A practical guide to the oral microbiome and its relation to health and disease

Epigenetic alterations and microbiota changes in the saliva of individuals with binge-eating spectrum disorders compared with normal weight healthy controls

AIMS

Binge-eating spectrum disorders, including bulimia nervosa (BN) and binge-eating disorder (BED), have psychological, behavioral, and physical effects, which present significant challenges for accurate diagnosis and treatment. Identifying biomarkers is thus of relevance to improve diagnostic and treatment strategies.

MAIN METHODS

Saliva collected from female individuals with BED (n = 20), BN (n = 17), and normal weight healthy controls (NW-HC) (n = 20) was analyzed to assess salivary microbiome, exosomal miRNA expression, and DNA methylation of dopaminergic system gene components.

KEY FINDINGS

Microbial diversity was significantly reduced in BED and BN groups compared to NW-HC. Differential abundance analysis revealed that Bacilli (class-level) were enriched in BN and BED, while Lachnospirales (order-level) were significantly depleted in BN compared to NW-HC. In total, 79 miRNAs were differentially expressed in patients compared with controls. Alteration in four of these miRNAs (let-7b-5p, mir-15b-5p, mir-429, and mir-221-3p) identified via network analysis as potentially relevant to psychiatric disorders, were confirmed to be significantly upregulated in both BED and BN compared with controls. Significant hypomethylation at specific CpG sites of the DAT1 gene was also observed in BED and BN groups relative to controls. Correlation analysis highlighted significant associations between specific microbiota genera, miRNA expression, and DNA methylation of DAT1 in both the BED and BN groups.

SIGNIFICANCE

Our findings provide new evidence on the role of epigenetic modifications linked to alterations in salivary microbial composition and diversity in BED and BN, opening new avenues for future research and therapeutic interventions in eating disorders targeting miRNAs and microbiota.

A curated bacterial and archaeal 16S rRNA Gene Oral Sequences dataset

In a given species, genomes and 16S rRNA gene sequences, along with their intragenomic copy numbers, can vary greatly across environments. The gene copy numbers are crucial for technologies which estimate microbial abundances based on gene counts, such as polymerase chain reaction and high-throughput sequencing. In these, taxa with fewer genes may be underestimated, while those with more genes might be overestimated. Therefore, it is essential to have accurate gene copy number databases specific to the niche under study. The 16S rRNA Gene Oral Sequences dataset (16SGOSeq) contains the number of 16S rRNA genes and their variants in the complete genomes of the bacterial and archaeal species present in the human oral cavity. It includes 3,192 complete genomes of oral bacteria and 191 complete genomes of oral archaea, from which the 16S rRNA gene sequences were extracted, and the sequence variants were identified. This oral-specific dataset of prokaryotic organisms and the pipeline followed for its construction can be applied by clinical microbiologists, bioinformaticians, or microbial ecologists in future microbiome research.

Streptococcus mutans-derived extracellular vesicles promote skin wound healing via tRNA cargo

BACKGROUND

The human oral cavity harbors a diverse microbiota, including Streptococcus species. Oral mucosal wounds heal rapidly, although the exact cause remains unclear. This study investigates the impact of Streptococcus mutans-derived extracellular vesicles (Sm EVs) on wound healing in both oral mucosal organoids and mouse skin. To explore whether microbial EV RNA cargo influences wound healing, RNA sequences from Sm EVs were identified, and the most abundant sequences were synthesized into oligomers and encapsulated in E. coli EVs (Ec EVs) for further in vivo testing. We assessed the role of Toll-like receptor 3 (TLR3) in the wound healing mechanism in TLR3 knockout (KO) mice.

RESULTS

Sm EVs significantly enhanced cell proliferation and migration in oral mucosa, with enhanced focal adhesion complex formation. Sm EVs improved wound healing in mouse dorsal skin compared to PBS controls. RNA sequencing revealed that bacterial tRNAs, particularly the tRNA-Met variant (Oligo 1), were the most abundant RNAs in Sm EVs. Ec EVs carrying Oligo 1 produced similar wound healing effects to Sm EVs in mucosal organoids and mouse dorsal skin. However, in TLR3 knockout mice, Oligo 1 did not improve wound healing.

CONCLUSIONS

This study highlights the role of Sm EVs, particularly their tRNA variants, in promoting skin wound healing through a TLR3-dependent mechanism. These findings suggest that EVs from oral commensal bacteria may offer therapeutic potential for chronic, non-healing skin wounds.

Oro-pharyngeal mucosal microbiome alternations causing immune system dysregulation in schizophrenia

Schizophrenia is a chronic and thoughtful psychological disorder that affects a person's thinking, feelings, and behaviours. Multi-factorial genetic, environmental, and neurological variables cause it. Recently, more research focused on the human microbiome, which alters the immune system and develops adverse health effects on the human body. The study discusses a possible relationship between the oropharyngeal microbiome and schizophrenia. According to recent studies, the oropharyngeal microbiome may alter the immune system in the human body and cause various psychiatric disorders, including schizophrenia. The oropharyngeal microbiome can cause schizophrenia either by affecting the genes, chromosomes, and immune system in the human body. Additionally, it examines the combined mechanism of how the oropharyngeal microbiome's alterations lead to genetic abnormalities and immune dysregulation in schizophrenia. By combining the various approaches, this chapter offers a comprehensive view of the oropharyngeal microbiome's role in schizophrenia and suggests that microbial alterations could serve as biomarkers or therapeutic targets for the disorder.

When oral health affects overall health: biofilms, dental infections, and emerging antimicrobial strategies

Dental health is a crucial component of overall health, yet it is frequently overlooked in discussions about well-being. This article explores the multifaceted aspects of dental infections, primarily focusing on biofilms formed by pathogenic bacteria such as Streptococcus mutans and Porphyromonas gingivalis. These biofilms contribute to dental caries and periodontal disease, conditions that affect oral health and have systemic consequences. Recent advancements in understanding biofilm formation and interactions have led to novel strategies for prevention and treatment, including using nanoparticles and smart hydrogels designed to disrupt biofilm integrity while promoting biocompatibility with human tissues. Furthermore, the article highlights the potential of natural remedies, including herbal extracts, as adjuncts in maintaining oral hygiene and combating microbial infections. A comprehensive overview of biofilm dynamics, including adhesion, maturation, and dispersion, is presented, alongside discussions on innovative therapeutic approaches addressing the limitations of conventional treatments. Ultimately, this article emphasizes the importance of maintaining dental health in preventing a wide spectrum of health issues, reinforcing that the mouth is a gateway to the body.

The Oral-Gut Microbiome-Brain Axis in Cognition

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and neuronal loss, affecting millions worldwide. Emerging evidence highlights the oral microbiome-a complex ecosystem of bacteria, fungi, viruses, and protozoa as a significant factor in cognitive health. Dysbiosis of the oral microbiome contributes to systemic inflammation, disrupts the blood-brain barrier, and promotes neuroinflammation, processes increasingly implicated in the pathogenesis of AD. This review examines the mechanisms linking oral microbiome dysbiosis to cognitive decline through the oral-brain and oral-gut-brain axis. These interconnected pathways enable bidirectional communication between the oral cavity, gut, and brain via neural, immune, and endocrine signaling. Oral pathogens, such as Porphyromonas gingivalis, along with virulence factors, including lipopolysaccharides (LPS) and gingipains, contribute to neuroinflammation, while metabolic byproducts, such as short-chain fatty acids (SCFAs) and peptidoglycans, further exacerbate systemic immune activation. Additionally, this review explores the influence of external factors, including diet, pH balance, medication use, smoking, alcohol consumption, and oral hygiene, on oral microbial diversity and stability, highlighting their role in shaping cognitive outcomes. The dynamic interplay between the oral and gut microbiomes reinforces the importance of microbial homeostasis in preserving systemic and neurological health. The interventions, including probiotics, prebiotics, and dietary modifications, offer promising strategies to support cognitive function and reduce the risk of neurodegenerative diseases, such as AD, by maintaining a diverse microbiome. Future longitudinal research is needed to identify the long-term impact of oral microbiome dysbiosis on cognition.

Association between oral microbiome and sleep disorders in U.S. adults: analysis of NHANES database 2009-2012

BACKGROUND

The microbiome, especially the gut microbiome, contributes to the regulation, etiology, and pathogenesis of sleep disorder. However, limited evidence regarding the oral microbiome's role in sleep disorder. Therefore, this study aimed to investigate the association between sleep disorder and oral microbial diversity and whether oral microbiota is associated with all-cause mortality in people with sleep disorder.

METHODS

The study included 4,729 individuals in the National Health and Nutrition Examination Survey (NHANES) from 2009 to 2012 and mortality data until 2019. Sleep disorder was assessed by structured questionnaire. The oral microbiome was characterized by 16 S ribosomal RNA gene sequencing. Logistic regression models were conducted to quantify the association of α-diversity with different sleep status controlling for potential confounding variables, and principal coordinate analysis along with permutational multivariate analysis of variance for β-diversity. The association between the oral microbiome and all-cause mortality was assessed using Cox proportional hazard models.

RESULTS

The α-diversity showed that a lower number of operational taxonomic units (OTUs) (adjusted odds ratio [aOR] = 0.996; 95% confidence interval [CI] = 0.994-0.998), less Faith's phylogenetic diversity (aOR = 0.954, 95% CI = 0.934-0.975), and a lower Shannon-Weiner index (aOR = 0.854, 95% CI = 0.772-0.944) were associated with sleep disorder. β-diversity revealed different oral microbiome communities between the two groups, as measured by the Bray-Curtis dissimilarity (R2 = 0.358%, P = 0.001), unweighted UniFrac distance (R2 = 0.450%, P = 0.001) and weighted UniFrac distance (R2 = 0.709%, P = 0.001). Furthermore, the OTUs (odds ratio [OR] = 0.999; 95% CI = 0.998-0.999; P < 0.05), Faith's phylogenetic diversity (OR = 0.987; 95% CI = 0.975-0.998; P < 0.05), Shannon-Weiner index (OR = 0.924; 95% CI = 0.873-0.979; P < 0.05), and the inverse Simpson index (OR = 0.553; 95% CI = 0.306-0.997; P < 0.05) were all associated with a significant increase in the risk of all-cause death in participants with sleep disorder.

CONCLUSIONS

Intra-population richness, inter-population dispersion, and the phylogenetic diversity of the oral microbiome have all been linked to sleep disorder and all-cause mortality. Overall, these results will help to better understand the etiology and pathogenesis of sleep disorder. Further studies are required to determine the mechanisms underlying the role of microbiome in the pathogenesis of sleep disorder.

Effects of Long-Term Heavy Metal Exposure on the Species Diversity, Functional Diversity, and Network Structure of Oral Mycobiome

Oral fungal homeostasis is closely related to the state of human health, and its composition is influenced by various factors. At present, the effects of long-term soil heavy metal exposure on the oral fungi of local populations have not been adequately studied. In this study, we used inductively coupled plasma-mass spectrometry (ICP-MS) to detect heavy metals in agricultural soils from two areas in Gansu Province, northwestern China. ITS amplicon sequencing was used to analyze the community composition of oral buccal mucosa fungi from local village residents. Simultaneously, the functional annotation of fungi was performed using FUNGuild, and co-occurrence networks were constructed to analyze the interactions of different functional fungi. The results showed that the species diversity of the oral fungi of local populations in the soil heavy metal exposure group was lower than that of the control population. The relative abundance of Apiotrichum and Cutaneotrichosporon was higher in the exposure group than in the control group. In addition, Cutaneotrichosporon is an Animal Pathogen, which may lead to an increased probability of disease in the exposure group. Meanwhile, there were significant differences in the co-occurrence network structure between the two groups. The control group had a larger and more stable network than the exposure group. Eight keystone taxa were observed in the network of the control group, while none were observed in that of the exposure group. In conclusion, heavy metal exposure may increase the risk of diseases associated with Apiotrichum and Cutaneotrichosporon infection in the local populations. It can also lead to the loss of keystone taxa and the reduced stability of the oral fungal network. The above results illustrated that heavy metal exposure impairs oral fungal interactions in the population. This study extends our understanding of the biodiversity of oral fungi in the population and provides new insights for further studies on the factors influencing oral fungal homeostasis.

A Potential Link Between Oral Microbiota and Female Reproductive Health

Oral cavity dysbiosis is associated with numerous inflammatory diseases, including diabetes, inflammatory bowel diseases, and periodontal disease. Changes in the oral microenvironment lead to bidirectional interactions between pathogens and individual host systems, which may induce systemic inflammation. There is increasing evidence linking the condition of the oral cavity with the most common causes of female infertility, such as polycystic ovary syndrome and endometriosis, as well as gestational complications, e.g., low birth weight, preterm delivery, and miscarriages. This review highlights the composition of the female oral microbiome in relation to infertility-related disorders, such as endometriosis and polycystic ovary syndrome, and provides a comprehensive overview of the current state of knowledge on the relationship between a dysbiotic oral microbiome, pregnancy, and its impact on the female reproductive tract.

A comparison of the alterations of oral microbiome with fixed orthodontic therapy and clear aligners: a systematic review

Aim

The oral microbiome plays a fundamental role in maintaining homeostasis of the oral cavity. In the last decade there has been an increasing use of clear aligners, which guarantee aesthetics and comfort for the patient. The aim of this work is to conduct a systematic review regarding the alterations in bacterial flora and oral health with aligner and fixed orthodontic therapy.

Design

A systematic review was conducted following the PRISMA Statement. Using the search strategy "(clear aligners OR Invisalign) AND (fixed therapy OR fixed orthodont * therapy) NOT (thermoplastic retainers) AND (oral microbiome OR oral microbiota * OR oral microbiology * OR oral health)", in the main scientific databases. Two scales were applied to assess the quality of scientific evidence: ROBINS-I and RoB 2.

Results

A total of 484 articles emerged of which 9 met our inclusion/exclusion criteria. Afterwards the application of the rating scales, 1 article was found to be at low risk of bias, 6 at moderate and 2 at serious risk of bias.

Conclusion

Both therapies cause an alteration of the oral microbiome, but the changes induced by the aligners seem to be compatible with a better oral health compared to fixed appliances.

Levilactobacillus brevis CD2 as a multifaceted probiotic to preserve oral health: results of a double-blind, randomized, placebo-controlled trial in healthy adults

BACKGROUND

A growing number of in vitro and in vivo studies suggest the application of probiotics as a natural approach to maintaining oral health. This double-blind, randomized controlled trial aimed to evaluate the efficacy of Levilactobacillus brevis CD2 (CNCM I-5566), a multifunctional probiotic frequently used in oral medicine, in preserving or improving several recognized oral health indicators.

METHODS

Thirty consenting healthy adults were randomized to receive four lozenges per day of L. brevis CD2 probiotic (n = 15) or placebo (n = 15) over four weeks. Clinical parameters (full-mouth bleeding on probing (BoP) and plaque index (PI) scores) were recorded. Unstimulated saliva was collected to measure salivation rate, pH, and buffer capacity. Salivary biomarkers were analyzed, including glucose, D-lactate, and secretory immunoglobulins A (sIgA). Clinical and salivary parameters were assessed at baseline, after four weeks of intervention, and two weeks post-intervention. Wilcoxon rank-sum test and robust regression analysis were used for statistical comparisons. The possible mediating effect of PI on BoP changes was assessed.

RESULTS

After four weeks, the probiotic group showed significant improvements in BoP and PI compared to baseline and placebo. The probiotic group had a higher salivation rate than baseline and placebo after four weeks of treatment and washout. While changes in salivary pH were not significant, buffering capacity increased in the probiotic group after four weeks of treatment and washout. Salivary glucose and D-lactate levels were lower in the probiotic group post-treatment and after washout. sIgA values increased and remained stable after washout in the probiotic group. No adverse effects were reported.

CONCLUSIONS

The treatment with L. brevis CD2 significantly improved clinical and salivary parameters, supporting its efficacy as a probiotic for oral health.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT06457724; Registered 7 June 2024 - Retrospectively registered; https://clinicaltrials.gov/study/NCT06457724?viewType=Table&page=452&rank=4512#study-overview .

Imbalance of oral microbiome homeostasis: the relationship between microbiota and the occurrence of dental caries

BACKGROUND

Streptococcus mutans is recognized as a key pathogen responsible for the development of dental caries. With the advancement of research on dental caries, the understanding of its pathogenic mechanism has gradually shifted from the theory of a single pathogenic bacterium to the theory of oral microecological imbalance. Acidogenic and aciduric microbial species are also recognized to participate in the initiation and progression of dental caries. This study is designed to elucidate the relationship between oral microbiome dysregulation and the initiation of dental caries.

RESULTS

16 S rRNA gene sequencing of saliva and dental plaque from the Specific Pathogen Free Control group and the Specific Pathogen Free sucrose diet group revealed that a sucrose diet significantly influenced the composition of the oral microbiome. At the phylum level, the dominant microbial communities in both groups of mice were Firmicutes, Proteobacteria, Unclassified Bacteria, Actinobacteria, and Bacteroidetes. At the genus level, statistical analysis identified significant differences in the abundance of 18 genera between the two groups. The relative abundance of the Gemella genus was significantly increased in the SPF Sucrose group. The SPF Control group and the Germ-free Control group have no differential bacterial genera in the oral microbiome. Micro-CT examination of the mandibles revealed the development of dental caries in both the SPF Sucrose group and the Germ-free Sucrose group.

CONCLUSIONS

This study indicates that a dysbiotic microbial community can lead to the development of caries. Lays the foundation for further research into the etiology of dental caries.

The association between oral microbiome and gastric precancerous lesions

Gastric precancerous lesions are thought to be precursors in the occurrence and development of gastric cancer through Correa's cascade. Recent studies have investigated the association between the oral microbiome and gastric precancerous lesions. However, there has yet to be a comprehensive synthesis review of the existing literature on the relationship between oral microbiome and gastric precancerous lesions. A systematic review was conducted to characterize the literature on the association between oral microbiome and gastric precancerous lesions. The studies show that oral microbiome is dynamic in individuals with gastric precancerous lesions. Oral-derived microorganisms were colonized in the gastric precancerous lesions. Interactions between oral and gastric microbiomes affect the response of the host immunity. The abnormal proliferation of oral-associated microorganisms may be linked to the reduction of gastric acid. The present review supports the potential association between oral microbiome and gastric precancerous lesions. However, the interactions are complex and multifaceted, which require further investigation.

The Oral Microbiome in Diabetes, Arterial Hypertension, and Obesity: A Scoping Review

BACKGROUND

Changes in the oral microbiome are expected in the presence of chronic conditions such as type 2 diabetes mellitus (T2D), arterial hypertension (AH), and obesity (OB).

OBJECTIVE

We aimed to map the literature regarding oral microbiome changes in people with T2D, AH, or OB compared to those without these conditions.

METHODS

This scoping review was guided by the JBI Manual for Evidence Synthesis and reported according to the PRISMA extension for scoping reviews (PRISMA-ScR). A search strategy was developed and adapted to five databases (Embase, LILACS, PubMed, Scopus, and Web of Science) and gray literature (Google Scholar and ProQuest Dissertation and Thesis). Two reviewers individually screened studies for inclusion. Data from the studies, including the molecular method to evaluate the microbiome and the type of sample, were extracted and analyzed. The focus was significant changes in phylum and genera.

RESULTS

A total of 1413 records were retrieved from databases, 86 from gray literature, and 7 from reference lists. After the screening process, 50 records were included, 28 on T2D, 8 on AH, and 12 on OB. Two studies addressed metabolic syndromes. Most studies identified the oral microbiome in saliva using 16S rRNA amplicon sequencing.

CONCLUSION

At the phylum level, Fusobacteria was enriched in ≥3 studies in people with T2D. Firmicutes enrichment was associated with T2D and OB. Genera enriched in T2D comprised Catonella, Leptotrichia, Prevotella, and Rothia. Aggregatibacter and Prevotella were enriched in OB. No phylum or genera were consistently enriched in AH.OSF protocol registration: DOI 10.17605/OSF.IO/XK72V (available at https://osf.io/z5fp4 ).

Comparative Genome Analysis of Canine Frederiksenia canicola Isolates

Background/Objectives: The One Health approach is crucial for managing and controlling the spread of antimicrobial resistance. Frederiksenia canicola is a recently identified bacterial species that seems to be a component of the oral microbiota of dogs; however, its pathogenic nature is questionable. Methods: In this study, the antibacterial susceptibility of F. canicola isolates was determined using the disk diffusion and broth microdilution methods. Genome-wide comparative analyses were performed to identify the genetic factors driving virulence and antimicrobial drug resistance (e.g., virulence factors, antimicrobial resistance genes (ARGs) and prophage-related sequences). Results: Most of the F. canicola isolates lacked virulence-associated genes. F. canicola is likely resistant to clindamycin, lincomycin and neomycin, but susceptible to penicillin, erythromycin and enrofloxacin. Antimicrobial resistance genes were not found in the F. canicola genomes, but prophage-related sequences were identified, suggesting its potential in the transfer of genes associated with drug resistance between bacteria in the oral microbiome. Conclusions: F. canicola is presumably a commensal organism with low virulence potential, as evidenced by the absence of virulence-associated genes. As F. canicola can colonize a wide range of hosts, including humans, further investigation with a greater number of isolates is needed to better understand the role of F. canicola in disease development and the spread of drug resistance.

Association between oral microbiome diversity and all-cause mortality: a longitudinal study of NHANES, 2009-2012

OBJECTIVE

The study investigates the association between oral microbiome diversity and all-cause mortality.

DESIGN

Population-based cohort study.

SETTING

US National Health and Nutrition Examination Survey (2009-2010 and 2011-2012).

PARTICIPANTS

A total of 8224 participants who had valid data on the oral microbiome diversity and survival through 31 December 2019 were included in this study.

PRIMARY AND SECONDARY OUTCOME MEASURES

Oral microbiome diversity was measured using the observed number of amplicon sequence variant (ASV) and grouped into quartiles. Cox proportional hazards regression models were used to estimate the HR and 95% CI for all-cause mortality according to the quartiles of ASV number, adjusted for potential confounders.

RESULTS

Among the 8224 participants (mean (SD) age: 42.0 (15.1) years; 49.9% male; 37.2% white, 23.8% black, 27.2% Hispanic and 11.8% other race/ethnicity), the median follow-up time was 108 months (IQR, 95-120 months) and 429 (5.2%) deaths were identified. Participants with a higher ASV number were more likely to be poor, non-Hispanic black or Hispanic, uninsured and current smokers, more likely to have poor self-rated oral health and periodontitis and less likely to use dental floss. However, compared with the lowest quartile of the ASV number, a suggestive association was observed for the second quartile (HR=0.80, 95% CI: 0.60 to 1.08), a significant reduction in all-cause mortality was observed for the third (HR=0.55, 95% CI: 0.37 to 0.82) and the fourth (HR=0.58, 95% CI: 0.38 to 0.89) quartile. The dose-response association for all-cause mortality risk was curvilinear; the protective association plateaued when the number of ASVs was larger than 120.

CONCLUSION

Despite being linked to greater socioeconomic disadvantages and poorer oral health, higher oral microbiome diversity was significantly associated with a substantial reduction in all-cause mortality.

A pilot study of the relationship between salivary microbial characteristics and endocrine and immune function in patients with burning mouth syndrome

OBJECTIVES

To explore the potential role of oral bacteria in the pathogenesis of burning mouth syndrome (BMS).

MATERIALS AND METHODS

Fifteen patients with BMS and 15 healthy controls were enrolled in this study. The relative abundance and diversity of salivary bacterial strains were analyzed using metagenomic DNA sequencing. The functionality of non-redundant genes was obtained by comparing the mmseqs2 with the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. BMS relating salivary protein markers were detected using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Partial least-squares discriminant analysis (PLS-DA) revealed that the salivary bacterial profiles of the BMS group (mean age: 38.9 ± 2.2 years) differed significantly from those of the control group (mean age: 34.1 ± 2.3 years) in terms of the abundance of dominant phyla, classes, orders, families, genera and species. Functional analysis revealed distinct endocrine and immune functions in the BMS group. The salivary cortisol and α-amylase levels were significantly higher, and salivary interleukn-6 levels were significantly lower in the BMS group than in the control group. Species contribution analysis of endocrine and immune functions revealed that Streptococcus mitis was an important contributor to endocrine and immune functions in the BMS group.

CONCLUSIONS

Salivary dysbiosis related to endocrine and immune functions may be a possible cause of BMS.

CLINICAL RELEVANCE

These findings could assist in the diagnosis and therapy of BMS.

CLINICAL TRIAL NUMBER

Not applicable.

Crosstalk between periodontitis and cardiovascular risk

Recent demographic developments resulted in an aged society with a rising disease burden of systemic and non-communicable diseases (NCDs). In cardiovascular disease (CVD), a NCD with high morbidity and mortality, recent preventive strategies include the investigation of comorbidities to reduce its significant economic burden. Periodontal disease, an oral bacterial-induced inflammatory disease of tooth-supporting tissue, is regulated in its prevalence and severity by the individual host response to a dysbiotic oral microbiota. Clinically, both NCDs are highly associated; however, shared risk factors such as smoking, obesity, type II diabetes mellitus and chronic stress represent only an insufficient explanation for the multifaceted interactions of both disease entities. Specifically, the crosstalk between both diseases is not yet fully understood. This review summarizes current knowledge on the clinical association of periodontitis and CVD, and elaborates on how periodontitis-induced pathophysiological mechanisms in patients may contribute to increased cardiovascular risk with focus on atherosclerosis. Clinical implications as well as current and future therapy considerations are discussed. Overall, this review supports novel scientific endeavors aiming at improving the quality of life with a comprehensive and integrated approach to improve well-being of the aging populations worldwide.

ORAL MICROBIOME OF BENNETT'S (NOTAMACROPUS RUFOGRISEUS) AND YELLOW-FOOTED (PETROGALE XANTHOPUS) ROCK WALLABIES AND THE IMPACT OF INTRAORAL DISEASE

Intraoral disease, including macropod progressive periodontal disease, is one of the leading causes of morbidity and mortality for wallabies under human care. Clinical signs associated with intraoral disease vary, and diagnostic findings can be difficult to interpret without intraoral radiographs or advanced imaging; therefore, this disease process can be challenging to detect in its early stages. Previous studies have investigated the effects of intraoral disease on the normal oral microbiome of various domestic species. Results from these studies demonstrate specific changes to the oral microbiome that have the potential to be used as an early indicator of intraoral disease. The purpose of this study was to evaluate the oral microbiome of 12 Bennett's wallabies (Notamacropus rufogriseus) and 3 yellow-footed rock wallabies (Petrogale xanthopus), using next-generation sequencing, to determine if intraoral disease influences the oral microbiome, as demonstrated in other species. The study identified a total of 295 bacterial species and 388 fungal species from the oral cavity of 15 wallabies. Although not statistically significant, the results of the study suggest an increase in the number of anaerobic bacterial species in sites of disease, including Actinomyces bowdenii, a species from the family Propionibacteriaceae, Peptostreptococcus canis, Fretibacterium sp., and Synergistes jonesii. It also revealed a decrease in microbial diversity in animals with active intraoral disease compared with animals without active disease, as well as at the site of disease compared with the control site. Results from this study support the findings of similar studies assessing the oral microbiome of macropods. Additional studies are warranted to better understand the normal oral microbiome of Bennett's and yellow-footed rock wallabies and the dynamic changes in the microbiome that occur in animals with intraoral disease.

The salivary microbiome and oral health status in HBeAg-negative chronic hepatitis B

Background/purpose

Dysbiosis of oral microbiota has been reported in late stage of chronic hepatitis B (CHB) infection with cirrhosis. CHB is characterized by the constant virus-induced liver injury which may lead to liver cirrhosis and hepatocellular carcinoma (HCC). However, some patients show normal liver function without antiviral treatment, associating with favourable prognosis. The oral microbiota composition and oral health status in these patients is unidentified.

Materials and methods

The study focuses on the composition of oral microbiota and oral health status in individuals with CHB and HBV vaccinees as controls. The CHB patients were hepatitis B 'e' antigen (HBeAg)-negative, with or without elevated liver enzyme increase at time of sampling, The 16S rRNA high-throughput sequencing and bioinformatic analysis were applied to investigate oral bacterial diversity, and oral examination including decay-missing-filled teeth (DMFT) index, probing depth (PD) and mucosal status was performed, along with oral health questionnaire, to assess the oral health status in CHB patients and healthy controls.

Results

Our results indicate that their oral microbiome compositions are not significantly different though some have increased ALT/AST liver enzyme levels at the time of sampling, compared to the healthy control participants who are vaccinated e.g. protected from this viral disease. CHB patients here bore a good oral health status and life-style habits as comparing to healthy controls.

Conclusion

These findings suggest that a health-associated salivary microflora is present in CHB without severe liver injury. Continued regular dental health and lifestyle support in liver disease patients is therefore justified.

The Oral-Gut-Brain Axis: The Influence of Microbes as a Link of Periodontitis With Ischemic Stroke

Periodontitis, a non-communicable chronic inflammation disease resulting from dysbiosis of the oral microbiota, has been demonstrated to have a positive association with the risk of ischemic stroke (IS). The major periodontal pathogens contribute to the progression of stroke-related risk factors such as obesity, diabetes, atherosclerosis, and hypertension. Transcriptional changes in periodontitis pathogens have been detected in oral samples from stroke patients, suggesting a new conceptual framework involving microorganisms. The bidirectional regulation between the gut and the central nervous system (CNS) is mediated by interactions between intestinal microflora and brain cells. The connection between the oral cavity and gut through microbiota indicates that the oral microbial community may play a role in mediating complex communication between the oral cavity and the CNS; however, underlying mechanisms have yet to be fully understood. In this review, we present an overview of key concepts and potential mechanisms of interaction between the oral-gut-brain axis based on previous research, focusing on how the oral microbiome (especially the periodontal pathogens) impacts IS and its risk factors, as well as the mediating role of immune system homeostasis, and providing potential preventive and therapeutic approaches.

A Randomized Clinical Study of a Curcumin and Melatonin Toothpaste Against Periodontal Bacteria

Background: The mouth and the oropharyngeal system are home to numerous bacterial species that constitute the so-called oral microbiome and play an important role for the integrity of the oral cavity, influencing the overall health of the body, as demonstrated by several studies. The aim of this study was to evaluate the bacterial modulation potential of a toothpaste (bioredoxin) containing curcumin and melatonin. Both substances have anti-inflammatory properties, as documented in several scientific reports. Methods: The in vivo study we present was a single-center, double-blind trial and was conducted in parallel groups. We enlisted 20 volunteers who were randomly assigned to four distinct groups using blinded four different toothpaste preparations: a standard toothpaste indicated as placebo, a toothpaste with curcumin, a toothpaste with melatonin, and a toothpaste with melatonin and curcumin. Results: The samples from the gingival tasks were taken at time 0 and after 8 weeks of toothpaste treatment. By evaluating the DNA content of the most significant periodontal bacteria related to the total bacteria count using quantitative PCR assays, including the saprophyte component of the microbiome, we demonstrated that the Curcumin and Melatonin treatment has a statistically relevant effect on decreasing the level of periodontal pathogenic bacteria DNA. The toothpaste with the addition of curcumin and melatonin showed a modulation between t0 and t1 of the Campylobacter rectus (14,568 vs. 3532.8) and Peptostreptococcus micro (1320.8 vs. 319) bacteria. In addition, a modulation of pathogenic bacteria and saprophytic bacteria was shown. The synergistic action of the two additives would therefore appear to lead to promising results. Conclusions: Despite the fact that additional studies may be necessary in evaluating the effect of the Curcumin/melatonin combination in modulating a proposed therapeutic effect on infections of the oropharyngeal apparatus, in this report, we show for the first time that a combination of curcumin and melatonin supplemented using an oral cosmetic vehicle has the capacity to decrease the level of periodontal pathogenic bacteria, possibly ameliorating health and the physiological conditions in the buccal scenario.

In Vitro Efficacy of Domestic Techniques for Disinfection of Toothbrushes Contaminated With Enterococcus faecalis

Introduction: Oral hygiene education for patients is fundamental in preventive-promotional dentistry. The disinfection of toothbrushes (TBs) must be integrated into this context due to their proximity to contaminant sources that make them vulnerable to cross infection in homes. The objective of this study was to compare the efficacy of domestic techniques for disinfection of TBs. Materials and Methods: We performed an in vitro study of 76 TBs contaminated with Enterococcus faecalis (Ef) ATCC 29212 subjected to different disinfection protocols: G1. Distilled water (DW; negative control; n = 8), G2. Dimethylsulfoxide (DMSO)10% (negative control; n = 8), G3. Chlorhexidine (CHX) 0.12% (positive control; n = 15), G4. 100% white vinegar (WV; n = 15), G5. Microwave (MW) at 700 W (n = 15), and G6. 200 mg/mL of certified alcoholic extract of purple garlic (GARLIC) from Arequipa (Allium sativum L; n = 15). Bacterial count was assessed by colony-forming units (CFU/mL) categorized as contamination: low (<30), medium (30-300), and high (>300). The Kruskal-Wallis test with post hoc pairs was used at a significance level of p < 0.05. Results: Efficacy against Ef showed highly significant differences between groups (p < 0.001) with lower median CFU/mL in G3 and G4 (Me = 0 [IQR (interquartile range) = 0]: low) and G5 (Me = 6000 [IQR = 45,000]: low/medium) versus negative controls (Me = 378,500 and 5,020,000 [IQR = 4,605,000 and 6,760,000]: medium/high; p ≤ 0.019). The counts of the G5 were not statistically different than G3, G4, and G6 (p > 0.06). The G6 (Me = 1,510,000 [IQR = 590,000]: medium) was inferior to G3 and G4 (p < 0.001), but similar to both negative control groups (p > 0.999). Conclusions: Disinfection of TBs with CHX, WV, and MWs produces a significant effective reduction in the count of Ef.

Metagenomic Study Reveals Phage-Bacterial Interactome Dynamics in Gut and Oral Microbiota in Pancreatic Diseases

Individuals with pancreatic-related health conditions usually show lower diversity and different composition of bacterial and viral species between the gut and oral microbiomes compared to healthy individuals. We performed a thorough microbiome analysis, using deep shotgun sequencing of stool and saliva samples obtained from patients with chronic pancreatitis (CP), pancreatic ductal adenocarcinoma (PDAC), and healthy controls (HCs).We observed similar microbiota composition at the species level in both the gut and oral samples in PDAC patients compared to HCs, among which the most distinctive finding was that the abundance of oral-originated Fusobacterium nucleatum species did not differ between the oral and the gut samples. Moreover, comparing PDAC patients with HCs, Klebsiella oxytoca was significantly more abundant in the stool samples of PDAC patients, while Streptococcus spp. showed higher abundance in both the oral and stool samples of PDAC patients. Finally, the most important finding was the distinctive gut phage-bacterial interactome pattern among PDAC patients. CrAssphages, particularly Blohavirus, showed mutual exclusion with K. oxytoca species, while Burzaovirus showed co-occurrence with Enterobacteriaceae spp., which have been shown to be capable of inducing DNA damage in human pancreatic cells ex vivo. The interactome findings warrant further mechanistic studies, as our findings may provide new insights into developing microbiota-based diagnostic and therapeutic methods for pancreatic diseases.

Characterization of lingual microbiota in pediatric geographic tongue

BACKGROUND

Geographic tongue is an oral mucosal lesion affecting the tongue. The association between geographic tongue and the mucosal microbiota in children remains unclear.

METHOD

To characterize the feature of lingual microbiota in pediatric geographic tongue, lingual swabs were collected from lesion sites and healthy sites of 25 patients with geographic tongue (14 males and 11 females; age 5.21 ±2.94 years) and 19 controls (10 males and 9 females; age 5.31±2.82 years). DNA was extracted and the 16S rRNA was amplificated, sequenced and analyzed.

RESULTS

The lingual microbiota composition was significantly different between children with geographic tongue and the healthy cohort; Streptobacillus was reduced in geographic tongue, while Catonella, Bacillus and Oribacterium were overrepresented. When the lesions and the normal mucosa were compared, an increased abundance of Prevotella oris was observed.

CONCLUSION

Our results provided new insight into the association between oral microbiota and pediatric geographic tongue.

Acquired pellicle and biofilm engineering with CaneCPI-5: Insights from proteomic and microbiomics analysis

OBJECTIVE

In this in vivo proof-of-concept study, acquired pellicle engineering was implemented to promote alterations in the protein composition of the acquired enamel pellicle (AEP) and the bacterial composition of the dental biofilm after treatment with Sugarcane cystatin (CaneCPI-5).

DESIGN

After prophylaxis, 10 volunteers rinsed (10 mL, 1 min) with the following solutions: 1) deionized water (H2O- negative control or 2) 0.1 mg/mL CaneCPI-5. The AEP and biofilm were formed along 2 or 3 h, respectively. The AEP was collected with electrode filter papers soaked in 3 % citric acid. After protein extraction, samples were analyzed by quantitative shotgun label-free proteomics. The biofilm microbiome was collected with a dental curette. The DNA was extracted, amplified, and analyzed by 16S-rRNA Next Generation Sequencing (NGS).

RESULTS

Treatment with CaneCPI-5 increased several proteins with antimicrobial, acid-resistance, affinity for hydroxyapatite, structural and calcium binding properties, such as Cysteine-rich-3 (6-fold-p = 0.03), Cystatin-B (5.5-fold-p < 0.01), Neutrophil-defensin 1 (4.7-fold-p < 0.01), Mucin (3.9-fold-p < 0.01), Immunoglobulin-heavy-constant (3.8-fold-p < 0.01) and Lactotransferrin (2.8-fold-p < 0.01). Microbiome revealed that several commensal bacteria had their abundance increased after rinsing with CaneCPI-5, such as Corynebacterium and Neisseria, while Streptococcus and Prevotella nigrescens were decreased. The results indicate the efficiency of CaneCPI-5 in promoting beneficial changes in the AEP and biofilm, making this phytocystatin a potential target for incorporation into dental products.

CONCLUSION

Cane demonstrated the capability to alter the protein composition of the acquired enamel pellicle (AEP) and the initial colonizers of the biofilm, enhancing the presence of proteins and bacteria crucial for dental protection.

The oral organ: A new vision of the mouth as a whole for a gerophysiological approach to healthy aging

This article brings a new perspective on oral physiology by presenting the oral organ as an integrated entity within the entire organism and its surrounding environment. Rather than considering the mouth solely as a collection of discrete functions, this novel approach emphasizes its role as a dynamic interphase, supporting interactions between the body and external factors. As a resilient ecosystem, the equilibrium of mouth ecological niches is the result of a large number of interconnected factors including the heterogeneity of different oral structures, diversity of resources, external and internal pressures and biological actors. The manuscript seeks to deepen the understanding of age-related changes within the oral cavity and throughout the organism, aligning with the evolving field of gerophysiology. The strategic position and fundamental function of the mouth make it an invaluable target for early prevention, diagnosis, treatment, and even reversal of aging effects throughout the entire organism. Recognizing the oral cavity capacity for sensory perception, element capture and information processing underscores its vital role in continuous health monitoring. Overall, this integrated understanding of the oral physiology aims at advancing comprehensive approaches to the oral healthcare and promoting broader awareness of its implications on the overall well-being.

Metatranscriptome and Resistome of the Endodontic Microbiome

INTRODUCTION

In this study, we used metatranscriptomics for the first time to investigate microbial composition, functional signatures, and antimicrobial resistance gene expression in endodontic infections.

METHODS

Root canal samples were collected from ten teeth, including five primary and five persistent/secondary endodontic infections. RNA from endodontic samples was extracted, and RNA sequencing was performed on a NovaSeq6000 system (Illumina). Taxonomic analysis was performed using the Kraken2 bacterial database. Then, sequences with a taxonomic classification were annotated against the Universal Protein Knowledgebase for functional annotation and the Comprehensive Antibiotic Resistance Database for AR-like gene identification.

RESULTS

Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria represented the dominant phyla, whereas Fusobacteria, Spirochetes, and Synergistetes were among the nondominant phyla. The top ten species were mainly represented by obligate (or quasiobligate) anaerobes, including Gram-negative (eg, Capnocytophaga sp. oral taxon 323, Fusobacterium nucleatum, Prevotella intermedia, Prevotella oris, Tannerella forsythia, and Tannerella sp. oral taxon HOT-286) and Gram-positive species (eg, Olsenella uli and Parvimonas micra). Transcripts encoding moonlighting proteins (eg, glycolytic proteins, translational elongation factors, chaperonin, and heat shock proteins) were highly expressed, potentially affecting bacterial adhesion, biofilm formation, host defense evasion, and inflammation induction. Endodontic bacteria expressed genes conferring resistance to antibiotic classes commonly used in dentistry, with a high prevalence and expression of tetracycline and lincosamide resistance genes. Antibiotic efflux and antibiotic target alteration/protection were the main resistance mechanisms.

CONCLUSIONS

Metatranscriptomics revealed the activity of potential endodontic pathogens, which expressed putative virulence factors and a wide diversity of genes potentially involved in AR.

Oral microbiome and its relationship with oral cancer

ABSTRACT

As the initial point for digestion, the balance of oral microorganisms plays an important role in maintaining local and systemic health. Oral dysbiosis, or an imbalance in the oral microbial community, may lead to the onset of various diseases. The presence or abnormal increase of microbes in the oral cavity has attracted significant attention due to its complicated relationship with oral cancer. Oral cancer can remodel microbial profiles by creating a more beneficial microenvironment for its progression. On the other hand, altered microbial profiles can promote tumorigenesis by evoking a complex inflammatory response and affecting host immunity. This review analyzes the oncogenic potential of oral microbiome alterations as a driver and biomarker. Additionally, a potentially therapeutic strategy via the reversal of the oral microbiome dysbiosis in oral cancers has been discussed.

Insights from metagenomics into gut microbiome associated with acute coronary syndrome therapy

Acute coronary syndrome (ACS) is a predominant cause of mortality, and the prompt and precise identification of this condition is crucial to minimize its impact. Recent research indicates that gut microbiota is associated with the onset, progression, and treatment of ACS. To investigate its role, we sequenced the gut microbiota of 38 ACS patients before and after percutaneous coronary intervention and statin therapy at three time points, examining differential species and metabolic pathways. We observed a decrease in the abundance of Parabacteroides, Escherichia, and Blautia in patients after treatment and an increase in the abundance of Gemalla, Klebsiella variicola, Klebsiella pneumoniae, and others. Two pathways related to sugar degradation were more abundant in patients before treatment, possibly correlated with disorders of sugar metabolism and risk factors, such as hyperglycemia, insulin resistance, and insufficient insulin secretion. Additionally, seven pathways related to the biosynthesis of vitamin K2 and its homolog were reduced after treatment, suggesting that ACS patients may gradually recover after therapy. The gut microbiota of patients treated with different statins exhibited notable differences after treatment. Rosuvastatin appeared to promote the growth of anti-inflammatory bacteria while reducing pro-inflammatory bacteria, whereas atorvastatin may have mixed effects on pro-inflammatory and anti-inflammatory bacteria while increasing the abundance of Bacteroides. Our research will provide valuable insights and enhance comprehension of ACS, leading to better patient diagnosis and therapy.

From Gut Microbiota to Brain Waves: The Potential of the Microbiome and EEG as Biomarkers for Cognitive Impairment

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder and a leading cause of dementia. Aging is a significant risk factor for AD, emphasizing the importance of early detection since symptoms cannot be reversed once the advanced stage is reached. Currently, there is no established method for early AD diagnosis. However, emerging evidence suggests that the microbiome has an impact on cognitive function. The gut microbiome and the brain communicate bidirectionally through the gut-brain axis, with systemic inflammation identified as a key connection that may contribute to AD. Gut dysbiosis is more prevalent in individuals with AD compared to their cognitively healthy counterparts, leading to increased gut permeability and subsequent systemic inflammation, potentially causing neuroinflammation. Detecting brain activity traditionally involves invasive and expensive methods, but electroencephalography (EEG) poses as a non-invasive alternative. EEG measures brain activity and multiple studies indicate distinct patterns in individuals with AD. Furthermore, EEG patterns in individuals with mild cognitive impairment differ from those in the advanced stage of AD, suggesting its potential as a method for early indication of AD. This review aims to consolidate existing knowledge on the microbiome and EEG as potential biomarkers for early-stage AD, highlighting the current state of research and suggesting avenues for further investigation.

Comprehensive analysis of the oral microbiota and metabolome change in patients of burning mouth syndrome with psychiatric symptoms

Background

Burning mouth syndrome (BMS) is a chronic idiopathic facial pain with intraoral burning or dysesthesia. BMS patients regularly suffer from anxiety/depression, and the association of psychiatric symptoms with BMS has received considerable attention in recent years. The aims of this study were to investigate the potential interplay between psychiatric symptoms and BMS.

Methods

Using 16S rRNA sequencing and liquid chromatography-mass spectrometry (LC/MS) to evaluate the oral microbiota and saliva metabolism of 40 BMS patients [including 29 BMS patients with depression or anxiety symptoms (DBMS)] and 40 age matched healthy control (HC).

Results

The oral microbiota composition in BMS exhibited no significant differences from HC, although DBMS manifested decreased α-diversity relative to HC. Noteworthy was the discernible elevation in the abundance of proinflammatory microorganisms within the oral microbiome of individuals with DBMS. Parallel findings in LC/MS analyses revealed discernible disparities in metabolites between DBMS and HC groups. Principal differential metabolites were notably enriched in amino acid metabolism and lipid metabolism, exhibiting associations with infectious and immunological diseases. Furthermore, the integrated analysis underscores a definitive association between the oral microbiome and metabolism in DBMS.

Conclusions

This study suggests possible future modalities for better understanding the pathogenesis and personalized treatment plans of BMS.

Update on Focal Infection Management: A Czech Interdisciplinary Consensus

BACKGROUND

The focal infection theory has been used to explain several chronic systemic diseases in the past. Systemic diseases were thought to be caused by focal infections, such as caries and periodontal diseases, and dentists were held responsible for these diseases due to the spread of oral infections. As knowledge of the interrelationship between oral microorganisms and the host immune response has evolved over the last few decades, the focal infection theory has been modified in various ways. The relationship between oral and systemic health appears to be more complex than that suggested by the classical theory of focal infections. Indeed, the contribution of the oral microbiota to some systemic diseases is gaining acceptance, as there are strong associations between periodontal disease and atherosclerotic vascular disease, diabetes, and hospital-associated pneumonia, amongst others. As many jurisdictions have various protocols for managing this oral-systemic axis of disease, we sought to provide a consensus on this notion with the help of a multidisciplinary team from the Czech Republic.

METHODS

A multidisciplinary team comprising physicians/surgeons in the specialities of dentistry, ear-nose and throat (ENT), cardiology, orthopaedics, oncology, and diabetology were quetioned with regard to their conceptual understanding of the focal infection theory particularly in relation to the oral-systemic axis. The team also established a protocol to determine the strength of these associations and to plan the therapeutic steps needed to treat focal odontogenic infections whenever possible.

RESULTS

Scoring algorithms were devised for odontogenic inflammatory diseases and systemic risks, and standardised procedures were developed for general use.

CONCLUSIONS

The designed algorithm of the oral-systemic axis will be helpful for all health care workers in guiding their patient management protocol.

Evaluation of the Oral Microbiome before and after Treatments for Halitosis with Photodynamic Therapy and Probiotics-Pilot Study

BACKGROUND

To compare photodynamic therapy and the use of probiotics in reducing halitosis assessed through gas chromatography and microbiome analysis.

METHODS

Participants aged from 18 to 25 years showing sulfide (SH2) ≥ 112 ppb on gas chromatography were selected. They were divided into four treatment groups: Group 1-Tongue Scraping; Group 2-Antimicrobial Photodynamic Therapy (aPDT); Group 3-Probiotics; and Group 4-Antimicrobial Photodynamic Therapy (aPDT) and Probiotics. The halimetry process was performed before, immediately after the treatments, and 7 days, 14 days, and 30 days after the initial collection. The collections for later microbiological analysis were made along with the halimetry for microbiome analysis.

RESULTS

Treatment with aPDT or probiotics under these experimental conditions was not able to change the bacteria present in the biofilm of the tongue.

CONCLUSIONS

More research is needed to know the behavior of the oral microbiome in the presence of halitosis and the effectiveness of new treatments.

Effect of Probiotic Supplements on the Oral Microbiota-A Narrative Review

Data from systematic reviews and meta-analyses show that probiotics positively impact clinical parameters of oral diseases such as gingivitis, dental caries, and periodontitis. However, the working mechanism of probiotics is not fully understood, but is hypothesized to be mediated by direct and indirect interactions with the oral microbiota and the human host. In the present narrative review, we focused on the microbiological effect of probiotic supplements based on data retrieved from randomized clinical trials (RCTs). In addition, we assessed to what extent contemporary molecular methods have been employed in clinical trials in the field of oral probiotics. Multiple RCTs have been performed studying the potential effect of probiotics on gingivitis, dental caries, and periodontitis, as evaluated by microbial endpoints. In general, results are conflicting, with some studies reporting a positive effect, whereas others are not able to record any effect. Major differences in terms of study designs and sample size, as well as delivery route, frequency, and duration of probiotic consumption, hamper comparison across studies. In addition, most RCTs have been performed with a limited sample size using relatively simple methods for microbial identification, such as culturing, qPCR, and DNA-DNA checkerboard, while high-throughput methods such as 16S sequencing have only been employed in a few studies. Currently, state-of-the-art molecular methods such as metagenomics, metatranscriptomics, and metaproteomics have not yet been used in RCTs in the field of probiotics. The present narrative review revealed that the effect of probiotic supplements on the oral microbiota remains largely uncovered. One important reason is that most RCTs are performed without studying the microbiological effect. To facilitate future systematic reviews and meta-analyses, an internationally agreed core outcome set for the reporting of microbial endpoints in clinical trials would be desirable. Such a standardized collection of outcomes would most likely improve the quality of probiotic research in the oral context.

A preliminary report on the exploration of salivary bacterial diversity by the multiplex SNaPshot assay

Salivary bacterial community composition is associated with the host's internal and environmental factors, which have potential applications in forensic practice. The 16S rRNA gene sequencing is the most commonly used strategy for detecting salivary bacterial diversity; however, its platforms are not compatible with capillary electrophoresis (CE) platforms commonly used for forensic applications. Therefore, we attempted to detect the salivary bacterial diversity using a single nucleotide polymorphism (SNP) assay. Salivary bacterial diversity varies among diverse geographic locations, making it a potential supplementary biomarker for forensic geographic sourcing. To evaluate the performance of the multiplex SNaPshot assay, saliva samples from three geographic locations in China were analyzed using the multiplex SNaPshot assay and 16S rRNA gene sequencing. We screened SNPs from two high-relative-abundance salivary genera (Streptococcus and Veillonella) to construct a multiplex SNaPshot system that can be used on the CE platform. The stability and sensitivity of the multiplex SNaPshot system were also tested. A random forest classification model was used to classify samples from different regions to explore the ability of salivary bacteria to discriminate between geographic sources. Six bacterial SNPs were screened and a multiplex SNaPshot system was constructed. The stability results showed that the typing of salivary stains that were placed indoors for different days was not affected in this study. Two-thirds of mocked salivary stain samples showed more than 90% of typing results obtained for salivary stain samples with an input of 0.1 µl saliva. The results of principal coordinate analysis based on salivary bacterial diversity showed significant differences between samples from the three different geographic locations. The accuracy of the random forest classification was 66.67% based on the multiplex SNaPshot assay and 83.33% based on the 16S rRNA gene sequencing. In conclusion, this is the first attempt to detect salivary bacterial diversity using a multiplex SNaPshot bacterial SNP assay. The geographic difference in human salivary bacterial community composition was significant, as revealed by the multiplex SNaPshot assay; however, its performance in discriminating geographic sources was lower than that of 16S rRNA gene sequencing. This strategy based on bacterial SNP loci may favor the detection of human bacterial diversity in common forensic laboratories but requires further exploration in larger sample sizes and more bacterial SNP loci.

Manual vs. interactive power toothbrush on plaque removal and salivary Streptococcus mutans and Lactobacillus casei levels : Single-center, examiner-blinded, randomized clinical trial in orthodontic patients

INTRODUCTION

The purpose of this study was to compare efficacy of a manual and an interactive power toothbrush in orthodontic patients by assessing periodontal indexes and bacterial content of saliva samples.

METHODS

Forty patients (20 females, 20 males; age range 12-18 years) with fixed orthodontic appliances were included in the study. The patients were randomly divided into two groups in a 1:1 ratio using sealed envelopes: group 1: manual toothbrush (Oral‑B Ortho Brush, Procter&Gamble Company, Dublin, Ireland), group 2: interactive power toothbrush (Oral‑B Genius 8900, Procter&Gamble Company, Marktheidenfeld, Germany). All participants were given the same toothpaste (Colgate Triple Action, Colgate-Palmolive, New York, NY, USA). The brushing procedure for each patient was described in detail, both orally and visually, utilizing a video demonstration. Plaque and bleeding index scores were recorded for both the lower and upper arches at the beginning of the study (T0) and at weeks 6 (T1) and 12 (T2). In addition, the numbers of Streptococcus (S.) mutans, Lactobacillus (L.) casei, and Porphyromonas (P.) gingivalis bacteria were determined using a real-time polymerase chain reaction (PCR) analysis in saliva samples collected at T0, T1, and T2 times. Mann-Whitney U test and Student's t test were used to compare data between the groups, and one-way analysis of variance (ANOVA) and Friedman tests were used to compare data from different time intervals for each group.

RESULTS

Plaque index values were greater in group 1 at T1 and T2, although there was no difference between the groups at T0. The gingival index scores of both groups were similar at T0, T1, and T2. While group 2 had a larger number of salivary S. mutans at T0 and T2, there was no significant difference between the groups at T1. At all three time points, there was no significant difference in salivary L. casei levels between the groups.

CONCLUSIONS

Although the interactive power toothbrush was more effective at removing plaque than the manual toothbrush, the results of the gingival index did not reflect the plaque scores. The number of certain salivary bacteria and brush type did not appear to have a clear relationship.

Spitting in the wind?-The challenges of RNA sequencing for biomarker discovery from saliva

Forensic trace contextualization, i.e., assessing information beyond who deposited a biological stain, has become an issue of great and steadily growing importance in forensic genetic casework and research. The human transcriptome encodes a wide variety of information and thus has received increasing interest for the identification of biomarkers for different aspects of forensic trace contextualization over the past years. Massively parallel sequencing of reverse-transcribed RNA ("RNA sequencing") has emerged as the gold standard technology to characterize the transcriptome in its entirety and identify RNA markers showing significant expression differences not only between different forensically relevant body fluids but also within a single body fluid between forensically relevant conditions of interest. Here, we analyze the quality and composition of four RNA sequencing datasets (whole transcriptome as well as miRNA sequencing) from two different research projects (the RNAgE project and the TrACES project), aiming at identifying contextualizing forensic biomarker from the forensically relevant body fluid saliva. We describe and characterize challenges of RNA sequencing of saliva samples arising from the presence of oral bacteria, the heterogeneity of sample composition, and the confounding factor of degradation. Based on these observations, we formulate recommendations that might help to improve RNA biomarker discovery from the challenging but forensically relevant body fluid saliva.

Standardization of the protocol for oral cavity examination and collecting of the biological samples for microbiome research using the next-generation sequencing (NGS): own experience with the COVID-19 patients

To date, publications have shown that compositions of oral microbiota differ depending on their habitats (e.g. tongue, tonsils, pharynx). The absence of set standards for the choice of the areas and conditions of material collection makes the oral microbiome one of the most difficult environments for a comparative analysis with other researchers, which is a meaningful limitation during an assessment of the potential effects of microorganisms as biomarkers in the courses of various human diseases. Therefore, standardisation of basic conditions of a dental examination and collection of material for the next generation sequencing (NGS) is worth attempting. The standardisation of the dental exam and collection of the clinical materials: saliva, swab from the tongue ridge, hard palate, palatine tonsils and oropharynx, supragingival plaque and subgingival plaque. Protocol involved the patients (n = 60), assigned to 3 groups: I-COVID-19 convalescents who received antibiotics, n = 17, II-COVID-19 convalescents, n = 23 and III-healthy individuals, n = 20. The collected biological samples were used to conduct NGS (16S rRNA). The conditions of patient preparation for collecting biological materials as well as the schedule of dental examination, were proposed. Based on the research conducted, we have indicated the dental indicators that best differentiate the group of COVID-19 patients (groups I and II) from healthy people (group III). These include the DMFT, D and BOP indices. The use of alpha and beta diversity analysis provided an overall insight into the diversity of microbial communities between specific niches and patient groups. The most different diversity between the studied group of patients (group II) and healthy people (group III) was noted in relation to the supragingival plaque. The order of activities during the dental exam as well as while collecting and securing clinical materials is particularly important to avoid technical errors and material contamination which may result in erroneous conclusions from the analyses of the results of sensitive tests such as the NGS. It has been shown that the dental indices: DMFT, D number, PI and BOP are the best prognostic parameters to assess the oral health. Based on beta diversity the most sensitive niche and susceptible to changes in the composition of the microbiota is the supragingival plaque. The procedures developed by our team can be applied as ready-to-use forms in studies conducted by other researchers.

Alcohol Consumption and the Diversity of the Oral Microbiome in Postmenopausal Women

BACKGROUND

Alcohol reduces neutrophil function and decreases salivary flow, which could affect the composition of the oral microbiome.

OBJECTIVE

We hypothesized that the α- and β-diversity of the oral microbiome and the relative abundance of bacterial taxa would differ by frequency and type of alcohol consumption.

METHODS

We used a food frequency questionnaire to assess the frequency of consumption of beer, wine, and liquor (drinks/week) in a sample of 1179 postmenopausal women in the Osteoporosis and Periodontal Disease Study. Women were categorized as nondrinkers, drinking <1 drink/wk, ≥1 to <7 drinks/wk, or ≥7 drinks/wk for total alcohol consumption and for beer, wine, and liquor consumption. The composition and diversity of the oral microbiome was assessed from subgingival plaque samples using 16S ribosomal RNA amplicon sequencing. Permutational multivariate analysis of variance (PERMANOVA) was used to examine β-diversity (between-sample diversity) in the microbiome between alcohol consumption categories. Analysis of covariance was used to examine the mean α-diversity (within-sample diversity), assessed by the Shannon index (species evenness), Chao1 index (species richness), and observed operational taxonomic unit (OTU) count and the mean relative abundance of 245 bacterial taxa across alcohol consumption categories.

RESULTS

Over half of the participants (67%) consumed alcohol, with 14% reporting ≥1 drink/d. The β-diversity across categories of total alcohol consumption, but not categories of alcohol type, was statistically significantly different (P for PERMANOVA = 0.016). Mean α-diversity measures were statistically significantly higher (P < 0.05) in the highest category of total alcohol and wine consumption compared to nondrinkers; no significant associations were found for beer or liquor consumption. The relative abundance of 1 OTU, Selenomonassp._oral_taxon_133, was significantly lower in the highest level of total alcohol consumption compared to nondrinkers after adjustment for multiple comparisons.

CONCLUSIONS

Alcohol consumption was associated with the diversity and composition of the subgingival microbiome.

Oral pathobiont Klebsiella chaperon usher pili provide site-specific adaptation for the inflamed gut mucosa

The ectopic gut colonization by orally derived pathobionts has been implicated in the pathogenesis of various gastrointestinal diseases, including inflammatory bowel disease (IBD). For example, gut colonization by orally derived Klebsiella spp. has been linked to IBD in mice and humans. However, the mechanisms whereby oral pathobionts colonize extra-oral niches, such as the gut mucosa, remain largely unknown. Here, we performed a high-density transposon (Tn) screening to identify genes required for the adaptation of an oral Klebsiella strain to different mucosal sites - the oral and gut mucosae - at the steady state and during inflammation. We find that K. aerogenes, an oral pathobiont associated with both oral and gut inflammation in mice, harbors a newly identified genomic locus named "locus of colonization in the inflamed gut (LIG)" that encodes genes related to iron acquisition (Sit and Chu) and host adhesion (chaperon usher pili [CUP] system). The LIG locus is highly conserved among K. aerogenes strains, and these genes are also present in several other Klebsiella species. The Tn screening revealed that the LIG locus is required for the adaptation of K. aerogenes in its ectopic niche. In particular, we determined K. aerogenes employs a CUP system (CUP1) present in the LIG locus for colonization in the inflamed gut, but not in the oral mucosa. Thus, oral pathobionts likely exploit distinct adaptation mechanisms in their ectopically colonized intestinal niche compared to their native niche.

Compositional and functional changes in the salivary microbiota related to oral leukoplakia and oral squamous cell carcinoma: a case control study

BACKGROUND

Oral squamous cell carcinoma (OSCC) is one of the most common malignant tumours with increasing incidence, and oral leukoplakia (OLK) has a strong tendency to undergo malignant transformation. The oral microbiota may influence oral cancer progression, but the salivary bacterial composition and functional changes in OSCC and OLK have not been comprehensively elucidated. Therefore, we compared salivary bacteria in OLK and OSCC patients with healthy controls (HC).

METHODS

Metagenomic sequencing was used to compare the bacterial composition and functional changes of 18 OSCC patients, 21 OLK patients and 21 HC. Spearman correlation was used to identify possible associations between functions and bacteria.

RESULTS

Gemella was the most differentially enriched genus in OSCC. At the species level, Streptococcus sp. NPS 308, Streptococcus agalactiae, Gemella haemolysans and Gemella morbillorum were slightly increased in OLK and OSCC. Kyoto Encyclopedia of Genes and Genomes (KEGG) results showed that OSCC was mainly associated with metabolism functions, including lipid metabolism, carbohydrate metabolism and glycan biosynthesis and metabolism. The synthesis and degradation of ketone bodies, cysteine and methionine metabolism and glycerolipid metabolism differed significantly among the three groups, and were highest in OSCC and lowest in HC. And G. haemolysans was significantly associated with these selected metabolic pathways.

CONCLUSIONS

Metagenomic analysis revealed significant differences in the salivary microbiota among OSCC, OLK and HC. Thus, salivary microbiota composition and functional changes may be associated with OSCC progression. Metabolism of nonessential amino acids such as cysteine and methionine in bacteria may play an important role in oral oncogenesis, and more studies of the mechanism between metabolisms of bacteria and oral oncogenesis are needed in the future.

Low Carbohydrate, High Fat Diet Alters the Oral Microbiome without Negating the Nitrite Response to Beetroot Juice Supplementation

A low carbohydrate, high fat (LCHF) diet in athletes increases fat oxidation but impairs sports performance, potentially due to impaired exercise economy. Dietary nitrate supplementation can improve exercise economy via an increase in nitric oxide production, which is initiated by the reduction of nitrate to nitrite within the oral cavity. This reaction is dependent on the presence of nitrate-reducing oral bacteria, which can potentially be altered by dietary changes, including a LCHF diet. This study explored the effect of a LCHF diet on the oral microbiome and subsequent changes to plasma nitrite concentration following nitrate supplementation. Following five days of LCHF or high carbohydrate (HCHO) control dietary intervention, highly trained male race walkers consumed 140 mL beetroot juice containing 8.4 mmol nitrate; they then provided (a) blood samples for plasma nitrate and nitrite analysis and (b) saliva samples for 16S rRNA sequencing of the oral microbiome. The LCHF diet (n = 13) reduced oral bacterial diversity and changed the relative abundance of the genera Neisseria (+10%), Fusobacteria (+3%), Prevotella (-9%), and Veillonella (-4%), with no significant changes observed following the HCHO diet (n = 11). Following beetroot juice ingestion, plasma nitrite concentrations were higher for the LCHF diet compared to the HCHO diet (p = 0.04). However, the absence of an interaction with the trial (pre-post) (p = 0.71) suggests that this difference was not due to the dietary intervention. In summary, we found an increase in plasma nitrate and nitrite concentrations in response to nitrate supplementation independent of diet. This suggests the oral microbiome is adaptive to dietary changes and can maintain a nitrate reduction capacity despite a decrease in bacterial diversity following the LCHF diet.

The effect of sex steroid hormones on the ecology of in vitro oral biofilms

Sex steroid hormones (SSH) such as oestrogen, progesterone and testosterone are cholesterol derived molecules that regulate various physiological processes. They are present in both blood and saliva, where they come in contact with oral tissues and oral microorganisms. Several studies have confirmed the effect of these hormones on different periodontal-disease-associated bacteria, using single-species models. Bacteria can metabolize SSH, use them as alternative for vitamin K and also use them to induce the expression of virulence factors. However, it is still unclear what the effects of SSH are on the oral microbiome. In this study, we investigated the effects of four SSH on commensal in vitro oral biofilms. Saliva-derived oral biofilms were grown in Mc Bain medium without serum or menadione using the Amsterdam Active-Attachment model. After initial attachment in absence of SSH, the biofilms were grown in medium containing either oestradiol, oestriol, progesterone or testosterone at a 100-fold physiological concentration. Menadione or ethanol were included as positive control and negative control, respectively. After 12 days with daily medium refreshments, biofilm formation, biofilm red fluorescence and microbial composition were determined. The supernatants were tested for proteolytic activity using the Fluorescence Resonance Energy Transfer Analysis (FRET). No significant differences were found in biofilm formation, red fluorescence or microbial composition in any of the tested groups. Samples grown in presence of progesterone and oestradiol showed proteolytic activity comparable to biofilms supplemented with menadione. In contrast, testosterone and oestriol showed a decreased proteolytic activity compared to biofilms grown in presence of menadione. None of the tested SSH had large effects on the ecology of in vitro oral biofilms, therefore a direct translation of our results into in vivo effects is not possible. Future experiments should include other host factors such as oral tissues, immune cells and combinations of SSH as present in saliva, in order to have a more accurate picture of the phenomena taking place in both males and females.

Altered oral microbiota and immune dysfunction in Chinese elderly patients with schizophrenia: a cross-sectional study

Schizophrenia (SZ) is a complex psychiatric neurodevelopmental disorder with uncertain etiology and pathogenesis. Increasing evidence has recognized the key role of the gut microbiota in SZ. However, few studies have investigated the potential link between oral microbiota and SZ. We studied the tongue coating microbiota and inflammatory profiles of 118 elderly SZ patients and 97 age-matched healthy controls using Illumina MiSeq sequencing and multiplex immunoassays, respectively. Reduced α-diversity, along with a significant difference in β-diversity, were observed in patients with SZ. We have identified SZ-associated oral dysbiosis, characterized by increased Streptococcus and Fusobacterium, as well as decreased Prevotella and Veillonella. These differential genera could potentially serve as biomarkers for SZ, either alone or in combination. Additionally, an elevated Streptococcus/Prevotella ratio could indicate oral dysbiosis. These differential genera formed two distinct clusters: Streptococcus-dominated and Prevotella-dominated, which exhibited different correlations with the altered immunological profiles. Furthermore, we also observed disruptions in the inferred microbiota functions in SZ-associated microbiota, particularly in lipid and amino acid metabolism. Our study provides novel insights into the characteristics of tongue coating microbiota and its associations with immunological disturbances in elderly SZ patients, which offer new targets for the diagnosis and treatment of SZ in the elderly.

Salivary microbiome in kidney diseases: A narrative review

Many research has been conducted since the microbiota's discovery that have focused on the role it plays in health and disease. Microbiota can be divided into categories like intestinal, oral, respiratory, and skin microbiota based on the specific localized areas. To maintain homeostasis and control immunological response, the microbial populations live in symbiosis with the host. On the other hand, dysbiosis of the microbiota can cause diseases including kidney diseases and the deregulation of body functioning. We discuss the current understanding of how various kidney diseases are caused by the salivary microbiome (SM) in this overview. First, we review the studies on the salivary microbiota in diverse clinical situations. The importance of the SM in diabetic kidney disease, chronic kidney disease, membranous nephropathy, and IgA nephropathy is next highlighted. We conclude that the characteristics of the SM of patients with various kidney diseases have revealed the potential of salivary microbial markers as noninvasive tool for the detection of various kidney diseases.

Methionine-producing tumor micro(be) environment fuels growth of solid tumors

BACKGROUND

Recent studies have uncovered the near-ubiquitous presence of microbes in solid tumors of diverse origins. Previous literature has shown the impact of specific bacterial species on the progression of cancer. We propose that local microbial dysbiosis enables certain cancer phenotypes through provisioning of essential metabolites directly to tumor cells.

METHODS

16S rDNA sequencing of 75 patient lung samples revealed the lung tumor microbiome specifically enriched for bacteria capable of producing methionine. Wild-type (WT) and methionine auxotrophic (metA mutant) E. coli cells were used to condition cell culture media and the proliferation of lung adenocarcinoma (LUAD) cells were measured using SYTO60 staining. Further, colony forming assay, Annexin V Staining, BrdU, AlamarBlue, western blot, qPCR, LINE microarray and subcutaneous injection with methionine modulated feed were used to analyze cellular proliferation, cell-cycle, cell death, methylation potential, and xenograft formation under methionine restriction. Moreover, C14-labeled glucose was used to illustrate the interplay between tumor cells and bacteria.

RESULTS/DISCUSSION

Our results show bacteria found locally within the tumor microenvironment are enriched for methionine synthetic pathways, while having reduced S-adenosylmethionine metabolizing pathways. As methionine is one of nine essential amino acids that mammals are unable to synthesize de novo, we investigated a potentially novel function for the microbiome, supplying essential nutrients, such as methionine, to cancer cells. We demonstrate that LUAD cells can utilize methionine generated by bacteria to rescue phenotypes that would otherwise be inhibited due to nutrient restriction. In addition to this, with WT and metA mutant E. coli, we saw a selective advantage for bacteria with an intact methionine synthetic pathway to survive under the conditions induced by LUAD cells. These results would suggest that there is a potential bi-directional cross-talk between the local microbiome and adjacent tumor cells. In this study, we focused on methionine as one of the critical molecules, but we also hypothesize that additional bacterial metabolites may also be utilized by LUAD. Indeed, our radiolabeling data suggest that other biomolecules are shared between cancer cells and bacteria. Thus, modulating the local microbiome may have an indirect effect on tumor development, progression, and metastasis.

Saliva culture as a predictive indicator for current blood infections and antimicrobial resistance in the ICU setting

Antimicrobial resistance is a worldwide health problem and patients in intensive care are more vulnerable, requiring strict control measures and early identification. Currently, clinical culture materials are used to identify the bacterial agent, but saliva culture is not validated, which has great clinical relevance because it participates in several pathophysiological processes. The aim of this study was to validate saliva culture in an intensive care unit environment, determining its diagnostic value for infection. For this purpose, the results of the 39-month surveillance cultures, from the database of a private hospital were evaluated. A total of 323 cultures were paired between saliva, tracheal secretions, blood and urine from patients who were hospitalized for more than 5 days. The search for correlations between the results was performed using the Spearman correlation test. Severity and evolution data were also correlated. It was possible to correlate the presence of Klebsiella spp. between blood culture and saliva culture in 25% of the results (r = 0.01) and the correlation between saliva and tracheal secretion was 33% (r = 0.33447) with p < 0.0001. In conclusion, saliva can be an excellent discriminator of systemic infections, and can be considered a useful culture in clinical practice.

From nitrate to NO: potential effects of nitrate-reducing bacteria on systemic health and disease

Current research has described improving multisystem disease and organ function through dietary nitrate (DN) supplementation. They have provided some evidence that these floras with nitrate (NO3-) reductase are mediators of the underlying mechanism. Symbiotic bacteria with nitrate reductase activity (NRA) are found in the human digestive tract, including the mouth, esophagus and gastrointestinal tract (GT). Nitrate in food can be converted to nitrite under the tongue or in the stomach by these symbiotic bacteria. Then, nitrite is transformed to nitric oxide (NO) by non-enzymatic synthesis. NO is currently recognized as a potent bioactive agent with biological activities, such as vasodilation, regulation of cardiomyocyte function, neurotransmission, suppression of platelet agglutination, and prevention of vascular smooth muscle cell proliferation. NO also can be produced through the conventional L-arginine-NO synthase (L-NOS) pathway, whereas endogenous NO production by L-arginine is inhibited under hypoxia-ischemia or disease conditions. In contrast, exogenous NO3-/NO2-/NO activity is enhanced and becomes a practical supplemental pathway for NO in the body, playing an essential role in various physiological activities. Moreover, many diseases (such as metabolic or geriatric diseases) are primarily associated with disorders of endogenous NO synthesis, and NO generation from the exogenous NO3-/NO2-/NO route can partially alleviate the disease progression. The imbalance of NO in the body may be one of the potential mechanisms of disease development. Therefore, the impact of these floras with nitrate reductase on host systemic health through exogenous NO3-/NO2-/NO pathway production of NO or direct regulation of floras ecological balance is essential (e.g., regulation of body homeostasis, amelioration of diseases, etc.). This review summarizes the bacteria with nitrate reductase in humans, emphasizing the relationship between the metabolic processes of this microflora and host systemic health and disease. The potential effects of nitrate reduction bacteria on human health and disease were also highlighted in disease models from different human systems, including digestive, cardiovascular, endocrine, nervous, respiratory, and urinary systems, providing innovative ideas for future disease diagnosis and treatment based on nitrate reduction bacteria.

Exploring the Association Between Thyroid Function and Oral Microbiome Diversity: An NHANES Analysis

Objective

To investigate the association between thyroid functions and the oral microbiome diversity.

Method

Data from the US National Health and Nutrition Examination Survey (NHANES; 2009-2012) were analyzed. Thyroid functions were defined using thyroid hormones and related biomarkers. Oral microbiome was measured using the observed number of amplicon sequence variants (ASVs) and the Bray-Curtis dissimilarity. Linear regression was used to estimate the average change (β) and 95% CI for the number of ASVs against thyroid functions, adjusted for sociodemographic variables, health conditions, urinary iodine status, and periodontitis. Non-metric multidimensional scaling (NMDS) was used to analyze the Bray-Curtis dissimilarity.

Results

A total of 2943 participants were analyzed. The observed number of ASVs has a weighted mean of 128.9. Self-reported thyroid disease was associated with reduced number of ASVs (β = -9.2, 95% CI: -17.2, -1.2), if only adjusted for sociodemographic variables and health conditions. In the fully adjusted model, compared to normal thyroid function, both subclinical and clinical hyperthyroidism were associated with reduced number of ASVs (β = -59.6, 95% CI: -73.2, -46.0; β = -28.2, 95% CI: -50.0, -6.5, respectively). Thyroid peroxidase antibody level higher than the reference range was associated with higher observed ASV (β= 9.0, 95% CI: 1.2, 16.9). NMDS analysis suggested significant difference in oral microbiome composition between free triiodothyronine groups (P = .002), between free thyroxine groups (P = .015), and between thyroglobulin groups (P = .035).

Conclusion

Hyperthyroidism was associated with reduced oral microbiome diversity. Free triiodothyronine, free thyroxine, and thyroglobulin levels may alter the oral microbiome composition.