Differential analysis of culturable and unculturable subgingival target microorganisms according to the stages of periodontitis

Effects of Pro-inflammatory Cytokines Induced by Porphyromonas gingivalis on Cell Cycle Regulation in Brain Endothelial Cells

OBJECTIVES

Advanced periodontitis potentially contributes to Alzheimer's disease (AD) development and progression by altering the blood-brain barrier microenvironment in the cerebral microvascular endothelium. This results, in cytotoxicity, cell cycle disruption, and increased pro-inflammatory cytokine expression, allowing pathogens to enter the brain and damage the central nervous system (CNS). This study evaluated the effects of Porphyromonas gingivalis W83 infection on pro-inflammatory response, cell viability, and cell cycle regulation in mouse brain endothelial cells (mBECs).

METHODS

mBECs were stimulated with live P. gingivalis at different multiplicity of infection (MOI) values (1:5, 1:10, 1:50, 1:100, 1:200) for 6, 12, 24, and 48 h. Cell viability, cell cycle regulation, and pro-inflammatory cytokine mRNA expression were assessed using the alamarBlue assay, flow cytometry, and reverse transcription quantitative polymerase chain reaction (RT-qPCR), respectively.

RESULTS

P. gingivalis reduced cell viability, induced morphological changes in mBECs by >50% after 48 h (p < 0.05) and caused concentration-dependent arrest in the S and G0/G1 phases of the cell cycle at MOI=1:100 and 1:200. The Il6, Il1b, and tumor necrosis factor alpha (Tnf) mRNA expression increased significantly compared to that of the controls (p < 0.05).

CONCLUSIONS

P. gingivalis reduced cellular metabolism and induced early cell cycle arrest at the G0/G1 phase in MBEC cells. It also increased the pro-inflammatory response, which could be associated with cell death and possible senescence of brain endothelial cells. These results suggested a possible role for P. gingivalis in the pathogenesis of AD. Further studies are required to elucidate these underlying mechanisms.

Emerging oral Treponema membrane proteins disorder neutrophil phosphoinositide signaling via phosphatidylinositol-4-phosphate 5-kinase

Background

Periodontitis (PD) is a group of inflammatory pathologies characterized by destruction of the tooth-supporting tissues. During PD, dysbiosis of the oral biofilm disrupts the host immune response and supports growth of pathogenic bacteria including the spirochetes Treponema denticola (Td), T. maltophilum (Tm), and T. lecithinolyticum (Tl). The outer membrane protein of Td, Msp, perturbs the function of neutrophils by modulating phosphoinositide (PIP) signaling. While Tm and Tl have similar outer membrane proteins, MspA and MspTL respectively, little is known of how these proteins affect neutrophil function.

Methods

This study examines putative mechanisms by which T. maltophilum MspA and T. lecithinolyticum MspTL inhibit neutrophil chemotaxis. Murine bone marrow neutrophils were treated with recombinant MspA or MspTL protein. Protein phosphorylation was assessed via immunoblot, phosphate release by malachite green assay, and PTEN and SHIP phosphatase activity through immunoprecipitation, enzymatic assays, and chemical inhibition. PIP quantification was assessed by immunofluorescence microscopy and Mass ELISAs, while small GTPase activity was measured with G-Protein Activation Assays. Neutrophil F-actin localization was determined through immunofluorescence.

Results

MspA and MspTL increase phosphate release in neutrophils, but unlike Msp, they do not affect PTEN or SHIP activity, despite modulating cellular levels of multiple PIP species [PI(3,4)P2, PI(4,5)P2, and PIP3]. Overall, MspA and MspTL differentially affected the metabolism of individual PIP species, but both increased PI(4,5)P2 levels in a PIP5K-dependent manner. Downstream effects of disrupted PIP signaling included inhibition of Akt and Rac1 activation and increased cortical F-actin localization.

Conclusions

Understanding distinct mechanistic relationships between novel Msp proteins and neutrophils provides important insight into how these understudied bacteria promote periodontitis progression.

Bacteraemia and proinflammatory response after non-surgical periodontal therapy and adjunctive antibiotics in patients with recent acute coronary syndrome

INTRODUCTION

This study compares the incidence of bacteraemia and proinflammatory cytokines in short and long periods after non-surgical periodontal therapy involving premedication with amoxicillin (AMX) followed by AMX and metronidazole (MTZ) in patients with Acute Coronary Syndrome (ACS).

METHODS

This pilot study included twelve individuals with periodontitis and recent ACS. Six patients were treated with subgingival instrumentation (SI), and six with supragingival ultrasonic scaling (US). Amoxicillin 2 g was administered as premedication in the first visit, followed by AMX-MTZ for one week. The incidence of bacteraemia was evaluated using hemoculture, qPCR, and next-generation sequencing (NGS) before the treatment (t0) and 30 min later (t1) (quadrants 1 and 2), and after one-week, pre-post-treatment samples were taken from the re-maining quadrants (t3 and t4). Proinflammatory cytokines were evaluated in serum at baseline (t0), one week (t1), and six months (t5).

RESULTS

Bacteraemia was low in 16.6 %, similar in both treatment groups. Porphyromonas gingivalis and Desulfobulbus oralis (16.6 %), Filifactor alocis, Eubacterium saphenum, Eubacterium brachy (8.3 %) were identified with qPCR. NGS was only detected in a single patient; at time t0, bacteria were more diverse than at t3 and were associated with the phyla Bacteroidetes and Proteobacteria. Interestingly, many clones observed in blood were non-oral. After treatment, all cytokines were reduced significantly in the SI group in the long term (p< 0.05).

CONCLUSIONS

Periodontal therapy reduced bacteremia: despite the antibiotic regimen, bacteria remained in peripheral blood, which could be associated with antimicrobial resistance. SI produced a more efficient reduction of proinflammatory cytokines after periodontal treatment in individuals with ACS.

Submucosal Microbiome Profiles in Paired and Unpaired Samples From Healthy and Peri-Implantitis Dental Implants

BACKGROUND

This cross-sectional study aimed to compare the composition of the submucosal microbiome of peri-implantitis with paired and unpaired healthy implant samples.

METHODS

We evaluated submucosal plaque samples obtained in 39 cases, including 13 cases of peri-implantitis, 13 cases involving healthy implants from the same patient (paired samples), and 13 cases involving healthy implants from different individuals (unpaired samples). The patients were evaluated using next-generation genomic sequencing (Illumina) based on 16S rRNA gene amplification. The sequences were grouped according to the amplicon sequence variant (ASV) to define the taxonomic categories. Alpha diversity was analyzed using Shannon's and Simpson's indices, while beta diversity was evaluated using principal coordinate analysis, analysis of similarities, and permutational multivariate variance analysis. Additionally, UniFrac distances were evaluated using Quantitative Insights into Microbial Ecology 2. Finally, we evaluated between-group differences in the taxonomic components.

RESULTS

There were no significant between-group differences in alpha diversity. The average bacterial ratios of Filifactor alocis, Porphyromona endodontalis, Tannerella forsythia, Treponema denticola, Peptostreptococcaceae [Eubacterium nodatum], Desulfobulbus sp. HTM 041, and Mogibacterium timidum significantly differed between peri-implantitis samples and unpaired samples from the healthy implants (p < 0.05). However, there were few differences in the microbiota between peri-implantitis samples and those paired with healthy implants in the same patient.

CONCLUSIONS

Future studies comparing the microbiome compositions using sequencing techniques between healthy implants and implants with peri-implantitis should focus on retrieving samples from the same patient, especially in individuals with a history of periodontitis.

Recent progress in understanding the role of bacterial extracellular DNA: focus on dental biofilm

Dental biofilm is a highly complicated and dynamic structure comprising not only microbial communities but also the surrounding matrix of extracellular polymeric substances (EPS), including polysaccharides, proteins, extracellular DNA (eDNA) and other biopolymers. In recent years, the important role of bacterial eDNA in dental biofilms has gradually attracted attention. In this review, we present recent studies on the presence, dynamic conformation and release of oral bacterial eDNA. Moreover, updated information on functions associated with oral bacterial eDNA in biofilm formation, antibiotic resistance, activation of the immune system and immune evasion is highlighted. Finally, we summarize the role of oral bacterial eDNA as a promising target for the treatment of oral diseases. Increasing insight into the versatile roles of bacterial eDNA in dental biofilms will facilitate the prevention and treatment of biofilm-induced oral infections.

Exploring the Efficacy of Novel Therapeutic Strategies for Periodontitis: A Literature Review

Periodontitis, a prevalent oral condition, is facing difficulties in therapeutic approaches, sometimes leading to failure. This literature review was conducted to investigate the diversity of other therapeutic approaches and their potential contributions to the successful management of the disease. This research scrutinized the alterations in microbial diversity and imbalances in crucial microbial species, which contribute significantly to the pathogenesis of periodontitis. Within the limitations of this study, we highlight the importance of understanding the treatment plan's role in periodontitis disease, opening the way for further research and innovative treatment plans to mitigate the impact of periodontitis on oral health. This will aid both healthcare professionals and patients in preventing and effectively treating periodontitis, ultimately improving oral health outcomes and overall systemic health and well-being.

Oral microbiome associated with differential ratios of Porphyromonas gingivalis and Streptococcus cristatus

Periodontitis has recently been defined as a dysbiotic disease caused by an imbalanced oral microbiota. The transition from commensal microbial communities to periodontitis-associated ones requires colonization by specific pathogens, including Porphyromonas gingivalis. We previously reported an antagonistic relationship between Streptococcus cristatus and P. gingivalis. To determine the role of S. cristatus in altering the interactions of P. gingivalis with other oral bacteria in a complex context, we collected dental plaque samples from patients with periodontitis and assigned them to two groups based on the ratios of S. cristatus and P. gingivalis. We then characterized the microbial profiles of the dental plaque samples using shotgun metagenomic sequencing and compared the oral microbial composition and functional capabilities of the group with high S. cristatus-P. gingivalis ratios with the low ratio group. Taxonomic annotation revealed significant differences in the microbial composition at both the genus and species levels between the low and high S. cristatus-P. gingivalis ratio groups. Notably, a higher microbial diversity was observed in the samples with low S. cristatus-P. gingivalis ratios. Furthermore, the antibiotic resistance gene profiles of the two groups were also distinct, with a significantly increased abundance of the genes in the dental plaque samples with low S. cristatus-P. gingivalis ratios. It, therefore, indicates that the S. cristatus-P. gingivalis ratios influenced the virulence potential of the oral microbiome. Our work shows that enhancing the S. cristatus-P. gingivalis ratio in oral microbial communities can be an attractive approach for revising the dysbiotic oral microbiome.IMPORTANCEPeriodontitis, one of the most common chronic diseases, is linked to several systemic diseases, such as cardiovascular disease and diabetes. Although Porphyromonas gingivalis is a keystone pathogen that causes periodontitis, its levels, interactions with accessory bacteria and pathobionts in the oral microbiome, and its association with the pathogenic potential of the microbial communities are still not well understood. In this study, we revealed the role of Streptococcus cristatus and the ratios of S. cristatus and P. gingivalis in modulating the oral microbiome to facilitate a deeper understanding of periodontitis and its progression. The study has important clinical implications as it laid a foundation for developing novel non-antibiotic therapies against P. gingivalis and improving the efficiency of periodontal treatments.

Factors Associated with the Extent of Clinical Attachment Loss in Periodontitis: A Multicenter Cross-Sectional Study

Periodontitis has significant public health implications, affecting individuals' overall health, well-being, and quality of life. This study aimed to assess the risk factors associated with the extent of clinical attachment loss (CAL) in a population diagnosed with periodontitis. Six hundred and sixty-seven patients with different degrees of CAL (mild, n = 223; moderate, n = 256; and advanced, n = 188) were enrolled. Socio-demographics, lifestyle, microbiological profiles, specific immune response, obesity, and single-nucleotide polymorphism of the IL1 gene were determined. Unconditional logistic regression models were conducted to determine the factors associated with the extent of CAL. Aging, smoking, microbial factors, plaque index, and IgG2 antibodies against Aggregatibacter actinomycetemcomitans were associated with advanced CAL. IgG2 antibodies against A. actinomycetemcomitans (OR 1.50; CI 95% 1.23-1.81), plaque accumulation (OR 2.69; CI 95% 2.20-3.29), Porphyromonas gingivalis (OR 1.93; CI 95% 1.35-2.76), Tanerella forsythia (OR 1.88; CI 95%1.30-2.70), and current smoking (OR 1.94; CI 95% 1.31-2.87) were associated with advanced CAL. Gene IL polymorphisms, obesity, and stress were not associated with the extent of CAL. Aging, plaque accumulation, smoking, and having antibodies against A. actinomycetemcomitans were the most critical factors associated with advanced CAL. In contrast, obesity, stress, and gene polymorphisms were not associated with the extent of CAL.

Hypochlorous Acid as a Potential Postsurgical Antimicrobial Agent in Periodontitis: A Randomized, Controlled, Non-Inferiority Trial

BACKGROUND

Hypochlorous acid (HOCl) is an antimicrobial agent with high affinity to Gram-negative bacteria of the subgingival biofilm. It could have an equivalent or no inferiority effect to chlorhexidine (CHX) to avoid recolonization of these microorganisms after the post-surgical period.

OBJECTIVE

The objective is to compare the reduction of plaque index (PI), gingival index (GI), pocket depth (PD), gain of clinical attachment level (CAL), and bacterial recolonization of periodontopathic microorganisms in subgingival biofilm at 7, 21, and 90 days after Open Flap Debridement (OFD) under two antimicrobial protocols: (A) HOCl 0.05% followed by HOCl 0.025% and (B) CHX 0.2%/CHX 0.12% used per 21 days without regular oral hygiene during the post-surgical period.

MATERIAL AND METHODS

A no-inferiority randomized controlled trial was carried out. Thirty-two patients were randomly divided to receive each antiplaque protocol after OFD in patients with periodontitis. Clinical indexes and bacterial recolonization were assessed using qPCR for up to 90 days. Data were analyzed using repeated measures ANOVA, mixed effects models adjusted for treatment, time, and the Chi-squared/Fisher test. A no-inferiority analysis was also performed using the Hodges-Lehmann hypothesis test for non-inferiority.

RESULTS

HOCl was not inferior to CHX in reducing PI. Both groups showed a comparable reduction of recolonization for Porphyromonas gingivalis, Tannerella forsythia, and Eubacterium nodatum. However, the HOCl protocol was non-inferior to the CHX protocol for Treponema denticola and Aggregatibacter actinomicetemcomitans.

CONCLUSIONS

HOCl improved periodontal healing. HOCl showed an impact in reducing the recolonization of periodontopathic bacteria in the postoperative period.