The human oral microbiome. J Bacteriol. 2010;192:5002-5017. [PMID: 20656903 DOI: 10.1128/jb.00542-10]

Genome-wide association study identifies host genetic variants influencing oral microbiota diversity and metabolic health

The microbial communities of the oral cavity are important elements of oral and systemic health. With emerging evidence highlighting the heritability of oral bacterial microbiota, this study aimed to identify host genome variants that influence oral microbial traits. Using data from 16S rRNA gene amplicon sequencing, we performed genome-wide association studies with univariate and multivariate traits of the salivary microbiota from 610 unrelated adults from the Danish ADDITION-PRO cohort. We identified six single nucleotide polymorphisms (SNPs) in human genomes that showed associations with abundance of bacterial taxa at different taxonomical tiers (P < 5 × 10-8). Notably, SNP rs17793860 surpassed our study-wide significance threshold (P < 1.19 × 10-9). Additionally, rs4530093 was linked to bacterial beta diversity (P < 5 × 10-8). Out of these seven SNPs identified, six exerted effects on metabolic traits, including glycated hemoglobin A1c, triglyceride and high-density lipoprotein cholesterol levels, the risk of type 2 diabetes and stroke. Our findings highlight the impact of specific host SNPs on the composition and diversity of the oral bacterial community. Importantly, our results indicate an intricate interplay between host genetics, the oral microbiota, and metabolic health. We emphasize the need for integrative approaches considering genetic, microbial, and metabolic factors.

Chlorhexidine digluconate mouthwash alters the oral microbial composition and affects the prevalence of antimicrobial resistance genes

Introduction

Chlorhexidine (CHX) is a commonly used antiseptic in situations of limited oral hygiene ability such as after periodontal surgery. However, CHX is also considered as a possible factor in the emergence of cross-resistance to antibiotics. The aim of this study was to analyze the changes in the oral microbiota and the prevalence of antimicrobial resistance genes (ARGs) due to CHX treatment.

Materials and methods

We analyzed the oral metagenome of 20 patients who applied a 0.2% CHX mouthwash twice daily for 4 weeks following periodontal surgical procedures. Saliva and supragingival plaque samples were examined before, directly after 4 weeks, and another 4 weeks after discontinuing the CHX treatment.

Results

Alpha-diversity decreased significantly with CHX use. The Bray-Curtis dissimilarity increased in both sample sites and mainly streptococci showed a higher relative abundance after CHX treatment. Although no significant changes of ARGs could be detected, an increase in prevalence was found for genes that encode for tetracycline efflux pumps.

Conclusion

CHX treatment appears to promote a caries-associated bacterial community and the emergence of tetracycline resistance genes. Future research should focus on CHX-related changes in the microbial community and whether the discovered tetracycline resistance genes promote resistance to CHX.

Supra- and Subgingival Microbiome in Gingivitis and Impact of Biofilm Control: A Comprehensive Review

This comprehensive review aimed (1) to characterize the sub- and supragingival microbiome in patients with biofilm-induced gingivitis (including experimental gingivitis), (2) to assess its stability and evolution over time, and (3) to assess the impact of biofilm control measures on this stability. An electronic search of the MEDLINE®/PubMed® database until December 2023 was conducted. NCBI Taxonomy, eHOMD 16S rRNA Reference Sequence, and Tree Version 15.23 databases were used to standardize taxonomic nomenclature. Out of 89 papers initially retrieved, 14 studies were finally included: 11 using experimental gingivitis as a model and three randomized clinical trials evaluating the impact of biofilm control measures. Among them, five characterized the subgingival microbiome, nine the supragingival microbiome, and one both the sub- and supragingival microbiome. In addition, five studies evaluated the effect of toothpaste, and four studies evaluated the effect of mouth rinses. The diversity and structure of the microbiome differed significantly between patients with periodontal health and those with biofilm-induced gingivitis (including experimental gingivitis). Those differences were not reversed through conventional oral hygiene measures. Specific antiseptic agents, especially if delivered as mouth rinses, may have an impact on the supra- and subgingival microbiome in gingivitis.

Saliva assay: a call for methodological standardization

The oral cavity provides an ideal environment for microorganisms, including bacteria, viruses, and fungi, to flourish. Increasing attention has been focused on the connection between the oral microbiome and both oral and systemic diseases, spurring active research into the collection and analysis of specimens for healthcare purposes. Among the various methods for analyzing the oral microbiome, saliva analysis is especially prominent. Saliva samples, which can be collected non-invasively, provide information on the systemic health and oral microbiome composition of an individual. This review was performed to evaluate the current state of the relevant research through an examination of the literature and to suggest an appropriate assay method for investigating the oral microbiome. We analyzed articles published in English in SCI(E) journals after January 1, 2000, ultimately selecting 53 articles for review. Articles were identified through keyword searches in the PubMed, Embase, Cochrane, Web of Science, and CINAHL databases. Three experienced researchers conducted full-text assessments following title and abstract screening to select appropriate papers. Subsequently, they organized and analyzed the desired data. Our review revealed that most studies utilized unstimulated saliva samples for oral microbiome analysis. Of the 53 studies examined, 29 identified relationships between the oral microbiome and various diseases, such as oral disease, Behçet disease, cancer, and oral lichen planus. However, the studies employed diverse methods of collection and analysis, which compromised the reliability and accuracy of the findings. To address the limitations caused by methodological inconsistencies, a standardized saliva assay should be established.

Metagenomic Characterization and Comparative Analysis of Removable Denture-Wearing and Non-Denture-Wearing Individuals in Healthy and Diseased Periodontal Conditions

Removable denture wearers are at an increased risk of developing periodontal diseases due to biofilm deposition and microbial colonization on the denture surface. This study aimed to characterize and compare the metagenomic composition of saliva in denture wearers with different periodontal statuses. Twenty-four community-dwelling elders were recruited and grouped into denture wearers with active periodontitis (APD), non-denture wearers with active periodontitis (APXD), denture wearers with stable periodontal health conditions (SPCD), and non-denture wearers with stable periodontal health conditions (SPCXD). Saliva samples were collected and underwent Type IIB restriction-site-associated DNA for microbiome (2bRAD-M) metagenomic sequencing to characterize the species-resolved microbial composition. Alpha diversity analysis based on the Shannon index revealed no significant difference between groups. Beta diversity analysis using the Jaccard distance matrix was nearly significantly different between denture-wearing and non-denture-wearing groups (p = 0.075). Some respiratory pathogens, including Streptococcus agalactiae and Streptococcus pneumoniae, were detected as the top 30 species in saliva samples. Additionally, LEfSe analysis revealed a substantial presence of pathogenic bacteria in denture groups. In the cohort of saliva samples collected from community-dwelling elders, a remarkable abundance of certain opportunistic pathogens was detected in the microbial community.

Altered salivary microbiota associated with high-sugar beverage consumption

The human oral microbiome may alter oral and systemic disease risk. Consuming high sugar content beverages (HSB) can lead to caries development by altering the microbial composition in dental plaque, but little is known regarding HSB-specific oral microbial alterations. Therefore, we conducted a large, population-based study to examine associations of HSB intake with oral microbiome diversity and composition. Using mouthwash samples of 989 individuals in two nationwide U.S. cohorts, bacterial 16S rRNA genes were amplified, sequenced, and assigned to bacterial taxa. HSB intake was quantified from food frequency questionnaires as low (< 1 serving/week), medium (1-3 servings/week), or high (> 3 servings/week). We assessed overall bacterial diversity and presence of specific taxa with respect to HSB intake in each cohort separately and combined in a meta-analysis. Consistently in the two cohorts, we found lower species richness in high HSB consumers (> 3 cans/week) (p = 0.027), and that overall bacterial community profiles differed from those of non-consumers (PERMANOVA p = 0.040). Specifically, presence of a network of commensal bacteria (Lachnospiraceae, Peptostreptococcaceae, and Alloprevotella rava) was less common in high compared to non-consumers, as were other species including Campylobacter showae, Prevotella oulorum, and Mycoplasma faucium. Presence of acidogenic bacteria Bifodobacteriaceae and Lactobacillus rhamnosus was more common in high consumers. Abundance of Fusobacteriales and its genus Leptotrichia, Lachnoanaerobaculum sp., and Campylobacter were lower with higher HSB consumption, and their abundances were correlated. No significant interaction was found for these associations with diabetic status or with microbial markers for caries (S. mutans) and periodontitis (P. gingivalis). Our results suggest that soft drink intake may alter the salivary microbiota, with consistent results across two independent cohorts. The observed perturbations of overrepresented acidogenic bacteria and underrepresented commensal bacteria in high HSB consumers may have implications for oral and systemic disease risk.

Characterization and morphological methods for oral biofilm visualization: where are we nowadays?

The oral microbiome represents an essential component of the oral ecosystem whose symbiotic relationship contributes to health maintenance. The biofilm represents a state of living of microorganisms surrounding themselves with a complex and tridimensional organized polymeric support and defense matrix. The substrates where the oral biofilm adhere can suffer from damages due to the microbial community metabolisms. Therefore, microbial biofilm represents the main etiological factor of the two pathologies of dental interest with the highest incidence, such as carious pathology and periodontal pathology. The study, analysis, and understanding of the characteristics of the biofilm, starting from the macroscopic structure up to the microscopic architecture, appear essential. This review examined the morphological methods used through the years to identify species, adhesion mechanisms that contribute to biofilm formation and stability, and how the action of microbicidal molecules is effective against pathological biofilm. Microscopy is the primary technique for the morphological characterization of biofilm. Light microscopy, which includes the stereomicroscope and confocal laser microscopy (CLSM), allows the visualization of microbial communities in their natural state, providing valuable information on the spatial arrangement of different microorganisms within the biofilm and revealing microbial diversity in the biofilm matrix. The stereomicroscope provides a three-dimensional view of the sample, allowing detailed observation of the structure, thickness, morphology, and distribution of the various species in the biofilm while CLSM provides information on its three-dimensional architecture, microbial composition, and dynamic development. Electron microscopy, scanning (SEM) or transmission (TEM), allows the high-resolution investigation of the architecture of the biofilm, analyzing the bacterial population, the extracellular polymeric matrix (EPS), and the mechanisms of the physical and chemical forces that contribute to the adhesion of the biofilm to the substrates, on a nanometric scale. More advanced microscopic methodologies, such as scanning transmission electron microscopy (STEM), high-resolution transmission electron microscopy (HR-TEM), and correlative microscopy, have enabled the evaluation of antibacterial treatments, due to the potential to reveal the efficacy of different molecules in breaking down the biofilm. In conclusion, evidence based on scientific literature shows that established microscopic methods represent the most common tools used to characterize biofilm and its morphology in oral microbiology. Further protocols and studies on the application of advanced microscopic techniques are needed to obtain precise details on the microbiological and pathological aspects of oral biofilm.

Microbiota of Saliva: A Non-invasive Diagnostic Tool

Potential of salivary microbiota as a non-invasive diagnostic tool for various diseases are explained in the present review. Traditional diagnostic methods rely on blood, which has limitations in terms of collection and biomarker specificity. We discuss the concept of normal flora and how disruptions in oral microbiota can be indicative of diseases. Saliva, harboring a diverse microbial community, offers promise as a diagnostic biomarker source for oral and non-oral conditions. We delve into the role of microbial dysbiosis in disease pathogenesis and the prospects of using biological indicators like dysbiosis for diagnosis, prediction, and monitoring. This review also emphasizes the significance of saliva microbiota in advancing early disease detection and timely intervention. We addressed the following research question and objectives: Can the microbiota of saliva serve as a non-invasive diagnostic tool for the early detection and monitoring of both oral and non-oral diseases? To achieve this, we will explore the normal flora of microorganisms in the oral cavity, the impact of microbial dysbiosis, and the potential of using specific pathogenic microorganisms as biomarkers. Additionally, we will investigate the correlation between oral and non-oral diseases by analyzing total saliva or site-specific dental biofilms for signs of symbiosis or dysbiosis. This research seeks to contribute valuable insights into the development of a non-invasive diagnostic approach with broad applications in healthcare.

Evaluation of Dental Plaque Area with Artificial Intelligence Model

OBJECTIVES

This study aims to assess the diagnostic accuracy of an artificial intelligence (AI) system employing deep learning for identifying dental plaque, utilizing a dataset comprising photographs of permanent teeth.

MATERIALS AND METHODS

In this study, photographs of 168 teeth belonging to 20 patients aged between 10 and 15 years, who met our criteria, were included. Intraoral photographs were taken of the patients in two stages, before and after the application of the plaque staining agent. To train the AI system to identify plaque on teeth with dental plaque that is not discolored, plaque and teeth were marked on photos with exposed dental plaque. One hundred forty teeth were used to construct the training group, while 28 teeth were used to create the test group. Another dentist reviewed images of teeth with dental plaque that was not discolored, and the effectiveness of AI in detecting plaque was evaluated using pertinent performance indicators. To compare the AI model and the dentist's evaluation outcomes, the mean intersection over union (IoU) values were evaluated by the Wilcoxon test.

RESULTS

The AI system showed higher performance in our study with a precision of 82% accuracy, 84% sensitivity, 83% F1 score, 87% accuracy, and 89% specificity in plaque detection. The area under the curve (AUC) value was found to be 0.922, and the IoU value was 76%. Subsequently, the dentist's plaque diagnosis performance was also evaluated. The IoU value was 0.71, and the AUC was 0.833. The AI model showed statistically significantly higher performance than the dentist (P < 0.05).

CONCLUSIONS

The AI algorithm that we developed has achieved promising results and demonstrated clinically acceptable performance in detecting dental plaque compared to a dentist.

Mycobacterium tuberculosis : a new hitchhiker in the etiopathogenesis of periodontitis

Periodontitis, a chronic inflammatory disease of the gums affects both the ligament and alveolar bone. A severe form of periodontal disease affects a strikingly high number of one billion adults globally. The disease permutes both the soft and hard tissues of the oral cavity leading to localized and systemic diseases. Periodontitis has a deleterious impact on systemic health causing diabetes, cardiovascular diseases (CVD), and other disease. The cause of the enhanced inflammatory process is due to dysbiosis and an unregulated immune response. Innate immune response and T cells trigger uninhibited cytokine release causing an unwarranted inflammatory response. The RANK- RANKL interaction between osteoblasts, immune cells, and progenitor osteoclasts results in the maturation of osteoclasts, which promote bone resorption. It is well established that dysbiosis of the oral cavity has been implicated in periodontitis. But emerging reports suggest that the pulmonary pathogen, Mycobacterium tuberculosis (Mtb), causes extrapulmonary diseases such as periodontitis. Many clinical case reports advocate the involvement of Mtb in periodontitis, which poses a threat with the surge of tuberculosis in HIV and other immunocompromised individuals. Fostering a better understanding of the mechanism, causative agents and control on inflammatory response is imperative in the prevention and treatment of periodontitis.

Bacterial Colonization on Endoscopic Materials and Surgical Field Without Infections After Transoral Endoscopic Thyroidectomy

INTRODUCTION

Our aim was to determine whether bacteria contamination occurred within the surgical field or on endoscopic equipment during surgery using the transoral endoscopic thyroidectomy vestibular approach (TOETVA).

MATERIALS AND METHODS

Participants were recruited from patients planned for TOETVA between May 2017 and December 2019. Bacterial samples were taken before and at the conclusion of the TOETVA procedure. The preoperative and postoperative samples were taken from the endoscopic materials and inferior oral vestibulum using a sterile flocked swab.

RESULTS

The study resulted in 480 samples (80 TOETVAs). No vestibular, port site, or neck infections occurred in any of the patients. Three (3.7%) out of 80 patients developed postoperative fever. Our results show different microbial communities during TOETVA. The most prevalent species detected were S treptococcus species. Multivariate logistic regression analyses revealed that the degree of contamination depended on the sampling site (inferior vestibulum > equipment) ( P =0.03). In addition, the abundance of bacteria was affected by operative time ( P =0.013). There were no significant differences observed in isolation frequencies of bacteria in malignancy ( P =0.34).

CONCLUSIONS

TOETVA surgery is categorized as a "clean-contaminated" operation. A swab identified the common colonizers of oral microbiota on the endoscopic equipment and within the surgical field.

Microbial diagnostics in periodontal diseases

Microbial analytical methods have been instrumental in elucidating the complex microbial etiology of periodontal diseases, by shaping our understanding of subgingival community dynamics. Certain pathobionts can orchestrate the establishment of dysbiotic communities that can subvert the host immune system, triggering inflammation and tissue destruction. Yet, diagnosis and management of periodontal conditions still rely on clinical and radiographic examinations, overlooking the well-established microbial etiology. This review summarizes the chronological emergence of periodontal etiological models and the co-evolution with technological advances in microbial detection. We additionally review the microbial analytical approaches currently accessible to clinicians, highlighting their value in broadening the periodontal assessment. The epidemiological importance of obtaining culture-based antimicrobial susceptibility profiles of periodontal taxa for antibiotic resistance surveillance is also underscored, together with clinically relevant analytical approaches to guide antibiotherapy choices, when necessary. Furthermore, the importance of 16S-based community and shotgun metagenomic profiling is discussed in outlining dysbiotic microbial signatures. Because dysbiosis precedes periodontal damage, biomarker identification offers early diagnostic possibilities to forestall disease relapses during maintenance. Altogether, this review highlights the underutilized potential of clinical microbiology in periodontology, spotlighting the clinical areas most conductive to its diagnostic implementation for enhancing prevention, treatment predictability, and addressing global antibiotic resistance.

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

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

Microbial Communities and Functional Genes in Periodontitis and Healthy Controls

BACKGROUND

Periodontitis is a chronic progressive disease and the leading cause of tooth loss in adults. Recent studies have shown the impact of oral microbial communities on systemic health and diseases such as cancer, atherosclerosis, rheumatoid arthritis, inflammatory bowel disease, diabetes, hypertension, and Alzheimer's disease. In previous case control studies investigatin the relationship between periodontal disease and the oral microbiota, little attention has been paid to the intersections of these domains.

METHODS

Here, we used high-throughput 16S rRNA sequencing to analyse the differences in the microbial composition in saliva between a group of patients with chronic periodontitis (C; n = 51) and a healthy control group (H; n = 61) and predicted the functional gene composition by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States.

RESULTS

We found significant alterations in oral microbial diversity between C and H (P = 0.002). Sixteen genera were significantly different between C and H, and 15 of them were enriched in C linear discriminant analysis (LDA > 2). Fifty functional genes were significantly different between C and H, and 34 of them were enriched in C (P < .025).

CONCLUSIONS

Periodontitis is associated with significant changes in the oral microbial community.

The investigation of the role of oral-originated Prevotella-induced inflammation in childhood asthma

Background and objectives

The oral and gut microbiota play significant roles in childhood asthma pathogenesis. However, the communication dynamics and pathogenic mechanisms by which oral microbiota influence gut microbiota and disease development remain incompletely understood. This study investigated potential mechanisms by which oral-originated gut microbiota, specifically Prevotella genus, may contribute to childhood asthma etiology.

Methods

Oral swab and fecal samples from 30 asthmatic children and 30 healthy controls were collected. Microbiome composition was characterized using 16S rRNA gene sequencing and metagenomics. Genetic distances identified potential oral-originated bacteria in asthmatic children. Functional validation assessed pro-inflammatory properties of in silico predicted microbial mimicry peptides from enriched asthma-associated species. Fecal metabolome profiling combined with metagenomic correlations explored links between gut microbiota and metabolism. HBE cells treated with Prevotella bivia culture supernatant were analyzed for lipid pathway impacts using UPLC-MS/MS.

Results

Children with asthma exhibited distinct oral and gut microbiota structures. Prevotella bivia, P. disiens, P. oris and Bacteroides fragilis were enriched orally and intestinally in asthmatics, while Streptococcus thermophilus decreased. P. bivia, P. disiens and P. oris in asthmatic gut likely originated orally. Microbial peptides induced inflammatory cytokines from immune cells. Aberrant lipid pathways characterized asthmatic children. P. bivia increased pro-inflammatory and decreased anti-inflammatory lipid metabolites in HBE cells.

Conclusion

This study provides evidence of Prevotella transfer from oral to gut microbiota in childhood asthma. Prevotella's microbial mimicry peptides and effects on lipid metabolism contribute to disease pathogenesis by eliciting immune responses. Findings offer mechanistic insights into oral-gut connections in childhood asthma etiology.

Does "all disease begin in the gut"? The gut-organ cross talk in the microbiome

The human microbiome, a diverse ecosystem of microorganisms within the body, plays pivotal roles in health and disease. This review explores site-specific microbiomes, their role in maintaining health, and strategies for their upkeep, focusing on oral, lung, vaginal, skin, and gut microbiota, and their systemic connections. Understanding the intricate relationships between these microbial communities is crucial for unraveling mechanisms underlying human health. Recent research highlights bidirectional communication between the gut and distant microbiome sites, influencing immune function, metabolism, and disease susceptibility. Alterations in one microbiome can impact others, emphasizing their interconnectedness and collective influence on human physiology. The therapeutic potential of gut microbiota in modulating distant microbiomes offers promising avenues for interventions targeting various disorders. Through interdisciplinary collaboration and technological advancements, we can harness the power of the microbiome to revolutionize healthcare, emphasizing microbiome-centric approaches to promote holistic well-being while identifying areas for future research.

Quantitative analysis of the effects of essential oil mouthrinses on clinical plaque microbiome: a parallel-group, randomized trial

BACKGROUND

The rich diversity of microorganisms in the oral cavity plays an important role in the maintenance of oral health and development of detrimental oral health conditions. Beyond commonly used qualitative microbiome metrics, such as relative proportions or diversity, both the species-level identification and quantification of bacteria are key to understanding clinical disease associations. This study reports the first-time application of an absolute quantitative microbiome analysis using spiked DNA standards and shotgun metagenome sequencing to assess the efficacy and safety of product intervention on dental plaque microbiome.

METHODS

In this parallel-group, randomized clinical trial, essential oil mouthrinses, including LISTERINE® Cool Mint Antiseptic (LCM), an alcohol-containing prototype mouthrinse (ACPM), and an alcohol-free prototype mouthrinse (AFPM), were compared against a hydroalcohol control rinse on clinical parameters and the oral microbiome of subjects with moderate gingivitis. To enable a sensitive and clinically meaningful measure of bacterial abundances, species were categorized according to their associations with oral conditions based on published literature and quantified using known amounts of spiked DNA standards.

RESULTS

Multivariate analysis showed that both LCM and ACPM shifted the dysbiotic microbiome composition of subjects with gingivitis to a healthier state after 4 weeks of twice-daily use, resembling the composition of subjects with clinically healthy oral conditions recruited for observational reference comparison at baseline. The essential oil-containing mouthrinses evaluated in this study showed statistically significant reductions in clinical gingivitis and plaque measurements when compared to the hydroalcohol control rinse after 6 weeks of use.

CONCLUSIONS

By establishing a novel quantitative method for microbiome analysis, this study sheds light on the mechanisms of LCM mouthrinse efficacy on oral microbial ecology, demonstrating that repeated usage non-selectively resets a gingivitis-like oral microbiome toward that of a healthy oral cavity.

TRIAL REGISTRATION

The trial was registered on ClinicalTrials.gov on 10/06/2021. The registration number is NCT04921371.

Comparative analysis of oropharyngeal microbiota in healthcare workers post-COVID-19

Background

To date, more than 770 million individuals have become coronavirus disease 2019 (COVID-19) convalescents worldwide. Emerging evidence highlights the influence of COVID-19 on the oral microbiome during both acute and convalescent disease phases. Front-line healthcare workers are at an elevated risk of exposure to viral infections, and the effects of COVID-19 on their oral microbiome remain relatively unexplored.

Methods

Oropharyngeal swab specimens, collected one month after a negative COVID-19 test from a cohort comprising 55 healthcare workers, underwent 16S rRNA sequencing. We conducted a comparative analysis between this post-COVID-19 cohort and the pre-infection dataset from the same participants. Community composition analysis, indicator species analysis, alpha diversity assessment, beta diversity exploration, and functional prediction were evaluated.

Results

The Shannon and Simpson indexes of the oral microbial community declined significantly in the post-COVID-19 group when compared with the pre-infection cohort. Moreover, there was clear intergroup clustering between the two groups. In the post-COVID-19 group, the phylum Firmicutes showed a significant increase. Further, there were clear differences in relative abundance of several bacterial genera in contrast with the pre-infection group, including Streptococcus, Gemella, Granulicatella, Capnocytophaga, Leptotrichia, Fusobacterium, and Prevotella. We identified Gemella enrichment in the post-COVID-19 group, potentially serving as a recovery period performance indicator. Functional prediction revealed lipopolysaccharide biosynthesis downregulation in the post-COVID-19 group, an outcome with host inflammatory response modulation and innate defence mechanism implications.

Conclusion

During the recovery phase of COVID-19, the oral microbiome diversity of front-line healthcare workers failed to fully return to its pre-infection state. Despite the negative COVID-19 test result one month later, notable disparities persisted in the composition and functional attributes of the oral microbiota.

Quantitative analysis of the effects of brushing, flossing, and mouthrinsing on supragingival and subgingival plaque microbiota: 12-week clinical trial

BACKGROUND

Translational microbiome research using next-generation DNA sequencing is challenging due to the semi-qualitative nature of relative abundance data. A novel method for quantitative analysis was applied in this 12-week clinical trial to understand the mechanical vs. chemotherapeutic actions of brushing, flossing, and mouthrinsing against the supragingival dental plaque microbiome. Enumeration of viable bacteria using vPCR was also applied on supragingival plaque for validation and on subgingival plaque to evaluate interventional effects below the gingival margin.

METHODS

Subjects with gingivitis were enrolled in a single center, examiner-blind, virtually supervised, parallel group controlled clinical trial. Subjects with gingivitis were randomized into brushing only (B); brushing and flossing (BF); brushing and rinsing with Listerine® Cool Mint® Antiseptic (BA); brushing and rinsing with Listerine® Cool Mint® Zero (BZ); or brushing, flossing, and rinsing with Listerine® Cool Mint® Zero (BFZ). All subjects brushed twice daily for 1 min with a sodium monofluorophosphate toothpaste and a soft-bristled toothbrush. Subjects who flossed used unflavored waxed dental floss once daily. Subjects assigned to mouthrinses rinsed twice daily. Plaque specimens were collected at the baseline visit and after 4 and 12 weeks of intervention. Bacterial cell number quantification was achieved by adding reference amounts of DNA controls to plaque samples prior to DNA extraction, followed by shallow shotgun metagenome sequencing.

RESULTS

286 subjects completed the trial. The metagenomic data for supragingival plaque showed significant reductions in Shannon-Weaver diversity, species richness, and total and categorical bacterial abundances (commensal, gingivitis, and malodor) after 4 and 12 weeks for the BA, BZ, and BFZ groups compared to the B group, while no significant differences were observed between the B and BF groups. Supragingival plaque vPCR further validated these results, and subgingival plaque vPCR demonstrated significant efficacy for the BFZ intervention only.

CONCLUSIONS

This publication reports on a successful application of a quantitative method of microbiome analysis in a clinical trial demonstrating the sustained and superior efficacy of essential oil mouthrinses at controlling dental plaque compared to mechanical methods. The quantitative microbiological data in this trial also reinforce the safety and mechanism of action of EO mouthrinses against plaque microbial ecology and highlights the importance of elevating EO mouthrinsing as an integral part of an oral hygiene regimen.

TRIAL REGISTRATION

The trial was registered on ClinicalTrials.gov on 31/10/2022. The registration number is NCT05600231.

Periodontal pathogen Aggregatibacter actinomycetemcomitans JP2 correlates with colonic leukocytes decrease and gut microbiome imbalance in mice

AIM

Evidence suggests that translocation of oral pathogens through the oral-gut axis may induce intestinal dysbiosis. This study aimed to evaluate the impact of a highly leukotoxic Aggregatibacter actinomycetemcomitans (Aa) strain on the gut microbiota, intestinal mucosal integrity and immune system in healthy mice.

METHODS

Eight-week-old male C57BL6 mice were divided into control (n = 16) and JP2 groups (n = 19), which received intragastric gavage with PBS and with a suspension of Aa JP2 (HK921), respectively, twice a week for 4 weeks. Colonic lamina propria, fecal material, serum, gingival tissues, and mandibles were obtained for analyses of leukocyte populations, inflammatory mediators, mucosal integrity, alveolar bone loss, and gut microbiota. Differences between groups for these parameters were examined by non-parametric tests.

RESULTS

The gut microbial richness and the number of colonic macrophages, neutrophils, and monocytes were significantly lower in Aa JP2-infected mice than in controls (p < .05). In contrast, infected animals showed higher abundance of Clostridiaceae, Lactobacillus taiwanensis, Helicobacter rodentium, higher levels of IL-6 expression in colonic tissues, and higher splenic MPO activity than controls (p < .05). No differences in tight junction expression, serum endotoxin levels, and colonic inflammatory cytokines were observed between groups. Infected animals presented also slightly more alveolar bone loss and gingival IL-6 levels than controls (p < .05).

CONCLUSION

Based on this model, intragastric administration of Aa JP2 is associated with changes in the gut ecosystem of healthy hosts, characterized by less live/recruited myeloid cells, enrichment of the gut microbiota with pathobionts and decrease in commensals. Negligible levels of colonic pro-inflammatory cytokines, and no signs of mucosal barrier disruption were related to these changes.

Ecological drivers of CRISPR immune systems

CRISPR-Cas is the only known adaptive immune system of prokaryotes. It is a powerful defense system against mobile genetic elements such as bacteriophages. While CRISPR-Cas systems can be found throughout the prokaryotic tree of life, they are distributed unevenly across taxa and environments. Since adaptive immunity is more useful in environments where pathogens persist or reoccur, the density and/or diversity of the host/pathogen community may drive the uneven distribution of CRISPR system. We directly tested hypotheses connecting CRISPR incidence with prokaryotic density/diversity by analyzing 16S rRNA and metagenomic data from publicly available environmental sequencing projects. In terms of density, we found that CRISPR systems are significantly favored in lower abundance (less dense) taxa and disfavored in higher abundance taxa, at least in marine environments. When we extended this work to compare taxonomic diversity between samples, we found CRISPR system incidence strongly correlated with diversity in human oral environments. Together, these observations confirm that, at least in certain types of environments, the prokaryotic ecological context indeed plays a key role in selecting for CRISPR immunity.

Importance

2Microbes must constantly defend themselves against viral pathogens, and a large proportion of prokaryotes do so using the highly effective CRISPR-Cas adaptive immune system. However, many prokaryotes do not. We investigated the ecological factors behind this uneven distribution of CRISPR-Cas immune systems in natural microbial populations. We found strong patterns linking CRISPR-Cas systems to prokaryotic density within ocean environments and to prokaryotic diversity within human oral environments. Our study validates previous within-lab experimental results that suggested these factors might be important and confirms that local environment and ecological context interact to select for CRISPR immunity.

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PrimerEvalPy: a tool for in-silico evaluation of primers for targeting the microbiome

BACKGROUND

The selection of primer pairs in sequencing-based research can greatly influence the results, highlighting the need for a tool capable of analysing their performance in-silico prior to the sequencing process. We therefore propose PrimerEvalPy, a Python-based package designed to test the performance of any primer or primer pair against any sequencing database. The package calculates a coverage metric and returns the amplicon sequences found, along with information such as their average start and end positions. It also allows the analysis of coverage for different taxonomic levels.

RESULTS

As a case study, PrimerEvalPy was used to test the most commonly used primers in the literature against two oral 16S rRNA gene databases containing bacteria and archaea. The results showed that the most commonly used primer pairs in the oral cavity did not match those with the highest coverage. The best performing primer pairs were found for the detection of oral bacteria and archaea.

CONCLUSIONS

This demonstrates the importance of a coverage analysis tool such as PrimerEvalPy to find the best primer pairs for specific niches. The software is available under the MIT licence at https://gitlab.citius.usc.es/lara.vazquez/PrimerEvalPy .

Antimicrobial efficacy of direct air gas soft jet plasma for the in vitro reduction of oral bacterial biofilms

The aim of this study was to evaluate the antimicrobial efficacy of an air gas soft jet CAP for its potential use in removing oral biofilms, given that plasma-based technologies have emerged as promising methods in periodontology. Two types of biofilms were developed, one by Streptococcus mutans UA 159 bacterial strain and the other by a complex mixture of saliva microorganisms isolated from a patient with periodontitis. This latter biofilm was characterized via Next Generation Sequencing to determine the main bacterial phyla. The CAP source was applied at a distance of 6 mm for different time points. A statistically significant reduction of both CFU count and XTT was already detected after 60 s of CAP treatment. CLSM analysis supported CAP effectiveness in killing the microorganisms inside the biofilm and in reducing the thickness of the biofilm matrix. Cytotoxicity tests demonstrated the possible use of CAP without important side effects towards human gingival fibroblasts cell line. The current study showed that CAP treatment was able to significantly reduce preformed biofilms developed by both S. mutans and microorganisms isolated by a saliva sample. Further studies should be conducted on biofilms developed by additional saliva donors to support the potential of this innovative strategy to counteract oral pathogens responsible for periodontal diseases.

Human Milk Microbiome-A Review of Scientific Reports

One of the most important bioactive components of breast milk are free breast milk oligosaccharides, which are a source of energy for commensal intestinal microorganisms, stimulating the growth of Bifidobacterium, Lactobacillus, and Bacteroides in a child's digestive tract. There is some evidence that maternal, perinatal, and environmental-cultural factors influence the modulation of the breast milk microbiome. This review summarizes research that has examined the composition of the breast milk microbiome and the factors that may influence it. The manuscript highlights the potential importance of the breast milk microbiome for the future development and health of children. The origin of bacteria in breast milk is thought to include the mother's digestive tract (entero-mammary tract), bacterial exposure to the breast during breastfeeding, and the retrograde flow of breast milk from the infant's mouth to the woman's milk ducts. Unfortunately, despite increasingly more precise methods for assessing microorganisms in human milk, the topic of the human milk microbiome is still quite limited and requires scientific research that takes into account various conditions.

Injectable hydrogels activated with copper sulfide nanoparticles for enhancing spatiotemporal sterilization and osteogenesis in periodontal therapy

Developing biomaterials capable of promoting bone regeneration in bacteria-infected sites is of utmost urgency for periodontal disease therapies. Here we produce a hybrid hydrogel by integrating CuS nanoparticles (CuSNPs), which could kill bacteria through photothermal therapy (PTT) triggered by a near infrared (NIR) light, and a gelatin methacryloyl (GelMA) hydrogel, which is injectable and biocompatible. Specifically, CuSNPs were precipitated by chitosan (CS) firstly, then grafted with methacrylic anhydride (MA) to form CuSNP@CS-MA, which was photo-crosslinked with GelMA to synthesize hybrid hydrogels (GelMA/CuSNP). The hybrid hydrogels exhibited a broad-spectrum antibacterial property that could be spatiotemprorally manipulated through applying a NIR light. Their mechanical properties were adjustable by controlling the concentration of CuSNPs, enabling the hydrogels to become more adapted to the oral diseases. Meanwhile, the hybrid hydrogels showed good cytocompatibility in vitro and improved hemostasis in vivo. Moreover, they accelerated alveolar osteogenesis and vascular genesis, successfully treating periodontis in four weeks in a rat model. GelMA/CuSNP hydrogels showed a broad-spectrum sterilization ability via PTT in vitro and outstanding antibacterial property in vivo, suggesting that the hybrid hydrogels could function in the challenging, bacteria-rich, oral environment. Such injectable hybrid hydrogels, capable of achieving both facilitated osteogenesis and NIR-inducible sterilization, represent a new biomaterial for treating periodontitis.

Oral microbiome dysbiosis among cigarette smokers and smokeless tobacco users compared to non-users

Tobacco use significantly influences the oral microbiome. However, less is known about how different tobacco products specifically impact the oral microbiome over time. To address this knowledge gap, we characterized the oral microbiome of cigarette users, smokeless tobacco users, and non-users over 4 months (four time points). Buccal swab and saliva samples (n = 611) were collected from 85 participants. DNA was extracted from all samples and sequencing was carried out on an Illumina MiSeq, targeting the V3-V4 region of the 16S rRNA gene. Cigarette and smokeless tobacco users had more diverse oral bacterial communities, including a higher relative abundance of Firmicutes and a lower relative abundance of Proteobacteria, when compared to non-users. Non-users had a higher relative abundance of Actinomyces, Granulicatella, Haemophilus, Neisseria, Oribacterium, Prevotella, Pseudomonas, Rothia, and Veillonella in buccal swab samples, compared to tobacco users. While the most abundant bacterial genera were relatively constant over time, some species demonstrated significant shifts in relative abundance between the first and last time points. In addition, some opportunistic pathogens were detected among tobacco users including Neisseria subflava, Bulleidia moorei and Porphyromonas endodontalis. Overall, our results provide a more holistic understanding of the structure of oral bacterial communities in tobacco users compared to non-users.

Dental plaque microbiota sequence counts for microbial profiling and resistance genes detection

Shotgun metagenomics sequencing experiments are finding a wide range of applications. Nonetheless, there are still limited guidelines regarding the number of sequences needed to acquire meaningful information for taxonomic profiling and antimicrobial resistance gene (ARG) identification. In this study, we explored this issue in the context of oral microbiota by sequencing with a very high number of sequences (~ 100 million), four human plaque samples, and one microbial community standard and by evaluating the performance of microbial identification and ARGs detection through a downsampling procedure. When investigating the impact of a decreasing number of sequences on quantitative taxonomic profiling in the microbial community standard datasets, we found some discrepancies in the identified microbial species and their abundances when compared to the expected ones. Such differences were consistent throughout downsampling, suggesting their link to taxonomic profiling methods limitations. Overall, results showed that the number of sequences has a great impact on metagenomic samples at the qualitative (i.e., presence/absence) level in terms of loss of information, especially in experiments having less than 40 million reads, whereas abundance estimation was minimally affected, with only slight variations observed in low-abundance species. The presence of ARGs was also assessed: a total of 133 ARGs were identified. Notably, 23% of them inconsistently resulted as present or absent across downsampling datasets of the same sample. Moreover, over half of ARGs were lost in datasets having less than 20 million reads. This study highlights the importance of carefully considering sequencing aspects and suggests some guidelines for designing shotgun metagenomics experiments with the final goal of maximizing oral microbiome analyses. Our findings suggest varying optimized sequence numbers according to different study aims: 40 million for microbiota profiling, 50 million for low-abundance species detection, and 20 million for ARG identification. KEY POINTS: • Forty million sequences are a cost-efficient solution for microbiota profiling • Fifty million sequences allow low-abundance species detection • Twenty million sequences are recommended for ARG identification.

Accelerated corrosion of 316L stainless steel in a simulated oral environment via extracellular electron transfer and acid metabolites of subgingival microbiota

316L stainless steel (SS) is widely applied as microimplant anchorage (MIA) due to its excellent mechanical properties. However, the risk that the oral microorganisms can corrode 316L SS is fully neglected. Microbiologically influenced corrosion (MIC) of 316L SS is essential to the health and safety of all patients because the accelerated corrosion caused by the oral microbiota can trigger the release of Cr and Ni ions. This study investigated the corrosion behavior and mechanism of subgingival microbiota on 316L SS by 16S rRNA and metagenome sequencing, electrochemical measurements, and surface characterization techniques. Multispecies biofilms were formed by the oral subgingival microbiota in the simulated oral anaerobic environment on 316L SS surfaces, significantly accelerating the corrosion in the form of pitting. The microbiota samples collected from the subjects differed in biofilm compositions, corrosion behaviors, and mechanisms. The oral subgingival microbiota contributed to the accelerated corrosion of 316L SS via acidic metabolites and extracellular electron transfer. Our findings provide a new insight into the underlying mechanisms of oral microbial corrosion and guide the design of oral microbial corrosion-resistant materials.

Effects of a stabilized stannous fluoride dentifrice on clinical, immunomodulatory, and microbial outcomes in a human experimental gingivitis model

BACKGROUND

Stannous fluoride dentifrice is well established for its beneficial clinical effects. In this study, we evaluated the effects of stannous fluoride on inflammation and oral microbiome.

METHODS

In this randomized, parallel-arm, double-blind, controlled clinical trial, we compared clinical resolution of experimental gingivitis by evaluating bleeding on probing, gingival index, and plaque index between stannous fluoride stabilized with zinc phosphate (test) and sodium fluoride (control) dentifrices. Further, these groups were compared for oral neutrophil counts, systemic priming of neutrophils, gingival crevicular fluid (GCF) expression of inflammatory markers, and the oral microbiome.

RESULTS

We found significant reduction in bleeding on probing in the test group compared to the control group in experimental gingivitis when participants used the test dentifrice prior to induction of experimental gingivitis. The test group also showed significant reductions in GCF levels of inflammatory markers (matrix metalloproteinase 8 [MMP8], receptor activator of nuclear factor kappa-Β ligand [RANKL]), oral polymorphonuclear neutrophil (PMN) counts, and systemic neutrophil priming (CD11b expression) during experimental gingivitis. Further, significant reductions in the gram-negative genera Porphyromonas, Tannerella, and Treponema were noted in the test group.

CONCLUSION

The stannous fluoride stabilized with zinc phosphate dentifrice formulation demonstrated clinical reduction in gingival inflammation and a beneficial effect on microbiome and immune markers. This intervention should be explored as a preventive aid in the progression of plaque-induced gingivitis to periodontitis.

Oral health as a modifiable risk factor for cardiovascular diseases

Cardiovascular diseases (CVDs) are a leading cause of morbidity and mortality worldwide with a high socioeconomic burden. Increasing evidence supports a convincing connection with increased cardiovascular risk of periodontal diseases (PD), a group of widespread, debilitating, and costly dysbiotic relapsing-remitting inflammatory diseases of the tissues supporting the teeth. Herein, we ensembled the best available evidence on the connection between CVDs and PD to review the recently emerging concept of the latter as a non-traditional risk factor for CVDs. We focused on oral dysbiosis, inflammation-associated molecular and cellular mechanisms, and epigenetic changes as potential causative links between PD and CVDs. The available evidence on the effects of periodontal treatment on cardiovascular risk factors and diseases was also described.

Bacterial contamination of air and surfaces during dental procedures-An experimental pilot study using Staphylococcus aureus

OBJECTIVE

The oral cavity contains numerous microorganisms, including antimicrobial-resistant bacteria. These microorganisms can be transmitted via respiratory particles from patients to healthcare providers and vice versa during dental care. We evaluated the spread of Staphylococcus aureus during standardized dental procedures using different scaling devices and rinsing solutions.

METHODS

During systematic therapy for dental biofilm removal (guided biofilm therapy), using an airflow or ultrasound device to a model simulation head. Staphylococcus aureus suspension was injected into the mouth of the model to mimic saliva. Different suction devices (conventional saliva ejector or a prototype) and rising solutions (water or chlorhexidine) were used. To assess contamination with S. aureus, an air-sampling device was placed near the oral cavity and samples of surface areas were collected.

RESULTS

S. aureus was only detected by air sampling when the conventional saliva ejector with airflow was used. No growth was observed during treatments with the ultrasonic piezo instrument or the prototype suction device. Notably, a rinsing solution of chlorhexidine digluconate decreased the bacterial load compared to water. Surface contamination was rarely detected (1 of 120 samples).

CONCLUSIONS

Although our findings indicate potential airborne bacterial transmission during routine prophylactic procedures, specific treatment options during biofilm removal appear to reduce air contamination. These options include ultrasonic piezo devices or the prototype suction device. The use of chlorhexidine reduced the CFU counts of S. aureus detected by air sampling. Surface contamination during dental procedures was a rare occurrence.

Commensal Oral Microbiota, Disease Severity, and Mortality in Fibrotic Lung Disease

Rationale: Oral microbiota associate with diseases of the mouth and serve as a source of lung microbiota. However, the role of oral microbiota in lung disease is unknown. Objectives: To determine associations between oral microbiota and disease severity and death in idiopathic pulmonary fibrosis (IPF). Methods: We analyzed 16S rRNA gene and shotgun metagenomic sequencing data of buccal swabs from 511 patients with IPF in the multicenter CleanUP-IPF (Study of Clinical Efficacy of Antimicrobial Therapy Strategy Using Pragmatic Design in IPF) trial. Buccal swabs were collected from usual care and antimicrobial cohorts. Microbiome data were correlated with measures of disease severity using principal component analysis and linear regression models. Associations between the buccal microbiome and mortality were determined using Cox additive models, Kaplan-Meier analysis, and Cox proportional hazards models. Measurements and Main Results: Greater buccal microbial diversity associated with lower FVC at baseline (mean difference, -3.60; 95% confidence interval [CI], -5.92 to -1.29% predicted FVC per 1-unit increment). The buccal proportion of Streptococcus correlated positively with FVC (mean difference, 0.80; 95% CI, 0.16 to 1.43% predicted per 10% increase) (n = 490). Greater microbial diversity was associated with an increased risk of death (hazard ratio, 1.73; 95% CI, 1.03-2.90), whereas a greater proportion of Streptococcus was associated with a reduced risk of death (HR, 0.85; 95% CI, 0.73 to 0.99). The Streptococcus genus was mainly composed of Streptococcus mitis species. Conclusions: Increasing buccal microbial diversity predicts disease severity and death in IPF. The oral commensal S. mitis spp associates with preserved lung function and improved survival.

Response of salivary microbiome to temporal, environmental, and surface characteristics under in vitro exposure

The microbiome of saliva stains deposited at crime scenes and in everyday settings is valuable for forensic investigations and environmental ecology. However, the dynamics and applications of microbial communities in these saliva stains have not been fully explored. In this study, we analyzed saliva samples that were exposed to indoor conditions for up to 1 year and to different carriers (cotton, sterile absorbent cotton swab, woolen, dacron) in both indoor and outdoor environments for 1 month using high-throughput sequencing. The analysis of microbial composition and Mfuzz clustering showed that the salivary flora, specifically Streptococcus (cluster7), which was associated with microbial contamination, remained stable over short periods of time. However, prolonged exposure led to significant differences due to the invasion of environmental bacteria such as Pseudomonas and Achromobacter. The growth and colonization of environmental flora were promoted by humidity. The neutral model predictions indicated that the assembly of salivary microbial communities in outdoor environments was significantly influenced by stochastic processes, with environmental characteristics having a greater impact on community change compared to surface characteristics. By incorporating data from previous studies on fecal and vaginal secretion microbiology, we developed RF and XGBoost classification models that achieved high accuracy (>98 %) and AUC (>0.8). Additionally, a RF regression model was created to determine the time since deposition (TsD) of the stains. Time inference models yielded a mean absolute error (MAE) of 7.1 days for stains exposed for 1 year and 14.2 h for stains exposed for 14 days. These findings enhance our understanding of the changes in the microbiome of saliva stains over time, in different environments, and on different surfaces. They also have potential applications in assessing potential microbial contamination, identifying body fluids, and inferring the time of deposition.

Awareness and Periodontal Health Practices of Fixed Orthodontic Appliance Patients: A Questionnaire-Based Survey

A well-aligned dentition is more conducive to periodontal health, which is necessary for successful orthodontic therapy. Maintaining good dental hygiene is crucial for effective treatment, and patient cooperation, education, motivation, and attitude are all important components. Orthodontists must routinely check in with their patients to see whether they are maintaining their oral hygiene and if they are using any additional assistance. Negligence on the part of the patient may be the cause of poor treatment outcomes. This study aims to show how patient education can affect treatment outcomes and the development of a functional, aesthetically pleasing, and healthy dentition. Aim This study aims to investigate awareness, attitude, and periodontal health knowledge among orthodontic patients. Objectives The study explores the level of awareness and knowledge regarding periodontal health among orthodontic patients, examining its correlation with factors such as age, attitude, and duration of orthodontic treatment. Additionally, it aims to gauge the extent of education received by orthodontic patients regarding proper oral hygiene practices and the potential repercussions of neglecting them. Methods A questionnaire-based study with a cross-sectional design was performed in Jeddah, Saudi Arabia. A total of 428 participants were randomly selected from several private orthodontic clinics and hospitals. The participants in the study were individuals currently undergoing treatment with fixed orthodontic appliances. Information was gathered using a self-administered questionnaire. Results The patients undergoing orthodontic treatment have a moderate understanding of periodontal disease about dental plaque. The level of awareness of periodontal health was 41%, and the level of knowledge about periodontal health was 51%. When it came to periodontal health, adult orthodontic patients had a positive attitude toward fixed orthodontic treatment (mean score = 0.75). Subjects' attitudes regarding fixed orthodontic treatment were significantly impacted by the patient's consistency with his/her dental checkups (p value = 0.02). Conclusion The patients' periodontal health awareness was moderate, while their periodontal health knowledge was fair. Orthodontic patient's awareness levels, as well as knowledge levels, showed significant differences in age and duration but not sex. Results showed no significant difference among the attitude levels of orthodontic patients and age, sex, and duration.

Microbiological assessment of success and failure in pulp revitalization: a randomized clinical trial using calcium hydroxide and chlorhexidine gluconate in traumatized immature necrotic teeth

Aim

To compare differences in the disinfection efficacy of calcium hydroxide (CH) and chlorhexidine gluconate (CHD) dressings in pulp revitalization (PR) of traumatized immature necrotic teeth; to investigate the microflora in successful/failed PR and whether bacterial persistence influences the outcomes of PR.

Methods

Microbiological assessment of the average bacterial load (CFU/sample) and bacterial diversity (taxa/sample) was performed on 41 teeth at three timepoints (S2-before, S3-after debridement and S5- after root canal dressing).

Results

The primary microflora was more diverse in successful cases than in failed. Decreases in CFU/sample and taxa/sample occurred S2 - S3, though new increases occurred at S5 in the CHD subgroup (successful and failed) and CFU/sample in the CH subgroup (failed). At S5, the successful cases showed more bacterial decreases. No specific species was associated with the outcomes with no statistical differences between the disinfection efficacy.

Conclusions

There were no statistical differences in CH and CHD efficacy. At S5, microflora persisted in both successful and failed outcomes, but the abundance and diversity increased significantly only in the failed cases. The successful outcomes presented higher diversity and higher decreases of the primary microflora at S5 than the failed outcomes. The abundance and diversity increased significantly at S5 only in failed cases.

Probiotic Effect of Streptococcus dentisani on Oral Pathogens: An In Vitro Study

Probiotics, including Streptococcus dentisani, have been proposed as an alternative to re-establish the ecology of the oral cavity and inhibit the formation of pathogenic biofilms. The main objective of this work was to assess the probiotic ability of S. dentisani against Streptococcus mutans, Streptococcus mitis, and Candida albicans biofilms. The ability of the strains to form a monospecies biofilm and the probiotic potential of S. dentisani using the competition, exclusion, and displacement strategies were determined. All strains were moderate biofilm producers. The ability of S. dentisani to compete with and exclude S. mutans and S. mitis during biofilm formation was not significant. However, S. dentisani significantly reduced pathologic streptococcal biofilms using the displacement strategy. Also S. dentisani reduced the formation of the C. albicans biofilm mainly through competition and displacement. In vitro, S. dentisani exhibited probiotic potential to reduce the formation of potentially pathogenic biofilms. Further investigation is required to understand the biofilm-inhibiting mechanisms exhibited by this probiotic strain.

Comparative Lipidomics of Oral Commensal and Opportunistic Bacteria

The oral cavity contains a vast array of microbes that contribute to the balance between oral health and disease. In addition, oral bacteria can gain access to the circulation and contribute to other diseases and chronic conditions. There are a limited number of publications available regarding the comparative lipidomics of oral bacteria and fungi involved in the construction of oral biofilms, hence our decision to study the lipidomics of representative oral bacteria and a fungus. We performed high-resolution mass spectrometric analyses (<2.0 ppm mass error) of the lipidomes from five Gram-positive commensal bacteria: Streptococcus oralis, Streptococcus intermedius, Streptococcus mitis, Streptococcus sanguinis, and Streptococcus gordonii; five Gram-positive opportunistic bacteria: Streptococcus mutans, Staphylococcus epidermis, Streptococcus acidominimus, Actinomyces viscosus, and Nanosynbacter lyticus; seven Gram-negative opportunistic bacteria: Porphyromonas gingivalis. Prevotella brevis, Proteus vulgaris, Fusobacterium nucleatum, Veillonella parvula, Treponema denticola, and Alkermansia muciniphila; and one fungus: Candida albicans. Our mass spectrometric analytical platform allowed for a detailed evaluation of the many structural modifications made by microbes for the three major lipid scaffolds: glycerol, sphingosine and fatty acyls of hydroxy fatty acids (FAHFAs).

Microbial Profiles in Oral Lichen Planus: Comparisons with Healthy Controls and Erosive vs. Non-Erosive Subtypes

Recent studies have begun exploring the potential involvement of microbiota in the pathogenesis of oral lichen planus (OLP), yet comprehensive investigations remain limited. Hence, this study aimed to compare the microbial profiles in saliva samples obtained from patients with OLP against those from healthy controls (HC), along with a comparison between erosive (E) and non-erosive (NE) OLP patients. Saliva samples were collected from 60 OLP patients (E: n = 25, NE: n = 35) and 30 HC individuals. Analysis revealed no significant differences in alpha diversity, as assessed by the Chao1 and Shannon index, across the three groups. However, Bray-Curtis distance analysis indicated a significant disparity in microbiome composition distribution between HC and E-OLP, as well as HC and NE-OLP groups. The six most abundant phyla observed across the groups were Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Fusobacteria, and Saccharibacteria (TM7). Notably, OLP groups exhibited a higher prevalence of Bacteroidetes. Prevotella emerged as the predominant genus in the OLP groups, while Capnocytophaga showed a relatively higher prevalence in E-OLP compared to NE-OLP. This study's findings indicate a notable difference in microbiota composition between HC and patients with OLP. Additionally, differences in the microbiome were identified between the E-OLP and NE-OLP groups. The increase in the proportion of certain bacterial species in the oral microbiome suggests that they may exacerbate the inflammatory response and act as antigens for OLP.

Early life factors and oral microbial signatures define the risk of caries in a Swedish cohort of preschool children

The oral cavity harbors complex communities comprising bacteria, archaea, fungi, protozoa, and viruses. The oral microbiota is establish at birth and develops further during childhood, with early life factors such as birth mode, feeding practices, and oral hygiene, reported to influence this development and the susceptibility to caries. We here analyzed the oral bacterial composition in saliva of 260 Swedish children at two, three and five years of age using 16S rRNA gene profiling to examine its relation to environmental factors and caries development at five years of age. We were able to assign the salivary bacterial community in each child at each time point to one of seven distinct clusters. We observed an individual dynamic in the development of the oral microbiota related to early life factors, such as being first born, born by C-section, maternal perinatal antibiotics use, with a distinct transition between three and five years of age. Different bacterial signatures depending on age were related to increased caries risk, while Peptococcus consistently linked to reduced risk of caries development.

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.

Short-Chain Fatty Acid (SCFA) as a Connecting Link between Microbiota and Gut-Lung Axis-A Potential Therapeutic Intervention to Improve Lung Health

The microbiome is an integral part of the human gut, and it plays a crucial role in the development of the immune system and homeostasis. Apart from the gut microbiome, the airway microbial community also forms a distinct and crucial part of the human microbiota. Furthermore, several studies indicate the existence of communication between the gut microbiome and their metabolites with the lung airways, called "gut-lung axis". Perturbations in gut microbiota composition, termed dysbiosis, can have acute and chronic effects on the pathophysiology of lung diseases. Microbes and their metabolites in lung stimulate various innate immune pathways, which modulate the expression of the inflammatory genes in pulmonary leukocytes. For instance, gut microbiota-derived metabolites such as short-chain fatty acids can suppress lung inflammation through the activation of G protein-coupled receptors (free fatty acid receptors) and can also inhibit histone deacetylase, which in turn influences the severity of acute and chronic respiratory diseases. Thus, modulation of the gut microbiome composition through probiotic/prebiotic usage and fecal microbiota transplantation can lead to alterations in lung homeostasis and immunity. The resulting manipulation of immune cells function through microbiota and their key metabolites paves the way for the development of novel therapeutic strategies in improving the lung health of individuals affected with various lung diseases including SARS-CoV-2. This review will shed light upon the mechanistic aspect of immune system programming through gut and lung microbiota and exploration of the relationship between gut-lung microbiome and also highlight the therapeutic potential of gut microbiota-derived metabolites in the management of respiratory diseases.

Bacterial contamination potential of personal protective equipment itself in dental aerosol-producing treatments

Personal protective equipment (PPE) has long been a high priority in dental aerosol-producing treatments. Since COVID-19 pandemic, its importance has increased yet again. While importance of PPE in preventing transmission and thus possible infection of pathogens is well known, contamination potential of PPE after treatment itself is less investigated. This review aims to give an overview of the current literature and contamination potential (viral, blood, bacterial) of components of protective equipment itself. The literature search was performed using the Medline database; furthermore, a hand search was conducted. Last search took place on 23 November 2022. Two categories of hygiene-related keywords were formed (category A: mask, face shield, goggles, eyewear, personal protective equipment; category B: contamination, aerosol). Each keyword from one category was combined with all keywords from the other one. In addition, the keyword "dental" was always added. First, a title and abstract screening was performed. Afterward, a full-text analysis was followed for the included studies. A total of 648 search hits were found in the Medline database. 47 were included after title and abstract screening. 22 studies were excluded after full-text analysis, 25 studies were included. The hand search resulted in 4 studies that were included. Bacterial contamination of PPE after treatment has been adequately studied, contamination with blood less. Microorganisms mainly originate from the oral and cutaneous flora; however, a transmission of potential pathogens like Staphylococcus aureus or Escherichia coli was also described. Studies showing transmission pathways starting from PPE and its various components are lacking. No measures have yet been described that fully protect the protective equipment from contamination. There is growing awareness that PPE itself can be a source of pathogen transmission, and thus possible infection. Therefore, not only wearing of protective clothing, but also conscious handling of it is crucial for transmission and possible infection prevention. However, studies showing transmission pathways starting from PPE and its various components are lacking. Several studies have investigated what measures can be taken to protect the protective equipment itself. So far, none of the methods evaluated can prevent contamination of PPE.

Changes in oral health during aging in a novel non-human primate model

Oral health plays a significant role in the quality of life and overall well-being of the aging population. However, age-related changes in oral health are not well understood due to challenges with current animal models. In this study, we analyzed the oral health and microbiota of a short-lived non-human primate (i.e., marmoset), as a step towards establishing a surrogate for studying the changes that occur in oral health during human aging. We investigated the oral health of marmosets using cadaveric tissues in three different cohorts: young (aged ≤6 years), middle-aged, and older (>10 years) and assessed the gingival bacterial community using analyses of the V3-V4 variable region of 16S rRNA gene. The oldest cohort had a significantly higher number of dental caries, increased dental attrition/erosion, and deeper periodontal pocket depth scores. Oral microbiome analyses showed that older marmosets had a significantly greater abundance of Escherichia-Shigella and Propionibacterium, and a lower abundance of Agrobacterium/Rhizobium at the genus level. Alpha diversity of the microbiome between the three groups showed no significant differences; however, principal coordinate analysis and non-metric multidimensional scaling analysis revealed that samples from middle-aged and older marmosets were more closely clustered than the youngest cohort. In addition, linear discriminant analysis effect size (LEFSe) identified a higher abundance of Esherichia-Shigella as a potential pathogenic biomarker in older animals. Our findings confirm that changes in the oral microbiome are associated with a decline in oral health in aging marmosets. The current study suggests that the marmoset model recapitulates some of the changes in oral health associated with human aging and may provide opportunities for developing new preventive strategies or interventions which target these disease conditions.

Phage therapy: A renewed approach against oral diseases caused by Enterococcus faecalis infections

Antibiotics play an important role in the treatment of infectious diseases. Long-term overuse or misuse of antibiotics, however, has triggered the global crisis of antibiotic resistance, bringing challenges to treating clinical infection. Bacteriophages (phages) are the viruses infecting bacterial cells. Due to high host specificity, high bactericidal activity, and good biosafety, phages have been used as natural alternative antibacterial agents to fight against multiple drug-resistant bacteria. Enterococcus faecalis is the main species detected in secondary persistent infection caused by failure of root canal therapy. Due to strong tolerance and the formation of biofilm, E. faecalis can survive the changes in pH, temperature, and osmotic pressure in the mouth and thus is one of the main causes of periapical lesions. This paper summarizes the advantages of phage therapy, its applications in treating oral diseases caused by E. faecalis infections, and the challenges it faces. It offers a new perspective on phage therapy in oral diseases.

Treatment of dental biofilm-forming bacterium Streptococcus mutans using tannic acid-mediated gold nanoparticles

Biosynthesized gold nanoparticles (AuNPs) are highly attracted as a biocompatible nanodrug to treat various diseased conditions in humans. In this study, phytochemical tannic acid-mediated AuNPs (TA-AuNPs) are successfully synthesized and tested for antibacterial and antibiofilm activity against dental biofilm-forming Streptococcus mutans biofilm. The synthesized TA-AuNPs are appeared as spherical in shape with an average size of 19 nm. The antibacterial potential of TA-AuNPs was evaluated using ZOI and MIC measurements; while, antibiofilm efficacy was measured by checking the eradication of preformed biofilm on the tooth model. The ZOI and MIC values for TA-AuNPs are 25 mm in diameter and 4 μg/mL, respectively. The MTT assay, CLSM, and SEM results demonstrate that the preformed S. mutans biofilm is completely eradicated at 4xMIC (16 μg/mL) of TA-AuNPs. Finally, the present study reveals that the synthesized TA-AuNPs might be a great therapeutic drug to treat dental biofilm-forming bacterium S. mutans.

Oral bacteriome and oral potentially malignant disorders: A systematic review of the associations

INTRODUCTION

Periodontal bacteria can infiltrate the epithelium, activate signaling pathways, induce inflammation, and block natural killer and cytotoxic cells, all of which contribute to the vicious circle of carcinogenesis. It is unknown whether oral dysbiosis has an impact on the etiology or prognosis of OPMD.

AIMS

Within this paradigm, this work systemically investigated and reported on the composition of oral microbiota in patients with oral potentially malignant disorders (OPMD) versus healthy controls.

METHODS

Observational studies that reported next generation sequencing analysis of oral tissue or salivary samples and found at least three bacterial species were included. Identification, screening, citation analysis, and graphical synthesis were carried out.

RESULTS

For oral lichen planus (OLP), the bacteria with the highest abundance were Fusobacterium, Capnocytophaga, Gemella, Granulicatella, Porphyromonas, and Rothia; for oral leukoplakia (OLK), Prevotella. Streptococci levels in OLK and OLP were lower. The usage of alcohol or smoke had no effect on the outcomes.

CONCLUSIONS

An increase in periodontal pathogenic bacteria could promote the development and exacerbation of lichen. Effective bacteriome-based biomarkers are worthy of further investigation and application, as are bacteriome-based treatments.

Intracanal microbiome profiles of two apical periodontitis cases in one patient: A comparison with saliva and plaque profiles

OBJECTIVES

To determine the characteristics of the endodontic microbiome.

MATERIAL AND METHODS

Saliva, plaque, and infected root canal wall dentin of two teeth suffering from apical periodontitis were harvested from a 58-year-old man. Bacterial DNA was extracted from each sample, and 16S rRNA gene analysis targeting the V3-V4 region was conducted on the Illumina MiSeq platform using QIIME2. The functional potential of the microbiomes was inferred using PICRUSt2.

RESULTS

The four microbiomes were different in structure and membership, yet the nine most abundant metabolic pathways were common among them. The two endodontic microbiomes were more anaerobic, rich in Firmicutes, and scarce in Actinobacteriota and Proteobacteria, compared with saliva and plaque microbiomes. Their profiles were dissimilar despite their clinical and radiographic similarities.

CONCLUSIONS

The endodontic microbiomes were anaerobic, rich in Firmicutes, scarce in Actinobacteriota and Proteobacteria, and considerably varied within an individual.

Essential genes for Haemophilus parainfluenzae survival and biofilm growth

Haemophilus parainfluenzae ( Hp ) is a Gram-negative, pleomorphic rod, highly prevalent and abundant as a commensal in the human oral cavity, and an infrequent extraoral opportunistic pathogen. Hp occupies multiple niches in the oral cavity, including the tongue dorsum, keratinized gingiva, and the supragingival plaque biofilm. As a member of the HACEK group, Hp is also known to cause infective endocarditis. Additionally, case reports have identified Hp as the causative agent of meningitis, septic arthritis, chronic osteomyelitis, septicemia, and a variety of other infectious diseases. Little is known about how Hp interacts with its neighbors in the healthy biofilm nor about its mechanisms of pathogenesis as an extraoral opportunistic pathogen. To address these unknowns, we identified the essential genomes of two Hp strains and the conditionally essential genes for their growth in in vitro biofilms aerobically and anaerobically. Using transposon insertion sequencing (TnSeq) with a highly saturated mariner transposon library in two strains, the ATCC33392 type-strain ( Hp 392) and a commensal oral isolate EL1 ( Hp EL1), we show that the essential genome of Hp 392 and Hp EL1 is composed of 395 and 384 genes, respectively. The core essential genome, consisting of 341 essential genes conserved between both strains, was composed of genes associated with genetic information processing, carbohydrate, protein, and energy metabolism. We also identified conditionally essential genes for aerobic and anaerobic biofilm growth, which were associated with carbohydrate and energy metabolism in both strains of Hp . Additionally, RNAseq analysis determined that most genes upregulated during anaerobic growth are not essential for Hp 392 anaerobic biofilm survival. The completion of this library and analysis under these conditions gives us a foundational insight into the basic biology of H. parainfluenzae in differing oxygen conditions, similar to its in vivo oral habitat. Further, the creation of this library presents a valuable tool for further investigation into conditionally essential genes for an organism that lives in close contact with many microbial species in the human oral habitat.

Discovery of Bacterial Key Genes from 16S rRNA-Seq Profiles That Are Associated with the Complications of SARS-CoV-2 Infections and Provide Therapeutic Indications

SARS-CoV-2 infections, commonly referred to as COVID-19, remain a critical risk to both human life and global economies. Particularly, COVID-19 patients with weak immunity may suffer from different complications due to the bacterial co-infections/super-infections/secondary infections. Therefore, different variants of alternative antibacterial therapeutic agents are required to inhibit those infection-causing drug-resistant pathogenic bacteria. This study attempted to explore these bacterial pathogens and their inhibitors by using integrated statistical and bioinformatics approaches. By analyzing bacterial 16S rRNA sequence profiles, at first, we detected five bacterial genera and taxa (Bacteroides, Parabacteroides, Prevotella Clostridium, Atopobium, and Peptostreptococcus) based on differentially abundant bacteria between SARS-CoV-2 infection and control samples that are significantly enriched in 23 metabolic pathways. A total of 183 bacterial genes were found in the enriched pathways. Then, the top-ranked 10 bacterial genes (accB, ftsB, glyQ, hldD, lpxC, lptD, mlaA, ppsA, ppc, and tamB) were selected as the pathogenic bacterial key genes (bKGs) by their protein-protein interaction (PPI) network analysis. Then, we detected bKG-guided top-ranked eight drug molecules (Bemcentinib, Ledipasvir, Velpatasvir, Tirilazad, Acetyldigitoxin, Entreatinib, Digitoxin, and Elbasvir) by molecular docking. Finally, the binding stability of the top-ranked three drug molecules (Bemcentinib, Ledipasvir, and Velpatasvir) against three receptors (hldD, mlaA, and lptD) was investigated by computing their binding free energies with molecular dynamic (MD) simulation-based MM-PBSA techniques, respectively, and was found to be stable. Therefore, the findings of this study could be useful resources for developing a proper treatment plan against bacterial co-/super-/secondary-infection in SARS-CoV-2 infections.