Oral Microbiome: Getting to Know and Befriend Neighbors, a Biological Approach

Case Report: Shift from Aggressive Periodontitis to Feline Chronic Gingivostomatitis Is Linked to Increased Microbial Diversity

Aggressive Periodontitis (AP) and Feline Chronic Gingivostomatitis (FCGS) are two oral inflammatory diseases in cats with unknown etiology. Both conditions present with severe inflammation of the oral cavity and in FCGS it is found with additional deterioration of the non-keratinized mucosa. The oral microbiome is increasingly implicated in disease progression, but little is known about shifts in the microbial community during the AP and FCGS progression. To that end, we used deep metagenomic sequencing with total RNA on three longitudinal samples of the oral microbiome in a cat first diagnosed with AP that progressed to FCGS. This deep sequencing approach revealed that increased diversity at both the genus and species levels marked the shift from AP to FCGS, including increases in Porphyromonas and Treponema species, and decreased Streptobacillus species. The metatranscriptomes were then probed for expression of antimicrobial resistance genes and virulence factors. Disease-related genes that include cheY, and ompP5 were expressed in early AP and FCGS, while others like galU were only expressed in one or the other disease state. Both genus and species-level shifts were observed along the longitudinal microbiome samples with a noted increase in species diversity in the FCGS-associated microbiome. Corroborating that functional shifts accompany taxonomic changes, the AMR and virulence factor expression similarly changed between the sampling points. Together, these taxonomic and functional shifts indicate that AP and FCGS are potentially linked and may be marked by changes in the oral microbiome, which supports the development of microbial-based clinical diagnostics and therapeutics.

Radiation-induced changes in salivary metabolite profile and pathways in head and neck cancer patients

INTRODUCTION

This longitudinal study assessed the salivary metabolic profile in patients with head and neck cancer (HNC) treated with radiotherapy (RT). This study aims to investigate salivary metabolites and biological oral pathways induced by RT.

METHODS

Clinical data and unstimulated whole-mouth saliva (USWMS) were obtained from 45 HNC patients before, during, and one week after the RT. Data was also collected from 30 healthy controls. NMR spectroscopy identified and quantified 24 metabolites. Spearman's rank correlation analysis and pathway enrichment analysis (MetaboAnalyst 6.0) was performed to check the effect of cancer therapy on the correlation and pathways of different salivary metabolites.

RESULTS

Of 24 metabolites identified, 17 salivary metabolites showed a consistent decrease in the concentration during and after treatment of HNC patients. The metabolite proline decreased, whereas fucose and 1,2-Propanediol were increased in the saliva causing altered redox balance and abnormal fucosylation in HNC patients compared to controls. Spearman correlation analysis indicated changes between pyruvate and some other metabolites, including alanine, trimethylamine, choline, taurine, and succinate, during RT. Five pathways (Pyruvate metabolism; Glycolysis / Gluconeogenesis; Glycine, serine, and threonine metabolism; Glyoxylate and dicarboxylate metabolism; and Alanine, aspartate and glutamate metabolism) are affected, demonstrating the metabolic dysregulation due to RT. The pyruvate metabolism was overpresented with the high Pathway Impact score.

CONCLUSION

Salivary metabolomics analysis revealed significant alterations in the metabolic profile of HNC patients undergoing RT, providing valuable insights into treatment-induced oral pathobiological changes. Alterations in salivary pathways during RT suggest disturbances in redox homeostasis, oxidative stress, and inflammation. The ability to monitor salivary metabolites and pathways non-invasively holds promise to personalized medicine in HNC treatment by enabling early detection of treatment-related toxicities, monitoring treatment response, and tailoring interventions to patient needs.

Effect of Synbiotic and Postbiotic Supplements on Dental Caries and Periodontal Diseases-A Comprehensive Review

Caries and periodontitis affect a significant part of the global population. Regular oral hygiene, sugar restriction, and fluoride exposure are the main avenues for the maintenance of oral health, but the adjunctive use of prebiotics and probiotic bacteria has gained attention over the past decades. The microbial and clinical effects of these biological interventions have been thoroughly covered in systematic reviews. However, the combination of prebiotics and probiotics (synbiotics) may boost the clinical benefits, and postbiotics, being inanimate microorganisms, can, when added to oral hygiene products, offer a sustainable option. The aim of this narrative review was to summarize clinical trials on the adjunctive use of synbiotics and postbiotics in the prevention and management of dental caries, gingivitis, and periodontitis. We searched two databases (PubMed and Google Scholar) for relevant literature, and we identified 17 relevant papers, five on dental caries and 12 with periodontal endpoints. We found emerging evidence of low certainty that lozenges/tablets containing synbiotics or postbiotics could reduce caries incidence in preschool and schoolchildren in comparison with standard preventive care. The effect on adult patients with plaque-induced gingivitis was less consistent. For adults with periodontitis, the adjunctive use of synbiotic and postbiotic products seemed to enhance the outcome of conventional scaling and root planning. In conclusion, both dental caries and periodontitis are non-communicable diseases, closely associated with an unbalanced oral biofilm, and the application of microbial modulators, including synbiotics and postbiotics, display promising beneficial effects and warrant further research.

Metagenomic Analysis of the Buccal Microbiome by Nanopore Sequencing Reveals Structural Differences in the Microbiome of a Patient with Molar Incisor Hypomineralization (MIH) Compared to a Healthy Child-Case Study

Molar incisor hypomineralization (MIH) is a qualitative developmental defect that affects the enamel tissue of permanent molars and can also occur in permanent incisors. Enamel affected by MIH has reduced hardness, increased porosity, and a higher organic content than unaffected enamel. These characteristics predispose the enamel to accumulation of bacteria and a higher prevalence of caries lesions. Through a groundbreaking metagenomic analysis of the buccal mucosal sample from a patient with MIH, we explored the intricacies of its microbiome compared to a healthy control using state-of-the-art nanopore long-read sequencing. Out of the 210 bacterial taxa identified in the MIH microbiome, we found Streptococcus and Haemophilus to be the most abundant genera. The bacteria with the highest read counts in the patient with MIH included Streptococcus mitis, Haemophilus parainfluenzae, Streptococcus pneumoniae, Rothia dentocariosa, and Gemella haemolysans. Our results revealed a striking contrast between healthy and MIH affected children, with a higher dominance and number of pathogenic species (S. pneumoniae, H. influenzae, and N. meningitidis) and reduced diversity in the MIH-affected patient. This distinct microbial profile not only sheds light on MIH-affected patients, but paves the way for future research, inspiring deeper understanding and larger scale studies.

Findings and methodologies in oral phageome research: a systematic review

Background

The oral microbiome serves as both an indicator and a mediator of oral health. Evidence indicates that bacteriophages (phages) are widely present in the oral microbiome and exhibit diverse classifications and interactions with human cells and other microbes. These phages constitute the oral phageome, which potentially exerts significant yet unexplored effects on the interplay between oral and general health.

Methods

Three databases (PubMed/MEDLINE, Embase and Scopus) were searched for metagenomic analyses that investigated the oral phageome. Eligible studies were synthesized based on their methodological approaches and findings.

Results

A total of 14 articles were included in this systematic review. Among the 14 articles included, there were six studies that discussed disease-related alterations, along with a discursive examination of additional variables such as sampling niches, external interventions and methodologies. The phages that infect Streptococcus Actinomyces Haemophilus, and Veillonella have been discovered to be associated with chronic periodontitis, caries, and pancreatic ductal carcinoma.

Conclusions

This systematic review focuses on findings and methodologies in oral phageome studies, which were conducted using highly heterogeneous methodologies that explored the oral phageome in multiple directions while placing constraints on quantitative statistics. Combining different kinds of sample types, utilizing the characteristics of different methods, involving both DNA and RNA phages, and differentiating lysogenic and lytic phages should be the distinction of further studies.

The Microbiome's Role in Chronic Pain and Inflammation

Context

Pain is a universal experience, one that is meant to protect people from further harm or injury, and chronic pain is prominent worldwide. Inflammation plays a central role in chronic pain.

Objective

The review intended to examine the epidemiology of chronic pain, the ways in which inflammation contributes to it, and the microbiome's role in it, evaluating the function of the oral microbiome and dietary factors.

Results

The inflammatory response plays a pivotal role in the transition from acute to chronic pain, with various mediators orchestrating a cascade of events that perpetuate pain signaling and sensitization. The microbiome interacts directly with the immune system and plays a fundamental role in addressing inflammation and chronic pain. Dysbiosis within the gut and oral microbiota can fuel systemic inflammation, exacerbating pain symptoms and influencing pain perception through the gut-brain axis. Additionally, microbial metabolites can influence immune function, reducing or perpetuating inflammation, which can further affect the experience of pain. Dietary factors also contribute significantly to inflammation and pain, and poor nutritional choices can exacerbate immune responses and trigger low-grade inflammation, perpetuating chronic-pain conditions.

Conclusions

Moving forward, a holistic approach to chronic pain management is imperative, addressing not only the symptoms but also the underlying inflammatory processes and systemic contributors. Embracing interdisciplinary collaboration and personalized treatment tailored to the individual patient's needs will be essential in alleviating chronic pain and improving overall quality of life. Through continued research and clinical innovation, healthcare practitioners can work towards more effective and compassionate care for those living with chronic pain.

Application of Metagenomics Sequencing in a Patient with Dementia: A New Case Report

(1) Background: The study of the microbiome is crucial for its role in major systemic diseases, in particular the oral and gut microbiota. In recent years, the study of microorganisms correlated, for example, with neurodegenerative disease has increased the prospect of a possible link between gut microbiota and the brain. Here, we report a new case concerning a patient who was initially evaluated genetically for dementia and late-onset dyskinesia, and later tested with 16S metagenomics sequencing. (2) Methods: Starting from a buccal swab, we extracted bacterial DNA and then we performed NGS metagenomics sequencing based on the amplification of the hypervariable regions of the 16S rRNA gene in bacteria. (3) Results: The sequencing revealed the presence of the Spirochaetes phylum, a pathogenic bacterium generally known to be capable of migrating to the Central Nervous System. (4) Conclusions: Oral infections, as our results suggest, could be possible contributing factors to various neurodegenerative conditions.

The Effects of Recreational and Pharmaceutical Substance Use on Oral Microbiomes and Health

Oral health remains one of the most taken for granted parts of human body health, even though poor oral health has now been linked to various diseases, such as cancers, diabetes, autoimmune complications, neurological disorders, and cardiovascular disease, just to name a few. As we review in this paper, substance use or abuse, including alcohol, smoking, recreational drugs, and pharmaceutical drugs can have significant implications on oral health, which in turn can lead to more systemic diseases. In this paper, we show that oral microbiome dysbiosis and inflammatory cytokine pathways are two of the most significant mechanisms contributing to oral health complications from substance use. When substance use decreases beneficial oral species and increases periodontopathogenic strains, a subsequent cascade of oncogenic and inflammatory cytokines is triggered. In this review, we explore these mechanisms and others to determine the consequences of substance use on oral health. The findings are of significance clinically and in research fields as the substance-use-induced deterioration of oral health significantly reduces quality of life and daily functions. Overall, the studies in this review may provide valuable information for future personalized medicine and safer alternatives to legal and pharmaceutical substances. Furthermore, they can lead towards better rehabilitation or preventative initiatives and policies, as it is critical for healthcare and addiction aid specialists to have proper tools at their disposal.

New Insights Regarding the Use of Relevant Synthetic Compounds in Dentistry

Worldwide, synthetic compounds are used for both in-office and at-home dental care. They are a valuable resource for both prophylactic and curative treatments for various dental problems, such as tooth decay, periodontal diseases, and many more. They are typically preferred due to their broad range of actions and ability to produce targeted, rapid, and long-lasting effects. Using a 0.12% chlorhexidine mouthwash is capable of reducing the plaque index from 47.69% to 2.37% and the bleeding index from 32.93% to 6.28% after just 2 weeks. Mouthwash with 0.1% OCT is also highly effective, as it significantly lowered the median plaque index and salivary bacterial counts in 152 patients in 5 days compared to a control group (p < 0.0001), while also reducing the gingival index (p < 0.001). When povidone-iodine was used as an irrigant during the surgical removal of mandibular third molars in 105 patients, it resulted in notably lower pain scores after 2 days compared to a control group (4.57 ± 0.60 vs. 5.71 ± 0.45). Sodium hypochlorite is excellent for root canal disinfection, as irrigating with 1% NaOCl completely eliminated the bacteria from canals in 65% patients. A 0.05% CPC mouthwash proved effective for perioperative patient care, significantly decreasing gingival bleeding (p < 0.001) and suppressing Streptococcus levels even one week post-surgery. Lastly, a 6% H2O2 paint-on varnish and 6% H2O2 tray formulations successfully bleached the teeth of 40 patients, maintaining a noticeably whiter appearance up to the 6-month follow-up, with significant color differences from the baseline (p < 0.005). Synthetic compounds have a large research base, which also provides a greater awareness of their mechanism of action and potential adverse effects. For a better understanding of how they work, several methods and assays are performed. These are protocolary techniques through which a compound's efficacy and toxicity are established.

The hidden link: How oral and respiratory microbiomes affect multiple sclerosis

BACKGROUND

Extensive research has explored the role of gut microbiota in multiple sclerosis (MS). However, the impact of microbial communities in the oral cavity and respiratory tract on MS is an emerging area of investigation.

PURPOSE

We aimed to review the current literature related to the nasal, oral, and lung microbiota in people with MS (PwMS).

METHODS

We conducted a narrative review of clinical and preclinical original studies on PubMed that explored the relationship between the bacterial or viral composition of the nasal, lung, and oral microbiota and MS. Additionally, to find relevant studies not retrieved initially, we also searched for references in related review papers, as well as the references cited within the included studies.

RESULTS AND CONCLUSIONS

Thirteen studies were meticulously reviewed in three sections; oral microbiota (n = 8), nasal microbiota (n = 3), and lung microbiota (n = 2), highlighting considerable alterations in the oral and respiratory microbiome of PwMS compared to healthy controls (HCs). Genera like Aggregatibacter and Streptococcus were less abundant in the oral microbiota of PwMS compared to HCs, while Staphylococcus, Leptotrichia, Fusobacterium, and Bacteroides showed increased abundance in PwMS. Additionally, the presence of specific bacteria, including Streptococcus sanguinis, within the oral microbiota was suggested to influence Epstein-Barr virus reactivation, a well-established risk factor for MS. Studies related to the nasal microbiome indicated elevated levels of specific Staphylococcus aureus toxins, as well as nasal glial cell infection with human herpes virus (HHV)-6 in PwMS. Emerging research on lung microbiome in animal models demonstrated that manipulating the lung microbiome towards lipopolysaccharide-producing bacteria might suppress MS symptoms. These findings open avenues for potential therapeutic strategies. However, further research is crucial to fully understand the complex interactions between the microbiome and MS. This will help identify the most effective timing, bacterial strains, and modulation techniques.

Microbiome in the nasopharynx: Insights into the impact of COVID-19 severity

Background

The respiratory tract harbors a variety of microbiota, whose composition and abundance depend on specific site factors, interaction with external factors, and disease. The aim of this study was to investigate the relationship between COVID-19 severity and the nasopharyngeal microbiome.

Methods

We conducted a prospective cohort study in Mexico City, collecting nasopharyngeal swabs from 30 COVID-19 patients and 14 healthy volunteers. Microbiome profiling was performed using 16S rRNA gene analysis. Taxonomic assignment, classification, diversity analysis, core microbiome analysis, and statistical analysis were conducted using R packages.

Results

The microbiome data analysis revealed taxonomic shifts within the nasopharyngeal microbiome in severe COVID-19. Particularly, we observed a significant reduction in the relative abundance of Lawsonella and Cutibacterium genera in critically ill COVID-19 patients (p < 0.001). In contrast, these patients exhibited a marked enrichment of Streptococcus, Actinomyces, Peptostreptococcus, Atopobium, Granulicatella, Mogibacterium, Veillonella, Prevotella_7, Rothia, Gemella, Alloprevotella, and Solobacterium genera (p < 0.01). Analysis of the core microbiome across all samples consistently identified the presence of Staphylococcus, Corynebacterium, and Streptococcus.

Conclusions

Our study suggests that the disruption of physicochemical conditions and barriers resulting from inflammatory processes and the intubation procedure in critically ill COVID-19 patients may facilitate the colonization and invasion of the nasopharynx by oral microorganisms.

Impact of HbA1c control and type 2 diabetes mellitus exposure on the oral microbiome profile in the elderly population

Objective

To investigate the associations of the oral microbiome status with diabetes characteristics in elderly patients with type 2 diabetes mellitus.

Methods

A questionnaire was used to assess age, sex, smoking status, drinking status, flossing frequency, T2DM duration and complications, and a blood test was used to determine the glycated haemoglobin (HbA1c) level. Sequencing of the V3-V4 region of the 16S rRNA gene from saliva samples was used to analyze the oral microbiome.

Results

Differential analysis revealed that Streptococcus and Weissella were significantly enriched in the late-stage group, and Capnocytophaga was significantly enriched in the early-stage group. Correlation analysis revealed that diabetes duration was positively correlated with the abundance of Streptococcus (r= 0.369, p= 0.007) and negatively correlated with the abundance of Cardiobacterium (r= -0.337, p= 0.014), and the level of HbA1c was not significantly correlated with the oral microbiome. Network analysis suggested that the poor control group had a more complex microbial network than the control group, a pattern that was similar for diabetes duration. In addition, Streptococcus has a low correlation with other microorganisms.

Conclusion

In elderly individuals, Streptococcus emerges as a potential biomarker linked to diabetes, exhibiting elevated abundance in diabetic patients influenced by disease exposure and limited bacterial interactions.

Salivary Metabolites Produced by Oral Microbes in Oral Diseases and Oral Squamous Cell Carcinoma: A Review

In recent years, salivary metabolome studies have provided new biological information and salivary biomarkers to diagnose different diseases at early stages. The saliva in the oral cavity is influenced by many factors that are reflected in the salivary metabolite profile. Oral microbes can alter the salivary metabolite profile and may express oral inflammation or oral diseases. The released microbial metabolites in the saliva represent the altered biochemical pathways in the oral cavity. This review highlights the oral microbial profile and microbial metabolites released in saliva and its use as a diagnostic biofluid for different oral diseases. The importance of salivary metabolites produced by oral microbes as risk factors for oral diseases and their possible relationship in oral carcinogenesis is discussed.

How probiotics, prebiotics, synbiotics, and postbiotics prevent dental caries: an oral microbiota perspective

Dental caries, a highly prevalent oral disease, impacts a significant portion of the global population. Conventional approaches that indiscriminately eradicate microbes disrupt the natural equilibrium of the oral microbiota. In contrast, biointervention strategies aim to restore this balance by introducing beneficial microorganisms or inhibiting cariogenic ones. Over the past three decades, microbial preparations have garnered considerable attention in dental research for the prevention and treatment of dental caries. However, unlike related pathologies in the gastrointestinal, vaginal, and respiratory tracts, dental caries occurs on hard tissues such as tooth enamel and is closely associated with localized acid overproduction facilitated by cariogenic biofilms. Therefore, it is insufficient to rely solely on previous mechanisms to delineate the role of microbial preparations in the oral cavity. A more comprehensive perspective should involve considering the concepts of cariogenic biofilms. This review elucidates the latest research progress, mechanisms of action, challenges, and future research directions regarding probiotics, prebiotics, synbiotics, and postbiotics for the prevention and treatment of dental caries, taking into account the unique pathogenic mechanisms of dental caries. With an enhanced understanding of oral microbiota, personalized microbial therapy will emerge as a critical future research trend.

Oral bacteriophages: metagenomic clues to interpret microbiomes

Bacteriophages are bacterial viruses that are distributed throughout the environment. Lytic phages and prophages in saliva, oral mucosa, and dental plaque interact with the oral microbiota and can change biofilm formation. The interactions between phages and bacteria can be considered a portion of oral metagenomics. The metagenomic profile of the oral microbiome indicates various bacteria. Indeed, there are various phages against these bacteria in the oral cavity. However, some other phages, like phages against Absconditabacteria, Chlamydiae, or Chloroflexi, have not been identified in the oral cavity. This review gives an overview of oral bacteriophage and used for metagenomics. Metagenomics of these phages deals with multi-drug-resistant bacterial plaques (biofilms) in oral cavities and oral infection. Hence, dentists and pharmacologists should know this metagenomic profile to cope with predental and dental infectious diseases.

Polyphasic molecular approach to the characterization of methanogens in the saliva of Tunisian adults

OBJECTIVES

Methanogenic archaea are a minor component of human oral microbiota. Due to their relatively low abundance, the detection of these neglected microorganisms is challenging. This study concerns the presence of methanogens in salivary samples collected from Tunisian adults to evaluate their prevalence and burden using a polyphasic molecular approach.

METHODS

A total of 43 saliva samples were included. Metagenomic and standard 16S rRNA sequencing were performed as an initial screening to detect the presence of methanogens in the oral microbiota of Tunisian adults. Further investigations were performed using specific quantitative real-time PCR targeting Methanobrevibacter oralis and Methanobrevibacter smithii.

RESULTS

Methanobrevibacter was detected in 5/43 (11.62 %) saliva samples after metagenomic 16S rRNA data analysis. The presence of M. oralis was confirmed in 6/43 samples by standard 16S rRNA sequencing. Using real-time PCR, methanogens were detected in 35/43 (81.39 %) samples, including 62.79 % positive for M. oralis and 76.74 % positive for M. smithii. These findings reflect the high prevalence of both methanogens, revealed by the high sensitivity of the real-time PCR approach. Interestingly, we also noted a significant statistical association between the detection of M. smithii and poor adherence to a Mediterranean diet, indicating the impact of diet on M. smithii prevalence.

CONCLUSION

Our study showed the presence of methanogens in the oral microbiota of Tunisian adults with an unprecedented relatively high prevalence. Choice of methodology is also central to picturing the real prevalence and diversity of such minor taxa in the oral microbiota.

Interaction between microorganisms and dental material surfaces: general concepts and research progress

Bacterial adhesion to dental materials’ surfaces is the initial cause of dental materials-related infections. Therefore, inhibiting bacterial adhesion is a critical step in preventing and controlling these infections. To this end, it is important to know how the properties of dental materials affect the interactions between microorganisms and material surfaces to produce materials without biological contamination. This manuscript reviews the mechanism of bacterial adhesion to dental materials, the relationships between their surface properties and bacterial adhesion, and the impact of bacterial adhesion on their surface properties. In addition, this paper summarizes how these surface properties impact oral biofilm formation and proposes designing intelligent dental material surfaces that can reduce biological contamination.

Emergency diagnosis made easy: matrix removal and analyte enrichment from raw saliva using paper-arrow mass spectrometry

Paracetamol overdose is a leading cause of acute liver failure that can prove fatal. Establishing paracetamol concentration accurately and quickly is critical. Current detection methods are invasive, time-consuming and/or expensive. Non-invasive, rapid and cost-effective techniques are urgently required. To address this challenge, a novel approach, called Paper-Arrow Mass Spectrometry (PA-MS) has been developed. This technique combines sample collection, extraction, enrichment, separation and ionisation onto a single paper strip, and the entire analysis process, from sample to result, can be carried out in less than 10 min requiring only 2 μL of raw human saliva. PA-MS achieved a LOQ of 185 ng mL-1, mean recovery of 107 ± 7%, mean accuracy of 11 ± 8% and precision ≤5% using four concentrations, and had excellent linearity (r2 = 0.9988) in the range of 0.2-200 μg mL-1 covering the treatment concentration range, surpassing the best-in-class methods currently available for paracetamol analysis. Furthermore, from a panel of human saliva samples, inter-individual variability was found to be <10% using this approach. This technique represents a promising tool for rapid and accurate emergency diagnosis.

The Complicated Relationship of Short-Chain Fatty Acids and Oral Microbiome: A Narrative Review

The human oral microbiome has emerged as a focal point of research due to its profound implications for human health. The involvement of short-chain fatty acids in oral microbiome composition, oral health, and chronic inflammation is gaining increasing attention. In this narrative review, the results of early in vitro, in vivo, and pilot clinical studies and research projects are presented in order to define the boundaries of this new complicated issue. According to the results, the current research data are disputable and ambiguous. When investigating the role of SCFAs in human health and disease, it is crucial to distinguish between their local GI effects and the systemic influences. Locally, SCFAs are a part of normal oral microbiota metabolism, but the increased formation of SCFAs usually attribute to dysbiosis; excess SCFAs participate in the development of local oral diseases and in oral biota gut colonization and dysbiosis. On the other hand, a number of studies have established the positive impact of SCFAs on human health as a whole, including the reduction of chronic systemic inflammation, improvement of metabolic processes, and decrease of some types of cancer incidence. Thus, a complex and sophisticated approach with consideration of origin and localization for SCFA function assessment is demanded. Therefore, more research, especially clinical research, is needed to investigate the complicated relationship of SCFAs with health and disease and their potential role in prevention and treatment.

A comparative evaluation of the antimicrobial effect of chamomile, Aloe vera-green tea, and chlorhexidine mouthwashes on some oral bacterial species

Background

Plant compounds such as Aloe vera, green tea, and chamomile have been increasingly used in recent years to achieve oral health. This study aimed to determine the antimicrobial effect of chamomile (Matrika), A. vera-green tea, and chlorhexidine (CHX) mouthwashes on some oral bacterial species.

Materials and Methods

This prospective experimental study investigated the antimicrobial properties of three mouthwashes, including chamomile (Matrika), A. vera -green tea, and CHX as well as distilled water as control on five bacterial species, including Streptococcus Oralis, Streptococcus sanguis, and Streptococcus mutans as primary colonizers and Porphyromonas gingivalis and Eikenella corrodens as secondary colonizers. Colony-forming unit was used to count the colonies and disc diffusion and well diffusion methods were used to measure the diameter of zone of inhibition. Data were analyzed by SPSS (version 22) software using descriptive statistics, ANOVA, Tukey, Kruskal-Wallis, and Mann-Whitney tests (α = 0.05).

Results

CHX had a significantly higher antibacterial effect than the other two mouthwashes in all three methods (P < 0.001). Further, the herbal mouthwashes in all three methods had a statistically significant effect on the bacterial species (P < 0.001). A. vera-green tea mouthwash had a significantly higher effect than chamomile mouthwash (Matrika) on all bacterial species except for S. sanguis (P < 0.05).

Conclusion

The findings showed that herbal mouthwashes had potentially antibacterial effects, but these effects were significantly lower than that of CHX. However, more clinical studies are needed to prove the current findings.

Pathways to healing: Plants with therapeutic potential for neurodegenerative diseases

Some of the greatest challenges in medicine are the neurodegenerative diseases (NDs), which remain without a cure and mostly progress to death. A companion study employed a toolkit methodology to document 2001 plant species with ethnomedicinal uses for alleviating pathologies relevant to NDs, focusing on its relevance to Alzheimer's disease (AD). This study aimed to find plants with therapeutic bioactivities for a range of NDs. 1339 of the 2001 plant species were found to have a bioactivity from the literature of therapeutic relevance to NDs such as Parkinson's disease, Huntington's disease, AD, motor neurone diseases, multiple sclerosis, prion diseases, Neimann-Pick disease, glaucoma, Friedreich's ataxia and Batten disease. 43 types of bioactivities were found, such as reducing protein misfolding, neuroinflammation, oxidative stress and cell death, and promoting neurogenesis, mitochondrial biogenesis, autophagy, longevity, and anti-microbial activity. Ethno-led plant selection was more effective than random selection of plant species. Our findings indicate that ethnomedicinal plants provide a large resource of ND therapeutic potential. The extensive range of bioactivities validate the usefulness of the toolkit methodology in the mining of this data. We found that a number of the documented plants are able to modulate molecular mechanisms underlying various key ND pathologies, revealing a promising and even profound capacity to halt and reverse the processes of neurodegeneration.

Smart dental materials for antimicrobial applications

Smart biomaterials can sense and react to physiological or external environmental stimuli (e.g., mechanical, chemical, electrical, or magnetic signals). The last decades have seen exponential growth in the use and development of smart dental biomaterials for antimicrobial applications in dentistry. These biomaterial systems offer improved efficacy and controllable bio-functionalities to prevent infections and extend the longevity of dental devices. This review article presents the current state-of-the-art of design, evaluation, advantages, and limitations of bioactive and stimuli-responsive and autonomous dental materials for antimicrobial applications. First, the importance and classification of smart biomaterials are discussed. Second, the categories of bioresponsive antibacterial dental materials are systematically itemized based on different stimuli, including pH, enzymes, light, magnetic field, and vibrations. For each category, their antimicrobial mechanism, applications, and examples are discussed. Finally, we examined the limitations and obstacles required to develop clinically relevant applications of these appealing technologies.

Association of polymicrobial interactions with dental caries development and prevention

Dental caries is a common oral disease. In many cases, disruption of the ecological balance of the oral cavity can result in the occurrence of dental caries. There are many cariogenic microbiota and factors, and their identification allows us to take corresponding prevention and control measures. With the development of microbiology, the caries-causing bacteria have evolved from the traditional single Streptococcus mutans to the discovery of oral symbiotic bacteria. Thus it is necessary to systematically organized the association of polymicrobial interactions with dental caries development. In terms of ecology, caries occurs due to an ecological imbalance of the microbiota, caused by the growth and reproduction of cariogenic microbiota due to external factors or the disruption of homeostasis by one's own factors. To reduce the occurrence of dental caries effectively, and considering the latest scientific viewpoints, caries may be viewed from the perspective of ecology, and preventive measures can be taken; hence, this article systematically summarizes the prevention and treatment of dental caries from the aspects of ecological perspectives, in particular the ecological biofilm formation, bacterial quorum sensing, the main cariogenic microbiota, and preventive measures.

Cross-kingdom Microbial Interactions Within the Oral Cavity and Their Implications for Oral Disease

Purpose of Review

This review serves to highlight the cross-kingdom interactions that can occur within the human oral cavity between fungus Candida albicans and oral bacteria, and their impact on the delicate balance between oral health and disease.

Recent Findings

A growing number of physical, chemical, and metabolic networks have been identified that underpin these cross-kingdom interactions. Moreover, these partnerships are often synergistic and can modulate microbial burden or virulence. This, in turn, can drive the onset or progression of oral diseases such as dental caries, periodontitis, denture-associated stomatitis, and oral cancer.

Summary

The impact of cross-kingdom interactions on the cellular, biochemical, and communal composition of oral microbial biofilms is increasingly clear. With growing insight into these processes at the molecular level, so this knowledge can be used to better inform the development of novel strategies to manipulate the oral microbiota to promote oral health and combat oral disease.

The Role of the Mycobiome in Women’s Health

Although the human bacteriome and virome have gained a great deal of attention over the years, the human mycobiome has been far more neglected despite having significant value and implications in human health. In women, mycobiome profiles in breastmilk, vaginal regions, the gut, skin, and the oral cavity can provide insight into women’s health, diseases, and microbiome dysbiosis. Analyses of mycobiome composition under factors, such as health, age, diet, weight, and drug exposure (including antibiotic therapies), help to elucidate the various roles of women’s mycobiome in homeostasis, microbiome interactions (synergistic and antagonistic), and health. This review summarizes the most recent updates to mycobiome knowledge in these critical areas.

Antibacterial and Antibiofilm Activity of Carvacrol against Oral Pathogenic Bacteria

Faced with the current situation of high rates of microbial resistance, together with the scarcity of new antibiotics, it is necessary to search for and identify new antimicrobials, preferably natural, to alleviate this situation. The aim of this work was to evaluate the antibacterial activity of carvacrol (CAR), a phenolic compound of essential oils, against pathogenic microorganisms causing oral infections, such as Streptococcus mutans and S. sanguinis, never evaluated before. The minimum inhibitory and the minimum bactericidal concentration were 93.4 μg/mL and 373.6 μg/mL, respectively, for the two strains. The growth kinetics under different concentrations of CAR, as well as the bactericidal power were determined. The subinhibitory concentrations delayed and decreased bacterial growth. Its efficacy on mature biofilms was also tested. Finally, the possible hemolytic effect of CAR, not observable at the bactericidal concentrations under study, was evaluated. Findings obtained point to CAR as an excellent alternative agent to safely prevent periodontal diseases. In addition, it is important to highlight the use of an experimental methodology that includes dual-species biofilm and subinhibitory concentration models to determine optimal CAR treatment concentrations. Thus, CAR could be used preventively in mouthwashes or biomaterials, or in treatments to avoid existing antibiotic resistance.

Oral microbiota in oropharyngeal cancers: Friend or foe?

Oral microbiome is a complex population of micro-organisms, which by cross-talking with the local immune system, plays a major role in the immune homeostasis of the oral cavity, further contributing in the physiology of the gastro-intestinal microbiota. Understanding their involvement in the onset and pathogenesis of oropharyngeal cancers is paramount, despite very few reports deal with the fundamental role exerted by oral microbiota disorders, such as dysbiosis and impairment in the oral microbiome composition as causative factors in the development of oropharyngeal tumors. Current research, via metabolomic or meta-transcriptomic analyses, is wondering how this complex microbial population regulates the immune homeostasis in oral and pharyngeal mucosa and whether changes in bacterial composition may give insights on the role of oral microbiome in the development of oropharyngeal tumors, so to prevent their occurrence.

Antibacterial efficacy of antibiotic pastes versus calcium hydroxide intracanal dressing: A systematic review and meta-analysis of ex vivo studies

Background

Conflicting findings on the potency of antibiotic pastes versus calcium hydroxide (CH) have been evident in the literature.

Aims

To compare the antibacterial efficacy of single antibiotic paste (SAP), double antibiotic paste (DAP), triple antibiotic paste (TAP), and modified TAP (mTAP) with CH on bacterial biofilms.

Methods

PubMed, Scopus, and Embase were comprehensively searched until August 23, 2021. The study protocol was registered in the PROSPERO. Ex vivo studies performed on Enterococcus faecalis or polymicrobial biofilms incubated on human/bovine dentin were selected. The quality of the studies was assessed using a customized quality assessment tool. Standardized mean difference (SMD) with a 95% confidence interval (CI) was calculated for the meta-analysis. Meta-regression models were used to identify the sources of heterogeneity and to compare the efficacy of pastes.

Results

The qualitative and quantitative synthesis included 40 and 23 papers, respectively, out of 1421 search results. TAP (SMD = -3.82; CI, -5.44 to -2.21; P < 0.001) and SAPs (SMD = -2.38; CI, -2.81 to - 1.94; P < 0.001) had significantly higher antibacterial efficacy compared to the CH on E. faecalis biofilm. However, no significant difference was found between the efficacy of DAP (SMD = -2.74; CI, -5.56-0.07; P = 0.06) or mTAP (SMD = -0.28; CI, -0.82-0.26; P = 0.31) and CH. Meta-regression model on E. faecalis showed that SAPs have similar efficacy compared to TAP and significantly better efficacy than DAP. On dual-species (SMD = 0.15; CI, -1.00-1.29; P = 0.80) or multi-species (SMD = 0.23; CI, -0.08-0.55; P = 0.15) biofilms, DAP and CH had similar efficacy.

Conclusions

Ex vivo evidence showed that antibiotic pastes were either superior or equal to CH. The studied SAPs had considerably higher or similar antibacterial effectiveness compared to DAP, CH, and TAP. Hence, combined antibiotic therapy was not necessarily required for root canal disinfection ex vivo.

Antifungal Activity of Mexican Propolis on Clinical Isolates of Candida Species

Infections caused by micro-organisms of the genus Candida are becoming a growing health problem worldwide. These fungi are opportunistic commensals that can produce infections—clinically known as candidiasis—in immunocompromised individuals. The indiscriminate use of different anti-fungal treatments has triggered the resistance of Candida species to currently used therapies. In this sense, propolis has been shown to have potent antimicrobial properties and thus can be used as an approach for the inhibition of Candida species. Therefore, this work aims to evaluate the anti-Candida effects of a propolis extract obtained from the north of Mexico on clinical isolates of Candida species. Candida species were specifically identified from oral lesions, and both the qualitative and quantitative anti-Candida effects of the Mexican propolis were evaluated, as well as its inhibitory effect on C. albicans isolate’s germ tube growth and chemical composition. Three Candida species were identified, and our results indicated that the inhibition halos of the propolis ranged from 7.6 to 21.43 mm, while that of the MFC and FC₅₀ ranged from 0.312 to 1.25 and 0.014 to 0.244 mg/mL, respectively. Moreover, the propolis was found to inhibit germ tube formation (IC₅₀ ranging from 0.030 to 1.291 mg/mL). Chemical composition analysis indicated the presence of flavonoids, including pinocembrin, baicalein, pinobanksin chalcone, rhamnetin, and biochanin A, in the Mexican propolis extract. In summary, our work shows that Mexican propolis presents significant anti-Candida effects related to its chemical composition, and also inhibits germ tube growth. Other Candida species virulence factors should be investigated in future research in order to determine the mechanisms associated with antifungal effects against them.

Natural products from traditional medicine as promising agents targeting at different stages of oral biofilm development

Oral cavity is an ideal habitat for more than 1,000 species of microorganisms. The diverse oral microbes form biofilms over the hard and soft tissues in the oral cavity, affecting the oral ecological balance and the development of oral diseases, such as caries, apical periodontitis, and periodontitis. Currently, antibiotics are the primary agents against infectious diseases; however, the emergence of drug resistance and the disruption of oral microecology have challenged their applications. The discovery of new antibiotic-independent agents is a promising strategy against biofilm-induced infections. Natural products from traditional medicine have shown potential antibiofilm activities in the oral cavity with high safety, cost-effectiveness, and minimal adverse drug reactions. Aiming to highlight the importance and functions of natural products from traditional medicine against oral biofilms, here we summarized and discussed the antibiofilm effects of natural products targeting at different stages of the biofilm formation process, including adhesion, proliferation, maturation, and dispersion, and their effects on multi-species biofilms. The perspective of antibiofilm agents for oral infectious diseases to restore the balance of oral microecology is also discussed.

Diversity and Biogeography of Human Oral Saliva Microbial Communities Revealed by the Earth Microbiome Project

The oral cavity is an important window for microbial communication between the environment and the human body. The oral microbiome plays an important role in human health. However, compared to the gut microbiome, the oral microbiome has been poorly explored. Here, we analyzed 404 datasets from human oral saliva samples published by the Earth Microbiome Project (EMP) and compared them with 815 samples from the human gut, nose/pharynx, and skin. The diversity of the human saliva microbiome varied significantly among individuals, and the community compositions were complex and diverse. The saliva microbiome showed the lowest species diversity among the four environment types. Human oral habitats shared a small core bacterial community containing only 14 operational taxonomic units (OTUs) under 5 phyla, which occupied over 75% of the sequence abundance. For the four habitats, the core taxa of the saliva microbiome had the greatest impact on saliva habitats than other habitats and were mostly unique. In addition, the saliva microbiome showed significant differences in the populations of different regions, which may be determined by the living environment and lifestyle/dietary habits. Finally, the correlation analysis showed high similarity between the saliva microbiome and the microbiomes of Aerosol (non-saline) and Surface (non-saline), i.e., two environment types closely related to human, suggesting that contact and shared environment being the driving factors of microbial transmission. Together, these findings expand our understanding of human oral diversity and biogeography.

Lactobacillus acidophilus Mitigates Osteoarthritis-Associated Pain, Cartilage Disintegration and Gut Microbiota Dysbiosis in an Experimental Murine OA Model

To test probiotic therapy for osteoarthritis (OA), we administered Lactobacillus acidophilus (LA) by oral gavage (2×/week) after induction of OA by partial medial meniscectomy (PMM). Pain was assessed by von Frey filament and hot plate testing. Joint pathology and pain markers were comprehensively analyzed in knee joints, spinal cords, dorsal root ganglia and distal colon by Safranin O/fast green staining, immunofluorescence microscopy and RT-qPCR. LA acutely reduced inflammatory knee joint pain and prevented further OA progression. The therapeutic efficacy of LA was supported by a significant reduction of cartilage-degrading enzymes, pain markers and inflammatory factors in the tissues we examined. This finding suggests a likely clinical effect of LA on OA. The effect of LA treatment on the fecal microbiome was assessed by 16S rRNA gene amplicon sequencing analysis. LA significantly altered the fecal microbiota compared to vehicle-treated mice (PERMANOVA p < 0.009). Our pre-clinical OA animal model revealed significant OA disease modifying effects of LA as reflected by rapid joint pain reduction, cartilage protection, and reversal of dysbiosis. Our findings suggest that LA treatment has beneficial systemic effects that can potentially be developed as a safe OA disease-modifying drug (OADMD).

Diagnosis and Treatment of Invasive Candidiasis

Candida species, belonging to commensal microbial communities in humans, cause opportunistic infections in individuals with impaired immunity. Pathogens encountered in more than 90% cases of invasive candidiasis include C. albicans, C. glabrata, C. krusei, C. tropicalis, and C. parapsilosis. The most frequently diagnosed invasive infection is candidemia. About 50% of candidemia cases result in deep-seated infection due to hematogenous spread. The sensitivity of blood cultures in autopsy-proven invasive candidiasis ranges from 21% to 71%. Non-cultural methods (beta-D-glucan, T2Candida assays), especially beta-D-glucan in combination with procalcitonin, appear promising in the exclusion of invasive candidiasis with high sensitivity (98%) and negative predictive value (95%). There is currently a clear deficiency in approved sensitive and precise diagnostic techniques. Omics technologies seem promising, though require further development and study. Therapeutic options for invasive candidiasis are generally limited to four classes of systemic antifungals (polyenes, antimetabolite 5-fluorocytosine, azoles, echinocandins) with the two latter being highly effective and well-tolerated and hence the most widely used. Principles and methods of treatment are discussed in this review. The emergence of pan-drug-resistant C. auris strains indicates an insufficient choice of available medications. Further surveillance, alongside the development of diagnostic and therapeutic methods, is essential.