Aggregatibacter actinomycetemcomitans (Aa) Under the Radar: Myths and Misunderstandings of Aa and Its Role in Aggressive Periodontitis

Molecular Analysis of Aggregatibacter actinomycetemcomitans ApiA, a Multi-Functional Protein

Aggregatibacter actinomycetemcomitans ApiA is a trimeric autotransporter outer membrane protein (Omp) that participates in multiple functions, enabling A. actinomycetemcomitans to adapt to a variety of environments. The goal of this study is to identify regions in the apiA gene responsible for three of these functions: auto-aggregation, buccal epithelial cell binding, and complement resistance. Initially, apiA was expressed in Escherichia coli. Finally, wild-type A. actinomycetemcomitans and an apiA-deleted version were tested for their expression in the presence and absence of serum and genes related to stress adaptation, such as oxygen regulation, catalase activity, and Omp proteins. Sequential deletions in specific regions in the apiA gene as expressed in E. coli were examined for membrane proteins, which were confirmed by microscopy. The functional activity of epithelial cell binding, auto-aggregation, and complement resistance were then assessed, and regions in the apiA gene responsible for these functions were identified. A region spanning amino acids 186-217, when deleted, abrogated complement resistance and Factor H (FH) binding, while a region spanning amino acids 28-33 was related to epithelial cell binding. A 13-amino-acid peptide responsible for FH binding was shown to promote serum resistance. An apiA deletion in a clinical isolate (IDH781) was created and tested in the presence and/or absence of active and inactive serum and genes deemed responsible for prominent functional activity related to A. actinomycetemcomitans survival using qRT-PCR. These experiments suggested that apiA expression in IDH781 is involved in global regulatory mechanisms that are serum-dependent and show complement resistance. This is the first study to identify specific apiA regions in A. actinomycetemcomitans responsible for FH binding, complement resistance, and other stress-related functions. Moreover, the role of apiA in overall gene regulation was observed.

Engineering Planar Gram-Negative Outer Membrane Mimics Using Bacterial Outer Membrane Vesicles

Antibiotic resistance is a major challenge in modern medicine. The unique double membrane structure of Gram-negative bacteria limits the efficacy of many existing antibiotics and adds complexity to antibiotic development by limiting transport of antibiotics to the bacterial cytosol. New methods to mimic this barrier would enable high-throughput studies for antibiotic development. In this study, we introduce an innovative approach to modify outer membrane vesicles (OMVs) from Aggregatibacter actinomycetemcomitans, to generate planar supported lipid bilayer membranes. Our method first involves the incorporation of synthetic lipids into OMVs using a rapid freeze-thaw technique to form outer membrane hybrid vesicles (OM-Hybrids). Subsequently, these OM-Hybrids can spontaneously rupture when in contact with SiO2 surfaces to form a planar outer membrane supported bilayer (OM-SB). We assessed the formation of OM-Hybrids using dynamic light scattering and a fluorescence quenching assay. To analyze the formation of OM-SBs from OM-Hybrids we used quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence recovery after photobleaching (FRAP). Additionally, we conducted assays to detect surface-associated DNA and proteins on OM-SBs. The interaction of an antimicrobial peptide, polymyxin B, with the OM-SBs was also assessed. These findings emphasize the capability of our platform to produce planar surfaces of bacterial outer membranes, which in turn, could function as a valuable tool for streamlining the development of antibiotics.

Periodontal diseases in Africa

Periodontal diseases, a group of complex conditions marked by an excessive immune response and periodontal tissue destruction, are a global health concern. Since 1990, the incidence of these diseases has doubled, with Western sub-Saharan Africa experiencing the highest burden. Accurate diagnosis and case identification are crucial for understanding the etiology, features of disease, research, treatment and prevention. Modern perspectives on periodontal disease classification are based on commonality among those affected. However, current literature is often plagued by methodological inconsistencies and focused on disease mechanisms in European populations. Health inequalities in low- and middle-income countries (LMICs) are exacerbated by these challenges, with sub-Saharan Africa, and Nigeria specifically, facing unique difficulties such as clinical personnel shortages and limited research infrastructure. This review explored disparities in periodontal disease research, care and outcomes in African populations. We highlighted these disparities and identified the factors contributing to inequities in periodontal health outcomes. We further demonstrated the critical need for inclusive and equitable healthcare and research practices tailored to the unique challenges faced by diverse populations and regions with limited resources. Addressing these disparities is essential for ensuring that advancements in healthcare are accessible to all, thereby improving global oral health and general health.

Connecting the dots: NETosis and the periodontitis-rheumatoid arthritis nexus

Periodontitis (PD) is characterized by the host's inflammatory responses to microbial dental biofilm dysbiosis, potentially resulting in tooth loss if left untreated. Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease leading to synovial inflammation and destruction of joint cartilage and bone. The suggested association between PD and RA is based on the potential of chronic inflammation present in periodontitis, which could induce alterations in proteins through post-translational modifications, leading to the formation of citrullinated and carbamylated protein antigens. Antibodies directed against these antigens can serve as biomarkers for the underlying immunological processes in RA. Recent studies have also focused on bacterial proteolytic enzymes released from PD-associated bacteria, such as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, which are also sources of these antibodies. Chronic inflammation in PD causes increased levels of inflammatory cytokines (interferon-α, interleukins-6 and 8, tumor necrosis factor-α) and neutrophil extracellular traps (NETs). The oral microbiota in PD is also associated with the release of NETs (a process known as NETosis). Elevated NET levels are a source of citrullinated and carbamylated proteins which highlights their role in an individual's risk of developing RA (pre-RA individuals) and the progression of chronic RA. This narrative review describes periodontitis and the dysbiotic subgingival microbiota and its role in NETosis as risk factors for inducing early RA and the prospects of identifying pre-RA individuals and seronegative RA patients with these risk factors.

A Rose by Any Other Name: The Long Intricate History of Localized Aggressive Periodontitis

This review addresses the recent World Workshop Consensus Conference (WWCC) decision to eliminate Localized Aggressive Periodontitis (LAgP) in young adults as a distinct form of periodontitis. A "Consensus" implies widespread, if not unanimous, agreement among participants. However, a significant number of attendees were opposed to the elimination of the LAgP classification. The substantial evidence supporting a unique diagnosis for LAgP includes the (1) incisor/molar pattern of disease, (2) young age of onset, (3) rapid progression of attachment and bone loss, (4) familial aggregation across multiple generations, and (5) defined consortium of microbiological risk factors including Aggregatibacter actinomycetemcomitans. Distinctive clinical signs and symptoms of LAgP are presented, and the microbial subgingival consortia that precede the onset of signs and symptoms are described. Using Bradford-Hill guidelines to assess causation, well-defined longitudinal studies support the unique microbial consortia, including A. actinomycetemcomitans as causative for LAgP. To determine the effects of the WWCC elimination of LAgP on research, we searched three publication databases and discovered a clear decrease in the number of new publications addressing LAgP since the new WWCC classification. The negative effects of the WWCC guidelines on both diagnosis and treatment success are presented. For example, due to the localized nature of LAgP, the practice of averaging mean pocket depth reduction or attachment gain across all teeth masks major changes in disease recovery at high-risk tooth sites. Reinstating LAgP as a distinct disease entity is proposed, and an alternative or additional way of measuring treatment success is recommended based on an assessment of the extension of the time to relapse of subgingival re-infection. The consequences of the translocation of oral microbes to distant anatomical sites due to ignoring relapse frequency are also discussed. Additional questions and future directions are also presented.

Genetics causal analysis of oral microbiome on type 2 diabetes in East Asian populations: a bidirectional two-sample Mendelian randomized study

Introduction

The dysbiosis of the oral microbiome is associated with the progression of various systemic diseases, including diabetes. However, the precise causal relationships remain elusive. This study aims to investigate the potential causal associations between oral microbiome and type 2 diabetes (T2D) using Mendelian randomization (MR) analyses.

Methods

We conducted bidirectional two-sample MR analyses to investigate the impact of oral microbiome from saliva and the tongue T2D. This analysis was based on metagenome-genome-wide association studies (mgGWAS) summary statistics of the oral microbiome and a large meta-analysis of GWAS of T2D in East Asian populations. Additionally, we utilized the T2D GWAS summary statistics from the Biobank Japan (BBJ) project for replication. The MR methods employed included Wald ratio, inverse variance weighting (IVW), weighted median, MR-Egger, contamination mixture (ConMix), and robust adjusted profile score (RAPS).

Results

Our MR analyses revealed genetic associations between specific bacterial species in the oral microbiome of saliva and tongue with T2D in East Asian populations. The MR results indicated that nine genera were shared by both saliva and tongue. Among these, the genera Aggregatibacter, Pauljensenia, and Prevotella were identified as risk factors for T2D. Conversely, the genera Granulicatella and Haemophilus D were found to be protective elements against T2D. However, different species within the genera Catonella, Lachnoanaerobaculum, Streptococcus, and Saccharimonadaceae TM7x exhibited multifaceted influences; some species were positively correlated with the risk of developing T2D, while others were negatively correlated.

Discussion

This study utilized genetic variation tools to confirm the causal effect of specific oral microbiomes on T2D in East Asian populations. These findings provide valuable insights for the treatment and early screening of T2D, potentially informing more targeted and effective therapeutic strategies.

Engineering Planar Gram-Negative Outer Membrane Mimics Using Bacterial Outer Membrane Vesicles

Antibiotic resistance is a major challenge in modern medicine. The unique double membrane structure of gram-negative bacteria limits the efficacy of many existing antibiotics and adds complexity to antibiotic development by limiting transport of antibiotics to the bacterial cytosol. New methods to mimic this barrier would enable high-throughput studies for antibiotic development. In this study, we introduce an innovative approach to modify outer membrane vesicles (OMVs) from Aggregatibacter actinomycetemcomitans, to generate planar supported lipid bilayer membranes. Our method first involves the incorporation of synthetic lipids into OMVs using a rapid freeze-thaw technique to form outer membrane hybrid vesicles (OM-Hybrids). Subsequently, these OM-Hybrids can spontaneously rupture when in contact with SiO2 surfaces to form a planar outer membrane supported bilayer (OM-SB). We assessed the formation of OM-Hybrids using dynamic light scattering and a fluorescence quenching assay. To analyze the formation of OM-SBs from OM-Hybrids we used quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence recovery after photobleaching (FRAP). Additionally, we conducted assays to detect surface-associated DNA and proteins on OM-SBs. The interaction of an antimicrobial peptide, polymyxin B, with the OM-SBs was also assessed. These findings emphasize the capability of our platform to produce planar surfaces of bacterial outer membranes, which in turn, could function as a valuable tool for streamlining the development of antibiotics.

Impact of Malocclusions on Periodontopathogenic Bacterial Load and Progression of Periodontal Disease: A Quantitative Analysis

BACKGROUND

(1) Periodontal disease (PD) is a globally prevalent chronic inflammatory condition, exacerbated by the dysbiosis of the oral microbiota. This study aims to evaluate the bacterial load of specific periodontopathogenic bacteria in patients with malocclusions (MAL) compared to those without. (2) Methods: Conducted at the "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania, this pilot study involved two groups: patients with MAL and PD, and patients with PD but without MAL. We included 20 patients: 10 with MAL (9 with crowding and 1 with an open bite) and 10 without MAL. Gingival crevicular fluid was collected for bacterial DNA extraction and quantified bacterial load using real-time PCR, focusing on 12 periodontopathogenic bacteria across different complexity classes. (3) Results: The study identified significantly higher concentrations of Treponema denticola (p = 0.023, median = 4.32, IQR = 2.76-5.53 vs. median = 1.93, IQR = 0-3.19), Tannerella forsythia (p = 0.020, mean = 6.04 ± 0.72 vs. mean = 4.4 ± 1.89) and Porphyromonas gingivalis (p = 0.002, median = 5.64, IQR = 4.94-5.98 vs. median = 2.48, IQR = 0-4.05) in patients with MAL compared to those without. This suggests that MAL contributes to an environment conducive to the proliferation of specific pathogens, potentially accelerating PD progression. Additionally, Eikenella corrodens (p = 0.040, mean = 4.55 ± 1.02 vs. mean = 3.23 ± 1.56), Campylobacter rectus (p < 0.001, mean = 4.2 ± 0.56 vs. mean = 1.8 ± 1.51), Prevotella intermedia (p = 0.043, median = 5.04, IQR = 0-5.49 vs. median = 0, IQR = 0-3.39), Capnocytophaga sputigena (p = 0.011, median = 5.91, IQR = 5.47-6.17 vs. median = 4.63, IQR = 3.83-5.64), and Capnocytophaga gingivalis (p = 0.007, median = 5.87, IQR = 5.34-6.03 vs. median = 4.4, IQR = 3.5-5.71) also showed elevated concentrations, indicating the broad impacts of MAL on oral microbial profiles. (4) Conclusions: The findings demonstrate a significant relationship between MAL and increased bacterial loads, underscoring the need for its integration in managing PD. Future research should expand demographic diversity and employ longitudinal designs to better understand the causative mechanisms at play.

Based on network pharmacology and molecular docking to explore the potential mechanism of shikonin in periodontitis

OBJECTIVES

To investigate the potential mechanisms of shikonin in preventing and treating periodontitis using network pharmacology and molecular docking methods.

MATERIALS AND METHODS

The targets of shikonin were obtained in TCMSP and SEA databases, and targets of periodontitis were gathered from the OMIM, GeneCards and Drugbank Databases. The intersecting targets were entered into the DAVID database to obtain the relevant biological functions and pathways by GO and KEGG enrichment analysis. The obtained targets were analysed the protein-protein interaction (PPI) in STRING platform. In Cytoscape 3.8.0, the network analysis function with the MCODE plug-in were used to obtain the key targets, of shikonin and periodontitis. Molecular docking and molecular dynamics simulation (MD) were used to assess the affinity between the shikonin and the key targets.

RESULTS

Shikonin was screened for 22 targets and periodontitis was screened for 944 targets, the intersecting targets were considered as potential therapeutic targets. The targets played important roles in cellular response to hypoxia, response to xenobiotic stimulus and positive regulates of apoptotic process by GO enrichment analysis. 10 significant pathways were analyzed by KEGG, such as human cytomegalovirus infection and PI3K-Akt signaling pathway, etc. Cytoscape software screened the key genes including AKT1, CCL5, CXCR4, PPARG, PTEN, PTGS2 and TP53. Molecular docking and MD results showed that shikonin could bind stably to the targets.

CONCLUSIONS

The present study enriched the molecular mechanisms in periodontitis with shikonin, providing potential therapeutic targets for periodontitis.

Aggregatibacter actinomycetemcomitans: From the Oral Cavity to the Heart Valves

Aggregatibacter actinomycetemcomitans (A. actinomycetecomitans) is a Gram-negative bacterial species that is an essential component of the oral microbiota. Due to its aggregative properties, it plays a role in the pathogenesis of human diseases. The presence of the surface proteins Fim, Briae, and microvesicles enables the bacterium to adhere to the epithelial surface and the tooth's surface. The presence of leukotoxin A (LtxA), which plays an important role in the pathogenicity of the bacterium, has been associated with both periodontitis and the etiology of rheumatoid arthritis (RA). A. actinomycetecomitans is also associated with several other systemic diseases and complications, such as endocarditis and different abscesses. In addition to leukotoxin A, A. actinomycetecomitans possesses several different virulence factors, including bacteriocins, chemotaxis inhibitory factors, cytotoxic factors, Fc-binding proteins, immunosuppressive factors, lipopolysaccharide collagenase, fibroblast inhibitory factors, antibiotic resistance determinants, adhesins, invasive factors and factors that inhibit the function of polymorphonuclear leukocytes. The ability of A. actinomycetemcomitans lipopolysaccharide to induce macrophages to secrete the interleukins IL-1, IL-1β, and tumor necrosis factor (TNF) is of considerable importance. The primary etiologic factor in the pathogenesis of periodontal disease is the oral biofilm colonized by anaerobic bacteria. Among these, A. actinomycetemcomitans occupies an important place as a facultative anaerobic bacterium. In addition, A. actinomycetemcomitans possesses many virulence factors that contribute to its potential to cause cancer. This article provides an overview of the virulence factors of A. actinomycetecomitans and its association with various systemic diseases, its oncogenic potential, and the treatment options for infections caused by A. actinomycetecomitans.

Grade C Molar-Incisor Pattern Periodontitis in Young Adults: What Have We Learned So Far?

Grade C molar-incisor pattern periodontitis (C-MIP) is a disease that affects specific teeth with an early onset and aggressive progression. It occurs in systemically healthy patients, mostly African descendants, at an early age, with familial involvement, minimal biofilm accumulation, and minor inflammation. Severe and rapidly progressive bone loss is observed around the first molars and incisors. This clinical condition has been usually diagnosed in children and young adults with permanent dentition under 30 years of age. However, this disease can also affect the primary dentition, which is not as frequently discussed in the literature. Radiographic records have shown that most patients diagnosed in the permanent dentition already presented disease signs in the primary dentition. A hyperresponsive immunological profile is observed in local (gingival crevicular fluid-GCF) and systemic environments. Siblings have also displayed a heightened inflammatory profile even without clinical signs of disease. A. actinomycetemcomitans has been classified as a key pathogen in C-MIP in both dentitions. Scaling and root planning associated with systemic antibiotics is the current gold standard to treat C-MIP, leading to GCF biomarker reduction, some systemic inflammatory response modulation and microbiome profile changes to a healthy-site profile. Further studies should focus on other possible disease-contributing risk factors.

Leukotoxin A Production and Release by JP2 and Non-JP2 Genotype Aggregatibacter actinomycetemcomitans in Relation to Culture Conditions

Aggressive forms of periodontitis, especially in young patients, are often associated with an increased proportion of the Gram-negative bacterium Aggregatibacter actinomycetemcomitans of the microbiota of the affected periodontal sites. One of the virulence factors of A. actinomycetemcomitans is a leukotoxin (LtxA) that induces a pro-inflammatory cell death process in leukocytes. A. actinomycetemcomitans exhibits a large genetic diversity and different genotypes vary in LtxA production capacity. The genotype JP2 is a heavy LtxA producer due to a 530-base pair deletion in the promoter for the toxin genes, and this trait has been associated with an increased pathogenic potential. The present study focused on the production and release of LtxA by different A. actinomycetemcomitans genotypes and serotypes under various growth conditions. Four different strains of this bacterium were cultured in two different culture broths, and the amount of LtxA bound to the bacterial surface or released into the broths was determined. The cultures were examined during the logarithmic and the early stationary phases of growth. The JP2 genotype exhibited the highest LtxA production among the strains tested, and production was not affected by the growth phase. The opposite was observed with the other strains. The composition of the culture broth had no effect on the growth pattern of the tested strains. However, the abundant release of LtxA from the bacterial surface into the culture broth was found in the presence of horse serum. Besides confirming the enhanced leucotoxicity of the JP2 genotype, the study provides new data on LtxA production in the logarithmic and stationary phases of growth and the effect of media composition on the release of the toxin from the bacterial membrane.

The efficacy of diode laser and subgingival air polishing with erythritol in treatment of periodontitis (clinical and microbiological study)

BACKGROUND

There is insufficient clinical and microbiological evidence to support the use of diode laser and air-polishing with erythritol as supplements to scaling and root planning(SRP). The aim of the current study is to evaluate the clinical and microbiologic efficacy of erythritol subgingival air polishing and diode laser in treatment of periodontitis.

METHODS

The study encompassed twenty-four individuals seeking periodontal therapy and diagnosed with stage I and stage II periodontitis. Eight patients simply underwent SRP. Eight more patients had SRP followed by erythritol subgingival air polishing, and eight patients had SRP followed by diode laser application. At baseline and six weeks, clinical periodontal parameters were measured, including Plaque Index (PI), Gingival Index (GI), periodontal Probing Depth (PPD), and Clinical Attachment Level (CAL). The bacterial count of Aggregatibacter actinomycetemcomitans(A.A), Porphyromonas gingivalis (P.G) was evaluated at different points of time.

RESULTS

The microbiological assessment revealed significant differences in the count of A.A. between the laser and erythritol groups immediately after treatment, indicating a potential impact on microbial levels. However, the microbial levels showed fluctuations over the subsequent weeks, without statistically significant differences. Plaque indices significantly decreased post-treatment in all groups, with no significant inter-group differences. Gingival indices decreased, and the laser group showed lower values than erythritol and control groups. PPD and CAL decreased significantly across all groups, with the laser group exhibiting the lowest values.

CONCLUSION

The supplementary use of diode laser and erythritol air polishing, alongside SRP, represents an expedited periodontal treatment modality. This approach leads to a reduction in bacteria and improvement in periodontal health.

TRIAL REGISTRATION

This clinical trial was registered on Clinical Trials.gov (Registration ID: NCT06209554) and released on 08/01/2024.

A Synthetic Small Molecule, LGM2605: A Promising Modulator of Increased Pro-Inflammatory Cytokine and Osteoclast Differentiation by Aggregatibacter actinomycetemcomitans Cytolethal Distending Toxin

Our research explores the interplay between Aggregatibacter actinomycetemcomitans (Aa) cytolethal distending toxin (Cdt) and the host's inflammatory response in molar/incisor pattern periodontitis (MIPP). Cdt disrupts phosphatidylinositol-3,4,5-triphosphate (PIP3) signaling, influencing cytokine expression through canonical and non-canonical inflammasome activation as well as nuclear factor-κB (NF-κB) activation, leading to inflammation in MIPP. THP-1 differentiated macrophages (TDMs) exposed to Cdt exhibited an upregulation of pro-inflammatory genes and subsequent cytokine release. We analyzed the ability of a small molecule therapeutic, LGM2605, known for its anti-inflammatory properties, to reduce pro-inflammatory gene expression and cytokine release in Cdt-exposed and Aa-inoculated TDMs. LGM2605's mechanism of action involves inhibiting NF-κB while activating the Nrf2-transcription factor and antioxidants. Herein, we show that this small molecule therapeutic mitigates Cdt-induced pro-inflammatory cytokine expression and secretion. Our study also further defines Cdt's impact on osteoclast differentiation and maturation in MIPP. Cdt promotes increased TRAP+ cells, indicating heightened osteoclast differentiation, specific to Cdt's phosphatase activity. Cathepsin K levels rise during this process, reflecting changes in TRAP distribution between control and Cdt-treated cells. Exploring LGM2605's effect on Cdt-induced osteoclast differentiation and maturation, we found TRAP+ cells significantly reduced with LGM2605 treatment compared to Cdt alone. Upon LGM2605 treatment, immunocytochemistry revealed a decreased TRAP intensity and number of multinucleated cells. Moreover, immunoblotting showed reduced TRAP and cathepsin K levels, suggesting LGM2605's potential to curb osteoclast differentiation and maturation by modulating inflammatory cytokines, possibly involving Nrf2 activation. In summary, our research reveals the intricate connections between Cdt, pro-inflammatory cytokines, and osteoclast differentiation, offering novel therapeutic possibilities for managing these conditions.

Microbiological Analysis of Plaque and Its Composition in Three Patient Groups under Different Orthodontic Treatments

BACKGROUND

This article analyzes differences in microbiological parameters and periodontal health conditions among three patient groups: those undergoing conventional orthodontic treatment with fixed appliances, patients undergoing orthodontic treatment with clear aligners, and a control group receiving no treatment.

MATERIALS AND METHODS

In this study, 60 patients were enrolled. The microbiological analysis employed a qualitative and semi-quantitative methodology of bacterial morphotype analysis.

RESULTS

The analyses revealed a significant difference in favor of clear oral and periodontal health aligners. This could be attributed to better bacterial biofilm removal and reduced mechanical stress on the periodontal ligament, factors facilitated by the ease of clear aligner removal. Significant differences (p-value < 0.05) were observed for the Full-Mouth Plaque Score, Full-Mouth Bleeding Score, Plaque Index, and periodontal health assessment measurements.

CONCLUSIONS

Although overall hygiene appears to be improved in patients in the aligners group compared to those treated with conventional orthodontic appliances, there are no statistically significant results regarding plaque composition. Microbiological aspects will be further addressed using more specific techniques in the follow-up of this research.

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.

Multivariate Analysis of Individual Bacterial Outer Membrane Vesicles Using Fluorescence Microscopy

Gram-negative bacteria produce outer membrane vesicles (OMVs) that play a critical role in cell-cell communication and virulence. OMVs have emerged as promising therapeutic agents for various biological applications such as vaccines and targeted drug delivery. However, the full potential of OMVs is currently constrained by inherent heterogeneities, such as size and cargo differences, and traditional ensemble assays are limited in their ability to reveal OMV heterogeneity. To overcome this issue, we devised an innovative approach enabling the identification of various characteristics of individual OMVs. This method, employing fluorescence microscopy, facilitates the detection of variations in size and surface markers. To demonstrate our method, we utilize the oral bacterium Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) which produces OMVs with a bimodal size distribution. As part of its virulence, A. actinomycetemcomitans secretes leukotoxin (LtxA) in two forms: soluble and surface associated with the OMVs. We observed a correlation between the size and toxin presence where larger OMVs were much more likely to possess LtxA compared to the smaller OMVs. In addition, we noted that, among the smallest OMVs (<100 nm diameter), the fractions that are toxin positive range from 0 to 30%, while the largest OMVs (>200 nm diameter) are between 70 and 100% toxin positive.

Multifunctional role of oral bacteria in the progression of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver disorders of varying severity, ultimately leading to fibrosis. This spectrum primarily consists of NAFL and non-alcoholic steatohepatitis. The pathogenesis of NAFLD is closely associated with disturbances in the gut microbiota and impairment of the intestinal barrier. Non-gut commensal flora, particularly bacteria, play a pivotal role in the progression of NAFLD. Notably, Porphyromonas gingivalis, a principal bacterium involved in periodontitis, is known to facilitate lipid accumulation, augment immune responses, and induce insulin resistance, thereby exacerbating fibrosis in cases of periodontitis-associated NAFLD. The influence of oral microbiota on NAFLD via the "oral-gut-liver" axis is gaining recognition, offering a novel perspective for NAFLD management through microbial imbalance correction. This review endeavors to encapsulate the intricate roles of oral bacteria in NAFLD and explore underlying mechanisms, emphasizing microbial control strategies as a viable therapeutic avenue for NAFLD.

Presence and Immunoreactivity of Aggregatibacter actinomycetemcomitans in Rheumatoid Arthritis

The presence of periodontal pathogens is associated with an increased prevalence of rheumatoid arthritis (RA). The systemic antibody response to epitopes of these bacteria is often used as a proxy to study correlations between bacteria and RA. The primary aim of the present study is to examine the correlation between the presence of Aggregatibacter actinomycetemcomitans (Aa) in the oral cavity and serum antibodies against the leukotoxin (LtxA) produced by this bacterium. The salivary presence of Aa was analyzed with quantitative PCR and serum LtxA ab in a cell culture-based neutralization assay. The analyses were performed on samples from a well-characterized RA cohort (n = 189) and a reference population of blood donors (n = 101). Salivary Aa was present in 15% of the RA patients and 6% of the blood donors. LtxA ab were detected in 19% of RA-sera and in 16% of sera from blood donors. The correlation between salivary Aa and serum LtxA ab was surprisingly low (rho = 0.55 [95% CI: 0.40, 0.68]). The presence of salivary Aa showed no significant association with any of the RA-associated parameters documented in the cohort. A limitation of the present study is the relatively low number of individuals with detectable concentrations of Aa in saliva. Moreover, in the comparison of detectable Aa prevalence between RA patients and blood donors, we assumed that the two groups were equivalent in other Aa prognostic factors. These limitations must be taken into consideration when the result from the study is interpreted. We conclude that a systemic immune response to Aa LtxA does not fully reflect the prevalence of Aa in saliva. In addition, the association between RA-associated parameters and the presence of Aa was negligible in the present RA cohort.

Aggregatibacter actinomycetemcomitans Cytolethal Distending Toxin Induces Cellugyrin-(Synaptogyrin 2) Dependent Cellular Senescence in Oral Keratinocytes

Recently, we reported that oral-epithelial cells (OE) are unique in their response to Aggregatibacter actinomycetemcomitans cytolethal distending toxin (Cdt) in that cell cycle arrest (G2/M) occurs without leading to apoptosis. We now demonstrate that Cdt-induced cell cycle arrest in OE has a duration of at least 7 days with no change in viability. Moreover, toxin-treated OE develops a new phenotype consistent with cellular senescence; this includes increased senescence-associated β-galactosidase (SA-β-gal) activity and accumulation of the lipopigment, lipofuscin. Moreover, the cells exhibit a secretory profile associated with cellular senescence known as the senescence-associated secretory phenotype (SASP), which includes IL-6, IL-8 and RANKL. Another unique feature of Cdt-induced OE senescence is disruption of barrier function, as shown by loss of transepithelial electrical resistance and confocal microscopic assessment of primary gingival keratinocyte structure. Finally, we demonstrate that Cdt-induced senescence is dependent upon the host cell protein cellugyrin, a homologue of the synaptic vesicle protein synaptogyrin. Collectively, these observations point to a novel pathogenic outcome in oral epithelium that we propose contributes to both A. actinomycetemcomitans infection and periodontal disease progression.

Awakening the sleeping giant: Epstein-Barr virus reactivation by biological agents

Epstein-Barr virus (EBV) may cause harm in immunocompromised conditions or on stress stimuli. Various chemical agents have been utilized to induce the lytic cycle in EBV-infected cells. However, apart from chemical agents and external stress stimuli, certain infectious agents may reactivate the EBV. In addition, the acute infection of other pathogens may provide suitable conditions for EBV to thrive more and planting the roots for EBV-associated pathologies. Various bacteria such as periodontal pathogens like Aggregatibacter, Helicobacter pylori, etc. have shown to induce EBV reactivation either by triggering host cells directly or indirectly. Viruses such as Human simplex virus-1 (HSV) induce EBV reactivation by HSV US3 kinase while other viruses such as HIV, hepatitis virus, and even novel SARS-CoV-2 have also been reported to cause EBV reactivation. The eukaryotic pathogens such as Plasmodium falciparum and Aspergillus flavus can also reactivate EBV either by surface protein interaction or as an impact of aflatoxin, respectively. To highlight the underexplored niche of EBV reactivation by biological agents, we have comprehensively presented the related information in this review. This may help to shedding the light on the research gaps as well as to unveil yet unexplored mechanisms of EBV reactivation.

The oral microbiome of a family including Papillon-Lefèvre-syndrome patients and clinically healthy members

AIMS

The oral microbiota composition of patients diagnosed with Papillon-Lefèvre-syndrome and treated for several years were compared to those existing in the oral cavity of the clinically healthy family members and a cohort of patients having various stages of chronic periodontitis.

MATERIALS AND METHODS

A family with two sisters affected with severe periodontitis and with the typical skin symptoms of Papillon-Lefèvre-syndrome, and symptomless parents and third sibling were investigated. The Patients received periodontal treatment for several years and their oral microbiome was analysed by amplicon sequencing. Data were evaluated by microbial cluster analysis.

RESULTS

The microbiome of the patients with Papillon-Lefèvre-syndrome was predominated with Aggregatibacter actinomycetemcomitans and associated oral periodontopathogens. Although the clinically healthy family members showed no oral disorder, their microbiome resembled that of subjects having mild periodontitis.

CONCLUSIONS

Predominance of A. actinomycetemcomitans in the subgingival microbiome of patients with Papillon-Lefèvre-syndrome suggests that specific treatment strategies directed against this pathobiont may improve the oral health status of the affected individuals.

TRIAL REGISTRATION

The study was conducted in accordance with the Declaration of Helsinki and the ethical permission has been issued by the Human Investigation Review Board of the University of Szeged, Albert Szent-Györgyi Clinical Centre (Permission No. 63/2017-SZTE). September 19, 2017.  https://u-szeged.hu/klinikaikutatas/rkeb-altal-jovahagyott/rkeb-2017 .

Effect of 15 days -6° head-down bed rest on microbial communities of supragingival plaque in young men

Introduction

The microgravity environment astronauts experience during spaceflight can lead to an increased risk of oral diseases and possible changes in oral microecology. In this study, we aimed to assess changes in the microbial community of supragingival plaques to explore the effects of spaceflight microgravity environment on oral microecology.

Methods

Sixteen healthy male volunteers were recruited, and supragingival plaque samples were collected under -6° head-down bed rest (HDBR) at five-time points: day 1 before HDBR; days 5, 10, and 15 of HDBR; and day 6 of recovery. Bacterial genomic DNA was sequenced using gene sequencing technology with 16S ribosomal ribonucleic acid V3-V4 hypervariable region amplification and the obtained data were analyzed bioinformatically.

Results

Alpha diversity analysis showed a significant increase in species richness in supragingival plaque samples on day 15 of HDBR compared with that at pre-HDBR. Beta diversity analysis revealed that the community composition differed among the groups. Species distribution showed that, compared with those at pre-HDBR, the relative abundances of Corynebacterium and Aggregatibacter increased significantly during HDBR, while those of Veillonella, Streptococcus, and Lautropia decreased significantly. Moreover, compared with those at pre-HDBR, the relative abundance of Leptotrichia increased significantly on day 6 of recovery, whereas the relative abundances of Porphyromonas and Streptococcus decreased significantly. Network analysis showed that the interaction relationship between the dominant genera became simpler during HDBR, and the positive and negative correlations between them showed dynamic changes. Phylogenetic investigation of communities by reconstruction of unobserved states analysis showed that the amino acid metabolism function of plaque microorganisms was more enriched during HDBR.

Discussion

In summary, in a 15-day simulated microgravity environment, the diversity, species distribution, interaction relationship, and metabolic function of the supragingival plaque microbial community changed, which suggests that microgravity may affect the oral microecosystem by changing the balance of supragingival plaque microbial communities and further leading to the occurrence and development of oral diseases.

Periodontal diseases in Thai schoolchildren. Clinical and microbiological observations

The prevalence of periodontitis among Thai schoolchildren is unknown. In a cross-sectional study, the prevalence and severity of periodontal diseases, in a group of Thai schoolchildren, along with the presence and numbers of bacterial species commonly associated with periodontitis were investigated. A consent form was sent out to 192 schoolchildren in one school (Chanachanupathom School) in Chana, Southern Thailand (in the age range of 12-18 years) and 119 attended for a clinical and microbiological examination. Clinical recordings included number of teeth present, DMFT, plaque index, bleeding index, clinical attachment loss (CAL), and probing pocket depth (PPD). Pooled plaque samples were analyzed with culture and qPCR against bacteria associated with periodontitis. The children had low caries experience (DMFT = 3.2 ± 2.3), poor oral hygiene, high bleeding scores, and 67 (56.3%) had at least one interproximal site with CAL ≥ 1 mm. Thirty-seven (31.1%) of the children were diagnosed with periodontitis stage I, and sixteen (13.4%) were classified as periodontitis Stage II. Aggregatibacter actinomycetemcomitans was sparsely found in all but the healthy clinical groups (gingivitis, periodontitis Stage I and II), while the groups showed a high prevalence of Fusobacterium spp., Prevotella intermedia/nigrescens, and Campylobacter species as well as of the periodontitis-associated species Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia. Thai schoolchildren have poor oral hygiene with abundant amounts of plaque and high presence of bleeding. Early onset periodontitis is common but mostly in its mild form and is not associated with the presence of A. actinomycetemcomitans.

Dual function of the O-antigen WaaL ligase of Aggregatibacter actinomycetemcomitans

Protein glycosylation is critical to the quaternary structure and collagen-binding activity of the extracellular matrix protein adhesin A (EmaA) associated with Aggregatibacter actinomycetemcomitans. The glycosylation of this large, trimeric autotransporter adhesin is postulated to be mediated by WaaL, an enzyme with the canonical function to ligate the O-polysaccharide (O-PS) antigen with a terminal sugar of the lipid A-core oligosaccharide of lipopolysaccharide (LPS). In this study, we have determined that the Escherichia coli waaL ortholog (rflA) does not restore collagen binding of a waaL mutant strain of A. actinomycetemcomitans but does restore O-PS ligase activity following transformation of a plasmid expressing waaL. Therefore, a heterologous E. coli expression system was developed constituted of two independently replicating plasmids expressing either waaL or emaA of A. actinomycetemcomitans to directly demonstrate the necessity of ligase activity for EmaA collagen binding. Proper expression of the protein encoded by each plasmid was characterized, and the individually transformed strains did not promote collagen binding. However, coexpression of the two plasmids resulted in a strain with a significant increase in collagen binding activity and a change in the biochemical properties of the protein. These results provide additional data supporting the novel hypothesis that the WaaL ligase of A. actinomycetemcomitans shares a dual role as a ligase in LPS biosynthesis and is required for collagen binding activity of EmaA.

Lactiplantibacillus plantarum GL001 alleviates jejunal oxidative damage induced by intestinal ischemia-reperfusion injury by influencing jejunal tissue metabolism through the improvement of jejunal microbial composition

Intestinal ischemia-reperfusion (IIR) injury is associated with inflammation and oxidative stress, yet its precise mechanisms remain not fully understood. IIR injury is closely linked to the gut microbiota and its metabolites. The anti-inflammatory and antioxidant effects of Lactiplantibacillus plantarum are specific to IIR. In our study, we conducted a 30-day pre-treatment of SD rats with both a standard strain of Lactiplantibacillus plantarum and Lactiplantibacillus plantarum GL001. After a 7-day cessation of treatment, we induced an IIR injury model to investigate the mechanisms by which Lactiplantibacillus plantarum alleviates IIR damage. The results demonstrate that Lactiplantibacillus plantarum effectively mitigates the inflammatory and oxidative stress damage induced by IIR. Lactiplantibacillus plantarum GL001 can improve the gut microbiota by reducing the abundance of harmful bacteria and increasing the abundance of beneficial bacteria. In IIR intestinal tissue, the levels of secondary bile acids are elevated. The content of the bacterial metabolite Calcimycin increases. Annotations of metabolic pathways suggest that Lactiplantibacillus plantarum GL001 can alleviate IIR damage by modulating calcium-phosphorus homeostasis through the regulation of parathyroid hormone synthesis, secretion, and action. Microbiota-metabolite correlation analysis reveals a significant negative correlation between calcimycin and Lactonacillus and a significant positive correlation between calcimycin and Shigella. There is also a significant positive correlation between calcimycin and secondary bile acids. Lactiplantibacillus plantarum GL001 can alleviate oxidative damage induced by IIR through improvements in gut microbiota and intestinal tissue metabolism.

Antimicrobial Activity of Zinc against Periodontal Pathogens: A Systematic Review of In Vitro Studies

Background and Objectives: More than a billion people worldwide suffer from chronic periodontitis. The primary etiological factor of periodontal diseases is dental plaque and the bacteria it contains, particularly Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Prevotella intermedia, and Aggregatibacter actinomycetemcomitans. Zinc, owing to its antibacterial properties, can be employed in periodontology. The objective of this review was to analyze scientific literature that examines the effects of zinc on periopathogens. Materials and methods: A systematic review protocol of scientific literature was designed following PRISMA recommendations. Data search was conducted in PubMed, Web of Science, and ScienceDirect databases. Full-text articles in English that examine the effects of zinc on periopathogens and were published between 2011 and 2021 were included. Results: Fifteen articles were included in the analysis based on inclusion criteria. ZnO exhibited antibacterial activity against P. gingivalis and P. intermedia (p < 0.001). The minimum inhibitory concentration against P. gingivalis was 10 μg/mL. ZnO demonstrated a significant antibacterial effect, as evidenced by inhibition zones of 15.10 mm for S. oralis, 13.36 mm for P. gingivalis, 12.98 mm for S. sanguis, and 14.01 mm for P. intermedia. Zn (II)-based polymers inhibited the ragA and ragB genes of P. gingivalis. Titanium dental implants coated with ZnO effectively disrupted the cell walls of P. gingivalis and A. actinomycetemcomitans. ZnO inhibited the growth of P. gingivalis within 2 h and the growth of F. nucleatum and P. intermedia within 3 h. ZnO exhibited nontoxic effects, and concentrations up to 0.8 mg/L increased cell survival rates by up to 90%. Conclusions: The analysis of the literature confirms the antibacterial action of zinc against periodontal pathogenic bacteria. At low concentrations, these substances do not exhibit cytotoxic effects on fibroblasts.

The role of NLRP3 in regulating gingival epithelial cell responses evoked by Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) has myriads of virulence factors among which leukotoxin provides A. actinomycetemcomitans with the advantage to thrive in the surrounding hostile environment and evade host immune defences. The NLRP3 inflammasome has been associated with periodontal disease development. However, our understanding of the involvement of caspase-1, caspase-4, and NLRP3 in the release of IL-1β and other inflammatory mediators from gingival epithelial cells during a A. actinomycetemcomitans infection is limited. The aim of this study was to investigate how the inflammasome-associated proteins caspase-1, caspase-4 and NLRP3 regulate the immune response of gingival epithelial cells during a A. actinomycetemcomitans infection. Human gingival epithelial cells (Ca9-22) deficient in NLRP3, caspase-1 or caspase-4 were created using CRISPR/Cas9. Gingival epithelial cells were stimulated with the A. actinomycetemcomitans low-leukotoxic strain NCTC9710 or the highly leukotoxic JP2 strain HK 165 for 6, 12 and 24 h. The results showed that the JP2 strain HK1651 induced higher IL-1β and IL-1RA release and mediated more epithelial cell death compared to the NCTC9710 strain. These findings were found to be capsase-1, caspase-4 and NLRP3-dependant. A targeted protein analysis of inflammation-related proteins showed that the expression of 37 proteins were identified as being significantly altered after HK1651 infection compared to unstimulated Cas9 and NLRP3-deficient cells. Of the 37 proteins, 23 of these inflammation-related proteins released by NLRP3-deficient cells differed significantly compared to Cas9 cells after infection. This suggests that NLRP3 has a broad effect on the inflammatory response in gingival epithelial cells.

Aggregatibacter actinomycetemcomitans cytolethal distending toxin modulates host phagocytic function

Cytolethal distending toxins (Cdt) are a family of toxins produced by several human pathogens which infect mucocutaneous tissue and induce inflammatory disease. Human macrophages exposed to Aggregatibacter actinomycetemcomitans (Aa) Cdt respond through canonical and non-canonical inflammasome activation to stimulate cytokine release. The inflammatory response is dependent on PI3K signaling blockade via the toxin's phosphatidylinositol-3,4,5-triphosphate (PIP3) phosphatase activity; converting PIP3 to phosphatidylinsoitol-3,4-diphosphate (PI3,4P2) thereby depleting PIP3 pools. Phosphoinositides, also play a critical role in phagosome trafficking, serving as binding domains for effector proteins during phagosome maturation and subsequent fusion with lysosomes. We now demonstrate that AaCdt manipulates the phosphoinositide (PI) pools of phagosome membranes and alters Rab5 association. Exposure of macrophages to AaCdt slowed phagosome maturation and decreased phago-lysosome formation, thereby compromising macrophage phagocytic function. Moreover, macrophages exposed to Cdt showed decreased bactericidal capacity leading to increase in Aggregatibacter actinomycetemcomitans survival. Thus, Cdt may contribute to increased susceptibility to bacterial infection. These studies uncover an underexplored aspect of Cdt function and provide new insight into the virulence potential of Cdt in mediating the pathogenesis of disease caused by Cdt-producing organisms such as Aa.

The interplay between oral microbiota, gut microbiota and systematic diseases

Over the past two decades, the importance of microbiota in health and disease has become evident. The human gut microbiota and oral microbiota are the largest and second-largest microbiome in the human body, respectively, and they are physically connected as the oral cavity is the beginning of the digestive system. Emerging and exciting evidence has shown complex and important connections between gut microbiota and oral microbiota. The interplay of the two microbiomes may contribute to the pathological processes of many diseases, including diabetes, rheumatoid arthritis, nonalcoholic fatty liver disease, inflammatory bowel disease, pancreatic cancer, colorectal cancer, and so on. In this review, we discuss possible routes and factors of oral microbiota to affect gut microbiota, and the contribution of this interplay between oral and gut microbiota to systemic diseases. Although most studies are association studies, recently, there have been increasing mechanistic investigations. This review aims to enhance the interest in the connection between oral and gut microbiota, and shows the tangible impact of this connection on human health.

Identifying size-dependent toxin sorting in bacterial outer membrane vesicles

Gram-negative bacteria produce outer membrane vesicles (OMVs) that play a critical role in cell-cell communication and virulence. Despite being isolated from a single population of bacteria, OMVs can exhibit heterogeneous size and toxin content, which can be obscured by assays that measure ensemble properties. To address this issue, we utilize fluorescence imaging of individual OMVs to reveal size-dependent toxin sorting. Our results showed that the oral bacterium Aggregatibacter actinomycetemcomitans (A.a.) produces OMVs with a bimodal size distribution, where larger OMVs were much more likely to possess leukotoxin (LtxA). Among the smallest OMVs (< 100 nm diameter), the fraction that are toxin positive ranges from 0-30%, while the largest OMVs (> 200 nm diameter) are between 70-100% toxin positive. Our single OMV imaging method provides a non-invasive way to observe OMV surface heterogeneity at the nanoscale level and determine size-based heterogeneities without the need for OMV fraction separation.

Evaluation of the antibacterial effect of hydroalcoholic extract of the galls of Quercus infectoria on Aggregatibacter actinomycetemcomitans

Background

Aggregatibacter actinomycetemcomitans (Aa) plays a vital role in some destructive forms of periodontitis. While mechanical and chemical plaque control is the first step in periodontitis treatment, side effects of adjunctive chemical agents such as chlorhexidine (CHX) mouthwash have led to the application of natural alternatives with minimal side effects. Therefore, this study evaluated the antibacterial effect of the hydroalcoholic extract of Quercus infectoria (Qi) galls on Aa in vitro.

Methods

The hydroalcoholic extract of Qi was obtained by the maceration method, and Aa bacterial strain was cultured. The inhibition zone diameter was measured through the agar well diffusion method. Also, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were determined by the broth microdilution method. All the experiments were repeated three times. 0.2% CHX was used as a control.

Results

The inhibition zone diameter of Aa increased with increasing concentration of Qi extract. While MIC and MBC values for CHX were 0.0039 and 0.0078 mg/mL, respectively, both MIC and MBC values of the Qi extract for this bacterium were similar, i.e., 2.5 mg/mL, which was significantly higherd.

Conclusion

Since other in vivo studies have confirmed the other properties of this extract and its safety in terms of cytotoxicity and mutagenicity, hydroalcoholic extract of Qi may be used in mouthwashes or local delivery systems to affect periodontal biofilm.

Prevalence of undiagnosed diabetes and prediabetes related to periodontitis and its risk factors in elderly individuals

OBJECTIVE

The prevalence of undiagnosed diabetes was estimated to increase with age and can reach 3.5%. The purpose of the study was to evaluate the prevalence of undiagnosed diabetes and prediabetes in the elderly patients who attended a dental clinic and to find common risk factors.

METHODS

Male patients, older than 50 years, attended their first dental visit to the School of Dentistry for a period of two years, and it was proposed to evaluate undiagnosed type 2 diabetes mellitus. Periodontal, biochemical, microbiological examinations, nutritional profile, and physical activity were performed.

RESULTS

A total of 106 patients were examined, 6 (5.6%) had diabetes, and 37 (34.9%) had prediabetes without prior diagnosis. The severity of periodontitis was greater in patients with diabetes. Most of the patients were overweight and had increased systolic blood pressure. Patients with prediabetes and periodontitis had a low adherence to the Mediterranean diet. Tannerella forsythia was present in more patients with periodontitis, and the prevalence of Aggregatibacter actinomycetemcomitans is practically absent in groups with periodontitis, except for the group with diabetes.

CONCLUSIONS

In the population studied, the prevalence of patients without a diagnosis of diabetes and prediabetes was very high and underestimated. The increased severity of periodontitis in patients with diabetes and in conjunction with the high level of cortisol seen in patients with periodontitis, especially those with diabetes, emphasize the dysregulation of the immunoinflammatory system.

CLINICAL SIGNIFICANCE

It is essential to add all this data to our dental practice to cover patient health with a broader landscape.

Periodontal microbiology and microbial etiology of periodontal diseases: Historical concepts and contemporary perspectives

This narrative review summarizes the collective knowledge on periodontal microbiology, through a historical timeline that highlights the European contribution in the global field. The etiological concepts on periodontal disease culminate to the ecological plaque hypothesis and its dysbiosis-centered interpretation. Reference is made to anerobic microbiology and to the discovery of select periodontal pathogens and their virulence factors, as well as to biofilms. The evolution of contemporary molecular methods and high-throughput platforms is highlighted in appreciating the breadth and depth of the periodontal microbiome. Finally clinical microbiology is brought into perspective with the contribution of different microbial species in periodontal diagnosis, the combination of microbial and host biomarkers for this purpose, and the use of antimicrobials in the treatment of the disease.

In Vitro Selection of Lactobacillus and Bifidobacterium Probiotic Strains for the Management of Oral Pathobiont Infections Associated to Systemic Diseases

The human oral pathobionts Aggregatibacter actinomycetemcomitans, Streptococcus mitis and Streptococcus mutans, in dysbiosis-promoting conditions, lead to oral infections, which also represent a threat to human systemic health. This scenario may be worsened by antibiotic misuse, which favours multi-drug resistance, making the research on pathogen containment strategies more than crucial. Therefore, we aimed to in vitro select the most promising probiotic strains against oral pathogen growth, viability, biofilm formation, and co-aggregation capacity, employing both the viable probiotics and their cell-free supernatants (CFSs). Interestingly, we also assessed probiotic efficacy against the three-pathogen co-culture, mimicking an environment similar to that in vivo. Overall, the results showed that Lactobacillus CFSs performed better than the Bifidobacterium, highlighting Limosilactobacillus reuteri LRE11, Lacticaseibacillus rhamnosus LR04, Lacticaseibacillus casei LC04, and Limosilactobacillus fermentum LF26 as the most effective strains, opening the chance to deeper investigation of their action and CFS composition. Altogether, the methodologies presented in this study can be used for probiotic efficacy screenings, in order to better focus the research on a viable probiotic, or on its postbiotics, suitable in case of infections.

Coating and Corruption of Human Neutrophils by Bacterial Outer Membrane Vesicles

Porphyromonas gingivalis is a keystone oral pathogen that successfully manipulates the human innate immune defenses, resulting in a chronic proinflammatory state of periodontal tissues and beyond. Here, we demonstrate that secreted outer membrane vesicles (OMVs) are deployed by P. gingivalis to selectively coat and activate human neutrophils, thereby provoking degranulation without neutrophil killing. Secreted granule components with antibacterial activity, especially LL-37 and myeloperoxidase (MPO), are subsequently degraded by potent OMV-bound proteases known as gingipains, thereby ensuring bacterial survival. In contrast to neutrophils, the P. gingivalis OMVs are efficiently internalized by macrophages and epithelial cells. Importantly, we show that neutrophil coating is a conserved feature displayed by OMVs of at least one other oral pathogen, namely, Aggregatibacter actinomycetemcomitans. We conclude that P. gingivalis deploys its OMVs for a neutrophil-deceptive strategy to create a favorable inflammatory niche and escape killing. IMPORTANCE Severe periodontitis is a dysbiotic inflammatory disease that affects about 15% of the adult population, making it one of the most prevalent diseases worldwide. Importantly, periodontitis has been associated with the development of nonoral diseases, such as rheumatoid arthritis, pancreatic cancer, and Alzheimer's disease. Periodontal pathogens implicated in periodontitis can survive in the oral cavity only by avoiding the insults of neutrophils while at the same time promoting an inflamed environment where they successfully thrive. Our present findings show that outer membrane vesicles secreted by the keystone pathogen Porphyromonas gingivalis provide an effective delivery tool of virulence factors that protect the bacterium from being killed while simultaneously activating human neutrophils.

Prevalence of Periodontal Pathogens in Slovak Patients with Periodontitis and Their Possible Aspect of Transmission from Companion Animals to Humans

Oral health and diseases are greatly influenced by oral bacteria. During dysbiosis, bacterial composition changes, which can lead to periodontitis. Periodontitis in humans is associated with periodontal pathogens such as Treponema denticola, Porphyromonas gingivalis, Tannerella forsythia and Aggregatibacter actinomycetemcomitans. Animal-to-human transmission of some of these pathogens has also been reported. The aim of this study was to evaluate the prevalence of periodontal pathogens in Slovak patients and to assess the possible risk of transmission of these pathogens from animals to their owners. The presence of periodontal pathogens in dental plaque was monitored by PCR. Amplified products were analysed using Sanger sequencing. T. forsythia isolates were assessed for the susceptibility to different antibiotics using the disk diffusion method. In humans, T. denticola, P. gingivalis, T. forsythia and A. actinomycetemcomitans were present in 69.23%, 69.23%, 100% and 84.62%, respectively. Most isolates of T. forsythia were susceptible to amoxicillin-clavulanic acid, clindamycin and moxifloxacin, but they were resistant to metronidazole. The transmission of T. forsythia from animals to their owners was not proven based on sequence analysing. On the other hand, transmission of Porphyromonas gulae was confirmed, but the risk of its involvement in the pathogenesis of periodontitis in humans must be further investigated.

Expression of Macrophage Polarization Markers against the Most Prevalent Serotypes of Aggregatibacter actinomycetemomitans

Aggregatibacter actinomycetemcomitans, a Gram-negative bacterium with seven serotypes (a–g) according to the structure of its LPS, has been defined as one of the most important pathogens in the development of a dysbiotic periodontal biofilm and the onset of periodontitis (an inflammatory chronic disease of the tissues around the teeth), where the serotype b is characterized as the most virulent compared with the other serotypes. The aim of this study was to evaluate the expression of the macrophage polarization markers M0, M1, and M2 against A. actinomycetemcomitans. Methods: THP-1 cells were infected with A. actinomycetemcomitans serotypes a, b, and c. The expression of CD11b, CD4, CD14, and CD68 for M0; IL-6, HLA/DRA, and CXCL10 for M21, and IL-10, CD163, fibronectin-1 or FN1, and CCL17 was evaluated by qPCR at 2 and 24 h after infection. Results: An increase in the expression of these molecules was induced by all serotypes at both times of infection, showing higher levels of expression to the M1 panel at 2 and 24 h compared to other markers. Conclusions: A. actinomycetemcomitans has a role in the macrophage polarization to the M1 phenotype in a non-serotype-dependent manner.

Connecting the Human Microbiome and Pancreatic Cancer

Pancreatic cancer is a deadly disease that is increasing in incidence throughout the world. There are no clear causal factors associated with the incidence of pancreatic cancer; however, some correlation to smoking, diabetes and alcohol has been described. Recently, a few studies have linked the human microbiome (oral and gastrointestinal tract) to pancreatic cancer development. A perturbed microbiome has been shown to alter normal cells while promoting cancer-related processes such as increased cell signaling, immune system evasion and invasion. In this article, we will review in detail the alterations within the gut and oral microbiome that have been linked to pancreatic cancer and explore the ability of other microbiomes, such as the lung and skin microbiome, to contribute to disease development. Understanding ways to identify a perturbed microbiome can result in advancements in pancreatic cancer research and allow for prevention, earlier detection and alternative treatment strategies for patients.

Impact of Three Nonsurgical, Full-Mouth Periodontal Treatments on Total Bacterial Load and Selected Pathobionts

For the treatment of periodontitis stage III/IV, a quadrant/week-wise debridement (Q-SRP) was compared with three full-mouth approaches: full-mouth scaling (FMS, accelerated Q-SRP within 24 h), full-mouth scaling with chlorhexidine-based disinfection (FMD), and FMD with adjuvant erythritol air polishing (FMDAP). The objective of this prospective, randomized study (a substudy of ClinicalTrials.gov, identifier: NCT03509233) was to compare the clinical and microbiological effects of the treatments. In total, 105 patients were randomized to one of the four aforementioned treatment groups, with n = 25, 28, 27, and 25 patients allocated to each group, respectively. At baseline and 3 and 6 months after treatment, the clinical parameters, including the pocket probing depths, clinical attachment level, and bleeding on probing, were recorded, and the prevalence of the total bacteria and four periodontal pathobionts (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, and Tannerella forsythia) was determined using real-time quantitative PCR. Concerning the clinical outcomes, all the treatment modalities were effective, but the full-mouth approaches, especially FMDAP, were slightly superior to Q-SRP. Using the FMD approach, the reduction in the bacterial load and the number of pathobionts was significantly greater than for FMS, followed by Q-SRP. FMDAP was the least effective protocol for microbial reduction. However, after a temporary increase 3 months after therapy using FMDAP, a significant decrease in the key pathogen, P. gingivalis, was observed. These findings were not consistent with the clinical results from the FMDAP group. In conclusion, the dynamics of bacterial colonization do not necessarily correlate with clinical outcomes after full-mouth treatments for periodontitis stage III/IV.

Antiplanktonic and Antibiofilm Activity of Rheum palmatum against Streptococcus oralis and Porphyromonas gingivalis

Periodontitis and peri-implantitis are inflammatory conditions with a high global prevalence. Oral pathogens such as Porphyromonas gingivalis play a crucial role in the development of dysbiotic biofilms associated with both diseases. The aim of our study was to identify plant-derived substances which mainly inhibit the growth of "disease promoting bacteria", by comparing the effect of Rheum palmatum root extract against P. gingivalis and the commensal species Streptococcus oralis. Antiplanktonic activity was determined by measuring optical density and metabolic activity. Antibiofilm activity was quantified using metabolic activity assays and live/dead fluorescence staining combined with confocal laser scanning microscopy. At concentrations of 3.9 mg/L, R. palmatum root extract selectively inhibited planktonic growth of the oral pathogen P. gingivalis, while not inhibiting growth of S. oralis. Selective effects also occurred in mature biofilms, as P. gingivalis was significantly more stressed and inhibited than S. oralis. Our studies show that low concentrations of R. palmatum root extract specifically inhibit P. gingivalis growth, and offer a promising approach for the development of a potential topical agent to prevent alterations in the microbiome due to overgrowth of pathogenic P. gingivalis.

Adhesion of Oral Bacteria to Commercial d-PTFE Membranes: Polymer Microstructure Makes a Difference

Bacterial contamination of the membranes used during guided bone regeneration directly influences the outcome of this procedure. In this study, we analyzed the early stages of bacterial adhesion on two commercial dense polytetrafluoroethylene (d-PTFE) membranes in order to identify microstructural features that led to different adhesion strengths. The microstructure was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). The surface properties were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), and surface free energy (SFE) measurements. Bacterial properties were determined using the microbial adhesion to solvents (MATS) assay, and bacterial surface free energy (SFE) was measured spectrophotometrically. The adhesion of four species of oral bacteria (Streptococcus mutans, Streptococcus oralis, Aggregatibacter actinomycetemcomitas, and Veilonella parvula) was studied on surfaces with or without the artificial saliva coating. The results indicated that the degree of crystallinity (78.6% vs. 34.2%, with average crystallite size 50.54 nm vs. 32.86 nm) is the principal feature promoting the adhesion strength, through lower nanoscale roughness and possibly higher surface stiffness. The spherical crystallites ("warts"), observed on the surface of the highly crystalline sample, were also identified as a contributor. All bacterial species adhered better to a highly crystalline membrane (around 1 log10CFU/mL difference), both with and without artificial saliva coating. Our results show that the changes in polymer microstructure result in different antimicrobial properties even for chemically identical PTFE membranes.

Lactobacillus helveticus Prevents Periodontitis Induced by Aggregatibacter actinomycetemcomitans in Rats by Regulating β-Defensins

Objective

To study the preventive effect of Lactobacillus helveticus (L. helveticus) on periodontitis induced by Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) in rats.

Methods

Eighteen 8-week-old female rats were randomly divided into three groups: Sham group, Trehalose group, and L. helveticus SBT2171 (LH2171) group. We measured the distance of the cementoenamel junction-alveolar bone crest (CEJ-ABC) to evaluate alveolar bone resorption. Hematoxylin-eosin staining was used to observe the histopathological changes of rat hemimaxillary tissues. We detected the expression of β-defensins, tumor necrosis factor-α (TNF-α), interleukin- (IL-) 1β, and IL-6 and the number of A. actinomycetemcomitans in rat gingival tissues by quantitative reverse transcriptase polymerase chain reaction. The levels of IL-1β, IL-6, and TNF-α in rat gingival tissues were also measured by enzyme-linked immunosorbent assay.

Results

Compared with the Trehalose group, the distance of CEJ-ABC was prominently reduced and alveolar bone resorption was notably improved in the LH2171 group. And the infiltration of inflammatory cells in the hemimaxillary tissue decreased obviously, periodontal fibers were arranged neatly, connective tissue small blood vessels proliferated, and the number of A. actinomycetemcomitans reduced significantly in the LH2171 group. In addition, the mRNA expression and release of inflammatory factors in the gingival tissues in the LH2171 group were notably lower than those in the Trehalose group. On the 21st and 36th day, the expression of β-defensins in the gingival tissue of the LH2171 group increased significantly.

Conclusion

L. helveticus improves alveolar bone resorption and increases the expression of β-defensins thereby inhibiting the number of A. actinomycetemcomitans and thus prevents periodontitis.

Discrepancies in Antimicrobial Susceptibility between the JP2 and the Non-JP2 Genotype of Aggregatibacter actinomycetemcomitans

The Aggregatibacter actinomycetemcomitans JP2 genotype is associated with high leukotoxin production and severe (aggressive) periodontitis. The aim of this study was to compare the antimicrobial susceptibility of JP2 and non-JP2 genotype strains. Minimal inhibitory concentrations (MICs) of 11 antimicrobials were determined for 160 A. actinomycetemcomitans of serotype a, b, or c, mostly isolated in Sweden or Ghana. MIC distributions for benzylpenicillin and fusidic acid revealed a more susceptible subpopulation for 38 serotype b strains, including the 32 of the JP2 genotype, with a benzylpenicillin MIC range of 0.125−0.5 mg/L. In contrast, benzylpenicillin MIC ≤ 16 mg/L was the estimated 99.5% epidemiological cutoff (ECOFF) of all strains. Beta-lactamase production was not detected. The fusidic acid MIC distribution of 11 strains of Aggregatibacter aphrophilus agreed with that found in non-JP2 strains. Cefotaxime, meropenem, levofloxacin, and trimethoprim−sulfamethoxazole MICs were all ≤0.25 mg/L, while MIC90 values for amoxicillin, azithromycin and tetracycline were 1 mg/L. Metronidazole MICs varied between 0.5 and >256 mg/L. The discrepant findings indicate that A. actinomycetemcomitans may be divided into two separate wild types, with a suggested intrinsic reduced susceptibility for benzylpenicillin in the majority of non-JP2 genotype strains. Possible implications for the treatment of A. actinomycetemcomitans infections are discussed.

Engineered Delivery of Dental Stem-Cell-Derived Extracellular Vesicles for Periodontal Tissue Regeneration

Periodontal disease begins as an inflammatory response to a bacterial biofilm deposited around the teeth, which over time leads to the destruction of tooth-supporting structures and consequently tooth loss. Conventional treatment strategies show limited efficacy in promoting regeneration of damaged periodontal tissues. Here, a delivery platform is developed for small extracellular vesicles (sEVs) derived from gingival mesenchymal stem cells (GMSCs) to treat periodontitis. EVs can achieve comparable therapeutic effects to their cells of origin. However, the short half-lives of EVs after their administration along with their rapid diffusion away from the delivery site necessitate frequent administration to achieve therapeutic benefits. To address these issues, "dual delivery" microparticles are engineered enabling microenvironment-sensitive release of EVs by metalloproteinases at the affected site along with antibiotics to suppress bacterial biofilm growth. GMSC sEVs are able to decrease the secretion of pro-inflammatory cytokines by monocytes/macrophages and T cells, suppress T-cell activation, and induce the formation of T regulatory cells (Tregs) in vitro and in a rat model of periodontal disease. One-time administration of immunomodulatory GMSC sEV-decorated microparticles leads to a significant improvement in regeneration of the damaged periodontal tissue. This approach will have potential clinical applications in the regeneration of a variety of tissues.

Succession of oral bacterial colonizers on dental implant materials: An in vitro biofilm model

OBJECTIVES

Oral bacterial adhesion on dental implant materials has been extensively studied using in vitro systems but has yielded results restricted to in vitro growth patterns due to limitations in species selection, sustained fastidious anaerobe growth, and mixed culture longevity. The aim of this study was to develop an oral bacterial biofilm model consisting of colonizers representative of the oral microbiome exhibiting temporal shifts characteristic of plaque development and maturation in vivo.

METHODS

Streptococcus oralis, Actinomyces naeslundii, Aggregatibacter actinomycetemcomitans, Veillonella parvula, Fusobacterium nucleatum, and Porphyromonas gingivalis were grown in monoculture prior to combination in mixed culture. Commercially pure titanium (cpTi) and yttria-stabilized zirconia (ZrO2) disks with polished, acid-etched, or sandblasted surfaces were prepared to evaluate oral bacterial adhesion. After 6 h, 1, 3, 7, 14 and 21 days, genomic DNA from planktonic and adherent bacteria was isolated. Quantitative polymerase chain reaction (qPCR) was used to enumerate the amount and proportion of each species.

RESULTS

Early-colonizing S. oralis and A. actinomycetemcomitans, dominated after 6 h prior to secondary colonization by F. nucleatum and V. parvula in planktonic (1 day) and sessile (3 days) form. A. naeslundii maintained relatively low but stable bacterial counts throughout testing. After 14 days, late-colonizing P. gingivalis became established in mixed culture and persisted, becoming the dominant species after 21 days. The composition of adherent bacteria across all substrates was statistically similar at all timepoints with notable exceptions including lower S. oralis bacterial counts on polished cpTi (3 days).

SIGNIFICANCE

Within the present model's limitations, multispecies oral bacterial attachment is similar on surface-treated cpTi and ZrO2.

Treponema denticola as a prognostic biomarker for periodontitis in dogs

Periodontal disease is one of the most common disorders in the oral cavity of dogs and humans. Periodontitis, the irreversible periodontal disease, arises progressively from gingivitis, the reversible inflammatory condition caused by dental plaque. Although the etiology of periodontitis has been widely studied in humans, it is still insufficient for the etiological studies on periodontitis in dogs. Many studies have reported that human periodontitis-related bacteria are putative pathogens responsible for periodontitis in dogs. However, most of these studies have focused on the appearance of a specific microbiome, and most of the cohort studies have insufficient sample sizes to generalize their results. In the present study, subgingival samples collected from 336 teeth were categorized into three groups at first, based on clinical outcomes (healthy, gingivitis, periodontitis). Subsequently, the periodontitis samples were further divided into three subgroups (early, moderate, and advanced periodontitis) according to the degree of periodontal attachment loss. Healthy and gingivitis were grouped as a reversible group, and the three subgroups were grouped as an irreversible group. To investigate trends of periodontopathic bacteria in the samples of dogs, a quantitative real-time polymerase chain reaction (PCR) was performed for quantification of 11 human periodontopathic bacteria as follows: Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Tannerella forsythia, Treponema denticola (Td), Fusobacterium nucleatum, Prevotella nigrescens, Prevotella intermedia, Parvimonas micra, Eubacterium nodatum, Campylobacter rectus, and Eikenella corrodens. The PCR results showed that Aa and Pg, the representative periodontopathic bacteria, were not significantly correlated or associated with the periodontitis cases in dogs. However, interestingly, Td was strongly associated with the irreversible periodontal disease in dogs, in that it was the most prevalent bacterium detected from the dog samples. These findings indicate that the presence and numbers of Td could be used as a prognostic biomarker in predicting the irreversible periodontal disease and the disease severity in dogs.

Aggregatibacter actinomycetemcomitans as the Aetiological Cause of Rheumatoid Arthritis: What Are the Unsolved Puzzles?

Leukotoxin A (LtxA) is the major virulence factor of an oral bacterium known as Aggregatibacter actinomycetemcomitans (Aa). LtxA is associated with elevated levels of anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis (RA) patients. LtxA targets leukocytes and triggers an influx of extracellular calcium into cytosol. The current proposed model of LtxA-mediated hypercitrullination involves the dysregulated activation of peptidylarginine deiminase (PAD) enzymes to citrullinate proteins, the release of hypercitrullinated proteins through cell death, and the production of autoantigens recognized by ACPA. Although model-based evidence is yet to be established, its interaction with the host’s immune system sparked interest in the role of LtxA in RA. The first part of this review summarizes the current knowledge of Aa and LtxA. The next part highlights the findings of previous studies on the association of Aa or LtxA with RA aetiology. Finally, we discuss the unresolved aspects of the proposed link between LtxA of Aa and RA.