Pathogen-related spirochetes identified within gingival tissue from patients with acute necrotizing ulcerative gingivitis

Acute Necrotizing Ulcerative Gingivitis: A Case Report

Compared to other conditions found in the necrotizing periodontal diseases group, acute necrotizing ulcerative gingivitis (ANUG) is a definite and specific disease. This illness has a long history that originates from the time of Hippocrates and is also referred to by several synonyms. ANUG occurs less commonly than other oral disorders, even though it is typically not rare. It starts suddenly, advances quickly, and finally results in significant loss of alveolar bone and soft tissue. Viral microorganisms and weakened host defenses have been linked to the etiology and pathophysiology of ANUG. In situations where there is psychological and physiological stress, the incidence of ANUG rises. In developed nations, the incidence of ANUG has declined and, in some cases, gone extinct due to the development of antibiotics and improved nutritional status. However, due to the persistently low nutritional status, the illness continues to be a frequently diagnosed clinical lesion in developing nations. This case report presents the case of a 24-year-old ANUG patient and the sequential treatment of this patient.

Detection of Pathogen-Related Oral Spirochetes, Treponema denticola, and Treponema socranskii in Dental Plaque from Dogs

Spirochetes have been observed in dental plaque from dogs, but specific spirochetes have not been identified. In particular, it is not known whether treponemes associated with periodontal diseases in humans also occur in dogs, and whether, like in humans, detection of specific treponemes correlates with periodontal status of dogs. Forty-two dogs were grouped according to the worst periodontal condition in the mouth, as determined by overt signs of inflammation and pocket probing depths. A representative specimen of dental plaque was obtained by pooling subgingival plaque collected from three uniform reference sites, irrespective of periodontal status at selected sites. The presence of pathogen-related oral spirochetes, Treponema denticola, and T. socranskii was determined using specific monoclonal antibodies in an immunocytochemical microscopic assay. All three treponemes were detected in all groups, but a significantly greater proportion of dogs with pocket probing depths ≥5 mm had detectable treponemes, compared to dogs that were in periodontal health.

Treponema medium Glycoconjugate Inhibits Activation of Human Gingival Fibroblasts Stimulated with Phenol-Water Extracts of Periodontopathic Bacteria

Oral treponemes are well-known as causative agents of periodontal diseases; however, the details have not been fully clarified. Here, we examined the effects of Treponema medium glycoconjugate on the activation of human gingival fibroblasts using phenol-water extracts from Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum subsp. nucleatum, and Actinobacillus actinomycetemcomitans. The phenol-water extracts activated human gingival fibroblasts to mediate IL-8 production, as well as IL-8 mRNA expression, phosphorylation of p38 mitogen-activated protein kinase, and expression of intercellular adhesion molecule-1. T. medium glycoconjugate exhibited no activation of human gingival fibroblasts, while phenol-water extract-induced activation of human gingival fibroblasts was clearly inhibited by T. medium glycoconjugate. Furthermore, binding of biotinylated phenol-water extracts to CD14 in the presence of LPS-binding protein was blocked with T. medium glycoconjugate. These results suggest that T. medium glycoconjugate has an inhibitory effect on host cell activation by periodontopathic bacteria caused by binding to CD14- and LPS-binding protein.

Relationship between invasion of the periodontium by periodontal pathogens and periodontal disease: a systematic review

Bacterial invasion of the periodontal tissues has been suggested as a relevant step in the etiopathogenesis of periodontal disease. However, its exact importance remains to be defined. The present systematic review assessed the scientific evidence concerning the relationship between the quality or quantity of periodontal microbiota in periodontal tissues and development of periodontal disease. The databases Medline-PubMed, Cochrane-CENTRAL, ISI Web of Knowledge and SCOPUS were searched, up to January 2014. Studies that reported evaluation of periodontal pathogens invasion on human tissues were selected. The screening of 440 title/abstracts elected 26 papers for full-text reading. Twenty three papers were subsequently excluded because of insufficient data or a study protocol not related to the objectives of this systematic review. All included studies were case-control studies that evaluated intracellular or adherent bacteria to epithelial cells from periodontal pockets versus healthy sulci. Study protocols presented heterogeneity regarding case and control definitions and methodological approaches for microbial identification. No consistent significant differences were found related to the presence/absence or proportion of specific periopathogens across the studies, as only one study found statistically significant differences regarding the presence of A. actinomycetemcomitans (p = 0.043), T. forsythia (P < 0.001), P. intermedia (P < 0.001), C. ochracea (P < 0.001) and C. rectus (P = 0.003) in epithelial cells from periodontal pockets vs. healthy sulci. All studies reported a larger unspecific bacterial load in or on the epithelial cells taken from a diseased site compared to a healthy sulcus. The current available data is of low to moderate quality and inconsistent mainly due to study design, poor reporting and methodological diversity. As so, there is insufficient evidence to support or exclude the invasion by periodontal pathogens as a key step in the etiopathogenesis of periodontal disease. Further research is needed.

Oral cavity contains distinct niches with dynamic microbial communities

Microbes colonize human oral surfaces within hours after delivery. During postnatal development, physiological changes, such as the eruption of primary teeth and replacement of the primary dentition with permanent dentition, greatly alter the microbial habitats, which, in return, may lead to community composition shifts at different phases in people's lives. By profiling saliva, supragingival and mucosal plaque samples from healthy volunteers at different ages and dentition stages, we observed that the oral cavity is a highly heterogeneous ecological system containing distinct niches with significantly different microbial communities. More importantly, the phylogenetic microbial structure varies with ageing. In addition, only a few taxa were present across the whole populations, indicating a core oral microbiome should be defined based on age and oral niches.

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.

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.

Oral treponemes and their outer membrane extracts activate human gingival epithelial cells through toll-like receptor 2

Oral treponemes are considered to be important in the development and progression of periodontal diseases. We investigated the mechanisms of recognition and activation of human gingival epithelial cells (HGEC) with the oral treponemes Treponema denticola, Treponema vincentii, and Treponema medium and their outer membrane extracts (OMEs). T. vincentii and T. medium but not T. denticola produced interleukin 8 (IL-8) in an HGEC culture. Further, all three treponemes induced IL-8 mRNA expression and NF-kappaB activation in HGEC. Among them, T. denticola especially exhibited trypsin- and chymotrypsin-like protease activities, and the addition of chymostatin, a chymotrypsin protease inhibitor, resulted in detectable IL-8 production by HGEC cultured with T. denticola. Additionally, IL-8 mRNA expression in HGEC cultured with the three treponemes and their OMEs was definitely inhibited by the mouse anti-human Toll-like receptor 2 (TLR2) monoclonal antibody TL2.1. These findings suggest that oral treponemes and their OMEs activate HGEC through TLR2.

Detection and quantification of oral treponemes in subgingival plaque by real-time PCR

Oral treponemes have been associated with periodontal diseases. We developed a highly sensitive and specific method to detect and quantify cultivable oral treponemes (Treponema denticola, Treponema vincentii, and Treponema medium) in 50 subgingival plaque samples from 13 healthy subjects as well as 37 patients with periodontal diseases using real-time PCR assays with specific primers and a TaqMan probe for each 16S rRNA sequence. The specificity for each assay was examined by using DNA specimens from various treponemal and other bacterial species. The TaqMan real-time PCR was able to detect from 10(3) to 10(8) cells of the oral treponemes, with correlation coefficients as follows: T. denticola, 0.984; T. vincentii, 0.991; and T. medium, 0.984. The frequencies of occurrence of these three oral treponemes in subgingival plaque samples were as follows: T. denticola, 68.0%; T. vincentii, 36.0%; and T. medium, 48.0%. In addition, the number of T. denticola, T. vincentii, and T. medium cells in plaque samples detected by real-time PCR ranged from 3 to 15,184, 1 to 447, and 1 to 7,301 cells/pg of plaque DNA, respectively. Increased numbers of T. denticola cells were detected in plaque samples from deep periodontal pockets, and T. medium was also detected in deep pockets. On the other hand, T. vincentii was mainly found in shallow pockets. These results suggest that various oral treponemes are associated with the formation of each stage of periodontal disease.

Molecular and immunological evidence of oral Treponema in the human brain and their association with Alzheimer's disease

The purpose of this investigation was to use molecular and immunological techniques to determine whether oral Treponema infected the human brain. Pieces of frontal lobe cortex from 34 subjects were analyzed with species-specific PCR and monoclonal antibodies. PCR detected Treponema in 14/16 Alzheimer's disease (AD) and 4/18 non-AD donors (P < 0.001), and AD specimens had more Treponema species than controls (P < 0.001). PCR also detected Treponema in trigeminal ganglia from three AD and two control donors. Cortex from 15/16 AD subjects and 6/18 controls contained Treponema pectinovorum and/or Treponema socranskii species-specific antigens (P < 0.01). T. pectinovorum and/or T. socranskii antigens were also found in trigeminal ganglia and pons from four embalmed cadavers, and 2/4 cadavers also had Treponema in the hippocampus. These findings suggest that oral Treponema may infect the brain via branches of the trigeminal nerve.

Periodontal disease as a specific, albeit chronic, infection: diagnosis and treatment

Periodontal disease is perhaps the most common chronic infection in adults. Evidence has been accumulating for the past 30 years which indicates that almost all forms of periodontal disease are chronic but specific bacterial infections due to the overgrowth in the dental plaque of a finite number of mostly anaerobic species such as Porphyromonas gingivalis, Bacteroides forsythus, and Treponema denticola. The success of traditional debridement procedures and/or antimicrobial agents in improving periodontal health can be associated with the reduction in levels of these anaerobes in the dental plaque. These findings suggest that patients and clinicians have a choice in the treatment of this overgrowth, either a debridement and surgery approach or a debridement and antimicrobial treatment approach. However, the antimicrobial approach, while supported by a wealth of scientific evidence, goes contrary to centuries of dental teaching that states that periodontal disease results from a "dirty mouth." If periodontal disease is demonstrated to be a risk factor for cardiovascular disease and stroke, it will be a modifiable risk factor since periodontal disease can be prevented and treated. Since the antimicrobial approach may be as effective as a surgical approach in the restoration and maintenance of a periodontally healthy dentition, this would give a cardiac or stroke patient and his or her physician a choice in the implementation of treatment seeking to improve the patient's periodontal condition so as to reduce and/or delay future cardiovascular events.

Activation of mitogen-activated protein kinases p42/44, p38, and stress-activated protein kinases in myelo-monocytic cells by Treponema lipoteichoic acid

We have shown previously that phenol/water extracts derived from two novel Treponema species, Treponema maltophilum, and Treponema brennaborense, resembling lipoteichoic acid (LTA), induce cytokines in mononuclear cells. This response was lipopolysaccharide binding-protein (LBP)-dependent and involved Toll-like receptors (TLRs). Here we show that secretion of tumor necrosis factor-alpha induced by Treponema culture supernatants and extracted LTA was paralleled by an LBP-dependent phosphorylation of mitogen-activated protein kinases (MAPKs) p42 and p44, and p38, as well as the stress-activated protein kinases c-Jun N-terminal kinases 1 and 2. Phosphorylation of p42/44 correlated with an increase of activity, and tumor necrosis factor-alpha levels were significantly reduced by addition of inhibitors of p42/44 and p38, PD 98059 and SB 203580, respectively. Treponeme LTA differed from bacterial lipopolysaccharide regarding time course of p42/44 phosphorylation, exhibiting a prolonged activation of MAPKs. Furthermore, MAPK activation and cytokine induction failed to be strictly correlated. Involvement of TLR-4 for phosphorylation of p42/44 was shown employing the neutralizing anti-murine TLR-4 antibody MTS 510. In TLR-2-negative U373 cells, the compounds studied differed regarding MAPK activation with T. maltophilum leading to a stronger activation. In summary, the data presented here show that treponeme LTA are able to activate the MAPK and stress-activated protein kinase pathway involving LBP and TLR-4.

Polymerase chain reaction for the detection of flaA-1 genes of oral spirochaetes in human advanced periodontal pockets

A novel group of oral spirochaetes that were specifically labeled by H9-2, a monoclonal antibody against the 37-kDa endoflagellar sheath protein of Treponema pallidum, have earlier been demonstrated in periodontitis-associated plaque samples; two cultivable oral spirochaetes T. vincentii and T. medium displayed cross-reactivity with that monoclonal, but the molecular basis for this cross-reactivity is not yet defined. Here, the flaA-1 genes which encode the 37-kDa sheath protein from T. vincentii and the oral spirochaetes present in samples from advanced periodontitis were examined. A 856 bp fragment of the flaA-1 gene was amplified in T. pallidum and T. vincentii. The same-size polymerase chain reaction fragments were also amplified in two clinical samples from patients with advanced periodontitis but not from samples of healthy plaque. The sequences of the flaA-1 genes of the oral spirochaetes detected in human periodontal plaque were closely similar to those of T. pallidum and T. vincentii, but neither of these two organisms could be detected in these samples using rRNA-specific primers. The identity of the flaA-1 positive spirochaetes associated with periodontitis remains to be determined.

Involvement of lipopolysaccharide binding protein, CD14, and Toll-like receptors in the initiation of innate immune responses by Treponema glycolipids

Culture supernatants from Treponema maltophilum associated with periodontitis in humans and Treponema brennaborense found in a bovine cattle disease accompanied with cachexia caused a dose-dependent TNF-alpha synthesis in human monocytes increasing with culture time. This activity could be reduced significantly by blocking the CD14-part of the LPS receptor using the My 4 mAb and by polymyxin B. In the murine macrophage cell line RAW 264.7, Treponema culture supernatants induced TNF-alpha secretion in a LPS binding protein (LBP)-dependent fashion. To enrich for active compounds, supernatants were extracted with butanol, while whole cells were extracted using a phenol/water method resulting in recovery of material exhibiting a similar activity profile. An LPS-LBP binding competition assay revealed an interaction of the treponeme phenol/water extracts with LBP, while precipitation studies implied an affinity to polymyxin B and endotoxin neutralizing protein. Macrophages obtained from C3H/HeJ mice carrying a Toll-like receptor (TLR)-4 mutation were stimulated with treponeme extracts for NO release to assess the role of TLRs in cell activation. Furthermore, NF-kappaB translocation in TLR-2-negative Chinese hamster ovary (CHO) cells was studied. We found that phenol/water-extracts of the two strains use TLRs differently with T. brennaborense-stimulating cells in a TLR-4-dependent fashion, while T. maltophilum-mediated activation apparently involved TLR-2. These results indicate the presence of a novel class of glycolipids in Treponema initiating inflammatory responses involving LBP, CD14, and TLRs.

The diversity of periodontal spirochetes by 16S rRNA analysis

The purpose of this study was to examine the diversity of spirochetes in the subgingival pocket of multiple subjects with a range of periodontal conditions, including two healthy, one adult periodontitis, three acute necrotizing ulcerative gingivitis, eight refractory periodontitis, and one human immunodeficiency virus (HIV) periodontitis. The 16S rRNA genes of spirochetes in plaque were amplified by polymerase chain reaction using spirochete selective primers. Over 500 clones were sequenced and subjected to phylogenetic analysis. The sequences clustered into the 10 known cultivated Treponema species and into 47 as-yet-uncultivated Treponema species. Most of these Treponema species were identified from multiple clones and subjects. The human periodontal pocket harbors a highly diverse treponeme population. Of the cultivated species, Treponema denticola, Treponema maltophilum and Treponema sp. Smibert-3 were most commonly encountered in diseased subjects but rarely in healthy subjects. Molecular tools based on the sequence data from this study will allow determination of the prevalence of cultivable and uncultivable treponemes in oral diseases.

Taxonomy and virulence of oral spirochetes

All oral spirochetes are classified in the genus Treponema. This genus is in the family Spirochaetaceae as in Bergey's manual of systematic bacteriology. Other generic members of the family include Spirochaeta, Cristispira and Borrelia. This conventional classification is in accord with phylogenetic analysis of the spirochetes based on 16S rRNA cataloguing. The oral spirochetes fall naturally within the grouping of Treponema. Only four species of Treponema have been cultivated and maintained reliably: Treponema denticola, Treponema pectinovorum, Treponema socranskii and Treponema vincentii. These species have valid names according to the rules of nomenclature except for Treponema vincentii, which only has had effective publication. The virulence factors of the oral spirochetes updated in this mini-review have been discussed within the following broad confines: adherence, cytotoxic effects, iron sequestration and locomotion. T. denticola has been shown to attach to human gingival fibroblasts, basement membrane proteins, as well as other substrates by specific attachment mechanisms. The binding of the spirochete to human gingival fibroblasts resulted in cytotoxicity and cell death due to enzymes and other proteins. Binding of the spirochete to erythrocytes was accompanied by agglutination and lysis. Hemolysis releases hemin, which is sequestered by an outer membrane sheath receptor protein of the spirochete. The ability to locomote through viscous environments enables spirochetes to migrate within gingival crevicular fluid and to penetrate sulcular epithelial linings and gingival connective tissue. The virulence factors of the oral spirochetes proven in vitro underscore the important role they play in the periodontal disease process. This role has been evaluated in vivo by use of a murine model.

Adherence to and penetration through endothelial cells by oral treponemes

Oral spirochetes were co-incubated with monolayers of endothelial cells seeded into multiwell plates or onto filters mounted in plastic chambers. Attachment was assessed using an enzyme-linked immunosorbent assay and scanning electron microscopy. Invasiveness was determined by monitoring media beneath filters within chambers for spirochetes using darkfield microscopy. Transmission electron microscopy was used to estimate intercellular and intracellular passage of spirochetes through monolayers. All tested treponemes attached to monolayers in a dose- and time-dependent manner, except Treponema phagedenis. A few treponemes were observed within host cell cytoplasm. Unidentified spirochetes obtained from dental plaque were also invasive. Results indicate that oral spirochetes possess virulence-associated characteristics shared with pathogenic spirochetes. Further studies should examine the possibility that invasive spirochetes could disseminate from within affected gingiva.

Antibodies to Treponema pallidum in serum from subjects with periodontitis: relationship to pathogen-related oral spirochetes

Pathogen-related oral spirochetes were identified in dental plaque using monoclonal antibodies to putative Treponema pallidum-specific proteins, and serum from subjects with necrotizing ulcerative gingivitis contained immunoglobulin G to molecules thought to be restricted to T. pallidum. The purpose of this study was to determine whether subjects with periodontitis were more likely to have serum antibodies to T. pallidum if pathogen-related oral spirochetes were present. Pathogen-related oral spirochetes were detected in subgingival plaque from 27 of 40 subjects, and 33 subjects had serum antibodies that bound T. pallidum proteins in immunoblots. Subjects with pathogen-related oral spirochetes were no more likely to have IgA, IgG or IgM to 15-, 37- or 47-kDa proteins than were subjects without pathogen-related oral spirochetes. In contrast to subjects with necrotizing ulcerative gingivitis, subjects with periodontitis had no detectable antibodies to 37- or 12-kDa proteins. Further research is needed to identify the stimulus for antibodies that cross-react with T. pallidum proteins.

Lack of humoral immune protection against Treponema denticola virulence in a murine model

This study investigated the characteristics of humoral immune responses to Treponema denticola following primary infection, reinfection, and active immunization, as well as immune protection in mice. Primary infection with T. denticola induced a significant (400-fold) serum immunoglobulin G (IgG) response compared to that in control uninfected mice. The IgG response to reinfection was 20, 000-fold higher than that for control mice and 10-fold higher than that for primary infection. Mice actively immunized with formalin-killed treponemes developed serum antibody levels seven- to eightfold greater than those in animals after primary infection. Nevertheless, mice with this acquired antibody following primary infection or active immunization demonstrated no significant alterations of lesion induction or decreased size of the abscesses following a challenge infection. Mice with primary infection developed increased levels of IgG3, IgG2b, and IgG2a antibodies, with IgG1 being lower than the other subclasses. Reinfected mice developed enhanced IgG2b, IgG2a, and IgG3 and less IgG1. In contrast, immunized mice developed higher IgG1 and lower IgG3 antibody responses to infection. These IgG subclass distributions indicate a stimulation of both Th1 and Th2 activities in development of the humoral immune response to infection and immunization. Our findings also demonstrated a broad antigen reactivity of the serum antibody, which was significantly increased with reinfection and active immunization. Furthermore, serum antibody was effective in vitro in immobilizing and clumping the bacteria but did not inhibit growth or passively prevent the treponemal infection. These observations suggest that humoral immune responses, as manifested by antibody levels, isotype, and antigenic specificity, were not capable of resolving a T. denticola infection.

Hemoxidation and binding of the 46-kDa cystalysin of Treponema denticola leads to a cysteine-dependent hemolysis of human erythrocytes

Cystalysin, a 46-kDa protein isolated from the cytosol of Treponema denticola, was capable of both cysteine dependent hemoxidation and hemolysis of human and sheep red blood cells. The activities were characteristic of a cysteine desulfhydrase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western immunoblotting analysis of the interaction of cystalysin with the red blood cells revealed an interaction of the protein with the red blood cell membrane. Substrates for the enzyme (including L-cysteine and beta-chloroalanine) enhanced the interaction, which occurred with both whole red blood cells as well as with isolated and purified red blood cell ghosts. SDS-PAGE and western immunoblotting employing anti-hemoglobin serum revealed that, during the hemoxidative events, the hemoglobin molecule associated with the red blood cell membrane, forming putative Heinz bodies. Spectrophotometric analysis of the hemoxidative events (cystalysin + cysteine + red blood cells) revealed a chemical modification of the native hemoglobin to sulfhemoglobin and methemoglobin. Hemoxidation also resulted in the degradation of both the red blood cell alpha- and beta-spectrin. The results presented suggest that the interaction of cystalysin with the red blood cell membrane results in the chemical oxidation of the hemoglobin molecule as well as an alteration in the red blood cell membrane itself.

Multiple forms of the major phenylalanine specific protease in Treponema denticola

The 160, 190 and 270 kDa outer sheath proteases of Treponema denticola ATCC 35404 were found to be multiple forms of the major 91 kDa phenylalanine protease (PAP) by immunoblotting using anti-91 kDa specific antibodies. Multiple forms of the phenylalanine protease were also found in 2 other T. denticola strains studied, ATCC 33520 and the clinical isolate GM-1. Protein, proteolytic and Western blot analyses using antibodies against the PAP and the major outer sheath protein (MSP) indicated that the 190 and 270 kDa proteases were protein complexes formed by the MSP and the PAP. These complexes dissociated by storage in 0.3% or higher SDS concentrations. The purified PAP was found to completely degrade keratin, but was unable to degrade native actin either in its monomeric or polymerized form. The association of the MSP adhesin with a protease capable of degrading host native proteins may benefit the obtention of protein-based nutrients necessary to support the growth of these treponemes. These complexes may also play a role in the structural organization of T. denticola outer sheath.

Sulfhemoglobin formation in human erythrocytes by cystalysin, an L-cysteine desulfhydrase from Treponema denticola

Cystalysin, isolated from the oral pathogen Treponema denticola, is an L-cysteine desulfhydrase (producing pyruvate, ammonia and hydrogen sulfide from cysteine) that can modify hemoglobin and has hemolytic activity. Here, we show that enzymatic activity of recombinant cystalysin depends upon stochiometric pyridoxal phosphate. The enzyme was not functional as an L-alanine transaminase, and had a strong preference for L-cysteine over D-cysteine. Cystalysin preferred small alpha-L-amino acids as substrates or inhibitors and was far more active towards L-cysteine than towards the other standard amino acids that undergo pyridoxal phosphate-dependent beta-elimination reactions (serine, threonine, tryptophan and tyrosine). Cystalysin tolerated small modifications to the carboxylate of L-cysteine (i.e., the methyl and ethyl esters of L-cysteine were good substrates), but the smallest possible peptide with an N-terminal cysteine, L-cysteinylglycine, was a very poor substrate. These results, combined with the implicit requirement for a free amine for pyridoxal phosphate-dependent reactions, imply that cystalysin cannot catabolize cysteine residues located within peptides. Cystalysin has Michaelis-Menten kinetics towards L-cysteine, and there was little or no inhibition by ammonia, H2S, pyruvate and acetate. Human erythrocytes incubated with H2S or with cystalysin and cysteine primarily accumulated sulfhemoglobin and methemoglobin, along with minor amounts of choleglobin and protein aggregates. Erythrocytes retained the ability to reduce methemoglobin in the presence of H2S. Cystalysin could not modify hemoglobin when beta-chloroalanine was the substrate, indicating an absolute requirement for H2S production. Cystalysin appears to be an unregulated L-cysteine catabolizing enzyme, with the resulting H2S production being essential to the atypical hemolytic activity.

Periodontal disease in dogs. Etiopathogenesis, prevalence, and significance

Periodontal disease is very common and often very severe in dogs. It is caused by accumulation of bacterial plaque, particularly Gram-negative anaerobic rods. Tissue destruction results from autodegradation induced by the continuing inflammatory response. Small dogs are particularly at risk. Prevention by retarding accumulation of plaque is the key concept.

Molecular epidemiology of oral treponemes associated with periodontal disease

Periodontitis, a disease responsible for tooth loss worldwide, is characterized by chronic inflammation of the periodontium, eventually leading to destruction of periodontal ligaments and supporting alveolar bone. Spirochetes, identified by dark-field microscopy as being the most predominant bacteria in advanced lesions, are thought to play a causative role. Various spirochetal morphotypes were observed, but most of these morphotypes are as yet uncultivable. To assess the role of these organisms we designed oligonucleotide probes for the identification of both cultivable and so far uncultivable spirochetes in periodontitis patients. Subgingival plaque specimens taken from diseased sites (n = 200) and healthy control sites (n = 44) from 53 patients with rapidly progressive periodontitis (RPP) were submitted to direct in situ hybridization or dot blot hybridization after prior amplification with eubacterial primers. Spirochetes were found in all patients, but their distributions varied considerably. Parallel use of oligonucleotide probes specific for cultivable or so far uncultivable treponemes suggested the presence of novel yet unknown organisms at a high frequency. These uncultivable treponemes were visualized by fluorescence in situ hybridization, and their morphologies, sizes, and numbers could be estimated. All RPP patients included in this study harbored oral treponemes that represent either novel species, e.g., Treponema maltophilum, or uncultivable phylotypes. Therefore, it is necessary to include these organisms in etiologic considerations and to strengthen efforts to cultivate these as yet uncultivable treponemes.

Virulence characteristics of oral treponemes in a murine model

This study was designed to investigate the virulence characteristics of Treponema denticola, T. socranskii, T. pectinovorum, and T. vincentii following challenge infection of mice. These microorganisms induced well-demarcated, dose-dependent, raised subcutaneous (s.c.) abscesses which were similar in time of onset, lesion progression, and duration of healing. Only viable cells were capable of inducing these characteristic s.c. abscesses. Histological examination of the skin lesion 3 and 5 days postinfection revealed abscess formation in the s.c. tissues, and abundant spiral organisms were demonstrated to be present in the abscess. Host resistance modulation by dexamethasone (neutrophil alteration) and cyclophosphamide (neutrophil depletion) pretreatment had a minimal effect on the virulence expression by any of these treponemes. The T. denticola isolates demonstrated significant trypsin-like protease (TLPase) activity, while both T. socranskii and T. vincentii were devoid of this activity. Interestingly, T. pectinovorum strains were heterogeneous with respect to TLPase as high producers, low producers, and nonproducers. However, no differences in lesion formation were noted regardless of whether the species expressed this proteolytic activity or whether treatment with N alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) and dithiothreitol was performed. These results showed that (i) a murine model may be used to evaluate virulence expression by oral treponemes; (ii) while TLPase activity varies among the oral treponemes, this protease does not appear to participate in abscess induction in the mouse model; and (iii) T. pectinovorum strains show variation in TLPase activity.

Cystalysin, a 46-kilodalton cysteine desulfhydrase from Treponema denticola, with hemolytic and hemoxidative activities

A 46-kDa hemolytic protein, referred to as cystalysin, from Treponema denticola ATCC 35404 was overexpressed in Escherichia coli LC-67. Both the native and recombinant 46-kDa proteins were purified to homogeneity. Both proteins expressed identical biological and functional characteristics. In addition to its biological function of lysing erythrocytes and hemoxidizing the hemoglobin to methemoglobin, cystalysin was also capable of removing the sulfhydryl and amino groups from selected S-containing compounds (e.g., cysteine) producing H2S, NH3, and pyruvate. This cysteine desulfhydrase resulted in the following Michaelis-Menten kinetics: Km = 3.6 mM and k(cat) = 12 s(-1). Cystathionine and S-aminoethyl-L-cysteine were also substrates for the protein. Gas chromatography-mass spectrometry and high-performance liquid chromatography analysis of the end products revealed NH3, pyruvate, homocysteine (from cystathionine), and cysteamine (from S-aminoethyl-L-cysteine). The enzyme was active over a broad pH range, with highest activity at pH 7.8 to 8.0. The enzymatic activity was increased by beta-mercaptoethanol. It was not inhibited by the proteinase inhibitor TLCK (N alpha-p-tosyl-L-lysine chloromethyl ketone), pronase, or proteinase K, suggesting that the functional site was physically protected or located in a small fragment of the polypeptide. We hypothesize that cystalysin is a pyridoxal-5-phosphate-containing enzyme, with activity of an alphaC-N and betaC-S lyase (cystathionase) type. Since large amounts of H2S have been reported in deep periodontal pockets, cystalysin may also function in vivo as an important virulence molecule.

Membrane components of Treponema denticola trigger proteinase release from human polymorphonuclear leukocytes

Tissue destruction during periodontitis is believed to be primarily brought about by leukocyte proteinases. We postulate that oral spirochetes cause discharge of polymorphonuclear leukocyte (PMN) lysosomal enzymes. Effects of Treponema denticola 53-kDa outer membrane protein, lipopolysaccharide (LPS), and peptidoglycan on degranulation of matrix metalloproteinases (MMP)-8 (collagenase) and -9 (gelatinase), cathepsin G, and elastase by human peripheral blood PMNs were studied by specific enzyme assays and Western blot analysis. T. denticola 53-kDa kDa outer membrane protein was found to be a particularly efficient inducer of MMP-8 release. The induction was comparable with that of phorbol myristate acetate, a known inducer of PMN specific granule discharge. All of the treponemal substances, most notably the 53-kDa protein and LPS, induced release of MMP-9, a component of C-type granules. Both collagenase and gelatinase released from PMNs were mostly in active forms. Release of cathepsin G and elastase was also observed with the 53-kDa protein treatment. The other T. denticola substances did not induce release of these serine proteinases. Lactate dehydrogenase was not released from PMNs by the treatments, indicating that the degranulation was specific and not caused by toxic effects of the substances. This was confirmed by transmission electron microscopy of PMNs treated with the 53-kDa protein that showed rapid vacuole formation and cell shape changes but no disintegration of the cells. Thus, T. denticola may participate in the PMN-dependent extracellular matrix degradation during the course of periodontal inflammation by triggering the secretion and activation of matrix metalloproteinases.

Phylogenetic analysis of pathogen-related oral spirochetes

Recently, Riviere et al. reported as yet uncultivable invasive oral spirochetes that cross-reacted with monoclonal antibodies (MAbs) specific for Treponema pallidum (G. R. Riviere, K. S. Elliot, D. F. Adams, L. G. Simonson, L. B. Forgas, A. M. Nilius, and S. A. Lukehart, J. Periodontol. 63:131-136, 1992; G. R. Riviere, M. A. Wagoner, S. A. Baker-Zander, K. S. Weisz, D. F. Adams, L. Simonson, and S. A. Lukehart, N. Engl. J. Med. 325:539-543, 1991; G. R. Riviere, K. S. Weisz, D. F. Adams, and D. D. Thomas, Infect. Immun. 59:3377-3380, 1991; G. R. Riviere, K. S. Weisz, L. G. Simonson, and S. A. Lukehart, Infect. Immun. 59:2653-2657, 1991). In an attempt to phylogenetically analyze these pathogen-related oral spirochetes, we used immunomagnetic separation, combined with comparative sequence analysis of 16S rRNA genes amplified in vitro by the PCR. The bacteria were immunomagnetically enriched from subgingival plaque samples of patients with rapidly progressive periodontitis by using MAb H9-2 specific for the 37-kDa endoflagellum sheath protein of T. pallidum. After PCR amplification with universal eubacterial primers 16S rRNA gene fragments were cloned into Escherichia coli. A total of 20 randomly selected recombinants were analyzed by sequencing about 200 to 300 bases of the 500-bp inserts. All the spirochetal 16S rRNA sequences clustered to previously described, as yet uncultivable cluster 7 treponemes of group I (B. K. Choi, B. J. Paster, F. E. Dewhirst, and U. B. Göbel, Infect. Immun. 62:1889-1895, 1994). With a sequence similarity of 96.4% the most closely related cultivable treponeme was Treponema vincentii, which also belongs to the group I treponemes. Subsequent immunological analysis of cultured treponemes with MAb H9-2 revealed that only T. vincentii strains showed specific immunofluorescence or a characteristic 37-kDa band in immunoblots. We therefore conclude that pathogen-related oral spirochetes constitute a heterogeneous population of treponemes comprising T. vincentii and T. vincentii-related organisms that have common epitopes cross-reacting with MAb H9-2.

Associations between Porphyromonas gingivalis and oral treponemes in subgingival plaque

Colonization and/or proliferation of Treponema denticola may depend on the presence of Porphyromonas gingivalis. The aims of this study were to confirm this synergistic relationship, to determine whether other oral bacteria were similarly associated with P. gingivalis and to relate coinfection to the periodontal status of plaque donors. Subgingival plaque was collected from every tooth except third molars in 106 subjects who were grouped by their worst periodontal condition. In addition to P. gingivalis, monoclonal antibodies were used to identify Campylobacter rectus, Eikenella corrodens, T. denticola, Treponema socranskii and pathogen-related oral spirochetes. Associations of these bacteria with coinfection by P. gingivalis were assessed by estimated odds ratios. The results indicate that coinfection with P. gingivalis is linked to all tested bacteria, but each pair was associated with distinct periodontal conditions. The distribution of coinfected sites suggests biased colonization of facial surfaces over lingual surfaces.

Periodontal status and detection frequency of bacteria at sites of periodontal health and gingivitis

It is generally recognized that bacteria in dental plaque at sites of periodontal diseases are not commonly found at sites of periodontal health. One hypothesis to explain the etiology of periodontitis is that pathogenic bacteria from diseased sites infect healthy sites. It has been suggested that gingival inflammation may predispose sites to colonization by bacteria associated with periodontal diseases. The purpose of this cross-sectional study was to determine whether the detection frequency of selected bacteria at sites of periodontal health or gingivitis differed between subjects who were in good periodontal health, subjects who had gingivitis, or subjects with periodontitis. The clinical status of every tooth (except third molars) from 106 subjects was characterized by means of clinical attachment level, probing depth and by signs of inflammation. Subgingival plaque was collected from mesio-facial and disto-lingual surfaces. Specific monoclonal antibodies were used in an immunocytochemical assay to identify Campylobacter rectus, Eikenella corrodens, Porphyromonas gingivalis, pathogen-related oral spirochetes (PROS, using Treponema pallidum subspecies pallidum monoclonal antibodies), T. denticola (serotypes A-D), T. socranskii subspecies buccale and T. socranskii subspecies socranskii. Differences in detection of bacteria between groups of subjects were measured using odds ratios (OR). Results of this study indicate that PROS was the only identified bacterium at sites of both health and gingivitis that demonstrated a significant positive relationship with the presence of periodontitis. These findings do not prove that bacteria spread from periodontitis sites, nor do they imply that disease necessarily results from infection. However, these data do suggest that some bacteria associated with periodontitis are more likely than others to tolerate conditions at healthy sites and that the presence of periodontitis increases risk of infection at healthy sites.

Aspects of adherence of oral spirochetes

Oral spirochetes are present in the oral cavity in various numbers and forms and have been strongly implicated as playing a role in the etiology of periodontal disease. Because adherence to host tissues is a critical first step in establishing a bacterial infection, reports on the attachment of oral spirochetes to host tissues and matrix components were reviewed. The great bulk of the literature concerns Treponema denticola; however, where there is information regarding other oral spirochete species, it will be noted.

Cytopathic effects of Treponema denticola chymotrypsin-like proteinase on migrating and stratified epithelial cells

The effects of Treponema denticola and its outer membrane-bound chymotrypsin-like proteinase on periodontal ligament epithelial cell cultures at different stages of maturity were studied. In sparse cultures with migrating epithelial cells, large intracellular vacuoles were formed rapidly following exposure to live T. denticola. Treponemes showing structural damage were seen occasionally inside membrane-bound vesicles. Intensive membrane blebbing occurred in infected cells and continued for up to 48 h before the cell died. Blebbing could also be induced by a purified chymotrypsin-like proteinase of T. denticola. Cortical actin and alpha-actinin of the bacterium-treated cells showed disorganization, and pericellular fibronectin was degraded by both whole T. denticola and the isolated proteinase. Epithelial cells with well-formed lateral cell contacts appeared to be more resistant to the effects of T. denticola than migrating isolated cells. In multilayer epithelial cultures, adhesion of T. denticola and membrane blebbing were observed infrequently. There was no evidence of invasion of T. denticola into epithelial multilayers. However, immunogold electron microscopy showed rapid transport of T. denticola chymotrypsin-like proteinase into newly formed large intracellular vacuoles within the epithelial layers. These vacuoles were lined by membranes studded with ribosomes. T. denticola-treated epithelial multilayers had loose cell contacts, collapsed intercellular spaces, and increased permeability. Through its capacity to cause these unique cytopathic effects, the chymotrypsin-like proteinase of T. denticola has the potential to contribute to the initiation of periodontal disease.

Comparison of molecular and microscopic techniques for detection of Treponema pallidum in genital ulcers

We compared the ability of direct immunofluorescent staining (DFA) and the PCR to detect Treponema pallidum in specimens from patients with genital ulcer disease. Touch preparations from 156 patients with genital lesions were fixed in acetone and stained with a fluorescein-labeled monoclonal antibody specific for the 37-kDa antigen of T. pallidum. After microscopic examination, the smear was removed from the slide with a swab. DNA was extracted with phenol-chloroform and precipitated with isopropanol. Ten microliters of the extracted DNA was amplified by PCR using primers for the gene encoding the 47-kDa protein of T. pallidum and hybridized to an internal probe. Twenty-two of 156 specimens were positive for T. pallidum by DFA and PCR, while 127 were negative by both methods, yielding a concordance of 95.5% (kappa = 0.84). Four specimens were positive by PCR and negative by DFA, while three specimens were negative by PCR and positive by DFA. The DFA-negative, PCR-positive specimens may have resulted from the presence of large numbers of leukocytes on the slides, obscuring visualization of treponemes. The DFA-positive, PCR-negative results were not due to inhibition of the PCR since purified T. pallidum DNA was amplified when added to aliquots of these specimens. Negative results in these specimens were most likely due to inefficient recovery of their DNA. These data suggest that DFA and PCR are equivalent methods for detection of T. pallidum on touch preparations of genital lesions. Further refinements of the PCR assay are necessary for it to significantly improve the detection of T. pallidum in genital lesions.

Degradation of endogenous plasma membrane fibronectin concomitant with Treponema denticola 35405 adhesion to gingival fibroblasts

Treponema denticola adhesion and degradation of fibronectin (Fn) on human gingival fibroblasts (HGF) were studied by immunofluorescence and enzyme-linked immunosorbent assays. The number of adherent bacteria increased and the amount of immunoreactive Fn decreased as a function of increasing T. denticola concentration. The distribution of cell-bound Fn was punctate in micrographs. Anti-human Fn impaired bacterial adhesion to HGF. Phenylmethylsulfonyl fluoride inhibited Fn degradation but not adhesion. Sonicated extracts and diluted spent growth medium degraded HGF Fn but, unlike intact T. denticola cells, they hardly stimulated F-actin rearrangements.

Diversity of cultivable and uncultivable oral spirochetes from a patient with severe destructive periodontitis

To determine the genetic diversity of cultivable and uncultivable spirochetes in the gingival crevice of a patient with severe periodontitis, partial 16S rRNA genes were cloned from PCR-amplified products of DNA and RNA extracted from a subgingival plaque sample. Approximately 500 bp were amplified in PCRs by using universally conserved primers with polylinker tails. Purified PCR products were cloned into Escherichia coli by using the plasmid vector pUC19. The resultant clone library was screened by colony hybridization with a radiolabeled, treponeme-specific oligonucleotide probe. The 16S rRNA inserts of 81 spirochetal clones were then sequenced by standard procedures. Sequences were compared with 16S rRNA sequences of 35 spirochetes, including the four known cultivable oral treponeme species. The analysis revealed an unexpected diversity of oral treponemes from a single patient. When 98% or greater sequence similarity was used as the definition of a species-level cluster, the clone sequences were found to represent 23 species. When 92% similarity was used as the definition, the clones fell into eight major groups, only two of which contained named species, Treponema vincentii and Treponema denticola, while Treponema pectinovorum and Treponema socranskii were not represented in any cluster. Seven of the 81 spirochetal clones were found to contain chimeric 16S rRNA sequences. In situ fluorescence hybridization with a fluorescein isothiocyanate-labeled oligonucleotide probe specific for one of the new species representing cluster 19 was used to identify cells of the target species directly in clinical samples.

Characterization of antisera raised against Treponema denticola (ATCC 33521) whole cell, outer sheath, protoplasmic cylinder, and axial flagella

In this study we produced polyclonal antisera directed to whole cell, outer sheath, protoplasmic cylinder and axial flagella sonicates of Treponema denticola (ATCC 33521) reference strain. Furthermore, the reactivity of the antisera was determined, using the enzyme-linked immunosorbent assay and immunoblotting techniques. As control antigen, other gram-negative bacteria (Salmonella minnesota, Escherichia coli) and related pathogenic spirochetes (Borrelia burgdorferi and Treponema pallidum) were used. It could be shown that the purified antibodies were specific for Treponema denticola and did not cross-react with the control antigens tested. Interestingly, with one exception, the anti-axial flagella antibody reacted with the flagellin of Treponema pallidum but not with Borrelia burgdorferi flagella. It is intended to use these antisera for the characterization of patient isolates in further studies.

Involvement of treponemal surface-located protein and carbohydrate moieties in the attachment of Treponema denticola ATCC 33520 to cultured rat palatal epithelial cells

We studied the nature of attachment of Treponema denticola ATCC 33520 to a microscopically distinct population of rounded rat palatal epithelial cells. The motility of the freshly harvested spirochetes appeared not be a prerequisite for attachment. Treatment of T. denticola ATCC 3350 with proteinase-K, heat, glutaraldehyde, formaldehyde and periodate oxidation decreased the attachment to the rounded rat palatal epithelial cells, indicating the involvement of protein and carbohydrate moieties. Trypsin treatment had no effect on the attachment. The attachment of T. denticola ATCC 33520 was decreased after treatment with native non-immune rabbit serum, native polyclonal rabbit serum, D-mannose, N-acetyl-D-galactosamine and sialic acid. The results indicate that the attachment of T. denticola ATCC 33520 to rounded rat palatal epithelial cells is mediated by trypsin-resistant adhesin(s) of protein and carbohydrate nature, with affinity for D-mannose, N-acetyl-D-galactosamine and sialic acid.

HIV-associated periodontal disease: new oral spirochete found

This study examines plaque for the presence of a recently described oral spirochete, tentatively called pathogen-related oral spirochete. This investigation found PROS in plaque of patients with HIV-associated periodontal disease.

Spirochaetes in oral infections

Oral spirochaetes, which are small-, medium- or large-sized, include species of the genus Treponema, many of which have not yet been cultured. They are found in root canal infections, pericoronitis, gingivitis and periodontitis, constituting up to 10% of the flora in endodontic abscesses, 30% in acute necrotizing ulcerative gingivitis, and 56% in advanced marginal periodontitis. The strong proteolytic activity of these organisms probably make them causes of infection rather than consequences. Being able to penetrate tissue, they bring their enzymes, metabolic products, and endotoxins, in direct contact with target cells. This may perturb essential functions of host cells and immunoglobulins. Enzyme activities may also help fulfil the complex growth requirements of spirochaetes in vivo. Reaction between infected periodontal tissue and monoclonal antibodies to Treponema pallidum has suggested that uncharacterized pathogen-related oral spirochaetes have surface structures and functions analogue to this well recognized pathogen. This warrants a more intensified search for the role of spirochaetes in oral infections.