Bacteroides melaninogenicus ss. intermedius invasion of rat gingival tissue

Infective endocarditis: prevention strategy and risk factors in an animal model

INTRODUCTION

Infective endocarditis is a serious infection of the endocardium, especially the heart valves, which is associated with a high mortality rate. It generally occurs in patients with altered and abnormal cardiac architecture combined with exposure to bacteria from trauma and other potentially high-risk activities with transient bacteremia.

Effect of black-pigmented bacteria on the plasminogen-plasmin system in human pulp and osteoblastic cells

OBJECTIVE

To date, there have been relatively few studies addressing the presence and expression of the plasminogen-plasmin system at the site of bacterial infection. The aim of the present study was to investigate the effect of black-pigmented bacteria on the expression of the plasminogen-plasmin system in human pulp and osteoblastic cells.

STUDY DESIGN

The supernatants of Porphyromonas endodontalis, Porphyromonas gingivalis, and Prevotella intermedia were used to evaluate tissue-type plasminogen activator (t-PA) and type 1 plasminogen activator inhibitor (PAI-1) gene expression in human pulp and osteoblastic cells. The levels of mRNA were quantitatively measured by using reverse transcription-polymerase chain reaction.

RESULTS

In this study, black-pigmented bacteria induced not only t-PA but also PAI-1 gene expression in human pulp and osteoblastic cells. In addition, the ratio of t-PA to PAI-1 was higher in human pulp and osteoblastic cells stimulated by black-pigmented bacteria than in untreated cell cultures (P <.05).

CONCLUSIONS

A fine balance exists in the expression of components of the plasminogen-plasmin system, whereby tissue homeostasis is maintained. Black-pigmented bacteria activate the activator-inhibitor system in human pulp and osteoblastic cells through unbalance regulation of t-PA and PAI-1, which might result in an uncontrolled degradation of pulpal and periapical tissues.

Invasion of human oral epithelial cells by Prevotella intermedia

Invasion of oral epithelial cells by pathogenic oral bacteria may represent an important virulence factor in the progression of periodontal disease. Here we report that a clinical isolate of Prevotella intermedia, strain 17, was found to invade a human oral epithelial cell line (KB), whereas P. intermedia 27, another clinical isolate, and P. intermedia 25611, the type strain, were not found to invade the cell line. Invasion was quantified by the recovery of viable bacteria following a standard antibiotic protection assay and observed by electron microscopy. Cytochalasin D, cycloheximide, monodansylcadaverine, and low temperature (4 degreesC) inhibited the internalization of P. intermedia 17. Antibodies raised against P. intermedia type C fimbriae and against whole cells inhibited invasion, but the anti-type-C-fimbria antibody inhibited invasion to a greater extent than the anti-whole-cell antibody. This work provides evidence that at least one strain of P. intermedia can invade an oral epithelial cell line and that the type C fimbriae and a cytoskeletal rearrangement are required for this invasion.

Effects of cytokines and periodontopathic bacteria on the leukocyte function-associated antigen 1/intercellular adhesion molecule 1 pathway in gingival fibroblasts in adult periodontitis

We investigated the effects of inflammatory cytokines and periodontopathic bacteria on expression of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1, and E-selectin (endothelial leukocyte adhesion molecule 1) in cultured human gingival fibroblasts (HGF). Cell surface ICAM-1 was upregulated on HGF under transcriptional control by exposure not only to interleukin-1 beta, tumor necrosis factor alpha, and gamma interferon but also to sonic extracts prepared from Porphyromonas gingivalis and Prevotella intermedia (nigrescens) and lipopolysaccharides from Escherichia coli. However, these stimuli induced only minimal expression of vascular cell adhesion molecule 1 and E-selectin on HGF. Binding assays using HGF and Molt 4, the human T-cell leukemia cell line, showed induced ICAM-1 to be functional, and the increased binding was blocked by a combination of monoclonal antibodies against ICAM-1 and leukocyte function-associated antigen 1. Furthermore, gingival tissues from adult periodontitis patients showed increased mRNA expression of ICAM-1 compared with that in tissues from normal healthy donors. In immunohistological analysis, we also observed in vivo that the expression of ICAM-1 on fibroblasts in adult periodontitis tissues was greater than that in normal gingiva. Thus, the overexpression of ICAM-1 on gingival fibroblasts induced by cytokines and periodontopathic bacteria is speculated to be deeply involved in the accumulation and retention of leukocyte function-associated antigen 1-bearing leukocytes in adult periodontitis lesions.

Porphyromonas gingivalis invades oral epithelial cells in vitro

The aim of the present study was to analyze the adhesive and invasive potential of a number of P. gingivalis strains, in an in vitro system utilizing cultures of human oral epithelial cells (KB cell line, ATCC CCL 17). P. gingivalis strains W50 and FDC 381 (laboratory strains) and OMGS 1738, 1743 and 1439 (clinical isolates) as well as E. coli strain HB 101 (non-adhering, non-invasive control) were used. Adherence was assessed by means of scintillation counting and light microscopy, after incubation of radiolabelled bacteria with epithelial cells. In the invasion assay, monolayers were infected with the P. gingivalis and E. coli strains and further incubated with an antibiotic mixture (metronidazole 0.1 mg/ml and gentamicin 0.5 mg/ml). Invasion was evaluated by (i) assessing presence of bacteria surviving the antibiotic treatment, and (ii) electron microscopy. All P. gingivalis strains adhered to and entered into the oral epithelial cells. After 3 hours of incubation, bacteria were frequently identified intracellularly by means of electron microscopy. The cellular membranes, encapsulating the microorganisms in early stages of the invasive process, appeared later to disintegrate. The presence of coated pits on the epithelial cell surfaces suggested that internalization of P. gingivalis was associated with receptor-mediated endocytosis (RME). Formation of outer membrane vesicles (blebs) by intracellular bacteria indicated that internalized P. gingivalis was able to retain its viability. E. coli strain HB 101 neither adhered to nor invaded epithelial cells.

Cytotoxic and immunostimulatory effects of Bacteroides cell products

The etiologic role of Bacteroides in both periodontal and periapical infections has been well documented, with current interest focusing on the specific pathogenic mechanisms involved. The effects of cell fractions derived from Bacteroides gingivalis (BG), Bacteroides intermedius (BI), and Bacteroides asaccharolyticus (BA) have been studied in vitro through: an assessment of the direct cytotoxic effects on human gingival fibroblasts using a tetrazolium dye reduction assay, an evaluation of murine lymphocyte stimulation and interleukin-1 release, and the induction of human lymphocyte-mediated cytotoxicity. Both BG and BI stimulated interleukin-1 release (P less than 0.001), while BA, a nonoral organism, was not significantly active in this respect. Only BG sonicates were able to induce lymphocyte-mediated cytotoxicity (P less than 0.005). All three Bacteroides species demonstrated direct cytotoxic effects on cultured gingival fibroblasts, and these effects were related to the relative protein content and endotoxin activity of the sonicate preparations for each organism. These data show that BG and BI possess factors which may enhance their virulence through activities not shared with BA.

Spirochetes in early lesions of necrotizing ulcerative gingivitis experimentally induced in beagles

The presence of spirochetes and other bacteria during the induction of necrotizing ulcerative gingivitis (NUG) in beagle dogs was studied by transmission electron microscopy. NUG was induced by application of dental debris from diseased dogs to 4 beagles treated with corticosteroid. Biopsies of interdental papillae were collected during a period of 7 weeks. Spirochetes and other bacteria were observed in enlarged intercellular spaces between non-keratinized epithelial cells. Intracellular bacteria were found with and without surrounding vesicular spaces. The invasive spirochetes were mainly intermediately sized and of flagellar "4-8-4" configuration or higher. Bacterial invasion of the sulcular epithelium occurred before clinical evidence of NUG could be observed. It is concluded that invasion by intermediate spirochetes and other bacteria plays a role in initiating ulcerative gingivitis in beagles.

Influence of granulation tissue, dental calculus and contaminated root cementum on periodontal wound healing. An experimental study in monkeys

The rôle of gingival granulation tissue, dental calculus and contaminated root cementum in marginal periodontal formation of new attachment was studied experimentally after chemical conditioning of the root surfaces of premolars and molars in 8 monkeys. Each treatment procedure was carried out in 4 monkeys. The other 4 monkeys served as controls. A morphometrical method was used to evaluate the results. It was concluded that a significant amount of new attachment including formation of new adhering cementum will result only on chemically-conditioned cementum surfaces. Small amounts of calculus or granulation tissue left in situ do not seem to influence healing, provided the cementum is left intact after chemical cleansing.

Prevalence of black-pigmented bacteroides species in root canal infections

The prevalence of black-pigmented Bacteroides species in the root canals of 72 teeth with apical periodontitis was evaluated. Twenty-two of the canals contained one or more species of black-pigmented Bacteroides. Bacteroides intermedius (14 strains) and Bacteroides endodontalis (5 strains) were most common. Of the species Bacteroides gingivalis, Bacteroides loeschei, and Bacteroides denticola, 2, 3, and 1 strains, respectively, were isolated. The median number of bacterial cells recovered from the root canals containing black-pigmented Bacteroides was 2.8 x 10(5) and from the other canals 3.0 x 10(3). The mean number of strains was 7.9 and 3.3, respectively. Sixteen of the 22 root canals containing black-pigmented Bacteroides species were associated with acute apical abscesses and purulent drainage through the root canal. The other six teeth with black-pigmented Bacteroides were asymptomatic. One additional abscess was present among the 72 cases. This root canal contained Actinomyces israelii and Actinomyces naeslundii.

Bacterial invasion in experimental gingivitis in man

Gingival biopsies of the mesial papilla area of the first molar were obtained from each patient at 0-, 14- and 21-day intervals during plaque formation. The biopsies were fixed, serially sectioned, and Gram-stained. The incidence and distribution of the bacteria-like structures were studied by microscopy. In all the specimens the bacterial nature of Gram-stained material was substantiated. In the epithelium the highest number of bacteria was found at the outer layer of marginal oral epithelium, sulcular epithelium and apical oral epithelium along with a decreasing pattern of penetration progressing deeper into the layers of tissue. For junctional epithelium the situation was just the opposite. Each subject had significantly higher counts at Day 21 than at Day 14 for both epithelium and connective tissue. Also significantly higher counts were found in connective tissue compared with epithelium. The higher bacterial density of intragingival bacteria was associated with the higher gingival and plaque indices. This study suggests that early stages of gingival inflammation may be mediated by invasion of bacteria.

Lack of bacterial invasion in experimental periodontitis

The present study in the beagle dog was performed to analyze whether micro-organisms from a subgingival microbiota could be translocated into or had the potential to invade the pocket epithelium and the gingival connective tissue during a phase of rapid breakdown of the attachment apparatus. An attempt was also made to assess whether tetracycline therapy suppressed the subgingival microbiota and changed the size and quality of the lesions in the gingival tissue. 5 inbred beagle dogs were used. Throughout the period of experimentation, the animals were fed a soft diet permitting gross accumulation of plaque and calculus. No mechanical plaque control measures were performed during the course of the study. On day 0, a 120-day period of periodontal tissue breakdown was initiated at the right mandibular 3rd and 4th premolars by tying cotton floss ligatures around the neck of these teeth. The process of tissue breakdown at the mandibular left 3rd and 4th premolars was started 30 days later. The ligatures were replaced once every 2 weeks during the subsequent 4-month period. On experimental day 120, the first biopsy was performed and gingival tissue sections prepared for light and electron microscopic assessment of a series of histometric characteristics. On day 120, a 30-day period of tetracycline (per os) administration was initiated. Each dog was given a dose of 500 mg tetracycline twice daily. On day 150, the biopsy procedure was repeated in the mandibular left premolar regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Recurrent periodontal disease and bacterial presence in the gingiva

Previous investigations have shown that, in biopsies taken from untreated sites of periodontitis, bacteria were present between the epithelial cells and within the connective tissue. In the present study we have examined Gram-stained sections of diseased gingival sites where the disease had recurred after surgical periodontal treatment. The six subjects chosen for the study were patients who had undergone surgical therapy for the treatment of periodontitis and who, upon subsequent recall visits, showed evidence of at least one site recurrent after treatment as detected by bleeding on probing and increased pocket depth of 5 mm or more. A normal control site from the same patient was chosen, preferably contralaterally, showing positive response to treatment with no signs of disease. Sections were stained with either hematoxylin and eosin for tissue survey or Gram for assessment of bacteria and examined by light microscopy. In many specimens, the bacterial nature of Gram-stained material was substantiated. Preliminary results showed a significantly increased number of bacteria in the refractory sites when compared with control sites which responded positively to treatment. The results of this investigation provided further evidence that bacterial presence inside the periodontal tissue may be an important pathogenic factor in periodontal disease.

Inhibition of gingival fibroblast growth by Bacteroides gingivalis

Human gingival fibroblasts were exposed in culture to cell extracts of different black-pigmented Bacteroides species, and their growth was monitored by determining thymidine uptake and counting cells. Of the Bacteroides species tested (B. gingivalis, B. asaccharolyticus, and B. intermedius), B. gingivalis gave the extract with the strongest inhibitory effect on fibroblast thymidine uptake. Linear inhibition reaching 80% of the control level was obtained with a dose of 100 micrograms of B. gingivalis extract protein per ml. The effect of B. asaccharolyticus resembled that of B. gingivalis, but even at the highest dose tested B. intermedius had only a slight inhibitory effect. When fibroblasts were counted after 2- and 4-day exposures to B. gingivalis extracts, a clear depression in the number of fibroblasts was found. The effects of extracts obtained from early and late growth phases of B. gingivalis cultures were similar. A fraction of B. gingivalis consisting essentially of lipopolysaccharides (LPSs) was obtained by degrading the extract proteins with proteinase K. Silver staining of polyacrylamide gels revealed a LPS pattern with a molecular mass ranging from 37 to 60 kilodaltons. This LPS-rich fraction caused inhibition of thymidine uptake by gingival fibroblasts similar to that caused by the native extract alone. Thus, the inhibition of gingival fibroblast growth by B. gingivalis appeared to be LPS mediated. This inhibitory effect of B. gingivalis on oral fibroblast growth may be a virulence factor of this bacterium.

Clinical and microbiological effects of sustained release chlorhexidine in periodontal pockets

Previous studies have shown that a 3-day exposure of the pocket flora to the sustained release of chlorhexidine significantly reduced the relative numbers of spirochetes and motile rods in periodontal pockets to negligible amounts. By 14 days post-treatment, their numbers had returned to pre-treatment levels. The present study extended the exposure time of the pocket flora to the sustained release of chlorhexidine in an attempt to prolong the suppression of the microbial flora for a clinically significant period of time. Clinical parameters were also studied. Sustained release devices (SRD) were inserted into 13 pockets from 8 patients. Pocket depth ranged between 5 and 8 mm. The SRD's were replaced every 3 days to give a total exposure of 9 days. Plaque index (PlI), bleeding on probing and pocket depth were measured, and bacterial samples taken for dark field microscopy and anaerobic culture. There was a marked decrease in the relative proportions of spirochetes and motile rods and the total anaerobic count post-treatment. Pocket depth was reduced in all 13 pockets. These results indicate that a prolonged exposure to chlorhexidine suppresses the pocket flora to negligible amounts and reduces pocket depth for up to 11 weeks post-treatment.

Fluorescent antibody and flagella stains for rapid detection of bacteria at periodontally healthy and diseased sites

Two rapid methods of identifying bacteria associated with periodontal disease were investigated to determine their diagnostic usefulness in longitudinal or epidemiologic studies. Three nonmotile organisms were identified by fluorescent antibody stains (FA) while percentages of motile bacteria were assessed by counting all spirochetes, flagellated and nonflagellated organisms stained with a simplified silver-plating stain for flagella. Relationships between disease activity and these bacteria from subgingival plaque samples taken at 18 individual sites (12 diseased, 6 healthy) were determined by correlating the quantity of detectable bacteria with the Gingival Index (GI), Plaque Index (PLI) and probing depth (PD). The highest correlations found with the FA stains were between Bacteroides gingivalis and probing depth (rs = 0.85), GI (rs = 0.80) and PLI (rs = 0.80). Bacteroides melaninogenicus and/or Bacteroides intermedius also correlated well with the GI (rs = 0.66), PLI (rs = 0.64), and PD (rs = 0.59), but to a lesser degree than B. gingivalis. Flagella stains showed that spirochetes correlated highly with PD (rs = 0.82), as did the total motile group with PLI (rs = 0.82). Motile bacteria alone were only moderately associated with the clinical parameters measured. The results of this investigation suggest that FA- and flagella-staining methods can be valuable screening tools for the detection of bacterial species and motile organisms in longitudinal or epidemiologic studies.

The presence of bacteria in the oral epithelium in periodontal disease. II. Immunohistochemical identification of bacteria

Serial histological sections of gingiva obtained from each of six advanced adult periodontitis, two localized juvenile periodontitis and two periodontally healthy patients were used for specific identification of bacteria within the oral epithelium and adjacent connective tissue. Healthy gingival biopsies served as controls. Sections from patients and control biopsies were Gram-stained and also screened with antibacterial sera associated with the peroxidase immunocytochemical technique for specific bacterial identification. The "Pop-off" electron microscopic technique was also used to further demonstrate the bacterial nature of peroxidase-stained material. In addition, the possible correlation between bacteria and areas of possible reduced keratinization was investigated. The results showed that sections of orthokeratinized healthy gingiva did not contain bacteria. Gram-stained sections from diseased sites contained large numbers of bacteria in the oral epithelium and adjacent connective tissue. Bacteroides gingivalis and to a lesser extent Capnocytophaga gingivalis were found in periodontitis, and Actinobacillus actinomycetemcomitans was found in juvenile periodontitis when the immunoperoxidase technique was used. The bacterial nature of peroxidase-stained material was confirmed by the "pop-off" technique. In the disease biopsies, bacterial presence was correlated with areas of reduced amounts of keratin suggesting that the oral epithelium may be a portal of entry for bacteria into gingival tissues.

Pathogenesis of periodontitis

Periodontitis is an inflammatory disease of the periodontium which is characterized by a progressive destruction of the tissues supporting the tooth. Its primary etiology is an ill-defined series of microbial infections which may be composed of only some of the more than 300 species of bacteria currently recognized in the oral cavity. The disease is currently considered to progress as periodic, relatively short episodes of rapid tissue destruction followed by some repair, and prolonged intervening periods of disease remission. Despite the apparent random distribution of episodes of disease activity, the resulting tissue breakdown exhibits a symmetrical pattern of alveolar bone loss and pocket formation which is common to several forms of periodontitis, although the distribution of the most affected teeth and surfaces may vary among diseases (e.g., juvenile periodontitis versus adult periodontitis or rapidly progressive periodontitis). Several reports have indicated that bacterial cells can be found in the pocket wall of periodontitis lesions. The translocation of bacteria into the tissues from the pocket environment is quite common, as evidenced by the common occurrence of bacteremias in patients with periodontitis following relatively minor events such as chewing and oral hygiene procedures. However, it is important to distinguish between the passive introduction of bacteria into periodontal tissues and frank invasion as might occur in an acute infection, since the pathological implications may be quite different.

Bacteroides intermedius binds fibrinogen

The binding of Bacteroides intermedius VPI 8944 to human fibrinogen has been characterized. The binding is time dependent, at least partially reversible, saturable, and specific. On an average, a maximum of 3,500 fibrinogen molecules bind per bacterial cell, with a dissociation constant of 1.7 X 10(-11) M. These bacteria also exhibit a fibrinogenolytic activity which can be partially inhibited by protease inhibitors. Bacteria release fibrinogenolytic activity into the surrounding medium without loss of binding activity, but more pronounced fibrinogen breakdown occurs when 125I-labeled fibrinogen is associated with the bacteria, suggesting that fibrinogen is degraded at the cell surface. Fibrinogen binding by B. intermedius might represent a mechanism of bacterial tissue adherence.

The colonization and establishment of invading bacteria in periodontium of ligature-treated immunosuppressed rats

The morphologic features and pattern of bacterial invasion of the periodontal tissue in ligature-induced periodontal defects of immunosuppressed rats were studied. Silk ligatures were placed circumferentially on the maxillary left second molar of 24 Sprague-Dawley rats. The treatment group (14 rats) received Cytoxan (75 mg/kg) the day after ligature placement and at Day 4. The control group (10 rats) received no medication. All animals were sacrificed on Day 8 and the maxillae processed for light and electron microscopy. Only ligated sites in immunosuppressed animals exhibited bacterial invasion. Invading bacteria consisted of microcolonies of Gram-negative and Gram-positive coccoid cells and rods located near the tissue surface. Each microcolony consisted of morphologically homogeneous microorganisms. The deeper sites revealed a diffuse invasion of Gram-negative rods which appeared morphologically similar. Other features associated with invasion were complete destruction of epithelial tissue next to the ligature and the lack of inflammatory cells in the gingival region. These findings, when compared to those of other reports of tissue penetration by bacteria, point to the necessity of differentiating between bacterial invasion of gingival tissues, associated with penetration of tissues by proliferating bacteria, and bacterial translocation, a situation in which bacteria are passively carried into the tissues, for example by mechanical manipulation immediately before or during biopsy taking, or possibly during processing for histology.

Bacterial invasion of periodontal tissues in advanced periodontitis in humans

Bacterial invasion of the pocket epithelium and underlying connective tissue was found in seven cases of advanced human periodontitis. Four cases showed invasion of the epithelium as well as the connective tissue while in the other three cases bacterial invasion was limited to the pocket epithelium. The microorganisms observed included cocci, rods, filaments, fusiforms and spirochetes and these were morphologically similar to those observed in the apical zone of the subgingival plaque. Most bacteria showed typical Gram-negative cell walls. Bacteria were seen in enlarged epithelial intercellular spaces and among debris of disintegrated epithelial cells. In the connective tissue the bacteria were seen among remnants of collagen fibers and degenerated fibroblasts. Identification of the invading microorganisms may assist in understanding the pathogenesis of chronic periodontitis.

Bacterial invasion of the periodontium; an important factor in the pathogenesis of periodontitis?

Tissue samples from 2 humans suffering from severe periodontitis were investigated by transmission electron microscopy. Confirming earlier observations in gnotobiotic rats, bacteria were found in various regions of gingival tissues. We observed bacteria invading the pocket epithelium, the underlying connective tissue, and microorganisms were also present deep in the connective tissue. The bacterial invasion of the periodontium was accompanied by different stages of tissue degradation. Various morphologically distinct types of Gram-negative and Gram-positive bacteria were evident. These microorganisms were found in the apical part of the periodontium. More coronally, a heavy infiltrate consisting predominantly of plasma cells was present. It is suggested that bacteria cannot invade regions of connective tissue protected by a massive cellular infiltrate. It seems that they rather circumvent this strong defense by penetrating more apically through the pocket epithelium while producing as camouflage leukochemophobic compounds which paralyze the chemotactically regulated mobile defense. It seems to us that bacterial invasion is a consistent feature of advanced periodontitis, leading to focal necrosis or microabscesses, and may well explain the cyclic nature of this disease.