Identification of Salivary Microbiota and Its Association With Host Inflammatory Mediators in Periodontitis

Oral and Gut Microbiota Dysbiosis Due to Periodontitis: Systemic Implications and Links to Gastrointestinal Cancer: A Narrative Review

Periodontitis can disrupt oral and gut microbiota, leading to dysbiosis that affects overall systemic health. Besides the spread of periodontal pathogens by the hematogenous route, they can also be translocated into the gastrointestinal tract, possibly intervening in the neoplastic process in the gastrointestinal tract. This manuscript reviews the relationship between oral and gut microbiota due to periodontitis, discussing systemic health implications and potential links to gastrointestinal cancer. This article highlights the significance and effect of dysbiosis in the gut, emphasizing the importance of maintaining oral health to prevent systemic diseases. Lastly, it will go through therapeutic innovations such as probiotics and oral microbiota analysis tools for systemic disease detection. These findings will mark the integration of oral health management in clinical practice to lower systemic disease risk and improve overall patient outcomes. Aim of work: This manuscript aims to unravel the pathological interaction between oral and gut microbiota and their bidirectional effect on systemic diseases. Materials and methods: The review was performed using the MEDLINE and ScienceDirect databases. Reviewed articles were published in English between the year 2015 and 2024. The search used keywords such as ("oral microbiota" AND "periodontal disease") OR ("oral microbiota" AND "gastrointestinal cancer") OR ("Porphyromonas gingivalis" AND "periodontal disease") OR ("Helicobacter pylori" AND "gastric cancer") OR ("gut microbiome" AND "inflammatory bowel disease") OR ("oral microbiome" AND "systemic diseases"). Conclusions: The dysbiotic change in the oral cavity due to periodontitis is linked directly and indirectly to systemic diseases such as IBS, neurodegenerative diseases, muscle joint diseases, respiratory infections, and gastrointestinal cancer; this underscores the importance of maintaining oral hygiene for prophylaxis of oral diseases and the prevention of systemic diseases. A better understanding of the interconnections between oral health and systemic diseases will integrate oral health management to offer new prevention, diagnostic, and treatment opportunities to improve overall patient outcomes.

Association between Oral Microbiome and Gastroesophageal Reflux Severity

Background/Objectives: Gastroesophageal reflux disease (GORD) is caused by gastric contents refluxing back into the oesophagus and oral cavity. It can lead to injuries to the mucosa in the form of erosion and ulcers. Our past research have shown acid reflux severity and disease progression is associated with alternations in the microbiota of the distal oesophagus. The aim of this study was to explore whether changes in the oral microbiota occurred in GORD patients and establish any associations with reflux severity. Methods: Fresh mouthwash samples were collected from 58 patients experiencing reflux symptoms referred for 24 h pH monitoring. The participants were categorised into three groups based on their DeMeester scores: Normal (<14.72), Mild (14.2-50), and Moderate/severe (>51). Microorganism identity and diversity were generated using hypervariable tag sequencing and analysing the V1-V3 region of the 16S rRNA gene. Results: No differences in microbiota diversity were found in oral microbiota between groups using the Chiao1 diversity index and Shannon diversity index. Microbiota in the Mild group showed reductions in Rothia dentocariosa and Lautropia, while Moryella and Clostridiales_1 were increased compared with the Normal group. In the Moderate/severe group, the abundance of Rothia aeria was reduced compared with the Normal group, while Schwartzia, Rs_045, Paludibacter, S. satelles, Treponema, and T. socranskii all had increased abundance. The abundance of Prevotella pallens was higher in the Mild group compared with Moderate/severe, while S. satelles and Paludibacter abundances were lower. Conclusions: Our study shows the oral microbiome show significant differences between acid reflux severity groups, as categorised by DeMeester score.

Quantifying periodontitis-associated oral dysbiosis in tongue and saliva microbiomes-An integrated data analysis

BACKGROUND

Periodontitis is primarily driven by subgingival biofilm dysbiosis. However, the quantification and impact of this periodontal dysbiosis on other oral microbial niches remain unclear. This study seeks to quantify the dysbiotic changes in tongue and salivary microbiomes resulting from periodontitis by applying a clinically relevant dysbiosis index to an integrated data analysis.

METHODS

The National Center for Biotechnology Information (NCBI) database was searched to identify BioProjects with published studies on salivary and tongue microbiomes of healthy and periodontitis subjects. Raw sequence datasets were processed using a standardized bioinformatic pipeline and categorized by their ecological niche and periodontal status. The subgingival microbial dysbiosis index (SMDI), a dysbiosis index originally developed using the subgingival microbiome, was computed at species and genus levels and customized for each niche. Its diagnostic accuracy for periodontitis was evaluated using receiver operating characteristic curves.

RESULTS

Four studies, contributing 328 microbiome samples, were included. At both species and genus levels, periodontitis samples had a higher SMDI, but the differences were only significant for subgingival biofilm and saliva (p < 0.001). However, SMDI showed good diagnostic accuracy for periodontitis status for all three niches (area under curve ranging from 0.76 to 0.90, p < 0.05). The dysbiosis index of subgingival biofilm was positively correlated with saliva consistently (p < 0.001) and with the tongue at the genus level (p = 0.036).

CONCLUSIONS

While the impact on the tongue microbiome requires further investigation, periodontitis-associated dysbiosis affects the salivary microbiome and is quantifiable using the dysbiosis index. The diagnostic potential of salivary microbial dysbiosis as a convenient periodontal biomarker for assessing periodontal status has potential public health and clinical applications.

PLAIN LANGUAGE SUMMARY

Periodontitis, a severe inflammation of the gums which causes bone loss, is a disease caused by an imbalance of good and bad bacteria under the gums. However, it is unclear how this bacterial imbalance in the gums affects the bacterial balance of other distinct parts of the mouth, such as the saliva and tongue. This study uses bacteria datasets of four previously published studies, contributing a total of 328 bacterial samples. The data were processed using a uniform data analysis workflow, and a bacterial score, the subgingival microbial dysbiosis index (SMDI), previously shown to capture periodontitis-associated bacteria imbalance, was calculated separately for samples from under the gums, the saliva, and the tongue. The SMDI was able to distinguish between health and periodontitis within each oral location, and in general, the scores were higher for periodontitis samples, though this difference was significant only for bacteria under the gums and in saliva. Saliva scores were also consistently correlated with bacteria under the gums. This study shows that periodontitis-associated bacterial imbalances are observed in oral locations beyond just under the gums, particularly the saliva. Thus, saliva bacteria may be used as a convenient biomarker for assessing gum disease, allowing for potential public health and clinical applications.

The salivary microbiome as a diagnostic biomarker of periodontitis: a 16S multi-batch study before and after the removal of batch effects

Introduction

Microbiome-based clinical applications that improve diagnosis related to oral health are of great interest to precision dentistry. Predictive studies on the salivary microbiome are scarce and of low methodological quality (low sample sizes, lack of biological heterogeneity, and absence of a validation process). None of them evaluates the impact of confounding factors as batch effects (BEs). This is the first 16S multi-batch study to analyze the salivary microbiome at the amplicon sequence variant (ASV) level in terms of differential abundance and machine learning models. This is done in periodontally healthy and periodontitis patients before and after removing BEs.

Methods

Saliva was collected from 124 patients (50 healthy, 74 periodontitis) in our setting. Sequencing of the V3-V4 16S rRNA gene region was performed in Illumina MiSeq. In parallel, searches were conducted on four databases to identify previous Illumina V3-V4 sequencing studies on the salivary microbiome. Investigations that met predefined criteria were included in the analysis, and the own and external sequences were processed using the same bioinformatics protocol. The statistical analysis was performed in the R-Bioconductor environment.

Results

The elimination of BEs reduced the number of ASVs with differential abundance between the groups by approximately one-third (Before=265; After=190). Before removing BEs, the model constructed using all study samples (796) comprised 16 ASVs (0.16%) and had an area under the curve (AUC) of 0.944, sensitivity of 90.73%, and specificity of 87.16%. The model built using two-thirds of the specimens (training=531) comprised 35 ASVs (0.36%) and had an AUC of 0.955, sensitivity of 86.54%, and specificity of 90.06% after being validated in the remaining one-third (test=265). After removing BEs, the models required more ASVs (all samples=200-2.03%; training=100-1.01%) to obtain slightly lower AUC (all=0.935; test=0.947), lower sensitivity (all=81.79%; test=78.85%), and similar specificity (all=91.51%; test=90.68%).

Conclusions

The removal of BEs controls false positive ASVs in the differential abundance analysis. However, their elimination implies a significantly larger number of predictor taxa to achieve optimal performance, creating less robust classifiers. As all the provided models can accurately discriminate health from periodontitis, implying good/excellent sensitivities/specificities, the salivary microbiome demonstrates potential clinical applicability as a precision diagnostic tool for periodontitis.

Oral Health and Caries Prevention: How Tongue Hygiene Helps Maintain Balance of Microbiota and Overall Health in Pediatric Patients

BACKGROUND/OBJECTIVES

The tongue harbors about two-thirds of the microorganisms present in the mouth; the stable bacterial population consists mainly of aerobic and facultative anaerobic streptococci. These bacterial colonies, found more frequently on the tongue than on the outside of the hard part of the dental enamel in children younger than 18 months, suggest that the tongue is a potential bacterial reservoir. The aim of this review is to examine the scientific literature to clarify whether the mechanical removal of bacterial biofilm on the tongue can have a positive effect on caries prevention, with the reduction in colony-forming unit (CFU) of salivary streptococcus and the whole-mouth plaque index (FMPS).

METHODS

An open literature search was conducted by using PubMed (MEDLINE), Cochrane Library and Google Scholar. The most studied age range was 9 to 12 years, with groups of children with no caries and groups with a minimum number of two teeth that were reconstructed, decayed and/or missing (DMFS/dmfs > 2) who experienced different tongue hygiene methods for the first time.

RESULTS

Four randomized trials met the search criteria and were included in this review.

CONCLUSIONS

The results obtained suggest that specific tongue hygiene protocols, combined with a healthy diet and lifestyle, could be considered the gold standard to enable more effective primary prevention and improve the health of pediatric patients. This review improves the understanding of the impact of tongue hygiene in controlling the bacteria responsible for the onset of carious disease and its systemic correlates; however, further research with more data is needed to further confirm the findings of this research.

High-Throughput Combined Analysis of Saliva Microbiota and Metabolomic Profile in Chinese Periodontitis Patients: A Pilot Study

The onset and progression of periodontitis involves complicated interactions between the dysbiotic oral microbiota and disrupted host immune-inflammatory response, which can be mirrored by the changes in salivary metabolites profile. This pilot study sought to examine the saliva microbiome and metabolome in the Chinese population by the combined approach of 16s rRNA sequencing and high-throughput targeted metabolomics to discover potential cues for host-microbe metabolic interactions. Unstimulated whole saliva samples were collected from eighteen Stage III and IV periodontitis patients and thirteen healthy subjects. Full-mouth periodontal parameters were recorded. The taxonomic composition of microbiota was obtained by 16s rRNA sequencing, and the metabolites were identified and measured by ultra-high performance liquid chromatography and mass spectrometry-based metabolomic analysis. The oral microbiota composition displayed marked changes where the abundance of 93 microbial taxa differed significantly between the periodontitis and healthy group. Targeted metabolomics identified 103 differential metabolites between the patients and healthy individuals. Functional enrichment analysis demonstrated the upregulation of protein digestion and absorption, histidine metabolism, and nicotinate and nicotinamide metabolism pathways in the dysbiotic microbiota, while the ferroptosis, tryptophan metabolism, glutathione metabolism, and carbon metabolism pathways were upregulated in the patients. Correlation analysis confirmed positive relationships between the clinical parameters, pathogen abundances, and disease-related metabolite levels. The integral analysis of the saliva microbiome and metabolome yielded an accurate presentation of the dysbiotic oral microbiome and functional alterations in host-microbe metabolism. The microbial and metabolic profiling of the saliva could be a potential tool in the diagnosis, prognosis evaluation, and pathogenesis study of periodontitis.

Realizing the clinical utility of saliva for monitoring oral diseases

In the era of personalized/precision health care, additional effort is being expended to understand the biology and molecular mechanisms of disease processes. How these mechanisms are affected by individual genetics, environmental exposures, and behavioral choices will encompass an expanding role in the future of optimally preventing and treating diseases. Considering saliva as an important biological fluid for analysis to inform oral disease detection/description continues to expand. This review provides an overview of saliva as a diagnostic fluid and the features of various biomarkers that have been reported. We emphasize the use of salivary biomarkers in periodontitis and transport the reader through extant literature, gaps in knowledge, and a structured approach toward validating and determine the utility of biomarkers in periodontitis. A summation of the findings support the likelihood that a panel of biomarkers including both host molecules and specific microorganisms will be required to most effectively identify risk for early transition to disease, ongoing disease activity, progression, and likelihood of response to standard periodontal therapy. The goals would be to develop predictive algorithms that serve as adjunctive diagnostic tools which provide the clinician and patient important information for making informed clinical decisions.

Role of Oral Microbiota Dysbiosis in the Development and Progression of Oral Lichen Planus

Oral lichen planus (OLP) is a chronic inflammatory autoimmune disease of the oral cavity with malignant potential affecting 1.01% of the worldwide population. The clinical patterns of this oral disorder, characterized by relapses and remissions of the lesions, appear on buccal, lingual, gingival, and labial mucosa causing a significant reduction in the quality of life. Currently, there are no specific treatments for this disease, and the available therapies with topical and systemic corticosteroids only reduce symptoms. Although the etiopathogenesis of this pathological condition has not been completely understood yet, several exogenous and endogenous risk factors have been proposed over the years. The present review article summarized the underlying mechanisms of action involved in the onset of OLP and the most well-known triggering factors. According to the current data, oral microbiota dysbiosis could represent a potential diagnostic biomarker for OLP. However, further studies should be undertaken to validate their use in clinical practice, as well as to provide a better understanding of mechanisms of action and develop novel effective intervention strategies against OLP.

Impact of Periodontitis on the Leakage of Oral Bacteria to the Gut

Colorectal cancer (CRC) and periodontitis have recently been related due to the higher incidence of CRC in periodontal patients and the involvement of periodontal pathogens in carcinogenesis, suggesting that leakage from the oral cavity to the gut occurs. However, the magnitude of this pass-through in healthy individuals is controversial, and the effect that periodontitis could play in it is understudied. To evaluate the rate of bacterial leakage from the oral cavity to the gut, we analyzed the microbial composition of saliva, subgingival plaque, and fecal samples in healthy individuals without gastrointestinal disorders, including 20 periodontitis patients and 20 oral healthy controls, using PacBio full-length 16S rRNA gene sequencing. As expected, we observed a higher abundance of periodontal pathogens in the subgingival plaque and saliva of periodontal patients. In contrast, no significant differences were found between the fecal samples of both groups, implying that gut samples from periodontal patients were not enriched in periodontal pathogens. Fusobacterium nucleatum, a biomarker of CRC, was not found in the fecal samples of any participant. Our study does show a small leakage of some oral bacteria (mainly streptococci) to the gut, regardless of periodontal health status. Future studies should test whether other host factors and/or the preexistence of a gut disorder must be present in addition to periodontitis to promote the colonization of the gut by oral pathogens. The absence of periodontal pathogens in feces supports the idea that these bacteria could be used as biomarkers of intestinal disorders, including CRC.

Comparison of the main pathogenic microorganisms of various common oral diseases in children and adults

The microorganisms in the human body gradually change and maintain a dynamic balance with the development of physiology and pathology. Oral microbiota is one of the most important microbiota in human body. It is not only closely related to the occurrence and development of oral diseases, but also plays an important role in the overall health. In childhood, the population of oral microorganisms is relatively small, but with the growth of age and tooth development, the species and quantity of oral microorganisms are gradually increasing. Different oral diseases also have their corresponding main microorganisms, and these dominant microorganisms change at different stages of the disease. In this review, we summarized and compared the main pathogenic microorganisms of several common oral diseases in children and adults. In addition, the possible association and difference between adults and children of the main pathogenic microorganisms in different stages of the same or different diseases are also discussed in order to provide research data for the development and diagnosis of common oral diseases in children and adults.

Salivary microbiome of healthy women of reproductive age

IMPORTANCE

The salivary microbiome has been proven to play a crucial role in local and systemic diseases. Moreover, the effects of biological and lifestyle factors such as oral hygiene and smoking on this microbial community have already been explored. However, what was not yet well understood was the natural variation of the saliva microbiome in healthy women and how this is associated with specific use of hormonal contraception and with the number of different sexual partners with whom microbiome exchange is expected regularly. In this paper, we characterized the salivary microbiome of 255 healthy women of reproductive age using an in-depth questionnaire and self-sampling kits. Using the large metadata set, we were able to investigate the associations of several host-related and lifestyle variables with the salivary microbiome profiles. Our study shows a high preservation between individuals.

Critical review of 16S rRNA gene sequencing workflow in microbiome studies: From primer selection to advanced data analysis

The multi-batch reanalysis approach of jointly reevaluating gene/genome sequences from different works has gained particular relevance in the literature in recent years. The large amount of 16S ribosomal ribonucleic acid (rRNA) gene sequence data stored in public repositories and information in taxonomic databases of the same gene far exceeds that related to complete genomes. This review is intended to guide researchers new to studying microbiota, particularly the oral microbiota, using 16S rRNA gene sequencing and those who want to expand and update their knowledge to optimise their decision-making and improve their research results. First, we describe the advantages and disadvantages of using the 16S rRNA gene as a phylogenetic marker and the latest findings on the impact of primer pair selection on diversity and taxonomic assignment outcomes in oral microbiome studies. Strategies for primer selection based on these results are introduced. Second, we identified the key factors to consider in selecting the sequencing technology and platform. The process and particularities of the main steps for processing 16S rRNA gene-derived data are described in detail to enable researchers to choose the most appropriate bioinformatics pipeline and analysis methods based on the available evidence. We then produce an overview of the different types of advanced analyses, both the most widely used in the literature and the most recent approaches. Several indices, metrics and software for studying microbial communities are included, highlighting their advantages and disadvantages. Considering the principles of clinical metagenomics, we conclude that future research should focus on rigorous analytical approaches, such as developing predictive models to identify microbiome-based biomarkers to classify health and disease states. Finally, we address the batch effect concept and the microbiome-specific methods for accounting for or correcting them.

Mucosal bleeding correlates with submucosal microbial dysbiosis in peri-implant mucositis of patients with periodontitis

OBJECTIVES

This study aimed to investigate the relationship between microbial communities and the severity of peri-implant mucosal bleeding in peri-implant mucositis.

MATERIALS AND METHODS

Submucosal plaque samples were collected from 54 implants divided into the healthy implant (HI) group, peri-implant mucositis (PM) group, and peri-implantitis (PI) group. Sequencing of 16S rRNA was performed using the Illumina MiSeq platform. Alpha diversity (i.e., Shannon and Chao index) and beta diversity were used to measure microbial diversity within and between microbial communities, respectively. Differences in microbial taxa between groups were assessed via linear discriminate analysis effect size. Correlation between the modified sulcus bleeding index (mSBI) and microbial dysbiosis index (MDI) was examined using Spearman correlation analysis and linear models.

RESULTS

The submucosal bacterial richness (Chao index) was positively correlated with the mean mSBI in the PM group. As the mean mSBI increased in the PM group, the beta diversity became closer to that of the PI group. In the PM group, the abundances of 47 genera were significantly correlated with the mean mSBI, and the MDI was positively associated with the mean mSBI. Fourteen of the forty-seven genera were discriminative taxa between the HI and PI groups, and the abundances of these biomarkers became closer to those in the PI group in the progression of peri-implant disease.

CONCLUSIONS

A higher mSBI value corresponded to a higher risk of microbial dysbiosis in peri-implant mucositis. The biomarkers identified may be useful for monitoring the progression of peri-implant disease.

Efficacy of nonsurgical periodontal therapy affecting salivary biomarkers in non-diabetic and type 2 diabetic periodontitis patients. An observational study

Objectives

To assess the effects of non-surgical periodontal therapy on salivary biomarkers in non-diabetic and type 2 diabetic periodontitis patients and to investigate if saliva may be used to monitor glucose levels in type 2 diabetes.

Material and methods

250 participants with chronic generalized periodontitis aged 35-70 years were divided into two groups: test group with type 2 diabetes (125 subjects with 64 males & 61 females) and control group with non-diabetic (125 subjects with 83 males & 42 females). Participants received non-surgical periodontal treatment. Pre-NSPT and 6-week post-NSPT saliva glucose, amylase, total protein, and C-reactive protein (CRP) levels were measured. Intergroup correlations were assessed using Karl Pearson's correlation coefficient and paired t-test.

Results

Non-surgical periodontal therapy significantly decreased CRP (p < 0.05) in diabetics and non-diabetics. CRP mean values changes from baseline 1.79 to post op 1.5 and baseline 1.5 to post-op 1.24 in males and females of test group, respectively. In control group males and females, mean values change from baseline 1.48 to post-op 1.42 and 1.499 to 1.40. Other parameters Glucose, amylase & total protein showed improvement in the level, but statistically non-significant (p > 0.05). Salivary glucose levels corresponded favorably with HbA1C levels.

Conclusion

In individuals with type 2 diabetes and non-diabetic generalized chronic periodontitis, non-surgical periodontal therapy may play a role in lowering the level of significant salivary biomarkers. Saliva can be utilized as a non-invasive approach for monitoring glucose levels in people with type 2 diabetes and chronic periodontitis.

Characteristics of the Salivary Microbiota in Periodontal Diseases and Potential Roles of Individual Bacterial Species To Predict the Severity of Periodontal Disease

The purposes of this study were to examine the compositional changes in the salivary microbiota according to the severity of periodontal disease and to verify whether the distribution of specific bacterial species in saliva can distinguish the severity of disease. Saliva samples were collected from 8 periodontally healthy controls, 16 patients with gingivitis, 19 patients with moderate periodontitis, and 29 patients with severe periodontitis. The V3 and V4 regions of the 16S rRNA gene in the samples were sequenced, and the levels of 9 bacterial species showing significant differences among the groups by sequencing analysis were identified using quantitative real-time PCR (qPCR). The predictive performance of each bacterial species in distinguishing the severity of disease was evaluated using a receiver operating characteristic curve. Twenty-nine species, including Porphyromonas gingivalis, increased as the severity of disease increased, whereas 6 species, including Rothia denticola, decreased. The relative abundances of P. gingivalis, Tannerella forsythia, Filifactor alocis, and Prevotella intermedia determined by qPCR were significantly different among the groups. The three bacterial species P. gingivalis, T. forsythia, and F. alocis were positively correlated with the sum of the full-mouth probing depth and were moderately accurate at distinguishing the severity of periodontal disease. In conclusion, the salivary microbiota showed gradual compositional changes according to the severity of periodontitis, and the levels of P. gingivalis, T. forsythia, and F. alocis in mouth rinse saliva had the ability to distinguish the severity of periodontal disease. IMPORTANCE Periodontal disease is one of the most widespread medical conditions and the leading cause of tooth loss, imposing high economic costs and an increasing burden worldwide as life expectancy increases. Changes in the subgingival bacterial community during the progression of periodontal disease can affect the entire oral ecosystem, and bacteria in saliva can reflect the degree of bacterial imbalance in the oral cavity. This study explored whether the specific bacterial species in saliva can distinguish the severity of periodontal disease by analyzing the salivary microbiota and suggested P. gingivalis, T. forsythia, and F. alocis as biomarkers for distinguishing the severity of periodontal disease in saliva.

Composition of subgingival microbiota associated with periodontitis and diagnosis of malignancy-a cross-sectional study

Periodontitis is one of the world's most prevalent infectious conditions, affecting between 25 and 40% of the adult population. It is a consequence of the complex interactions between periodontal pathogens and their products, which trigger the host inflammatory response, chronic inflammation, and tissue destruction. Chronic systemic low-grade inflammation is involved in numerous diseases, and it is also known that long-lasting inflammation and chronic infections predispose one to cancer. Here, we characterized and compared the subgingival microbiota associated with periodontitis and diagnosis of malignancy in a longitudinal 10-year follow-up study. The study was conducted on 50 patients with periodontitis and 40 periodontally healthy individuals. The recorded clinical oral health parameters were periodontal attachment loss (AL), bleeding on probing (BOP), gingival index (GI), probing depth (PD), and plaque index (PI). Subgingival plaque was collected from each participant, from which DNA was extracted, and 16S rRNA gene amplicon sequencing performed. Cancer diagnoses data were collected between the years 2008-2018 from the Swedish Cancer Registry. The participants were categorized based on having cancer at the time of sample collection (CSC), having developed cancer later (DCL), and controls without any cancer. The most abundant phyla across all 90 samples were Actinobacteria, Proteobacteria, Firmicutes, Bacteroidetes, and Fusobacteria. At the genus level, Treponema, Fretibacterium, and Prevotella were significantly more abundant in samples of periodontitis patients compared to non-periodontitis individuals. With regard to samples of cancer patients, Corynebacterium and Streptococcus were more abundant in the CSC group; Prevotella were more abundant in the DCL group; and Rothia, Neisseria, and Capnocytophaga were more abundant in the control group. In the CSC group, we also found that the presence of periodontal inflammation, in terms of BOP, GI, and PLI, significantly correlated with species belonging to the genera Prevotella, Treponema, and Mycoplasma. Our results revealed that several subgingival genera were differentially enriched among the studied groups. These findings underscore the need for further research to fully understand the role that oral pathogens may play in the development of cancer.

Role of ubiquitin-specific protease 5 in the inflammatory response of chronic periodontitis

BACKGROUND

The systemic inflammatory response caused by chronic periodontitis is a risk factor for multiple diseases. Ubiquitin-specific protease 5 (USP5) is a kind of deubiquitinase which mainly responsible for dissociating unanchored polyubiquitin. However, the functions of USP5 in chronic periodontitis have not been reported.

METHODS

Chronic periodontitis patients were recruited, and their periodontal samples were collected. The levels of USP5, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) in gingival crevicular fluid were evaluated by ELISA. The expression of USP5, TNF-α, IL-6, and IL-1β in human periodontal ligament stem cells (PDLSCs) was estimated by qRT-PCR assay. The activation of STAT3 signaling was examined by Western blot.

RESULTS

USP5 was upregulated in the gingival crevicular fluid and gingival tissues of chronic periodontitis patients. USP5 expression was positively correlated with the expression of proinflammatory factors. USP5 knockdown and deubiquitinase inhibitor inhibited LPS-induced inflammatory responses in PDLSCs. Suppressing USP5 inhibited STAT3 signaling in PDLSCs.

CONCLUSION

Suppression deubiquitinase USP5 inhibits the inflammatory response of chronic periodontitis by suppressing STAT3 signaling.

Oridonin alleviates the inhibitory effect of lipopolysaccharide on the proliferation and osteogenic potential of periodontal ligament stem cells by inhibiting endoplasmic reticulum stress and NF-κB/NLRP3 inflammasome signaling

BACKGROUND

The aim of this study was to investigate the protective effect and mechanism of oridonin in an in vitro lipopolysaccharide (LPS)-induced human periodontal ligament stem cells (hPDLSCs) model of periodontitis.

METHODS

Primary hPDLSCs were isolated and cultured, and then the expression of surface antigens CD146, STRO-1 and CD45 of hPDLSCs was detected by flow cytometry. The mRNA expression level of Runx2, OPN, Col-1, GRP78, CHOP, ATF4 and ATF6 in the cells was tested by qRT-PCR. MTT was taken to determine the cytotoxicity of oridonin at different concentrations (0-4 μM) on hPDLSCs. Besides, ALP staining, alizarin red staining and Oil Red O staining were utilized to assess the osteogenic differentiation (ALP concentration, mineralized calcium nodule formation) and adipogenic differentiation abilities of the cells. The proinflammatory factors level in the cells was measured by ELISA. The protein expression level of NF-κB/NLRP3 pathway-related proteins and endoplasmic reticulum (ER) stress-related markers in the cells were detected by Western blot.

RESULTS

hPDLSCs with positive CD146 and STRO-1 expression and negative CD45 expression were successfully isolated in this study. 0.1-2 μM of oridonin had no significant cytotoxicity on the growth of hPDLSCs, while 2 μM of oridonin could not only greatly reduce the inhibitory effect of LPS on the proliferation and osteogenic differentiation of hPDLSCs cells, but also inhibit LPS-induced inflammation and ER stress in hPDLSCs cells. Moreover, further mechanism research showed that 2 μM of oridonin suppressed NF-κB/NLRP3 signaling pathway activity in LPS-induced hPDLSCs cells.

CONCLUSIONS

Oridonin promotes proliferation and osteogenic differentiation of LPS-induced hPDLSCs in an inflammatory environment, possibly by inhibiting ER stress and NF-κB/NLRP3 pathway. Oridonin may have a potential role in the repair and regeneration of hPDLSCs.

Electroacupuncture regulates macrophage, neutrophil, and oral microbiota to alleviate alveolar bone loss and inflammation in experimental ligature-induced periodontitis

AIM

Electroacupuncture (EA) regulates distant body physiology through somatic sensory autonomic reflexes, balances the microbiome, and can promote the release of immune cells into bloodstream, thereby inhibiting severe systemic inflammation. This makes it possible to use EA as an integrated treatment for periodontitis.

MATERIALS AND METHODS

In this study, EA was applied to the ST36 acupoints in a ligature-induced periodontitis (LIP) mouse model. Then the effects of EA on periodontal myeloid cells, cytokines, and the microbiome were comprehensively analysed using flow cytometry, quantitative Polymerase Chain Reaction (PCR), and 16 S sequencing.

RESULTS

Results demonstrated that EA could significantly relieve periodontal bone resorption. EA also suppressed the infiltration of macrophages and neutrophils, reduced gene expression of the pro-inflammatory cytokines IL-1β, IL-6, IL-17 and TNF-α, and increased expression of the anti-inflammatory factors IL-4 and IL-10 in periodontal tissues. Moreover, composition of the periodontal microbiome was regulated by EA, finding that complex of microbiota, including supragingival Veillonella, subgingival Streptococcus, and subgingival Erysipelatoclostridium, were significantly reduced. Meanwhile, nitrate and nitrate-related activities of subgingival microbiota were reversed. Network analysis revealed close relationships among Veillonella, Streptococcus, and Bacteroides.

CONCLUSIONS

Our study indicates that EA can effectively alleviate inflammation and bone resorption in LIP mice, potentially via the regulation of myeloid cells, cytokines, and periodontal microbiome.

Oral microbial dysbiosis in patients with periodontitis and chronic obstructive pulmonary disease

Background

Oral microbiota is closely related to the homeostasis of the oral cavity and lungs. To provide potential information for the prediction, screening, and treatment strategies of individuals, this study compared and investigated the bacterial signatures in periodontitis and chronic obstructive pulmonary disease (COPD).

Materials and methods

We collected subgingival plaque and gingival crevicular fluid samples from 112 individuals (31 healthy controls, 24 patients with periodontitis, 28 patients with COPD, and 29 patients with both periodontitis and COPD). The oral microbiota was analyzed using 16S rRNA gene sequencing and diversity and functional prediction analysis were performed.

Results

We observed higher bacterial richness in individuals with periodontitis in both types of oral samples. Using LEfSe and DESeq2 analyses, we found differentially abundant genera that may be potential biomarkers for each group. Mogibacterium is the predominant genus in COPD. Ten genera, including Desulfovibrio, Filifactor, Fretibacterium, Moraxella, Odoribacter, Pseudoramibacter Pyramidobacter, Scardovia, Shuttleworthia and Treponema were predominant in periodontitis. Bergeyella, Lautropia, Rothia, Propionibacterium and Cardiobacterium were the signature of the healthy controls. The significantly different pathways in the Kyoto Encyclopedia of Genes and Genomes (KEGG) between healthy controls and other groups were concentrated in genetic information processing, translation, replication and repair, and metabolism of cofactors and vitamins.

Conclusions

We found the significant differences in the bacterial community and functional characterization of oral microbiota in periodontitis, COPD and comorbid diseases. Compared to gingival crevicular fluid, subgingival plaque may be more appropriate for reflecting the difference of subgingival microbiota in periodontitis patients with COPD. These results may provide potentials for predicting, screening, and treatment strategies for individuals with periodontitis and COPD.

Phocaeicola oris sp. nov., an anaerobic bacterium isolated from the saliva of a patient with oral squamous cell carcinoma

A Gram-stain-negative or -positive, strictly anaerobic, non-spore-forming and pleomorphic bacterium (designated 14-104^T) was isolated from the saliva sample of a patient with oral squamous cell carcinoma. It was an acid-tolerant neutralophilic mesophile, growing at between 20 and 40 °C (with optimum growth at 30 °C) and pH between pH 3.0 and 7.0 (with optimum growth at pH 6.0-7.0). It contained anteiso-C_15 : 0 and C_15 : 0 as the major fatty acids. The genome size of strain 14-104^T was 2.98 Mbp, and the G+C content was 39.6 mol%. It shared <87 % 16S rRNA sequence similarity, <71 % orthologous average nucleotide identity, <76 % average amino acid identity and <68 %% of conserved proteins with its closest relative, Phocaeicola abscessus CCUG 55929^T. Reconstruction of phylogenetic and phylogenomic trees revealed that strain 14-104^T and P. abscessus CCUG 55929^T were clustered as a distinct clade without any other terminal node. The phylogenetic and phylogenomic analyses along with physiological and chemotaxonomic data indicated that strain 14-104^T represents a novel species in the genus Phocaeicola, for which the name Phocaeicola oris sp. nov. is proposed. The type strain is 14-104^T (=BCRC 81305^T= NBRC 115041^T).

Host Genotype Links to Salivary and Gut Microbiota by Periodontal Status

Limited evidence describing how host genetic variants affect the composition of the microbiota is currently available. The aim of this study was to assess the associations between a set of candidate host genetic variants and microbial composition in both saliva and gut in the TwinsUK registry. A total of 1,746 participants were included in this study and provided stool samples. A subset of 1,018 participants also provided self-reported periodontal data, and 396 of those participants provided a saliva sample. Host DNA was extracted from whole-blood samples and processed for Infinium Global screening array, focusing on 37 selected single-nucleotide polymorphisms (SNPs) previously associated with periodontitis. The gut and salivary microbiota of participants were profiled using 16S ribosomal RNA amplicon sequencing. Associations between genotype on the selected SNPs and microbial outcomes, including α diversity, β diversity, and amplicon sequence variants (ASVs), were investigated in a multivariate mixed model. Self-reported periodontal status was also compared with microbial outcomes. Downstream analyses in gut microbiota and salivary microbiota were carried out separately. IL10 rs6667202 and VDR 2228570 SNPs were associated with salivary α diversity, and SNPs in IL10, HSA21, UHRF2, and Fc-γR genes were associated with dissimilarity matrix generated from salivary β diversity. The SNP that was associated with the greatest number of salivary ASVs was VDR 2228570 followed by IL10 rs6667202, and that of gut ASVs was NPY rs2521364. There were 77 salivary ASVs and 39 gut ASVs differentially abundant in self-reported periodontal disease versus periodontal health. The dissimilarity between saliva and gut microbiota within individuals appeared significantly greater in self-reported periodontal cases compared to periodontal health. IL10 and VDR gene variants may affect salivary microbiota composition. Periodontal status may drive variations in the salivary microbiota and possibly, to a lesser extent, in the gut microbiota.

Pathogenetic aspects of the development of psoriatic arthritis in people with generalized chronic periodontitis

The pathogenetic mechanisms of progression of chronic periodontitis and psoriatic arthritis have common components in immune and inflammatory responses.

The pathogenesis of chronic periodontitis involves interaction of microbial and immunological components. As a chronic immune-mediated inflammatory disease and a consequence of an infectious trigger that originally affects gingival soft tissue, periodontitis is typically characterized by periodontal destruction and damage to adjacent connective tissues. Neutrophils contribute to the development of periodontitis and participate in its progression by recruiting T helper 17 cells and stimulating synthesis of the receptor activator of the nuclear factor kappa-β ligand (RANKL), contributing to bone resorption.

Macrophages as producers of proinflammatory cytokines (interleukin (IL)-1β, IL-6, IL-22, IL-23, tumor necrosis factor (TNF)), free radicals, and matrix metalloproteinases contribute to the chronic course of the disease. Tissue destruction results in generation of reactive oxygen species by neutrophils, which, against the background of a decrease in the antioxidant potential, leads to development of oxidative stress. These processes together lead to tooth mobility, formation of periodontal pockets, and bone resorption.

The key factors in the formation of psoriatic arthritis against the background of periodontitis are overproduction of proinflammatory cytokines in target tissues (skin, joints, gingival microflora) and development of an excessive systemic immune response to the microbiota inhabiting the epithelial and periodontal tissues. A statistically confirmed correlation of the progression of periodontal destruction with the presence of psoriatic arthritis proves the significance of the effects of inflammation as a background for the progression of a comorbidity. Increased IL-17 synthesis plays a crucial role in the development of immune responses of pathological bone remodeling and bone resorption in periodontitis and psoriatic arthritis.

Baricitinib alleviates lipopolysaccharide‑induced human periodontal ligament stem cell injury and promotes osteogenic differentiation by inhibiting JAK/STAT signaling

Periodontitis is the chronic inflammation of the periodontal tissue. The present study aimed to investigate the role of baricitinib, a Janus kinase (JAK)1/2 inhibitor, in periodontitis by using a lipopolysaccharide (LPS)-induced human periodontal ligament stem cell (PDLSC) model. The viability of PDLSCs stimulated by LPS was assessed in the presence of baricitinib by Cell Counting Kit-8 assay. The induction of oxidative stress was evaluated by detecting the intracellular reactive oxygen species (ROS) levels, superoxide dismutase (SOD) activity and glutathione (GSH) content. ELISA and reverse transcription-quantitative PCR were used to determine the levels of inflammatory factors TNF-α, IL-1β and IL-6. Alkaline phosphatase (ALP) activity and alizarin red staining were used to assess the osteogenic differentiation of PDLSCs. The expression levels of osteogenic differentiation- and JAK/signal transducer and activator of transcription (STAT) signaling-associated proteins were estimated with western blotting. RO8191, an agonist of the JAK/STAT pathway, was used to treat PDLSCs to investigate the regulatory mechanism of baricitinib. The results indicated that baricitinib elevated the LPS-induced decrease in cell viability. LPS-triggered oxidative stress and inflammation were inhibited by baricitinib, as demonstrated by the decreased levels of ROS, TNF-α, IL-1β, IL-6 and increased levels of SOD and GSH. In addition, baricitinib caused a marked elevation in ALP activity and mineralization ability of PDLSCs, as determined by the upregulated osteocalcin and Runt-related transcription factor 2 expression. Moreover, the expression levels of phosphorylated (p)-JAK1, p-JAK2 and p-STAT3 were downregulated by baricitinib in a dose-dependent manner. Furthermore, addition of RO8191 restored the effect of baricitinib on the induction of oxidative stress, inflammation and osteogenic differentiation of PDLSCs exposed to LPS. Collectively, these findings suggested that baricitinib alleviated oxidative stress and inflammation and promoted osteogenic differentiation of LPS-induced PDLSCs by inhibiting JAK/STAT signaling.

The role of the oral microbiome in smoking-related cardiovascular risk: a review of the literature exploring mechanisms and pathways

Cardiovascular disease is a leading cause of morbidity and mortality. Oral health is associated with smoking and cardiovascular outcomes, but there are gaps in knowledge of many mechanisms connecting smoking to cardiovascular risk. Therefore, the aim of this review is to synthesize literature on smoking and the oral microbiome, and smoking and cardiovascular risk/disease, respectively. A secondary aim is to identify common associations between the oral microbiome and cardiovascular risk/disease to smoking, respectively, to identify potential shared oral microbiome-associated mechanisms. We identified several oral bacteria across varying studies that were associated with smoking. Atopobium, Gemella, Megasphaera, Mycoplasma, Porphyromonas, Prevotella, Rothia, Treponema, and Veillonella were increased, while Bergeyella, Haemophilus, Lautropia, and Neisseria were decreased in the oral microbiome of smokers versus non-smokers. Several bacteria that were increased in the oral microbiome of smokers were also positively associated with cardiovascular outcomes including Porphyromonas, Prevotella, Treponema, and Veillonella. We review possible mechanisms that may link the oral microbiome to smoking and cardiovascular risk including inflammation, modulation of amino acids and lipids, and nitric oxide modulation. Our hope is this review will inform future research targeting the microbiome and smoking-related cardiovascular disease so possible microbial targets for cardiovascular risk reduction can be identified.

Recent progress and perspectives on the relationship between hyperuricemia and periodontitis

Periodontitis is one of the most prevalent diseases in oral cavity, which could not merely lead to the destruction of supporting or surrounding tooth structures but also affect the whole-body health such as the digestive and nervous systems. Epidemiological investigations suggested that in some developed countries, more than 45% or even 50% population were suffering from periodontitis. However, the prevalence increases with age remarkably and it is investigated that a high prevalence (>50%) is affecting the elderly who is over 65 years old. There is an increasing interest in the direct and indirect relationships between periodontitis and hyperuricemia. Currently, hyperuricemia has become the second major metabolic disease in modern society and the prevalence of hyperuricemia among adult males and females was 21.7% and 14.4% respectively. As an inflammatory disease associated with various systemic diseases, periodontitis may have certain connections with hyperuricemia. Partial existing research announced that hyperuricemia could act as an inhibitory factor for periodontitis, while other scholars presented that a high uric acid (UA) level was more likely to aggravate inflammatory immune response and lead to more serious tissue destruction. This article provides a detailed and comprehensive overview of the relationship underlying hyperuricemia and periodontitis in the molecular mechanisms. Given the impact of hyperuricemia, this review could provide insight into its comorbidities.

Measuring changes in blood volume fraction during induced gingivitis of healthy and unhealthy populations using hyperspectral spatial frequency domain imaging: a clinical study

This investigation aimed to quantitatively measure the changes in inflammation of subjects with healthy and unhealthy gums during a period of induced gingivitis. A total of 30 subjects (15 healthy, 15 with gum inflammation) were enlisted and given oral exams by a dental hygienist. Baseline measurements were acquired before a 3-week period of oral hygiene abstinence. The lobene modified gingival index scoring was used for inflammation scoring and hyperspectral spatial frequency domain imaging was used to quantitatively measure oxy- and deoxygenated blood volume fraction at two time points: at Baseline and after 3 weeks of oral hygiene abstinence. We found that abstaining from oral hygiene causes a near proportional increase in oxygenated and deoxygenated blood volume fraction for healthy individuals. For individuals who started the study with mild to moderate gingivitis, increases in blood volume were mainly due to deoxygenated blood.

Oral Microbiota from Periodontitis Promote Oral Squamous Cell Carcinoma Development via γδ T Cell Activation

Oral squamous cell carcinoma (OSCC) is a fatal disease, and periodontitis is associated with OSCC development. However, the pathogenesis in the context of OSCC with periodontitis has not been fully understood. Here, we demonstrated that periodontitis promoted OSCC development, accompanied by alterations in the oral bacterial community and the tumor immune microenvironment. The oral microbiota from periodontitis maintained the dominant position throughout the whole process of OSCC with periodontitis, of which Porphyromonas was the most abundant genus. The oral microbiota from periodontitis could activate interleukin-17-positive (IL-17⁺) γδ T cells directly. The activated γδ T cells were necessary for the IL-17/signal transducer and activator of transcription 3 (STAT3) pathway and promoted M2-tumor-associated macrophage (TAM) infiltration in OSCC proliferation. Our data provide insight into the carcinogenesis of OSCC with periodontitis by outlining the tumor-associated immune response shaped by the oral microbiota from periodontitis. Thus, oral commensal bacteria and IL-17⁺ γδ T cells might be potential targets for monitoring and treating OSCC. IMPORTANCE The work reveals the role of the oral microbiota from periodontitis in carcinogenesis. Furthermore, our study provides insight into the pathogenesis of OSCC with periodontitis by outlining the tumor-associated immune response shaped by the oral microbiota from periodontitis, which might identify new research and intervention targets for OSCC with periodontitis.

Stable reconstructed human gingiva–microbe interaction model: Differential response to commensals and pathogens

Background

To investigate human oral health and disease, models are required which represent the interactions between the oral mucosa and microbiome. Our aim was to develop an organotypic model which maintains viability of both host and microbes for an extended period of time.

Methods

Reconstructed Human Gingiva (RHG) were cultured air-lifted with or without penicillin-streptomycin (PS) and topically exposed to Streptococcus gordonii (commensal) or Aggregatibacter actinomycetemcomitans (pathogen) for 72 hours in agar. RHG histology, viability and cytokines (ELISA), and bacterial viability (colony forming units) and location (FISH) were assessed.

Results

The low concentration of topically applied agar did not influence RHG viability. Topically applied bacteria in agar remained localized and viable for 72 hours and did not spill over to infect RHG culture medium. PS in RHG culture medium killed topically applied bacteria. Co-culture with living bacteria did not influence RHG viability (Ki67 expression, MTT assay) or histology (epithelium differentiation, Keratin10 expression). RHG exposed to S. gordonii (with or without PS) did not influence low level of IL-6, IL-8, CCL2, CCL5, CCL20 or CXCL1 secretion. However, all cytokines increased (except CCL2) when RHG were co-cultured with A. actinomycetemcomitans. The effect was significantly more in the presence of living, rather than dead, A. actinomycetemcomitans. Both bacteria resulted in increased expression of RHG antimicrobial peptides (AMPs) Elafin and HBD-2, with S. gordonii exposure resulting in the most Elafin secretion.

Conclusion

This technical advance enables living human oral host–microbe interactions to be investigated during a 72-hour period and shows differences in innate immunology triggered by S. gordonii and A. actinomycetemcomitans.

Periodontitis-related salivary microbiota aggravates Alzheimer's disease via gut-brain axis crosstalk

The oral cavity is the initial chamber of digestive tract; the saliva swallowed daily contains an estimated 1.5 × 10¹² oral bacteria. Increasing evidence indicates that periodontal pathogens and subsequent inflammatory responses to them contribute to the pathogenesis of Alzheimer's disease (AD). The intestine and central nervous system jointly engage in crosstalk; microbiota-mediated immunity significantly impacts AD via the gut-brain axis. However, the exact mechanism linking periodontitis to AD remains unclear. In this study, we explored the influence of periodontitis-related salivary microbiota on AD based on the gut-brain crosstalk in APP^swe/PS1^ΔE9 (PAP) transgenic mice. Saliva samples were collected from patients with periodontitis and healthy individuals. The salivary microbiota was gavaged into PAP mice for two months. Continuous gavage of periodontitis-related salivary microbiota in PAP mice impaired cognitive function and increased β-amyloid accumulation and neuroinflammation. Moreover, these AD-related pathologies were consistent with gut microbial dysbiosis, intestinal pro-inflammatory responses, intestinal barrier impairment, and subsequent exacerbation of systemic inflammation, suggesting that the periodontitis-related salivary microbiota may aggravate AD pathogenesis through crosstalk of the gut-brain axis. In this study, we demonstrated that periodontitis might participate in the pathogenesis of AD by swallowing salivary microbiota, verifying the role of periodontitis in AD progression and providing a novel perspective on the etiology and intervention strategies of AD.

Integrated analysis of the salivary microbiome and metabolome in chronic and aggressive periodontitis: A pilot study

This pilot study was designed to identify the salivary microbial community and metabolic characteristics in patients with generalized periodontitis. A total of 36 saliva samples were collected from 13 patients with aggressive periodontitis (AgP), 13 patients with chronic periodontitis (ChP), and 10 subjects with periodontal health (PH). The microbiome was evaluated using 16S rRNA gene high-throughput sequencing, and the metabolome was accessed using gas chromatography-mass spectrometry. The correlation between microbiomes and metabolomics was analyzed by Spearman’s correlation method. Our results revealed that the salivary microbial community and metabolite composition differed significantly between patients with periodontitis and healthy controls. Striking differences were found in the composition of salivary metabolites between AgP and ChP. The genera Treponema, Peptococcus, Catonella, Desulfobulbus, Peptostreptococcaceae_[XI] ([G-2], [G-3] [G-4], [G-6], and [G-9]), Bacteroidetes_[G-5], TM7_[G-5], Dialister, Eikenella, Fretibacterium, and Filifactor were present in higher levels in patients with periodontitis than in the healthy participants. The biochemical pathways that were significantly different between ChP and AgP included pyrimidine metabolism; alanine, aspartate, and glutamate metabolism; beta-alanine metabolism; citrate cycle; and arginine and proline metabolism. The differential metabolites between ChP and AgP groups, such as urea, beta-alanine, 3-aminoisobutyric acid, and thymine, showed the most significant correlations with the genera. These differential microorganisms and metabolites may be used as potential biomarkers to monitor the occurrence and development of periodontitis through the utilization of non-invasive and convenient saliva samples. This study reveals the integration of salivary microbial data and metabolomic data, which provides a foundation to further explore the potential mechanism of periodontitis.

Host mRNA Analysis of Periodontal Disease Patients Positive for Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans and Tannerella forsythia

Periodontal disease is a frequent pathology worldwide, with a constantly increasing prevalence. For the optimal management of periodontal disease, there is a need to take advantage of actual technology to understand the bacterial etiology correlated with the pathogenic mechanisms, risk factors and treatment protocols. We analyzed the scientific literature published in the last 5 years regarding the recent applications of mRNA analysis in periodontal disease for the main known bacterial species considered to be the etiological agents: Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans and Tannerella forsythia. We identified new pathogenic mechanisms, therapeutic target genes and possible pathways to prevent periodontal disease. The mRNA analysis, as well as the important technological progress in recent years, supports its implementation in the routine management of periodontal disease patients.

Effect of electronic cigarette and tobacco smoking on the human saliva microbial community

Increasing evidence demonstrated the oral microbial community profile characteristics affected by conventional cigarettes smoking, but few studies focus on oral microbiome in response to electronic cigarettes (E-cigarettes). This study aimed to investigate the effect of E-cigarettes on the oral microbiome and to describe the difference of oral community profiles between E-cigarette smokers and tobacco smokers. 16S rRNA V4 gene sequencing was performed to investigate the oral microbial profiles of 5 E-cigarette smokers, 14 tobacco smokers, 8 quitting tobacco smokers, and 6 nonsmokers. The Chao1, ACE, and Shannon diversity indexes increased significantly in saliva samples collected from E-cigarette smokers and tobacco smokers compared to the non-smokers, and no significant difference was found in alpha diversity between E-cigarette smokers and tobacco smokers. The main phyla Proteobacteria, Firmicutes, Bacteroidetes, and Fusobacteria and major genera Neisseria, Streptococcus, Prevotellaceae, Fusobacterium, and Porphyromonas dominated in the smoking groups, while Actinobacteria, Proteobacteria, Firmicutes, Bacteroidetes, and Fusobacteria became the dominant phyla along with the genera Corynebacterium, Neisseria, Streptococcus, Actinomyces, and Porphyromonas in the nonsmokers. The differences in the phylum Actinobacteria and genus Corynebacterium contributed to various functional differences between smokers and nonsmokers. The difference on oral microbial and composition between E-cigarettes and common tobacco were associated with increased Prevotellaceae and decreased Neisseria. Additionally, smoking cessation could lead to re-establishment of the oral microbiome to that of nonsmokers. Our data demonstrate that E-cigarette smoking had different effects on the structure and composition of the oral microbial community compared to tobacco smoking. However, the short- and long-term impact of E-cigarette smoking on microbiome composition and function needs further exploration.

Citizen-science reveals changes in the oral microbiome in Spain through age and lifestyle factors

The relevance of the human oral microbiome to our understanding of human health has grown in recent years as microbiome studies continue to develop. Given the links of the oral cavity with the digestive, respiratory and circulatory systems, the composition of the oral microbiome is relevant beyond just oral health, impacting systemic processes across the body. However, we still have a very limited understanding about intrinsic and extrinsic factors that shape the composition of the healthy oral microbiome. Here, we followed a citizen-science approach to assess the relative impact on the oral microbiome of selected biological, social, and lifestyle factors in 1648 Spanish individuals. We found that the oral microbiome changes across age, with middle ages showing a more homogeneous composition, and older ages showing more diverse microbiomes with increased representation of typically low abundance taxa. By measuring differences within and between groups of individuals sharing a given parameter, we were able to assess the relative impact of different factors in driving specific microbial compositions. Chronic health disorders present in the analyzed population were the most impactful factors, followed by smoking and the presence of yeasts in the oral cavity. Finally, we corroborate findings in the literature that relatives tend to have more similar oral microbiomes, and show for the first time a similar effect for classmates. Multiple intrinsic and extrinsic factors jointly shape the oral microbiome. Comparative analysis of metabarcoding data from a large sample set allows us to disentangle the individual effects.

Periodontitis Salivary Microbiota Aggravates Ischemic Stroke Through IL-17A

Although epidemiological studies suggest that periodontitis is tightly associated with ischemic stroke, its impact on ischemic stroke and the underlysing mechanisms are poorly understood. Recent studies have shown that alteration in gut microbiota composition influences the outcomes of ischemic stroke. In the state of periodontitis, many oral pathogenic bacteria in the saliva are swallowed and transmitted to the gut. However, the role of periodontitis microbiota in the pathogenesis and progression of ischemic stroke is unclear. Therefore, we hypothesized that the periodontitis salivary microbiota influences the gut immune system and aggravates ischemic stroke. Mice receiving gavage of periodontitis salivary microbiota showed significantly worse stroke outcomes. And these mice also manifested more severe neuroinflammation, with higher infiltration of inflammatory cells and expression of inflammatory cytokines in the ischemic brain. More accumulation of Th17 cells and IL-17⁺ γδ T cells were observed in the ileum. And in Kaede transgenic mice after photoconversion. Migration of CD4⁺ T cells and γδ T cells from the ileum to the brain was observed after ischemic stroke in photoconverted Kaede transgenic mice. Furthermore, the worse stroke outcome was abolished in the IL-17A knockout mice. These findings suggest that periodontitis salivary microbiota increased IL-17A-producing immune cells in the gut, likely promoted the migration of these cells from the gut to the brain, and subsequently provoked neuroinflammation after ischemic stroke. These findings have revealed the role of periodontitis in ischemic stroke through the gut and provided new insights into the worse outcome of ischemic stroke coexisting with periodontitis in clinical trials.

The Composition and Functional Capacities of Saliva Microbiota Differ Between Children With Low and High Sweet Treat Consumption

Excess sugar consumption—common in youth—is associated with poor health. Evidence on the relationship between sugar consumption and the oral microbiome, however, remains scarce and inconclusive. We explored whether the diversity, composition, and functional capacities of saliva microbiota differ based on the consumption of select sugary foods and drinks (“sweet treats”). Using 16S rRNA gene sequencing, we characterized saliva microbiota from 11 to 13-year-old children who participated in the Finnish Health in Teens (Fin-HIT) cohort study. The sample comprised children in the lowest (n = 227) and highest (n = 226) tertiles of sweet treat consumption. We compared differences in the alpha diversity (Shannon, inverse Simpson, and Chao1 indices), beta diversity (principal coordinates analysis based on Bray–Curtis dissimilarity), and abundance (differentially abundant operational taxonomic units (OTUs) at the genus level) between these low and high consumption groups. We performed PICRUSt2 to predict the metabolic pathways of microbial communities. No differences emerged in the alpha diversity between low and high sweet treat consumption, whereas the beta diversity differed between groups (p = 0.001). The abundance of several genera such as Streptococcus, Prevotella, Veillonella, and Selenomonas was higher in the high consumption group compared with the low consumption group following false discovery rate correction (p < 0.05). Children with high sweet treat consumption exhibited higher proportions of nitrate reduction IV and gondoate biosynthesis pathways compared with the low consumption group (p < 0.05). To conclude, sweet treat consumption shapes saliva microbiota. Children who consume a high level of sweet treats exhibited different compositions and metabolic pathways compared with children who consume low levels of sweet treats. Our findings reveal novel insights into the relationship between sugary diets and oral microbiota.

The Microbiome in Periodontitis and Diabetes

Objectives

To perform a comprehensive and integrative review of the available literature on the potential changes in the microbiome of healthy and individuals with diabetes under periodontal health and disease.

Materials and Methods

The review was conducted by two independent reviewers. Indexed electronic databases (PubMed/Medline, Cochrane Library, Web of Science and Scopus) were searched, including articles published in English and dated from 5 years ago until December 2021. A manual search also was performed to identify co-related articles. Following the removal of duplicates and eligibility criteria, the articles were included in tables for analysis and described in the manuscript.

Results

According to this review, diabetes mellitus was associated with significant changes in the subgingival and salivary microbiome, either in its association with periodontitis or in cases of periodontal health. In addition to affecting microbial diversity in terms of taxonomy, metagenomic studies have shown that this endocrine disorder may also be directly related to increased pathogenicity in the oral microbiome.

Conclusion

Although the reviewed studies demonstrate important differences in the subgingival and salivary microbiome composition because of diabetes mellitus, further studies are needed to clarify the real effects of hyperglycemia on oral microbial profiles and support new diagnostic approaches and innovative treatments.

Varied Composition and Underlying Mechanisms of Gut Microbiome in Neuroinflammation

The human gut microbiome has been implicated in a host of bodily functions and their regulation, including brain development and cognition. Neuroinflammation is a relatively newer piece of the puzzle and is implicated in the pathogenesis of many neurological disorders. The microbiome of the gut may alter the inflammatory signaling inside the brain through the secretion of short-chain fatty acids, controlling the availability of amino acid tryptophan and altering vagal activation. Studies in Korea and elsewhere highlight a strong link between microbiome dynamics and neurocognitive states, including personality. For these reasons, re-establishing microbial flora of the gut looks critical for keeping neuroinflammation from putting the whole system aflame through probiotics and allotransplantation of the fecal microbiome. However, the numerosity of the microbiome remains a challenge. For this purpose, it is suggested that wherever possible, a fecal microbial auto-transplant may prove more effective. This review summarizes the current knowledge about the role of the microbiome in neuroinflammation and the various mechanism involved in this process. As an example, we have also discussed the autism spectrum disorder and the implication of neuroinflammation and microbiome in its pathogenesis.

Salivary Microbiota and Host-Inflammatory Responses in Periodontitis Affected Individuals With and Without Rheumatoid Arthritis

Objectives

Periodontitis and rheumatoid arthritis (RA) are two widespread chronic inflammatory diseases with a previously suggested association. The objective of the current study was to compare the oral microbial composition and host´s inflammatory mediator profile of saliva samples obtained from subjects with periodontitis, with and without RA, as well as to predict biomarkers, of bacterial pathogens and/or inflammatory mediators, for classification of samples associated with periodontitis and RA.

Methods

Salivary samples were obtained from 53 patients with periodontitis and RA and 48 non-RA with chronic periodontitis. The microbial composition was identified using 16S rRNA gene sequencing and compared across periodontitis patients with and without RA. Levels of inflammatory mediators were determined using a multiplex bead assay, compared between the groups and correlated to the microbial profile. The achieved data was analysed using PCoA, DESeq2 and two machine learning algorithms, OPLS-DA and sPLS-DA.

Results

Differential abundance DESeq2 analyses showed that the four most highly enriched (log2 FC >20) amplicon sequence variants (ASVs) in the non-RA periodontitis group included Alloprevotella sp., Prevotella sp., Haemophilus sp., and Actinomyces sp. whereas Granulicatella sp., Veillonella sp., Megasphaera sp., and Fusobacterium nucleatum were the most highly enriched ASVs (log2 FC >20) in the RA group. OPLS-DA with log2 FC analyses demonstrated that the top ASVs with the highest importance included Vampirovibrio sp. having a positive correlation with non-RA group, and seven ASVs belonging to Sphingomonas insulae, Sphingobium sp., Novosphingobium aromaticivorans, Delftia acidovorans, Aquabacterium spp. and Sphingomonas echinoides with a positive correlation with RA group. Among the detected inflammatory mediators in saliva samples, TWEAK/TNFSF12, IL-35, IFN-α2, pentraxin-3, gp130/sIL6Rb, sIL-6Ra, IL-19 and sTNF-R1 were found to be significantly increased in patients with periodontitis and RA compared to non-RA group with periodontitis. Moreover, correlations between ASVs and inflammatory mediators using sPLS-DA analysis revealed that TWEAK/TNFSF12, pentraxin-3 and IL-19 were positively correlated with the ASVs Sphingobium sp., Acidovorax delafieldii, Novosphingobium sp., and Aquabacterium sp.

Conclusion

Our results suggest that the combination of microbes and host inflammatory mediators could be more efficient to be used as a predictable biomarker associated with periodontitis and RA, as compared to microbes and inflammatory mediators alone.

Insights into gut microbiota communities of Poecilobdella manillensis, a prevalent Asian medicinal leech

AIMS

Medicinal leeches (Annelida: Hirudinea) are fresh water ectoparasitic species which have been applied as traditional therapy. However, gut microbiota could bring high risks of opportunistic infections after leeching, and arouses great interests. Here gut bacterial and fungal communities of an Asian prevalent leech Poecilobdella manillensis, were characterized and analyzed through culture-independent sequencing.

METHODS AND RESULTS

With high coverage in 18 samples (>0.999), a more complicated community was apparent after comparing with previous leech studies. A total of 779/939 OTUs of bacteria and fungi were detected from leech guts. The bacterial community was dominated by phylum Bacteroidetes and Synergistetes. Genera Mucinivorans and Fretibacterium accounted mostly at the genus level. And genus Aeromonas showed an extremely low abundance (2.02%) on average. The fungal community was dominated by phylum Ascomycota and Basidiomycota. At the genus level, the dominant OTUs included Mortierella, Geminibasidium and Fusarium. The analysis of core taxa included those above dominant genera and some low-abundance genera (>1%). The functional annotation of bacterial community showed a close correlation with metabolism (34.8 ± 0.6%). Some fungal species were predicted as opportunistic human pathogens including Fusarium and Chaetomiaceae.

CONCLUSIONS

The present study provides fundamental rationales for further studies of such issues as bacteria-fungi-host interactions, host fitness, potential pathogens and infecting risks after leeching. It shall facilitate in-depth explorations on a safe utilization of leech therapy.

SIGNIFICANCE AND IMPACT OF STUDY

Present paper is the first-ever exploration on microbiota of a prevalent Asian medicinal leech based on culture-independent technical. And it is also the first report of gut fungi community of medicinal leech. The diversity and composition of bacteria in P. manillensis was far different from that of the European leech. The main components and core OTUs indicate a particular gut environment of medicinal leech. Unknown bacterial and fungal species were also recovered from leech gut.

Gingival Transcriptome of Innate Antimicrobial Factors and the Oral Microbiome With Aging and Periodontitis

The epithelial barrier at mucosal sites comprises an important mechanical protective feature of innate immunity, and is intimately involved in communicating signals of infection/tissue damage to inflammatory and immune cells in these local environments. A wide array of antimicrobial factors (AMF) exist at mucosal sites and in secretions that contribute to this innate immunity. A non-human primate model of ligature-induced periodontitis was used to explore characteristics of the antimicrobial factor transcriptome (n = 114 genes) of gingival biopsies in health, initiation and progression of periodontal lesions, and in samples with clinical resolution. Age effects and relationship of AMF to the dominant members of the oral microbiome were also evaluated. AMF could be stratified into 4 groups with high (n = 22), intermediate (n = 29), low (n = 18) and very low (n = 45) expression in healthy adult tissues. A subset of AMF were altered in healthy young, adolescent and aged samples compared with adults (e.g., APP, CCL28, DEFB113, DEFB126, FLG2, PRH1) and were affected across multiple age groups. With disease, a greater number of the AMF genes were affected in the adult and aged samples with skewing toward decreased expression, for example WDC12, PGLYRP3, FLG2, DEFB128, and DEF4A/B, with multiple age groups. Few of the AMF genes showed a >2-fold increase with disease in any age group. Selected AMF exhibited significant positive correlations across the array of AMF that varied in health and disease. In contrast, a rather limited number of the AMF significantly correlated with members of the microbiome; most prominent in healthy samples. These correlated microbes were different in younger and older samples and differed in health, disease and resolution samples. The findings supported effects of age on the expression of AMF genes in healthy gingival tissues showing a relationship to members of the oral microbiome. Furthermore, a dynamic expression of AMF genes was related to the disease process and showed similarities across the age groups, except for low/very low expressed genes that were unaffected in young samples. Targeted assessment of AMF members from this large array may provide insight into differences in disease risk and biomolecules that provide some discernment of early transition to disease.

Pleckstrin Levels Are Increased in Patients with Chronic Periodontitis and Regulated via the MAP Kinase-p38α Signaling Pathway in Gingival Fibroblasts

Chronic periodontitis (CP) is a bacteria-driven inflammatory disease characterized by the breakdown of gingival tissue, the periodontal ligament, and alveolar bone, leading ultimately to tooth loss. We previously reported the pleckstrin gene (PLEK) to be highly upregulated in gingival tissue of patients with CP and the only gene concurrently upregulated in other inflammatory diseases including rheumatoid arthritis and cardiovascular diseases. Using saliva from 169 individuals diagnosed with CP and healthy controls, we investigated whether pleckstrin could serve as a novel biomarker of periodontitis. Additionally, we explored signal pathways involved in the regulation of PLEK using human gingival fibroblasts (HGFs). Pleckstrin levels were significantly higher (p < 0.001) in the saliva samples of patients with CP compared to controls and closely associated with CP severity. Immunohistochemical analysis revealed the expression of pleckstrin in inflammatory cells and gingival fibroblasts of CP patients. To explore the signal pathways involved in pleckstrin regulation, we stimulated HGFs with either interleukin-1β (IL-1β) or lipopolysaccharides (LPS) alone, or in combination with inhibitors targeting c-Jun N-terminal kinase, tyrosine kinase, protein kinase C, or p38 MAP kinase. Results showed that IL-1β and LPS significantly increased PLEK mRNA and pleckstrin protein levels. VX-745, the p38 MAP kinase inhibitor significantly decreased IL-1β- and LPS-induced pleckstrin levels at both the mRNA and the protein level. Together, these findings show that pleckstrin could serve as a salivary biomarker for the chronic inflammatory disease periodontitis and a regulator of inflammation via the p38 MAP kinase pathway.

Rifaximin-α reduces gut-derived inflammation and mucin degradation in cirrhosis and encephalopathy: RIFSYS randomised controlled trial

BACKGROUND & AIMS

Rifaximin-α is efficacious for the prevention of recurrent hepatic encephalopathy (HE), but its mechanism of action remains unclear. We postulated that rifaximin-α reduces gut microbiota-derived endotoxemia and systemic inflammation, a known driver of HE.

METHODS

In a placebo-controlled, double-blind, mechanistic study, 38 patients with cirrhosis and HE were randomised 1:1 to receive either rifaximin-α (550 mg BID) or placebo for 90 days.

PRIMARY OUTCOME

50% reduction in neutrophil oxidative burst (OB) at 30 days.

SECONDARY OUTCOMES

changes in psychometric hepatic encephalopathy score (PHES) and neurocognitive functioning, shotgun metagenomic sequencing of saliva and faeces, plasma and faecal metabolic profiling, whole blood bacterial DNA quantification, neutrophil toll-like receptor (TLR)-2/4/9 expression and plasma/faecal cytokine analysis.

RESULTS

Patients were well-matched: median MELD (11 rifaximin-α vs. 10 placebo). Rifaximin-α did not lead to a 50% reduction in spontaneous neutrophil OB at 30 days compared to baseline (p = 0.48). However, HE grade normalised (p = 0.014) and PHES improved (p = 0.009) after 30 days on rifaximin-α. Rifaximin-α reduced circulating neutrophil TLR-4 expression on day 30 (p = 0.021) and plasma tumour necrosis factor-α (TNF-α) (p <0.001). Rifaximin-α suppressed oralisation of the gut, reducing levels of mucin-degrading sialidase-rich species, Streptococcus spp, Veillonella atypica and parvula, Akkermansia and Hungatella. Rifaximin-α promoted a TNF-α- and interleukin-17E-enriched intestinal microenvironment, augmenting antibacterial responses to invading pathobionts and promoting gut barrier repair. Those on rifaximin-α were less likely to develop infection (odds ratio 0.21; 95% CI 0.05-0.96).

CONCLUSION

Rifaximin-α led to resolution of overt and covert HE, reduced the likelihood of infection, reduced oralisation of the gut and attenuated systemic inflammation. Rifaximin-α plays a role in gut barrier repair, which could be the mechanism by which it ameliorates bacterial translocation and systemic endotoxemia in cirrhosis.

CLINICAL TRIAL NUMBER

ClinicalTrials.gov NCT02019784.

LAY SUMMARY

In this clinical trial, we examined the underlying mechanism of action of an antibiotic called rifaximin-α which has been shown to be an effective treatment for a complication of chronic liver disease which effects the brain (termed encephalopathy). We show that rifaximin-α suppresses gut bacteria that translocate from the mouth to the intestine and cause the intestinal wall to become leaky by breaking down the protective mucus barrier. This suppression resolves encephalopathy and reduces inflammation in the blood, preventing the development of infection.

Oral Dysbiosis in Severe Forms of Periodontitis Is Associated With Gut Dysbiosis and Correlated With Salivary Inflammatory Mediators: A Preliminary Study

Inflammation is a driven force in modulating microbial communities, but little is known about the interplay between colonizing microorganisms and the immune response in periodontitis. Since local and systemic inflammation may play a whole role in disease, we aimed to evaluate the oral and fecal microbiome of patients with periodontitis and to correlate the oral microbiome data with levels of inflammatory mediator in saliva. Methods: Nine patients with periodontitis (P) in Stage 3/Grade B and nine age-matched non-affected controls (H) were evaluated. Microbial communities of oral biofilms (the supra and subgingival from affected and non-affected sites) and feces were determined by sequencing analysis of the 16SrRNA V3-V4 region. Salivary levels of 40 chemokines and cytokines were correlated with oral microbiome data. Results: Supragingival microbial communities of P differed from H (Pielou's evenness index, and Beta diversity, and weighted UniFrac), since relative abundance (RA) of Defluviitaleaceae, Desulfobulbaceae, Mycoplasmataceae, Peptostreococcales-Tissierellales, and Campylobacteraceae was higher in P, whereas Muribaculaceae and Streptococcaceae were more abundant in H. Subgingival non-affected sites of P did not differ from H, except for a lower abundance of Gemellaceae. The microbiome of affected periodontitis sites (PD ≥ 4 mm) clustered apart from the subgingival sites of H. Oral pathobionts was more abundant in sub and supragingival biofilms of P than H. Fecal samples of P were enriched with Acidaminococcus, Clostridium, Lactobacillus, Bifidobacterium, Megasphaera, and Romboutsia when compared to H. The salivary levels of interleukin 6 (IL-6) and inflammatory chemokines were positively correlated with the RA of several recognized and putative pathobionts, whereas the RA of beneficial species, such as Rothia aeria and Haemophilus parainfluenzae was negatively correlated with the levels of Chemokine C-C motif Ligand 2 (CCL2), which is considered protective. Dysbiosis in patients with periodontitis was not restricted to periodontal pockets but was also seen in the supragingival and subgingival non-affected sites and feces. Subgingival dysbiosis revealed microbial signatures characteristic of different immune profiles, suggesting a role for candidate pathogens and beneficial organisms in the inflammatory process of periodontitis.

Effect of Lactobacillus reuteri on Gingival Inflammation and Composition of the Oral Microbiota in Patients Undergoing Treatment with Fixed Orthodontic Appliances: Study Protocol of a Randomized Control Trial

The effect of probiotics in improving or maintaining oral health in orthodontic patients is understudied. The aim of this study is to evaluate the effect of probiotic administration in addition to tooth brushing on clinical gingival inflammation, plaque formation, subgingival microbiota composition, and salivary biomarkers of inflammation in adolescents with fixed orthodontic appliances. The present study is a 6-month, double-blind, two-arm, placebo-controlled, single-center trial, in which 116 adolescent volunteers aged 12-16 years will be recruited from the patients of the orthodontics clinic of the University Hospital of Lille, France. Subjects who meet the eligibility criteria will be allocated to one of the following groups: (i) control: two placebo lozenges per day for 90 days together with regular oral hygiene, (ii) test: two probiotic lozenges per day for 90 days together with regular oral hygiene. Clinical assessment and biological sample collection will be performed at baseline, 3 and 6 months. In addition, compliance outcomes and adverse events will be monitored.

Oral microbiota and periodontitis severity among Hispanic adults

Background

Periodontitis, one of the most common bacterial infections characterized by chronic inflammation, is also known to be a risk factor for chronic conditions, including cardiovascular disease and cancer. This inflammation is driven by an altered microbiota with an increase in pathogenic bacteria. We evaluated the association between oral microbiota and periodontitis severity in high-risk Hispanics.

Method

This cross-sectional study recruited 134 sexually active participants aged 21 to 49 years old from STI Clinics in Puerto Rico. A periodontal examination, saliva collection, and an interviewer-administered questionnaire were performed. Periodontal severity was categorized as: having no disease, mild, and moderate/severe and BOP and tooth loos was noted. Saliva samples were collected for genomic DNA extraction, downstream 16S rDNA amplification sequencing, and bioinformatics analyses.

Results

The structure, composition, and diversity of bacterial communities differed significantly according to periodontal severity. The richness and overall diversity also differed between participants without periodontitis and participants with some level of periodontal disease. A higher abundance of Prevotella, Veillonella, or Treponema was attributed to periodontal disease and Aggregatibacter to severe bleeding on probing, while Neisseria was found in higher abundance in healthy participants, decreasing its levels with drinking, smoking, and oral sex practices.

Conclusions

Our findings indicate that dysbiosis occurs as periodontal disease progresses, and both alcohol consumption and smoking habits pose risk factors for oral dysbiosis. These results are of public health and clinical impact, as several bacteria identified could serve in the future as biomarkers for periodontitis and oral cancer risk.

Saliva as a non-invasive specimen for COPD assessment

BACKGROUND

People with COPD have been reported to bear a distinct airway microbiota from healthy individuals based on bronchoalveolar lavage (BAL) and sputum samples. Unfortunately, the collection of these samples involves relatively invasive procedures and is resource-demanding, limiting its regular use. Non-invasive samples from the upper airways could constitute an interesting alternative, but its relationship with COPD is still underexplored. We examined the merits of saliva to identify the typical profile of COPD oral bacteria and test its association with the disease.

METHODS

Outpatients with COPD and age-sex matched healthy controls were recruited and characterised based on clinical parameters and 16S rRNA profiling of oral bacteria. A clustering analysis based on patients' oral bacteria beta-diversity and logistic regressions were performed to evaluate the association between oral bacteria composition and COPD.

RESULTS

128 individuals participated (70 patients and 58 controls). Differential abundance analyses showed differences in patients comparable to the ones previously observed in samples from the lower respiratory tract, i.e., an increase in Proteobacteria (particularly Haemophilus) and loss of microbiota diversity. An unsupervised clustering analysis separated patients in two groups based on microbiota composition differing significantly in the frequency of patients hospitalized due to severe acute exacerbation of COPD (AECOPD) and in the frequency of GOLD D patients. Furthermore, a low frequency of Prevotella was associated with a significantly higher risk of recent severe AECOPD and of being GOLD D.

CONCLUSION

Salivary bacteria showed an association with COPD, particularly with severe exacerbations, supporting the use of this non-invasive specimen for future studies of heterogeneous respiratory diseases like COPD.

Analysis of Salivary Microbiome and Its Association With Periodontitis in Patients With Obstructive Sleep Apnea

Objectives

This study aimed to analyze the periodontal conditions of patients with obstructive sleep apnea (OSA) in relation to the salivary microbiome.

Materials and Methods

In total, 54 male adults (27 with OSA, 27 controls) completed this cross-sectional study. All participants were monitored by overnight polysomnography (PSG) and underwent full-mouth periodontal examination. Saliva samples were then collected, and the microbial 16S ribosomal RNA gene was sequenced. The data were analyzed to determine the microbial distribution and the community structure of the two groups.

Results

Demonstrated by alpha and beta diversity, the OSA group had a lower microbial richness and a lower observed species than the controls. There was no significant difference in the microbial species diversity or evenness between the OSA and the non-OSA groups. The OSA group had fewer operational taxonomic units (OTUs), and the distribution of microbiome showed that several gram-positive bacteria had higher abundance in the OSA group. As for periodontal pathogens, the relative abundance of Prevotella was significantly increased in the OSA group. No significant difference was observed in the relative abundance of other pathogens at either the genus or species level.

Conclusions

The salivary microbial community structure was altered in patients with OSA in terms of species richness and trans-habitat diversity, along with an increase in Prevotella, a specific periodontal pathogen. These findings might explain the high prevalence of periodontitis in OSA patients.

Metagenomic analysis of primary colorectal carcinomas and their metastases identifies potential microbial risk factors

The paucity of microbiome studies at intestinal tissues has contributed to a yet limited understanding of potential viral and bacterial cofactors of colorectal cancer (CRC) carcinogenesis or progression. We analysed whole-genome sequences of CRC primary tumours, their corresponding metastases and matched normal tissue for sequences of viral, phage and bacterial species. Bacteriome analysis showed Fusobacterium nucleatum, Streptococcus sanguinis, F. Hwasookii, Anaerococcus mediterraneensis and further species enriched in primary CRCs. The primary CRC of one patient was enriched for F. alocis, S. anginosus, Parvimonas micra and Gemella sp. 948. Enrichment of Escherichia coli strains IAI1, SE11, K-12 and M8 was observed in metastases together with coliphages enterobacteria phage φ80 and Escherichia phage VT2φ_272. Virome analysis showed that phages were the most preponderant viral species (46%), the main families being Myoviridae, Siphoviridae and Podoviridae. Primary CRCs were enriched for bacteriophages, showing five phages (Enterobacteria, Bacillus, Proteus, Streptococcus phages) together with their pathogenic hosts in contrast to normal tissues. The most frequently detected, and Blast-confirmed, viruses included human endogenous retrovirus K113, human herpesviruses 7 and 6B, Megavirus chilensis, cytomegalovirus (CMV) and Epstein-Barr virus (EBV), with one patient showing EBV enrichment in primary tumour and metastases. EBV was PCR-validated in 80 pairs of CRC primary tumour and their corresponding normal tissues; in 21 of these pairs (26.3%), it was detectable in primary tumours only. The number of viral species was increased and bacterial species decreased in CRCs compared with normal tissues, and we could discriminate primary CRCs from metastases and normal tissues by applying the Hutcheson t-test on the Shannon indices based on viral and bacterial species. Taken together, our results descriptively support hypotheses on microorganisms as potential (co)risk factors of CRC and extend putative suggestions on critical microbiome species in CRC metastasis.