Taxonomic and Functional Analyses of the Supragingival Microbiome from Caries-Affected and Caries-Free Hosts

The short-term impact of comprehensive caries treatment on the supragingival microbiome of severe early childhood caries

BACKGROUND

Children affected by severe early childhood caries (S-ECC) usually need comprehensive caries treatment due to the extensive of caries. How the oral microbiome changes after caries therapy within the short-term warrant further study.

AIM

This study aimed to investigate the short-term impact of comprehensive caries treatment on the supragingival plaque microbiome of S-ECC children.

DESIGN

Thirty-three children aged 2-4 years with severe caries (dt > 7) were recruited. Comprehensive caries treatment was performed under general anesthesia in one session and included restoration, pulp treatment, extraction, and fluoride application. Supragingival plaque was sampled pre- and 1-month posttreatment. The genomic DNA of the supragingival plaque was extracted, and bacterial 16S ribosomal RNA gene sequencing was performed.

RESULTS

Our data showed that the microbial community evenness significantly decreased posttreatment. Furthermore, comprehensive caries treatment led to more diverse microbial structures among the subjects. The interbacterial interactions reflected by the microbial community's co-occurrence network tended to be less complex posttreatment. Caries treatment increased the relative abundance of Corynebacterium matruchotii, Corynebacterium durum, Actinomyces naeslundii, and Saccharibacteria HMT-347, as well as Aggregatibacter HMT-458 and Haemophilus influenzae. Meanwhile, the relative abundance of Streptococcus mutans, three species from Leptotrichia, Neisseria bacilliformis, and Provotella pallens significantly decreased posttreatment.

CONCLUSION

Our results suggested that comprehensive caries treatment may contribute to the reconstruction of a healthier supragingival microbiome.

Multiomics analysis reveals the genetic and metabolic characteristics associated with the low prevalence of dental caries

Background

Despite poor oral hygiene, the Baiku Yao (BKY) ethnic group in China presents a low prevalence of dental caries, which may be related to genetic susceptibility. Due to strict intra-ethnic marriage rule, this ethnic has an advantage in studying the interaction between genetic factors and other regulatory factors related to dental caries.

Methods

Peripheral blood from a caries-free adult male was used for whole genome sequencing, and the BKY assembled genome was compared to the Han Chinese genome. Oral saliva samples were collected from 51 subjects for metabolomic and metagenomic analysis. Multiomics data were integrated for combined analysis using bioinformatics approaches.

Results

Comparative genomic analysis revealed the presence of structural variations in several genes associated with dental caries. Metabolomic and metagenomic sequencing demonstrated the caries-free group had significantly higher concentration of antimicrobials and higher abundance of core oral health-related microbiota. The functional analysis indicated that cationic antimicrobial peptide resistance and the lipopolysaccharide biosynthesis pathway were enriched in the caries-free group.

Conclusions

Our study provided new insights into the specific regulatory mechanisms that contribute to the low prevalence of dental caries in the specific population and may provide new evidence for the genetic diagnosis and control of dental caries.

Effects of different soil water holding capacities on vegetable residue return and its microbiological mechanism

With the gradual expansion of the protected vegetable planting area, dense planting stubbles and increasing labor cost, the treatment of vegetable residues has become an urgent problem to be solved. Soil bacterial community structure plays an important role in vegetable residue return and is susceptible to environmental changes. Therefore, understanding the influences of different soil water holding capacities on plant residue decomposition and soil bacterial communities is important for biodegradation. During the whole incubation period, the weight loss ratio of plant residue with 100% water holding capacity was 69.60 to 75.27%, which was significantly higher than that with 60% water holding capacity in clay and sandy soil, indicating that high water holding capacity promoted the decomposition of plant residue. The degradation of lignin and cellulose was also promoted within 14 days. Furthermore, with the increase in soil water holding capacity, the contents of NH4+ increased to 5.36 and 4.54 times the initial value in the clay and sandy soil, respectively. The increase in napA and nrfA resulted in the conversion of NO3- into NH4+. The increase in water holding capacity made the bacterial network structure more compact and changed the keystone bacteria. The increase in water holding capacity also increased the relative abundance of Firmicutes at the phylum level and Symbiobacterium, Clostridium at the genus level, which are all involved in lignin and cellulose degradation and might promote their degradation. Overall, these findings provide new insight into the effects of different soil water holding capacities on the degradation of plant residues in situ and the corresponding bacterial mechanisms.

Oral microbial communities in 5-year-old children with versus without dental caries

BACKGROUND

Caries in young children has received more and more attention. The study of the oral microbiota may help to understand the polymicrobial etiology of dental caries.

OBJECTIVES

To investigate the diversity and structure of microbial communities in saliva samples from 5-year-old children with versus without dental caries.

METHODS

A total of 36 saliva samples were collected from 18 children with high caries (HB group) and from 18 children without caries (NB group). Then, 16S rDNA was amplified from bacterial samples using polymerase chain reaction, and high-throughput sequencing was performed using Illumina Novaseq platforms.

RESULTS

Sequences were clustered into operational taxonomic units (OTUs), which were distributed among 16 phyla, 26 classes, 56 orders, 93 families, 173 genera, and 218 species. Firmicutes, Bacteroides, Proteobacteria, Actinobacteria, Fusobacteria, Patescibacteria, Epsilonbacteraeota, Cyanobacteria, Acidobacteria and Spirochaetes were basically the same in different groups, but their relative abundances were different. The core microbiome was defined as the species from 218 shared microbial taxa. The alpha diversity test showed that there were no significant differences in microbial abundance and diversity between the high caries and no caries groups. The results from principal coordinate analysis (PCoA) and hierarchical clustering showed that the two groups had similar microorganisms. The biomarkers of different groups were defined by LEfSe analysis to identify potential caries-related and health-related bacteria. Co-occurrence network analysis of dominant genera showed that oral microbial communities in the no caries group were more complex and aggregated than those in the high caries group. Finally, the PICRUSt algorithm was used to predict the function of the microbial communities from saliva samples. The obtained results showed that mineral absorption was greater in the no caries group than in the high caries group. BugBase was used to determine phenotypes present in microbial community samples. The obtained results showed that Streptococcus was greater in the high caries group than in the no caries group.

CONCLUSION

Findings of this study provide a comprehensive understanding of the microbiological etiology of dental caries in 5-year-old children and are expected to provide new methods for its prevention and treatment.

Identification of Putative Bacterial Pathogens for Orofacial Granulomatosis Based on 16S rRNA Metagenomic Analysis

Orofacial granulomatosis (OFG) is a chronic inflammatory disease characterized by nontender swelling of the orofacial tissues, the underlying cause of which remains unknown. Our previous study demonstrated that tooth apical periodontitis (AP) is involved in the development of OFG. To characterize the AP bacterial signatures of OFG patients and identify possible pathogenic bacteria that cause OFG, the compositions of the AP microbiotas in OFG patients and controls were compared using 16S rRNA gene sequencing. Pure cultures of putative bacterial pathogens were established by growing bacteria as colonies followed by purification, identification, and enrichment and then were injected into animal models to determine the causative bacteria contributing to OFG. A specific AP microbiota signature in the OFG patients was shown, characterized by the predominance of phyla Firmicutes and Proteobacteria, notably members of the genera Streptococcus, Lactobacillus, and Neisseria, were found. Streptococcus spp., Lactobacillus casei, Neisseria subflava, Veillonella parvula, and Actinomyces spp. from OFG patients were isolated and successfully cultured in vitro and then injected into mice. Ultimately, footpad injection with N. subflava elicited granulomatous inflammation. IMPORTANCE Infectious agents have long been considered to play a role in the initiation of OFG; however, a direct causal relationship between microbes and OFG has not yet been established. In this study, a unique AP microbiota signature was identified in OFG patients. Moreover, we successfully isolated candidate bacteria from AP lesions of OFG patients and assessed their pathogenicity in laboratory mice. Findings from this study may help provide in-depth insights into the role of microbes in OFG development, providing the basis for targeted therapeutic approaches for OFG.

Fluoride and gallein inhibit polyphosphate accumulation by oral pathogen Rothia dentocariosa

The uptake and storage of extracellular orthophosphate (Pi) by polyphosphate (polyP) accumulating bacteria may contribute to mineral dissolution in the oral cavity. To test the effect of potential inhibitors of polyP kinases on Rothia dentocariosa, gallein (0, 25, 50, and 100 μM) and fluoride (0, 50, and 100 ppm) were added to R. dentocariosa cultures grown in brain-heart infusion broth. At a late log growth phase (8 h), extracellular Pi was measured using an ascorbic acid assay, and polyP was isolated from bacterial cells treated with RNA/DNAases using a neutral phenol/chloroform extraction. Extracts were hydrolyzed and quantified as above. Gallein and fluoride had minor effects on bacterial growth with NaF having a direct effect on media pH. Gallein (≥25 μM) and fluoride (≥50 ppm) attenuated the bacterial drawdown of extracellular Pi by 56.7% (P < 0.05) and 37.3% (P < 0.01). There was a corresponding polyP synthesis decrease of 73.2% (P < 0.0001) from gallein and 83.1% (P < 0.0001) from fluoride. Attenuated total reflectance-Fourier-transform infrared spectroscopy validated the presence of polyP and its reduced concentration in R. dentocariosa bacterial cells following gallein and fluoride treatment. Rothia dentocariosa can directly change extracellular Pi and accumulate intracellular polyP, but the mechanism is attenuated by gallein and NaF.

High-Throughput Sequencing Analysis of the Changes in the Salivary Microbiota of Hungarian Young and Adult Subpopulation by an Anthocyanin Chewing Gum and Toothbrush Change

The sour cherry contains anthocyanins, which have bactericide action against some oral bacteria (Klebsiella pneumoniae, Pseudomonas aeruginosa). Sour cherry also has antibiofilm action against Streptococcus mutans, Candida albicans, and Fusobacterium nucleatum. Our earlier research proved that chewing sour cherry anthocyanin gum significantly reduces the amount of human salivary alpha-amylase and Streptococcus mutans levels. The microbiota of a toothbrush affects oral health and regular toothbrush change is recommended. A total of 20 healthy participants were selected for the study. We analysed saliva samples with 16S rRNA sequencing to investigate the effect of 2 weeks (daily three times, after main meals) of chewing sour cherry anthocyanin gum-supplemented by toothbrush change in half of our case-control study cohort-after scaling on human oral microbiota. A more stable and diverse microbiome could be observed after scaling by the anthocyanin gum. Significant differences between groups (NBR: not toothbrush changing; BR: toothbrush changing) were evaluated by log₂ proportion analysis of the most abundant family and genera. The analysis showed that lower level of some Gram-negative anaerobic (Prevotella melaninogenica, Porphyromonas pasteri, Fusobacterium nucleatum subsp. vincentii) and Gram-positive (Rothia mucilaginosa) bacteria could be observed in the case group (BR), accompanied by build-up of health-associated Streptococcal network connections.

Impact of different oral treatments on the composition of the supragingival plaque microbiome

Background

Dental plaque consists of a diverse microbial community embedded in a complex structure of exopolysaccharides. Dental biofilms form a natural barrier against pathogens but lead to oral diseases in a dysbiotic state.

Objective

Using a metaproteome approach combined with a standard plaque-regrowth study, this pilot study examined the impact of different concentrations of lactoperoxidase (LPO) on early plaque formation, and active biological processes.

Design

Sixteen orally healthy subjects received four local treatments as a randomized single-blind study based on a cross-over design. Two lozenges containing components of the LPO-system in different concentrations were compared to a placebo and Listerine®. The newly formed dental plaque was analyzed by mass spectrometry (nLC-MS/MS). 

Results

On average 1,916 metaproteins per sample were identified, which could be assigned to 116 genera and 1,316 protein functions. Listerine® reduced the number of metaproteins and their relative abundance, confirming the plaque inhibiting effect. The LPO-lozenges triggered mainly higher metaprotein abundances of early and secondary colonizers as well as bacteria associated with dental health but also periodontitis. Functional information indicated plaque biofilm growth.

Conclusion

In conclusion, the mechanisms on plaque biofilm formation of Listerine® and the LPO-system containing lozenges are different. In contrast to Listerine®, the lozenges led to a higher bacterial diversity.

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.

Xylitol-Containing Chewing Gum Reduces Cariogenic and Periodontopathic Bacteria in Dental Plaque—Microbiome Investigation

Background

Dental caries and periodontal disease remain the most prevalent oral health problems in the world. Chewing xylitol gum may help reduce the risk of caries and periodontitis for dental health benefits. However, little evidence has shown healthy food estimation by sequencing 16S rDNA in oral microbial communities. This study investigated the clinical effect of xylitol chewing gum on dental plaque accumulation and microbiota composition using the PacBio full-length sequencing platform in 24 young adults (N = 24). The participants were randomly assigned to xylitol chewing gum and control (no chewing gum) groups. Participants in the chewing gum group chewed ten pieces of gum (a total of 6.2 g xylitol/day). Dental plaque from all teeth was collected for weighing, measuring the pH value, and analysis of microbial communities at the beginning (baseline, M0) and end of the 2-week (effect, M1) study period.

Results

The results suggested a 20% reduction in dental plaque accumulation (p &lt; 0.05) among participants chewing xylitol gum for 2 weeks, and the relative abundance of Firmicutes (a type of pathogenic bacteria associated with caries) decreased by 10.26% (p &lt; 0.05) and that of Bacteroidetes and Actinobacteria (two types of pathogenic bacteria associated with periodontitis) decreased by 6.32% (p &lt; 0.001) and 1.66% (p &lt; 0.05), respectively. Moreover, the relative abundance of Fusobacteria was increased by 9.24% (p &lt; 0.001), which has been proven to have a higher proportion in dental plaque of healthy adults. However, the dental plaque pH value stayed in a healthy range for the two groups.

Conclusion

In conclusion, chewing xylitol gum would benefit cariogenic and periodontal bacterial reduction in the oral cavity, which could help to prevent the diseases related to these bacteria.

From Mouth to Brain: Distinct Supragingival Plaque Microbiota Composition in Cerebral Palsy Children With Caries

Children with cerebral palsy (CP) present a higher prevalence and severity of caries. Although researchers have studied multiple risk factors for caries in CP, the role of microorganisms in caries remains one of the critical factors worth exploring. In order to explore the differences in the supragingival plaque microbiota (SPM), supragingival plaque samples were collected from 55 CP children and 23 non-CP children for 16S rRNA sequencing. Distinct SPM composition was found between CP children with severe caries (CPCS) and non-CP children with severe caries (NCPCS). Further subanalysis was also done to identify if there were any differences in SPM among CP children with different degrees of caries, namely, caries-free (CPCF), mild to moderate caries (CPCM), and severe caries (CPCS). After selecting the top 15 most abundant species in all groups, we found that CPCS was significantly enriched for Fusobacterium nucleatum, Prevotella intermedia, Campylobacter rectus, Porphyromonas endodontalis, Catonella morbi, Alloprevotella tannerae, Parvimonas micra, Streptobacillus moniliformis, and Porphyromonas canoris compared to NCPCS. By comparing CPCF, CPCM, and CPCS, we found that the core caries-associated microbiota in CP children included Prevotella, Alloprevotella, Actinomyces, Catonella, and Streptobacillus, while Capnocytophaga and Campylobacter were dental health-associated microbiota in CP children. Alpha diversity analysis showed no significant difference between NCPCS and CPCS, but the latter had a much simpler core correlation network than that of NCPCS. Among CP children, CPCM and CPCF displayed lower bacterial diversity and simpler correlation networks than those of CPCS. In summary, the study showed the specific SPM characteristics of CPCS compared to NCPCS and revealed the core SPM in CP children with different severities of caries (CPCF, CPCM, and CPCS) and their correlation network. Hopefully, the study would shed light on better caries prevention and therapies for CP children. Findings from the current study offer exciting insights that warrant larger cohort studies inclusive of saliva and feces samples to investigate the potential pathogenic role of oral microbiota through the oral–gut–brain axis in CP children with caries.

Supragingival microbiome alternations as a consequence of smoking different tobacco types and its relation to dental caries

This study aimed to assess the effect of smoking different tobacco types on the supragingival microbiome and its relation to dental caries. Forty supragingival plaque samples were collected from smokers of a single tobacco type and non-smokers seeking treatment at the University Dental Hospital Sharjah, UAE. DMFT (decayed, missing and filled teeth) was determined for all participants who were divided into two groups: no-low caries (NC-LC: DMFT = 0-4; n = 18) and moderate-high caries (MC-HC: DMFT = 5-20; n = 22). 16S rRNA gene was sequenced using third-generation sequencing with Nanopore technology. Microbiome composition and diversity were compared. Caries was most common among cigarette smokers. Supragingival microbiota were significantly altered among smokers of different tobacco types. In cigarette smokers, cariogenic bacteria from genus Streptococcus (including S. mutans) were significantly more among subjects with NC-LC, while Lactobacilli (including L. fermentum) were more among subjects with MC-HC. In medwakh smokers, several periodontopathogens were significantly elevated in subjects with NC-LC, while other pathogenic bacteria (as Klebsiella pneumoniae) were more in those with MC-HC. Cigarette and alternative tobacco smoking had a significant impact on the supragingival microbiome. Indeed, further studies are required to unravel the consequences of oral dysbiosis triggered by smoking. This could pave the way for microbiota-based interventional measures for restoring a healthy oral microbiome which could be a promising strategy to prevent dental caries.

The predictive power of saliva electrolytes exceeds that of saliva microbiomes in diagnosing early childhood caries

Early childhood caries (ECC) is one of the most prevalent chronic diseases affecting children worldwide, and thus its etiology, diagnosis, and prognosis are of particular clinical significance. This study aims to test the ability of salivary microbiome and electrolytes in diagnosing ECC, and their interplays within the same population. We here simultaneously profiled salivary microbiome and biochemical components of 331 children (166 caries-free (H group) and 165 caries-active children (C group)) aged 4-6 years. We identified both salivary microbial and biochemical dysbiosis associated with ECC. Remarkably, K⁺, Cl^-, NH₄⁺, Na⁺, SO₄^2-, Ca²⁺, Mg²⁺, and Br^- were enriched while pH and NO₃^- were depleted in ECC. Moreover, the dmft index (ECC severity) positively correlated with Cl^-, NH₄⁺, Ca²⁺, Mg²⁺, Br^-, while negatively with pH and NO₃^-. Furthermore, machine-learning classification models were constructed based on these biomarkers from saliva microbiota, or electrolytes (and pH). Unexpectedly, the electrolyte-based classifier (AUROC = 0.94) outperformed microbiome-based (AUROC = 0.70) one and the composite-based one (with both microbial and biochemical data; AUC = 0.89) in predicting ECC. Collectively, these findings indicate ECC-associated alterations and interplays in the oral microbiota, electrolytes and pH, underscoring the necessity of developing diagnostic models with predictors from salivary electrolytes.

Tooth brushing using toothpaste containing theaflavins reduces the oral pathogenic bacteria in healthy adults

Theaflavins (TFs) are the main bioactive component in black tea. At present, little effort has been done to evaluate the influence of TFs when included in the toothpaste on the diversity of oral microbiota. In this study, eighty samples collected from the saliva and supragingival plaque of 20 healthy adults using toothpaste with the absence or presence of TFs for a period of 4 weeks were used for the oral microbiome analysis by 16S rRNA gene sequencing. Alpha and beta diversity analysis showed that tooth brushing using the toothpaste with TFs significantly increased the microbial abundance in the saliva samples, and altered the oral microbiota obtained from the saliva and supragingival plaque. The linear discriminant analysis revealed that the use of toothpaste with TFs significantly reduced the abundance of oral pathogens (e.g., Prevotella, Selenomonas, and Atopobium) while increased the abundance of oral-health associated bacteria (e.g., Streptococcus and Rothia). In addition, using toothpaste with TFs reduced the functional pathways abundance relevance to the extracellular polymeric substance (EPS) synthesis while enriched the functions in transporters, ABC transporters, two-component system, and amino acid metabolism. Collectively, our results provide evidence for the application of toothpaste containing TFs as a promising oral care product.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02699-7.

Association between Household Exposure to Secondhand Smoke and Dental Caries among Japanese Young Adults: A Cross-Sectional Study

The long-term effects of secondhand smoke (SHS) on dental caries among Japanese young adults remain unclear. The purpose of this cross-sectional study was to evaluate whether household exposure to SHS is associated with dental caries in permanent dentition among Japanese young adults. The study sample included 1905 first-year university students (age range: 18–19 years) who answered a questionnaire and participated in oral examinations. The degree of household exposure to SHS was categorized into four levels according to the SHS duration: no experience (−), past, current SHS < 10 years, and current SHS ≥ 10 years. Dental caries are expressed as the total number of decayed, missing, and filled teeth (DMFT) score. The relationships between SHS and dental caries were determined by logistic regression analysis. DMFT scores (median (25th percentile, 75th percentile)) were significantly higher in the current SHS ≥ 10 years (median: 1.0 (0.0, 3.0)) than in the SHS—(median: 0.0 (0.0, 2.0)); p = 0.001). DMFT ≥ 1 was significantly associated with SHS ≥ 10 years (adjusted odds ratio: 1.50, 95% confidence interval: 1.20–1.87, p < 0.001). Long-term exposure to SHS (≥10 years) was associated with dental caries in permanent dentition among Japanese young adults.

Sucrose promotes caries progression by disrupting the microecological balance in oral biofilms: an in vitro study

Sucrose has long been regarded as the most cariogenic carbohydrate. However, why sucrose causes severer dental caries than other sugars is largely unknown. Considering that caries is a polymicrobial infection resulting from dysbiosis of oral biofilms, we hypothesized that sucrose can introduce a microbiota imbalance favoring caries to a greater degree than other sugars. To test this hypothesis, an in vitro saliva-derived multispecies biofilm model was established, and by comparing caries lesions on enamel blocks cocultured with biofilms treated with sucrose, glucose and lactose, we confirmed that this model can reproduce the in vivo finding that sucrose has the strongest cariogenic potential. In parallel, compared to a control treatment, sucrose treatment led to significant changes within the microbial structure and assembly of oral microflora, while no significant difference was detected between the lactose/glucose treatment group and the control. Specifically, sucrose supplementation disrupted the homeostasis between acid-producing and alkali-producing bacteria. Consistent with microbial dysbiosis, we observed the most significant disequilibrium between acid and alkali metabolism in sucrose-treated biofilms. Taken together, our data indicate that the cariogenicity of sugars is closely related to their ability to regulate the oral microecology. These findings advance our understanding of caries etiology from an ecological perspective.

High-throughput DNA sequencing of microbiota at interproximal sites

Objective: The oral microbiota has been deeply studied by high-throughput sequencing techniques. However, although the interproximal regions have one of the highest caries rates in the oral cavity, information about the bacterial composition at those sites is scarce.

Methods: In this study, we used 16S rRNA Illumina sequencing to describe the microbiota associated to interproximal regions at two time points. In addition, dental plaque samples at the vestibular and lingual surfaces from the same teeth were also analysed at the two time points.

Results: Interproximal-associated microbiota was found to be similar to already described bacterial communities in other mouth niches. Streptoccocus, Veillonella, Rothia, Actinomyces, Neisseria, Haemophilus and Fusobacterium were the most abundant genera in this oral region. Statistical analyses showed that the microbiota from interproximal sites was more similar to that sampled from the vestibular surfaces than to the lingual surfaces. Interestingly, many potentially cariogenic bacteria such as Scardovia, Atopobium or Selenomonas were over-represented in the interproximal regions in comparison with vestibular and lingual sites.

Conclusion: The microbiota at interproximal regions appears to be specific and stable through time. Potentially pathogenic bacteria may increase caries development risk and gingival inflammation at those sites.

Comparison of oral microbiome profiles in stimulated and unstimulated saliva, tongue, and mouth-rinsed water

Epidemiological studies using saliva have revealed relationships between the oral microbiome and many oral and systemic diseases. However, when collecting from a large number of participants such as a large-scale cohort study, the time it takes to collect saliva can be a problem. Mouth-rinsed water, which is water that has been used to rinse the oral cavity, can be used as an alternative method for collecting saliva for oral microbiome analysis because it can be collected in a shorter time than saliva. The purpose of this study was to verify whether mouth-rinsed water is a suitable saliva substitute for analyzing the oral microbiome. We collected samples of mouth-rinsed water, stimulated saliva, unstimulated saliva, and tongue coating from 10 systemic healthy participants, and compared the microbial diversity and composition of the samples using next-generation sequencing of 16S rRNA-encoding genes. The results showed that the microbial diversity of mouth-rinsed water was similar to that of unstimulated and stimulated saliva, and significantly higher than that of tongue-coating samples. The microbial composition at the species level of mouth-rinsed water also showed a very high correlation with the composition of unstimulated and stimulated saliva. These results suggest that the mouth-rinsed water is a suitable collection method instead of saliva for oral microbiome analysis.

Metaproteomics analysis of microbial diversity of human saliva and tongue dorsum in young healthy individuals

Background: The human oral microbiome influences initiation or progression of diseases like caries or periodontitis. Metaproteomics approaches enable the simultaneous investigation of microbial and host proteins and their interactions to improve understanding of oral diseases.

Objective: In this study, we provide a detailed metaproteomics perspective of the composition of salivary and tongue microbial communities of young healthy subjects.

Design: Stimulated saliva and tongue samples were collected from 24 healthy volunteers, subjected to shotgun nLC-MS/MS and analyzed by the Trans-Proteomic Pipeline and the Prophane tool.

Results: 3,969 bacterial and 1,857 human proteins could be identified from saliva and tongue, respectively. In total, 1,971 bacterial metaproteins and 1,154 human proteins were shared in both sample types. Twice the amount of bacterial metaproteins were uniquely identified for the tongue dorsum compared to saliva. Overall, 107 bacterial genera of seven phyla formed the microbiome. Comparative analysis identified significant functional differences between the microbial biofilm on the tongue and the microbiome of saliva.

Conclusion: Even if the microbial communities of saliva and tongue dorsum showed a strong similarity based on identified protein functions and deduced bacterial composition, certain specific characteristics were observed. Both microbiomes exhibit a great diversity with seven genera being most abundant.

Oral microbiomes in children with asthma and dental caries

OBJECTIVE

Recently, a significant association between dental caries and the severity of bronchial asthma in children has been revealed. This finding indicates a possible relationship between the oral microbiome and the pathogenesis of asthma. The purpose of our study was to estimate differences in the dental plaque microbiota of asthmatic children with and without dental caries by 16S rDNA sequencing.

MATERIAL AND METHODS

Dental plaque samples were obtained with a spoon excavator from the occlusal surface of one deciduous tooth (the second mandibular left molar in caries-free children and the most affected tooth in caries-affected children). Total DNA was extracted from dental plaque. DNA libraries were analysed by 16S rRNA gene sequencing on the MiSeq (Illumina) platform.

RESULTS

There were no significant differences in the composition of bacterial communities from both caries-affected and caries-free children with asthma. The "caries-enriched" genus was Veillonella (Veillonellaceae, Selenomonadales, Negativicutes). Relative abundance of Neisseria was significantly higher in caries-free children with asthma (p < 0.05).

CONCLUSIONS

The most significant difference in compared bacterial communities was a higher relative abundance of Veillonella in caries-affected plaques that suggests its involvement in pathogenesis of caries. Potential respiratory pathogens are present in oral cavity of both caries-affected and caries-free asthmatic children.