Microbial etiological agents of destructive periodontal diseases

Shared antigens of Porphyromonas gingivalis and Bacteroides forsythus

Periodontitis in humans is caused by a group of predominantly gram-negative, anaerobic bacteria among which Porphyromonas gingivalis and Bacteroides forsythus are prominent. A similar group is present and presumably plays a similar role in experimental periodontitis in the primate Macaca fascicularis. Nevertheless, immunization using a vaccine containing only killed P. gingivalis suppresses the progress of experimental periodontitis in M. fascicularis. We investigated the hypothesis that gram-negative periodontopathic bacterial may share antigens, and immunization with one species may induce antibodies reactive with other gram-negative species. Using enzyme-linked immunosorbent assay (ELISA), Western and dot immunoblots with nonabsorbed and absorbed and immune and preimmune sera we show that monkeys immunized with P. gingivalis produce antibodies reactive not only with antigens of P. gingivalis but also with those of B. forsythus. Similarly, rabbits immunized with P. gingivalis or with B. forsythus produce antibodies that react with antigens of both bacteria. Cross-reactive antibodies bind to epitopes in lipid A and possibly in core carbohydrate of lipopolysaccharide. Using complexes of lipopolysaccharide with polymyxin B, bovine serum albumin and apolipoprotein A1 specificity of binding was documented. Using sera from monkeys immunized with P. gingivalis, cross-reactivity with Actinobacillus actinomycetemcomitans could not be demonstrated by ELI-SA, although binding to lipopolysaccharide but not to lipid A was demonstrated by Western and dot immunoblots. Antibodies to shared lipopolysaccharide epitopes of periodontopathic bacteria may account, at least in part, for the immune protection observed in immunized monkeys, and shared epitopes may have potential as a vaccine for periodontitis in humans.

Cytokine-inducing components of periodontopathogenic bacteria

Pro-inflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8 and tumour necrosis factor (TNF) are believed to be the major pathological mediators of inflammatory diseases ranging from arthritis to the periodontal diseases. The stimuli inducing proinflammatory cytokine induction in the former disease is unclear but in the periodontal diseases it is obvious that the stimulus is the accumulation of bacteria in the subgingival region. As these bacteria do not invade the lesional tissues in large numbers, it is believed that their soluble components or products interact with host tissues to induce cytokine gene transcription. The paradigm is that lipopolysaccharide is the key bacterial component inducing pro-inflammatory cytokine gene expression. However, over the past decade a growing number of reports on non-oral bacteria have established that many other bacterial components, as well as secretory products, have the capacity to induce cytokine synthesis. Some of these, such as the protein pneumolysin from Streptococcus pneumoniae, are incredibly potent (in this case inducing cytokine synthesis at femtomolar concentrations). This review surveys the range of bacterial components and products which have been shown to stimulate cytokine synthesis with particular emphasis on the hypothesis that these components play a role in the pathology of the periodontal diseases.

Potential of diagnostic microbiology for treatment and prognosis of dental caries and periodontal diseases

Most evidence suggests that only a finite number of bacteria are responsible for dental caries and periodontal diseases. This knowledge led to the development of microbial tests which can identify suspected pathogens. Current evaluation of the diagnostic power of microbial tests has shown that they have a low sensitivity and a low prognostic value. Despite these shortcomings, there are valid indications for microbiological-based diagnosis. Salivary microbial tests for the detection of mutans streptococci and lactobacilli may be useful, for example, in young children, oligosialic patients, and orthodontic patients. These tests can be used to monitor the success of chemopreventive measures or compliance with dietary recommendations. Microbial diagnosis, may also be valuable in the treatment of early-onset periodontitis or in subjects who respond poorly to periodontal therapy. The use of microbial tests to monitor the efficacy of chemotherapy or mechanical treatment is of particular interest.

Source of suspected periodontal pathogens re-emerging after periodontal treatment

To clarify the source of re-emerging periodontal pathogens after treatment, we compared the ribotypes of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia/Prevotella nigrescens group and Campylobacter rectus before and after treatment in 7 periodontitis patients and in 6 of the spouses. The patients harbored A. actinomycetemcomitans, P. gingivalis, P. intermedia/P. nigrescens group or C. rectus in their subgingival or salivary samples before treatment. The respective bacterial species were not detected 1 month after treatment, but reappeared by 6 months later. When available, 4 random colonies of each of the 4 species were isolated from both subgingival and salivary samples at each sampling occasion, the isolates were subcultured, identified and typed applying pheno- and genotypic intraspecies characterization methods. Altogether 90 strains of A. actinomycetemcomitans, P. gingivalis, P. intermedia/P. nigrescens group and C. rectus were available from 2, 3, 2 and 4 patients, respectively. The pre- and post-treatment ribotypes of A. actinomycetemcomitans-, P. gingivalis- and P. intermedia/P. nigrescens group-isolates were identical in all respective patients. The pre- and post-treatment ribotypes of C. rectus were identical in 1 of 4 patients, whereas 2 patients harbored a previously not detected post-treatment ribotype and 1 patient harbored the initial and a previously not detected post-treatment ribotype. To study the possibility that periodontitis patients may acquire strains from the spouse after treatment, isolates of A. actinomycetemcomitans, P. gingivalis, P. intermedia/P. nigrescens group and C. rectus (n = 95) from the patients' spouses were ribotyped and compared with those of the patients. The patient exhibited his own post-treatment ribotypes, different from those of the spouse, of A. actinomycetemcomitans and P. gingivalis in 1 couple and of P. intermedia/P. nigrescens group and C. rectus in 1 couple. In the 2 patients who harbored a previously not detected post-treatment ribotype of C. rectus, one patient shared the new ribotype with the spouse, whereas the other one did not. Although an exogenous source cannot be fully ruled out, the patient's own oral flora seems to be the main source of re-emerging periodontal pathogens after treatment.

Treatment of periodontal disease based on microbiological diagnosis. Relation between microbiological and clinical parameters during 5 years

The purpose of this study was to assess the clinical effect of treatment aimed to suppress Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis below detection level and Prevotella intermedia below 5% of the cultivable periodontal pocket flora. Sixteen patients and a total of 111 periodontal pockets with probing depth > or = 6 mm were included in the study. Twelve patients and a total of 77 sites completed the 5-year study. The results demonstrated clinical improvement of probing depth and gain of clinical attachment level of 3.4 mm and 1.2 mm, respectively. Treatment to eliminate indicator bacteria continued for 3 years before the aim was fulfilled. In order to eliminate A. actinomycetemcomitans from a majority of the sites, a combination of surgery and generalized tetracycline treatment was performed. A recolonization or regrowth of the indicator bacteria exceeding detection levels took place in several sites. The presence of A. actinomycetemcomitans. P. gingivalis, and P. intermedia, alone or in combination, correlated with attachment level change on the individual level. No such correlation was obtained by using presence of plaque, bleeding on probing, or three other bacteria (Campylobacter rectus, Eikenella corrodens, and Fusobacterium nucleatum) not used as treatment goal markers.

Utility of 5 major putative periodontal pathogens and selected clinical parameters to predict periodontal breakdown in patients on maintenance care

The predictive utility of 5 major putative periodontopathic microbial species, "superinfecting" organisms, and several clinical periodontal parameters were assessed relative to periodontitis recurrence over a 12-month period in 78 treated adult patients participating in a 3-month maintenance care program. At baseline, pooled subgingival microbial samples were collected from each patient, and whole-mouth evaluations of probing depth, relative periodontal attachment level, furcation involvement, and indices of plaque and gingival inflammation were carried out. 67 (85.9%) subjects were culture-positive at baseline for presence of either Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Campylobacter rectus or Peptostreptococcus micros, with 48 (61.5%) subjects yielding one or more of these species at or above designated threshold proportions of > or = 0.01% for A. actinomycetemcomitans, > or = 0.1% for P. gingivalis, > or = 2.5% for P. intermedia, > or = 2.0% for C. rectus, and > or = 3.0% for P. micros. Subgingival yeasts were recovered from 12 subjects, staphylococci from 7, and enteric rods/pseudomonads from 6; however, no subjects revealed > or = 1.0% baseline proportions of these "superinfecting" organisms in subgingival specimens. Periodontitis recurrence in subjects was defined as any periodontal site exhibiting either a probing depth increase of > or = 3 mm from baseline, or a probing depth increase of > or = 2 mm from baseline together with a loss in relative periodontal attachment of > or = 2 mm from baseline. 15 (19.2%) study subjects showed periodontitis recurrence within 6 months of baseline, and 25 (32.1%) within 12 months. The mere baseline presence of the 5 major test species and "superinfecting" organisms were not significant predictors of periodontitis recurrence over 12 months. However, a 2.5 relative risk for periodontitis recurrence over 12 months was found for subjects yielding one or more of the 5 major test species at or above the designated baseline threshold proportions (p = 0.022, Mantel-Haenszel chi 2 test). The positive predictive value for periodontitis recurrence of a microbiologic analysis encompassing the 5 major test species at or above the designated threshold proportions improved with increasing time from baseline, up to approximately 42% at 12 months. Baseline variables jointly providing in multiple regression analysis the best predictive capability for periodontitis recurrence in subjects over a 12-month period were recovery of one or more of the 5 major test species at or above designated threshold proportions, the proportion of sites per subject with > or = 5 mm probing depth, and the mean whole-mouth probing depth. These findings indicate that one or more of 5 major putative periodontal pathogens in elevated subgingival proportions together with increased probing depth predispose adults on maintenance care to recurrent periodontitis.

Degradation of host protease inhibitors and activation of plasminogen by proteolytic enzymes from Porphyromonas gingivalis and Treponema denticola

Bacterial proteases may participate in the pathogenesis of periodontal diseases through their action on host proteins. In the present study, the ability of selected periodontopathogens, as well as two proteases isolated from Porphyromonas gingivalis and Treponema denticola, to degrade host protease inhibitors was evaluated. The activation of human plasminogen by the two bacterial proteases was also investigated. Proteolytic breakdown of host protease inhibitors (alpha-1-antitrypsin, antichymotrypsin, alpha 2-macroglobulin, antithrombin III, antiplasmin and cystatin C) was evaluated by SDS-PAGE. The 80 kDa trypsin-like protease of P. gingivalis completely digested the six protease inhibitors under investigation, whereas the 95 kDa chymotrypsin-like protease of T. denticola was slightly less active, more particularly on alpha 2-macroglobulin and cystatin C. When whole cells from a number of oral bacterial species were tested, the most significant degradation was obtained with P. gingivalis, T. denticola, Prevotella intermedia, Prevotella nigrescens and Capnocytophaga spp. Peptostreptococcus micros and Propionibacterium acnes had only some degradative activity on selected inhibitors, whereas three bacterial species, Actinobacillus actinomycetemcomitans, Bacteroides forsythus and Fusobacterium nucleatum, had no effect on the protease inhibitors. The 80 kDa protease of P. gingivalis demonstrated strong plasminogen activation, whereas no such activity was associated with the 95 kDa protease of T. denticola. This study indicates the high potential of some periodontal pathogens to destroy protease inhibitors and activate plasminogen. This may result in an uncontrolled degradation of periodontal tissues and a rapid progression of the disease.

Local and systemic chemotherapy in the management of periodontal disease: an opinion and review of the concept

Periodontal disease appears to arise from the interaction of pathogenic bacteria with a susceptible host. The main aims of disease management have been to establish a high standard of oral hygiene and to professionally and thoroughly debride the root surface Chemical agents could be considered for both aspects of management. Chemoprevention using supragingivally delivered agents such as chlorhexidine may be questioned for value in the pre-treatment hygiene phase but have well-established efficacy immediately preoperatively and during the post-operative weeks. Long-term maintenance use of chlorhexidine is problematic due to local side effects. Antiplaque toothpastes show modest benefits to gingivitis but are not proven to prevent recurrence of periodontitis. Chemotherapy may be directed at subgingival plaque, using antimicrobials, or at the host response using anti-inflammatory agents. Antimicrobials can be locally or systemically delivered. In most cases antimicrobial chemotherapy should be considered adjunctive to mechanical debridement. The advantages of local and systemic chemotherapy must be balanced against the disadvantages and potential side effects of agents. Antimicrobial chemotherapy offers little or no benefit to the treatment of most chronic adult periodontitis patients and should be reserved for the more rapid or refractory types of disease, and after the debridement phase. Despite the large number of studies there are insufficient comparative data to support any one local delivery system or systemic regimen as superior to another. Systemic versus local antimicrobials have not been compared to date. Host response modifying drugs such as non-steriodal anti-inflammatory drugs (NSAIDS) offer the potential to reduce breakdown and promote healing, including bone regeneration. However until more data are available, NSAIDs should not be used in the management of chronic periodontal diseases, there being no specific agent(s) or regimen established for use. Chemotherapy has an important place in the management of chronic periodontal diseases but routine use must be considered as an over prescription of these valuable agents.

Characteristics of systemic antibody responses of nonhuman primates following active immunization with Porphyromonas gingivalis, Prevotella intermedia and Bacteroides fragilis

Periodontal disease is an infectious disease manifested by the progressive change of a healthy resident commensal microbiota to a pathogenic one characterized by a specific microbiota. Thus, the prospect for the use of selected bacteria or their antigens as a vaccine to interfere with the microbial changes and resulting progression of periodontal tissue destruction has been proposed. As a first step in examining the use of bacterial antigens as immunogens in periodontitis, this study characterized the humoral immune response in Macaca fascicularis after systemic immunization with intact Porphyromonas gingivalis, Prevotella intermedia and Bacteroides fragilis. Parental immunization of the nonhuman primate with the intact bacteria resulted in the production of specific and significantly elevated levels of antibodies to P. gingivalis and P. intermedia, with the predominant isotype being immunoglobulin G (IgG). In contrast, the principal response to the nonoral, intestinal bacterium, B. fragilis, was of the IgM isotype. Immunization increased IgG, IgM, and IgA antibody by 14-227 fold to P. gingivalis and 8-108 fold to P. intermedia. The level of serum IgA antibody increased (77-227 fold). The kinetics of the antibody response post-immunization and post-ligation differed with respect to each of the bacteria tested. IgG antibody to P. gingivalis increased through week 16 of the experiment and remained elevated above baseline through week 32. The IgG antibody level to P. intermedia peaked at 4 weeks following the third immunization and decreased post-ligation to near baseline levels by week 16. Characterization of the immune response after active immunization in the nonhuman primate has demonstrated a substantial and specific increase in antibody response which was sustained for several weeks. The insights obtained from these studies should help optimize the potential for immunologic interference with progressing periodontitis.

Efficacy of systemically administered acetylsalicylic acid plus scaling on periodontal health and elastase-alpha 1-proteinase inhibitor in gingival crevicular fluid

The purpose of this proof of principle trial was to assess whether conventional periodontal therapy and systemically administrated acetylsalicylic acid (ASA) are functionally synergistic when combined in the treatment of periodontitis. A total of 30 patients with untreated moderate to severe adult periodontitis were enrolled into the study and were given placebo q.i.d. between the baseline and 6-week examination, and acetylsalicylic acid (ASA) 500 mg q.i.d. between the 6-week and 12-week examinations. In addition, they received supra- and subgingival scaling in 1 quadrant after baseline examination and in 2 further randomly selected quadrants after the 6-week examination. The study design resulted in the following 4 therapies: (1) scaling plus ASA 500 mg q.i.d.; (2) scaling plus placebo q.i.d.; (3) ASA 500 mg q.i.d. alone; (4) placebo q.i.d. alone. Two-way analysis of variance showed functional synergism of ASA and scaling, resulting in a therapeutic efficacy approximately equivalent to the sum of each individual therapeutic efficacy (i.e., ASA alone and scaling alone) in reducing gingival inflammation and pocket probing depth over the 6-week observation period (interaction: p > 0.05). Only the effect of ASA was significant in reducing the concentration of elastase-alpha 1-proteinase inhibitor in gingival crevicular fluid (GCF E-alpha 1-PI) (p < 0.001), reduction in GCF E-alpha 1-PI concentrations by ASA may indicate a decreased risk in periodontal disease progression. The results suggest that the combination of therapies and their different mechanisms of action, i.e., reduction of bacterial plaque and inhibition of destructive components of the immune responses, may result in functionally synergistic therapeutic efficacies in patients with untreated adult periodontitis.

Host response assessment in recurring periodontitis

Data derived from periodontitis patients have provided support for a relationship between the distribution of selected members of the periodontopathic microbiota and antibody levels to the intact bacteria in both serum and GCF. These data are consistent with the systemic antibody as a reflection of the host response to an infectious process associated with an episode of disease activity. The purpose of this report is to address the concept that the host antibody responses may help to elucidate the specific etiologic agents and be used to model the risk for future periodontal disease progression in recurring periodontitis. These findings from one study in adult periodontitis patients indicated that elevations in certain antibody specificities are most closely associated with patients exhibiting a risk of disease recurrence. Furthermore, analysis of the frequency of antibody elevations suggested that patients capable of maintaining elevated antibody to these pathogens post-treatment, may be indicative of an individual at less risk. A 2nd investigation was implemented to address questions concerning host-parasite interactions in A. actinomycetemcomitans-associated recurring periodontitis. The results showed distinctive characteristics of local and systemic antibody responses and A. actinomycetemcomitans infection in patients with varying extents of recurrent disease. These longitudinal studies developed evidence for the potential of local and/or systemic antibody responses as indicators of periodontal disease recurrence.

Virulence factors of Actinobacillus actinomycetemcomitans relevant to the pathogenesis of inflammatory periodontal diseases

There is strong evidence implicating Actinobacillus actinomycetemcomitans as the causative agent of localised juvenile periodontitis (LJP), a disease characterised by rapid destruction of the tooth-supporting tissues. This organism possesses a large number of virulence factors with a wide range of activities which enable it to colonise the oral cavity, invade periodontal tissues, evade host defences, initiate connective tissue destruction and interfere with tissue repair. Adhesion to epithelial and tooth surfaces is dependent on the presence of surface proteins and structures such as microvesicles and fimbriae. Invasion has been demonstrated in vivo and in vitro although the mechanisms involved are poorly understood. The organism has a number of means of evading host defences which include: (i) inhibiting poloymorphonuclear leukocyte (PMN) chemotaxis; (ii) killing PMNs and monocytes; (iii) producing immunosuppressive factors; (iv) secreting proteases capable of cleaving IgG; and (v) producing Fc-binding proteins. Surface components of A. actinomycetemcomitans are potent stimulators of bone resorption and can induce the release of a range of cytokines which can initiate tissue destruction. A number of surface components can also inhibit the proliferation of fibroblasts and their production of components of the extracellular matrix. Little is known, however, regarding the way in which these factors operate in vivo to produce the pathological features of the disease.

Cell envelope and cell wall immunization of Macaca fascicularis: effect on the progression of ligature-induced periodontitis

The nonhuman primate, Macaca fascicularis, was used to study the role of immunization with selected members of the periodontopathic microbiota in the longitudinal progression of ligature-induced periodontitis. Animals were immunized with cell envelope antigens prepared from Porphyromonas gingivalis and Prevotella intermedia, and a mixture prepared from Fusobacterium nucleatum, Campylobacter rectus, and Actinomyces viscosus. Serum immunoglobulin G (IgG), IgM and IgA isotype antibodies increased significantly in all immunization groups and were specific for each of the immunogens. P. gingivalis and P. intermedia immunization resulted in a stabilization of the proportions of these species throughout most of the experiment. The high P. gingivalis antibody titer resulted in low P. gingivalis numbers being recovered. P. gingivalis immunization, while lowering recoverable viable P. gingivalis, resulted in significantly increased levels of Prevotella loescheii, Prevotella buccae, Bacteroides macacae and Prevotella melaninogenica compared with preligation and preimmunization levels. Actinobacillus actinomycetemcomitans, Capnocytophaga spp. and Eikenella spp. remained at preligation levels postimmunization. Campylobacter spp. increased significantly during the course of the experiment in all groups, whereas the levels of Fusobacterium spp. decreased. Plaque indices and bleeding on probing showed significant increases in all groups following ligation, with the placebo group showing the greatest increase. Pocket depth measurements revealed that , whereas the placebo animals showed an approximate 5% increase, the P. gingivalis- and P. intermedia-immunized groups showed nearly a 20% increase in pocket depth. Attachment level measurements showed significantly greater attachment loss in the P. gingivalis- and P. intermedia-immunized groups, and the F. nucleatum + C. rectus + A. viscosus immunization appeared to prevent significant changes in pocket depth/attachment level loss. Radiographic measurement of bone loss by computer-assisted densitometric image analysis revealed that the placebo group lost bone throughout the experiment. P. gingivalis- and P. intermedia-immunized groups showed an exacerbated loss of bone density and the group immunized with F. nucleatum + C. rectus + A. viscosus exhibited significantly lower amounts of bone loss when analyzed by computer-assisted densitometric image analysis, compared with the other immunized groups. Although immunization with P. gingivalis and P. intermedia cell envelope antigens had an effect on their emergence in the complex microbiota of the developing periodontal pocket, this immunization also resulted in greater bone loss than immunization with F. nucleatum + C. rectus + A. viscosus, suggesting that, whereas selective members of the putative periodontopathic microbiota may play a direct role in periodontal tissue destruction, the complexity of the subgingival microbiota dictates that considerable scrutiny is required to select useful immunogens that can elicit functional protection from periodontal tissue destruction induced by oral microorganisms that already colonize or infect the host.

Colorimetric microtiter plate based assay for detection and quantification of amplified Actinobacillus actinomycetemcomitans DNA

We developed a colorimetric microtiter plate-based assay for the detection and quantification of polymerase chain reaction-amplified DNA fragment specific for Actinobacillus actinomycetemcomitans. We amplified the 396-bp leukotoxin-specific DNA fragment by using two oligonucleotide primers, one carrying a biotin group at the 5' end and another one with a digoxigenin at the 5' end. Following amplification, the biotinylated polymerase chain reaction products were applied to a microtiter well precoated with avidin. The colorimetric detection and quantification were achieved by an enzyme-linked immunosorbent assay using alkaline phosphatase-conjugated anti-digoxigenin antibody. The detection limit of the colorimetric assay was found to be as little as 500 fg of purified A. actinomycetemcomitans DNA and as few as 50 A. actinomycetemcomitans. Therefore, this colorimetric assay was able to estimate the amount of A. actinomycetemcomitans in subgingival plaque samples. We concluded that the colorimetric assay of the PCR product is a very useful method not only to detect the presence of A. actinomycetemcomitans but also to quantify the amount of A. actinomycetemcomitans in large numbers of subgingival plaque samples.

Intergeneric coaggregation of oral Treponema spp. with Fusobacterium spp. and intrageneric coaggregation among Fusobacterium spp

A total of 22 strains of Treponema spp. including members of all four named human oral species were tested for coaggregation with 7 strains of oral fusobacteria, 2 strains of nonoral fusobacteria, and 45 strains of other oral bacteria, which included actinobacilli, actinomyces, capnocytophagae, eubacteria, porphyromonads, prevotellae, selenomonads, streptococci, and veillonellae. None of the treponemes coaggregated with any of the latter 45 oral strains or with the two nonoral fusobacteria. All treponemes, eight Treponema denticola strains, eight T. socranskii strains, four oral pectinolytic treponemes, one T. pectinovorum strain, and one T. vincentii strain coaggregated with at least one strain of the fusobacteria tested as partners. The partners consisted of one strain of Fusobacterium periodonticum, five F. nucleatum strains including all four subspecies of F. nucleatum, and a strain of F. simiae obtained from the dental plaque of a monkey. In the more than 100 coaggregations observed, the fusobacterial partner was heat inactivated (85 degrees C for 30 min), while the treponemes were unaffected by the heat treatment. Furthermore, the fusobacteria were usually inactivated by proteinase K treatment, and the treponemes were not affected. Only the T. denticola coaggregations were inhibited by lactose and D-galactosamine. None were inhibited by any of 23 other different sugars or L-arginine. Intragenic coaggregations were seen among the subspecies of F. nucleatum and with F. periodonticum, and none were inhibited by any of the sugars tested or by L-arginine. No intrageneric coaggregations were observed among the treponemes. These data indicate that the human oral treponemes show a specificity for oral fusobacteria as coaggregation partners. Such cell-to cell contact may facilitate efficient metabolic communication and enhance the proliferation of each cell in the progressively more severe stages of periodontal disease.

Immunomagnetic PCR and DNA probe for detection and identification of Porphyromonas gingivalis

The aim of the study that we describe was to combine an immunomagnetic separation and a PCR followed by dot blot hybridization with a DNA probe for the detection and identification of Porphyromonas gingivalis. Immunomagnetic particles were coated with monoclonal antibody specific for P. gingivalis and were incubated with a suspension containing seven oral bacterial species spiked with various dilutions of P. gingivalis. Beads with their load of bound bacterial were boiled in water, and the target DNA in the supernatant was amplified with a primer pair to generate a 593-bp PCR fragment specific for P. gingivalis. Finally, the product of amplification was detected by dot blot hybridization with a digoxigenin-labeled 593-bp probe. The detection limit was determined to be 100 bacterial cells per ml. The immunomagnetic-PCR/DNA probe procedure described here should be useful for the rapid, specific, and sensitive detection and identification of P. gingivalis in clinical samples.

Molecular genetic detection of Bacteroides heparinolyticus in adult periodontitis

Bacteroides heparinolyticus in subgingival plaque was identified using a digoxigenin-labeled whole genomic DNA probe and a polymerase chain reaction (PCR) assay based on 16S rRNA species-specific primers (5'-ATG GTG ATT CCG CAT GGT TTC TCC-3' (base position, 188-212) and 5'-CAA ACT TTC ACA GCT GAC TTA AGC-3' (592-615)). Subgingival specimens obtained by paper points from 3 deep periodontal pockets in each of 113 adults were examined. The DNA probe reacted with all pure isolates tested of B. heparinolyticus and did not react with other oral species tested; the probe showed positive reactions in 74.3% of the patient samples examined. The PCR primers produced the 428 bp species specific amplification product in all B. heparinolyticus test strains and did not reveal detectable amplicons with strains of other subgingival species. The PCR method detected 50 B. heparinolyticus cells dispersed in subgingival plaque. PCR only revealed B. heparinolyticus in 6.2% of the patient samples studied. The higher level of positive specimens with the DNA probe was probably due to false-positive reactions from cross-hybridization with unknown subgingival species. This study suggests that the PCR method amplifying specific 16S rRNA sequences represents an easy and valuable means to detect B. heparinolyticus in subgingival plaque. The low prevalence of subgingival B. heparinolyticus does not incriminate the organism in the etiology of adult periodontitis.

Longitudinal dynamics of infection and serum antibody in A. actinomycetemcomitans periodontitis

OBJECTS

This report describes one of the first prospective studies delineating the relationship between infection, host antibody responses and disease exacerbations and remissions in a distinct subset of periodontitis patients infected with A. actinomycetemcomitans.

DESIGN

The design of this longitudinal study included visits for each patient approximately every 2 months for up to 3 years.

SUBJECTS AND METHODS

Subjects (n=51) included 16 adult periodontitis (AP) and 11 early-onset periodontitis (EOP) patients with elevated serum IgG antibody to A. actinomycetemcomitans and infection with this microorganism, 12 AP patients with normal levels of anti-Aa antibody, and 12 normal subjects. MEASUREMENT OUTCOMES: Clinical parameters included a gingival index, plaque index, bleeding on probing, pocket depth, and attachment level. Disease activity was defined as loss of attachment during the monitoring intervals. Serum IgG, IgM and IgA antibody to A. actinomycetemcomitans Y4 (serotype b) was quantitated using an ELISA. Subgingival plaque samples were examined for A. actinomycetemcomitans using colony immunoblotting. Human serum IgG antibody specificities to outer membrane antigens (OMA) of A. actinomycetemcomitans Y4 were determined using Western immunoblotting.

RESULTS

A. actinomycetemcomitans-infected AP patients had a higher frequency of teeth infected when compared to the EOP patients. However, the EOP patients exhibited a trend for higher levels of A. actinomycetemcomitans in those teeth that were infected. Active disease patients demonstrated a significantly greater frequency of infected sites, as well as significant elevations in the proportions of A. actinomycetemcomitans. Both EOP and AP groups showed significantly elevated IgG, IgM and IgA antibody to A. actinomycetemcomitans when compared to a periodontally normal group. The level of IgG antibody was significantly elevated in A. actinomycetemcomitans-positive patients with active disease, while IgA antibody was decreased in a number of the active group patients. Plaque samples derived from active sites showed a clear and significant increase in A. actinomycetemcomitans that occurred from 2-6 months prior to the identification of disease activity. Approximately 70% of the active disease patients showed an increase in IgG antibody level by 2-4 months prior to disease activity. Studies of the antigen reactivity patterns of serum IgG indicated that antibody to antigens of 65, 58, 48, 29 and 24 kDa were more frequent in patients who showed active disease, while those patients with the greatest frequency of active disease appeared to show a general decrease in the recognition of the A. actinomycetemcomitans OMA.

CONCLUSIONS

It appears that A. actinomycetemcomitans infection relates to a particular type of disease with accompanying antibody responses that reflect periods of active disease. The dynamics of A. actinomycetemcomitans infection and the level and specificity of systemic antibody responses to this pathogen support an important contribution of the immune response to managing this infection.

Functional properties of nonhuman primate antibody to Porphyromonas gingivalis

The nonhuman primate (NHP) serves as a useful model for examining the host-parasite interactions in Porphyromonas gingivalis-associated periodontal disease. This study determined the influence of NHP sera on (i) the direct killing of P. gingivalis, (ii) P. gingivalis-induced superoxide anion (O2-) release from human polymorphonuclear leukocytes (PMNs), and (iii) the ability of PMNs to bind and phagocytize P. gingivalis. Three types of NHP sera were utilized: (i) normal or baseline sera; (ii) sera obtained after ligature-induced periodontitis; and (iii) sera obtained following active immunization with formalinized P. gingivalis. All assays were performed with or without the addition of human complement. Significantly more (P < 0.01) direct killing of P. gingivalis occurred with immunized sera and complement than with any of the other treatments. The sera from ligature-induced periodontitis NHPs had significantly less (P < 0.03) killing capacity than the baseline sera, which contained natural antibody produced to P. gingivalis colonization. Sera from immunized NHPs were used to opsonize P. gingivalis and caused significantly greater (P < 0.01) levels of O2- release from PMNs. Finally, the sera from immunized NHPs significantly enhanced (P < 0.009) the uptake of P. gingivalis by PMNs, although binding of the bacteria to PMNs was similar among all three serum types. Active immunization of NHPs with P. gingivalis elicited a functional antibody that enhanced direct killing, positively influenced the activation of PMNs, and enhanced the ability of PMNs to phagocytize P. gingivalis. Moreover, antibody produced as a sequela of progressing periodontitis appeared to lack these functions. A wide variability in functional capacity of the sera from individual NHPs, which may contribute to an individual's susceptibility to P. gingivalis-induced disease, was noted. This variability suggested that results from functional tests of serum antibody may aid in predicting host susceptibility to disease and response to therapy.

Comparative virulence of periodontopathogens in a mouse abscess model

OBJECTIVE(S)

This report compares the virulence of selected strains of P. gingivalis, A. actinomycetemcomitans, C. rectus, F. nucleatum and T. denticola in a murine model as a measure of pathogenic potential of these oral microorganisms. The characteristics of the tissue destruction associated with these monoinfections were then related to a potential model for bacterial synergism in progressing periodontitis.

DESIGN AND METHODS

All bacterial strains were grown to mid-logarithmic to early stationary growth phase, harvested and used at various doses to challenge BALB/c normal and BALB/c dexamethasone (DEX) treated mice to mimic a neutrophil dysfunction. The characteristics of tissue destruction, and overt tissue destructive capacity of these species were examined as a function of challenge dose and time.

OUTCOME MEASURES

The mice were examined for an interval of approximately 15 days post-challenge and the presence/absence of lesions, localized or generalized nature of the lesion (including size in mm2), and lethality of the infection were assessed.

RESULTS

Comparison of the virulence of the various P. gingivalis strains related to lethality and lesion size associated with destruction of the connective tissue, indicated a virulence capacity of P. gingivalis strains 53977>W50 = T22>3079>33277>381. C. rectus elicited localized necrotic lesions which were limited to the epithelial layers of the skin. The size of the lesions also indicated a graded difference in virulence, such that C. rectus strains 234>576>>33238. A. actinomycetemcomitans caused the formation of classic localized abscesses with a PMN infiltrate and inflammatory exudates. Although each of the A. actinomycetemcomitans strains exhibited a similar virulence pattern in this murine model, A. actinomycetemcomitans serotype b representative strains were potentially more pathogenic with a virulence capacity of 3113D-N = 3975A>JP2 > or = Y4>29523>33384. Both C. rectus and A. actinomycetemcomitans strains showed clear evidence that recent clinical isolates were more virulent than laboratory strains. Challenge with F. nucleatum resulted in tissue destructive responses which were different from those observed with the other strains used in this study. A rapid onset of dose-dependent lesion development, related to the formation of either closed abscesses or open lesions, was observed with F. nucleatum. Tissue involvement was also greater at lower F. nucleatum doses when compared to the other bacteria. F. nucleatum challenge of DEX-treated mice resulted in a shift to open lesions. T. denticola appeared to be more tissue invasive than the other species examined in this study. Challenge of mice with T. denticola resulted in involvement of multiple tissues, including epithelial and connective tissues, as well as appearing to invade muscle layers and deeper tissues. In addition to invading deeper tissues, the resulting lesions took considerably longer to resolve. In the DEX-treated mice (neutrophil depleted), P. gingivalis, C. rectus, and A. actinomycetemcomitans were significantly more virulent. In contrast, while DEX treatment altered the characteristics of lesions caused by F. nucleatum, the extent of lesions produced by F. nucleatum and T. denticola was not substantially enhanced.

CONCLUSIONS

The results obtained from this study suggest that different microorganisms have the ability to provide individual pathologies which may act in an additive/synergistic fashion contributing to the tissue destruction noted in periodontitis.

Factors associated with different responses to periodontal therapy

In a study of the efficacy of modified Widman flap surgery and scaling and root planning accompanied by 1 of 4 systemic adjunctive agents, Augmentin, tetracycline, ibuprofen or placebo, it was observed that subjects differed in their response to therapy. The difference was only partially accounted for by the adjunctive agent employed. The purpose of the present investigation was to examine clinical and microbiological features in subjects who showed different levels of attachment change post-therapy. 40 subjects were subset into 3 groups based on mean attachment level change post-therapy. 10 poor response subjects showed mean attachment loss; 19 moderate response subjects showed mean attachment gain between 0.02-0.5 mm and 11 good response subjects showed a mean gain of attachment > 0.5 mm. Clinical parameters were measured at 6 sites per tooth both pre- and post-therapy. Microbiological samples were taken from the mesial aspect of each tooth and evaluated individually for their content of 14 subgingival taxa using a colony lift method and DNA probes. % of sites colonized by each species was computed for each subject both pre- and post-therapy. Significant differences were observed among treatment response groups for mean probing pocket depth, attachment level and % of sites with plaque pre-therapy. The poor response subjects had the lowest mean probing pocket depth and attachment level, but the highest plaque levels. Post-therapy, the poor response group exhibited the greatest degree of gingival inflammation as assessed by gingival redness and bleeding on probing.(ABSTRACT TRUNCATED AT 250 WORDS)

Patterns of antibody response in subjects with periodontitis

Periodontal diseases comprise a heterogeneous group of infections that are difficult to distinguish on a clinical basis alone. The purpose of the present investigation was to group periodontitis subjects according to their elevated serum antibody levels to specific subgingival species. A total of 119 subjects (19-70 years) with evidence of prior periodontal destruction were monitored at 2-month intervals (maximum 8 visits), prior to therapy, using clinical parameters measured at 6 sites per tooth. The probing attachment level was measured twice at each visit, and an increase of > 2.5mm at a site was used to define subjects with progressing disease. Serum samples were obtained from each subject at each visit and the level of antibody determined by enzyme-linked immunosorbent assay to 12 subgingival species. Subgingival plaque samples were taken from the mesial aspect of all teeth in each subject at each visit, and the levels of 14 different subgingival species were determined using a colony-lift method and DNA probes. Subjects were grouped by cluster analysis of their elevated antibody levels using a simple matching coefficient. Ninety-two subjects fell into 9 clusters with 100% similarity; 29 subjects in one cluster group exhibited elevated antibody to none of the test species. Seven subjects in a second cluster group showed elevated antibody to Bacteroides forsythus. Subjects in the other 7 clusters showed elevated antibody to Actinobacillus actinomycetemcomitans serotype a only or in combination with B. forsythus, A. actinomycetemcomitans serotype b, Prevotella intermedia or Porphyromonas gingivalis.(ABSTRACT TRUNCATED AT 250 WORDS)

Critical issues in periodontal research

The purpose of this paper is to highlight briefly the major achievements and the remaining critical issues in the areas of epidemiology, microbiology, pathogenesis, diagnosis, and therapy. Periodontitis affects a relatively small proportion of study populations in the United States and other countries. Prevalence may be decreasing, but that remains to be seen. The identity and characteristics of susceptible individuals and groups are not known, and risk indicators for severe disease are only beginning to be identified. A very large number of different microbial species has been implicated in the etiology. It seems unlikely that all of these are essential participants. Essential participants need to be identified and better characterized. Whether putative pathogens are members of the commensal flora or exogenous species that must be transmitted is unclear. The relationship between the presence of a pathogenic flora and disease status is obscure. Pathogenic bacterial species are essential, but insufficient to cause disease. A susceptible host and local environmental factors--for example, elevated iron concentration--may be necessary for disease to occur. Many clonal types may not be virulent, and numbers greater than certain threshold levels appear to be necessary. The pathways by which bone and connective tissues of the periodontium are destroyed are sufficiently understood to permit development of therapies aimed at their modification. Examples are the use of vaccines, topical application of anti-inflammatory drugs, and use of chemically modified tetracyclines.

Saliva-bacterium interactions in oral microbial ecology

Saliva is thought to have a significant impact on the colonization of microorganisms in the oral cavity. Salivary components may participate in this process by one of four general mechanisms: binding to microorganisms to facilitate their clearance from the oral cavity, serving as receptors in oral pellicles for microbial adhesion to host surfaces, inhibiting microbial growth or mediating microbial killing, and serving as microbial nutritional substrates. This article reviews information pertinent to the molecular interaction of salivary components with bacteria (primarily the oral streptococci and Actinomyces) and explores the implications of these interactions for oral bacterial colonization and dental plaque formation. Knowledge of the molecular mechanisms controlling bacterial colonization of the oral cavity may suggest methods to prevent not only dental plaque formation but also serious medical infections that may follow microbial colonization of the oral cavity.