Treponema lecithinolyticum sp. nov., a small saccharolytic spirochaete with phospholipase A and C activities associated with periodontal diseases

Tolerance to intraoral biofilms and their effectiveness in improving mouth dryness and modifying oral microbiota in patients with primary Sjögren's syndrome: "Predelfi study"

INTRODUCTION

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease characterized by exocrine gland dysfunction. No therapeutic strategy is sufficient on its own for the management of dry mouth and therapeutic innovations are required.

METHODS

This Predelfi study was a single-center, prospective, comparative, randomized, double-blind, cross-over controlled study with the primary objective of assessing the tolerance to and effectiveness of two adhesive biofilms (containing prebiotics and, sodium alginate, respectively) in patients with pSS and hyposialia (#NCT04206826 in ClinicalTrials.gov). Secondary objectives were to obtain initial data regarding the clinical effectiveness of such biofilms in the improvement of signs and symptoms related to dry mouth and potential changes in the oral microbiota. Ten pSS patients with pSS were included (9 females and 1 male) with a mean age of 58.1 ± 14.0 years.

RESULTS AND DISCUSSION

Tolerance to the prebiotic and sodium alginate biofilms was assessed by the patients (visual analog scale [VAS] score 66.7 and 87.6, respectively) and the practitioner (90 and 100, respectively). The absolute changes in the VAS scores at the start and end of each treatment period highlighted an improvement in mouth dryness for the sodium alginate versus the prebiotic biofilm. The VAS scores for other parameters (mouth burning sensation; taste alteration; chewing; swallowing and speech difficulties) remained globally comparable between the two groups. Unstimulated salivary flow showed no changes regardless of the biofilm used. Regarding the oral microbiota, the sodium alginate biofilm increased the abundance of the Treponema genus, whereas the use of the prebiotic biofilm as the first treatment increased the abundance of the genera Veillonella and Prevotella. Nevertheless, the prebiotic biofilm appeared to stimulate "milder" genera with regard to periodontal infections. Furthermore, pre-treatment with the prebiotic biofilm prevented the emergence of the Treponema genus induced by subsequent treatment with the sodium alginate biofilm, suggesting a potential protective effect.

Treponema peruense sp. nov., a commensal spirochaete isolated from human faeces

A Gram-stain-negative, obligatory anaerobic spirochaete (RCC2812^T) was isolated from a faecal sample obtained from an individual residing in a remote Amazonian community in Peru. The bacterium showed highest 16S rRNA gene sequence similarity to the pig intestinal spirochete Treponema succinifaciens (89.48 %). Average nucleotide identity values between strain RCC2812^T and all available Treponema genomes from validated type strains were all <73 %, thus clearly lower than the species delineation threshold. The DNA G+C content of RCC2812^T was 41.24 mol%. Phenotypic characterization using the API-ZYM and API 20A systems confirmed the divergent position of this bacterium within the genus Treponema. Strain RCC2812^T could be differentiated from the phylogenetically most closely related T. succinifaciens by the presence of alkaline phosphatase and α -glucosidase activities. Unlike T. succinifaciens, strain RCC2812^T grew equally well with or without serum. Strain RCC2812^T is the first commensal Treponema isolated from the human faecal microbiota of remote populations, and based on the collected data represents a novel Treponema species for which the name Treponema peruense sp. nov. is proposed. The type strain is RCC2812^T (=LMG 31794^T=CIP 111910^T).

Analysis of 1,000+ Type-Strain Genomes Substantially Improves Taxonomic Classification of Alphaproteobacteria

The class Alphaproteobacteria is comprised of a diverse assemblage of Gram-negative bacteria that includes organisms of varying morphologies, physiologies and habitat preferences many of which are of clinical and ecological importance. Alphaproteobacteria classification has proved to be difficult, not least when taxonomic decisions rested heavily on a limited number of phenotypic features and interpretation of poorly resolved 16S rRNA gene trees. Despite progress in recent years regarding the classification of bacteria assigned to the class, there remains a need to further clarify taxonomic relationships. Here, draft genome sequences of a collection of genomes of more than 1000 Alphaproteobacteria and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa recognized as problematic long ago but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera and of a variety of genera to other families. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which are confirmed as valuable taxonomic markers. Similarly, analysis of the gene content was shown to provide valuable taxonomic insights in the class. Significant incongruities between 16S rRNA gene and whole genome trees were not found in the class. The incongruities that became obvious when comparing the results of the present study with existing classifications appeared to be caused mainly by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. Another probable cause of misclassifications in the past is the partially low overall fit of phenotypic characters to the sequence-based tree. Even though a significant degree of phylogenetic conservation was detected in all characters investigated, the overall fit to the tree varied considerably.

Borrelia burgdorferi hijacks cellular metabolism of immune cells: Consequences for host defense

Changes in cellular metabolism have proven to be important factors in driving cell behavior. It has been shown that cellular metabolism of immune cells changes when exposed to or infected by several pathogens: while this is often an adaptation of the host cells to the infection, sometimes it represents a mechanism through which the pathogens evade immune activation. Borrelia burgdorferi sensu lato, the causative agent of Lyme borreliosis, is a pathogen that highly depends on the host to survive, as the bacterium lacks many central metabolic pathways to generate its own nutrients. It is therefore quite likely that the bacterium interacts with host cells to obtain these metabolites and thereby affects metabolism in the host. Previously, several studies have assessed metabolic pathways in B. burgdorferi s.l. and how it adapts to its different host species. However, few studies have looked into how the interaction with the bacterium might affect the host cell metabolism. In this review we present the major metabolic pathways activated during Lyme borreliosis, viewed from both bacterium and host metabolism, and we discuss how these pathways interact with each other, and how they influence pathogenesis of Lyme borreliosis.

The subgingival microbiome associated with periodontitis in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a systemic disease, predisposing patients to other inflammatory conditions including periodontitis. The subgingival microbiome, a key player in periodontitis pathogenesis, is not well characterized in T2DM population. To better understand whether the subgingival microbiome is different between T2DM and systemically healthy, nondiabetic (ND) subjects, we performed a longitudinal analysis of the subgingival microbiome in T2DM patients (n = 15) compared with ND subjects (n = 16). Using metagenomic shotgun sequencing, we investigated the microbiome in the healthy periodontal state, periodontitis state, and resolved state after treatment. We found that in the periodontitis state, the shift in the subgingival microbiome from the healthy state was less prominent in T2DM compared with ND subjects, yet the clinical signs of disease were similar for both. Furthermore, we revealed highly correlated presence of pathogenic species in relative abundance not only in the periodontitis state, but also in the healthy state in T2DM, suggesting an elevated risk of progression to periodontitis in this cohort. We further investigated the functional potentials of the subgingival microbiome and identified a set of microbial marker genes associated with the clinical states. These genes were significantly enriched in 21 pathways, some of which are associated with periodontitis and some potentially link T2DM and periodontitis. This study identified the longitudinal changes of the subgingival microbiome associated with periodontitis in T2DM and suggests that T2DM patients are more susceptible to shifts in the subgingival microbiome toward dysbiosis, potentially due to impaired host metabolic and immune regulation.

Increased transferrin saturation is associated with subgingival microbiota dysbiosis and severe periodontitis in genetic haemochromatosis

Genetic haemochromatosis (GH) is responsible for iron overload. Increased transferrin saturation (TSAT) has been associated with severe periodontitis, which is a chronic inflammatory disease affecting tissues surrounding the teeth and is related to dysbiosis of the subgingival microbiota. Because iron is essential for bacterial pathogens, alterations in iron homeostasis can drive dysbiosis. To unravel the relationships between serum iron biomarkers and the subgingival microbiota, we analysed samples from 66 GH patients. The co-occurrence analysis of the microbiota showed very different patterns according to TSAT. Healthy and periopathogenic bacterial clusters were found to compete in patients with normal TSAT (≤45%). However, significant correlations were found between TSAT and the proportions of Porphyromonas and Treponema, which are two genera that contain well-known periopathogenic species. In patients with high TSAT, the bacterial clusters exhibited no mutual exclusion. Increased iron bioavailability worsened periodontitis and promoted periopathogenic bacteria, such as Treponema. The radical changes in host-bacteria relationships and bacterial co-occurrence patterns according to the TSAT level also suggested a shift in the bacterial iron supply from transferrin to NTBI when TSAT exceeded 45%. Taken together, these results indicate that iron bioavailability in biological fluids is part of the equilibrium between the host and its microbiota.

The occurrence of Treponema spp. in gingival plaque from dogs with varying degree of periodontal disease

Periodontal disease is common in dogs and is initiated by gingival plaque composed of several hundred bacterial species. Some of these species have specifically been pointed out as potential periodontal pathogens, such as Treponema spp. Treponema spp. are difficult to culture and therefore the majority have been detected by culture-independent methods, such as PCR (Polymerase Chain Reaction). This leaves many Treponema spp. uncharacterized and unnamed. In this study, treponemes were investigated in gingival plaque from dogs with varying degree of periodontal disease with the aim to describe their occurrence and diversity in dogs. The methods used were culture, phase-contrast microscopy, PCR targeting the 16SrRNA-tRNA^Ile intergenic spacer region (ISR2), sequencing of the ISR2 and phylogenetic analysis. Treponema spp. were detected in samples from 10 out of 11 dogs and isolates were obtained from six dogs. Both healthy and periodontitis affected dogs were Treponema positive. Phylogenetic analysis, based on ISR2 sequences, revealed a large diversity of treponemes in the study population that were found to be distributed mainly in two groups, corresponding to the human oral treponeme phylogroups II (Treponema denticola) and IV (Treponema maltophilum) genetic groups. They were generally more distantly related to other treponemes in these groups. Treponemes from dogs with periodontitis and dogs with mild gingivitis without periodontitis did not differ in any obvious way. The results indicate that several phylotypes of oral treponemes are common in dogs regardless of periodontal status.

Alterations in the oral microbiome in HIV-infected participants after antiretroviral therapy administration are influenced by immune status

OBJECTIVE

To characterize the oral bacterial microbiome in HIV-infected participants at baseline and after 24 weeks of EFV/FTC/TDF.

DESIGN

Thirty-five participants co-enrolled in two AIDS Clinical Trials Group (ACTG) studies, A5272 and A5280, with paired saliva samples and complete data sets were assessed.

METHODS

Paired saliva samples were evaluated for bacterial microbiome using 16S rDNA PCR followed by Illumina sequencing. Diversity and differential abundance was compared between groups. A random forest classification scheme was used to determine the contribution of parameters in classifying participants' CD4+ T-cell count.

RESULTS

Bacterial communities demonstrated considerable variability both within participants and between timepoints, although they became more similar after 24 weeks of ART. At baseline, both the number of taxa detected and the average alpha diversity were variable between participants, but did not differ significantly based on CD4+ cell count, viral load or other factors. After 24 weeks of ART samples obtained from participants with persistently low CD4+ T-cell counts had significantly higher bacterial richness and diversity. Several differentially abundant taxa, including Porphyromonas species associated with periodontal disease, were identified, which discriminated between baseline and posttreatment samples. Analysis demonstrated that although inflammatory markers are important in untreated disease, the salivary microbiome may play an important role in CD4+ T-cell count recovery after ART.

CONCLUSION

Shifts in the oral microbiome after ART initiation are complex, and may play an important role in immune function and inflammatory disease.

Multilocus Sequence Analysis of Phylogroup 1 and 2 Oral Treponeme Strains

More than 75 "species-level" phylotypes of spirochete bacteria belonging to the genus Treponema reside within the human oral cavity. The majority of these oral treponeme phylotypes correspond to as-yet-uncultivated taxa or strains of uncertain standing in taxonomy. Here, we analyze phylogenetic and taxonomic relationships between oral treponeme strains using a multilocus sequence analysis (MLSA) scheme based on the highly conserved 16S rRNA, pyrH, recA, and flaA genes. We utilized this MLSA scheme to analyze genetic data from a curated collection of oral treponeme strains (n = 71) of diverse geographical origins. This comprises phylogroup 1 (n = 23) and phylogroup 2 (n = 48) treponeme strains, including all relevant American Type Culture Collection reference strains. The taxonomy of all strains was confirmed or inferred via the analysis of ca. 1,450-bp 16S rRNA gene sequences using a combination of bioinformatic and phylogenetic approaches. Taxonomic and phylogenetic relationships between the respective treponeme strains were further investigated by analyzing individual and concatenated flaA (1,074-nucleotide [nt]), recA (1,377-nt), and pyrH (696-nt) gene sequence data sets. Our data confirmed the species differentiation between Treponema denticola (n = 41) and Treponema putidum (n = 7) strains. Notably, our results clearly supported the differentiation of the 23 phylogroup 1 treponeme strains into five distinct "species-level" phylotypes. These respectively corresponded to "Treponema vincentii" (n = 11), Treponema medium (n = 1), "Treponema sinensis" (Treponema sp. IA; n = 4), Treponema sp. IB (n = 3), and Treponema sp. IC (n = 4). In conclusion, our MLSA-based approach can be used to effectively discriminate oral treponeme taxa, confirm taxonomic assignment, and enable the delineation of species boundaries with high confidence.

IMPORTANCE

Periodontal diseases are caused by persistent polymicrobial biofilm infections of the gums and underlying tooth-supporting structures and have a complex and variable etiology. Although Treponema denticola is strongly associated with periodontal diseases, the etiological roles of other treponeme species/phylotypes are less well defined. This is due to a paucity of formal species descriptions and a poor understanding of genetic relationships between oral treponeme taxa. Our study directly addresses these issues. It represents one of the most comprehensive analyses of oral treponeme strains performed to date, including isolates from North America, Europe, and Asia. We envisage that our results will greatly facilitate future metagenomic efforts aimed at characterizing the clinical distributions of oral treponeme species/phylotypes, helping investigators to establish a more detailed understanding of their etiological roles in periodontal diseases and other infectious diseases. Our results are also directly relevant to various polymicrobial tissue infections in animals, which also involve treponeme populations.

Novel Pathogens in Periodontal Microbiology

Periodontitis is a polymicrobial disease caused by complex interactions between distinct pathogens in a biofilm resulting in the destruction of periodontal tissues. It seems evident that unknown microorganisms might be involved in onset or progression of periodontitis. For many decades, research in the field of oral microbiology failed to identify certain subgingival microbiota due to technical limitations but, over a period of 12 years using molecular approaches and sequencing techniques, it became feasible to reveal the existence of new periodontal pathogens. Therefore, it is evident that in addition to conventional periodontal pathogens, other microbes might be involved in onset and progression of periodontitis. The novel pathogens enlisted under periodontal phylogeny include Cryptobacterium curtum, Dialister pneumosintes, Filifactor alocis, Mitsuokella dentalis, Slackia exigua, Selenomonas sputigena, Solobacterium moorei, Treponema lecithinolyticum, and Synergistes. The polymicrobial etiology of periodontitis has been elucidated by comprehensive techniques, and studies throwing light on the possible virulence mechanisms possessed by these novel periodontal pathogens are enlisted.

Identification and genome reconstruction of abundant distinct taxa in microbiomes from one thermophilic and three mesophilic production-scale biogas plants

BACKGROUND

Biofuel production from conversion of biomass is indispensable in the portfolio of renewable energies. Complex microbial communities are involved in the anaerobic digestion process of plant material, agricultural residual products and food wastes. Analysis of the genetic potential and microbiology of communities degrading biomass to biofuels is considered to be the key to develop process optimisation strategies. Hence, due to the still incomplete taxonomic and functional characterisation of corresponding communities, new and unknown species are of special interest.

RESULTS

Three mesophilic and one thermophilic production-scale biogas plants (BGPs) were taxonomically profiled using high-throughput 16S rRNA gene amplicon sequencing. All BGPs shared a core microbiome with the thermophilic BGP featuring the lowest diversity. However, the phyla Cloacimonetes and Spirochaetes were unique to BGPs 2 and 3, Fusobacteria were only found in BGP3 and members of the phylum Thermotogae were present only in the thermophilic BGP4. Taxonomic analyses revealed that these distinctive taxa mostly represent so far unknown species. The only exception is the dominant Thermotogae OTU featuring 16S rRNA gene sequence identity to Defluviitoga tunisiensis L3, a sequenced and characterised strain. To further investigate the genetic potential of the biogas communities, corresponding metagenomes were sequenced in a deepness of 347.5 Gbp in total. A combined assembly comprised 80.3 % of all reads and resulted in the prediction of 1.59 million genes on assembled contigs. Genome binning yielded genome bins comprising the prevalent distinctive phyla Cloacimonetes, Spirochaetes, Fusobacteria and Thermotogae. Comparative genome analyses between the most dominant Thermotogae bin and the very closely related Defluviitoga tunisiensis L3 genome originating from the same BGP revealed high genetic similarity. This finding confirmed applicability and reliability of the binning approach. The four highly covered genome bins of the other three distinct phyla showed low or very low genetic similarities to their closest phylogenetic relatives, and therefore indicated their novelty.

CONCLUSIONS

In this study, the 16S rRNA gene sequencing approach and a combined metagenome assembly and binning approach were used for the first time on different production-scale biogas plants and revealed insights into the genetic potential and functional role of so far unknown species.

Exploring salivary microbiota in AIDS patients with different periodontal statuses using 454 GS-FLX Titanium pyrosequencing

Patients with acquired immunodeficiency syndrome (AIDS) are at high risk of opportunistic infections. Oral manifestations have been associated with the level of immunosuppression, these include periodontal diseases, and understanding the microbial populations in the oral cavity is crucial for clinical management. The aim of this study was to examine the salivary bacterial diversity in patients newly admitted to the AIDS ward of the Public Health Clinical Center (China). Saliva samples were collected from 15 patients with AIDS who were randomly recruited between December 2013 and March 2014. Extracted DNA was used as template to amplify bacterial 16S rRNA. Sequencing of the amplicon library was performed using a 454 GS-FLX Titanium sequencing platform. Reads were optimized and clustered into operational taxonomic units for further analysis. A total of 10 bacterial phyla (106 genera) were detected. Firmicutes, Bacteroidetes, and Proteobacteria were preponderant in the salivary microbiota in AIDS patients. The pathogen, Capnocytophaga sp., and others not considered pathogenic such as Neisseria elongata, Streptococcus mitis, and Mycoplasma salivarium but which may be opportunistic infective agents were detected. Dialister pneumosintes, Eubacterium infirmum, Rothia mucilaginosa, and Treponema parvum were preponderant in AIDS patients with periodontitis. Patients with necrotic periodontitis had a distinct salivary bacterial profile from those with chronic periodontitis. This is the first study using advanced sequencing techniques focused on hospitalized AIDS patients showing the diversity of their salivary microbiota.

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.

Comparative analysis of oral treponemes associated with periodontal health and disease

BACKGROUND

Periodontal diseases, such as periodontitis, are chronic inflammatory infections affecting the gingivae (gums), underlying connective tissues and bone that support the teeth. Oral treponemes (genus Treponema) are widely-considered to play important roles in periodontal disease etiology and pathogenesis; however, precise relationships remain to be fully established.

METHODS

A 16S rRNA clone library-based approach was used to comprehensively characterize and compare the diversity of treponeme taxa present in subgingival plaque sampled from periodontitis patients (n = 10) versus periodontitis-free controls (n = 10). 16S rRNA gene sequences were assigned to operational taxonomic units (OTUs) using a 99% identity cut-off A variety of taxonomy (OTU) and phylogeny-based statistical approaches were used to compare populations of treponeme OTUs present in both subject groups.

RESULTS

A total of 615 plasmid clones containing ca. 1500 bp Treponema 16S rRNA gene sequences were obtained; 365 from periodontitis subjects, 250 from periodontitis-free controls. These were assigned to 110 treponeme OTUs. 93 OTUs were detected in the periodontitis subjects (mean 9.3 ± 5.2 OTUs per subject; range 9-26), and 43 OTUs were detected in controls (mean 4.3 ± 5.9 OTUs per subject; range 3-20). OTUs belonging to oral treponeme phylogroups 1-7 were detected in both subject sets. Phylogroup 1 treponemes had the highest levels of OTU richness (diversity) and clonal abundance within both subject groups. Levels of OTU richness and clonal abundance of phylogroup 2 treponemes were significantly higher in the periodontitis subjects (Mann Whitney U-test, p < 0.001). Both OTU-based and phylogeny-based analyses clearly indicated that there were significant differences in the composition of treponeme communities present in periodontitis versus control subjects. The detection frequency of five OTUs showed a statistically-significant correlation with disease status. The OTU (8P47) that corresponded to the type strain of Treponema denticola had the strongest association with periodontitis (p < 0.01).

CONCLUSIONS

Higher levels of treponeme taxon richness and clonal abundance were associated with periodontitis. However, our results clearly indicated that subjects free from clinical symptoms of periodontal disease also contained highly diverse populations of treponeme bacteria within their subgingival microbiota. Our data supports the hypothesis that specific treponeme taxa are associated with periodontal disease.

Bernhard Guggenheim – Critical Mind at the Forefront of Oral Microbiology

Bernhard Guggenheim is a distinguished leader in oral microbiology and immunology and a recipient of many honors. This article outlines his background and scientific career and illuminates some of his important contributions to dental research. At the age of 75, he continues to scrutinize established paradigms and unremittingly fosters demanding biofilm research.

Td92, an outer membrane protein of Treponema denticola, induces osteoclastogenesis via prostaglandin E(2)-mediated RANKL/osteoprotegerin regulation

BACKGROUND AND OBJECTIVE

Periodontitis is a chronic inflammatory disease of the periodontium that causes significant alveolar bone loss. Osteoclasts are bone-resorbing multinucleated cells. Osteoblasts regulate osteoclast differentiation by expression of RANKL and osteoprotegerin (OPG). Td92 is a surface-exposed outer membrane protein of Treponema denticola, a periodontopathogen. Although it has been demonstrated that Td92 acts as a stimulator of various proinflammatory mediators, the role of Td92 in alveolar bone resorption remains unclear. Therefore, in this study, we investigated the role of Td92 in bone resorption.

MATERIAL AND METHODS

Mouse bone marrow cells were co-cultured with calvariae-derived osteoblasts in the presence or absence of Td92. Osteoclast formation was assessed by TRAP staining. Expressions of RANKL, osteoprotegerin (OPG) and prostaglandin E(2) (PGE(2) ) in osteoblasts were estimated by ELISA.

RESULTS

Td92 induced osteoclast formation in the co-cultures. In the osteoblasts, RANKL and PGE(2) expressions were up-regulated, whereas OPG expression was down-regulated by Td92. The addition of OPG inhibited Td92-induced osteoclast formation. The prostaglandin synthesis inhibitors NS398 and indomethacin were also shown to inhibit Td92-induced osteoclast formation. The effects of Td92 on the expressions of RANKL, OPG and PGE(2) in osteoblasts were blocked by NS398 or indomethacin.

CONCLUSION

These results suggest that Td92 promotes osteoclast formation through the regulation of RANKL and OPG production via a PGE(2) -dependent mechanism.

Exploring the oral bacterial flora: current status and future directions

OBJECTIVE

The oral cavity forms an indispensable part of the human microbiome, for its unique and diverse microflora distributed within various niches. While majority of these organisms exhibit commensalism, shifts in bacterial community dynamics cause pathological changes within oral cavity and distant sites. The aim of this review was to appraise the current and emerging methods of detecting bacteria of the oral cavity paying particular attention to the cultivation independent methods.

DESIGN

Literature pertaining to cultivation based and cultivation independent methods of oral bacterial identification was reviewed.

METHODS

The specific advantages and disadvantages of cultivation based, microscopic, immunological and metagenomic identification methods were appraised.

RESULTS

Because of their fastidious and exacting growth requirements, cultivation based studies grossly underestimate the extent of bacterial diversity in these polymicrobial infections. Culture independent methods deemed more sensitive in identifying difficult to culture and novel bacterial species.

CONCLUSION

Apart from characterizing potentially novel bacterial species, the nucleic acid sequence data analyzed using various bioinformatics protocols have revealed that there are in excess of 700 bacterial species inhabiting the mouth. Moreover, the latest pyrosequencing based methods have further broadened the extent of bacterial diversity in oral niches.

The major outer membrane protein of a periodontopathogen induces IFN-beta and IFN-stimulated genes in monocytes via lipid raft and TANK-binding kinase 1/IFN regulatory factor-3

Surface molecules of pathogens play an important role in stimulating host immune responses. Elucidation of the signaling pathways activated by critical surface molecules in host cells provides insight into the molecular pathogenesis resulting from bacteria-host interactions. MspTL is the most abundant outer membrane protein of Treponema lecithinolyticum, which is associated with periodontitis, and induces expression of a variety of proinflammatory factors. Although bacteria and bacterial components like LPS and flagellin are known to induce IFN-beta, induction by bacterial surface proteins has not been reported. In the present study, we investigated MspTL-mediated activation of signaling pathways stimulating up-regulation of IFN-beta and IFN-stimulated genes in a human monocytic cell line, THP-1 cells, and primary cultured human gingival fibroblasts. MspTL treatment of the cells induced IFN-beta and the IFN-stimulated genes IFN-gamma-inducible protein-10 (IP-10) and RANTES. A neutralizing anti-IFN-beta Ab significantly reduced the expression of IP-10 and RANTES, as well as STAT-1 activation, which was also induced by MspTL. Experiments using specific small interfering RNA showed that MspTL activated TANK-binding kinase 1 (TBK1), but not inducible IkappaB kinase (IKKi). MspTL also induced dimerization of IFN regulatory factor-3 (IRF-3) and translocation into the nucleus. The lipid rapid-disrupting agents methyl-beta-cyclodextrin, nystatin, and filipin inhibited the MspTL internalization and cellular responses, demonstrating that lipid raft activation was a prerequisite for MspTL cellular signaling. Our results demonstrate that MspTL, the major outer protein of T. lecithinolyticum, induced IFN-beta expression and subsequent up-regulation of IP-10 and RANTES via TBK1/IRF-3/STAT-1 signaling secondary to lipid raft activation.

Laboratory maintenance of Treponema denticola

This unit describes the methods, media, and equipment necessary for routine laboratory culture and handling of the anaerobic oral spirochete Treponema denticola. Topics discussed include nutrient requirements, recommended media formulations, and expected growth kinetics, as well as methods and equipment necessary to maintain anaerobic conditions. An additional protocol on isolation of T. denticola from clinical samples is included.

Identification of a fibronectin-binding protein of Treponema lecithinolyticum by two-dimensional gel electrophoresis and ligand binding assay

Treponema lecithinolyticum is associated with periodontitis and endodontic infections. As a critical early step in the infection process, fibronectin-binding protein (Fbp) is known to be involved in the adhesion of bacteria to cell surfaces for colonization and, hence, is considered to be a virulence factor. In this study, we identified an Fbp from the T. lecithinolyticum cell surface with a molecular mass of about 52 kDa by using 2-dimensional gel electrophoresis followed by a ligand binding assay. As T. lecithinolyticum is capable of binding to soluble and immobilized fibronectin, this Fbp may contribute to bacterial attachment to host cells.

Mapping of the proinflammatory domains of MspTL of Treponema lecithinolyticum

The major surface protein (MspTL) of Treponema lecithinolyticum, associated with periodontitis and endodontic infections, has been reported to induce proinflammatory mediators such as intercellular adhesion molecule (ICAM)-1, and interleukin (IL)-1beta, IL-6 and IL-8. The purpose of this study was to examine the role of MspTL in cell adhesion/migration and to identify its proinflammatory domains. Using the human monocytic cell line THP-1 and human dermal microvascular endothelial cells (HMEC-1), it was demonstrated that MspTL increased adhesion of monocytes to endothelial cells and transendothelial migration. To analyse the proinflammatory domains of the protein, four gene constructs covering different regions of MspTL were designed and expressed in Escherichia coli using the expression vector pQE-30. Histidine-tagged recombinant proteins were purified using Ni-NTA agarose and polymyxin B agarose to remove LPS contamination. Recombinant truncated polypeptides were assessed for the ability to induce ICAM-1 and proinflammatory factors in THP-1 cells by real-time RT-PCR and ELISA. Of the four polypeptides, the one spanning the N-terminal 86 amino acids significantly induced ICAM-1, IL-1beta, IL-6, IL-8, tumour necrosis factor-alpha (TNF-alpha), cyclooxygenase (COX)-2, and prostaglandin E2 (PGE2). The results indicate that MspTL may induce cell adhesion and inflammation via its N-terminal region.

Association of Eubacterium nodatum and Treponema denticola with human periodontitis lesions

BACKGROUND

The purpose of the present investigation was to compare the levels, proportions and percentage of sites colonized by 40 bacterial species in subgingival plaque samples from periodontally healthy subjects and patients with chronic periodontitis to seek possible pathogens other than the consensus pathogens Porphyromonas gingivalis and Tannerella forsythia.

METHOD

Subgingival plaque samples were taken from the mesial aspect of each tooth in 635 subjects with chronic periodontitis and 189 periodontally healthy subjects. The samples were individually analyzed for their content of 40 bacterial species using checkerboard DNA-DNA hybridization (total samples = 21,832). Mean counts, % DNA probe counts and percentage of sites colonized at >10(5) were determined for each species in each subject and then averaged in each clinical group. Significance of difference between groups was determined using the Mann-Whitney test. Association between combinations of species and periodontal status was examined by stepwise logistic regression analysis. Analyses were repeated using a subset of subjects from both clinical groups who had proportions of P. gingivalis plus T. forsythia less than the median (4.42%) found in periodontally healthy subjects. All analyses were adjusted for multiple comparisons.

RESULTS

For the 824 subjects the consensus pathogens P. gingivalis and T. forsythia as well as Eubacterium nodatum and Treponema denticola had significantly higher mean counts, proportions and percentage of sites colonized in samples from subjects with periodontitis than from periodontally healthy subjects. There were significantly more Capnocytophaga gingivalis, Streptococcus gordonii and Veillonella parvula in periodontally healthy subjects. E. nodatum, T. denticola, Streptococcus oralis, Streptococcus intermedius, Fusobacterium nucleatum ssp. vincentii all had higher counts and proportions in diseased than healthy subjects who had low proportions of P. gingivalis and T. forsythia. Logistic regression analysis indicated that the same species groups were associated with disease status after adjusting for the proportions of the other species.

CONCLUSIONS

This investigation confirmed the strong association of P. gingivalis and T. forsythia with chronic periodontitis and emphasized a strong association of E. nodatum and T. denticola with periodontitis whether in the presence or absence of high levels of the consensus pathogens. Other species, including S. oralis, Eikenella corrodens, S. intermedius and F. nucleatum ssp. vincentii, were associated with disease when P. gingivalis and T. forsythia were present in low proportions.

Molecular epidemiology of oral treponemes in patients with periodontitis and in periodontitis-resistant subjects

The etiologic role of oral treponemes in human periodontitis is still under debate. Although seen by dark-field microscopy in large numbers, their possible role is still unclear since they comprise some 60 different phylotypes, most of which are still uncultured. To determine their status as mere commensals or opportunistic pathogens, molecular epidemiological studies are required that include both cultured and as-yet-uncultured organisms. Here we present such data, comparing treponemal populations from chronic periodontitis (CP) or generalized aggressive periodontitis (GAP) patients. As a periodontitis-resistant (PR) control group, we included elderly volunteers with more than 20 natural teeth and no history of periodontal treatment and no or minimal clinical signs of periodontitis. Almost every treponemal phylotype was present in all three groups. For most treponemes, the proportion of subjects positive for a certain species or phylotype was higher in both periodontitis groups than in the PR group. This difference was pronounced for treponemes of the phylogenetic groups II and IV and for Treponema socranskii and Treponema lecithinolyticum. Between the periodontitis groups the only significant differences were seen for T. socranskii and T. lecithinolyticum, which were found more often in periodontal pockets of GAP patients than of CP patients. In contrast, no difference was found for Treponema denticola. Our findings, however, strengthen the hypothesis of treponemes being opportunistic pathogens. It appears that T. socranskii, T. lecithinolyticum and group II and IV treponemes may represent good indicators for periodontitis and suggest the value of the respective probes for microbiological diagnosis in periodontitis subjects.

The metabolism of cholesterol and certain hormonal steroids by Treponema denticola

The aim was to investigate whether reference cultures and fresh isolates of Treponema denticola are able to 5alpha-reduce and further metabolise testosterone, 4-androstenedione, progesterone, corticosterone, cortisol or cholesterol. Two reference and five freshly isolated cultures of T. denticola were incubated with either radiolabeled or unlabeled steroid substrates; in the first case products were identified by thin layer chromatography and in the latter by gas chromatography-mass spectroscopy. All the substrates were 5alpha-reduced. Both reference cultures and fresh isolates of T. denticola presented 3beta- and 17beta-hydroxy steroid dehydrogenase activity. It was concluded that T. denticola was capable of steroid metabolism and hypotheses are discussed regarding the in vivo function of this metabolism including, T. denticola utilising host supplied steroids as growth factors and T. denticola steroid metabolism acting as a virulence factor.

Phenol/water extract of Treponema socranskii subsp. socranskii as an antagonist of Toll-like receptor 4 signalling

Treponema socranskii is one of the most frequently found oral spirochaetes in periodontitis and endodontic infections. LPS or glycolipids from bacteria are potent stimulators of innate immune and inflammatory systems. In this study the bioactivity of a phenol/water extract from T. socranskii subsp. socranskii (TSS-P) was analysed. TSS-P showed minimal endotoxicity and no inducing potential for proinflammatory cytokines (TNF-α and IL-8) or for intercellular adhesion molecule-1 (ICAM-1) in human monocyte cell line THP-1 cells and primary cultured human gingival fibroblasts. Rather, it inhibited ICAM-1 expression and IL-8 secretion from cells stimulated by the LPS of Escherichia coli and Actinobacillus actinomycetemcomitans, which are known to be Toll-like receptor 4 (TLR4) agonists. However, this antagonistic activity was not shown in cells stimulated by peptidoglycan or IL-1β. As its antagonistic mechanism, TSS-P blocked the binding of E. coli LPS to LPS-binding protein (LBP) and CD14, which are molecules involved in the recruitment of LPS to the cell membrane receptor complex TLR4–MD-2 for the intracellular signalling of LPS. TSS-P itself did not bind to MD-2 or THP-1 cells, but inhibited the binding of E. coli LPS to MD-2 or to the cells in the presence of serum (which could be replaced by recombinant human LBP and recombinant human CD14). The results suggest that TSS-P acts as an antagonist of TLR4 signalling by interfering with the functioning of LBP/CD14.

Treponema berlinense sp. nov. and Treponema porcinum sp. nov., novel spirochaetes isolated from porcine faeces

Limit-dilution procedures were used to isolate seven, helically coiled bacterial strains from faeces of swine that constituted two unidentified taxa. Comparative 16S rRNA gene sequence analysis showed highest similarity values with species of the genus Treponema indicating that the isolates are members of this genus. Strain 7CPL208(T), as well as five further isolates, and 14V28(T) displayed the highest 16S rRNA gene sequence similarities with Treponema pectinovorum ATCC 33768(T) (92.3%) and Treponema parvum OMZ 833(T) (89.9%), respectively. Polar lipid profiles distinguished 7CPL208(T) and 14V28(T) from each other as well as from related species. Based on their phenotypic and genotypic distinctiveness, strains 7CPL208(T) and 14V28(T) are suggested to represent two novel species of the genus Treponema, for which the names Treponema berlinense sp. nov. and Treponema porcinum sp. nov. are proposed. The type strain for Treponema berlinense is 7CPL208(T) (=ATCC BAA-909(T)=CIP 108244(T)=JCM 12341(T)) and for Treponema porcinum 14V28(T) (=ATCC BAA-908(T)=CIP 108245(T)=JCM 12342(T)).

Molecular analysis of human oral microbiota

OBJECTIVES

The application of molecular, mainly 16S ribosomal RNA (rRNA)-based approaches enables researchers to bypass the cultivation step and has proven its usefulness in studying the microbial composition in a variety of ecosystems, including the human oral cavity. In this mini-review, we describe the impact of these culture-independent approaches on our knowledge of the ecology of the human oral cavity and provide directions for future studies that should emphasize the role of specific strains, species and groups of microbes in periodontal disease.

MATERIALS AND METHODS

Recent findings are summarized to elucidate the relationship between periodontal disease and human oral microbiota, including as-yet-to-be-cultured organisms.

RESULTS

The real-time polymerase chain reaction (PCR) method was developed to detect and quantify periodontopathic bacteria, such as Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis (formerly Bacteroides forsythus) and Treponema denticola. The checkerboard DNA-DNA hybridization technique allowed enumeration of large numbers of species in very large numbers of samples. 16S rRNA gene clone library analysis revealed the diversity of human oral microbiota and the existence of as-yet-to-be-cultured organisms that are presumed periodontal pathogens. In addition, terminal restriction fragment length polymorphism (T-RFLP) analysis was applied for assessment of diversity of human oral microbiota.

CONCLUSION

Culture-independent approaches are useful for studying the microbial ecology in the human oral cavity and should be useful in the future to elucidate the etiology of periodontal disease.

Upregulation of intercellular adhesion molecule 1 and proinflammatory cytokines by the major surface proteins of Treponema maltophilum and Treponema lecithinolyticum, the phylogenetic group IV oral spirochetes associated with periodontitis and endodontic infections

Treponema maltophilum and Treponema lecithinolyticum belong to the group IV oral spirochetes and are associated with endodontic infections, as well as periodontitis. Recently, the genes encoding the major surface proteins (Msps) of these bacteria (MspA and MspTL, respectively) were cloned and sequenced. The amino acid sequences of these proteins showed significant similarity. In this study we analyzed the functional role of these homologous proteins in human monocytic THP-1 cells and primary cultured periodontal ligament (PDL) cells using recombinant proteins. The complete genes encoding MspA and MspTL without the signal sequence were cloned into Escherichia coli by using the expression vector pQE-30. Fusion proteins tagged with N-terminal hexahistidine (recombinant MspA [rMspA] and rMspTL) were obtained, and any possible contamination of the recombinant proteins with E. coli endotoxin was removed by using polymyxin B-agarose. Flow cytometry showed that rMspA and rMspTL upregulated the expression of intercellular adhesion molecule 1 (ICAM-1) in both THP-1 and PDL cells. Expression of proinflammatory cytokines, such as interleukin-6 (IL-6) and IL-8, was also induced significantly in both cell types by the Msps, as determined by reverse transcription-PCR and an enzyme-linked immunosorbent assay, whereas IL-1beta synthesis could be detected only in the THP-1 cells. The upregulation of ICAM-1, IL-6, and IL-8 was completely inhibited by pretreating the cells with an NF-kappaB activation inhibitor, l-1-tosylamido-2-phenylethyl chloromethyl ketone. This suggests involvement of NF-kappaB activation. The increased ICAM-1 and IL-8 expression in the THP-1 cells obtained with rMsps was not inhibited in the presence of the IL-1 receptor antagonist (IL-1ra), a natural inhibitor of IL-1. Our results show that the Msps of the group IV oral spirochetes may play an important role in amplifying the local immune response by continuous inflammatory cell recruitment and retention at an infection site by stimulation of expression of ICAM-1 and proinflammatory cytokines.

Treponema putidum sp. nov., a medium-sized proteolytic spirochaete isolated from lesions of human periodontitis and acute necrotizing ulcerative gingivitis

So far, little phenotypic heterogeneity has been detected in cultured oral treponemes with trypsin-like proteolytic activity, and all have been assigned to the species Treponema denticola. However, comparisons of protein patterns and antigen expression in our collection of proteolytic oral treponemes occasionally identified isolates with a unique phenotype; e.g. strain OMZ 830 (=ATCC 700768), which qualified as a ‘pathogen-related oral spirochaete’ due to the presence of a ∼37 kDa protein reactive with the Treponema pallidum FlaA-specific mAb H9-2. In addition to such single isolates, a homogeneous group of seven independent strains is described that were highly motile, medium-sized, proteolytic but asaccharolytic spirochaetes and were cultured from human gingivitis, periodontitis and acute necrotizing ulcerative gingivitis in medium OMIZ-Pat supplemented with 1 % human serum and antibiotics. Growth of these spirochaetes in OMIZ-Pat was not dependent on, but was stimulated by, human or bovine serum. Carbohydrates were neither required nor stimulatory for growth. The protein and antigen patterns of total cell extracts of these organisms separated by SDS-PAGE were distinct from those of all previously cultured spirochaetes, with highest similarity to T. denticola. The novel spirochaete has a 2 : 4 : 2 arrangement of the periplasmic flagella, similar to T. denticola. However, the flagellin pattern as detected by immunostaining or glycan staining of Western blots readily distinguished the novel group from T. denticola. Also, distinct from reference strains of T. denticola, none of the novel isolates displayed sialidase or dentilisin activities, both of which are expressed by most strains of T. denticola. Trypsin-like activity and other enzymes as detected by API ZYM test were similar to those of T. denticola. The status of a novel species is supported by the 16S rRNA gene sequence, with 98·5 % similarity to its closest cultured relative, T. denticola. The name Treponema putidum sp. nov. is proposed (type strain OMZ 758T=ATCC 700334T=CIP 108088T).

Taxonomic changes of bacteria associated with endodontic infections

There have been major recent reorganizations among bacterial taxa as a result of phylogenetic taxonomic approaches. As a consequence, old species have been renamed and novel species have been proposed. The introduction of molecular technology for microbial identification has also allowed the detection of microbial taxa never previously found in endodontic infections. Therefore, the list of putative endodontic pathogens is frequently changing and expanding. The purpose of this review is twofold: to cover the taxonomic changes that the major putative endodontic pathogens have undergone in the recent years and to compile data from studies regarding the detection of known or novel bacterial species that had been only recently reported to occur in endodontic infections.

Two paralogous families of a two-gene subtilisin operon are widely distributed in oral treponemes

Certain oral treponemes express a highly proteolytic phenotype and have been associated with periodontal diseases. The periodontal pathogen Treponema denticola produces dentilisin, a serine protease of the subtilisin family. The two-gene operon prcA-prtP is required for expression of active dentilisin (PrtP), a putative lipoprotein attached to the treponeme's outer membrane or sheath. The purpose of this study was to examine the diversity and structure of treponemal subtilisin-like proteases in order to better understand their distribution and function. The complete sequences of five prcA-prtP operons were determined for Treponema lecithinolyticum, "Treponema vincentii," and two canine species. Partial operon sequences were obtained for T. socranskii subsp. 04 as well as 450- to 1,000-base fragments of prtP genes from four additional treponeme strains. Phylogenetic analysis demonstrated that the sequences fall into two paralogous families. The first family includes the sequence from T. denticola. Treponemes possessing this operon family express chymotrypsin-like protease activity and can cleave the substrate N-succinyl-alanyl-alanyl-prolyl-phenylalanine-p-nitroanilide (SAAPFNA). Treponemes possessing the second paralog family do not possess chymotrypsin-like activity or cleave SAAPFNA. Despite examination of a range of protein and peptide substrates, the specificity of the second protease family remains unknown. Each of the fully sequenced prcA and prtP genes contains a 5' hydrophobic leader sequence with a treponeme lipobox. The two paralogous families of treponeme subtilisins represent a new subgroup within the subtilisin family of proteases and are the only subtilisin lipoprotein family. The present study demonstrated that the subtilisin paralogs comprising a two-gene operon are widely distributed among treponemes.

Distribution of Periodontal Pathogens in Korean Aggressive Periodontitis

BACKGROUND

Microbial associations in aggressive periodontitis versus different ethnic origins are substantially unknown. We undertook this study to determine the prevalence of seven putative periodontopathogens in Korean patients and to evaluate microbial differences in localized and generalized aggressive periodontitis patients.

METHODS

Thirty-nine aggressive periodontitis patients between 20 and 35 years old (24 males and 15 females; mean age 29.6 years) were selected according to clinical criteria. The patients were subclassified into 17 localized and 22 generalized aggressive periodontitis patients. In each of the 39 individuals, subgingival plaque samples were collected from four diseased teeth (> or = 6 mm probing depth, 156 sites) and one healthy site (< or = 3 mm probing depth, 39 sites). Polymerase chain reaction (PCR) of the 16S ribosomal RNA gene fragments (about 530 bp) of plaque bacteria and their subsequent detection by dot-blot hybridization using specific oligonucleotide probes were performed to determine the presence of seven periodontopathogens.

RESULTS

The prevalences were 75% for Actinobacillus actinomycetemcomitans, 94.2% for Tannerella forsythensis (formerly Bacteroides forsythus), 99.4% for Fusobacterium sp., 85.9% for Micromonas micros (formerly Peptostreptococcus micros), 96.8% for Porphyromonas gingivalis, 78.8% for Prevotella intermedia, and 96.8% for Treponema sp. The prevalences of these bacteria were significantly higher in diseased sites than in healthy sites. Logistic regression analysis showed that P. intermedia was more significantly associated with generalized aggressive periodontitis than the localized form, with an odds ratio of 3.28 (95% confidence interval 1.26-8.56, P = 0.015).

CONCLUSIONS

Our results demonstrate that the seven periodontal pathogens analyzed are strongly associated with Korean aggressive periodontitis. In particular, P. intermedia are more significantly associated with generalized aggressive periodontitis, a more severe and progressive form, than with localized aggressive periodontitis.

PCR-based identification of Treponema maltophilum, T amylovorum, T medium, and T lecithinolyticum in primary root canal infections

OBJECTIVE

Molecular genetic methods have significantly contributed to the knowledge about the microbiota associated with infected root canals. Albeit spirochetes have been commonly observed in primary root canal infections, only recently they have been identified. The purpose of the present study was to investigate the occurrence of four treponemes-Treponema maltophilum, Treponema lecithinolyticum, Treponema amylovorum, and Treponema medium-in cases of primary endodontic infections associated with different forms of periradicular diseases through a 16S rDNA-based nested PCR assay.

DESIGN

Samples were taken from thirty-one infected root canals associated with either asymptomatic or symptomatic apical periodontitis. DNA extracted from the samples was initially amplified using universal 16S rDNA primers, followed by a second round of amplification using the first PCR products to detect a specific fragment of the 16S rDNA of each target Treponema species.

RESULTS

All cases were positive for the universal bacterial primers, indicating that samples contained bacterial DNA. Of the four target species, T. maltophilum was the most prevalent, being detected in 39% of the cases (33% of the asymptomatic cases and 50% of the symptomatic cases). T. lecithinolyticum was the next more prevalent among the species tested, being found in 26% of the samples (33% of asymptomatic cases and 10% of the symptomatic cases). T. amylovorum was found in 7% of the cases (5% of the asymptomatic cases and 10% of the symptomatic cases), while T. medium was in 13% of the cases (14% of the asymptomatic cases and 10% of the symptomatic cases). None of the species tested was significantly associated with clinical symptoms.

CONCLUSIONS

This was possibly the hitherto first study to report the occurrence of T. lecithinolyticum, T. amylovorum, and T. medium in infections of endodontic origin. Overall, findings suggested that these oral treponemes, particularly T. maltophilum and T. lecithinolyticum, can be involved in the pathogenesis of periradicular diseases.

Inhibitory effect of procyanidin oligomer from elm cortex on the matrix metalloproteinases and proteases of periodontopathogens

OBJECTIVES

The purpose of this study was to evaluate a partially purified extract (elm extract) from the Ulmi cortex (Ulmi macrocarpa Hance) and its active ingredient, a mix of procyanidin oligomers (3 to 12 flavan-3-ol monomers, an average molecular weight of 1,518 with an average polymerization degree of 5.3) for a possible inhibitory effect against proteases.

BACKGROUND

Host-derived matrix metalloproteinases (MMPs) and bacterial proteases play important roles in the gingival tissue destruction that is a characteristic of periodontitis. The inhibitors of these proteases may be developed into therapeutic agents against periodontitis.

METHODS

The inhibitory effects were assessed by gelatin zymography. The MMPs tested were originated from the gingival crevicular fluid (GCF) of adult periodontitis patients and from the conditioned media of cultured periodontal ligament (PDL) cells, which provided the proMMP-2 and activated MMP-2 when treated with a periodontopathogen, Treponema lecithinolyticum. Bacterial enzymes tested were secreted forms from two major periodontopathogens, Porphyromonas gingivalis and Treponema denticola. In addition, the inhibitory effects on trypsin-like enzymes from these two periodontopathogens were assayed by the n-benzoyl-DL-arginine-naphthylamide (BANA) test.

RESULTS

The elm extract and the procyanidin oligomer (100-1,000 microg/ml) exhibited potent inhibitory effects on the MMPs in GCF (chiefly MMP-8 and MMP-9), the pro and active forms of MMP-2, and secreted and trypsin-like enzymes from T. denticola and P. gingivalis.

CONCLUSIONS

These results suggest that elm cortex should be considered as a potential agent against periodontal diseases, due to its inhibitory action on MMPs and the proteases of periodontopathogens.

New bacterial species associated with chronic periodontitis

Recent investigations of the human subgingival oral flora based on ribosomal 16S cloning and sequencing have shown many of the bacterial species present to be novel species or phylotypes. The purpose of the present investigation was to identify potential periodontal pathogens among these newly identified species and phylotypes. Species-specific ribosomal 16S primers for PCR amplification were developed for detection of new species. Associations with chronic periodontitis were observed for several new species or phylotypes, including uncultivated clones D084 and BH017 from the Deferribacteres phylum, AU126 from the Bacteroidetes phylum, Megasphaera clone BB166, clone X112 from the OP11 phylum, and clone I025 from the TM7 phylum, and the named species Eubacterium saphenum, Porphyromonas endodontalis, Prevotella denticola, and Cryptobacterium curtum. Species or phylotypes more prevalent in periodontal health included two uncultivated phylotypes, clone W090 from the Deferribacteres phylum and clone BU063 from the Bacteroidetes, and named species Atopobium rimae and Atopobium parvulum.

Amended biochemical characteristics and phylogenetic position of Treponema medium

Umemoto et al. (1997, Int J Syst Bacteriol 47, pp. 67-72) proposed spirochete strain G7201, isolated from the periodontal pocket of an adult patient, as a new species, Treponema medium. They deposited this strain in the American Type Culture Collection (ATCC) as type strain ATCC 700293T. Recently, ATCC suggested that there is a discrepancy between the previous report and the results obtained by ATCC in biochemical tests on T. medium ATCC 700293T. In this study, we re-examined and verified the biochemical characteristics of T. medium. The fermentation pattern of carbohydrates of T. medium resembled that of Treponema vincentii and Treponema denticola, but T. medium was clearly differentiated from T. vincentii in the production of indole, and from T. denticola in the hydrolysis of esculin. Also, sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) protein profile analysis and phylogenetic comparison of 16S rDNA sequences revealed that T. medium is clearly differentiated from any established treponemal species, which supports the validity of the proposal of Treponema medium as a new species.

Cloning and characterization of a major surface protein (MspTL) of Treponema lecithinolyticum associated with rapidly progressive periodontitis

The gene encoding a major surface protein (MspTL) of Treponema lecithinolyticum, a periodontopathogen, was cloned and sequenced. The mspTL gene has a 1770-bp open reading frame (ORF) encoding a protein of 590 amino acids with a predicted molecular mass of 65 kDa which had a typical prokaryotic signal sequence (19 amino acids). MspTL showed a high level of homology with major sheath protein (MspA) of Treponema maltophilum, phylogenetically the closest relative of T. lecithinolyticum. Southern blot analysis indicated that the mspTL gene exists in a single copy and Northern blot analysis showed that the mspTL transcript is monocistronic. Another ORF located downstream of mspTL was in the same orientation and encoded a putative protein, in which the first N-terminal 291 amino acids were identified. The homologous region of this protein is also a part on the T. maltophilum mspA locus.

Activation of matrix metalloproteinase-2 by a novel oral spirochetal species Treponema lecithinolyticum

BACKGROUND

Periodontal tissue destruction is a characteristic of periodontitis. This can be caused by either bacterial enzymes or host cell-derived matrix metalloproteinases (MMPs). In order to elucidate the etiologic role of oral spirochetes, we investigated the effects of Treponema lecithinolyticum, a novel saccharolytic species, on MMP-2 activation.

METHODS

Gingival fibroblasts (GFs) and periodontal ligament (PDL) cells obtained from healthy human subjects were cultured to confluence in alpha-minimal essential medium (alpha-MEM) supplemented with 10% fetal bovine serum. After serum starvation for a day, the cultures were treated with whole cell sonicates, heat-denatured whole cell sonicates, outer membrane fraction (OMF) or formaldehyde-fixed cells of T. lecithinolyticum. Culture supernatants were collected after incubation for 24 to 48 hours and analyzed for MMP-2 activation by gelatin zymography. Collagenolytic activity was quantitatively measured using human [3H] type IV collagen as a substrate.

RESULTS

Treatment of GFs and PDL cells with whole cell sonicates, formaldehyde-fixed whole cells, or the OMF of T. lecithinolyticum resulted in the production of MMP-2 partly in the fully active form with a molecular mass of 62 kDa, whereas non-treated control cultures and cultures treated with a heat-denatured fraction did not show the active form. Cultures exposed to T. lecithinolyticum had higher collagenolytic activity than non-treated cultures.

CONCLUSIONS

Our results demonstrate that T. lecithinolyticum, possibly mediated by proteinaceous cell surface-associated components, may participate in extracellular matrix degradation by activation of MMP-2 during periodontal inflammation.

Effects of whole cell sonicates of Treponema lecithinolyticum on osteoclast differentiation

BACKGROUND

Alveolar bone destruction is a characteristic feature of periodontal diseases and multinucleated osteoclast cells derived from hemopoietic cells are responsible for bone resorption. Treponema lecithinolyticum is a novel oral spirochete isolated from the periodontal lesions.

METHODS

The effect of whole cell sonicates on the osteoclast differentiation was examined in a co-culture system of hemopoietic mouse bone marrow cells and calvaria derived-osteoblastic cells to clarify the role of T. lecithinolyticum in the alveolar bone destruction associated with periodontal diseases. The differentiated osteoclasts were confirmed by tartrate-resistant acid phosphatase (TRAP) staining.

RESULTS

Sonicates of this bacterium stimulated the osteoclast formation in the co-culture system in a dose-dependent manner. The sonicates-induced osteoclast formation was partially inhibited by the heat treatment of sonicates. Indomethacin, which is a prostaglandin inhibitor, decreased the osteoclast formation induced by the bacterial sonicates.

CONCLUSIONS

These findings suggest that T. lecithinolyticum induces osteoclast differentiation by a prostaglandin E2-dependent mechanism and that heat-labile components may be involved in this process.

Identification of oral spirochetes at the species level and their association with other bacteria in endodontic infections

OBJECTIVES

Recent molecular approaches have revealed that fastidious organisms such as Bacteroides forsythus and oral treponemes were frequently found in root canals with apical periodontitis. The purpose of this study was to identify the isolates of oral spirochetes at the species level in endodontic infections and to determine their association with B forsythus and Porphyromonas gingivalis.

STUDY DESIGN

Seventy-nine teeth with apical periodontitis were selected for this study. After sampling from the root canals aseptically, polymerase chain reaction amplification for the 16S rRNA gene was performed with eubacterial universal primers. Subsequently, dot-blot hybridization was performed with 8 species-specific oligonucleotide probes. The microbial associations were analyzed by using the odds ratio.

RESULTS

The most frequently found species was P gingivalis (27.4%), followed by Treponema maltophilum (26%), B forsythus (16.4%), and Treponema socranskii (2.7%). Other treponemes, including Treponema denticola, were not detected in our samples. Significant microbial associations were identified between T maltophilum, B forsythus, and P gingivalis by performing analysis with the odds ratio.

CONCLUSION

Our results indicate that T maltophilum should be included in etiologic studies of endodontic diseases.