A new checkerboard panel for testing bacterial markers in periodontal disease

Association of F. alocis and D. pneumosintes with Periodontitis Disease Severity and Red Complex Bacteria

Oral biofilms are considered the principal etiological agent in the development of periodontitis. Novel species that may contribute to periodontitis and dysbiosis have been identified recently. The study aims to evaluate the presence of F. alocis and D. pneumosintes in healthy and diseased patients and their association with clinical parameters and with red complex bacteria. The study included 60 subjects, with 30 patients each in the healthy and periodontitis groups. The clinical parameters were noted, and samples were subjected to DNA extraction followed by a polymerase chain reaction. Statistical analysis was performed using the Graph Pad Prism software. Results: F. alocis and D. pneumosintes were detected at a significantly higher percentage in the periodontitis group compared to the healthy group (p < 0.05). D. pneumosintes was significantly associated with T. forsythia in the periodontitis group (p < 0.05). Both of these organisms were present in sites with higher clinical attachment loss (p < 0.05). This study demonstrated that both F. alocis and D. pneumosintes were detected at a significantly higher percentage in periodontitis subjects and were detected more frequently in sites with a greater clinical attachment loss. It was also evident that both F. alocis and D. pneumosintes can be present independently of other putative periodontal pathogens.

Evaluation of Sterify Gel as an Adjunctive Treatment to Scaling and Root Planing in Promoting Healing of Periodontal Pockets: A Split-Mouth Randomized Controlled Trial

Background

Periodontal disease is a common infectious disease that leads to the destruction of tooth-supporting structures. Current treatments, such as scaling and root planing (SRP), have limitations in deep and complex pockets, and antibiotic use carries the risk of resistance. Sterify Gel, a medical device composed of polyvinyl polymers, hydroxytyrosol, nisin, and magnesium ascorbyl phosphate, offers a new approach to periodontal care. This study aims to evaluate the safety and efficacy of Sterify Gel as an adjunctive treatment to SRP in promoting the healing of periodontal pockets.

Methods

The study includes 34 patients with moderate to advanced chronic periodontal disease. Randomization assigned one site for SRP alone (control) and the other site for SRP with Sterify Gel (treatment). Periodontal parameters were evaluated at baseline, 1, 2, and 3 months after treatment bacterial contamination was assessed through quantitative PCR at baseline and 3 months after treatment. Statistical analysis was conducted using ANOVA and Wilcoxon test.

Results

Treatment with Sterify Gel and SRP demonstrated significant improvements in pocket depth, gingival recession, and clinical attachment level compared with SRP alone. Bleeding and plaque indexes, pain perception, tooth mobility, and furcations showed no significant differences between the two groups. The treatment group showed a reduction in bacterial contamination at 3 months.

Conclusions

Sterify Gel in combination with SRP shows the potential for improving periodontal health by promoting healing and reducing periodontal pockets. It may offer benefits in preventing bacterial recolonization and reducing reliance on antibiotics.

Microbial biomarkers as a predictor of periodontal treatment response: A systematic review

To evaluate the prognostic accuracy of microbial biomarkers and their associations with the response to active periodontal treatment (APT) and supportive periodontal therapy (SPT). Microbial dysbiosis plays a crucial role in the disease processes of periodontitis. Biomarkers based on microbial composition may offer additional prognostic value, supplementing the limitations of current clinical parameters. While these microbial biomarkers have been clinically evaluated, there is a lack of consensus regarding their prognostic accuracy. A structured search strategy was applied to MEDLINE (PubMed), Cochrane Library, and Embase on 1/11/2022 to identify relevant publications. Prospective clinical studies involving either APT or SPT, with at least 3-month follow-up were included. There were no restrictions on the type of microbial compositional analysis. 1918 unique records were retrieved, and 13 studies (comprising 943 adult patients) were included. Heterogeneity of the studies precluded a meta-analysis, and none of the included studies had performed the sequence analysis of the periodontal microbiome. Seven and six studies reported on response to APT and SPT, respectively. The prognostic accuracy of the microbial biomarkers for APT and SPT was examined in only two and four studies, respectively. Microbial biomarkers had limited predictive accuracy for APT and inconsistent associations for different species across studies. For SPT, elevated abundance of periodontal pathogens at the start of SPT was predictive of subsequent periodontal progression. Similarly, persistent high pathogen loads were consistently associated with progressive periodontitis, defined as an increased pocket probing depth or clinical attachment loss. While there was insufficient evidence to support the clinical use of microbial biomarkers as prognostic tools for active periodontal treatment outcomes, biomarkers that quantify periodontal pathogen loads may offer prognostic value for predicting progressive periodontitis in the subsequent supportive periodontal therapy phase. Additional research will be required to translate information regarding subgingival biofilm composition and phenotype into clinically relevant prognostic tools.

Quantitative investigation of the bacterial content of periodontal abscess samples by real-time PCR

OBJECTIVES

Periodontal abscesses, which are part of the acute periodontal disease group characterized by the destruction of periodontal tissue with deep periodontal pockets, bleeding on probing, suppuration, and localized pus accumulation, cause rapid destruction of tooth-supporting tissues. This study aimed to evaluate the microbial content of periodontal abscesses by specific and culture-independent qPCR.

METHODS

This study was conducted on 30 volunteers diagnosed with periodontal abscesses and presenting with complaints of localized pain, swelling, and tenderness in the gingiva. Genomic DNA was isolated from the samples taken. Escherichia coli bacteria were used for the standard curve created to calculate the prevalence of target bacteria in the total bacterial load. 16S rRNA Universal primers were used to assess the total bacterial load and prevalence. Bacterial counts were analyzed with Spearman's rank correlation coefficients (ρ) matrix.

RESULTS

From the analysis of Real-Time PCR, Porphyromonas gingivalis (30, 100%), Prevotella intermedia (30, 100%), and Fusobacterium nucleatum (30, 100%) were detected in all samples. Campylobacter rectus (29, 96.6%), Porphyromonas endodontalis (29, 96.6%), Tannerella forsythia (28, 93.3%), Filifactor alocis (28, 93.3%), and Actinomyces naeslundii (28, 93.3%) were also frequently detected.

CONCLUSIONS

Periodontal abscesses were found to be polymicrobial, and not only periodontal pathogens appeared to be associated with the development of periodontal abscesses. The presence, prevalence, and number of Porphyromonas endodontalis and Propionibacterium acnes in the contents of periodontal abscesses were determined for the first time in our study. Further studies are needed to better understand the roles of bacteria in periodontal disease, including abscesses.

Selenomonas sputigena Interactions with Gingival Epithelial Cells That Promote Inflammation

Increased prevalence and abundance of Selenomonas sputigena have been associated with periodontitis, a chronic inflammatory disease of tooth-supporting tissues, for more than 50 years. Over the past decade, molecular surveys of periodontal disease using 16S and shotgun metagenomic sequencing approaches have confirmed the disease association of classically recognized periodontal pathogens such as Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia while highlighting previously underappreciated organisms such as Filifactor alocis and S. sputigena. Despite abundant clinical association between S. sputigena and periodontal disease, we have little to no understanding of its pathogenic potential, and virulence mechanisms have not been studied. In this study, we sought to characterize the response of gingival epithelial cells to infection with S. sputigena. Here, we show that S. sputigena attaches to gingival keratinocytes and induces expression and secretion of cytokines and chemokines associated with inflammation and leukocyte recruitment. We demonstrate that S. sputigena induces signaling through Toll-like receptor 2 (TLR2) and TLR4 but evades activation of TLR5. Cytokines released from S. sputigena-infected keratinocytes induced monocyte and neutrophil chemotaxis. These results show that S. sputigena-host interactions have the potential to contribute to bacterially driven inflammation and tissue destruction, the hallmark of periodontitis. Characterization of previously unstudied pathogens may provide novel approaches to develop therapeutics to treat or prevent periodontal disease.

Multiomics Analysis Reveals the Impact of Microbiota on Host Metabolism in Hepatic Steatosis

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a complex disease involving alterations in multiple biological processes regulated by the interactions between obesity, genetic background, and environmental factors including the microbiome. To decipher hepatic steatosis (HS) pathogenesis by excluding critical confounding factors including genetic variants and diabetes, 56 heterogenous MAFLD patients are characterized by generating multiomics data including oral and gut metagenomics as well as plasma metabolomics and inflammatory proteomics data. The dysbiosis in the oral and gut microbiome is explored and the host-microbiome interactions based on global metabolic and inflammatory processes are revealed. These multiomics data are integrated using the biological network and HS's key features are identified using multiomics data. HS is finally predicted using these key features and findings are validated in a follow-up cohort, where 22 subjects with varying degree of HS are characterized.

Micromonas micros: A rare anaerobic cause of late implant failure following spinal surgery

Context: Delayed, postoperative, spine infections are rare, most commonly occurring secondary to fastidious, less virulent pathogens. The etiology may involve a distant infectious focus, not related to the index operation. Patients may present months, or even years postoperatively with pain related to mechanical implant failure, often without additional signs of systemic infection.Findings: We present the case of a 59-year-old male who developed rapid disk degeneration and implant failure seven months following instrumented lumbar fusion surgery. The causal organism was found to be Micromonas micros, an anaerobic bacterium typically located in the oral cavity and associated with periodontal disease. The patient was found to have extensive oral caries, which were presumed to have occurred secondary to poor oral hygiene and his use of fentanyl lozenges for chronic back pain. The patient was treated with revision staged spinal surgery and long-term intravenous antibiotics.Conclusion/clinical relevance: This case highlights an unusual etiology of delayed postoperative spinal implant failure and provides evidence for periodontal disease as a source of hematogenous seeding in postoperative spinal infections. The orthopaedist should also be aware of the potential relationship between poor oral hygiene and the use of high sugar content fentanyl lozenges in treating chronic back pain in these patients.

Role of the Filifactor alocis Hypothetical Protein FA519 in Oxidative Stress Resistance

In the periodontal pocket, there is a direct correlation between environmental conditions, the dynamic oral microbial flora, and disease. The relative abundance of several newly recognized microbial species in the oral microenvironment has raised questions on their impact on disease development. One such organism, Filifactor alocis, is significant to the pathogenic biofilm structure. Moreover, its pathogenic characteristics are highlighted by its ability to survive in the oxidative-stress microenvironment of the periodontal pocket and alter the microbial community dynamics. There is a gap in our understanding of its mechanism(s) of oxidative stress resistance and impact on pathogenicity. Several proteins, including HMPRFF0389-00519 (FA519), were observed in high abundance in F. alocis during coinfection of epithelial cells with Porphyromonas gingivalis W83. Bioinformatics analysis shows that FA519 contains a "Cys-X-X-Cys zinc ribbon domain" which could be involved in DNA binding and oxidative stress resistance. We have characterized FA519 to elucidate its roles in the oxidative stress resistance and virulence of F. alocis. Compared to the wild-type strain, the F. alocis isogenic gene deletion mutant, FLL1013 (ΔFA519::ermF), showed significantly reduced sensitivity to hydrogen peroxide and nitric oxide-induced stress. The ability to form biofilm and adhere to and invade gingival epithelial cells was also reduced in the isogenic mutant. The recombinant FA519 protein was shown to protect DNA from Fenton-mediated damage with an intrinsic ability to reduce hydrogen peroxide and disulfide bonds. Collectively, these results suggest that FA519 is involved in oxidative stress resistance and can modulate important virulence attributes in F. alocis. IMPORTANCE Filifactor alocis is an emerging member of the periodontal community and is now proposed to be a diagnostic indicator of periodontal disease. However, due to the lack of genetic tools available to study this organism, not much is known about its virulence attributes. The mechanism(s) of oxidative stress resistance in F. alocis is unknown. Therefore, identifying the adaptive mechanisms utilized by F. alocis to survive in the oxidative stress environment of the periodontal pocket would lead to understanding its virulence regulation, which could help develop novel therapeutic treatments to combat the effects of periodontal disease. This study is focused on the characterization of FA519, a hypothetical protein in F. alocis, as a multifunctional protein that plays an important role in the reactive oxygen species-detoxification pathway. Collectively, our results suggest that FA519 is involved in oxidative stress resistance and can modulate important virulence attributes in F. alocis.

The Varied Proportion of Filifactor alocis in Periodontal Health and Disease in the South Indian Subpopulation

BACKGROUND AND AIM

The periodontal microbiome being complex, this study was aimed to detect and quantify the prevalence of Filifactor alocis in various stages of periodontitis and to evaluate its prospect as a diagnostic marker for periodontal disease.

SETTINGS AND DESIGN

Sixty subjects were selected (20 healthy controls, 20 with chronic periodontitis, and 20 with aggressive periodontitis) for the study.

MATERIALS AND METHODS

Clinical parameters probing depth and the level of clinical attachment was recorded, subgingival plaque samples were collected. The F. alocis 16srDNA was cloned, sequenced, and used as the standard for real-time quantification of bacterial load using SYBR green chemistry.

STATISTICAL ANALYSIS

Clinical, microbiological, and quantitative polymerase chain reaction (PCR) data were analyzed using ANOVA and Pearson's coefficient correlation.

RESULTS

(a) Real-time PCR analysis showed the highest average F. alocis count in chronic periodontitis subjects (32,409.85), which was followed by count in healthy controls (3046.15) and the least count in aggressive periodontitis subjects (939.84). The bacterial count was statistically significant at P = 0.005. (b) An intra-group comparison reveals that there was a statistically significant increase in the bacterial count with age and mean probing pocket depth at P = 0.0005.

CONCLUSION

F. alocis population in aggressive periodontitis was lower compared to chronic periodontitis and healthy controls. The F. alocis population surge in healthy controls may be due to geographical variations and the ethnicity of the subjects. A higher population of F. alocis in chronic periodontitis proves its high pathogenic potential to invade the host tissues to aid in further periodontal destruction.

Role of Superoxide Reductase FA796 in Oxidative Stress Resistance in Filifactor alocis

Filifactor alocis, a Gram-positive anaerobic bacterium, is now a proposed diagnostic indicator of periodontal disease. Because the stress response of this bacterium to the oxidative environment of the periodontal pocket may impact its pathogenicity, an understanding of its oxidative stress resistance strategy is vital. Interrogation of the F. alocis genome identified the HMPREF0389_00796 gene that encodes for a putative superoxide reductase (SOR) enzyme. SORs are non-heme, iron-containing enzymes that can catalyze the reduction of superoxide radicals to hydrogen peroxide and are important in the protection against oxidative stress. In this study, we have functionally characterized the putative SOR (FA796) from F. alocis ATCC 35896. The recombinant FA796 protein, which is predicted to be a homotetramer of the 1Fe-SOR class, can reduce superoxide radicals. F. alocis FLL141 (∆FA796::ermF) was significantly more sensitive to oxygen/air exposure compared to the parent strain. Sensitivity correlated with the level of intracellular superoxide radicals. Additionally, the FA796-defective mutant had increased sensitivity to hydrogen peroxide-induced stress, was inhibited in its ability to form biofilm and had reduced survival in epithelial cells. Collectively, these results suggest that the F. alocis SOR protein is a key enzymatic scavenger of superoxide radicals and protects the bacterium from oxidative stress conditions.

Periodontal status, vascular reactivity, and platelet aggregation changes in rats submitted to hypercholesterolemic diet and periodontitis

BACKGROUND AND OBJECTIVES

Periodontitis can corroborate with development and progression of atherosclerosis and a possible bidirectional interaction between both pathologies has been hypothesized. The aim of this work was to study the interactions between diet-induced hypercholesterolemia and ligature-induced periodontitis in Wistar rats submitted to both conditions.

MATERIAL AND METHODS

Animals were divided into four experimental groups: C (control: standard diet without periodontitis), Perio (periodontitis plus standard diet), HC (high cholesterol diet without periodontitis), and HC + Perio (high cholesterol diet plus periodontitis). The diets were offered for 45 days and a silk ligature was applied in the lower first molars of Perio and HC-Perio animals on day 34 and maintained for 11 days until euthanasia. The mandibles were excised, and alveolar bone loss was determined by macroscopic and micro-tomographic (µ-CT) imaging. Blood samples were obtained, and platelet aggregation was induced in plasma rich in platelets by adenosine diphosphate (ADP) and collagen. Endothelium-dependent vascular reactivity and protein expression of endothelial (eNOS), phosphorylated endothelial (peNOS), and inducible (iNOS) nitric oxide synthases were evaluated in aorta samples.

RESULTS

The HC diet combined with periodontitis (HC + Perio group) was associated with an increased alveolar bone loss, when compared to the other groups. Both in Perio and HC groups, platelet aggregation induced by ADP or collagen was increased, while maximum aortic relaxation induced by acetylcholine was decreased. Periodontitis or HC diet alone decreased the expression of peNOS and HC diet increased the expression of iNOS. In contrast, no additive or synergistic effects were found in vascular reactivity or in platelet aggregation when the two conditions were associated (HC + Perio group).

CONCLUSION

Hypercholesterolemia accelerated the process of bone loss induced by periodontitis while a high cholesterol diet or periodontitis individually increased platelet aggregation and vascular reactivity in rats without additive or synergistic effects, when associated.

Putative Periodontal Pathogens, Filifactor Alocis and Peptoanaerobacter Stomatis, Induce Differential Cytokine and Chemokine Production by Human Neutrophils

Periodontitis is a highly prevalent infectious disease that affects ~ 50% of the adults in the USA alone. Two Gram-positive anaerobic oral bacteria, Filifactor alocis and Peptoanaerobacterstomatis, have emerged as important periodontal pathogens. Neutrophils are a major component of the innate host response in the gingival tissue, and the contribution of neutrophil-derived cytokines and chemokines plays a central role in disease progression. The pattern of cytokines and chemokines released by human neutrophils upon stimulation with newly appreciated periodontal bacteria compared to the keystone oral pathogen Porphyromonas gingivalis was investigated. Our results showed that both F. alocis and P. stomatis triggered TLR2/6 activation. F. alocis induced significant changes in gene expression of cytokines and chemokines in human neutrophils compared to unstimulated cells. However, except for IL-1ra, neutrophils released lower levels of cytokines and chemokines in response to F. alocis compared to P. stomatis. Furthermore, bacteria-free conditioned supernatant collected from neutrophils challenged with P. stomatis, but not from P. gingivalis or F. alocis, was chemotactic towards both neutrophils and monocytes. Elucidating stimuli-specific modulation of human neutrophil effector functions in the context of dysbiotic microbial community constituents provides valuable information for understanding the pathogenesis of periodontal diseases.

The interplay between oral microbiome, lifestyle factors and genetic polymorphisms in the risk of oral squamous cell carcinoma

Poor oral hygiene may lead to overgrowth of pathogenic oral bacteria, which may induce chronic inflammation to promote the oncogenesis of oral squamous cell carcinoma (OSCC). This study investigated the association between oral bacterial profile and OSCC risk in a case-control study of 138 OSCC cases and 151 controls (88 cases and 90 controls for the discovery group and 50 cases and 61 controls for the validation group). Oral bacterial profiles were characterized by targeted sequencing of the 16S rRNA gene. Three species of periodontopathogenic bacteria, Prevotella tannerae, Fusobacterium nucleatum, and Prevotella intermedia, were associated with an increased OSCC risk. This association was modified by the genetic polymorphisms of TLR2 and TLR4. Use of alcohol, betel quids and cigarettes and poor oral hygiene were associated with a higher percentage of oral periodontopathogenic bacteria. The association between alcohol and periodontopathogenic bacteria was modified by the genetic polymorphism of ALDH2, with a stronger positive association observed among the ALDH2-deficient individuals. The percentage of periodontopathogenic bacteria was positively correlated with the level of salivary IL1β, an inflammatory cytokine. Overall, our results showed a positive association between periodontopathogenic bacteria and OSCC risk and this relationship may be influenced by lifestyle and genetic factors. Our results provided further biological support for the established association between poor oral hygiene and OSCC risk. This suggested that improving oral hygiene may reduce OSCC risk and should be part of a public health campaign to prevent the occurrence of OSCC.

Neutrophil Interaction with Emerging Oral Pathogens: A Novel View of the Disease Paradigm

Periodontitis is a multifactorial chronic inflammatory infectious disease that compromises the integrity of tooth-supporting tissues. The disease progression depends on the disruption of host-microbe homeostasis in the periodontal tissue. This disruption is marked by a shift in the composition of the polymicrobial oral community from a symbiotic to a dysbiotic, more complex community that is capable of evading killing while promoting inflammation. Neutrophils are the main phagocytic cell in the periodontal pocket, and the outcome of the interaction with the oral microbiota is an important determinant of oral health. Novel culture-independent techniques have facilitated the identification of new bacterial species at periodontal lesions and induced a reappraisal of the microbial etiology of periodontitis. In this chapter, we discuss how neutrophils interact with two emerging oral pathogens, Filifactor alocis and Peptoanaerobacter stomatis, and the different strategies deploy by these organisms to modulate neutrophil effector functions, with the goal to outline a new paradigm in our knowledge about neutrophil responses to putative periodontal pathogens and their contribution to disease progression.

Filifactor alocis modulates human neutrophil antimicrobial functional responses

Filifactor alocis is a newly appreciated pathogen in periodontal diseases. Neutrophils are the predominant innate immune cell in the gingival crevice. In this study, we examined modulation of human neutrophil antimicrobial functions by F. alocis. Both non-opsonised and serum-opsonised F. alocis were engulfed by neutrophils but were not efficiently eliminated. Challenge of neutrophils with either non-opsonised or serum-opsonised F. alocis induced a minimal intracellular as well as extracellular respiratory burst response compared to opsonised Staphylococcus aureus and fMLF, respectively. However, pretreatment or simultaneous challenge of neutrophils with F. alocis did not affect the subsequent oxidative response to a particulate stimulus, suggesting that the inability to trigger the respiratory response was only localised to F. alocis phagosomes. In addition, although neutrophils engulfed live or heat-killed F. alocis with the same efficiency, heat-killed F. alocis elicited a higher intracellular respiratory burst response compared to viable organisms, along with decreased surface expression of CD35, a marker of secretory vesicles. F. alocis phagosomes remained immature by delayed and reduced recruitment of specific and azurophil granules, respectively. These results suggest that F. alocis withstands neutrophil antimicrobial responses by preventing intracellular ROS production, along with specific and azurophil granule recruitment to the bacterial phagosome.

Caries and Periodontitis: Contesting the Conventional Wisdom on Their Aetiology

We review the literature on the oral microbiome and the role of the microbiota in the development of dental caries and periodontitis. While most research has been focused on identifying one or more specific determinants of these diseases, the results have provided limited predictive value and have not been able to explain the variation in the distribution of these diseases observed in epidemiological or clinical studies. Drawing on existing knowledge about the nature of the oral microbiota, we suggest that a stochastic model based on the Weiner process provides simple and parsimonious explanations for the pathogenesis of both caries and periodontitis, making few assumptions, and providing explanations for phenomena that have hitherto proved difficult, or have required complex arguments, to explain. These diseases occur as the result of the dental hard tissues and periodontal tissues integrating the random "noise" caused by normal metabolic activities of commensal microorganisms in the dental biofilm. The processes that result in the progression and regression of caries and periodontitis may be considered as "natural," rather than pathological, even if, when left unchecked over long periods of time, they can result in the development of pathologies. The likelihood of progression or regression can be influenced by other determinants, but these processes will nevertheless occur in the absence of such influences. The distributional characteristics of the model approximate the findings of epidemiological studies indicating that, for both caries and periodontitis, there will be few sites affected in the early period after the eruption of the permanent dentition, but in those older there is an almost linear relationship with increasing age; furthermore, the longer a site survives without being affected, the less likely that it will be affected. We discuss the clinical and public health importance of these findings.

Filifactor alocis manipulates human neutrophils affecting their ability to release neutrophil extracellular traps induced by PMA

Neutrophils operate at the site of injury or inflammation in the periodontal pocket to ensure periodontal health and clearance of bacterial pathogens. Filifactor alocis is recently identified as a potential periodontal pathogen, and in this study, we assessed the formation of neutrophil extracellular traps (NETs), in response to the presence of the organism. NET formation by human neutrophils was not induced when challenged with F. alocis, independent of opsonization, viability, time, or bacterial dose. F. alocis also failed to induce NETs from TNF-α-primed neutrophils and did not induce the release of extracellular neutrophil elastase. However, significant NET induction was observed when neutrophils were challenged with Streptococcus gordonii or Peptoanaerobacter stomatis, In addition, co-infection studies revealed that the presence of F. alocis with S. gordonii or P. stomatis does not enhance or reduce NETs. Additionally, F. alocis failed to impact pre-formed NETs induced by either S. gordonii or P. stomatis. Pretreatment with F. alocis prior to stimulation with phorbol 12-myristate 13-acetate (PMA), S. gordonii, or P. stomatis revealed that the bacterium is capable of reducing only PMA but not S. gordonii or P. stomatis NET formation. These results indicate that F. alocis manipulates neutrophils, inhibiting the triggering of NET induction.

The oral microbiome-the relevant reservoir for acute pediatric appendicitis?

PURPOSE

The oral microbiome has been related to numerous extra oral diseases. Recent studies detected a high abundance of oral bacteria in inflamed appendices in pediatric patients. To elucidate the role of oral bacteria in acute pediatric appendicitis, we studied the oral and appendiceal microbiome of affected children compared to healthy controls.

METHODS

Between January and June 2015, 21 children undergoing appendectomy for acute appendicitis and 28 healthy controls were prospectively enrolled in the study. All individuals underwent thorough dental examination and laboratory for inflammatory parameters. Samples of inflamed appendices and the gingival sulcus were taken for 16S rDNA sequencing. RT-qPCR of Fusobacterium nucleatum, Peptostreptococcus stomatis, and Eikenella corrodens was performed and their viability was tested under acidic conditions to mimic gastric transfer.

RESULTS

In phlegmonous appendices, Bacteroidetes and Porphyromonas were discovered as dominant phylum and genus. In sulcus samples, Firmicutes and Streptococcus were detected predominantly. P. stomatis, E. corrodens, and F. nucleatum were identified in each group. Viable amounts of P. stomatis were increased in sulci of children with acute appendicitis compared to sulci of healthy controls. In inflamed appendices, viable amounts of E. corrodens and F. nucleatum were decreased compared to sulci of children with appendicitis. Postprandial viability could be demonstrated for all tested bacteria.

CONCLUSION

In children with acute appendicitis, we identified several oral bacterial pathogens. Based on postprandial viability of selected species, a viable migration from the oral cavity through the stomach to the appendix seems possible. Thus, the oral cavity could be a relevant reservoir for acute appendicitis.

Exploring the microbiome in health and disease

The analysis of human microbiome is an exciting and rapidly expanding field of research. In the past decade, the biological relevance of the microbiome for human health has become evident. Microbiome comprises a complex collection of microorganisms, with their genes and metabolites, colonizing different body niches. It is now well known that the microbiome interacts with its host, assisting in the bioconversion of nutrients and detoxification, supporting immunity, protecting against pathogenic microbes, and maintaining health. Remarkable new findings showed that our microbiome not only primarily affects the health and function of the gastrointestinal tract but also has a strong influence on general body health through its close interaction with the nervous system and the lung. Therefore, a perfect and sensitive balanced interaction of microbes with the host is required for a healthy body. In fact, growing evidence suggests that the dynamics and function of the indigenous microbiota can be influenced by many factors, including genetics, diet, age, and toxicological agents like cigarette smoke, environmental contaminants, and drugs. The disruption of this balance, that is called dysbiosis, is associated with a plethora of diseases, including metabolic diseases, inflammatory bowel disease, chronic obstructive pulmonary disease, periodontitis, skin diseases, and neurological disorders. The importance of the host microbiome for the human health has also led to the emergence of novel therapeutic approaches focused on the intentional manipulation of the microbiota, either by restoring missing functions or eliminating harmful roles. In the present review, we outline recent studies devoted to elucidate not only the role of microbiome in health conditions and the possible link with various types of diseases but also the influence of various toxicological factors on the microbial composition and function.

Association of three putative periodontal pathogens with chronic periodontitis in Brazilian subjects

Objective

The aim of this study was to evaluate the association of Porphyromonas endodontalis, Filifactor alocis and Dialister pneumosintes with the occurrence of periodontitis.

Material and Methods

Thirty subjects with chronic periodontitis (ChP) and 10 with periodontal health (PH) were included in the study. Nine subgingival biofilm samples were collected as follows: i) PH group - from the mesial/buccal aspect of each tooth in two randomly chosen contralateral quadrants; ii) ChP group - from three sites in each of the following probing depth (PD) categories: shallow (≤3 mm), moderate (4-6 mm) and deep (≥7 mm). Checkerboard DNA-DNA hybridization was used to analyze the samples.

Results

We found the three species evaluated in a higher percentage of sites and at higher levels in the group with ChP than in the PH group (p<0.05, Mann-Whitney test). We also observed these differences when the samples from sites with PD≤4 mm or ≥5 mm of subjects with ChP were compared with those from subjects with PH (p<0.05, Mann-Whitney test). In addition, the prevalence and levels of D. pneumosintes, and especially of F. alocis were very low in healthy subjects (0.12x10⁵ and 0.01x10⁵, respectively).

Conclusion

F. alocis and D. pneumosintes might be associated with the etiology of ChP, and their role in the onset and progression of this infection should be further investigated. The role of P. endodontalis was less evident, since this species was found in relatively high levels and prevalence in the PH group.

Filifactor alocis Promotes Neutrophil Degranulation and Chemotactic Activity

Filifactor alocis is a recently recognized periodontal pathogen; however, little is known regarding its interactions with the immune system. As the first-responder phagocytic cells, neutrophils are recruited in large numbers to the periodontal pocket, where they play a crucial role in the innate defense of the periodontium. Thus, in order to colonize, successful periodontal pathogens must devise means to interfere with neutrophil chemotaxis and activation. In this study, we assessed major neutrophil functions, including degranulation and cell migration, associated with the p38 mitogen-activated protein kinase (MAPK) signaling pathway upon challenge with F. alocis. Under conditions lacking a chemotactic gradient, F. alocis-challenged neutrophils had increased migration compared to uninfected cells, indicating that F. alocis increases chemokinesis in human neutrophils. In addition, neutrophil chemotaxis induced by interleukin-8 was significantly enhanced when cells were challenged with F. alocis, compared to noninfected cells. Similar to live bacteria, heat-killed F. alocis induced both random and directed migration of human neutrophils. The interaction of F. alocis with Toll-like receptor 2 induced granule exocytosis along with a transient ERK1/2 and sustained p38 MAPK activation. Moreover, F. alocis-induced secretory vesicle and specific granule exocytosis were p38 MAPK dependent. Blocking neutrophil degranulation with TAT-SNAP23 fusion protein significantly reduced the chemotactic and random migration induced by F. alocis Therefore, we propose that induction of random migration by F. alocis will prolong neutrophil traffic time in the gingival tissue, and subsequent degranulation will contribute to tissue damage.

In Situ Anabolic Activity of Periodontal Pathogens Porphyromonas gingivalis and Filifactor alocis in Chronic Periodontitis

Porphyromonas gingivalis and Filifactor alocis are fastidious anaerobic bacteria strongly associated with chronic forms of periodontitis. Our understanding of the growth activities of these microorganisms in situ is very limited. Previous studies have shown that copy numbers of ribosomal-RNA precursor (pre-rRNA) of specific pathogen species relative to genomic-DNA (gDNA) of the same species (P:G ratios) are greater in actively growing bacterial cells than in resting cells. The method, so-called steady-state pre-rRNA-analysis, represents a novel culture-independent approach to study bacteria. This study employed this technique to examine the in situ growth activities of oral bacteria in periodontitis before and after non-surgical periodontal therapy. Sub-gingival paper-point samples were taken at initial and re-evaluation appointments. Pre-rRNA and gDNA levels of P. gingivalis and F. alocis were quantified and compared using reverse-transcriptase qPCR. The results indicate significantly reduced growth activity of P. gingivalis, but not F. alocis, after therapy. The P:G ratios of P. gingivalis and F. alocis were compared and a low-strength, but statistically significant inter-species correlation was detected. Our study demonstrates that steady-state pre-rRNA-analysis can be a valuable culture-independent approach to studying opportunistic bacteria in periodontitis.

Human neutrophils and oral microbiota: a constant tug-of-war between a harmonious and a discordant coexistence

Neutrophils are a major component of the innate host response, and the outcome of the interaction between the oral microbiota and neutrophils is a key determinant of oral health status. The composition of the oral microbiome is very complex and different in health and disease. Neutrophils are constantly recruited to the oral cavity, and their protective role is highlighted in cases where their number or functional responses are impeded, resulting in different forms of periodontal disease. Periodontitis, one of the more severe and irreversible forms of periodontal disease, is a microbial-induced chronic inflammatory disease that affects the gingival tissues supporting the tooth. This chronic inflammatory disease is the result of a shift of the oral bacterial symbiotic community to a dysbiotic more complex community. Chronic inflammatory infectious diseases such as periodontitis can occur because the pathogens are able to evade or disable the innate immune system. In this review, we discuss how human neutrophils interact with both the symbiotic and the dysbiotic oral community; an understanding of which is essential to increase our knowledge of the periodontal disease process.

Probiotic supplements and debridement of peri-implant mucositis: a randomized controlled trial

OBJECTIVE

The aim of this double-blind randomized placebo-controlled trial was to evaluate the effects of probiotic supplements in adjunct to conventional management of peri-implant mucositis.

MATERIALS AND METHODS

Forty-nine adult patients with peri-implant mucositis were consecutively recruited after informed consent. After initial mechanical debridement and oral hygiene instructions, the patients received a topical oil application (active or placebo) followed by twice-daily intake of lozenges (active or placebo) for 3 months. The active products contained a mix of two strains of Lactobacillus reuteri. Patients were clinically monitored and sampled at baseline and after 1, 2, 4, 12 and 26 weeks. The clinical end-points were pocket-probing depth (PPD), plaque index (PI) and bleeding on probing (BOP). In addition, the subgingival microbiota was processed with checkerboard DNA-DNA hybridization and samples of gingival crevicular fluid (GCF) were analyzed for selected cytokines with the aid of multiplex immunoassays.

RESULTS

After 4 and 12 weeks, all clinical parameters were improved in both the test and the placebo group. PPD and BOP were significantly reduced compared with baseline (p < 0.05), but no significant differences were displayed between the groups. The clinical improvements persisted 3 months after the intervention. No major alterations of the subgingival microflora were disclosed and the levels of inflammatory mediators in GCF did not differ between the groups.

CONCLUSIONS

Mechanical debridement and oral hygiene reinforcement resulted in clinical improvement of peri-implant mucositis and a reduction in cytokine levels. Probiotic supplements did not provide added benefit to placebo.

Periodontal disease in a remote Asian population: association between clinical and microbiological parameters

OBJECTIVE

The aim was to clinically and microbiologically describe the periodontal conditions in a remote adult Asian population with poor oral hygiene.

METHODS

The subjects were 30-60-year-old adults of Karen Hill tribes with no access to dental care. Eighty-six subjects were selected randomly. Clinical registrations included number of remaining teeth, plaque index (PlI), bleeding on probing (BoP), clinical attachment loss (CAL), and probing pocket depth (PPD). Subgingival plaque samples were collected and analyzed with the checkerboard method.

RESULTS

Subjects of the study group had mean number of remaining teeth of 26.5 despite the abundant plaque and a high bleeding score. Severe periodontitis (CAL ≥ 7 mm) was recorded in 12.9% of the youngest age group (30-39 years) while it was significantly higher (52%) in the middle group (40-49 years) and (60%) in the eldest age group (50-60 years). Pathological pocketing (PPD ≥ 7 mm) was significantly lower in all age groups. Age, betel chewing, and a microbiological cluster including at least one of Prevotella tannerae, Filifactor alocis and Porphyromonas endodontalis significantly correlated with the severity of periodontal disease.

CONCLUSION

Age, betel chewing, and a new bacterial complex other than the "red complex" correlated to periodontal breakdown in this remote adult Asian population.

A Filifactor alocis-centered co-occurrence group associates with periodontitis across different oral habitats

Periodontitis is a highly prevalent polymicrobial disease worldwide, yet the synergistic pattern of the multiple oral pathogens involved is still poorly characterized. Here, saliva, supragingival and subgingival plaque samples from periodontitis patients and periodontally healthy volunteers were collected and profiled with 16S rRNA gene pyrosequencing. Different oral habitats harbored significantly different microbiota, and segregation of microbiota composition between periodontitis and health was observed as well. Two-step redundancy analysis identified twenty-one OTUs, including Porphyromonas gingivalis, Tannerella forsythia and Filifactor alocis, as potential pathogens that were significantly associated with periodontitis and with two periodontitis diagnostic parameters (pocket depth and attachment loss) in both saliva and supragingival plaque habitats. Interestingly, pairwise correlation analysis among the 21 OTUs revealed that Filifactor alocis was positively correlated with seven other putative pathogens (R > 0.6, P < 0.05), forming a co-occurrence group that was remarkably enriched in all three habitats of periodontitis patients. This bacterial cluster showed a higher diagnostic value for periodontitis than did any individual potential pathogens, especially in saliva. Thus, our study identified a potential synergistic ecological pattern involving eight co-infecting pathogens across various oral habitats, providing a new framework for understanding the etiology of periodontitis and developing new diagnoses and therapies.

Subgingival microbiome in smokers and non-smokers in Korean chronic periodontitis patients

Smoking is a major environmental factor associated with periodontal diseases. However, we still have a very limited understanding of the relationship between smoking and subgingival microflora in the global population. Here, we investigated the composition of subgingival bacterial communities from the pooled plaque samples of smokers and non-smokers, 134 samples in each group, in Korean patients with moderate chronic periodontitis using 16S rRNA gene-based pyrosequencing. A total of 17,927 reads were analyzed and classified into 12 phyla, 126 genera, and 394 species. Differences in bacterial communities between smokers and non-smokers were examined at all phylogenetic levels. The genera Fusobacterium, Fretibacterium, Streptococcus, Veillonella, Corynebacterium, TM7, and Filifactor were abundant in smokers. On the other hand, Prevotella, Campylobacter, Aggregatibacter, Veillonellaceae GQ422718, Haemophilus, and Prevotellaceae were less abundant in smokers. Among species-level taxa occupying > 1% of whole subgingival microbiome of smokers, higher abundance (≥ 2.0-fold compared to non-smokers) of seven species or operational taxonomic units (OTUs) was found: Fusobacterium nucleatum, Neisseria sicca, Neisseria oralis, Corynebacterium matruchotii, Veillonella dispar, Filifactor alocis, and Fretibacterium AY349371. On the other hand, lower abundance of 11 species or OTUs was found in smokers: Neisseria elongata, six Prevotella species or OTUs, Fusobacterium canifelinum, Aggregatibacter AM420165, Selenomonas OTU, and Veillonellaceae GU470897. Species richness and evenness were similar between the groups whereas diversity was greater in smokers than non-smokers. Collectively, the results of the present study indicate that differences exist in the subgingival bacterial community between smoker and non-smoker patients with chronic moderate periodontitis in Korea, suggesting that cigarette smoking considerably affects subgingival bacterial ecology.

The oral microbiome diversity and its relation to human diseases

As one of the most clinically relevant human habitats, the human mouth is colonized by a set of microorganisms, including bacteria, archaea, fungi, and viruses. Increasing evidence has supported that these microbiota contribute to the two commonest oral diseases of man (dental caries and periodontal diseases), presenting significant risk factors to human health conditions, such as tumor, diabetes mellitus, cardiovascular diseases, bacteremia, preterm birth, and low birth weight in infants. It is widely accepted that oral microorganisms cause diseases mainly by a synergistic or cooperative way, and the interspecies interactions within the oral community play a crucial role in determining whether oral microbiota elicit diseases or not. Since a comprehensive understanding of the complex interspecies interactions within a community needs the knowledge of its endogenous residents, a plenty of research have been carried out to explore the oral microbial diversity. In this review, we focus on the recent progress in this field, including the oral microbiome composition and its association with human diseases.

Age-dependent changes in Porphyromonas gingivalis and Prevotella species/phylotypes in healthy gingiva and inflamed/diseased sub-gingival sites

OBJECTIVES

Early colonisation of oral surfaces by periodontal pathogens presents a significant risk factor for subsequent development of destructive disease affecting tissues that support the dentition. The aims of the present study were to establish the age-dependent relationship between sub-gingival profiles of 22 Prevotella species/phylotypes in children, adolescents and adults from an isolated Aboriginal community and, further, to use this information to identify Prevotella species that could serve as microbial risk indicators.

MATERIALS AND METHODS

DNA isolated from sub-gingival plaque samples (three healthy sites and three inflamed/diseased sites) from adults, adolescents and children was screened for Porphyromonas gingivalis load and 22 Prevotella species/phylotypes by species-specific PCR.

RESULTS

A noticeable feature in adolescents was the marked increase in colonisation by P. gingivalis across all test sites. The mean number of Prevotella species/phylotypes colonising inflamed/diseased sub-gingival sites increased with age. Progressive partitioning of selected Prevotella species/phylotypes to healthy or inflamed/diseased sites was evident. Prevalence of Prevotella intermedia, Prevotella oral clone P4PB_24 and Prevotella oris increased significantly with age in diseased sites. Similarly, significant age-dependent increase in colonisation of healthy as well as inflamed/diseased sub-gingival sites was apparent for Prevotella oralis, Prevotella multiformis, Prevotella denticola, Prevotella strain P4P_53 and Prevotella oral clone BR014.

CONCLUSION

Early colonisation of children by P. gingivalis, P. intermedia and Prevotella oral clone P4PB_24 provides indication of risk for subsequent development of periodontal disease.

CLINICAL RELEVANCE

In the present study, the complexity of Prevotella species within gingival sites is explored as a basis for evaluating contribution of Prevotella species to disease.

Proteome analysis of coinfection of epithelial cells with Filifactor alocis and Porphyromonas gingivalis shows modulation of pathogen and host regulatory pathways

Changes in periodontal status are associated with shifts in the composition of the bacterial community in the periodontal pocket. The relative abundances of several newly recognized microbial species, including Filifactor alocis, as-yet-unculturable organisms, and other fastidious organisms have raised questions on their impact on disease development. We have previously reported that the virulence attributes of F. alocis are enhanced in coculture with Porphyromonas gingivalis. We have evaluated the proteome of host cells and F. alocis during a polymicrobial infection. Coinfection of epithelial cells with F. alocis and P. gingivalis strains showed approximately 20% to 30% more proteins than a monoinfection. Unlike F. alocis ATCC 35896, the D-62D strain expressed more proteins during coculture with P. gingivalis W83 than with P. gingivalis 33277. Proteins designated microbial surface component-recognizing adhesion matrix molecules (MSCRAMMs) and cell wall anchor proteins were highly upregulated during the polymicrobial infection. Ultrastructural analysis of the epithelial cells showed formation of membrane microdomains only during coinfection. The proteome profile of epithelial cells showed proteins related to cytoskeletal organization and gene expression and epigenetic modification to be in high abundance. Modulation of proteins involved in apoptotic and cell signaling pathways was noted during coinfection. The enhanced virulence potential of F. alocis may be related to the differential expression levels of several putative virulence factors and their effects on specific host cell pathways.

Centipeda periodontii in human periodontitis

This study assessed the subgingival occurrence of the flagellated, Gram-negative, anaerobic rod Centipeda periodontii in chronic periodontitis and periodontal health/gingivitis with species-specific nucleic acid probes, and evaluated the in vitro resistance of subgingival isolates to therapeutic levels of amoxicillin, metronidazole, and doxycycline. Subgingival plaque biofilm specimens from 307 adults with chronic periodontitis, and 48 adults with periodontal health/localized gingivitis, were evaluated with digoxigenin-labeled, whole-chromosomal, DNA probes to C. periodontii ATCC 35019 possessing a 10(4) cell detection threshold. Fifty-two C. periodontii subgingival culture isolates were assessed on antibiotic-supplemented enriched Brucella blood agar for in vitro resistance to either amoxicillin at 2 µg/ml, metronidazole at 4 µg/ml, or doxycycline at 2 µg/ml. A significantly greater subgingival occurrence of C. periodontii was found in chronic periodontitis subjects as compared to individuals with periodontal health/gingivitis (13.4 vs. 0 %, P < 0.003), although high subgingival counts of the organism (≥ 10(6) cells) were rarely detected (1.3 % of chronic periodontitis subjects). In vitro resistance was not found to amoxicillin or metronidazole, and to doxycycline in only 2 (3.9 %) of the 52 C. periodontii clinical isolates studied. These findings indicate that C. periodontii is not a major constituent of the subgingival microbiome in chronic periodontitis or periodontal health/gingivitis. The potential contribution of C. periodontii to periodontal breakdown in the few chronic periodontitis subjects who yielded high subgingival levels of the organism remains to be delineated. C. periodontii clinical isolates were susceptible in vitro to therapeutic concentrations of three antibiotics frequently used in treatment of human periodontitis.

Quantitative analysis of classical and new putative periodontal pathogens in subgingival biofilm: a case-control study

BACKGROUND AND OBJECTIVES

A number of species/phylotypes have been newly implicated as putative periopathogens. The objective of this study was to explore associations among classical and new pathogens in subgingival biofilm and to assess their relative importance to chronic periodontitis.

MATERIAL AND METHODS

Pooled subgingival biofilm samples were obtained from 40 patients with chronic periodontitis and 40 healthy controls. Taqman q-PCR assays were used to determine the absolute and relative counts of Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Parvimonas micra, Filifactor alocis, oral Synergistetes and oral TM7s. Microbial associations were assessed using cluster analysis. Different statistical models were used to explore associations between microbial parameters and periodontitis.

RESULTS

The median log and relative counts were lowest for TM7s (4.4 and 0.0016%, respectively) and highest for oral Synergistetes (7.2 and 1.4%, respectively). Oral Synergistetes clustered strongly with the red complex, particularly T. forsythia (100% rescaled similarity). All species/phylotypes except TM7s were significantly associated with periodontitis (Mann-Whitney test; p ≤ 0.005). However, P. gingivalis and F. alocis lost association after adjusting for confounders (ordinal regression). In receiving operator characteristic curve analysis, the log counts of oral Synergistetes were the best markers of periodontitis (82.5% sensitivity and specificity), followed by those of T. forsythia, P. micra and T. denticola. In prediction analysis, however, P. micra was the only microbial predictor of periodontal parameters.

CONCLUSIONS

Oral Synergistetes are presented here as new members of the red complex, with relative importance to periodontitis exceeding that of the classical members. P. micra is shown as an important periodontal pathogen warranting more attention.

Microbial role in periodontitis: Have we reached the top? Some unsung bacteria other than red complex

The microbial etiology of periodontal disease has been the focus of researchers for a long time. The search for the pathogens of periodontal diseases has been underway for more than 100 years, and continues up today. Despite the increasing knowledge about oral microbiota, we are not able to implicate any one particular organism that can be considered as a candidate pathogen. In fact the term "candidate pathogen" has lost its steam with a myriad of microorganisms being incriminated from time to time. Most studies of the bacterial etiology of periodontitis have used either culture-based or targeted deoxyribonucleic acid approaches and so it is likely that pathogens remain undiscovered. The advent of 16S cloning and sequencing has facilitated identification of several uncultivable bacteria in the oral cavity. The concept that not one single organism, but several organisms contained in the biofilm orchestrating in a medley of the show appears to be more plausible. The present review highlights some lesser known bacteria associated with periodontal destruction.

Subgingival bacteria in Ghanaian adolescents with or without progression of attachment loss

OBJECTIVE

This study describes subgingival bacterial profiles associated with clinical periodontal status in Ghanaian adolescents with or without progression of attachment loss.

MATERIALS AND METHODS

Among 500 adolescents included in a cohort study, 397 returned 2 years later for a periodontal re-examination, including full-mouth CAL measurements. At follow-up, a subgroup of 98 adolescents was also subjected to bacterial sampling with paper points at four periodontal sites (mesial aspect of 11, 26, 31, and 46) and analyzed with the checkerboard DNA-DNA hybridization technique against DNA-probes from nine periodontitis-associated bacterial species.

RESULTS

The 98 Ghanaian adolescents examined in the present study were similar to the entire group examined at the 2-year follow-up with respect to age, gender, and CAL ≥3 mm. A high detection frequency of Fusobacterium nucleatum and Prevotella intermedia (>99%) using checkerboard analysis was found, while for Aggregatibacter actinomycetemcomitans the detection frequency was <50%. A strong correlation was found at the individual level between the presence of P. intermedia and the total CAL change, and P. intermedia and Porphyromonas gingivalis were strongly correlated with a change in CAL and probing pocket depth (PPD) at the sampled sites. In a linear regression model, a significant discriminating factor for the total CAL change in the dentition during the 2-year follow-up period was obtained for P. intermedia and public school.

CONCLUSION

This study indicates that subgingival bacterial species other than A. actinomycetemcomitans, for example, P. intermedia, have a significant association with periodontal breakdown (change in CAL) in Ghanaian adolescents with progression of periodontal attachment loss.

Life in a Diverse Oral Community - Strategies for Oxidative Stress Survival

BACKGROUND

While the oral cavity harbors more than 680 bacterial species, the interaction and association of selected bacterial species play a role in periodontal diseases. Bacterial species including Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia, a consortium previously designated as the "red complex" is now being expanded to include other new emerging pathogens that are significantly associated with periodontal disease.

HIGHLIGHT

In addition to novel mechanisms for oxidative resistance of individual species, community dynamics may lead to an overall strategy for survival in the inflammatory environment of the periodontal pocket. Complex systems controlled by response regulators protect against oxidative and nitrosative stress.

CONCLUSION

The combination of these multifaceted strategies would provide a comprehensive defense and support system against the repetitive host immune response to promote microbial persistence and disease.

Lessons learned and unlearned in periodontal microbiology

Periodontal diseases are initiated by bacterial species living in polymicrobial biofilms at or below the gingival margin and progress largely as a result of the inflammation elicited by specific subgingival species. In the past few decades, efforts to understand the periodontal microbiota have led to an exponential increase in information about biofilms associated with periodontal health and disease. In fact, the oral microbiota is one of the best-characterized microbiomes that colonize the human body. Despite this increased knowledge, one has to ask if our fundamental concepts of the etiology and pathogenesis of periodontal diseases have really changed. In this article we will review how our comprehension of the structure and function of the subgingival microbiota has evolved over the years in search of lessons learned and unlearned in periodontal microbiology. More specifically, this review focuses on: (i) how the data obtained through molecular techniques have impacted our knowledge of the etiology of periodontal infections; (ii) the potential role of viruses in the etiopathogenesis of periodontal diseases; (iii) how concepts of microbial ecology have expanded our understanding of host-microbe interactions that might lead to periodontal diseases; (iv) the role of inflammation in the pathogenesis of periodontal diseases; and (v) the impact of these evolving concepts on therapeutic and preventive strategies to periodontal infections. We will conclude by reviewing how novel systems-biology approaches promise to unravel new details of the pathogenesis of periodontal diseases and hopefully lead to a better understanding of their mechanisms.

Diagnosis and anti-infective therapy of periodontitis

Periodontal diseases (gingivitis and periodontitis) are chronic bacterial infections with a remarkably high prevalence and morbidity. Periodontitis, in contrast to gingivitis, is not reversible, is associated with certain bacterial species and affects all of the soft tissue and bone that support teeth. Among the periodontal pathogens, species, such as Aggregatibacter (Actinobacillus) actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, and several forms of uncultivable spirochetes play the major role in the pathogenesis. In severe chronic, recurrent and especially aggressive forms of periodontitis, diagnosis of the species involved and, whenever possible, an optimized evidence-based antimicrobial treatment is indicated. In order to monitor alarming bacterial changes in the periodontal pocket, several techniques, namely microscopy, culture, immunoassays, enzyme tests and DNA-based techniques, have been established and the methods are described in the first part of this review. In the second part, the selection and use of locally delivered (topical) and systemic antibiotics used adjunctively in periodontal therapy are discussed.

Filifactor alocis infection and inflammatory responses in the mouse subcutaneous chamber model

Recent microbiome studies have implicated a role for Filifactor alocis in periodontal disease. In this study, we investigated the colonization and survival properties of F. alocis in a mouse subcutaneous chamber model of infection and characterized host innate immune responses. An infection of 10(9) F. alocis successfully colonized all chambers; however, the infection was cleared after 72 h. F. alocis elicited a local inflammatory response with neutrophils recruited into the chambers at 2 h postinfection along with an increase in levels of the proinflammatory cytokines interleukin 1β (IL-1β), IL-6, and tumor necrosis factor (TNF). F. alocis also induced apoptosis in chamber epithelial cells and neutrophils. Consistent with resolution of infection, neutrophil numbers and cytokine levels returned to baseline by 72 h. Fluorescent in situ hybridization (FISH) and quantitative PCR demonstrated that F. alocis exited the chambers and spread to the spleen, liver, lung, and kidney. Massive neutrophil infiltration was observed in the spleen and lungs, and the recruited neutrophils were in close proximity to the infecting bacteria. Significant epithelial injury was observed in the kidneys. Infection of all tissues was resolved after 7 days. This first in vivo study of the pathogenicity of F. alocis shows that in the chamber model the organism can establish a proinflammatory, proapoptotic local infection which is rapidly resolved by the host concordant with neutrophil influx. Moreover, F. alocis can spread to, and transiently infect, remote tissues where neutrophils can also be recruited.

Oral community interactions of Filifactor alocis in vitro

Filifactor alocis is a gram positive anaerobe that is emerging as an important periodontal pathogen. In the oral cavity F. alocis colonizes polymicrobial biofilm communities; however, little is known regarding the nature of the interactions between F. alocis and other oral biofilm bacteria. Here we investigate the community interactions of two strains of F. alocis with Streptococcus gordonii, Fusobacterium nucleatum, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, organisms with differing pathogenic potential in the oral cavity. In an in vitro community development model, S. gordonii was antagonistic to the accumulation of F. alocis into a dual species community. In contrast, F. nucleatum and the type strain of F. alocis formed a synergistic partnership. Accumulation of a low passage isolate of F. alocis was also enhanced by F. nucleatum. In three species communities of S. gordonii, F. nucleatum and F. alocis, the antagonistic effects of S. gordonii superseded the synergistic effects of F. nucleatum toward F. alocis. The interaction between A. actinomycetemcomitans and F. alocis was strain specific and A. actinomycetemcomitans could either stimulate F. alocis accumulation or have no effect depending on the strain. P. gingivalis and F. alocis formed heterotypic communities with the amount of P. gingivalis greater than in the absence of F. alocis. However, while P. gingivalis benefited from the relationship, levels of F. alocis in the dual species community were lower compared to F. alocis alone. The inhibitory effect of P. gingivalis toward F. alocis was dependent, at least partially, on the presence of the Mfa1 fimbrial subunit. In addition, AI-2 production by P. gingivalis helped maintain levels of F. alocis. Collectively, these results show that the pattern of F. alocis colonization will be dictated by the spatial composition of microbial microenvironments, and that the organism may preferentially accumulate at sites rich in F. nucleatum.

Effect of probiotic lozenges on inflammatory reactions and oral biofilm during experimental gingivitis

AIM

Probiotic bacteria have been introduced for prevention and treatment of periodontal diseases. The aim was to assess if daily oral administration of probiotic bacteria could influence the inflammatory response and the composition of supragingival plaque in an experimental gingivitis model.

MATERIALS AND METHODS

Eighteen healthy female adults volunteered after informed consent. A double-blind randomized placebo-controlled cross-over design was used. The buccal surface of first molars was used as experimental sites. A mouth-guard covering the first premolar to second molar was used when brushing, preventing accidental cleaning during 3 weeks of plaque accumulation. Lozenges containing L. reuteri (ATCC55730 and ATCC PTA5289) or placebo were taken twice a day. During the run-in and washout periods, professional tooth cleaning was performed 5 days/week. At baseline and follow-up, plaque index, gingival index and bleeding on probing were recorded. Samples of gingival crevicular fluid (GCF) were analysed for concentration of seven inflammatory mediators. Bacterial samples were processed with checkerboard DNA/DNA-hybridization.

RESULTS

All subjects presented a local plaque accumulation and developed manifest gingivitis at the test sites during the intervention periods. The volume of GCF increased in both groups but was statistically significant only in the placebo group (p < 0.05). The concentrations of IL1-β and IL-18 increased significantly (p < 0.05), while IL-8 and MIP1-β decreased (p < 0.05). No differences were displayed between test and placebo. Likewise, the microbial composition did not differ between the groups.

CONCLUSION

Daily intake of probiotic lozenges did not seem to significantly affect the plaque accumulation, inflammatory reaction or the composition of the biofilm during experimental gingivitis.

Pattern of distribution of Prevotella species/phylotypes associated with healthy gingiva and periodontal disease

The purpose of the present study was to obtain diverse profiles of Prevotella species associated with gingival sites in an isolated Aboriginal and an urban community by phylogenetic analysis and to establish patterns of association of identified Prevotella species in gingival sites. Species/phylotypes identified from the phylogenetic analysis of near full-length Bacteroidetes 16S rRNA gene sequences cloned from subgingival plaque samples obtained from an Aboriginal community were compared with those from an ethnically diverse urban metropolitan population suffering from periodontal disease. Specific primer sets were designed and validated for 22 distinct Prevotella species from the 24 species/phylotypes identified from both populations. Within the isolated Aboriginal community, gingival sites in adults were colonised by a mean of 15 different Prevotella species. Prevotella sp. oral clone P4PB24, Prevotella intermedia, Prevotella oralis, Prevotella denticola and Prevotella sp. strain P4P62 had the highest association with increasing probing depth in diseased sites (p < 0.05). P. intermedia and Prevotella sp. oral clone P4PB24, the Prevotella species significantly associated with increasing probing depth in diseased gingival sites and also strongly associated with P. gingivalis load (p < 0.05) in diseased gingival sites, showed significant correlation for co-colonisation (r = 0.6). Prevotella sp. oral clone B31FD, showing strong association with P. gingivalis load (p < 0.05) in diseased gingival sites, showed no significant correlation for co-colonisation with any other Prevotella species. This study provides a comprehensive analysis of Prevotella species associated with gingival sites for the informative evaluation of the epidemiology of infection by this genus.

Porphyromonas endodontalis in chronic periodontitis: a clinical and microbiological cross-sectional study

Background

Although previous studies have shown the presence of Porphyromonas endodontalis in chronic periodontitis associated with periapical lesions, the occurrence of this pathogen in diseased periodontal sites without periapical lesions has been poorly investigated.

Objective

The aims of this study were to quantify P. endodontalis in patients with chronic periodontitis without periapical lesions, to evaluate the potential correlation of P. endodontalis with Porphyromonas gingivalis and Tannerella forsythia, and to evaluate the ability of periodontal treatment to reduce these pathogens.

Design

Patients with generalized chronic periodontitis were selected by recording clinical attachment level (CAL), probing depth (PD), and bleeding on probing (BOP). Subgingival samples from 30 diseased nonadjacent sites (CAL≥5 mm, PD between 5 and 7 mm and positive BOP) and 30 healthy nonadjacent sites (PD≤3 mm and negative BOP) were collected and subjected to microbial analysis by quantitative polymerase chain reaction (qPCR) The variables of age, PD, CAL and BOP of all individuals were analyzed using the paired t-test (GrapPad Prism5^®). Data of bacteria quantification were subjected to a normality test (D'Agostino-Pearson Test). For bacterial correlation analysis, the Spearman correlation was used.

Results

Our results showed that diseased sites had significantly higher levels of P. endodontalis compared to healthy sites, similar to the results obtained for P. gingivalis and T. forsythia. The numbers of all bacterial species were reduced significantly after mechanical periodontal treatment. P. endodontalis was significantly correlated with the presence of T. forsythia and P. gingivalis in the diseased group.

Conclusion

Our results suggest that there is a high prevalence of P. endodontalis, P. gingivalis and T. forsythia in periodontitis sites and that mechanical periodontal treatment is effective at reducing the pathogens studied.