases". In this chapter, we will focus on a well-characterized form of biochemical warfare: bacteriocins produced by Streptococcus mutans, a primary dental caries pathogen, and hydrogen peroxide (H2O2) produced by several oral commensal streptococci. We will describe detailed methodologies on the competition assay, isolation, purification, and characterization of bacteriocins.

Streptococcus mutans Associated with Endo-Periodontal Lesions in Intact Teeth

A massive periodontal destruction can affect the root canal (RC) system and potentially expose the pulpo-dentinal complex to opportunistic bacteria. Streptococcus mutans is a major pathogen of human caries and periodontal diseases, and its virulence mostly resides in the ability to adhere to collagen and form biofilms, due to collagen-binding proteins (CBPs) Cnm and Cbm. Seventeen patients affected by severe endo-periodontal lesions without caries and/or exposure of pulpal tissue were subjected to tooth extraction and samples for microbiological investigation were collected from the root surface (RS) and RC. The collected swabs were cultivated and subjected to the quantitative real-time PCR (qPCR) for the detection of S. mutans and to the PCR for the cnm/cbm genes investigation, followed by next-generation sequencing (NGS). S. mutans DNA was detected in 12/17 (70.5%) RS samples and in 8/17 (47.0%) RC samples. In the CBPs screening of positive samples, the cnm gene was detected in 4/12 (33.3%) RS and in 1/8 (12.5%) RC samples, whilst all the samples tested negative for the cbm gene. The presence of the cnm gene could enhance the local virulence of the pathogens. Therefore, S. mutans have to be included as potential periodontopathogen bacterium in severe or refractory forms of periodontal diseases.

Characterization of Leuconostoc mesenteroides MJM60376 as an oral probiotic and its antibiofilm activity.

Lactic acid bacteria have been widely used as probiotics for improving gut health. However, studies on oral probiotics were very limited. In this study, 67 lactic acid bacteria (LAB) were isolated from fermented food and screened for antagonistic activity against Streptococcus mutans, the causative pathogen of dental caries. Leuconostoc mesenteroides MJM60376 showed the highest antagonistic activity against S. mutans KCTC3065. L. mesenteroides MJM60376 also showed oral probiotic characteristics including weak acid production, lysozyme tolerance, adhesion to oral epithelial cell (YD-38), antibiotic susceptibility, and good coaggregation ability with S. mutans. Furthermore, the biofilm formation of S. mutans was significantly reduced when cocultured with L. mesenteroides. Scanning electron microscopy analysis showed that amounts of attached bacteria of S. mutans and network-like structures were significantly reduced by L. mesenteroides MJM60376. Cell-free supernatant (CFS) of L. mesenteroides MJM60376 also greatly inhibited biofilm formation of S. mutans from the adherent stage, the activity remained even after it was treated with catalase, trypsin, or pH neutralized. Expression levels of biofilm formation-related genes were significantly reduced in S. mutans when it was treated with the CFS of L. mesenteroides MJM60376. Therefore, L. mesenteroides MJM60376 has great potential to be used as a multifunctional ingredient.