The microflora of periodontal sites showing active destructive progression

Pre- and post-implantation microbiota of the tongue, teeth, and newly placed implants

OBJECTIVES

This investigation sought intra-oral sources of species colonizing dental implants.

MATERIALS AND METHODS

Plaque samples were taken pre- and post-successful osseointegration from implants, teeth, and from tongues of 10 edentulous and 11 partially dentate subjects. Samples were assayed using whole genomic DNA probes in a checkerboard assay to 42 subgingival species.

RESULTS

Similar prevalences and mean levels (10(3) to 10(4)) of microorganisms colonized implants and teeth. Species levels from tongue samples were higher than those of teeth and implants, although species prevalence was similar, suggesting that larger samples were obtained from the tongue. No significant differences were observed between the microbiota from the tongue of edentulous and partially dentate subjects. Most implant species were detected on tongue pre-implantation. In individual edentulous subjects, there were positive associations between Capnocytophaga ochracea and Campylobacter rectus from tongue and implant samples. In individual partially dentate subjects, there were positive associations between Fusobacterium nucleatum subsp. vincentii from tongue and implant samples, and Treponema denticola from implant and tooth samples taken at the same visit.

CONCLUSION

This study indicated that the tongue, in addition to teeth, can be a source for species colonizing new implants.

Oral flora and pathogenic organisms

Oral microbial flora consist of numerous bacterial taxa, ranging from aerobes through fastidious anaerobes, and fungi, viruses, and protozoa. Many of these bacteria are unique to the oral cavity. The organisms exist in a complex interrelationship that is regulated and maintained by physical and metabolic microbial interactions, and by environmental factors, such as saliva and diet. Many of these organisms are relatively harmless, although others are significant pathogens, producing local and systemic diseases in healthy and compromised individuals.

Isolation and chemical analysis of a lipopolysaccharide from the outer membrane of the oral anaerobic spirochete Treponema pectinovorum

Isolation of a putative lipopolysaccharide from the surface of the oral treponeme, Treponema pectinovorum, revealed it to contain larger amounts of 3-deoxy-D-manno-octulosonic acid compared with other oral Treponema species. This molecule was isolated from the outer membrane of T. pectinovorum and had chemical characteristics of a putative lipopolysaccharide. The yield of lipopolysaccharide was between 0.6% and to 1.1% of the bacterial dry weight. The purified molecule was resistant to the action of proteinases and consisted of both sugars and lipids. 3-Deoxy-D-manno-octulosonic acid and hexoses accounted for 6.1-8.7% and 17.6-20.2%, respectively of the dry weight. Carbohydrate compositional analysis revealed the presence of glucose, galactose, 2-acetamido-2-deoxy-glucose, rhamnose and 6-deoxy-talose in the molar ratio of 1.00:0.96:0.19:0.88:0.98, respectively. No heptose was detected. The fatty acid analysis determined the presence of straight chain, C13:00, C14:00, C15:00 and C17:00 acids, as well as branched chain, C13:00, C14:00 and two species of C15:00, acids. Electrophoretic analysis indicated that the lipopolysaccharide was present as two major species.

Enhanced interleukin-8 production in THP-1 human monocytic cells by lipopolysaccharide from oral microorganisms and granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been used to assist in bone marrow recovery during cancer chemotherapy. Interleukin-8 (IL-8) plays an important role in macrophage mediated inflammatory processes including exacerbation of periodontal diseases, one of the most common complications in GM-CSF receiving cancer patients. The effect of GM-CSF supplementation on IL-8 production was investigated in a human monocyte cell line THP-1, stimulated with lipopolysaccharide extracted from two oral microorganisms, Porphyromonas gingivalis and Fusobacterium nucleatum. Resting THP-1 cells were treated with lipopolysaccharide (1 microgram/ml) of P. gingivalis or F. nucleatum and/or GM-CSF (50 IU/ml) for varying time periods. The production of IL-8 in THP-1 cells was measured by a solid-phase enzyme-linked immunosorbent assay (ELISA). A very low level of the cytokine IL-8 was produced constitutive in THP-1 cells. Starting from 8 h of treatment and afterwards GM-CSF alone significantly increased IL-8 production in THP-1 cells. Lipopolysaccharide (1 microgram/ml) extracts from either F. nucleatum or P. gingivalis amplified IL-8 production 500-800 times in comparison to resting THP-1 cells. When lipopolysaccharide of F. nucleatum or P. gingivalis was supplemented with 50 IU/ml of GM-CSF, there was a statistically significant enhanced production of IL-8 by THP-1 cells after 1 day to 7 days of treatment as compared with lipopolysaccharide treatment alone. GM-CSF (50 IU/ml) also significantly increased IL-8 production from 2-7 days of treatment of THP-1 cells when supplemented with a positive control, phorbol-12-myristate-13 acetate (PMA), as compared to PMA treatment alone. These investigations using the in vitro THP-1 human monocyte cell model indicate that there may be an increase in the response on a cellular level to oral endotoxin following GM-CSF therapy as evidenced by enhanced production of the tissue-reactive inflammatory cytokine, IL-8.

Rapid and efficient inactivation of IL-6 gingipains, lysine- and arginine-specific proteinases from Porphyromonas gingivalis

Deregulation of the cytokine network is an important adaptation of pathogenic bacteria to modulate and evade a host immune response. Here we describe that IL-6 is rapidly and efficiently cleaved and inactivated by the arginine- and lysine-specific proteinases from Porphyromonas gingivalis, referred to as RGP-A, RGP-B, and KGP. One of the primary cleavage sites for RGPs has been mapped between R18 and Q19 within the N-terminal region of the IL-6 polypeptide chain; however, both KGP and RGPs cleave IL-6 within the C-terminal region of the polypeptide chain. After these initial proteolytic cleavages, IL-6 is further degraded by each of the enzymes tested. Although KGP is the most potent IL-6-degrading proteinase, the initial C-terminal cleavage of IL-6 mediated by all gingipains is already sufficient to inactivate this cytokine. Our data are consistent with the observation that in periodontitis the IL-6 concentration is lowest in the gingival tissue adjacent to bacterial plaque, whereas significantly elevated concentrations of this cytokine are detected around the infected area. Degradation of IL-6 by gingipains may, therefore, represent an additional mechanism which influences the balance between pro- and anti-inflammatory reactions at distal versus proximal sites from the periodontal plaque.

The effects of HIV viral load on the phagocytic activity of monocytes activated with lipopolysaccharide from oral microorganisms

A study was undertaken to determine whether viral load status in HIV+ patients has any potential effect on monocyte phagocytic function both before and after challenge of the monocytes with lipopolysaccharide (LPS) isolated from oral microorganisms. LPS of two putative periodontal pathogens Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum) was prepared. Whole blood samples in EDTA were collected from 30 HIV+ patients presenting for dental care at the University of Maryland. Control samples were prepared from appropriate uninfected individuals. Viral load was determined using quantitative RT-PCR (Amplicor, Roche Diagnostics). Phagocytic function was determined using FITC labeled Saccharomyces species in resting isolated monocytes and in cells after 24 h stimulation with 1 microgram/ml of LPS of P. gingivalis or F. nucleatum. Immunohistochemical staining was performed for complement receptor CR-1 (CD-35) on phagocyte cells. In HIV+ patients with high viral load (> 10,000 copies/ml), 13.5% of isolated resting monocytes demonstrated phagocytic activity, while 23% of the resting control monocytes from non-infected individuals showed phagocytic function. When the monocytes were stimulated with 1 microgram/ml of LPS of F. nucleatum, phagocytic activity was observed in 18.5% of monocytes in patients with high viral load, 33.5% with moderate viral load (400-10,00 copies/ml) and 51% with low viral load (<400 copies/ml), while 62% of the control monocytes demonstrated phagocytic activity. Stimulation of monocytes with LPS of P. gingivalis showed similar results. Complement receptor CD-35 showed a 50% decrease in expression in HIV+ patients with high viral load. A progressive decrease in monocyte/macrophage phagocytic function and CD-35 expression with and without oral LPS activation occurs after HIV infection and this trend appears to be accentuated in patients with high viral load. This relationship may contribute to increased susceptibility to oral opportunistic infections in advanced HIV+ patients.

Inhibition of osteoblastic cell differentiation by lipopolysaccharide extract from Porphyromonas gingivalis

Lipopolysaccharide from Porphyromonas gingivalis (P-LPS), an important pathogenic bacterium, is closely associated with inflammatory destruction of periodontal tissues. P-LPS induces the release of cytokines and local factors from inflammatory cells, stimulates osteoclastic-cell differentiation, and causes alveolar bone resorption. However, the effect of P-LPS on osteoblastic-cell differentiation remains unclear. In this study, we investigated the effect of P-LPS extract prepared by the hot-phenol-water method, on the differentiation of primary fetal rat calvaria (RC) cells, which contain a subpopulation of osteoprogenitor cells, into osteoblastic cells. P-LPS extract significantly inhibited bone nodule (BN) formation and the activity of alkaline phosphatase (ALPase), an osteoblastic marker, in a dose-dependent manner (0 to 100 ng of P-LPS extract per ml). P-LPS extract (100 ng/ml) significantly decreased BN formation to 27% of the control value and inhibited ALPase activity to approximately 60% of the control level on days 10 to 21 but did not affect RC cell proliferation and viability. P-LPS extract time-dependently suppressed the expression of ALPase mRNA, with an inhibitory pattern similar to that of enzyme activity. The expression of mRNAs for osteocalcin and osteopontin, matrix proteins related to bone metabolism, was markedly suppressed by P-LPS extract. Furthermore, P-LPS extract increased the expression of mRNAs for CD14, LPS receptor, and interleukin-1beta in RC cells. These results indicate that P-LPS inhibits osteoblastic-cell differentiation and suggest that LPS-induced bone resorption in periodontal disease may be mediated by effects on osteoblastic as well as osteoclastic cells.

Studies on the binding of Treponema pectinovorum to HEp-2 epithelial cells

We developed a radioassay to assess the adherence of the oral treponemes Treponema denticola and Treponema pectinovorum to live HEp-2 epithelial cells. T. pectinovorum bound firmly to the epithelial cell monolayer in a concentration-dependent manner. The results indicated that a subpopulation of T. pectinovorum appeared to bind and that the binding could be influenced by environmental factors. Increasing concentrations of fetal bovine serum inhibited binding, whereas T. pectinovorum membrane vesicles and co-incubation with T. denticola ATCC 35404 increased the number of cells bound to the monolayer. Treatment of T. pectinovorum with periodic acid, but not trypsin or proteinase K, decreased the binding suggesting that a cell surface carbohydrate, such as the O-antigenic component of the lipopolysaccharide, mediates attachment of the bacteria to the epithelial cells. Co-infection of the HEp-2 cells with both T. denticola and T. pectinovorum did not interfere with each other in attachment to the epithelial cell suggesting that they do not compete for the same cellular receptor on the host cell surface. This study demonstrates that T. pectinovorum is capable, in vitro, of forming a tight association with host cells and that this binding could represent an initial step in the pathogenesis of T. pectinovorum.

Antigen activation of THP-1 human monocytic cells after stimulation with lipopolysaccharide from oral microorganisms and granulocyte-macrophage colony-stimulating factor

A human THP-1 monocyte cell line culture system has been utilized to evaluate the morphological changes in THP-1 cells and to measure expression of activation antigens (CD-11b, CD-11c, CD-14, CD-35, CD-68, CD-71 and HLA-DR) as evidence of maturation of THP-1 cells in response to stimulation by lipopolysaccharide (LPS) from the oral microorganisms, Fusobacterium nucleatum and Porphyromonas gingivalis, and granulocyte-macrophage colony-stimulating factor. THP-1 cells were stimulated with LPS (1 microgram/ml) of P. gingivalis or F. nucleatum for different time periods (1, 2, 4 and 7 d). Detection of different activation antigens on THP-1 cells was performed by indirect immunohistochemical staining followed by light microscopy. Confirmational studies were performed in parallel using indirect immunofluorescence and immunogold electron microscopy for detection of the corresponding activation antigens. Expression of different activation antigens by resting THP-1 cells revealed HLA-DR to be on 3% of the cells; CD-11b, 9%; CD-11c, 8%; CD-14, 22%; CD-35, 9% and CD-68, 7%. The CD-71 activation antigen was not expressed in untreated THP-1 cells. LPS stimulation increased expression of all activation antigens. A significant (p < 0.05) increase in expression of CD-11b, CD-11c, CD-14, CD-35, CD-68 and CD-71 was observed when GM-CSF (50 IU/ml) was supplemented during the treatment of THP-1 cells with LPS of F. nucleatum or P. gingivalis. Activation and differentiation of THP-1 cells by LPS from oral microorganisms in the presence of GM-CSF supports a role for human macrophages in acute and chronic periodontal diseases and may explain the clinically observable periodontal exacerbations in some patients after GM-CSF therapy.

Microbiological understandings and mysteries of noma (cancrum oris)

The microbiologic history of noma was reviewed. Studies have associated the disease process with large numbers of fusiform bacilli and spirochetal organisms. In order to study the microbiology of the staging and infection periods of noma 62 Nigerian children, aged 3-14 years, 22 children had acute necrotizing ulcerative gingivitis (ANUG) and were also malnourished, 20 exhibited no acute necrotizing ulcerative gingivitis but were malnourished and 20 were free of acute necrotizing ulcerative gingivitis and in good nutritional state) were evaluated for the presence of viruses and oral microorganisms. The ANUG cases in the malnourished children had a higher incidence of Herpesviridae, the main virus being detected was cytomegalovirus. There were more anaerobic microorganisms recovered, with Prevotella intermedia as the predominant isolate, in the malnourished children as compared to the healthy children. A study of the predominant microflora in active sites of noma lesions was carried out in eight noma patients, 3-15 years of age, in Sokoto State, northwestern Nigeria. Fusobacterium necrophorum was recovered from 87.5% of the noma lesions. Oral microorganisms isolated included Prevotella intermedia, alpha-hemolytic streptococci and Actinomyces spp. which were isolated from 75.0, 50.0 and 37.5% of the patients, respectively. Peptostreptococcus micros, Veillonella parvula, Staphylococcus aureus and Pseudomonas spp. were each recovered from one lesion. All strains were observed to be sensitive to all of the antibiotics tested with the exception of one strain of P. intermedia which showed resistance to penicillin. The pathogenic mechanisms of F. necrophorum as a trigger organism were discussed. The isolation from human noma lesions of F. necrophorum, a pathogen primarily associated with animal diseases, may have important etiologic and animal transmission implications.

Prevalence of Porphyromonas gingivalis and periodontal health status

Periodontitis is a common, progressive disease that eventually affects the majority of the population. The local destruction of periodontitis is believed to result from a bacterial infection of the gingival sulcus, and several clinical studies have provided evidence to implicate Porphyromonas gingivalis. If P. gingivalis is a periodontal pathogen, it would be expected to be present in most subjects with disease and rarely detected in subjects with good periodontal health. However, in most previous studies, P. gingivalis has not been detected in the majority of subjects with disease, and age-matched, periodontally healthy controls were not included for comparison. The purpose of the study reported here was to compare the prevalence of P. gingivalis in a group with periodontitis to that of a group that is periodontally healthy. A comprehensive sampling strategy and a sensitive PCR assay were used to maximize the likelihood of detection. The target sequence for P. gingivalis-specific amplification was the transcribed spacer region within the ribosomal operon. P. gingivalis was detected in only 25% (46 of 181) of the healthy subjects but was detected in 79% (103 of 130) of the periodontitis group (P < 0.0001). The odds ratio for being infected with P. gingivalis was 11.2 times greater in the periodontitis group than in the healthy group (95% confidence interval, 6.5 to 19.2). These data implicate P. gingivalis in the pathogenesis of periodontitis and suggest that P. gingivalis may not be a normal inhabitant of a periodontally healthy dentition.

Functional changes in THP-1 human monocytic cells after stimulation with lipopolysaccharide of oral microorganisms and granulocyte macrophage colony stimulating factor

A human THP-1 monocyte cell line culture system has been utilized to observe the effect of granulocyte macrophage colony stimulating factor (GM-CSF) supplementation with lipopolysaccharide (LPS) of oral microorganisms to stimulate monocyte/macrophage functional activity. LPS of oral microorganisms, Fusobacterium nucleatum and Porphyromonas gingivalis was produced by phenol-water extraction and characterized. The phagocytosis assay was performed using F1TC labeled Saccharomyces yeast particles. Phagocytic functional activity was observed in 10-11% of resting THP-1 cells. Treatment of THP-1 cells with LPS of F. nucleatum or P. gingivalis increased the phagocytic activity of THP-1 cells 2-3 fold. GM-CSF significantly increased phagocytosis either alone or when supplemented with LPS of F. nucleatum or P. gingivalis. A chemotaxis assay was performed using a 48 well chemotaxis chamber. Chemotactic functional activity of THP-1 cells was increased 2-fold after 4 days of treatment with GM-CSF. Stimulation of THP-1 cells with LPS of F. nucleatum or P. gingivalis significantly reduced the chemotactic activity indicating the maturation towards a fixed macrophage. There were functional variations (chemotaxis and phagocytosis) in THP-1 cells in response to LPS of oral microorganisms following stimulation with GM-CSF.

Histatin 5 is a substrate and not an inhibitor of the Arg- and Lys-specific proteinases of Porphyromonas gingivalis

The salivary peptide histatin 5 has been reported to be an inhibitor of the Arg- and Lys-specific proteinases of Porphyromonas gingivalis, an oral pathogen associated with periodontitis. In this study a purified P. gingivalis proteinase preparation consisting of a complex of the Arg- and Lys-specific proteinases and adhesins was assayed using chromogenic substrates in the presence of histatin 5. Histatin 5 produced a concentration-dependent decrease in the initial rate of hydrolysis of the chromogenic substrates by both proteinases. However, pre-incubation of histatin 5 with the purified proteinase preparation or a P. gingivalis cell sonicate for 10 min prior to assay with the chromogenic substrates showed that under these conditions the salivary peptide did not decrease the initial rate of chromogen release. Mass spectrometric analysis revealed rapid degradation of histatin 5 at all four lysyl and all three arginyl residues by the P. gingivalis proteinases. This study demonstrates that histatin 5 is a substrate for the P. gingivalis extracellular Arg- and Lys-specific cysteine proteinases and not an inhibitor.

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.

Semi-automated measurement of motility of human subgingival microflora by image analysis

The purpose of this investigation was to quantitatively estimate bacterial motility by image analysis, and to apply this method for the measurement of motility of human subgingival microflora. We developed a semi-automated method for the quantification of bacterial motility using video microscopy, digitization and image processing. Moving images of both authentic bacterial samples and clinical samples were recorded using a phase contrast microscope with a high speed (1/100 s) shutter camera. The motility was evaluated by measuring the total number of pixels remaining after the subtraction of 2 serial video images. The total number of pixels was significantly correlated with both the sum of the velocity of each bacterial cell and the number of motile bacteria on the same original images. Motility of subgingival microflora from 140 clinical samples tested was measured at 0 pixels to 3600 pixels, whereas the effect of Brownian movement was less than 150 pixels. The motility of subgingival microflora estimated with this image analysis system did not differ much from objective judgments by the naked eyes of experts. These results suggest that a semi-automated image analysis system may be useful in the evaluation of the motility of human subgingival microflora.

An aminopeptidase nutritionally important to Fusobacterium nucleatum

The properties of an aminopeptidase (AP) from Fusobacterium nucleatum were studied in view of the fact that this organism, along with other Gram-negative anaerobes involved in periodontal diseases, survives in the subgingival environment by obtaining energy via the fermentation of a small number of peptide-derived amino acids. The AP was found to be cell-associated and was isolated from disrupted chemostat-grown cells. It was purified by (NH4)2SO4 fractionation, two column chromatographic steps and IEF. The enzyme was found to have a molecular mass of 54 kDa, a pI of 5.1, a pH optimum between 7.5 and 8.0 and, using Leu-Ala as substrate, it gave K(m) and Vmax values of 0.66 mM and 0.12 mumol min-1 mg-1, respectively. No complete homology was found between the N-terminal sequence of the first 20 amino acids (MDXKXYVDLKERFLRYVKFN...) and any other published sequence, but residues 8-20 gave a 62% match with residues 9-21 of an AP from Haemophilus influenzae. The enzyme was inactivated by chelating agents, bestatin, p-hydroxymercuribenzoate and some heavy metals. Cobalt ions restored EDTA-inactivated activity but did not reverse inhibition by 1,10-phenanthroline. In addition, bestatin and 1,10-phenanthroline had an inhibitory effect on the batch growth of F. nucleatum in a complex medium in which peptidase activities would be nutritionally essential. No such inhibition was observed in a chemically defined medium in which growth was not dependent upon peptidase activities. The peptidase described in this paper therefore appears to be a cobalt-activated metallo-AP which, together with other peptidases, is considered to be important in the survival of F. nucleatum in the subgingival environment of the mouth.

Interleukin-6 production by human monocytes treated with granulocyte-macrophage colony-stimulating factor in the presence of lipopolysaccharide of oral microorganisms

This study focused on the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) and lipopolysaccharide of the putative periodontal pathogens Porphyromonas gingivalis or Fusobacterium nucleatum on IL-6 production by THP-1 cells (a human monocytic cell line). Resting THP-1 cells were alternatively treated with GM-CSF (50 IU/ml) and lipopolysaccharide of P. gingivalis or F. nucleatum, in varying concentrations for varying time periods. IL-6 production in supernatant fluids of treated cells was evaluated by an enzyme-linked immunosorbent assay (ELISA) and a reverse transcription polymerase chain reaction (RT-PCR) was used to evaluate gene expression. Untreated THP-1 cells did not produce IL-6 as determined by ELISA. RT-PCR also failed to detect IL-6 mRNA in untreated THP-1 cells, indicating that IL-6 was not constitutively produced. After stimulation of THP-1 cells with lipopolysaccharide of F. nucleatum or P. gingivalis, IL-6 was produced, peaking at 4 h (200-300 pg/ml) and thereafter sharply declining by 8 h. When GM-CSF was added together with lipopolysaccharide of P. gingivalis or F. nucleatum, there was a synergistic quantitative increase in production of IL-6 as measured by ELISA as compared with lipopolysaccharide alone. IL-6 mRNA was detected by RT-PCR, 15 min after stimulation with lipopolysaccharide of either P. gingivalis or F. nucleatum. GM-CSF supplementation with lipopolysaccharide of P. gingivalis shortened the transcription of IL-6 mRNA to 5 min, a shift which was not observed with lipopolysaccharide of F. nucleatum, possibly indicating a different mechanism of initiation of transcription. Production of IL-6 by GM-CSF-treated THP-1 cells in the presence of lipopolysaccharide of oral microorganisms may provide a model for studying the role of macrophages in acute and chronic periodontal diseases, including the clinical periodontal exacerbation as observed in chemotherapy patients receiving GM-CSF for bone marrow recovery.

Subgingival microflora associated with nifedipine-induced gingival overgrowth

The purpose of this study was to examine the composition of subgingival plaque of 140 periodontal lesions in 35 patients with cardiovascular disorders who were administered nifedipine and manifested nifedipine-induced gingival overgrowth (GO). Age was inversely associated with the GO. Plaque index and bleeding index showed a significant association with GO, while nifedipine dosage and duration of nifedipine therapy were not found to be significant predictors of GO. The gingival inflammation as expressed in the logistic regression model by the interaction term color x tone was found to be significantly associated with the GO. Statistically significant differences between the groups of comparable probing depth and different degrees of GO were detected for Propionibacterium acnes, Capnocytophaga gingivalis, Capnocytophaga ochracea, Capnocytophaga sputigena, Bacteroides gracilis, Fusobacterium mortiferum, Fusobacterium nucleatum, Fusobacterium varium and Selenomonas sputigena in deep and enlarged lesions. Significantly more frequently isolated were the bacterial species Eubacterium alactolyticum, Campylobacter concisus, C. gingivalis, C. ochracea, C. sputigena, F. mortiferum, F. nucleatum, and F. varium from the more enlarged lesions (GO >3).

Granulocyte-macrophage colony-stimulating factor amplification of interleukin-1beta and tumor necrosis factor alpha production in THP-1 human monocytic cells stimulated with lipopolysaccharide of oral microorganisms

Cytokines, including granulocyte-macrophage colony-stimulating factor (GM-CSF), are used to assist in bone marrow recovery during cancer chemotherapy. Interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) play important roles in inflammatory processes, including exacerbation of periodontal diseases, one of the most common complications in patients who undergo this therapy. A human monocyte cell line (THP-1) was utilized to investigate IL-1beta and TNF-alpha production following GM-CSF supplementation with lipopolysaccharide (LPS) from two oral microorganisms, Porphyromonas gingivalis and Fusobacterium nucleatum. LPS of P. gingivalis or F. nucleatum was prepared by a phenol-water extraction method and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and determination of total protein and endotoxin contents. Resting THP-1 cells were treated with LPS of P. gingivalis or F. nucleatum and/or GM-CSF (50 IU/ml) by using different concentrations for various time periods. Production of IL-1beta and TNF-alpha in THP-1 cells was measured by solid-phase enzyme-linked immunosorbent assay. Reverse transcription (RT)-PCR was used to evaluate the gene expression of resting and treated THP-1 cells. IL-1beta was not detected in untreated THP-1 cells. IL-1beta production was, however, stimulated sharply at 4 h. GM-CSF amplified IL-1beta production in THP-1 cells treated with LPS from both oral anaerobes. No IL-1beta-specific mRNA transcript was detected in untreated THP-1 cells. However, IL-1beta mRNA was detected by RT-PCR 2 h after stimulation of THP-1 cells with LPS from both organisms. GM-CSF did not shorten the IL-1beta transcriptional activation time. GM-CSF plus F. nucleatum or P. gingivalis LPS activated THP-1 cells to produce a 1.6-fold increase in TNF-alpha production at 4 h over LPS stimulation alone. These investigations with the in vitro THP-1 model indicate that there may be an increase in the cellular immune response to oral endotoxin following GM-CSF therapy, as evidenced by production of the tissue-reactive cytokines IL-1beta and TNF-alpha.

Cytopathic effects of the major surface protein and the chymotrypsinlike protease of Treponema denticola

Prominent antigens of Treponema denticola have been suggested to be mediators of the cytopathic effects typically seen in periodontal disease. In the present study of the T. denticola major surface protein (Msp) and the surface-expressed chymotrypsinlike protease complex (CTLP), we characterized the ability of these proteins to adhere to and lyse epithelial cells. Msp and CTLP were closely associated in spirochete outer membranes. Purified Msp, both native and recombinant, and CTLP bound to glutaraldehyde-fixed periodontal ligament epithelial cells. Adherence of Msp was partially blocked by specific antibodies. Adherence of CTLP was partially blocked by serine protease inhibitors and was further inhibited by specific antibodies. Both native Msp and CTLP were cytotoxic toward periodontal ligament epithelial cells, and their cytotoxicity was inhibited by the same treatments that inhibited adherence. Msp, but not CTLP, lysed erythrocytes. Msp complex (partially purified outer membranes free of protease activity) was cytotoxic toward a variety of different cell types. Pore-forming activities of recombinant Msp in black lipid model membrane assays and in HeLa cell membranes were similar to those reported for the native protein, supporting the hypothesis that Msp cytotoxicity was due to its pore-forming activity.

Association of oral spirochetes from periodontally healthy sites with development of gingivitis

The purpose of this investigation was to determine whether the presence of selected disease-associated bacteria in health-associated plaque correlated with future gingivitis. Sites of periodontal health were identified in 65 adults. Six months later (recall 1) plaque was collected from sites that remained in periodontal health, and 5 species of specific bacteria and pathogen-related oral spirochetes were detected using monoclonal antibodies in a microscopic assay. Members of the spirochete morphogroup were also identified by phase contrast microscopy. The relationship between site-specific detection of bacteria at recall 1 and development of gingivitis at recall 2 or 3 was evaluated by means of logistic regression using generalized estimating equations, from which odds ratios (OR) were estimated. Significance was conservatively defined as OR > 2.0 and P < 0.05. We found that 488 of 1,424 healthy sites developed gingivitis over the 12-month interval between recall 1 and 3. Only the spirochete morphogroup (OR =2.04; P=0.002) was significantly associated with the transition from health to gingivitis. The association of Treponema socranskii with future gingivitis was higher than expected (OR=2.27), but the relationship was not statistically significant (P=0.163). Campylobacter rectus, Eikenella corrodens, Porphyromonas gingivalis, and pathogen-related oral spirochetes did not correlate well with gingivitis (OR < 2.0). Health-associated plaque from 5 sites contained Treponema denticola, and all 5 sites progressed to gingivitis. An OR could not be calculated because T. denticola was not detected in health-associated plaque from stable healthy sites. These findings indicated that the presence of T. denticola and unidentified spirochetes in health-associated plaque was associated with increased susceptibility to gingival inflammation. Future studies assessing a larger panel of dental plaque microorganisms, with shorter intervals between baseline and follow-up assessment, are necessary to more fully evaluate the association between detection of specific organisms at healthy sites and risk for gingivitis.

Porphyromonas gingivalis, Prevotella intermedia and Bacteroides forsythus in plaque subjacent to bridge pontics

This study examined the distribution of P. gingivalis, P. intermedia and B. forsythus in plaque on metallic and porcelain pontics adjacent to healthy and inflamed mucosa. Subpontic plaque was collected from 33 inflamed and 31 healthy sites. Plaque suspension was incubated with specific rabbit antisera to P. gingivalis (FDC 381), P. intermedia (ATCC 25261) and B. forsythus (FDC 335), and the labelled cells disclosed with fluorescein-labelled goat-anti-rabbit IgG by indirect immunofluorescence microscopy. Mean proportions of P. gingivalis, P. intermedia, and B. forsythus at inflamed sites were 0.60+/-0.75, 2.48+/-2.28, and 0.44+/-0.64% respectively, and at healthy sites 0.21+/-0.43, 1.27+/-1.05, and 0.15+/-0.18% respectively. These differences were statistically significant. Almost all sites were positive for P. intermedia, whereas only 12/31 healthy and 21/33 inflamed sites were positive for P. gingivalis. 18/31 healthy and 28/33 inflamed sites were positive for B. forsythus. P. intermedia was recovered in higher proportions from metallic pontics adjacent to inflamed sites (MI) than healthy sites (MH) or porcelain pontics next to inflamed (PI) or healthy sites (PH). P. gingivalis is was recovered in higher proportions from MI than PH. We conclude that both the nature of the pontic material and the health status of the mucosa affect the composition of the associated microbiota.

Studies on fusobacteria associated with periodontal diseases

The physiological and metabolic characteristics of representative isolates of the various subspecies of Fusobacterium nucleatum were investigated by growing them in continuous culture in chemically-defined, media. Behaving almost identically, these organisms were found to obtain energy from the fermentation of simple carbohydrates such as glucose or fructose or from the fermentation of certain amino acids, free or in the form of small peptides. The latter can be attacked by aminopeptidase activity which was shown to be essential for the growth of the organism in an environment lacking fermentable carbohydrate and free amino acids but replete with small peptides. This metabolic versatility may explain the presence of F. nucleatum in both supra- and sub-gingival dental plaque and why it is often found together with organisms such as Porphyromonas gingivalis which display powerful endopeptidase activities. Using the technique of allozyme electrophoresis, the current subspeciation of F. nucleatum was shown to be of doubtful validity and evidence, based upon physiological and metabolic properties, for differences in pathogenicity between isolates was not detected. While this organism is a member of various bacterial consortia associated with periodontal diseases, its contribution to the disease process remains unclear.

Prevalence of Peptostreptococcus micros morphotypes in patients with adult periodontitis

The prevalence of the smooth and rough colonial morphotypes of Peptostreptococcus micros was examined with culture technique in 123 patients with adult periodontitis (age 24-68 years). Of all subgingival samples, 91% contained the smooth morphotype of P. micros. The smooth morphotype constituted a mean percentage of the total anaerobic viable biota of 6.0%, with a range of 0.02-35.7%. Of these samples, 49% contained colonies of the rough morphotype as well, with a mean percentage of the total anaerobic viable biota of 2.3% (range 0.01-16.2%). None of the samples contained only the rough morphotype. The total percentage of P. micros varied from 0.02-35.71% with a mean of 7.2%. No correlation was found between the prevalence of both morphotypes of P. micros and the age of the subjects or with loss of attachment or pocket depth.

Restriction fragment-length polymorphism analysis of 16S rDNA from oral asaccharolytic Eubacterium species amplified by polymerase chain reaction

Restriction fragment-length polymorphism (RFLP) analysis of 16S rDNA amplified by polymerase chain reaction was used to generate restriction profiles of the type strains of oral asaccharolytic Eubacterium species, that is, Eubacterium brachy, Eubacterium exiguum, Eubacterium lentum, Eubacterium minutum, Eubacterium nodatum, Eubacterium saphenum, Eubacterium timidum and 33 asaccharolytic Eubacterium strains isolated from oral sites. The 16S rRNA gene sequences from isolated genomic DNA samples were amplified by polymerase chain reaction (PCR). PCR products were purified and characterized by single digestions with 7 restriction endonucleases. Among the 7 endonucleases, HpaII was found to discriminate the respective reference strains. Twenty-three isolates, out of 33, were assigned to one of the reference species, on the basis of their restriction profiles by digestion with HpaII. The remaining 10 isolates could not be assigned to any of the established species and constituted 4 distinct groups, each of which may be a new species.

Microbiota of health, gingivitis, and initial periodontitis

This study compared the subgingival microbiota in periodontal health, gingivitis and initial periodontitis using predominant culture and a DNA probe, checkerboard hybridization method. 56 healthy adult subjects with minimal periodontal attachment loss were clinically monitored at 3-month intervals for 12 months. More sites demonstrated small increments of attachment loss than attachment gain over the monitoring period. Sites, from 17 subjects, showing > or = 1.5 mm periodontal attachment loss during monitoring were sampled as active lesions for microbial analysis. Twelve subjects demonstrated interproximal lesions, and 5 subjects had attachment loss at buccal sites (recession). Cultural studies identified Bacteroides forsythus, Campylobacter rectus, and Selenomonas noxia as the predominant species associated with active interproximal lesions (9 subjects), whereas Actinomyces naeslundii, and Streptococcus oralis, were the dominant species colonizing buccal active sites. A. naeslundii, Campylobacter gracilis, and B. forsythus (at lower levels than active sites) were the dominant species cultured from gingivitis (10 subjects). Health-associated species (10 subjects) included Streptococcus oralis, A. naeslundii, and Actinomyces gerencseriae. DNA probe data identified higher mean levels of B. forsythus and C. rectus with active (7 subjects) compared to inactive periodontitis sites. Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans were detected infrequently. Cluster analysis of the cultural microbiota grouped 8/9 active interproximal lesions in one subcluster characterized by a mostly gram-negative microbiota, including B. forsythus and C. rectus. The data suggest that B. forsythus C. rectus and S. noxia were major species characterizing sites converting from periodontal health to disease. The differences in location and microbiota of interproximal and buccal active sites suggested that different mechanisms may be involved in increased attachment loss.

Subgingival microbiota of shallow periodontal pockets in individuals after head and neck irradiation

This study aimed at investigating the subgingival plaque microorganisms of shallow pockets (< or = 5 mm) in subjects who previously received irradiation in the head and neck region for treatment of nasopharyngeal carcinoma. Direct microscopy and anaerobic culture were used. Subgingival paper point samples were taken from 6 tooth-sites (one/sextant) per subject for direct microscopy (n = 108). Another set of paper points was taken from the deepest of the previously selected sites (one per subject) with: group A) no bleeding on probing to the sulcus depth (n = 9) and group B) bleeding on probing to the sulcus depth (n = 6) for microscopic and anaerobic culture study. Under the microscope, the microflora was found to be a complex mixture comprising gram-positive and gram-negative cocci, rods and filaments, fusiforms, curved rods and spirochetes. Low level of fungi were observed and mycelia were occasionally detected. There was no significant variation in the plaque bacterial morphotypes observable according to sites of isolation and no significant difference between group A and group B in morphotypes of the different microflora. The predominant cultivable microflora comprised several species of facultative and obligate anaerobic bacteria: Gemella, Peptostreptococcus, Staphylococcus, Stomatococcus, Streptococcus, Actinomyces, Eubacterium, Lactobacillus, Propionibacterium, Neisseria, Veillonella, Bacteroides, Campylobacter, Capnocytophaga, Fusobacterium, Kingella, Porphyromonas and Prevotella species. There was no difference between the two groups except the significantly higher proportion of Kingella dentrificans isolated from group B sites. However, colonization of the gingival sulcus in these individuals by microbes that are normal flora of: skin (Peptostreptococcus prevotii and Propionibacterium granulosum) and gut (Eubacterium aerofaciens, Fusobacterium mortiferum and Fusobacterium varium) was detected. These findings appear to suggest that the major components of the subgingival microflora of shallow sites in previously head- and neck-irradiated individuals are similar to that of gingivitis sites in the normal population although they may contain bacterial or fungal species uncommon in normal subjects.

beta-Lactamase-producing strains in the species Prevotella intermedia and Prevotella nigrescens

A total of 96 strains were collected that included laboratory strains and clinical isolates classified Prevotella intermedia sensu lato and the type strains of the species P. intermedia sensu stricto and Prevotella nigrescens. Susceptibility to amoxicillin and amoxicillin-clavulanic acid was determined by the Etest. PCR-DNA probe assays were used to speciate each strain as P. intermedia sensu stricto or P. nigrescens. By Etest, 71 strains (74%) were susceptible to both amoxicillin and amoxicillin-clavulanic acid with minimum inhibitory concentrations in the 0.016-0.064 microgram/ml range. In contrast, amoxicillin minimum inhibitory concentrations of 25 strains (26%) were in the range of 1.5-96 micrograms/ml with concomitant amoxicillin-clavulanic acid minimum inhibitory concentrations in the low range 0.016-0.38 microgram/ml, indicating a production of beta-lactamase as confirmed by nitrocefin tests. Of these beta-lactamase-producing strains, 20% (5/25) were identified as P. intermedia sensu stricto by the PCR-DNA probe assay and 72% (18/25) as P. nigrescens. Our results provide support for the major role of P. nigrescens in the failure of therapy using beta-lactam antibiotics.

Characterization of a novel N-acetylneuraminic acid-specific Fusobacterium nucleatum PK1594 adhesin

Fusobacterium nucleatum has been identified as significantly associated with sites with active periodontal disease and, as a group, the oral fusobacteria coaggregate with members of all oral bacteria genera tested. Monoclonal antibodies were prepared and used in conjunction with other potential inhibitors, such as simple sugars and amino acids, to characterize coaggregation interactions, of F. nucleatum PK1594. Four unique monoclonal antibodies, 5H11, 14C7, 19F2 and 29C12, were obtained by their ability to inhibit coaggregation of F. nucleatum PK1594 with Actinomyces israelii PK16. They were also capable of inhibiting other coaggregations including Streptococcus oralis H1, S. oralis J22, Capnocytophaga ochracea ATCC33596, Prevotella denticola PK1277 and Prevotella intermedia PK1511. All of these interactions were completely inhibited by N-acetylneuraminic acid. Neither N-acetylneuraminic acid nor monoclonal antibody 5H11 had any inhibitory effect on other F. nucleatum PK1594 interactions, including all galactose-inhibitable coaggregations. The results indicate that F. nucleatum PK1594 expresses upon its surface a distinct type of adhesin that mediates coaggregation interactions that are inhibited by N-acetylneuraminic acid.

Gram-positive anaerobic cocci

Gram-positive anaerobic cocci (GPAC) are a heterogeneous group of organisms defined by their morphological appearance and their inability to grow in the presence of oxygen; most clinical isolates are identified to species in the genus Peptostreptococcus. GPAC are part of the normal flora of all mucocutaneous surfaces and are often isolated from infections such as deep organ abscesses, obstetric and gynecological sepsis, and intraoral infections. They have been little studied for several reasons, which include an inadequate classification, difficulties with laboratory identification, and the mixed nature of the infections from which they are usually isolated. Nucleic acid studies indicate that the classification is in need of radical revision at the genus level. Several species of Peptostreptococcus have recently been described, but others still await formal recognition. Identification has been based on carbohydrate fermentation tests, but most GPAC are asaccharolytic and use the products of protein degradation for their metabolism; the introduction of commercially available preformed enzyme kits affords a physiologically more appropriate method of identification, which is simple and relatively rapid and can be used in routine diagnostic laboratories. Recent reports have documented the isolation in pure culture of several species, notably Peptostreptococcus magnus, from serious infections. Studies of P. magnus have elucidated several virulence factors which correlate with the site of infection, and reveal some similarities to Staphylococcus aureus. P. micros is a strongly proteolytic species; it is increasingly recognized as an important pathogen in intraoral infections, particularly periodontitis, and mixed anaerobic deep-organ abscesses. Comparison of antibiotic susceptibility patterns reveals major differences between species. Penicillins are the antibiotics of choice, although some strains of P. anaerobius show broad-spectrum beta-lactam resistance.

Identification of a Fusobacterium nucleatum PK1594 galactose-binding adhesin which mediates coaggregation with periopathogenic bacteria and hemagglutination

Attachment of Fusobacterium nucleatum to various oral surfaces is mediated by several adhesins anchored on its outer surface. Monoclonal antibodies (MAbs) were prepared and used to identify the putative galactose-binding adhesin of F. nucleatum PK1594. Four unique MAbs, 8G7, 26B9, 28G11, and 29D4, were isolated on the basis of their ability to inhibit coaggregation of F. nucleatum PK1594 with Porphyromonas gingivalis PK1924. All four MAbs were also capable of inhibiting galactose-inhibitable interactions of F. nucleatum PK1594 with other oral gram-negative bacteria and with erythrocytes. Preincubation of F. nucleatum PK1594 with MAb 26B9 or its Fab fragments at concentrations lower than 1 microg/ml resulted in complete inhibition of coaggregation with P. gingivalis PK1924 or hemagglutination. F. nucleatum PK1594 surface components prepared by mild sonication or by extracting whole cells with detergents were subjected to Western blot analysis. None of the MAbs were able to recognize any polypeptide in these experiments. Therefore, detergent extracts of F. nucleatum PK1594 surface components were subjected to three experimental procedures: (i) separation by ion-exchange chromatography and testing of fractions for reaction with MAb 26B9 in an enzyme-linked immunosorbent assay (ELISA), (ii) lactose-Sepharose affinity chromatography and testing of the lactose eluate in ELISA with MAb 26B9, and (iii) immunoseparation with either MAb 26B9 or 8G7. Collectively, the results suggest that the putative adhesin is a 30-kDa outer membrane polypeptide which mediates the coaggregation with P. gingivalis PK1924 as well as other galactose-sensitive interactions of F. nucleatum PK1594.

Association of oral spirochetes from sites of periodontal health with development of periodontitis

The purpose of this investigation was to determine whether the presence of disease-associated bacteria in health-associated plaque correlated with susceptibility to periodontitis over time. Sites of periodontal health were identified in 65 adults. Six months later (recall 1), plaque was collected from sites that remained in periodontal health, and specific bacteria were detected using monoclonal antibodies in a microscopic assay. The spirochete morphogroup was identified by phase contrast microscopy. The relationship between detection at recall 1 and development of periodontitis over two successive 6-month intervals (recalls 2 and 3) was evaluated by means of logistic regression using generalized estimating equations (GEE), from which odds ratios (OR) were estimated and tested for significance. Significant relationships were defined as those having ORs with P < 0.05. Ninety-three of 1,032 sites developed signs of early periodontitis over the 12-month interval between recall 1 and recall 3. The spirochete morphogroup (OR = 3.13, P < 0.001) and pathogen-related oral spirochetes (PROS) (OR = 3.68, P < 0.001) were significantly associated with healthy sites that developed periodontitis. The association of Treponema socranskii was not significant (OR = 3.62, P = 0.0918). Odds ratios for Campylobacter rectus, Eikenella corrodens, and Porphyromonas gingivalis were less than 2.0 and not significant. Treponema denticola was not detected in health-associated plaque from stable health sites and was detected in only three sites that progressed to periodontitis. These findings indicate that the presence of PROS and some unidentified spirochetes in health-associated plaque is associated with increased susceptibility to periodontitis.

Serum antibodies to Porphyromonas gingivalis block the prostaglandin E2 response to lipopolysaccharide by mononuclear cells

The ability of rabbit and monkey immune sera to neutralize prostaglandin E2 (PGE2) production by human monocytes stimulated with lipopolysaccharide (LPS) was examined. CD14-dependent LPS activation of PGE2 was examined under assay conditions which allowed the comparison of preimmune and immune sera. Serum obtained from rabbits immunized with formalin-fixed Porphyromonas gingivalis cells dramatically reduced the amount of PGE2 produced in response to LPS obtained from three different strains of P. gingivalis but not that from Escherichia coli or Bacteroides fragilis. In addition, a significant reduction in the mean PGE2 level was observed in the presence of sera from immunized but not control monkeys employed in a vaccine trial. Immune serum samples from five of nine immunized monkeys were able to reduce LPS-induced production of PGE2 by greater than 50% compared to that in the corresponding preimmune sera. Immune monkey serum, similar to immune rabbit serum, blocked PGE2 production in response to P. gingivalis LPS but not E. coli LPS. These data demonstrate that immunization with P. gingivalis whole cells can elicit an antibody response that is able to block the PGE2 response to LPS. Neutralization of LPS-mediated inflammatory mediator production may account in part for the observed suppression of alveolar bone loss in immunized monkeys.

Identification, isolation, and characterization of the 42-kilodalton major outer membrane protein (MompA) from Treponema pectinovorum ATCC 33768

The major protein present in the isolated outer membrane of Treponema pectinovorum ATCC 33768, MompA, was identified, purified, and characterized. Immuno-gold electron microscopy, using anti-MompA serum, and cell fractionation experiments confirmed the localization of MompA to the outer membrane. MompA was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to have a molecular mass of 42 kDa when heat denatured, whereas native MompA formed a number of detergent-stable forms with molecular masses of 71, 76, and 83 kDa. A temperature of 60 degrees C was required to convert the native protein to the 42-kDa form. A number of detergents and chemical agents that are capable of breaking ionic and hydrogen bonds of proteins did not convert native MompA to the 42-kDa species. The native forms of the protein were resistant to the combined action of proteinase K, trypsin, and chymotrypsin, whereas the 42-kDa form of MompA was not. The N-terminal amino acid sequence of MompA was determined to be DVTVNINSRVRPVLYTT, and database searches did not identify any homology with known protein sequences. Amino acid compositional analysis showed the protein to be rich in proline and glycine, with these amino acids accounting for 28 and 13%, respectively, of the total amino acids. Antiserum raised against the major outer membrane protein of T. denticola GM-1 and ATCC 35405 did not cross-react with MompA, and antiserum raised against MompA did not react with any cellular components of Treponema denticola, Treponema vincentii, or Treponema socranskii. A major outer membrane protein similar in molecular mass to MompA was identified in eight clinical isolates of T. pectinovorum. The major outer membrane protein produced by four of the clinical isolates reacted strongly, by Western blotting, with anti-MompA serum, whereas proteins of the other strains did not.

Arbitrarily primed polymerase chain reaction fingerprinting and clonal analysis of oral Fusobacterium nucleatum isolates

F. nucleatum is the most commonly isolated microorganism from subgingival plaque, but the role of this microorganism in periodontal diseases remains undefined. Arbitrarily primed polymerase chain reaction (AP-PCR) was evaluated as a method for fingerprinting F. nucleatum isolates and for use in clonal analysis. Pulsed field gel electrophoresis was used to further differentiate F. nucleatum isolates, with identical AP-PCR patterns. Extremely heterogeneous AP-PCR fingerprints were observed among the 98 F. nucleatum isolates, with 36 different genotypes observed with primer C1 and 30 different genotype detected with primer C2. Combining the results of the AP-PCR genotype analysis from C1 and C2 primer amplifications revealed that up to 7 different genotypes could be distinguished from isolates from the same oral cavity and that up to 4 different genotypes were observed within a single site. An intense amplicon at approximately 450 bp generated in AP-PCR amplification with primer C2 was associated with F. nucleatum subsp. nucleatum (ATCC 25586) and with 15 F. nucleatum isolates from diseased sites and 2 isolates from healthy sites. Pulsed field gel electrophoresis confirmed the AP-PCR genotypes and demonstrated increased discriminatory power over AP-PCR. The results indicated that AP-PCR and pulsed field gel electrophoresis provide a simple and sensitive means for differentiating oral F. nucleatum isolates and further demonstrate the heterogeneity of this species. These techniques may serve as useful tools in the clonal and epidemiological analysis of F. nucleatum isolates, which may help define the role of these microorganisms in periodontal diseases.

A cell-associated protein complex of Porphyromonas gingivalis W50 composed of Arg- and Lys-specific cysteine proteinases and adhesins

Porphyromonas gingivalis has been associated with the development of adult periodontitis and cysteine proteinases with trypsin-like specificity have been implicated as major virulence factors. We have extracted the major cell-associated trypsin-like proteolytic activity of P. gingivalis W50 using mild sonication. Anion-exchange and gel-filtration FPLC of the sonicate revealed that Arg- and Lys-specific proteinase activity was associated with a 300 kDa complex which could be dissociated into seven bands (48, 45, 44, 39, 27, 17 and 15 kDa) by SDS-PAGE with the 44 kDa band containing two different proteins as shown by N-terminal sequence analysis. On further chromatography of the 300 kDa complex on Arg-Sepharose the majority of the complex eluted from the affinity column as an undissociated complex. However, a small amount dissociated such that the Lys- and Arg-specific activities could be separated by eluting first with lysine then arginine, respectively. The 45 kDa protein of the complex was purified by further anion-exchange FPLC in the presence of octyl-beta-D-glucopyranoside and was shown to be an Arg-specific, thiol-activated, calcium-stabilized cysteine proteinase. The 48 kDa protein was also further purified in a similar fashion and shown to be a Lys-specific cysteine proteinase that was not inhibited by EDTA. The two 44 kDa and the 39, 27, 17 and 15 kDa proteins of the complex exhibit amino acid sequence homology and are proposed to be haemagglutinins/adhesins. The 45 kDa Arg-specific proteinase and one of the 44 kDa adhesins as well as the 15, 17 and 27 kDa adhesins are processed from the single polyprotein encoded by the gene designated prtR, with all proteins preceded by an Arg or Lys residue within the polyprotein. Similarly, the 48 kDa Lys-specific proteinase, the 39 and 15 kDa adhesins as well as the other 44 kDa adhesin of the 300 kDa complex are encoded by a single gene designated prtK, with all proteins preceded by an Arg or Lys residue within the polyprotein. The 39, 15 and 44 kDa adhesins of PrtK all exhibit high homology with the 44, 15, 17 and 27 kDa adhesins encoded by prtR, particularly the 15 kDa proteins which are identical. The cell-associated proteinase-adhesin complex, designated PrtR-PrtK, is therefore composed of the two gene products, the mature PrtR (160 kDa) and mature PrtK (163 kDa) that are further proteolytically processed (most likely autolytically) to release proteinase and adhesin domains that remain non-covalently associated. The fully processed PrtR-PrtK complex comprises the cysteine proteinases-PrtR45 and PrtK48 and seven sequence-related adhesin molecules, PrtR44, PrtR15, PrtR17, PrtR27 and PrtK39, PrtK15 and PrtK44. We propose that this proteinase-adhesin complex is a major virulence factor for P. gingivalis involved in the evasion of host defence and in the assimilation of haem and peptides.

PCR-DNA probe assays for identification and detection of Prevotella intermedia sensu stricto and Prevotella nigrescens

The purpose of this study was to construct PCR-DNA probe assays specific for Prevotella intermedia sensu stricto and Prevotella nigrescens based on the ability of randomly amplified polymorphic DNA (RAPD) fingerprinting to generate species-specific markers. The strategy included four steps: (i) construction of first-generation DNA probes from a 850-bp RAPD marker for P. intermedia sensu stricto and a 1,300-bp RAPD marker for P. nigrescens, (ii) cloning and sequencing of each RAPD marker, (iii) designing of primer pairs flanking specific internal sequences of 754 bp for P. intermedia sensu stricto and of ca. 1,100 bp for P. nigrescens, and (iv) synthesis (by PCR amplification) and digoxigenin labeling of quantities of DNA probes 754 and ca. 1,100 bp in size. The PCR-DNA probe assays combine either PCR amplification of a 754-bp specific sequence in the genomic DNA of strains of P. intermedia sensu stricto and hybridization with the 754-bp digoxigenin-labeled probe or amplification of a ca. 1,100-bp sequence of P. nigrescens and hybridization with the ca. 1,100-bp probe. Specific hybridization was observed with the amplified DNAs from 25 strains of P. intermedia and 24 strains of P. nigrescens, and no reaction was observed with the PCR products from 20 foreign species. The PCR-DNA probe assays described here should allow a highly specific and sensitive detection of P. intermedia sensu stricto and P. nigrescens in mixed infections.

Characterization of Bacteroides forsythus isolates

Fifteen Bacteroides forsythus strains freshly isolated from patients with periodontitis were used together with three collection strains and one type strain for characterization of growth on various media; determination of enzymatic profiles, antibiotic susceptibility profiles, 16S rRNA ribotypes, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) outer membrane protein profiles, and pathogenicity; and gas chromatography analysis by using a wound chamber model in rabbits. All strains were stimulated by N-acetylmuramic acid, while one strain needed a further supplement such as yeast extract for optimal growth. All strains showed trypsin-like activity. While 10 different ribotypes were found, the SDS-PAGE profiles revealed similar patterns for all strains. All strains were sensitive to penicillin G (MICs, <0.5 microg/ml), ampicillin (MICs, <1.0 microg/ml), amoxicillin (MICs, <0.38 microg/ml), metronidazole (MICs, <0.005 microg/ml), tetracycline (MICs, <0.19 microg/ml), doxycycline (MICs, 0.05 microg/ml), erythromycin (MICs, <0.4 microg/ml), and clindamycin (MICs, <0.016 microg/ml), while they were less sensitive to ciprofloxacin (MICs, <4 microg/ml). B. forsythus did not cause abscess formation by monoinoculation. B. forsythus coinoculated with Fusobacterium nucleatum ATCC 10953 caused abscess formation in 75% of rabbits, while it caused abscess formation in 100% of rabbits when it was coinoculated with Porphyromonas gingivalis FDC 381. In the case of the latter combination, four of six rabbits died of sepsis after 6 to 7 days, and P. gingivalis and B. forsythus were recovered from the heart blood at a proportion of 10:1. B. forsythus strains were highly virulent and invasive in combination with P. gingivalis.

Pathogenicity of Prevotella intermedia and Prevotella nigrescens isolates in a wound chamber model in rabbits

The pathogenicity of 14 isolates identified as Prevotella intermedia or Prevotella nigrescens by serogrouping using monoclonal antibodies was compared in a tissue cage model in rabbits. Seven strains from periodontal abscesses, 5 strains from deep periodontal pockets and 2 strains from gingivitis were tested in the animal model comprising 6 Teflon tissue cages implanted on the back each of 34 rabbits. A total of 10(5)-10(8) cells of P. intermedia or P. nigrescens strains were inoculated alone or together with either Actinobacillus actinomycetemcomitans or Streptococcus mitis. Five strains of Porphyromonas gingivalis were used as a reference. The infectivity was recorded as pus formation and log viable count in aspirated material for 3, 7 and 14 days. None of the Prevotella strains inoculated in monoculture survived more than 3 days, and they had no capacity to produce abscess. P. intermedia or P. nigrescens strains in combination with A. actinomycetemcomitans produced abscesses in 33-100% and with S. mitis in 42-100%. No difference in abscess formation or log viable count in samples after 14 days was recorded between serogroup I (P. intermedia) and serogroup II and III (P. nigrescens). The infectivity of P. intermedia or P. nigresceas strains did not differ whether they were isolated from periodontal abscess, periodontal pocket or gingivitis. P. intermedia and P. nigrescens strains produced abscesses in combination with a facultative anaerobic strain and appears to have a similar pathogenicity in the wound chamber model in rabbits.

The bactericidal effects of dental ultrasound on Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. An in vitro investigation

This study investigated the possible bactericidal acoustic effects of the dental ultrasonic scaler. Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis suspensions, were subjected to the vibrations of a Cavitron P1 insert for 2.5 and 5.0 min in an acoustically-simulated pocket model and the survivors enumerated. The extent of any cavitation occurring within the pocket model to which the statistically significant bactericidal activity observed might be attributed, was determined by 'sonoluminescence', which was then investigated by photomultiplication techniques. However, these failed to detect any sonoluminescence within the pocket space and, moreover, the necessary deflection of the water coolant away from the insert tip, to avoid flooding of the experimental pocket, proved to result in temperatures of 47.6 degrees C and 52.3 degrees C at the respective time intervals, and thereby constituted an alternative possible bactericidal mechanism. Examination of the effects of such temperature changes on the target bacteria then revealed statistically significant differences in the viable counts of both microorganisms after 5.0-min periods, and as such were comparable to those previously detected in relation to the pocket model. Whilst it must be presumed that the bacteriolytic effect observed in the main investigation was due to the incidental temperature changes, in the absence of acoustic cavitation the influence of any associated acoustic microstreaming cannot be discounted. Further investigations to assess the bactericidal potential of acoustic phenomena using a modified experimental to exclude any hyperthermic effects are therefore necessary.

Intra-familial transmission and distribution of Prevotella intermedia and Prevotella nigrescens

The periodontal bacteria Prevotella intermedia and Prevotella nigrescens have been recently separated from each other. The purpose of this study was to investigate the distribution and routes of transmission of these bacteria among family members. Seven patients with moderate to severe periodontitis were selected. These probands, their spouses and 14 of their children were investigated. The presence of Pr. intermedia and Pr. nigrescens was determined by culture techniques in pooled subgingival plaque samples, in the saliva, on the tongue, tonsils and buccal mucosa. Differentiation of Pr. intermedia and Pr. nigrescens was performed by enzyme electrophoretic mobility. From all 7 patients, as well as 4 spouses and 3 of the children, Pr. intermedia could be isolated. Pr. nigrescens was found in 2 of the 7 patients, in 5 of the spouses and in 5 of the 6 children aged 5-10 yr. In the 8 children aged 0-4 yr both species were seldom isolated. These data are in accordance with earlier findings that Pr. intermedia is associated with periodontitis and Pr. nigrescens with a relatively healthy periodontal condition. Ribotyping of bacteria was performed by hybridization of HindIII restriction endonuclease digests of chromosomal DNA with ribosomal DNA. Isolates from unrelated individuals always had distinct ribotypes. Indistinguishable ribotypes of Pr. intermedia and Pr. nigrescens were found both among married couples and among parents and children. This indicates that intrafamilial transmission of Pr. intermedia and Pr. nigrescens is possible both between adults and between parents and children.

Release and activation of human neutrophil matrix metallo- and serine proteinases during phagocytosis of Fusobacterium nucleatum, Porphyromonas gingivalis and Treponema denticola

The phagocytic ingestion of reference strains and clinical isolates of Fusobacterium nucleatum, Porphyromonas gingivalis, and Treponema denticola by polymorphonuclear leukocytes (PMNs) and the concomitant release of PMN granule proteinases were studied by specific functional and immunological assays. PMNs were incubated with the microorganisms anaerobically at 37 degrees C for indicated time periods. The suspensions and pellets were used for phagocytic ingestion assay and electron microscopic study, respectively. The supernatants were used for the measurements of the amounts and activities of the released PMN enzymes including PMN gelatinase (MMP-9), collagenase (MMP-8), serine proteases (elastase and cathepsin G), and lactate dehydrogenase (LDH). Both fluorescence microscopy and transmission electron microscopy showed that F. nucleatum, P. gingivalis and T. denticola were ingested by the PMNs in comparable numbers. However, measurements of the enzymes released from the triggered PMNs revealed major differences among the three species. High amount of elastase was released from the PMNs triggered by F. nucleatum, but not by P. gingivalis or T. denticola. The treatment of PMNs with P. gingivalis whole cells resulted in the release of gelatinase partly in the 82 kD active form, suggesting proteolytic activation of the degranulated 92 kD proMMP-9. The 82 kD active form of gelatinase was not detected upon triggering the PMNs with F. nucleatum and T. denticola. The PMN-bacteria interaction did not result in release of LDH from triggered PMNs indicating the proteinase release was not due to the PMN cell death. The results show that the susceptibilities of the 3 potentially periodontopathogenic microorganisms, F. nucleatum, P. gingivalis and T. denticola to phagocytic ingestion are not directly related to the amounts and activities of PMN enzymes released during the bacteria-PMN interactions. As PMN degranulation is considered as one of the major pathogenic mechanisms in periodontitis, the observed differences among the microorganisms may be important virulence characteristics of these species.

Concordance of Porphyromonas gingivalis colonization in families

Periodontitis is a widespread disease that appears to be due to a specific bacterial infection. Several species of bacteria have been investigated as potential pathogens, and particularly strong evidence links the presence of Porphyromonas gingivalis with indicators of periodontitis. Information concerning the transmission of P. gingivalis between human contacts may be important in determining risk factors for disease and developing preventive strategies. A few small studies have provided some evidence of transmission between related individuals, but no large-scale study of families that would reflect the typical transmission of this pathogen in the population has been reported. The purpose of this study was to investigate the transmission of P. gingivalis within randomly selected, extended families. The colonization status of 564 members of multigeneration families was determined, and the degree of concordance observed among members of these families was then compared to that expected to occur based on the prevalence of colonization in the population studied. A PCR assay was used for detection of P. gingivalis. Concordance in colonization was more frequently observed within entire families (P = 0.0000) and for spouses (P < 0.001), children and their mothers (P < 0.001), children and their fathers (P < 0.01), adults and their mothers (P < 0.005), and siblings (P < 0.05) than would be expected if P. gingivalis were randomly distributed in the population studied. Results showed that contact with an infected family member substantially increased the relative risk of colonization in these intrafamilial pairs. This indicates that P. gingivalis is commonly transmitted by contact with an infected family member.

Experimental apexigenesis in baboons

Apexification with calcium hydroxide is a routine procedure. However, some clinical reports suggest that root completion can occur by controlling the infection without use of a catalyst. The present study investigated the use of tetracycline treatment (in root canals) on root growth in immature teeth, rendered non-vital experimentally. Incisors in 3 young baboons were exposed and canals were left open. After 2 months all canals were cleaned and treated with either tetracycline or formocresol. Some canals in each group were filed. Animals were sacrificed after 6 months. Bacterial evaluations were done before placing medications, one week later and six months after that. The number of bacteria were reduced in all treatment groups. Root growth almost near completion was observed in more teeth treated with tetracycline than in the formocresol group.

Occurrence of Porphyromonas gingivalis, Bacteroides forsythus, and Treponema denticola in periodontally healthy and diseased subjects as determined by an ELISA technique

The aim of this study was to assess by means of an ELISA technique, the occurrence of 3 putative periodontopathogens, Porphyromonas gingivalis, Bacteroides forsythus, and Treponema denticola, in 3 clinically-defined adult periodontal conditions. Thirty systemically-healthy subjects were selected and grouped into 3 categories according to their periodontal health: 1) 10 periodontitis subjects (PS), having moderate adult chronic periodontitis; 2) 10 untreated gingivitis subjects (UGS), exhibiting no signs of periodontal destruction but presenting with clinical signs of mild gingivitis; and, 3) 10 treated gingivitis subjects (TGS), having the same clinical status as UGS, but who received a thorough prophylaxis treatment within the past 7 to 14 days prior to the baseline examination. A total of 60 samples were collected subgingivally from the six Ramfjord teeth per subject in each group and ELISA analysis was carried out to give a semiquantitative estimate of P. gingivalis. B. forsythus, and T. denticola. The immunologic detection method suggested the presence of antigens of P. gingivalis, B. forsythus, and T. denticola in subjects from each of the 3 groups. When a global analysis for the 3 disease groups was performed at one time, statistically significant differences were found among the ELISA scores of the 3 bacterial species. For example, comparisons of the ELISA scores showed that the concentrations of P. gingivalis differed significantly when comparing TGS to UGS and PS, but not when examining UGS/PS. The ELISA scores for B. forsythus were significantly different between TGS and PS. Mean concentrations of T. denticola were significantly different when comparing PS to TGS or UGS, whereas no difference was found between the latter categories. Within the limited scope of this study, the concentration of antigens detectable from putative periodontopathogens like P. gingivalis, B. forsythus, and T. denticola differed among the 3 diseased groups, with periodontitis subjects often showing the greatest level of antigens. Thus, it is reasonable to expect that, when using sensitive immunological detection methods, antigens of suspected periodontal pathogens can be found irrespective of the individual's clinical status. However, while detectable in the periodontal sites, the concentrations of these microorganisms are most likely to be above the threshold necessary to induce clinically-significant disease. Studies with larger sample size and standardized antigens are necessary to determine if the groups we found not to differ, were, in fact, different.