Beyond Streptococcus mutans: dental caries onset linked to multiple species by 16S rRNA community analysis

Site-tropism of streptococci in the oral microbiome

A detailed understanding of where bacteria localize is necessary to advance microbial ecology and microbiome-based therapeutics. The site-specialist hypothesis predicts that most microbes in the human oral cavity have a primary habitat type within the mouth where they are most abundant. We asked whether this hypothesis accurately describes the distribution of the members of the genus Streptococcus, a clinically relevant taxon that dominates most oral sites. Prior analysis of 16S rRNA gene sequencing data indicated that some oral Streptococcus clades are site-specialists while others may be generalists. However, within complex microbial populations composed of numerous closely related species and strains, such as the oral streptococci, genome-scale analysis is necessary to provide the resolution to discriminate closely related taxa with distinct functional roles. Here, we assess whether individual species within this genus are specialists using publicly available genomic sequence data that provide species-level resolution. We chose a set of high-quality representative genomes for human oral Streptococcus species. Onto these genomes, we mapped shotgun metagenomic sequencing reads from supragingival plaque, tongue dorsum, and other sites in the oral cavity. We found that every abundant Streptococcus species in the healthy human oral cavity showed strong site-tropism and that even closely related species such as S. mitis, S. oralis, and S. infantis specialized in different sites. These findings indicate that closely related bacteria can have distinct habitat distributions in the absence of dispersal limitation and under similar environmental conditions and immune regimes. Substantial overlap between the core genes of these three species suggests that site-specialization is determined by subtle differences in genomic content.

Changes in oral pH before and after placing preformed metal crowns in primary dentition of Mexican children

BACKGROUND: Prefabricated metal crowns (PMCs) have been widely used in pediatric dentistry due to their great success in various clinical situations. However, it is important to know the local effects, such as changes in pH in the oral environment. OBJECTIVE: To evaluate the pH variations before and after placement of PMCs. METHODS: A quasi-experimental study (before and after) was performed with 32 pediatric patients who needed rehabilitation with PMCs at a pediatric dentistry clinic in a public university. Measurements were made using a pH potentiometer before PMC placement, one week after, and one month after placement. ANOVA and Pearson correlation were performed in SPSS. RESULTS: The average age of the participants was 5.9 ± 1.6 years, and 53.1% were female. The average pH before, one week after, and one month after crown placement was 7.46 ± 0.37, 7.00 ± 0.32, and 7.1 ± 0.19, respectively. Significant differences (p< 0.05) were observed between the three pH measurements. We found differences when comparing the basal pH values to those at one week (p= 0.001) and one month (p= 0.002). CONCLUSION: Although there were statistically significant differences in the pH change values before and after the placement of crowns, these differences may not have a clinical impact.

Streptococcus sobrinus as a Predominant Oral Bacteria Related to the Occurrence of Dental Caries in Polish Children at 12 Years Old

Dental caries is listed by the WHO as one of the major non-communicable diseases that need to be prevented and treated. The aim of the study was to evaluate the prevalence and severity of caries expressed as the Decayed, Missing and Filled Permanent Teeth (DMFT) index in 12-year-old Polish children and to verify bacterial species related to the occurrence of dental caries. Quantitative real-time PCR analysis of DNA isolated from saliva samples was performed to detect 8 cariogenic and periopathogenic bacterial strains. A total of 118 Polish children were enrolled in the study. They had low mean DMFT scores of 1.58 ± 1.98. The prevalence of dental caries in the children tested was low (53.4%), with a tendency to decrease compared to previous oral surveys. Bacterial abundance of other species in the dental caries and caries-free groups did not differ; however, periopathogenic Prevotella pallens, Fusobacterium nucleatum along with cariogenic Streptococcus mutans and Lactobacillus fermentum were significantly strongly correlated in the caries-active subjects. The prevalence of S. sobrinus was significantly higher in children with dental caries (p = 0.023) and correlated with higher DMFT. It may temporarily play an important role in the initiation of the cariogenic process or in its enhancement due to an ecological imbalance in dental microbiota.

A Co-Association of Streptococcus mutans and Veillonella parvula/dispar in Root Caries Patients and In Vitro Biofilms

Root caries in geriatric patients is a growing problem as more people are maintaining their natural teeth into advanced age. We determined the levels of various bacterial species previously implicated in root caries disease or health using quantitative real-time PCR in a pilot study of 7 patients with 1 to 4 root caries lesions per person. Levels of 12 different species on diseased roots compared to healthy (contralateral control) roots were measured. Four species were found at significantly higher levels on diseased roots (Streptococcus mutans, Veillonella parvula/dispar, Actinomyces naeslundii/viscosus, and Capnocytophaga granulosa) compared across all plaque samples. The level of colonization by these species varied dramatically (up to 1,000-fold) between patients, indicating different patients have different bacteria contributing to root caries disease. Neither of the two species previously reported to correlate with healthy roots (C. granulosa and Delftia acidovorans) showed statistically significant protective roles in our population, although D. acidovorans showed a trend toward higher levels on healthy teeth (P = 0.08). There was a significant positive correlation between higher levels of S. mutans and V. parvula/dispar on the same diseased teeth. In vitro mixed biofilm studies demonstrated that co-culturing S. mutans and V. parvula leads to a 50 to 150% increase in sucrose-dependent biofilm mass compared to S. mutans alone, depending on the growth conditions, while V. parvula alone did not form in vitro biofilms. The presence of V. parvula also decreased the acidification of S. mutans biofilms when grown in artificial saliva and enhanced the health of mixed biofilms.

Prevalence of Type IV Pili-Mediated Twitching Motility in Streptococcus sanguinis Strains and Its Impact on Biofilm Formation and Host Adherence

Type IV pili (Tfp) are known to mediate several biological activities, including surface-dependent twitching motility. Although a pil gene cluster for Tfp biosynthesis is found in all sequenced Streptococcus sanguinis strains, Tfp-mediated twitching motility is less commonly detected. Upon examining 81 clinical strains, 39 strains generated twitching zones on blood agar plates (BAP), while 27 strains displayed twitching on Todd-Hewitt (TH) agar. Although BAP appears to be more suitable for the development of twitching zones, 5 strains exhibited twitching motility only on TH agar, indicating that twitching motility is not only strain specific but also sensitive to growth media. Furthermore, different twitching phenotypes were observed in strains expressing comparable levels of pilT, encoding the retraction ATPase, suggesting that the twitching phenotype on agar plates is regulated by multiple factors. By using a PilT-null and a pilin protein-null derivative (CHW02) of twitching-active S. sanguinis CGMH010, we found that Tfp retraction was essential for biofilm stability. Further, biofilm growth was amplified in CHW02 in the absence of shearing force, indicating that S. sanguinis may utilize other ligands for biofilm formation in the absence of Tfp. Similar to SK36, Tfp from CGMH010 were required for colonization of host cells, but PilT only marginally affected adherence and only in the twitching-active strain. Taken together, the results suggest that Tfp participates in host cell adherence and that Tfp retraction facilitates biofilm stability. IMPORTANCE Although the gene clusters encoding Tfp are commonly present in Streptococcus sanguinis, not all strains express surface-dependent twitching motility on agar surfaces. Regardless of whether the Tfp could drive motility, Tfp can serve as a ligand for the colonization of host cells. Though many S. sanguinis strains lack twitching activity, motility can enhance biofilm stability in a twitching-active strain; thus, perhaps motility provides little or no advantage to the survival of bacteria within dental plaque. Rather, Tfp retraction could provide additional advantages for the bacteria to establish infections outside the oral cavity.

Functional signatures of ex-vivo dental caries onset

Background

The etiology of dental caries remains poorly understood. With the advent of next-generation sequencing, a number of studies have focused on the microbial ecology of the disease. However, taxonomic associations with caries have not been consistent. Researchers have also pursued function-centric studies of the caries microbial communities aiming to identify consistently conserved functional pathways. A major question is whether changes in microbiome are a cause or a consequence of the disease. Thus, there is a critical need to define conserved functional signatures at the onset of dental caries.

Methods

Since it is unethical to induce carious lesions clinically, we developed an innovative longitudinal ex-vivo model integrated with the advanced non-invasive multiphoton second harmonic generation bioimaging to spot the very early signs of dental caries, combined with 16S rRNA short amplicon sequencing and liquid chromatography-mass spectrometry-based targeted metabolomics.

Findings

For the first time, we induced longitudinally monitored caries lesions validated with the scanning electron microscope. Consequently, we spotted the caries onset and, associated with it, distinguished five differentiating metabolites - Lactate, Pyruvate, Dihydroxyacetone phosphate, Glyceraldehyde 3-phosphate (upregulated) and Fumarate (downregulated). Those metabolites co-occurred with certain bacterial taxa; Streptococcus, Veillonella, Actinomyces, Porphyromonas, Fusobacterium, and Granulicatella, regardless of the abundance of other taxa.

Interpretation

These findings are crucial for understanding the etiology and dynamics of dental caries, and devising targeted interventions to prevent disease progression.

Quorum Sensing and Quorum Quenching with a Focus on Cariogenic and Periodontopathic Oral Biofilms

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

Effect of Sodium Hypochlorite in Dental Unit Waterline on Aerosolized Bacteria-Generated from Endodontic Procedures

INTRODUCTION

Aerosol generation in a dental setting is a critical concern and approaches that aim at decreasing bacterial load in aerosols is of high priority for dental professionals. The objectives of this study were to evaluate the relative effect of various endodontic procedures on the generation and dissemination of aerosols and the effect of 0.1% sodium hypochlorite (NaOCl) in dental unit waterlines (DUWLs) on the bacterial load in the generated aerosols in a clinical setting.

METHODS

The study was completed in two phases. The classical passive sampling technique using brain heart infusion agar plates was utilized. Agar plates were strategically placed throughout the operatory at pre-defined locations.

PHASE I

To evaluate the effect of different endodontic procedures on generation and dissemination of aerosols, we collected a total of 38 samples. Following baseline collection, test samples were collected during vital pulp therapy (VPT) full pulpotomy (n=10), non-surgical root canal therapy (NSRCT; n=10), surgical root canal therapy (SRCT; n=10), and incision and drainage (I&D; n=8) procedures. Bacterial growth was expressed as colony-forming units at 48 hours post-sample collection. Data were analyzed using 1-way analysis of variance with Tukey's multiple comparisons post-hoc test.

PHASE II

To evaluate the effect of 0.1% NaOCl in DUWL on the bacterial load in the generated aerosols, a total of 30 samples were collected. All procedures including VPT (n=10), NSRCT (n=10), and SRCT (n=10) were performed with 0.1% NaOCl in DUWL. Bacterial growth was expressed as colony-forming units at 48 hours post-sample collection. Data were analyzed using 2-way analysis of variance with Tukey's multiple comparisons post-hoc test.

RESULTS

All endodontic procedures generated aerosols at all tested locations except I&D. Aerosols were disseminated as far as 3m from the patient's head with no significant difference between various locations (p>0.05). VPT procedures generated the maximum number of aerosols compared to NSRCT and SRCT. Adding 0.1% NaOCl to DUWLs significantly reduced the bacterial load in the generated aerosols in all treatment groups compared to groups treated with untreated waterlines (p<0.05). No significant difference was noted in the bacterial load between all groups with treated waterlines (p>0.05).

CONCLUSIONS

All tested endodontic procedures led to the generation and dissemination of contaminated aerosols, and the addition of 0.1% NaOCl as a biocide to the DUWL led to a statistically significant reduction in the bacterial load.

Does high sugar intake really alter the oral microbiota?: A systematic review

OBJECTIVES

Diet is one of the main factors influencing the diversity and interactions of the oral microbiota. The purpose of this study is to determine the impact of sugar intake on the microbial diversity and bacteria that predominate under these conditions.

MATERIAL AND METHODS

A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guide, using the PubMed, Scopus, and Science Direct databases and combinations of the words "microbiota," "microbiology," "bacteria," "sugars," "dysbiosis," "caries," "microbiome," "oral microbial," and "oral microbiota profile pattern." The selection criteria included year, language, type of publication, comparison of microbiota during low and high sugar intake, and bacterial identification by molecular sequencing of the 16S subunit of ribosomal RNA.

RESULTS

Out of a total of 374 papers that came up after the initial search, 8 met the criteria for this review. The papers included research on populations comprising children, young adults, and adults, with most of the studies reporting selection criteria for the participants and using validated instruments to determine sugar intake. Apart from one study, all others reported for high sugar intake conditions a significant decrease in microbial diversity of the oral microbiome and the predominance of several bacterial genera or species, including Streptococcus, Scardovia, Veillonella, Rothia, Actinomyces, and Lactobacillus.

CONCLUSIONS

Sugar-rich diets have a significantly unfavorable effect on the diversity and balance of oral microbiota; however, further studies are required to determine the exact role of sugar in microbial interactions.

Oral Microbiota, Its Equilibrium and Implications in the Pathophysiology of Human Diseases: A Systematic Review

Imbalances of the oral microbiota and dysbiosis have traditionally been linked to the occurrence of teeth and oral diseases. However, recent findings indicate that this microbiota exerts relevant influence in systemic health. Dysbiosis of the oral microbiota is implicated in the apparition and progression of cardiovascular, neurodegenerative and other major human diseases. In fact, the oral microbiota are the second most diverse and largely populated microbiota of the human body and its relationships with systemic health, although widely explored, they still lack of proper integration. The purpose of this systematic review is thus to widely examine the implications of oral microbiota in oral, cardiovascular and neurodegenerative diseases to offer integrative and up-to-date interpretations. To achieve that aim, we identified a total of 121 studies curated in PUBMED from the time interval January 2003–April 2022, which after careful screening resulted in 79 studies included. The reviewed scientific literature provides plausible vias of implication of dysbiotic oral microbiota in systemic human diseases, and encourages further research to continue elucidating the highly relevant and still poorly understood implications of this niche microbiota in systemic health. PROSPERO Registration Number: CRD42022299692. This systematic review follows relevant PRISMA guidelines.

Update of the list of QPS-recommended microbiological agents intentionally added to food or feed as notified to EFSA 16: suitability of taxonomic units notified to EFSA until March 2022

The qualified presumption of safety (QPS) approach was developed to provide a regularly updated generic pre‐evaluation of the safety of microorganisms, intended for use in the food or feed chains, to support the work of EFSA's Scientific Panels. The QPS approach is based on an assessment of published data for each agent, with respect to its taxonomic identity, the body of relevant knowledge, safety concerns and occurrence of antimicrobial resistance. Safety concerns identified for a taxonomic unit (TU) are, where possible, confirmed at the species/strain or product level and reflected by ‘qualifications’. In the period covered by this statement, no new information was found that would change the status of previously recommended QPS TUs. Of the 50 microorganisms notified to EFSA in October 2021 to March 2022 (inclusive), 41 were not evaluated: 10 filamentous fungi, 1 Enterococcus faecium, 1 Clostridium butyricum, 3 Escherichia coli and 1 Streptomyces spp. because are excluded from QPS evaluation, and 25 TUs that have already a QPS status. Nine notifications, corresponding to seven TUs were evaluated: four of these, Streptococcus salivarius, Companilactobacillus formosensis, Pseudonocardia autotrophica and Papiliotrema terrestris, being evaluated for the first time. The other three, Microbacterium foliorum, Pseudomonas fluorescens and Ensifer adhaerens were re‐assessed. None of these TUs were recommended for QPS status: Ensifer adhaerens, Microbacterium foliorum, Companilactobacillus formosensis and Papiliotrema terrestris due to a limited body of knowledge, Streptococcus salivarius due to its ability to cause bacteraemia and systemic infection that results in a variety of morbidities, Pseudonocardia autotrophica due to lack of body of knowledge and uncertainty on the safety of biologically active compounds which can be produced, and Pseudomonas fluorescens due to possible safety concerns.

Current State and Challenges of the Global Outcomes of Dental Caries Research in the Meta-Omics Era

Despite significant healthcare advances in the 21st century, the exact etiology of dental caries remains unsolved. The past two decades have witnessed a tremendous growth in our understanding of dental caries amid the advent of revolutionary omics technologies. Accordingly, a consensus has been reached that dental caries is a community-scale metabolic disorder, and its etiology is beyond a single causative organism. This conclusion was based on a variety of microbiome studies following the flow of information along the central dogma of biology from genomic data to the end products of metabolism. These studies were facilitated by the unprecedented growth of the next- generation sequencing tools and omics techniques, such as metagenomics and metatranscriptomics, to estimate the community composition of oral microbiome and its functional potential. Furthermore, the rapidly evolving proteomics and metabolomics platforms, including nuclear magnetic resonance spectroscopy and/or mass spectrometry coupled with chromatography, have enabled precise quantification of the translational outcomes. Although the majority supports ‘conserved functional changes’ as indicators of dysbiosis, it remains unclear how caries dynamics impact the microbiota functions and vice versa, over the course of disease onset and progression. What compounds the situation is the host-microbiota crosstalk. Genome-wide association studies have been undertaken to elucidate the interaction of host genetic variation with the microbiome. However, these studies are challenged by the complex interaction of host genetics and environmental factors. All these complementary approaches need to be orchestrated to capture the key players in this multifactorial disease. Herein, we critically review the milestones in caries research focusing on the state-of-art singular and integrative omics studies, supplemented with a bibliographic network analysis to address the oral microbiome, the host factors, and their interactions. Additionally, we highlight gaps in the dental literature and shed light on critical future research questions and study designs that could unravel the complexities of dental caries, the most globally widespread disease.

Lactobacilli and human dental caries: more than mechanical retention

Lactobacilli have been considered as major contributors to human dental caries for over a century. Recent in vitro model studies have shown that when compared to Streptococcus mutans, a keystone pathogen of human dental caries, the ability of lactobacilli to form biofilms is poor, although differences exist between the different major species. Further studies using molecular and bioinformatics approaches provide evidence that multiple mechanisms, including adhesin-receptor mediated physical contact with S. mutans, facilitate the adherence and establishment of lactobacilli on the tooth surface. There is also evidence that under conditions like continuous sugar consumption, weak acids and other antimicrobials such as bacteriocins from lactobacilli can become detrimental to the microbial community, especially those in the proximity. Details on the underlying mechanisms of how different Lactobacillus sp. establish and persist in the highly complex microbiota on the tooth surface await further investigation.

Salivary microbiome differences in prepubertal children with and without adrenal androgen excess

BACKGROUND

Premature adrenarche is a condition of childhood adrenal androgen excess (AAE) in the absence of gonadotropin-dependent puberty, and has been linked to insulin resistance and progression to metabolic syndrome. Microbial dysbiosis is associated with progression of inflammatory states and chronic diseases. Here, we aimed to examine the salivary microbiomes of children with AAE and assess the relationship with adrenal androgens and metabolic parameters.

METHODS

In a prospective cross-sectional study of children with AAE and healthy controls, adrenal and metabolic parameters were characterized and salivary microbiome was profiled using V3-V4 16S rDNA gene amplicon sequencing.

RESULTS

There was increased α-diversity in AAE (5 M, 15 F) compared to controls (3 M, 8 F), with positive correlation of 11OHA4, 11KA4, testosterone, androstenedione, DHEA, and DHEAS. Subanalyses showed increased α-diversity in both overweight/obese AAE and normal weight AAE compared to normal weight controls. Genus Peptostreptococcus, Veillonella, and Streptococcus salivarius were increased in normal weight AAE. Genus Prevotella, Abiotrophia, and Neisseria were increased in overweight/obese AAE.

CONCLUSION

These pilot data demonstrate differences in salivary microbiome profiles of children with and without AAE. Further studies are needed to assess the causal relationships between adrenal androgens, metabolic dysfunction, and salivary microbiome composition.

IMPACT

This study is the first to report the salivary microbiome of prepubertal children with adrenal androgen excess (AAE). α-Diversity is increased in the salivary microbiome of children with AAE independent of weight status, and in this study cohort several serum androgens are positively associated with α-diversity. Several taxa that have been associated with periodontal disease and inflammation are found to be significantly increased in AAE.

Tooth-Specific Streptococcus mutans Distribution and Associated Microbiome

Dental caries is multifactorial and polymicrobial in nature and remains one of the most common oral diseases. While caries research has focused on Streptococcus mutans as the main etiological pathogen, its impact at the tooth level is not fully understood. In this cross-sectional study, the levels and distribution of S. mutans in the posterior teeth at different dentition stages were investigated along with the corresponding tooth-specific microbiome. Occlusal plaque samples of 87 individual posterior teeth were collected from thirty children in three dentition stages (primary, mixed, and permanent). The S. mutans levels in the occlusal plaque of individual posterior teeth were quantified with qPCR, and those with preferential colonization were selected for tooth-specific microbiome analysis using 16S rRNA sequencing. Results: Quantification of S. mutans levels in the occlusal plaque confirmed the preferential colonization on the first primary and permanent molars. These teeth were selected for further tooth-specific microbiome sequencing, as they also displayed high caries experience. There were significant differences in the relative abundance of the four most abundant genera: Neisseria, Streptococcus, Rothia, and Veillonella. Furthermore, the tooth-level caries experience was correlated with a reduction in the microbiome diversity. Analyzing the different tooth-associated microbial communities, distinct tooth-specific core microbiomes were identified. Conclusions: Our findings suggest that caries susceptibility at the tooth level, depending on tooth type and dentition stage, is influenced by individual species as well as plaque community.

Taxonomic and functional alterations in the salivary microbiota of children with and without severe early childhood caries (S-ECC) at the age of 3

Background

Primary dental caries is the most prevalent oral disease among preschool children, which can cause severe damage to teeth and even affect the mental well-being of children. Various studies have demonstrated that the oral microbiome plays a pivotal role in the onset and development of dental caries. However, it remains uncertain about the key microbial markers associated with caries, owing to the limited evidence.

Methods

Fifteen S-ECC children and fifteen healthy controls were selected from three-year-old children in this study. Their clinical data and oral saliva samples were collected. Shotgun sequencing was conducted to investigate the microbial differences and the relevant functions between the two groups.

Results

We observed no apparent difference in oral microbial community diversity between the two groups. Still, at the genus/species levels, several characteristic genera/species such as Propionibacterium, Propionibacterium acidifaciens, Prevotella denticola, Streptococcus mutans and Actinomyces sp. oral taxon 448/414 increased significantly in S-ECC children, compared with the oral health group. Furthermore, we found that functional pathways involving glycolysis and acid production, such as starch and sucrose metabolism, fructose and mannose metabolism, glycolysis/gluconeogenesis, were prominently up-regulated in the high-caries group.

Conclusions

Our study showed that dental caries in children were associated with the alterations in the oral microbiota at the composition and functional levels, which may potentially inspire the exploration of microbial diagnosis or therapeutic treatments.

Molecular Detection of Streptococcus downii sp. nov. from Dental Plaque Samples from Patients with Down Syndrome and Non-Syndromic Individuals

A new bacterial species has recently been identified in the dental plaque of an adolescent with Down syndrome. The species is known as Streptococcus downii sp. nov. (abbreviated to S. downii), and it inhibits the growth of S. mutans and certain periodontal pathogens. The aim of this study was to determine the distribution of S. downii in the oral cavity of individuals with Down syndrome. Methods: A specific polymerase chain reaction for the operon of bacteriocin (class IIb lactobin A/cerein 7B family) was designed to detect S. downii in individuals with Down syndrome (n = 200) and in the general population (n = 100). We also compared the whole genome of S. downii and the regions related to its bacteriocins against 127 metagenomes of supragingival plaque of the “Human Microbiome Project”. Results: We detected the specific gene of the S. downii bacteriocin in an individual with Down syndrome (Cq, 34.52; GE/μL, 13.0) and in an individual of the non-syndromic control group (Cq, 34.78 Cq; GE/μL, 4.93). The prevalence of S. downii was ≤1% both in Down syndrome and in the general population, which did not allow for clinical-microbiological correlations to be established. This result was confirmed by detecting only one metagenome with an ANIm with approximately 95% homology and with 100% homology with ORFs that code class IIb lactobiocin A/cerein 7B bacteriocins among the 127 metagenomes of the “Human Microbiome Project” tested. Conclusions: The detection rate of S. downii in the supragingival dental plaque was very low, both in the Down syndrome individuals and in the non-syndromic controls. A clinical-microbiological correlation could therefore not be established.

Multimodal Data Integration Reveals Mode of Delivery and Snack Consumption Outrank Salivary Microbiome in Association With Caries Outcome in Thai Children

Early childhood caries (ECC) is not only the most common chronic childhood disease but also disproportionately affects underserved populations. Of those, children living in Thailand have been found to have high rates of ECC and severe ECC. Frequently, the cause of ECC is blamed on a handful of cariogenic organisms, such as Streptococcus mutans and Streptococcus sobrinus. However, ECC is a multifactorial disease that results from an ecological shift in the oral cavity from a neutral pH (~7.5) to an acidic pH (&lt;5.5) environment influenced by the host individual’s biological, socio-behavioral, and lifestyle factors. Currently, there is a lack of understanding of how risk factors at various levels influence the oral health of children at risk. We applied a statistical machine learning approach for multimodal data integration (parallel and hierarchical) to identify caries-related multiplatform factors in a large cohort of mother-child dyads living in Chiang Mai, Thailand (N=177). Whole saliva (1 mL) was collected from each individual for DNA extraction and 16S rRNA sequencing. A set of maternal and early childhood factors were included in the data analysis. Significantly, vaginal delivery, preterm birth, and frequent sugary snacking were found to increase the risk for ECC. The salivary microbial diversity was significantly different in children with ECC or without ECC. Results of linear discriminant analysis effect size (LEfSe) analysis of the microbial community demonstrated that S. mutans, Prevotella histicola, and Leptotrichia hongkongensis were significantly enriched in ECC children. Whereas Fusobacterium periodonticum was less abundant among caries-free children, suggesting its potential to be a candidate biomarker for good oral health. Based on the multimodal data integration and statistical machine learning models, the study revealed that the mode of delivery and snack consumption outrank salivary microbiome in predicting ECC in Thai children. The biological and behavioral factors may play significant roles in the microbial pathobiology of ECC and warrant further investigation.

Mechanistic Effects of E-Liquids on Biofilm Formation and Growth of Oral Commensal Streptococcal Communities: Effect of Flavoring Agents

Background: Vaping has become a global health concern. As research continues, more studies are beginning to question the relative safety of E-liquid flavoring additives. The oral cavity is the first site of exposure to E-liquid aerosol, making it critical for investigation. Because of the importance of commensal bacterial biofilms for oral health, we sought to explore the effects of E-liquids ± flavors on the formation and growth of single- and multi-species biofilms and to investigate the mechanism of inhibition. Methods: Quantitative and confocal biofilm analysis, death curves, and colony-forming units (CFU) were evaluated with flavorless and flavored (tobacco, menthol, cinnamon, strawberry, blueberry) E-liquids using four strains of oral commensal bacteria (Streptococcus gordonii, Streptococcus intermedius, Streptococcus mitis, and Streptococcus oralis). Results: All flavoring agents show a dose-dependent inhibition in the growth of single-species and multi-species biofilms. Furthermore, CFUs, death curves, and light microscopy show that flavoring agents have a bactericidal mode of inhibition on the growth of these oral streptococci. Conclusions: These results show that flavored, rather than unflavored, E-liquids are more detrimental to biofilm formation and growth of oral commensal bacteria. Consequently, E-liquid flavorings agents could pose risks to the oral microenvironment, and by extension, to systemic health.

Phytochemical Profile of Antibacterial Agents from Red Betel Leaf (Piper crocatum Ruiz and Pav) against Bacteria in Dental Caries

Based on data from The Global Burden of Disease Study in 2016, dental and oral health problems, especially dental caries, are a disease experienced by almost half of the world’s population (3.58 billion people). One of the main causes of dental caries is the pathogenesis of Streptococcus mutans. Prevention can be achieved by controlling S. mutans using an antibacterial agent. The most commonly used antibacterial for the treatment of dental caries is chlorhexidine. However, long-term use of chlorhexidine has been reported to cause resistance and some side effects. Therefore, the discovery of a natural antibacterial agent is an urgent need. A natural antibacterial agent that can be used are herbal medicines derived from medicinal plants. Piper crocatum Ruiz and Pav has the potential to be used as a natural antibacterial agent for treating dental and oral health problems. Several studies reported that the leaves of P. crocatum Ruiz and Pav contain secondary metabolites such as essential oils, flavonoids, alkaloids, terpenoids, tannins, and phenolic compounds that are active against S. mutans. This review summarizes some information about P. crocatum Ruiz and Pav, various isolation methods, bioactivity, S. mutans bacteria that cause dental caries, biofilm formation mechanism, antibacterial properties, and the antibacterial mechanism of secondary metabolites in P. crocatum Ruiz and Pav.

Oral Microbiota during Childhood and Its Role in Chemotherapy-Induced Oral Mucositis in Children with Cancer

The human oral cavity harbors the second most abundant microbiota after the gastrointestinal tract, with over 700 species currently identified in the oral microflora. The oral microbiota develops from intrauterine life and after birth is continuously shaped by several influencing factors. The perturbation of the diversity and proportions of species within the oral microbiota leads to dysbiosis and associated increased risk of local and systemic diseases. In children who receive chemotherapy for cancer, oral mucositis is a common and painful side effect that decreases quality of life (QoL) and treatment adherence. The oral microbiota undergoes a substantial dysbiosis as an effect of cancer and its treatment, characterized by lower richness and less diversity. Furthermore, this dysbiosis seems to promote pro-inflammatory cytokine release and pro-apoptotic mediators, enhancing the oral tissue damage. Further studies on the role of the oral microbiota in the pathogenesis of oral mucositis should be performed among children with cancer who receive chemotherapy, to find preventive and protective factors against the pathogenesis of oral mucositis.

Evaluation of the Antibacterial Effects of Four Different Adhesives Against Three Bacterial Species in Two Time Periods: An In Vitro Comparative Study

Aim:

The study aimed at evaluating the antibacterial activities of four adhesive systems against three bacterial species in two time periods.

Material and Method:

Four different antibacterial adhesive materials, a nonantibacterial adhesive (Clearfil SE Bond), and a vancomycin-impregnated antibiogram disc were used in the study. The antibacterial activities of Gluma 2 Bond, Clearfil SE Protect Bond (CPB) Primer, FL Bond II (FLB), and Peak Universal Bond (PUB) on Enterococcus faecalis, Streptococcus mutans, and Lactobacillus acidophilus were evaluated by the disc diffusion method. Antibiogram discs onto which the adhesive agent was dripped were placed on agar plates at intervals. Inhibition zone diameters around the discs, which were incubated, were measured. Statistical analysis was done with the one-way analysis of variance.

Results:

As a result of our study, it was concluded that the CPB Primer was the agent with the highest antibacterial activity, including the control group. One of the remarkable findings in our study was that CPB Primer showed the most significant effect against Streptococcus mutans among microorganisms. Although not statistically significant, the antibacterial effect of adhesive agents at the end of the 48th h was found to be higher than at the end of the 24th h ( P > .05).

Conclusion:

The strong antibacterial activity of the CPB Primer on all three bacteria suggests that it is a preferable adhesive agent in deep dentinal caries as well as in initial caries lesions.

Candida albicans and Early Childhood Caries

Early childhood caries (ECC) is a highly prevalent and costly chronic oral infectious disease in preschool children. Candida albicans has been frequently detected in children and has demonstrated cariogenic traits. However, since ECC is a multifactorial infectious disease with many predisposing non-microbial factors, it remains to be elucidated whether the presence and accumulation of C. albicans in ECC is merely a consequence of the adaptation of C. albicans to a cariogenic oral environment, or it plays an active role in the initiation and progression of dental caries. This review aims to summarize the current knowledge on C. albicans and the risk of ECC, with a focus on its synergistic relationship with the cariogenic pathogen Streptococcus mutans. We also highlight recent advances in the development of approaches to disrupt C. albicans-S. mutans cross-kingdom biofilms in ECC prevention and treatment. Longitudinal clinical studies, including interventional clinical trials targeting C. albicans, are necessary to ascertain if C. albicans indeed contributes in a significant manner to the initiation and progression of ECC. In addition, further work is needed to understand the influence of other bacteria and fungi of oral microbiota on C. albicans-S. mutans interactions in ECC.

Testing of candidate probiotics to prevent dental caries induced by Streptococcus mutans in a mouse model

AIMS

We evaluated two species of human oral commensal streptococci in protection against dental caries induced by Streptococcus mutans.

METHODS AND RESULTS

Candidate probiotics, Streptococcus sp. A12, Streptococcus sanguinis BCC23 and an arginine deiminase mutant of BCC23 (∆arcADS) were tested for their ability to reduce S. mutans-induced caries in an established mouse model. Mice were colonized with a probiotic, challenged with S. mutans, then intermittently reinoculated with a probiotic strain. Oral colonization of each strain and autochthonous bacteria was assessed by qPCR. Both BCC23 strains, but not A12, were associated with markedly reduced sulcal caries, persistently colonized mucosal and dental biofilms, and significantly lowered S. mutans counts. All three strains enhanced mucosal colonization of autochthonous bacteria. In a follow-up experiment, when S. mutans was established first, dental and mucosal colonization of S. mutans was unaltered by a subsequent challenge with either BCC23 strain. Results between BCC23 and BCC23 ∆arcADS were equivalent.

CONCLUSIONS

BCC23 is a potential probiotic to treat patients at high caries risk. Its effectiveness is independent of ADS activity, but initial dental cleaning to enhance establishment in dental biofilms may be required.

SIGNIFICANCE AND IMPACT OF THE STUDY

In vivo testing of candidate probiotics is highly informative, as effectiveness is not always reflected by genotype or in vitro behaviors.

Streptococcus mutans-associated bacteria in dental plaque of severe early childhood caries

Background

Streptococcus mutans (S. mutans) is a potential pathogenic bacteria of dental caries. However, the level of S. mutans is low in some children with severe early childhood caries (SECC)

Aim

To evaluate the effect of S. mutans level on dental microbiome and cariogenesis.

Methods

The oral microbiota was compared between caries-free group (CF) and SECC group.16S rRNA gene sequencing was used for S. mutans level bacterial community analysis. The candidate bacteria that were closely related with S. mutans abundance were identified and confirmed by absolute quantitative real-time PCR in clinical dental plaque samples from CF and SECC groups.

Results

Through in-depth analysis of dental plaque microorganism, Leptotrichia, Selenomonas and Prevotella_7 were found in the S. mutans-low group (p < 0.05) and Porphyromonas, Selenomonas_3 were found in the S. mutans-high group (p < 0.05). Through quantitative real-time PCR, Leptotrichia, Selenomonas and Prevotella_7 were identified as the potential biomarkers of SECC when S. mutans was at a low level.

Conclusion

Leptotrichia, Selenomonas and Prevotella_7 are identified as potential biomarkers in SECC with a low abundance or without S. mutans. Our study may shed light on the understanding of caries occurrence in SECC with low abundance of S. mutans.

Abbreviations

S. mutans, Streptococcus mutans; CF, caries-free; SECC, severe early childhood caries; ECC, early childhood caries; rRNA, ribosome RNA; qPCR, Quantitative real-time PCR; OTUs, operational taxonomic units; ANOVA, analysis of variance; LDA, Linear discriminant analysis; LEfSe, Linear discriminant analysis effect size; COG, Groups of proteins; NMDS, Non-MetricMulti-Dimensional Scaling; IL-1β, interleukin −1β; IL-6, interleukin-6; IL-8, interleukin-8; IL-10, interleukin-10.

Site- and Time-Dependent Compositional Shifts in Oral Microbiota Communities

Objectives

The oral microbiota plays a significant role in oral health. The present study aims to characterize variations in the oral microbiota relative to the collection site, the dynamics of biofilm accumulation, and inherent inter-individual differences.

Methods

Whole stimulated saliva and tooth biofilm samples from the 16 defined tooth regions were collected after 1, 2, or 3 days without oral hygiene (accumulation time) in six healthy adults with no signs of active caries or periodontal disease. The routines and conditions before and between sample collections were carefully standardized. Genomic DNA was extracted, and the V3-V4 regions of the 16S rRNA gene were amplified by PCR and sequenced on an Illumina MiSeq platform. Sequences were quality controlled, amplicon sequence variants (ASVs) were clustered, and taxonomic allocation was performed against the expanded Human Oral Microbiome Database (eHOMD). Microbial community profiles were analyzed by multivariate modeling and a linear discriminant analysis (LDA) effect size (LEfSe) method.

Results

The overall species profile in saliva and tooth biofilm differed between participants, as well as sample type, with a significantly higher diversity in tooth biofilm samples than saliva. On average, 45% of the detected species were shared between the two sample types. The microbiota profile changed from the most anterior to the most posterior tooth regions regardless of whether sampling was done after 1, 2, or 3 days without oral hygiene. Increasing accumulation time led to higher numbers of detected species in both the saliva and region-specific tooth biofilm niches.

Conclusion

The present study confirms that the differences between individuals dominate over sample type and the time abstaining from oral hygiene for oral microbiota shaping. Therefore, a standardized accumulation time may be less important for some research questions aiming at separating individuals. Furthermore, the amount of DNA is sufficient if at least two teeth are sampled for microbiota characterization, which allows a site-specific characterization of, for example, caries or periodontitis.

Diversity of site-specific microbes of occlusal and proximal lesions in severe- early childhood caries (S-ECC)

Background

Severe-early childhood caries (S-ECC) a global problem of significant concern, commonly manifest on the occlusal, and proximal surfaces of affected teeth. Despite the major ecological differences between these two niches the compositional differences, if any, in the microbiota of such lesions is unknown.

Methods

Deep-dentine caries samples from asymptomatic primary molars of children with S-ECC (n 19) belonging to caries-code 5/6, (ICDAS classification) were evaluated. Employing two primer pools, we amplified and compared the bacterial 16S rRNA gene sequences of the seven hypervariable regions (V2—V4 and V6—V9) using NGS-based assay.

Results

Bray-Curtisevaluation indicated that occlusal lesions (OL) had a more homogeneous community than the proximal lesions (PL) with significant compositional differences at the species level (p = 0.01; R- 0.513). Together, the occlusal and proximal niches harbored 263 species, of which 202 (76.8%) species were common to both , while 49 (18.6%) and 12 (4.6%) disparate species were exclusively isolated from the proximal and occlusal niches, respectively. The most commonl genera at both niches included Streptococcus, Prevotella, and Lactobacillus. S. mutans was predominant in PL (p ≤ 0.05), and Atopobium parvulum (p = 0.01) was predominant in OL.

Conclusions

Distinct differences exist between the caries microbiota of occlusal and proximal caries in S-ECC.

Metataxonomic and metabolomic evidence of biofilm homeostasis disruption related to caries: an in vitro study

The ecological dysbiosis of a biofilm includes not only bacterial changes but also changes in their metabolism. Related to oral biofilms, changes in metabolic activity are crucial endpoint, linked directly to the pathogenicity of oral diseases. Despite the advances in caries research, detailed microbial and metabolomic etiology is yet to be fully clarified. To advance this knowledge, a meta‐taxonomic approach based on 16S rRNA gene sequencing and an untargeted metabolomic approach based on an ultra‐high performance liquid chromatography‐quadrupole time‐of‐flight mass spectrometry analysis (UHPLC/Q‐TOF‐MS) were conducted. To this end, an in vitro biofilm model derived from the saliva of healthy participants were developed, under commensal and cariogenic conditions by adding sucrose as the disease trigger. The cariogenic biofilms showed a significant increase of Firmicutes phyla (p = 0.019), due to the significant increase in the genus Streptococcus (p = 0.010), and Fusobacter (p < 0.001), by increase Fusobacterium (p < 0.001) and Sphingomonas (p = 0.024), while suffered a decrease in Actinobacteria (p < 0.001). As a consequence of the shift in microbiota composition, significant extracellular metabolomics changes were detected, showed 59 metabolites of the 120 identified significantly different in terms of relative abundance between the cariogenic/commensal biofilms (Rate of change > 2 and FDR < 0.05). Forty‐two metabolites were significantly higher in abundance in the cariogenic biofilms, whereas 17 metabolites were associated significantly with the commensal biofilms, principally related protein metabolism, with peptides and amino acids as protagonists, latter represented by histidine, arginine, l‐methionine, glutamic acid, and phenylalanine derivatives.

Veillonellae: Beyond Bridging Species in Oral Biofilm Ecology

The genus Veillonella comprises 16 characterized species, among which eight are commonly found in the human oral cavity. The high abundance of Veillonella species in the microbiome of both supra- and sub-gingival biofilms, and their interdependent relationship with a multitude of other bacterial species, suggest veillonellae to play an important role in oral biofilm ecology. Development of oral biofilms relies on an incremental coaggregation process between early, bridging and later bacterial colonizers, ultimately forming multispecies communities. As early colonizer and bridging species, veillonellae are critical in guiding the development of multispecies communities in the human oral microenvironment. Their ability to establish mutualistic relationships with other members of the oral microbiome has emerged as a crucial factor that may contribute to health equilibrium. Here, we review the general characteristics, taxonomy, physiology, genomic and genetics of veillonellae, as well as their bridging role in the development of oral biofilms. We further discuss the role of Veillonella spp. as potential “accessory pathogens” in the human oral cavity, capable of supporting colonization by other, more pathogenic species. The relationship between Veillonella spp. and dental caries, periodontitis, and peri-implantitis is also recapitulated in this review. We finally highlight areas of future research required to better understand the intergeneric signaling employed by veillonellae during their bridging activities and interspecies mutualism. With the recent discoveries of large species and strain-specific variation within the genus in biological and virulence characteristics, the study of Veillonella as an example of highly adaptive microorganisms that indirectly participates in dysbiosis holds great promise for broadening our understanding of polymicrobial disease pathogenesis.

The Impact of Mouthwash on the Oropharyngeal Microbiota of Men Who Have Sex with Men: a Substudy of the OMEGA Trial

Mouthwash is a commonly used product and has been proposed as an alternative intervention to prevent gonorrhea transmission. However, the long-term effects of mouthwash on the oral microbiota are largely unknown. We investigated the impact of 12 weeks of daily mouthwash use on the oropharyngeal microbiota in a subset of men who have sex with men who participated in a randomized trial comparing the efficacy of two alcohol-free mouthwashes for the prevention of gonorrhea. We characterized the oropharyngeal microbiota using 16S rRNA gene sequencing of tonsillar fossae samples collected before and after 12 weeks of daily use of Listerine mouthwash or Biotène dry mouth oral rinse. Permutational multivariate analysis of variance (PERMANOVA) was used to assess differences in oropharyngeal microbiota composition following mouthwash use. Differential abundance testing was performed using ALDEx2, with false-discovery rate correction. A total of 306 samples from 153 men were analyzed (Listerine, n = 78 and Biotène, n = 75). There was no difference in the overall structure of the oropharyngeal microbiota following Listerine or Biotène use (PERMANOVA P = 0.413 and P = 0.331, respectively). Although no bacterial taxa were significantly differentially abundant following Listerine use, we observed a small but significant decrease in the abundance of both Streptococcus and Leptotrichia following Biotène use. Overall, our findings suggest that daily use of antiseptic mouthwash has minimal long-term effects on the composition of the oropharyngeal microbiota.

IMPORTANCE Given the role of the oral microbiota in human health, it is important to understand if and how external factors influence its composition. Mouthwash use is common in some populations, and the use of antiseptic mouthwash has been proposed as an alternative intervention to prevent gonorrhea transmission. However, the long-term effect of mouthwash use on the oral microbiota composition is largely unknown. We found that daily use of two different commercially available mouthwashes had limited long-term effects on the composition of the oropharyngeal microbiota over a 12-week period. The results from our study and prior studies highlight that different mouthwashes may differentially affect the oral microbiome composition and that further studies are needed to determine if mouthwash use induces short-term changes to the oral microbiota that may have detrimental effects.

Increasing risk factors of non-alcoholic fatty liver disease, a look into chronic periodontitis and insulin resistance

Non-alcoholic fatty liver disease (NAFLD) is marked by the excessive intrusion of triglycerides into hepatocytes without any role of alcohol consumption. Various risk factors have been attributed to this disease pathogenesis which involves metabolic disorders, immune response, and even an intricate relationship between the two. The role of insulin resistance (IR) in NAFLD has long been known; however, the molecular basis of disease progression under this metabolic backdrop is still being investigated. Similarly, the periodontitis-mediated immune response is another major factor involved in NAFLD manifestation which has generated huge interest. The prevalence of pathogenic bacteria elicits a strong immune response which according to studies shows a strong correlation with NAFLD state. Such pre-existing conditions have a strong probability of explaining the disease onset. Additionally, increasing reports of inflammatory response and its links to insulin resistance have further increased the scope of understanding NAFLD. Through this review, we aim to elaborate on these factors explaining their role in the disease progression.

Predominance of non-Streptococcus mutans bacteria in dental biofilm and its relation to caries progression

This study aims to assess differences in biofilm bacterial composition between patients with low and high caries. Patients without a medical problem and with no history of antibiotic use, mouth wash or fluoride application in the previous 3 months were recruited. Caries was recorded at cavitation level; score was calculated by a national mean (dmft of 4.8 and DMFT of 2.7). Pooled biofilm samples were collected from mesial, distal, buccal, lingual, and occlusal surfaces. Based on caries experience, individuals were classified into low and high caries and both groups were compared regarding bacteria identified using 16S rRNA gene sequencing, and molecular phylogenetic analysis of the isolates was performed. A total of twenty seven randomly selected samples with low (n = 13) and high (n = 14) caries. Identification of oral bacteria was performed using 16S rRNA sequence, Rothia mucilaginosa and R. aeria were identified in low caries individuals, while R. dentocariosa was detected in high caries individuals. Two Streptococcus spp. were identified only in low caries S. salivarius and S. gordonii whereas S. sanguinis, S. mitis, S. sinensis, S. rubneri, S. vestibularis, S. cristatus and S. massiliensis were identified only in individuals with high caries. This study revealed the absence of R. mucilaginosa in the high caries subjects and its coexistence with the low caries subjects. Streptococcus mutans was insignificant contributor of caries among samples, while, Streptococcus sanguinis was the main constituent of high caries Saudi patients.

Acidogenic and aciduric properties of Streptococcus mutans serotype c according to its genomic variability

Streptococcus mutans (S. mutans) has a wide genetic diversity that contributes to its phenotypic heterogeneity, and may be related to attributes associated with acidogenicity and aciduricity. The aim of this study was to evaluate the acidogenic and aciduric properties of S. mutans serotype c isolates from saliva of schoolchildren according to the genomic variability. S. mutans isolates were identified by polymerase chain reaction. Fifty S. mutans serotype c isolates were genotyped by pulsed field gel electrophoresis and tested for their ability to produce and resist acid. Three specific genotypes were identified in the caries-active group and only one in the caries-free group. Although isolates were similarly acidogenic, an exclusive caries-active genotype had the greatest glycolytic activity. In contrast, isolates exhibited variable aciduricity, and three caries-active genotypes were the least aciduric. We concluded that there is genetic variability within serotype c. Acid production was similar regardless of the caries status but correlated with the number of genotypes. In addition, resistance to acid could be an important characteristic for the establishment and colonisation of specific genotypes in children with caries. However, it is important to evaluate children's intrinsic characteristics and other phenotypic properties to explain the physiopathological behaviour of the different genotypes.

Manganese transport by Streptococcus sanguinis in acidic conditions and its impact on growth in vitro and in vivo

Streptococcus sanguinis is an oral commensal and an etiological agent of infective endocarditis. Previous studies have identified the SsaACB manganese transporter as essential for endocarditis virulence; however, the significance of SsaACB in the oral environment has never been examined. Here we report that a ΔssaACB deletion mutant of strain SK36 exhibits reduced growth and manganese uptake under acidic conditions. Further studies revealed that these deficits resulted from the decreased activity of TmpA, shown in the accompanying paper to function as a ZIP‐family manganese transporter. Transcriptomic analysis of fermentor‐grown cultures of SK36 WT and ΔssaACB strains identified pH‐dependent changes related to carbon catabolite repression in both strains, though their magnitude was generally greater in the mutant. In strain VMC66, which possesses a MntH transporter, loss of SsaACB did not significantly alter growth or cellular manganese levels under the same conditions. Interestingly, there were only modest differences between SK36 and its ΔssaACB mutant in competition with Streptococcus mutans in vitro and in a murine oral colonization model. Our results suggest that the heterogeneity of the oral environment may provide a rationale for the variety of manganese transporters found in S. sanguinis.

Potential of Prebiotic D-Tagatose for Prevention of Oral Disease

Recent studies have shown phenotypic and metabolic heterogeneity in related species including Streptococcus oralis, a typical oral commensal bacterium, Streptococcus mutans, a cariogenic bacterium, and Streptococcus gordonii, which functions as an accessory pathogen in periodontopathic biofilm. In this study, metabolites characteristically contained in the saliva of individuals with good oral hygiene were determined, after which the effects of an identified prebiotic candidate, D-tagatose, on phenotype, gene expression, and metabolic profiles of those three key bacterial species were investigated. Examinations of the saliva metabolome of 18 systemically healthy volunteers identified salivary D-tagatose as associated with lower dental biofilm abundance in the oral cavity (Spearman’s correlation coefficient; r = -0.603, p = 0.008), then the effects of D-tagatose on oral streptococci were analyzed in vitro. In chemically defined medium (CDM) containing D-tagatose as the sole carbohydrate source, S. mutans and S. gordonii each showed negligible biofilm formation, whereas significant biofilms were formed in cultures of S. oralis. Furthermore, even in the presence of glucose, S. mutans and S. gordonii showed growth suppression and decreases in the final viable cell count in a D-tagatose concentration-dependent manner. In contrast, no inhibitory effects of D-tagatose on the growth of S. oralis were observed. To investigate species-specific inhibition by D-tagatose, the metabolomic profiles of D-tagatose-treated S. mutans, S. gordonii, and S. oralis cells were examined. The intracellular amounts of pyruvate-derived amino acids in S. mutans and S. gordonii, but not in S. oralis, such as branched-chain amino acids and alanine, tended to decrease in the presence of D-tagatose. This phenomenon indicates that D-tagatose inhibits growth of those bacteria by affecting glycolysis and its downstream metabolism. In conclusion, the present study provides evidence that D-tagatose is abundant in saliva of individuals with good oral health. Additionally, experimental results demonstrated that D-tagatose selectively inhibits growth of the oral pathogens S. mutans and S. gordonii. In contrast, the oral commensal S. oralis seemed to be negligibly affected, thus highlighting the potential of administration of D-tagatose as an oral prebiotic for its ability to manipulate the metabolism of those targeted oral streptococci.

Effectiveness and safety of Bifidobacterium in preventing dental caries: a systematic review and meta-analysis

OBJECTIVES

The effectiveness and safety of Bifidobacterium in dental caries prevention are controversial. Thus, we performed this systematic review and meta-analysis to explore the preventive value of Bifidobacterium.

METHODS

Eligible studies were identified from several databases, including PubMed, the Cochrane Library, Embase, Web of Science, and Scopus. Hand searches were also conducted in relevant bibliographies. We then extracted and pooled standardized mean difference (SMD) and risk ratio (RR) to analyze the anti-caries effect of Bifidobacterium with Stata 16.0 software. If the data obtained was not suitable for meta-analysis, qualitative descriptions were performed.

RESULTS

Compared with the placebo control group, there was no statistically significant reduction in Streptococcus mutans and Lactobacilli counts in saliva in the test group. Also, there were no significant differences in Streptococcus mutans and Lactobacillus counts in dental plaque and no significant difference in caries incidence in deciduous teeth. There was no significant difference in the incidence of adverse events between the Bifidobacterium and control groups.

CONCLUSIONS

Available evidence demonstrates that Bifidobacterium is neither effective in reducing Streptococcus mutans and Lactobacillus counts in the saliva or dental plaque nor in reducing the occurrence of caries in deciduous teeth. Evaluation of its safety requires further investigations. Therefore, Bifidobacterium is not a competent probiotic candidate to prevent dental caries.

Metagenomic Analysis Reveals Neisseria bacilliformis Variation in the Early Childhood Caries Plaque Microbiome

The progression of early childhood caries (ECC) is caused by microbial colonized in dental plaque. However, the association framework both from 16s genus down to high resolution metagenomic strain level and from composition to genome function analysis on caries lacks. 16S rRNA sequence revealed the composition of 3-6 years dental caries (ECC, n = 29), and severe dental caries (SECC, n = 36) children are significantly different from caries-free controls (CF, n = 31). Especially, genus Neisseria is enriched in caries (P < 0.05). Metagenomics sequence of 3 ECCs, 3 SECCs, and 3 CFs reveals Neisseria bacilliformis ATCC BAA-1200 in genus Neisseria is also significantly enriched in caries (P < 0.05). Then, we recovered high-quality metagenomic assembly genomes (MAG), named bin 86, which have 99% identity with Neisseria bacilliformis ATCC BAA-1200 genome. Function analysis of Neisseria bacilliformis ATCC BAA-1200 genome shows its metabolism power of sugar and adhesion, colonization, acid production, and acid tolerance ability, which suggested Neisseria bacilliformis ATCC BAA-1200 may serve as a biomarker for childhood caries.

Symbiosis and Dysbiosis of the Human Mycobiome

The influence of microbiological species has gained increased visibility and traction in the medical domain with major revelations about the role of bacteria on symbiosis and dysbiosis. A large reason for these revelations can be attributed to advances in deep-sequencing technologies. However, the research on the role of fungi has lagged. With the continued utilization of sequencing technologies in conjunction with traditional culture assays, we have the opportunity to shed light on the complex interplay between the bacteriome and the mycobiome as they relate to human health. In this review, we aim to offer a comprehensive overview of the human mycobiome in healthy and diseased states in a systematic way. The authors hope that the reader will utilize this review as a scaffolding to formulate their understanding of the mycobiome and pursue further research.

The induction of inflammation by the cGAS-STING pathway in human dental pulp cells: A laboratory investigation

AIM

To explore the presence of the cGAS-STING inflammatory pathway in human pulp tissue and human dental pulp cells (HDPCs).

METHODOLOGY

Pulp tissue was collected from freshly extracted human healthy third molars or third molars with irreversible pulpitis. Quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunoassay (ELISA) were performed to assess IFN-β, TNF and IL-6. Human dental pulp cells prepared from healthy human pulp tissues were transfected with interferon stimulatory DNA (ISD), bacterial genomic DNA, bacterial cyclic dinucleotides c-di-AMP, c-di-GMP or host cyclic dinucleotide cGAMP. SiRNA was used to knock down the endogenous cGAS or STING. G140 and H-151 were used to inhibit cGAS and STING respectively. Amlexanox and BAY 11-7082 were used to inhibit TBK1 and NF-κB respectively. qRT-PCR and ELISA were performed to detect the level of IFN-β, TNF and IL-6. Western blot was performed to evaluate the TBK1, IRF3 and p65 phosphorylation. The Student's t-test and one-way anova were used for statistical analysis.

RESULTS

IFN-β, TNF and IL-6 were up-regulated in the inflamed human dental pulp tissue. CGAS and STING mRNA were increased in the inflamed human dental pulp tissue and detected in HDPCs prepared from healthy human pulp tissues. ISD transfection induced TBK1, IRF3 and p65 phosphorylation as well as IFN-β, TNF and IL-6 production. IFN-β, TNF and IL-6 production were also induced by transfection of bacterial and host cyclic dinucleotides or bacteria DNA. ISD or bacteria DNA transfection elevated the intracellular levels of cGAMP. Knock-down of cGAS or STING, as well as using cGAS inhibitor G140 or STING inhibitor H-151 abolished the IFN-β, TNF and IL-6 production induced by ISD transfection. Knock-down of STING or using STING inhibitor H-151 abolished the IFN-β, TNF and IL-6 induction by transfection of bacterial and host cyclic dinucleotides. Both Amlexanox and BAY 11-7082 inhibited IFN-β, TNF and IL-6 production triggered by ISD and cyclic dinucleotides transfection.

CONCLUSIONS

Human dental pulp cells expressed an intact cGAS-STING signalling axis. The cGAS-STING signalling axis may play an important role in pulp inflammation and immune defence.

Associations between dental caries and systemic diseases: a scoping review

BACKGROUND

The objective of this study was to evaluate and present evidence from animal and human clinical studies on associations between dental caries and systemic diseases, and to suggest potential mechanisms that might explain such associations.

METHODS

An electronic search was conducted of PubMed, Embase and Cochrane Central Register of Controlled Trials for articles published from 2010 to 2020 in the English language. From the initial search, 404 full-text studies were assessed for eligibility. After excluding studies for technical and study limitations, a total of 67 studies were included in the summary tables and additional studies were included in the review to support evidence.

RESULTS

Few systemic disease and conditions were found to be clinically meaningfully associated with caries experience. Best evidence from human and animal studies described association between metabolic diseases and dental caries. Several interesting animal studies were noted that could generate clinical hypotheses and further investigations in rodent models for cardiovascular injury and hyperglycemia. Inadequate data was found to suggest any modifications to current clinical practice or prevention guidelines.

CONCLUSIONS

Limited clinical evidence was found connecting several systemic diseases and dental caries. Inadequate data was found to suggest any modifications to current clinical practice or prevention guidelines.

CLINICAL SIGNIFICANCE

Understanding of associations between dental caries and systemic diseases play a crucial role in the treatment planning and education of the dental patient.

Evaluation of bactericidal effects of ultraviolet light C irradiation on cariogenic bacteria: An in vitro study

Backgrounds

Ultraviolet light C (UVL-C) irradiation has demonstrated an antimicrobial action against various pathogens. This study aimed to evaluate the bactericidal effect of UVL-C irradiation against cariogenic oral bacteria (Streptococcus mutans) in single layers and colonies grown on solid surfaces.

Methods

Two different experiments were performed. In the first experiment, a single layer of Streptococcus mutans bacteria on agar plates was exposed to UVL-C irradiation at energies from 0 to 21 mWs/cm². The second experiment was conducted to inhibit viability of bacterial colonies on solid surfaces. The samples were derived from saliva from a patient where bacteria were grown on plastic strips and then exposed to UVL-C. The highest energy was 1050 mWs/cm².

Results

Exposure to 21 mWs/cm² was bactericidal in single layers of Streptococcus mutans. The result for bacterial colonies on solid surfaces indicated only a bacteriostatic effect, even at energies of 1050 mWs/cm².

Conclusions

Ultraviolet light C exhibits bactericidal effects on single layers of Streptococcus mutans but has a limited effect on bacterial colonies in a biofilm. It is a matter of debate whether these in vitro results would have the same effect in clinical setting.

Oral Microbiota: A Major Player in the Diagnosis of Systemic Diseases

The oral cavity is host to a complex and diverse microbiota community which plays an important role in health and disease. Major oral infections, i.e., caries and periodontal diseases, are both responsible for and induced by oral microbiota dysbiosis. This dysbiosis is known to have an impact on other chronic systemic diseases, whether triggering or aggravating them, making the oral microbiota a novel target in diagnosing, following, and treating systemic diseases. In this review, we summarize the major roles that oral microbiota can play in systemic disease development and aggravation and also how novel tools can help investigate this complex ecosystem. Finally, we describe new therapeutic approaches based on oral bacterial recolonization or host modulation therapies. Collaboration in diagnosis and treatment between oral specialists and general health specialists is of key importance in bridging oral and systemic health and disease and improving patients' wellbeing.

Predicting dental caries increment using salivary biomarkers in a remote Indigenous Australian child population

BACKGROUND

The burden of childhood dental caries amongst Indigenous Australians is higher than in other Australians. Because of differences in lifestyle and the evolutionary history of the oral microbiota, associated risk indicators may differ. Here, we evaluate associations between caries increment, salivary biomarkers and baseline caries among children aged 5-17 years residing in a remote rural Indigenous community.

METHODS

This study was part of a trial assessing cost-effectiveness of an intervention to prevent dental caries among children. Baseline epidemiology and application of topical caries-preventive measures was conducted in 2015, followed-up in 2016 and 2017. Children who did not consent or failed to attend the prevention visits but did attend for follow-up epidemiology constituted a natural comparison group for evaluating the intervention. Saliva flow, pH, buffering and bacterial loads were measured at all visits. Caries was scored by the International Caries Detection and Assessment system. Outcome was caries increment. Explanatory variables were sex, being in experimental or comparison group, baseline caries, saliva flowrate and buffering, pH, and salivary loads of mutans streptococci (MS), Lactobacilli (LB), and yeast. Chi Square tests compared caries incidence in relation to explanatory variables and Generalised Linear Models explored associations between explanatory and outcome variables.

RESULTS

Of 408 participants at baseline, only 208 presented at 2-year follow-up. Of caries-free children at baseline, significantly fewer had incipient (p = 0.01) and advanced (p = 0.04) caries after two years. Children in the experimental group experienced fewer tooth surfaces with advanced caries (p = 0.02) than comparison children. Having caries at baseline (p = 0.02) and low salivary flow-rates (p < 0.001) saw a significant increase in advanced caries after two years. Children with high salivary loads of MS (p = 0.03) and LB (p = 0.004) experienced more advanced carious surfaces. Multivariable analysis revealed 58% reduction (p = 0.001) in advanced caries among children with high salivary flow rates. Caries increment was 61% (p = 0.03) more for incipient and 121% (p = 0.007) more for advanced caries among children who harboured higher loads of MS.

CONCLUSION

As with other ethnicities, children with low salivary flow and those with high MS had higher incipient and advanced caries increments after two years. Such risk assessments facilitate targeted preventive interventions for such communities.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ANZCTR), No: ACTRN12615000693527: 3 July 2015.

Antibacterial effect of a disinfectant spray for sports mouthguards on Streptococcus sobrinus

BACKGROUND

Mouthguard (MG) disinfectant sprays are available for maintaining MG hygiene. The effect of these sprays against Streptococcus sobrinus is still unknown. The purpose of this study was to evaluate the antibacterial effect of an MG disinfectant spray against S. sobrinus using the modified ISO 22196 standard.

MATERIALS AND METHODS

In this in vitro study, we used the following treatment groups for antibacterial testing: MG spray-1 (left in spray for 30 s), MG spray-2 (60 s), and control (n = 4). All analyses were performed at a statistically significant level (P = 0.05) using JMP^® 14.

RESULTS

The log colony-forming units of the MG spray-2 group were significantly lower than those of the other groups. The antibacterial activity of MG spray-2 against S. sobrinus was >2.1.

CONCLUSION

We confirmed the antibacterial effect of the MG spray against S. sobrinus, and it was influenced by the treatment duration, with the optimum effect at a longer duration.

Progress in Oral Microbiome Related to Oral and Systemic Diseases: An Update

The human oral microbiome refers to an ecological community of symbiotic and pathogenic microorganisms found in the oral cavity. The oral cavity is an environment that provides various biological niches, such as the teeth, tongue, and oral mucosa. The oral cavity is the gateway between the external environment and the human body, maintaining oral homeostasis, protecting the mouth, and preventing disease. On the flip side, the oral microbiome also plays an important role in the triggering, development, and progression of oral and systemic diseases. In recent years, disease diagnosis through the analysis of the human oral microbiome has been realized with the recent development of innovative detection technology and is overwhelmingly promising compared to the previous era. It has been found that patients with oral and systemic diseases have variations in their oral microbiome compared to normal subjects. This narrative review provides insight into the pathophysiological role that the oral microbiome plays in influencing oral and systemic diseases and furthers the knowledge related to the oral microbiome produced over the past 30 years. A wide range of updates were provided with the latest knowledge of the oral microbiome to help researchers and clinicians in both academic and clinical aspects. The microbial community information can be utilized in non-invasive diagnosis and can help to develop a new paradigm in precision medicine, which will benefit human health in the era of post-metagenomics.

Function-adaptive clustered nanoparticles reverse Streptococcus mutans dental biofilm and maintain microbiota balance

Dental plaques are biofilms that cause dental caries by demineralization with acidogenic bacteria. These bacteria reside inside a protective sheath which makes any curative treatment challenging. We propose an antibiotic-free strategy to disrupt the biofilm by engineered clustered carbon dot nanoparticles that function in the acidic environment of the biofilms. In vitro and ex vivo studies on the mature biofilms of Streptococcus mutans revealed >90% biofilm inhibition associated with the contact-mediated interaction of nanoparticles with the bacterial membrane, excessive reactive oxygen species generation, and DNA fragmentation. An in vivo examination showed that these nanoparticles could effectively suppress the growth of S. mutans. Importantly, 16S rRNA analysis of the dental microbiota showed that the diversity and richness of bacterial species did not substantially change with nanoparticle treatment. Overall, this study presents a safe and effective approach to decrease the dental biofilm formation without disrupting the ecological balance of the oral cavity.