Frequency of Tongue Cleaning Impacts the Human Tongue Microbiome Composition and Enterosalivary Circulation of Nitrate

Salivary biomarkers for early detection of oral squamous cell carcinoma (OSCC) and head/neck squamous cell carcinoma (HNSCC): A systematic review and network meta-analysis

Oral cancer became a very common condition. WHO estimates that there are 4 cases of lip and oral cavity cancer for every 100,000 people worldwide. The early diagnosis of cancers is currently a top focus in the health sector. Recent systematic reviews and meta-analyses have identified promising biomarkers for early detection in several original research investigations. However, it is still unclear the quality of these evidence and which biomarker performs the best in terms of early detection. Therefore, the objective was, to map the methodological and reporting quality of available oral squamous cell carcinoma (OSCC) or head/neck squamous cell carcinoma (HNSCC) systematic reviews and meta-analysis. Secondly, to evaluate diagnostic accuracy of salivary biomarkers for common craniofacial cancers and to compare the diagnostic value of different salivary biomarkers. PubMed, Scopus, Web of Science, Embase and Cochrane Library electronic databases were used to map the methodological and reporting quality of the systematic reviews and meta-analysis conducted on the HNSCC, OSCC using the AMSTAR-2 checklist. The inclusion criteria were systematic reviews and meta-analysis published in the topic of HNSCC and OSCC biomarkers. Exclusion criteria were no animal studies; original primary studies, due to limitation of competency in other languages articles with language other than English were excluded. The sensitivity and specificity were calculated for salivary biomarkers and ranked according to network meta-analysis principles. A total of N = 5893 patients were included from four meta-analysis studies. All together, these included n = 37 primary studies. n = 94 biomarkers were pooled from these four meta-analyses and categorised into the stages at which they were detected (I-IV). In OSCC, Chemerin and MMP-9 displayed the highest sensitivity, registering 0.94 (95% CI 0.78, 1.00) and a balanced accuracy of 0.93. Phytosphingosine closely followed, with a sensitivity of 0.91 (95% CI 0.68, 0.99) and a balanced accuracy of 0.87. For HNSCC, the top three biomarkers are Actin, IL-1β Singleplex, and IL-8 ELISA. Actin leads with a sensitivity of 0.91 (95% CI 0.68-0.99), a specificity of 0.67, and an overall accuracy of 0.79. Subsequently, IL-1β Singleplex exhibits a sensitivity of 0.62 (95% CI 0.30-0.88), a specificity of 0.89, and an accuracy of 0.75, followed by IL-8 ELISA with a sensitivity of 0.81 (95% CI 0.54-0.97), a specificity of 0.59, and an accuracy of 0.70. In conclusion, there was highest sensitivity for MMP-9 and chemerin salivary biomarkers. There is need of further more studies to identify biomarkers for HNSCC and OSCC.

The effect of daily usage of Listerine Cool Mint mouthwash on the oropharyngeal microbiome: a substudy of the PReGo trial

Introduction. ListerineÒ is a bactericidal mouthwash widely used to prevent oral health problems such as dental plaque and gingivitis. However, whether it promotes or undermines a healthy oral microbiome is unclear.Hypothesis/Gap Statement. We hypothesized that the daily use of Listerine Cool Mint would have a significant impact on the oropharyngeal microbiome.Aim. We aimed to assess if daily usage of Listerine Cool Mint influenced the composition of the pharyngeal microbiome.Methodology. The current microbiome substudy is part of the Preventing Resistance in Gonorrhoea trial. This was a double-blind single-centre, crossover, randomized controlled trial of antibacterial versus placebo mouthwash to reduce the incidence of gonorrhoea/chlamydia/syphilis in men who have sex with men (MSM) taking HIV pre-exposure prophylaxis (PrEP). Fifty-nine MSM taking HIV PrEP were enrolled. In this crossover trial, participants received 3 months of daily Listerine followed by 3 months of placebo mouthwash or vice versa. Oropharyngeal swabs were taken at baseline and after 3 months use of each mouthwash. DNA was extracted for shotgun metagenomic sequencing (Illumina Inc.). Non-host reads were taxonomically classified with MiniKraken and Bracken. The alpha and beta diversity indices were compared between baseline and after each mouthwash use. Differentially abundant bacterial taxa were identified using ANOVA-like differential expression analysis.Results. Streptococcus was the most abundant genus in most samples (n = 103, 61.7 %) with a median relative abundance of 31.5% (IQR 20.6-44.8), followed by Prevotella [13.5% (IQR 4.8-22.6)] and Veillonella [10.0% (IQR 4.0-16.8)]. Compared to baseline, the composition of the oral microbiome at the genus level (beta diversity) was significantly different after 3 months of Listerine (P = 0.006, pseudo-F = 2.29) or placebo (P = 0.003, pseudo-F = 2.49, permutational multivariate analysis of variance) use. Fusobacterium nucleatum and Streptococcus anginosus were significantly more abundant after Listerine use compared to baseline.Conclusion. Listerine use was associated with an increased abundance of common oral opportunistic bacteria previously reported to be enriched in periodontal diseases, oesophageal and colorectal cancer, and systemic diseases. These findings suggest that the regular use of Listerine mouthwash should be carefully considered.

Do oral and gut microbiota communicate through redox pathways? A novel asset of the nitrate-nitrite-NO pathway

Nitrate may act as a regulator of •NO bioavailability via sequential reduction along the nitrate-nitrite-NO pathway with widespread health benefits, including a eubiotic effect on the oral and gut microbiota. Here, we discuss the molecular mechanisms of microbiota-host communication through redox pathways, via the production of •NO and oxidants by the family of NADPH oxidases, namely hydrogen peroxide (via Duox2), superoxide radical (via Nox1 and Nox2) and peroxynitrite, which leads to downstream activation of stress responses (Nrf2 and NFkB pathways) in the host mucosa. The activation of Nox2 by microbial metabolites is also discussed. Finally, we propose a new perspective in which both oral and gut microbiota communicate through redox pathways, with nitrate as the pivot linking both ecosystems.

Acute effects of a chewable beetroot-based supplement on cognitive performance: a double-blind randomized placebo-controlled crossover clinical trial

BACKGROUND

Dietary nitrate (NO3-) has been shown to be useful as an ergogenic aid with potential applications in health and disease (e.g., blood pressure control). However, there is no consensus about the effects of dietary NO3- or beetroot (BR) juice supplementation on cognitive function.

OBJECTIVE

The aim of this study was to evaluate the effects of a single dose of a chewable BR-based supplement on cognitive performance.

METHODS

A double-blind randomized placebo-controlled two-period crossover clinical trial was carried out based on the extension of the CONSORT guidelines for randomized crossover trials. A total of 44 participants (24 F; 20 M; 32.7 [12.5] years; 66.3 [9.0] kg; 170 [9.2] cm; 22.8 [1.4] kg/m2) were randomly allocated to receive first either four BR-based chewable tablets (BR-CT) containing 3 g of a Beta vulgaris extract (RedNite®) or four tablets of a placebo (maltodextrin). A 4-day washout period was used before crossover. Ninety minutes after ingestion of the treatments, a neuropsychological testing battery was administered in each period. The trial was registered at clinicaltrials.gov NCT05509075.

RESULTS

Significant improvements with moderate effect size were found on memory consolidation at the short and long term only after BR-CT supplementation via the Rey Auditory Verbal Learning Test immediate (+ 20.69%) and delayed (+ 12.34%) recalls. Likewise, enhancement on both frontal lobe functions (+ 2.57%) and cognitive flexibility (+ 11.16%) were detected after BR-CT. There was no significant change (p < 0.05) on verbal memory of short-term digits, working memory and information processing speed. Mixed results were found on mood and anxiety through the Beck Depression Inventory-II (BDI-II) and the State-Trait Anxiety Inventory (STAI-Y1 and STAI-Y2); however, sequence and period effects were seen on STAI-Y2.

CONCLUSIONS

The acute administration of a chewable BR-based supplement improves certain aspects of cognitive function in healthy females and males, particularly memory capacity and frontal skills.

Association between mouth rinse use and changes in blood pressure: A systematic review and meta-analysis with trial sequential analysis

INTRODUCTION

Previous randomized controlled trials have shown that the use of antiseptic mouth rinses not only eradicates oral bacteria but also disrupts their ability to convert nitrate to nitrite, which is the key molecule in regulating blood pressure (BP).

OBJECTIVE

This study aimed to evaluate the association between the use of mouth rinses and changes in BP.

METHODS

The PubMed, Web of Science, EMBASE, Scopus, and Cochrane Library databases were systematically searched from their respective inception dates to 18th December 2022 to identify potential interventional studies with information on the association between the use of mouth rinse and changes in BP. Five trials using a controlled, crossover design were identified for data analysis.

RESULTS

The weighted mean difference was pooled using a random-effects model. The pooled results of five trials together showed that the use of mouth rinses did not result in a statistically or clinically significant increase in the systolic BP (SBP) (1.59 mmHg; 95% confidence interval [CI], -0.15 to 3.33) or diastolic BP (DBP) (0.46 mmHg; 95% CI, -0.72 to 1.64). The trial sequential analysis did not present conclusive evidence supporting the association between mouth rinse use and BP elevation.

CONCLUSION

Within the limits of the available evidence, our review and meta-analysis showed that mouth rinse use did not result in a statistically significant increase in the SBP, DBP, or mean arterial pressure (MAP). Nevertheless, the results should be interpreted cautiously due to the high degree of inconsistency across the studies.

Cytokine and microbiota profiles in obesity-related hypertension patients

Background

Systemic arterial hypertension is linked to a heightened risk of cardiovascular diseases on a global scale. In Mexico, nearly half of adults in vulnerable conditions experience hypertension. Imbalance in the oral and intestinal microbiota composition has been observed in patients with hypertension, documented by a decrease of bacteria producing short-chain fatty acids, which play a critical role in blood pressure regulation.

Aim

To examine the cytokines' profile and assess the characteristics of oral and gut microbiota in obesity-related hypertension in Mexican patients.

Methods

A cross-sectional, observational, and analytical study was carried out. Twenty-two patients were categorized by their body mass index (BMI) as overweight and obese, and the diagnosis of primary hypertension. DNA from supragingival dental plaque and feces samples was used to carry out 16S rRNA sequencing. Additionally, 13 cytokines were quantified.

Results

In the oral microbiota, Kluyvera was found to be significantly enriched in obese compared to overweight patients. Instead, the gut microbiota was dominated by Firmicutes. However, the correlation between certain genera and proinflammatory cytokines was noted.

Conclusion

This exploratory study provides insights into the complex relationship between the oral and gut microbiota and their association with systemic inflammation in obesity-related hypertension.

Sweet Orange Juice Processing By-Product Extracts: A Caries Management Alternative to Chlorhexidine

Dental caries is one of the most prevalent chronic diseases globally in both children and adults. This study investigated the potential of industrial sweet orange waste extracts (ISOWE) as a substitute for chlorhexidine (CHX) in managing dental caries. First, the cytotoxicity of ISOWE (40, 80, 120 mg/mL) and CHX (0.1 and 0.2%) on buccal epithelial cells was determined. ISOWE exhibited no overall toxicity, whereas CHX strongly affected cell viability. The combination of ISOWE and CHX significantly enhanced cell proliferation compared to CHX alone. Next, the antimicrobial efficacy of ISOWE, CHX, and their combination was assessed against a 7-day complex biofilm model inoculated with oral samples from human volunteers. CHX exhibited indiscriminate antimicrobial action, affecting both pathogenic and health-associated oral microorganisms. ISOWE demonstrated lower antimicrobial efficacy than CHX but showed enhanced efficacy against pathogenic species while preserving the oral microbiome's balance. When applied to a cariogenic biofilm, the combined treatment of ISOWE with 0.1% CHX showed similar efficacy to 0.2% CHX treatment alone. Overall, the findings suggest that ISOWE is a promising natural anti-cariogenic agent with lower toxicity and enhanced selectivity for pathogenic species compared to CHX.

Smoking and salivary microbiota: a cross-sectional analysis of an Italian alpine population

The oral microbiota plays an important role in the exogenous nitrate reduction pathway and is associated with heart and periodontal disease and cigarette smoking. We describe smoking-related changes in oral microbiota composition and resulting potential metabolic pathway changes that may explain smoking-related changes in disease risk. We analyzed health information and salivary microbiota composition among 1601 Cooperative Health Research in South Tyrol participants collected 2017-2018. Salivary microbiota taxa were assigned from amplicon sequences of the 16S-V4 rRNA and used to describe microbiota composition and predict metabolic pathways. Aerobic taxa relative abundance decreased with daily smoking intensity and increased with years since cessation, as did inferred nitrate reduction. Former smokers tended to be more similar to Never smokers than to Current smokers, especially those who had quit for longer than 5 years. Cigarette smoking has a consistent, generalizable association on oral microbiota composition and predicted metabolic pathways, some of which associate in a dose-dependent fashion. Smokers who quit for longer than 5 years tend to have salivary microbiota profiles comparable to never smokers.

Mouthwash Effects on the Oral Microbiome: Are They Good, Bad, or Balanced?

This narrative review describes the oral microbiome, and its role in oral health and disease, before considering the impact of commonly used over-the-counter (OTC) mouthwashes on oral bacteria, viruses, bacteriophages, and fungi that make up these microbial communities in different niches of the mouth. Whilst certain mouthwashes have proven antimicrobial actions and clinical effectiveness supported by robust evidence, this review reports more recent metagenomics evidence, suggesting that mouthwashes such as chlorhexidine may cause "dysbiosis," whereby certain species of bacteria are killed, leaving others, sometimes unwanted, to predominate. There is little known about the effects of mouthwashes on fungi and viruses in the context of the oral microbiome (virome) in vivo, despite evidence that they "kill" certain viral pathogens ex vivo. Evidence for mouthwashes, much like antibiotics, is also emerging with regards to antimicrobial resistance, and this should further be considered in the context of their widespread use by clinicians and patients. Therefore, considering the potential of currently available OTC mouthwashes to alter the oral microbiome, this article finally proposes that the ideal mouthwash, whilst combatting oral disease, should "balance" antimicrobial communities, especially those associated with health. Which antimicrobial mouthwash best fits this ideal remains uncertain.

The Effects of Antimicrobial Mouthwashes on Systemic Disease: What Is the Evidence?

The potential association between antimicrobial mouthwash use and systemic health has gained attention in recent years with reports highlighting how some common systemic conditions are influenced by the use of different types of mouthwashes. In this context, links between mouthwash use and cardiovascular disease, diabetes mellitus, oral cancer, Alzheimer's disease, and preeclampsia have been proposed, albeit with limited levels of evidence. Chlorhexidine mouthwash in particular has been the most widely studied agent while available data on other types of over-the-counter mouthwashes are generally scarce. Furthermore, there is currently no evidence-based recommendations on the appropriate use of mouthwashes during pregnancy. This article will present the current evidence on the association between mouthwash use and the aforementioned conditions with emphasis on the mechanisms that may underlie such an association.

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.

Oral microbiome mediated inflammation, a potential inductor of vascular diseases: a comprehensive review

The dysbiosis of the oral microbiome and vascular translocation of the periodontopathic microorganism to peripheral blood can cause local and systemic extra-oral inflammation. Microorganisms associated with the subgingival biofilm are readily translocated to the peripheral circulation, generating bacteremia and endotoxemia, increasing the inflammation in the vascular endothelium and resulting in endothelial dysfunction. This review aimed to demonstrate how the dysbiosis of the oral microbiome and the translocation of oral pathogen-induced inflammation to peripheral blood may be linked to cardiovascular diseases (CVDs). The dysbiosis of the oral microbiome can regulate blood pressure and activate endothelial dysfunction. Similarly, the passage of periodontal microorganisms into the peripheral circulation and their virulence factors have been associated with a vascular compartment with a great capacity to activate endothelial cells, monocytes, macrophages, and plaquettes and increase interleukin and chemokine secretion, as well as oxidative stress. This inflammatory process is related to atherosclerosis, hypertension, thrombosis, and stroke. Therefore, oral diseases could be involved in CVDs via inflammation. The preclinic and clinical evidence suggests that periodontal disease increases the proinflammatory markers associated with endothelial dysfunction. Likewise, the evidence from clinical studies of periodontal treatment in the long term evidenced the reduction of these markers and improved overall health in patients with CVDs.

Antibiotics in Dentistry: A Narrative Review of the Evidence beyond the Myth

Antibiotics have undoubtedly revolutionized medicine and the health and survival of patients with life-threatening infections, being nonetheless free from potential adverse effects, and the risk of intestinal dysbiosis, antimicrobial resistance, and the resulting consequences for the patient's health and the public purse. The present study narratively reviewed the epidemiological data on worldwide antibiotic consumption and administration in dental practice, patients' adherence to prescriptions, the antimicrobial resistance phenomenon in dentistry, and the evidence supporting and recommending appropriate antibiotic use in dental care. Eligible systematic reviews and original studies in humans published in the English language from January 2000 to 26 January 2023 were considered. A total of 78 studies, 47 on the epidemiology of antibiotic use and prescription in dentistry, 6 on antibiotic therapy in dentistry, 12 on antibiotic prophylaxis in dentistry, 0 on adherence of dental patients to antibiotic prescription, and 13 on antimicrobial resistance in dentistry, were presently considered. Retrieved evidence revealed that antibiotics are frequently overused and misused in dental practice, dental patients frequently do not adhere to prescriptions, and antimicrobial resistance in dentistry is a still rising phenomenon also secondary to improper oral antiseptics use. The present findings highlighted the need to establish more evidence-based and accurate antibiotic prescriptions to sensitize dentists and dental patients to minimize and rationalize the use of antibiotics only when it is indicated and necessary, improve patients' adherence, and enhance knowledge and awareness of the antimicrobial resistance in dentistry.

Illuminating the oral microbiome and its host interactions: animal models of disease

Periodontitis and caries are driven by complex interactions between the oral microbiome and host factors, i.e. inflammation and dietary sugars, respectively. Animal models have been instrumental in our mechanistic understanding of these oral diseases, although no single model can faithfully reproduce all aspects of a given human disease. This review discusses evidence that the utility of an animal model lies in its capacity to address a specific hypothesis and, therefore, different aspects of a disease can be investigated using distinct and complementary models. As in vitro systems cannot replicate the complexity of in vivo host-microbe interactions and human research is typically correlative, model organisms-their limitations notwithstanding-remain essential in proving causality, identifying therapeutic targets, and evaluating the safety and efficacy of novel treatments. To achieve broader and deeper insights into oral disease pathogenesis, animal model-derived findings can be synthesized with data from in vitro and clinical research. In the absence of better mechanistic alternatives, dismissal of animal models on fidelity issues would impede further progress to understand and treat oral disease.

Preprocedural mouthwashes for infection control in dentistry-an update

OBJECTIVES

Aerosols and splatter are routinely generated in dental practice and can be contaminated by potentially harmful bacteria or viruses such as SARS-CoV-2. Therefore, preprocedural mouthwashes containing antiseptic agents have been proposed as a potential measure for infection control in dental practice. This review article aims to summarize the clinical (and, if insufficient, preclinical) evidence on preprocedural mouthwashes containing antiseptic agents and to draw conclusions for dental practitioners.

METHODS

Literature on preprocedural mouthwashes for reduction of bacterial or viral load in dental aerosols was searched and summarized.

RESULTS

Preprocedural mouthwashes, particularly those containing chlorhexidine digluconate (CHX), cetylpyridinium chloride (CPC), or essential oils (EO), can significantly reduce the bacterial load in dental aerosols. With respect to viruses such as HSV-1, there are too little clinical data to draw any clear recommendations. On the other hand, clinical data is consolidating that CPC-containing mouthwashes can temporarily reduce the intraoral viral load and infectivity in SARS-CoV-2 positive individuals. Nevertheless, potential risks and side effects due to regular antiseptic use such as ecological effects or adaptation of bacteria need to be considered.

CONCLUSIONS

The use of preprocedural mouthwashes containing antiseptics can be recommended according to currently available data, but further studies are needed, particularly on the effects on other viruses besides SARS-CoV-2. When selecting a specific antiseptic, the biggest data basis currently exists for CHX, CPC, EO, or combinations thereof.

CLINICAL RELEVANCE

Preprocedural mouthwashes containing antiseptics can serve as part of a bundle of measures for protection of dental personnel despite some remaining ambiguities and in view of potential risks and side effects.

Effect of Extracts, Fractions, and Isolated Molecules of Casearia sylvestris to Control Streptococcus mutans Cariogenic Biofilm

The effects of extracts, fractions, and molecules of Casearia sylvestris to control the cariogenic biofilm of Streptococcus mutans were evaluated. First, the antimicrobial and antibiofilm (initial and pre-formed biofilms) in prolonged exposure (24 h) models were investigated. Second, formulations (with and without fluoride) were assessed for topical effects (brief exposure) on biofilms. Third, selected treatments were evaluated via bacterium growth inhibition curves associated with gene expression and scanning electron microscopy. In initial biofilms, the ethyl acetate (AcOEt) and ethanolic (EtOH) fractions from Brasília (BRA/DF; 250 µg/mL) and Presidente Venceslau/SP (Water/EtOH 60:40 and Water/EtOH 40:60; 500 µg/mL) reduced ≥6-logs vs. vehicle. Only the molecule Caseargrewiin F (CsF; 125 µg/mL) reduced the viable cell count of pre-formed biofilms (5 logs vs. vehicle). For topical effects, no formulation affected biofilm components. For the growth inhibition assay, CsF yielded a constant recovery of surviving cells (≅3.5 logs) until 24 h (i.e., bacteriostatic), and AcOEt_BRA/DF caused progressive cell death, without cells at 24 h (i.e., bactericidal). CsF and AcOEt_BRA/DF damaged S. mutans cells and influenced the expression of virulence genes. Thus, an effect against biofilms occurred after prolonged exposure due to the bacteriostatic and/or bactericidal capacity of a fraction and a molecule from C. sylvestris.

Oral hygiene, mouthwash usage and cardiovascular mortality during 18.8 years of follow-up

Aim(s) We tested the following hypotheses: would better oral hygiene self-care (OHS) influence cardiovascular (CVD) mortality? Will using mouthwash in addition to OHS affect CVD mortality? How does mouthwash usage impact the oral microbes?Design and methods Among 354 dentate subjects from the Kuopio Oral Health and Heart study, the association of OHS with CVD mortality was assessed using Cox regression analyses, adjusting for age, sex, smoking, dyslipidemia, diabetes, hypertension and education. Additionally, whether using mouthwash would affect this relationship was evaluated.Results In the multivariable-adjusted models, OHS was associated with a 51% reduction in the risk of CVD mortality (hazard ratio [HR] 0.49 [0.28-0.85]; p = 0.01). Even those who had coronary artery disease at baseline showed a marginally significant benefit (0.50 [0.24-1.06]; p = 0.07). However, mouthwash usage did not change OHS effects (HR = 0.49 [0.27-0.87]; p = 0.01), indicating no additional benefits nor detriments. All tested microbes trended to decrease with mouthwash usage in the short term, but none were statistically significant.Conclusion Good OHS significantly lowered the risk of CVD mortality relative to poor OHS. Mouthwash usage did not show any long-term harm or benefit on CVD mortality beyond the benefits rendered by brushing and flossing.

Short-term effects of Chlorhexidine mouthwash and Listerine on oral microbiome in hospitalized patients

Introduction

Chlorhexidine (CHX) and essential oil containing mouthwashes like Listerine^® can improve oral hygiene via suppressing oral microbes. In hospitalized patients, CHX mouthwash reduces the incidence of ventilator-associated pneumonia. However, CHX use was also associated with increased mortality, which might be related to nitrate-reducing bacteria. Currently, no study determines oral bacteria targeted by essential oils mouthwash in hospitalized patients using a metagenomic approach.

Methods

We recruited 87 hospitalized patients from a previous randomized control study, and assigned them to three mouthwash groups: CHX, Listerine, and normal saline (control). Before and after gargling the mouthwash twice a day for 5-7 days, oral bacteria were examined using a 16S rDNA approach.

Results

Alpha diversities at the genus level decreased significantly only for the CHX and Listerine groups. Only for the two groups, oral microbiota before and after gargling were significantly different, but not clearly distinct. Paired analysis eliminated the substantial individual differences and revealed eight bacterial genera (including Prevotella, Fusobacterium, and Selenomonas) with a decreased relative abundance, while Rothia increased after gargling the CHX mouthwash. After gargling Listerine, seven genera (including Parvimonas, Eubacterium, and Selenomonas) showed a decreased relative abundance, and the magnitudes were smaller compared to the CHX group. Fewer bacteria targeted by Listerine were reported to be nitrate-reducing compared to the CHX mouthwash.

Discussion

In conclusion, short-term gargling of the CHX mouthwash and Listerine altered oral microbiota in our hospitalized patients. The bacterial genera targeted by the CHX mouthwash and Listerine were largely different and the magnitudes of changes were smaller using Listerine. Functional alterations of gargling CHX and Listerine were also different. These findings can be considered for managing oral hygiene of hospitalized patients.

A mouthwash formulated with o-cymen-5-ol and zinc chloride specifically targets potential pathogens without impairing the native oral microbiome in healthy individuals

Background

Many antimicrobial compounds in mouthwashes can have a negative impact on the oral microbiome. O-cymen-5-ol, a compound derived from a phytochemical, has a targeted mode of action and is being used as an alternative. However, its effect on the native oral microbiome is unknown.

Aim

To assess the effect of a mouthwash formulated with o-cymen-5-ol and zinc chloride on the oral microbiome of healthy individuals.

Methods

A mouthwash formulated with o-cymen-5-ol and zinc chloride was administered to a cohort of 51 volunteers for 14 days, while another cohort of 49 volunteers received a placebo. The evolution of the oral microbiome in both groups was analysed using a metataxonomic approach.

Results

Analysis of the oral microbiome showed that the mouthwash selectively targeted potential oral pathogens while maintaining the integrity of the rest of the microbiome. Specifically, the relative abundance of several potentially pathogenic bacterial taxa, namely Fusobacteriota, Prevotella, Actinomyces, Granulicatella, Abiotrophia, Lautropia, Lachnoanaerobaculum, Eubacterium (nodatum group) and Absconditabacteriales (SR1) decreased, while the growth of Rothia, a nitrate-reducing bacterium beneficial for blood pressure, was stimulated.

Conclusions

The use of o-cymen-5-ol and zinc chloride as antimicrobial agents in oral mouthwashes is a valuable alternative to classical antimicrobial agents.

Distinct Agents Induce Streptococcus mutans Cells with Altered Biofilm Formation Capacity

Dental caries is a multifactorial biofilm- and sugar-dependent disease. This study investigated the influence of different agents on the induction of surviving Streptococcus mutans cells after successive treatment cycles and characterized the biofilms formed by these cells recovered posttreatment. The agents (with their main targets listed in parentheses) were compound 1771 (lipoteichoic acids), 4′ hydroxychalcone (exopolysaccharides), myricetin (exopolysaccharides), tt-farnesol (cytoplasmatic membrane), sodium fluoride (enolase—glycolysis), chlorhexidine (antimicrobial), and vehicle. Recovered cells from biofilms were generated from exposure to each agent during 10 cycles of consecutive treatments (modeled on a polystyrene plate bottom). The recovered cell counting was different for each agent. The recovered cells from each group were grown as biofilms on saliva-coated hydroxyapatite discs (culture medium with sucrose/starch). In S. mutans biofilms formed by cells recovered from biofilms previously exposed to compound 1771, 4′ hydroxychalcone, or myricetin, cells presented higher expression of the 16S rRNA, gyrA (DNA replication and transcription), gtfB (insoluble exopolysaccharides), and eno (enolase—glycolysis) genes and lower quantities of insoluble dry weight and insoluble exopolysaccharides than those derived from other agents. These findings were confirmed by the smaller biovolume of bacteria and/or exopolysaccharides and the biofilm distribution (coverage area). Moreover, preexposure to chlorhexidine increased exopolysaccharide production. Therefore, agents with different targets induce cells with distinct biofilm formation capacities, which is critical for developing formulations for biofilm control.

IMPORTANCE This article addresses the effect of distinct agents with distinct targets in the bacterial cell (cytoplasmatic membrane and glycolysis), the cell’s extracellular synthesis of exopolysaccharides that are important for cariogenic extracellular matrix construction and biofilm buildup in the generation of cells that persisted after treatment, and how these cells form biofilms in vitro. For example, if preexposure to an agent augments the production of virulence determinants, such as exopolysaccharides, its clinical value may be inadequate. Modification of biofilm formation capacity after exposure to agents is critical for the development of formulations for biofilm control to prevent caries, a ubiquitous disease associated with biofilm and diet.

Ecological Effects of Daily Antiseptic Treatment on Microbial Composition of Saliva-Grown Microcosm Biofilms and Selection of Resistant Phenotypes

Antiseptics are widely used in dental practice and included in numerous over-the-counter oral care products. However, the effects of routine antiseptic use on microbial composition of oral biofilms and on the emergence of resistant phenotypes remain unclear. Microcosm biofilms were inoculated from saliva samples of four donors and cultured in the Amsterdam Active Attachment biofilm model for 3 days. Then, they were treated two times daily with chlorhexidine digluconate (CHX) or cetylpyridinium chloride (CPC) for a period of 7 days. Ecological changes upon these multiple antiseptic treatments were evaluated by semiconductor-based sequencing of bacterial 16S rRNA genes and identification of amplicon sequence variants (ASVs). Furthermore, culture-based approaches were used for colony-forming units (CFU) assay, identification of antiseptic-resistant phenotypes using an agar dilution method, and evaluation of their antibiotic susceptibilities. Both CHX and CPC showed only slight effects on CFU and could not inhibit biofilm growth despite the two times daily treatment for 7 days. Both antiseptics showed significant ecological effects on the microbial compositions of the surviving microbiota, whereby CHX led to enrichment of rather caries-associated saccharolytic taxa and CPC led to enrichment of rather gingivitis-associated proteolytic taxa. Antiseptic-resistant phenotypes were isolated on antiseptic-containing agar plates, which also exhibited phenotypic resistance to various antibiotics. Our results highlight the need for further research into potential detrimental effects of antiseptics on the microbial composition of oral biofilms and on the spread of antimicrobial resistance in the context of their frequent use in oral healthcare.

Individual Sweet Taste Perception Influences Salivary Characteristics After Orosensory Stimulation With Sucrose and Noncaloric Sweeteners

Emerging evidence points to a major role of salivary flow and viscoelastic properties in taste perception and mouthfeel. It has been proposed that sweet-tasting compounds influence salivary characteristics. However, whether perceived differences in the sensory properties of structurally diverse sweet-tasting compounds contribute to salivary flow and saliva viscoelasticity as part of mouthfeel and overall sweet taste perception remains to be clarified. In this study, we hypothesized that the sensory diversity of sweeteners would differentially change salivary characteristics in response to oral sweet taste stimulation. Therefore, we investigated salivary flow and saliva viscoelasticity from 21 healthy test subjects after orosensory stimulation with sucrose, rebaudioside M (RebM), sucralose, and neohesperidin dihydrochalcone (NHDC) in a crossover design and considered the basal level of selected influencing factors, including the basal oral microbiome. All test compounds enhanced the salivary flow rate by up to 1.51 ± 0.12 g/min for RebM compared to 1.10 ± 0.09 g/min for water within the 1st min after stimulation. The increase in flow rate was moderately correlated with the individually perceived sweet taste (r = 0.3, p < 0.01) but did not differ between the test compounds. The complex viscosity of saliva was not affected by the test compounds, but the analysis of covariance showed that it was associated (p < 0.05) with mucin 5B (Muc5B) concentration. The oral microbiome was of typical composition and diversity but was strongly individual-dependent (permutational analysis of variance (PERMANOVA): R² = 0.76, p < 0.001) and was not associated with changes in salivary characteristics. In conclusion, this study indicates an impact of individual sweet taste impressions on the flow rate without measurable changes in the complex viscosity of saliva, which may contribute to the overall taste perception and mouthfeel of sweet-tasting compounds.

Nitrite Generating and Depleting Capacity of the Oral Microbiome and Cardiometabolic Risk: Results from ORIGINS

Background

The enterosalivary nitrate–nitrite–nitric oxide (NO 3 –NO 2 –NO) pathway generates NO following oral microbiota‐mediated production of salivary nitrite, potentially linking the oral microbiota to reduced cardiometabolic risk. Nitrite depletion by oral bacteria may also be important for determining the net nitrite available systemically. We examine if higher abundance of oral microbial genes favoring increased oral nitrite generation and decreased nitrite depletion is associated with a better cardiometabolic profile cross‐sectionally.

Methods and Results

This study includes 764 adults (mean [SD] age 32 [9] years, 71% women) enrolled in ORIGINS (Oral Infections, Glucose Intolerance, and Insulin Resistance Study). Microbial DNA from subgingival dental plaques underwent 16S rRNA gene sequencing; PICRUSt2 was used to estimate functional gene profiles. To represent the different components and pathways of nitrogen metabolism in bacteria, predicted gene abundances were operationalized to create summary scores by (1) bacterial nitrogen metabolic pathway or (2) biochemical product (NO 2 , NO, or ammonia [NH 3 ]) formed by the action of the bacterial reductases encoded. Finally, nitrite generation‐to‐depletion ratios of gene abundances were created from the above summary scores. A composite cardiometabolic Z score was created from cardiometabolic risk variables, with higher scores associated with worse cardiometabolic health. We performed multivariable linear regression analysis with cardiometabolic Z score as the outcome and the gene abundance summary scores and ratios as predictor variables, adjusting for sex, age, race, and ethnicity in the simple adjusted model. A 1 SD higher NO versus NH 3 summary ratio was inversely associated with a −0.10 (false discovery rate q =0.003) lower composite cardiometabolic Z score in simple adjusted models. Higher NH 3 summary score (suggestive of nitrite depletion) was associated with higher cardiometabolic risk, with a 0.06 (false discovery rate q =0.04) higher composite cardiometabolic Z score.

Conclusions

Increased net capacity for nitrite generation versus depletion by oral bacteria, assessed through a metagenome estimation approach, is associated with lower levels of cardiometabolic risk.

Is Chlorhexidine in Dentistry an Ally or a Foe? A Narrative Review

Chlorhexidine has been one of the most effective and popular antiseptic substances used in medicine for decades. In dentistry, it has been used in endodontics, periodontology, surgery, and general dentistry. It is also widely used daily by patients in mouth rinses, gels, or toothpastes. Because of its multiple uses, we should follow all types of research reporting its potential adverse effects. This article aims to review the most up-to-date studies regarding chlorhexidine and its possible side effects, in the period of the SARS-CoV-2 pandemic, as the use of different antiseptic substances has rapidly increased.

Microbial Characteristics of Common Tongue Coatings in Patients with Precancerous Lesions of the Upper Gastrointestinal Tract

The tongue coating (TC) microbiota, a crucial component of the tongue coating, illustrates a huge microbial percentage of the body that mostly includes actinobacteria, bacteroides, firmicutes, and fusobacteria. The TC microbiota is closely related to the development of upper gastrointestinal malignancies, such as oral, gastric, and esophageal cancer. Nonetheless, the microbiological characteristics of common TCs in individuals with precancerous lesions of the upper gastrointestinal tract are still unclear. Herein, we designed a case-control study, recruiting 153 PLUGT patients with four different types of TCs, including 47 white-thin, 19 white-thick, 47 yellow-thin, and 40 yellow-thick, as well as 47 volunteers as controls. To analyze microbial characteristics, 16S rRNA microbiome approaches were used. An enzyme-linked immunosorbent assay (ELISA) was employed to assess serum IL-17A and total bile acid (TBA). According to the obtained results, Leptotrichia was found to be a promising biomarker for thin as well as thick yellow coatings. In comparison to the control TC microbiota, 39 different genera developed commensal networks in common TCs. Lachnoanaerobaculum and pseudonocardia were the most striking core bacteria. Lachnoanaerobaculum positively correlated with Leptotrichia in W-thin and Y-thick coatings, with actinomyces and methylobacterium in Y-thin coatings, with Campylobacter in Y-thick coatings, and with Bradyrhizobium in W-thick and Y-thick coatings. Serum IL-17A levels were greater in cases with W-thin coating than in controls, and serum IL-17A was positively linked with Parvimonas in patients with W-thick or Y-thin coating. In Y-thin coating, the oral dominating bacteria Streptococcus was negatively linked with serum TBA. Taken together, the promoted bacteria were found to be synergistically proliferative in the TCs of PLUGT patients. The diverse TCs had distinct bacterial commensal networks, whereas the common TCs were linked by specific bacteria to serum IL-17A and TBA.

Pathways Linking Oral Bacteria, Nitric Oxide Metabolism, and Health

Nitrate-reducing oral bacteria have gained a lot of interest due to their involvement in nitric oxide (NO) synthesis and its important cardiometabolic outcomes. Consortia of nitrate-metabolizing oral bacteria associated with cardiometabolic health and cognitive function have been recently identified. Longitudinal studies and clinical trials have shown that chronic mouthwash use is associated with increased blood pressure and increased risk for prediabetes/diabetes and hypertension. Concurrently, recent studies are beginning to shed some light on the complexity of nitrate reduction pathways of oral bacteria, such as dissimilatory nitrate reduction to ammonium (DNRA), which converts nitrite into ammonium, and denitrification, which converts nitrite to NO, nitrous oxide, and dinitrogen. These pathways can affect the composition and metabolism of the oral microbiome; consequently, salivary nitrate and nitrite metabolism have been proposed as targets for probiotics and oral health. These pathways could also affect systemic NO levels because NO generated through denitrification can be oxidized back to nitrite in the saliva, thus facilitating flux along the NO₃^--NO₂^--NO pathway, while DNRA converts nitrite to ammonium, leading to reduced NO. It is, therefore, important to understand which pathway predominates under different oral environmental conditions, since the clinical consequences could be different for oral and systemic health. Recent studies show that oral hygiene measures such as tongue cleaning and dietary nitrate are likely to favor denitrifying bacteria such as Neisseria, which are linked with better cardiometabolic health. A vast body of literature demonstrates that redox potential, carbon-to-nitrate ratio, and nitrate-to-nitrite ratio are key environmental drivers of the competing denitrification and DNRA pathways in various natural and artificial ecosystems. Based on this information, a novel behavioral and microbial model for nitric oxide metabolism and health is proposed, which links lifestyle factors with oral and systemic health through NO metabolism.

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

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

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

The oral microbiome: Role of key organisms and complex networks in oral health and disease

States of oral health and disease reflect the compositional and functional capacities of, as well as the interspecies interactions within, the oral microbiota. The oral cavity exists as a highly dynamic microbial environment that harbors many distinct substrata and microenvironments that house diverse microbial communities. Specific to the oral cavity, the nonshedding dental surfaces facilitate the development of highly complex polymicrobial biofilm communities, characterized not only by the distinct microbes comprising them, but cumulatively by their activities. Adding to this complexity, the oral cavity faces near-constant environmental challenges, including those from host diet, salivary flow, masticatory forces, and introduction of exogenous microbes. The composition of the oral microbiome is shaped throughout life by factors including host genetics, maternal transmission, as well as environmental factors, such as dietary habits, oral hygiene practice, medications, and systemic factors. This dynamic ecosystem presents opportunities for oral microbial dysbiosis and the development of dental and periodontal diseases. The application of both in vitro and culture-independent approaches has broadened the mechanistic understandings of complex polymicrobial communities within the oral cavity, as well as the environmental, local, and systemic underpinnings that influence the dynamics of the oral microbiome. Here, we review the present knowledge and current understanding of microbial communities within the oral cavity and the influences and challenges upon this system that encourage homeostasis or provoke microbiome perturbation, and thus contribute to states of oral health or disease.

Oral, Tongue-Coating Microbiota, and Metabolic Disorders: A Novel Area of Interactive Research

Interactions between colonizing microbiota and the host have been fully confirmed, among which the tongue-coating microbiota have a moderate rate of renewal and disease sensitivity and are easily obtained, making them an ideal research subject. Oral microbiota disorders are related to diabetes, obesity, cardiovascular disease, cancer, and other systemic diseases. As an important part of the oral cavity, tongue-coating microbiota can promote gastritis and digestive system tumors, affecting the occurrence and development of multiple chronic diseases. Common risk factors include diet, age, and immune status, among others. Metabolic regulatory mechanisms may be similar between the tongue and gut microbiota. Tongue-coating microbiota can be transferred to the respiratory or digestive tract and create a new balance with local microorganisms, together with the host epithelial cells forming a biological barrier. This barrier is involved in the production and circulation of nitric oxide (NO) and the function of taste receptors, forming the oral-gut-brain axis (similar to the gut-brain axis). At present, the disease model and mechanism of tongue-coating microbiota affecting metabolism have not been widely studied, but they have tremendous potential.

Effects of chlorhexidine mouthwash on the oral microbiome

INTRODUCTION/OBJECTIVES

Chlorhexidine (CHX) is a commonly used mouthwash with potent anti-microbial effects useful for the management of oral disease. However, we are moving away from the view of simply 'killing' bacteria, towards managing oral microbial ecosystems (oral microbiome), as an integrated system, to promote oral and systemic health. Here, we aimed to review the effects of CHX mouthwash on the balance of microbial communities in the mouth in vivo in oral health and disease.

SOURCES AND STUDY SECTION

The hierarchy of evidence was applied, with systematic reviews and randomised controlled trials consulted where available and case controlled studies being described thereafter. Search terms for each subject category were entered into MEDLINE, PubMed, Google Scholar and the Cochrane database. Focussing on metagenomics studies provides unique overview of the oral microbiome as an integrated system.

DATA

Evidence was limited, but several next generation sequencing case-controlled studies suggested that in an integrated system, CHX may cause a shift towards lower bacterial diversity and abundance, in particular nitrate-reducing bacteria in vivo. CHX also appeared to alter salivary pH, lactate, nitrate and nitrite concentrations in saliva. Evidence regarding the effects of CHX on the oral microbiome during oral disease is still emerging.

CONCLUSIONS

CHX alters the composition the oral microbiome. However, as CHX use remains widespread in dentistry to manage oral disease, urgent research using metagenomics studies of microbial communities in vivo are still needed to determine CHX mouthwash is 'good', 'bad' or otherwise for bacteria, in the context of oral and systemic health.

Alterations of oral microbiota in patients with obstructive sleep apnea-hypopnea syndrome treated with continuous positive airway pressure: a pilot study

PURPOSE

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is an independent risk factor for cardiovascular diseases, including hypertension. In our previous study, it was demonstrated that oral microbiota alteration in patients with OSAHS, particularly in the genera Aggregatibacter and Porphyromonas, may influence the development of hypertension. Continuous positive airway pressure (CPAP) is the main therapy for OSAHS and OSAHS-associated hypertension. However, the role of oral microbiota post CPAP treatment remains unknown.

METHODS

We conducted 16S rDNA pyrosequencing and bioinformatic analyses to compare the bacterial composition of oral specimens from patients with OSAHS before and after overnight CPAP treatment.

RESULTS

This approach enabled a relatively comprehensive description of oral microbiota, with decreases in Gemella and increases in Staphylococcus, f_Lachnospiraceae, Parabacteroides, and f_Ruminococcaceae after CPAP treatment.

CONCLUSION

Alteration of oral microbiota may shed new insight on the underlying pathogenesis of OSAHS-associated hypertension.

Boosting nitric oxide in stress and respiratory infection: Potential relevance for asthma and COVID-19

Nitric oxide (NO) is a ubiquitous signaling molecule that is critical for supporting a plethora of processes in biological organisms. Among these, its role in the innate immune system as a first line of defense against pathogens has received less attention. In asthma, levels of exhaled NO have been utilized as a window into airway inflammation caused by allergic processes. However, respiratory infections count among the most important triggers of disease exacerbations. Among the multitude of factors that affect NO levels are psychological processes. In particular, longer lasting states of psychological stress and depression have been shown to attenuate NO production. The novel SARS-CoV-2 virus, which has caused a pandemic, and with that, sustained levels of psychological stress globally, also adversely affects NO signaling. We review evidence on the role of NO in respiratory infection, including COVID-19, and stress, and argue that boosting NO bioavailability may be beneficial in protection from infections, thus benefitting individuals who suffer from stress in asthma or SARS-CoV-2 infection.

Tongue microbiome in children with autism spectrum disorder

Background: A few recent studies have characterized the salivary microbiome in association with Autism Spectrum Disorder (ASD). Here, we sought to assess if there is an association between the tongue microbiome and ASD.

Methods: Tongue scrapping samples were obtained from 25 children with ASD and 38 neurotypical controls. The samples were sequenced for the 16S rRNA gene (V1-V3) and the resultant high-quality reads were assigned to the species-level using our previously described BLASTn-based algorithm. Downstream analyses of microbial profiles were conducted using QIIME, LEfSe, and R.

Results: Independent of grouping, Prevotella, Streptococcus, Leptotrichia, Veillonella, Haemophilus and Rothia accounted for > 60% of the average microbiome. Haemophilus parainfluenzae, Rothia mucilaginosa, Prevotella melaninogenica and Neisseria flavescens/subflava were the most abundant species. Species richness and diversity did not significantly differ between the study groups. Thirteen species and three genera were differentially abundant between the two groups, e.g. enrichment of Actinomyces odontolyticus and Actinomyces lingnae and depletion of Campylobacter concisus and Streptococcus vestibularis in the ASD group. However, none of them withstood adjustment for multiple comparisons.

Conclusion: The tongue microbiome of children with ASD was not significantly different from that of healthy control children, which is largely consistent with results from the literature.

Evaluation of Clinical, Biochemical and Microbiological Markers Related to Dental Caries

Our aim was to evaluate clinical, biochemical and microbiological markers related to dental caries in adults. A sample that consisted of 75 volunteers was utilized. The presence of caries and the presence of plaque and gingival indices were determined. Unstimulated salivary flow, pH, lactate, Streptococcus mutans and Streptococcus dentisani were measured in the participants’ plaque and saliva samples before and after rinsing with a sugar solution. Lactate in plaque was found to be significantly related to age, gender, tooth-brushing frequency, the presence of cavitated caries lesions and plaque and gingival indices (p < 0.05). The levels of S. dentisani in plaque increased significantly with tooth-brushing frequency (p = 0.03). Normalized plaque S. dentisani values and the percentage of S. dentisani were slightly higher in patients with basal lactic acid levels ≤ 50 mg/L. After rinsing with a sugary solution, the percentage of S. mutans levels in plaque were higher in patients with lactic acid levels > 350 mg/L (p = 0.03). Tooth-brushing frequency was the factor which was most associated with oral health. Women reflected better clinical and biochemical parameters than men. Low pH and high lactic acid levels tended to be associated with high caries rates. No association was found between bacteria levels and caries indices.

Periodontitis, Blood Pressure, and the Risk and Control of Arterial Hypertension: Epidemiological, Clinical, and Pathophysiological Aspects-Review of the Literature and Clinical Trials

Purpose of Review

Arterial hypertension is an important risk factor for cardiovascular disease. In the world, about 45% of people suffer from arterial hypertension, while good blood pressure control is achieved by only approximately 50% of all hypertensive patients treated. The reason for the high prevalence of arterial hypertension and its poor control is low knowledge of hypertensinogenic factors. One such factor is periodontitis, which is a disease of social importance.

Recent Findings

It has been shown that the occurrence of periodontitis leads to an increase in blood pressure, increasing the risk of arterial hypertension. Periodontitis can also lead to ineffectiveness of antihypertensive treatment. Some interventional studies have shown that treatment of periodontitis reduced blood pressure in patients with arterial hypertension. The pathogenesis of arterial hypertension in periodontitis is complex and concerns mainly the impairment of the vasodilatation properties of the endothelium.

Summary

Hygiene and periodontitis treatment should be a method of preventing arterial hypertension and a method of increasing the effectiveness of antihypertensive treatment.

Spatial Ecology of the Human Tongue Dorsum Microbiome

A fundamental question in microbial ecology is how microbes are spatially organized with respect to each other and their host. A test bed for examining this question is the tongue dorsum, which harbors a complex and important microbial community. Here, we use multiplexed fluorescence spectral imaging to investigate the organization of the tongue microbiome at micron to hundred-micron scales. We design oligonucleotide probes for taxa both abundant and prevalent, as determined by sequence analysis. Imaging reveals a highly structured spatial organization of microbial consortia, ranging in linear dimension from tens to hundreds of microns. The consortia appear to develop from a core of epithelial cells, with taxa clustering in domains suggestive of clonal expansion. Quantitative proximity analysis provides the basis for a model of tongue dorsum microbiome organization and dynamics. Our work illustrates how high-resolution analysis of micron-scale organization provides insights into physiological functions and microbiome-host interactions.

How microbes are spatially organized is a fundamental question in microbial ecology about which little is known. Using fluorescence spectral imaging, Wilbert et al. discover dense, highly structured microbial consortia on the human tongue. Analysis of the organization of these consortia permits inferences about community dynamics and oral microbial ecology.

Association Between Periodontitis and Blood Pressure Highlighted in Systemically Healthy Individuals: Results From a Nested Case-Control Study

[Figure: see text].

Potential role for age as a modulator of oral nitrate reductase activity

Reduction of salivary nitrate to nitrite by oral nitrate reductase (NR) expressing bacteria has emerged as an integral pathway in regulating nitric oxide (NO) homeostasis and signaling. The oral microbiome is critical for this pathway. Variations in this pathway may underlie variable responses in the magnitude by which dietary or therapeutic nitrate modulates NO-signaling. The relationships between oral microbes and NR activity, and the factors that affect this relationship remain unclear however. Using a cross-sectional study design, the objective of this study was to determine the relationships between oral microbes and oral NR activity using a protocol that directly measures initial NR activity. Tongue swabs were collected from 28 subjects ranging in age from 21 to 73y. Initial NR activity showed a bell-shaped dependence with age, with activity peaking at ~40-50y and being lower but similar between younger (20-30y) and older (51-73) individuals. Microbiome relative abundance and diversity analyses, using 16s sequencing, demonstrated differences across age and identified both NR expressing and non-expressing bacteria in modulating initial NR activity. Finally, initial NR activity was measured in 3mo and 13mo old C57BL/6J mice. No differences in bacterial number were observed. However initial NR activity was significantly (80%) lower in 13mo old mice. Collectively, these data suggest that age is a variable in NR activity and may modulate responsiveness to dietary nitrate.

Characterization of the Oral Microbiome of Medicated Type-2 Diabetes Patients

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease that is becoming a significant global health care problem. Several studies have shown that people with diabetes are more susceptible to oral problems, such as periodontitis and, although the causes are still inconclusive, oral microbiota is considered to play a major role in oral health. This study aimed to characterize the oral microbiome of a sample representing T2DM patients from Portugal and exploit potential associations between some microorganisms and variables like teeth brushing, smoking habits, average blood sugar levels, medication and nutrient intake. By sequencing the hypervariable regions V3-V4 of the 16S rRNA gene in 50 individuals belonging to a group of diabetes patients and a control group, we found a total of 232 taxa, from which only 65% were shared between both groups. No differences were found in terms of alpha and beta diversity between categories. We did not find significant differences in the oral microbiome profiles of control and diabetes patients. Only the class Synergistia and the genus TG5, which are related to periodontitis, were statistically more frequent in the control group. The similar microbiome profiles of medicated diabetics and the control group indicates that the relationship between the T2DM and the oral microbiome might be more related to either the lifestyle/diet rather than diabetes per se. Moreover, this study provides, for the first time, insights into the oral microbiome of a population with a high prevalence of diabetes.

Dietary Nitrate and Nitric Oxide Metabolism: Mouth, Circulation, Skeletal Muscle, and Exercise Performance

Nitric oxide (NO) is a gaseous signaling molecule that plays an important role in myriad physiological processes, including the regulation of vascular tone, neurotransmission, mitochondrial respiration, and skeletal muscle contractile function. NO may be produced via the canonical NO synthase-catalyzed oxidation of l-arginine and also by the sequential reduction of nitrate to nitrite and then NO. The body's nitrate stores can be augmented by the ingestion of nitrate-rich foods (primarily green leafy vegetables). NO bioavailability is greatly enhanced by the activity of bacteria residing in the mouth, which reduce nitrate to nitrite, thereby increasing the concentration of circulating nitrite, which can be reduced further to NO in regions of low oxygen availability. Recent investigations have focused on promoting this nitrate-nitrite-NO pathway to positively affect indices of cardiovascular health and exercise tolerance. It has been reported that dietary nitrate supplementation with beetroot juice lowers blood pressure in hypertensive patients, and sodium nitrite supplementation improves vascular endothelial function and reduces the stiffening of large elastic arteries in older humans. Nitrate supplementation has also been shown to enhance skeletal muscle function and to improve exercise performance in some circumstances. Recently, it has been established that nitrate concentration in skeletal muscle is much higher than that in blood and that muscle nitrate stores are exquisitely sensitive to dietary nitrate supplementation and deprivation. In this review, we consider the possibility that nitrate represents an essential storage form of NO and discuss the integrated function of the oral microbiome, circulation, and skeletal muscle in nitrate-nitrite-NO metabolism, as well as the practical relevance for health and performance.

Optimizing the quality of clinical studies on oral microbiome: A practical guide for planning, performing, and reporting

With this review, we aim to increase the quality standards for clinical studies with microbiome as an output parameter. We critically address the existing body of evidence for good quality practices in oral microbiome studies based on 16S rRNA gene amplicon sequencing. First, we discuss the usefulness of microbiome profile analyses. Is a microbiome study actually the best approach for answering the research question? This is followed by addressing the criteria for the most appropriate study design, sample size, and the necessary data (study metadata) that should be collected. Next, we evaluate the available evidence for best practices in sample collection, transport, storage, and DNA isolation. Finally, an overview of possible sequencing options (eg, 16S rRNA gene hypervariable regions, sequencing platforms), processing and data interpretation approaches, as well as requirements for meaningful data storage, sharing, and reporting are provided.

Assessing the Relationship Between Nitrate-Reducing Capacity of the Oral Microbiome and Systemic Outcomes

The significance of the oral microbiome in the generation of the nitric oxide (NO) via the enterosalivary nitrate-nitrite-nitric oxide pathway is increasingly recognized, directly linking the oral microbiome to cardiometabolic outcomes influenced by NO. The objective of this chapter is to outline a strategy of identifying pathway-specific bacterial taxa or predicted genes of interest from 16S rRNA data, specifically in the enterosalivary pathway of nitrate reduction, and analyzing their relationship with cardiometabolic outcomes using multivariable regression models.

Dysbiosis of the Salivary Microbiome is Associated with Hypertension and Correlated with Metabolic Syndrome Biomarkers

BACKGROUND

Hypertension (HT) is an idiopathic disease with severe complications and a high incidence of global mortality. Although the disease shares characteristic features with diabetes and obesity, the complex interplay of endogenous and environmental factors is not well characterized. The oral microbiome has recently been studied to better understand the role of commensal microorganisms in metabolic disorders, including HT, although its role in disease etiology is unclear.

METHODS

To bridge this gap, we compared the oral microbiome and clinical chemistry of adult subjects enrolled at Qatar Biobank. Clinical chemistry was performed using Roche Cobas-6000 analyzer. Saliva samples were subjected to 16S rRNA sequencing using Illumina MiSeq platform. Cross-gender comparisons were made between control (males/females) (C-M and C-F) and HT (HT-M and HT-F) groups.

RESULTS

The HT groups had higher (p ≤ 0.05) BMI, plasma glucose, insulin, C-peptide, and alkaline phosphatase (ALP) concentrations. Triglycerides, cholesterol, LDL-cholesterol, and sodium ions were similar among the groups. The microbiome was predominantly occupied by Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Firmicutes were higher (p ≤ 0.05) in the HT groups, whereas Proteobacteria was only higher in the C-F group. Prevotella and Veillonella were significantly higher in the HT groups and exhibited a positive correlation with blood pressure and hyperglycemia. In contrast to other studies, the mathematical summation of priori-select microbes reveals that nitrate-reducing microbes were higher in the HT groups compared with the controls.

CONCLUSION

In conclusion, these observations suggest a strong association of HT with microbial dysbiosis, where microbial species other than nitrate-reducing microbes contribute to blood pressure regulation. The findings affirm plausible microbial signatures of hypertension and suggest manipulating these microbes as a novel treatment modality. Future experiments are warranted for the mechanistic investigation of hypertension metagenomics and microbial activity.

The role of dietary nitrate and the oral microbiome on blood pressure and vascular tone

There is increasing evidence for the health benefits of dietary nitrates including lowering blood pressure and enhancing cardiovascular health. Although commensal oral bacteria play an important role in converting dietary nitrate to nitrite, very little is known about the potential role of these bacteria in blood pressure regulation and maintenance of vascular tone. The main purpose of this review is to present the current evidence on the involvement of the oral microbiome in mediating the beneficial effects of dietary nitrate on vascular function and to identify sources of inter-individual differences in bacterial composition. A systematic approach was used to identify the relevant articles published on PubMed and Web of Science in English from January 1950 until September 2019 examining the effects of dietary nitrate on oral microbiome composition and association with blood pressure and vascular tone. To date, only a limited number of studies have been conducted, with nine in human subjects and three in animals focusing mainly on blood pressure. In general, elimination of oral bacteria with use of a chlorhexidine-based antiseptic mouthwash reduced the conversion of nitrate to nitrite and was accompanied in some studies by an increase in blood pressure in normotensive subjects. In conclusion, our findings suggest that oral bacteria may play an important role in mediating the beneficial effects of nitrate-rich foods on blood pressure. Further human intervention studies assessing the potential effects of dietary nitrate on oral bacteria composition and relationship to real-time measures of vascular function are needed, particularly in individuals with hypertension and those at risk of developing CVD.

Role of Oral and Gut Microbiota in Dietary Nitrate Metabolism and Its Impact on Sports Performance

Nitrate supplementation is an effective, evidence-based dietary strategy for enhancing sports performance. The effects of dietary nitrate seem to be mediated by the ability of oral bacteria to reduce nitrate to nitrite, thus increasing the levels of nitrite in circulation that may be further reduced to nitric oxide in the body. The gut microbiota has been recently implicated in sports performance by improving muscle function through the supply of certain metabolites. In this line, skeletal muscle can also serve as a reservoir of nitrate. Here we review the bacteria of the oral cavity involved in the reduction of nitrate to nitrite and the possible changes induced by nitrite and their effect on gastrointestinal balance and gut microbiota homeostasis. The potential role of gut bacteria in the reduction of nitrate to nitrite and as a supplier of the signaling molecule nitric oxide to the blood circulation and muscles has not been explored in any great detail.

The evolutionary history of the human oral microbiota and its implications for modern health

Numerous biological and cultural factors influence the microbial communities (microbiota) that inhabit the human mouth, including diet, environment, hygiene, physiology, health status, genetics, and lifestyle. As oral microbiota can underpin oral and systemic diseases, tracing the evolutionary history of oral microbiota and the factors that shape its origins will unlock information to mitigate disease today. Despite this, the origins of many oral microbes remain unknown, and the key factors in the past that shaped our oral microbiota are only now emerging. High throughput DNA sequencing of oral microbiota using ancient DNA and comparative anthropological methodologies has been employed to investigate oral microbiota origins, revealing a complex, rich history. Here, I review the current literature on the factors that shaped and guided oral microbiota evolution, both in Europe and globally. In Europe, oral microbiota evolution was shaped by interactions with Neandertals, the adaptation of farming, widespread integration of industrialization, and postindustrial lifestyles that emerged after World War II. Globally, evidence for a multitude of different oral microbiota histories is emerging, likely supporting dissimilarities in modern oral health across discrete human populations. I highlight how these evolutionary changes are linked to the development of modern oral diseases and discuss the remaining factors that need to be addressed to improve this embryonic field of research. I argue that understanding the evolutionary history of our oral microbiota is necessary to identify new treatment and prevention options to improve oral and systemic health in the future.

Bronchopulmonary dysplasia is associated with reduced oral nitrate reductase activity in extremely preterm infants

Oral microbiome mediated nitrate reductase (NR) activity regulates nitric oxide (NO) bioavailability and signaling. While deficits in NO-bioavailability impact several morbidities of extreme prematurity including bronchopulmonary dysplasia (BPD), whether oral NR activity is associated with morbidities of prematurity is not known. We characterized NR activity in extremely preterm infants from birth until 34 weeks' post menstrual age (PMA), determined whether changes in the oral microbiome contribute to changes in NR activity, and determined whether changes in NR activity correlated with disease. In this single center prospective cohort study (n = 28), we observed two surprising findings: (1) NR activity unexpectedly peaked at 29 weeks' PMA (p < 0.05) and (2) when infants were stratified for BPD status, infants who developed BPD had significantly less NR activity at 29 weeks' PMA compared to infants who did not develop BPD. Oral microbiota and NR activity may play a role in BPD development in extremely preterm infants, indicating potential for disease prediction and therapeutic targeting.

Antiseptic mouthwash, the nitrate-nitrite-nitric oxide pathway, and hospital mortality: a hypothesis generating review

Meta-analyses and several large cohort studies have demonstrated that antiseptic mouthwashes are associated with mortality in hospitalized patients. A clear pathogenic mechanism is lacking, leading to controversy and a reluctance to abandon or limit the use of antiseptic mouthwashes. Here, we generate the hypothesis that a disturbance in nitric oxide homeostasis by antiseptic mouthwashes may be responsible for the observed increase in mortality risk. Nitric oxide is essential in multiple physiological processes, and a reduction in nitric oxide bioavailability is associated with the occurrence or worsening of pathologies, such as atherosclerosis, diabetes, and sepsis. Oral facultative anaerobic bacteria are essential for the enterosalivary nitrate–nitrite–nitric oxide pathway due to their capacity to reduce nitrate to nitrite. Nitrate originates from dietary sources or from the active uptake by salivary glands of circulating nitrate, which is then excreted in the saliva. Because antiseptic mouthwashes eradicate the oral bacterial flora, this nitric oxide-generating pathway is abolished, which may result in nitric oxide-deficient conditions potentially leading to life-threatening complications such as ischaemic heart events or sepsis.