Apical periodontitis development and bacterial response to endodontic treatment. Experimental root canal infections in monkeys with selected bacterial strains

In six monkeys, 160 root canals were inoculated with a combination of four bacterial strains belonging to species Streptococcus milleri, Peptostreptococcus anaerobius, Prevotella oralis, and Fusobacterium nucleatum. In two other monkeys, 24 root canals were inoculated with a five-strain combination consisting of these strains and a strain of Enterococcus faecalis. All strains were previously isolated from an infected monkey root canal. After 8-12 months, survival of the strains was recorded bacteriologically, and the reaction in the periapical region was radiographed. From 180 of 184 root canals, one or more of the bacterial strains were reisolated. The two facultative strains were more frequently reisolated than the anaerobic strains. Apical periodontitis was registered in the periapical region of more than 96% of root canals with reisolated bacteria but in none of those without reisolated bacteria. Endodontic treatment was carried out in two sessions with an interval of 14 d without interappointment dressings, and the effect was evaluated bacteriologically before and after each treatment. The chemo-mechanical treatment reduced significantly the number of strains and bacterial cells. The facultative bacteria were more resistant to the treatment than the anaerobic bacteria. The five-strain combination had a higher survival rate than the four-strain combination.

The role of lipopolysaccharide in infectious bone resorption of periapical lesion

BACKGROUND

The role of lipopolysaccharide (LPS) in periapical lesion-induced bone resorption was investigated. Polymyxin B (PMB), a specific inhibitor of LPS, was evaluated to treat the apical lesion.

METHODS

Lipopolysaccharide isolated from two common endodontic pathogens, Fusobacterium nucleatum and Porphyromonas endodontalis, stimulated mouse macrophage (J774) to release interleukin-1alpha (IL-1 alpha) and tumor necrosis factor-alpha (TNF-alpha) in a time-dependent manner.

RESULTS

Combination of LPS further enhanced the stimulation. PMB inhibited these effects significantly. LPS also stimulated matrix metalloproteinase-1 (MMP-1) gene expression in J774, whereas anti-IL-1 alpha and anti-TNF-alpha antibodies, as well as PMB, diminished this effect. A disease model of periapical lesion was established in Wistar rat. Administration of PMB reduced the extent of lesion-associated bone resorption by 76% to approximately 80%, and simultaneously reduced the numbers of MMP-1-producing macrophages.

CONCLUSIONS

It is suggested that LPS released from the infected root canal triggers the synthesis of IL-1 alpha and TNF-alpha from macrophages. These pro-inflammatory cytokines up-regulate the production of MMP-1 by macrophages to promote periapical bone resorption.

Fusobacterium nucleatum induces premature and term stillbirths in pregnant mice: implication of oral bacteria in preterm birth

Fusobacterium nucleatum is a gram-negative anaerobe ubiquitous to the oral cavity. It is associated with periodontal disease. It is also associated with preterm birth and has been isolated from the amniotic fluid, placenta, and chorioamnionic membranes of women delivering prematurely. Periodontal disease is a newly recognized risk factor for preterm birth. This study examined the possible mechanism underlying the link between these two diseases. F. nucleatum strains isolated from amniotic fluids and placentas along with those isolated from orally related sources invaded both epithelial and endothelial cells. The invasive ability may enable F. nucleatum to colonize and infect the pregnant uterus. Transient bacteremia caused by periodontal infection may facilitate bacterial transmission from the oral cavity to the uterus. To test this hypothesis, we intravenously injected F. nucleatum into pregnant CF-1 mice. The injection resulted in premature delivery, stillbirths, and nonsustained live births. The bacterial infection was restricted inside the uterus, without spreading systemically. F. nucleatum was first detected in the blood vessels in murine placentas. Invasion of the endothelial cells lining the blood vessels was observed. The bacteria then crossed the endothelium, proliferated in surrounding tissues, and finally spread to the amniotic fluid. The pattern of infection paralleled that in humans. This study represents the first evidence that F. nucleatum may be transmitted hematogenously to the placenta and cause adverse pregnancy outcomes. The results strengthen the link between periodontal disease and preterm birth. Our study also indicates that invasion may be an important virulence mechanism for F. nucleatum to infect the placenta.

Genome analysis of F. nucleatum sub spp vincentii and its comparison with the genome of F. nucleatum ATCC 25586

We present the draft genome sequence and its analysis for Fusobacterium nucleatum sub spp. vincentii (FNV), and compare that genome with F. nucleatum ATCC 25586 (FN). A total of 441 FNV open reading frames (ORFs) with no orthologs in FN have been identified. Of these, 118 ORFs have no known function and are unique to FNV, whereas 323 ORFs have functional orthologs in other organisms. In addition to the excretion of butyrate, H2S and ammonia-like FN, FNV has the additional capability to excrete lactate and aminobutyrate. Unlike FN, FNV is likely to incorporate galactopyranose, galacturonate, and sialic acid into its O-antigen. It appears to transport ferrous iron by an anaerobic ferrous transporter. Genes for eukaryotic type serine/threonine kinase and phosphatase, transpeptidase E-transglycosylase Pbp1A are found in FNV but not in FN. Unique ABC transporters, cryptic phages, and three types of restriction-modification systems have been identified in FNV. ORFs for ethanolamine utilization, thermostable carboxypeptidase, gamma glutamyl-transpeptidase, and deblocking aminopeptidases are absent from FNV. FNV, like FN, lacks the classical catalase-peroxidase system, but thioredoxin/glutaredoxin enzymes might alleviate oxidative stress. Genes for resistance to antibiotics such as acriflavin, bacitracin, bleomycin, daunorubicin, florfenicol, and other general multidrug resistance are present. These capabilities allow Fusobacteria to survive in a mixed culture in the mouth.

[Septic shock with liver abscess in an immunocompetence patient. Presentation of an unusual Fusobacterium nucleatum infection]

BACKGROUND

Fusobacterium septicemia with septic metastasis is a very rare and potentially serous condition when complicated by septic shock. Most cases have been described in patients with humoral immunity disorders and/or severe underlying chronic disease.

CASE REPORT

A 24-year-old immunocompetent woman with a tonsil infection developed F. nucleatum septic shock with liver abscess formation. Outcome was rapidly favorable with antibiotic treatment and adapted intensive care, probably favored by the absence of an associated immune deficit.

DISCUSSION

Despite its low incidence, F. nucleatum should be entertained as a possible cause of septicemia originating from a pelviperitoneal, pulmonary with abscess formation, or upper airway infection. Proper diagnosis is essential due to the risk of poor prognosis. Fusobacterium nucleatum is a commensal strictly anaerobic bacteria of the buccal cavity. It can cause dental and upper airway infections. Septicemia with secondary localization of F. nucleatum is very rare and the severity depends on the presence of associate septic shock. The immunopathological implications of these infections remain to be elucidated.

Effect of lipopolysaccharide from periodontal pathogens on the production of tissue plasminogen activator and plasminogen activator inhibitor 2 by human gingival fibroblasts

Both tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 2 (PAI-2) are important proteolysis factors present in inflamed human periodontal tissues. The aim of the present study was to investigate the effect of lipopolysaccharide (LPS) on the synthesis of t-PA and PAI-2 by human gingival fibroblasts (HGF). LPS from different periodontal pathogens including Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Fusobacterium nucleatum were extracted by the hot phenol water method. The levels of t-PA and PAI-2 secreted into the cell culture media were measured by enzyme-linked immunosorbent assays (ELISA). The mRNA for t-PA and PAI-2 were measured by RT-PCR. The results showed t-PA synthesis was increased in response to all types of LPS studied and PAI-2 level was increased by LPS from A. actinomycetemcomitans and F. nucleatum, but not P. gingivalis. When comparing the effects of LPS from non-periodontal bacteria (Escherichia coli and Salmonella enteritidis) with the LPS from periodontal pathogens, we found that the ratio of t-PA to PAI-2 was greater following exposure of the cells to LPS from periodontal pathogens. The highest ratio of t-PA to PAI-2 was found in those cells exposed to LPS from P. gingivalis. These results indicate that LPS derived from periodontal pathogens may cause unbalanced regulation of plasminogen activator and plasminogen activator inhibitor by HGF and such an effect may, in part, contribute to the destruction of periodontal connective tissue through dysregulated pericellular proteolysis.

Lipid peroxidation caused by oxygen radicals from Fusobacterium-stimulated neutrophils as a possible model for the emergence of periodontitis

OBJECTIVE

The possible contribution of bacteria and polymorphonuclear neutrophils (PMN) to the disease process of periodontitis was evaluated.

DESIGN

Fusobacterium nucleatum has been associated with chronic adult periodontitis. Intracellular production and extracellular release of reactive oxygen species (ROS) by PMN stimulated by fusobacteria were evaluated. To estimate the potential extracellular damage that might be caused by the ROS, the lipid peroxidation (LPO) of an exogenous phospholipid, Intralipid, was assayed.

METHODS

The ROS production of PMN was studied by the nitroblue tetrazolium and chemiluminescence tests. The levels of malonaldehyde (MDA) and 4-hydroxyalkenals were used to indicate LPO.

RESULTS

Fusobacterium nucleatum strains stimulated neutrophils to produce a large amount of ROS, independently of plasma complement factors. The two strains tested induced considerable intracellular, but no extracellular chemiluminescence responses during the first hour, indicating that ROS were released into phagosomes. However an incubation period of 4 h, in the presence of the extracellular lipid resulted in a high degree of LPO, presumably caused by ROS release from the Fusobacterium-stimulated PMN. ROS production and lipid peroxidation could be counteracted by vitamin E.

CONCLUSION

In periodontitis local bacteria might stimulate PMN to release ROS, which cause inflammation and destruction.

The virulence of mixed infection with Streptococcus constellatus and Fusobacterium nucleatum in a murine orofacial infection model

Orofacial infections are usually polymicrobial, and it is the microbial interactions of pathogenic species that cause tissue destruction. In this study, the microbial interaction between Streptococcus constellatus and Fusobacterium nucleatum was characterized using a murine orofacial infection model. A mixture of viable S. constellatus and F. nucleatum cells (both 2 x 10(8) CFU/mouse) was injected into the submandible; as a result, all of the test mice died. In contrast, none of the experimental animals monoinjected with either S. constellatus or F. nucleatum died (P<0.001), indicating that the synergism between the two resulted in the virulence. When a mixture of viable S. constellatus cells and a culture filtrate of F. nucleatum was tested, lethality and the bacterial cell count per lesion were significantly enhanced as compared with monoinjections (P<0.02). However, the virulence of F. nucleatum was not enhanced by infection of a culture filtrate of S. constellatus. The enhancement of virulence was observed even when viable S. constellatus cells and the culture filtrate of F. nucleatum were injected at separate sites. Heat treatment of the culture filtrate of F. nucleatum did not affect the enhancement. These results indicate that a heat-stable substance(s) produced by F. nucleatum contributes to the microbial synergy of S. constellatus and F. nucleatum in orofacial infections.

Cytokine, elastase and oxygen radical release by Fusobacterium nucleatum-activated leukocytes: a possible pathogenic factor in periodontitis

Periodontitis is characterised by tissue destruction caused by reactive oxygen species (ROS) and proteolytic enzymes, which are released by the interaction between bacteria and phagocytes. We estimated the ability of Fusobacterium species to induce release of tissue destructive and proinflammatory mediators from in vitro activated peripheral leukocytes. ROS was measured with the nitroblue tetrazolium (NBT) method, elastase with a specific chromogenic substrate and cytokines, including interleukin 1beta (IL-1beta), tumour necrosis factor alpha (TNF-alpha), and interleukin 8 (IL-8) with a sandwich ELISA method. Various clinical isolates of unopsonized Fusobacterium species stimulated the neutrophils to an increased NBT- reduction. IL-1beta, TNFalpha, IL-8 and elastase were released in significantly higher levels from neutrophils stimulated by Fusobacterium species. In conclusion, unopsonized Fusobacterium species can induce increased production of oxygen radicals, cytokines and elastase from leukocytes activated in vitro.

[The neutralizing effect of histidine-rich-polypeptides on LPS from suspected periodontal pathogens]

OBJECTIVE

Human parotid histidine-rich-polypeptides (HRPs) are a family of lowmolecular-weight, cationic polypeptides. HRP-1, HRP-3 and HRP-5 comprise 85%-90% of the total HRPs and are called major HRPs. There were many researches indicating the antimicrobial activities of HRPs. Recently, HRPs were reported to have an inhibitory action on the lipopolysaccharide (LPS) of E. coli, with HRP-5 being the most effective one among the three major HRPs. Since the LPS of oral gram-negative bacteria is thought to be one of the important etiological factors during the development of periodontal diseases, our experiment was aimed to investigate the neutralizing effect of human parotid HRP-5 on the LPS of anaerobic suspected periodontal pathogens, which have different chemical structures and biological activities compared with LPS of aerobic E. coli.

METHODS

By using of preparative acid urea polyacrylamide gel electrophoresis (AU-PAGE), HRP-5 was purified from parotid saliva collected from healthy adults. Two stains of suspected periodontal pathogens, Porphyromonas gingivalis (P.g, 47-A) and Fusobacterium nuceatum (F. n, separated from subgingival plaque of a patient with adult periodontitis) were mass cultured. After harvested in the midlogarithmic phase, they were washed and lyophilized. The LPS of dried bacteria were extracted by the modified Westphal hot phenol-water procedures and purified by the enzyme digestion plus ultracentrifugation. Limulus test was applied to test the neutralizing effect of HRP-5 on the LPS-induced gelation of Limulus amoebocyte lysate. In brief, the standard LPS of E. coli, or extracted LPS of P. g or F. n, was preincubated with HRP-5 in a tube separately in room temperature for 10 minutes. Then the reagent of Limulus amoebocyte lysate was added in all the tubes, continued the incubation in 37 degrees C for one hour. After that, the gelation level of every tube was observed.

RESULTS

LPS extracted from P. g and F. n both showed good purity and strong activities to induce gelation of Limulus amoebocyte lysate. The gelation induced by LPS (1 ng/ml) of these two anaerobic suspected periodontal pathogens were weakly inhibited by HRP-5 (10 micrograms/ml), similar to that observed with standard LPS of E. coli. To get a complete neutralizing effect on LPS, it may be important to increase the concentration of HRP-5.

CONCLUSION

It appeared that HRPs could neutralize the endotoxic properties of LPS of suspected periodontal pathogens, therefore may contribute to periodontal health. The present investigation further confirmed that HRPs are important components of the host non-immune defense system.

[Bacterial virulence in the etiology of periodontal diseases]

Strong relationships have been very often described between various form of periodontal disease (PD) and certain bacterial species, so that nowadays periodontal disease is recognized as an infectious disease. Destruction of periodontal supporting tissues happens as a response to very intricate host-parasite interactions. When the clinician will be able to fully understand and identify such phenomena it would be possible to succeed in a properly diagnosis and control of the active phase of periodontal disease. The first step in such a direction would be to analyze the common characteristic of some bacterial species, the so called suspected periodontopathogens. Such species namely Gram-negative, associated with the outbreak of periodontal disease have in common the capacity to disrupt the integrity of the host defences by means of the so called virulence factors. These factors may enhance the bacterial colonization or may interfere with the host response that ultimately results in periodontal support breakdown. The present review focuses on the virulence factors of the main suspected periodontopathogens evaluating the effects on the host immune response and directly on the periodontal tissues.

Fusobacterium nucleatum involvement in adult periodontitis and possible modification of strain classification

BACKGROUND

This investigation was designed to evaluate the involvement of Fusobacterium nucleatum clinical strains in adult periodontitis by subspecies and expression of hemagglutination activity.

METHODS

Forty-nine Fusobacterium strains were isolated from 40 sites in 40 subjects presenting with adult periodontitis. F. nucleatum subspecies identification was based on the electrophoretic migration of glutamate dehydrogenase and 2-oxoglutarate reductase. Hemagglutination activity and inhibition by galactose were tested on sheep erythrocytes.

RESULTS

The 49 isolates belonged to the F. nucleatum species with a predominance of the nucleatum (34.7%) followed by the vincentii (26.5%) subspecies. In parallel, 71% of the strains belonging to the nucleatum subspecies were preferentially associated with Porphyromonas gingivalis. Prevotella intermedia/nigrescens detection was essentially correlated with identification of Fusobacterium nucleatum subspecies vincentii. No correlation was established between any particular subspecies and the pathogenicity factors tested (hemagglutination and production of short-chain fatty acids). On the other hand, significant predominance (65%, P= 0.017) of strongly hemagglutinating strains (titre > or =8 U) was observed in the sites where Porphyromonas gingivalis, Prevotella intermedia/nigrescens and/or Campylobacter rectus were not detected. These strains also showed higher butyric acid production.

CONCLUSION

The importance of the adherence factors for Fusobacterium nucleatum strains and their multimodal aspect may indicate a higher pathogenicity or a higher involvement of certain strains and could lead to a classification of these strains, which is more closely related to their implication in the development of periodontal disease.

Anaerobic bacterial extracts influence production of matrix metalloproteinases and their inhibitors by human dental pulp cells

The role of human dental pulp (HDP) cells in extracellular matrix degradation in pulpitis is still unclear. In this study, the effects of sonicated bacterial extracts (SBEs) from Prevotella intermedia, Fusobacterium nucleatum, Porphyromonas endodontalis, and Porphyromonas gingivalis on the balance between the production of matrix metalloproteinases (MMPs) and that of their inhibitors [tissue inhibitors of metalloproteinases (TIMPs)] by HDP cells were examined. HDP cells were treated with SBEs, and their culture media were later harvested. MMP activities and TIMP concentrations were determined by use of independent measurement strategies and sensitive ELISAs. The production of MMP-1 and MMP-2 was accelerated by all SBE. On the other hand, TIMP-1 production was slightly elevated; and TIMP-2 production was markedly inhibited by all of the extracts. SBEs derived from these anaerobic bacteria seemed to affect the acceleration of extracellular matrix degradation activity by HDP cells. These findings suggest that HDP cells stimulated by bacterial byproducts may be involved in the pathogenesis of pulpitis.

Interactions between periodontal bacteria and human oral epithelial cells: Fusobacterium nucleatum adheres to and invades epithelial cells

Bacteria are causative agents of periodontal diseases. Interactions between oral bacteria and gingival epithelial cells are essential aspects of periodontal infections. Using an in vitro tissue culture model, a selected group of gram-negative anaerobic bacteria frequently associated with periodontal diseases, including Bacteroides forsythus, Campylobacter curvus, Eikenella corrodens, Fusobacterium nucleatum, Porphyromonas gingivalis, and Prevotella intermedia, were examined for their ability to adhere to and invade primary cultures of human gingival epithelial cells (HGEC). The effects of these bacteria on the production of interleukin-8 (IL-8), a proinflammatory chemokine, were also measured. These studies provided an initial demonstration that F. nucleatum adhered to and invaded HGEC and that this was accompanied by high levels of IL-8 secretion from the epithelial cells. The attachment and invasion characteristics of F. nucleatum were also tested using KB cells, an oral epithelial cell line. The invasion was verified by transmission electron microscopy and with metabolic inhibitors. Invasion appeared to occur via a "zipping" mechanism and required the involvement of actins, microtubules, signal transduction, protein synthesis, and energy metabolism of the epithelial cell, as well as protein synthesis by F. nucleatum. A spontaneous mutant, lam, of F. nucleatum, isolated as defective in autoagglutination, was unable to attach to or invade HGEC or KB cells, further indicating the requirement of bacterial components in these processes. Sugar inhibition assays indicated that lectin-like interactions were involved in the attachment of F. nucleatum to KB cells. Investigation of these new virulence phenotypes should improve our understanding of the role of F. nucleatum in periodontal infections.

Acquisition of plasmin activity by Fusobacterium nucleatum subsp. nucleatum and potential contribution to tissue destruction during periodontitis

Fusobacterium nucleatum subsp. nucleatum has been associated with a variety of oral and nonoral infections such as periodontitis, pericarditis, bone infections, and brain abscesses. Several studies have shown the role of plasmin, a plasma serine protease, in increasing the invasive capacity of microorganisms. In this study, we investigated the binding of human plasminogen to F. nucleatum subsp. nucleatum, and its subsequent activation into plasmin. Plasminogen-binding activity of bacterial cells was demonstrated by a solid-phase dot blot assay using an anti-plasminogen antibody. The binding activity was heat resistant and involved cell-surface lysine residues since it was abolished in the presence of the lysine analog epsilon-aminocaproic acid. Activation of plasminogen-coated bacteria occurred following incubation with either streptokinase, urokinase-type plasminogen activator (u-PA), or a Porphyromonas gingivalis culture supernatant. In the case of the P. gingivalis culture supernatant, a cysteine protease was likely involved in the activation. The plasmin activity generated on the cell surface of F. nucleatum subsp. nucleatum could be inhibited by aprotinin. Activation of plasminogen by u-PA was greatly enhanced when plasminogen was bound to bacteria rather than in a free soluble form. u-PA-activated plasminogen-coated F. nucleatum subsp. nucleatum was found to degrade fibronectin, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Tissue inhibitor of metalloproteinase-1 was also degraded by the plasmin activity generated on the bacterial cells. This study suggests a possible role for plasminogen, which is present in affected periodontal sites, in promoting tissue destruction and invasion by nonproteolytic bacteria such as F. nucleatum subsp. nucleatum.

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.

Cytotoxic effect of endodontic bacteria on periapical fibroblasts

This study was conducted to investigate the effects of sonicated bacterial extracts (SBEs) from anaerobic Gram-negative bacteria on periapical fibroblast obtained from the apical portion of human periodontal ligaments. Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, and Fusobacterium nucleatum were chosen from among the endodontic bacteria isolated from root canals having a periapical lesion and compared in terms of their cytotoxicity. The purpose of this study was to examine which bacteria are involved in the development of periapical inflammation. The anaerobes were cultured under strict anaerobic conditions, and the bacterial cells were then harvested by centrifugation after incubation. The concentrated cell suspensions were sonicated and subsequently centrifuged. An SBE was made of each of the filtered supernatants. Each SBE was added to cultures of periapical fibroblasts. The cell growth and proliferation were measured by the MTT method after 3, 5, and 7 days. The SBEs from P. endodontalis, P. gingivalis, and F. nucleatum inhibited the growth of the fibroblasts, whereas the SBE from P. intermedia did not inhibit it. The SBEs from P. gingivalis and F. nucleatum inhibited the fibroblast growth more strongly than did the P. endodontalis, P. gingivalis, and F. nucleatum may participate in the development of periapical lesions.

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.

Evidence for genetic control of changes in f-actin polymerization caused by pathogenic microorganisms: in vitro assessment using gingival fibroblasts from human twins

Attachment to and migration upon a substratum, as well as other functions of connective tissue cells, are regulated mainly by cytoplasmic structural proteins, particularly filamentous actin (f-actin). Pathogenic microorganisms exert negative effects on cytoskeletal proteins. In the present study, normal gingival fibroblasts from 10 sets of human twins (6 fraternal, DZ; 4 identical, MZ) were exposed to soluble extracts from Porphyromonas gingivalis or Fusobacterium nucleatum, then f-actin was stained using FITC-labeled phalloidin. Cells were examined under fluorescence, and a computer-assisted image analyzer quantitated f-actin polymerization as fluorescence intensity on a per-cell basis. Intraclass correlation coefficients for f-actin in MZ/MZ vis-a-vis DZ/DZ paired cell cultures were determined to assess the possible heritability of responses to the microorganism preparations. F-actin labeling was significantly different between control cultures and those exposed to the extracts. Both F. nucleatum and P. gingivalis effected f-actin and fibroblast morphology. When the data were adjusted for gender and age effects, and for differences in control f-actin levels, fibroblasts from MZ twin pairs were moderately similar in both absolute and relative responses to bacterial challenges; cells from DZ twins showed little similarity when response was measured on the absolute scale, and moderate similarity using the relative scale.

Alveolar bone loss in rats infected with a strain of Prevotella intermedia and Fusobacterium nucleatum isolated from a child with prepubertal periodontitis

Prevotella intermedia and fusobacterium nucleatum are associated with various forms of periodontal disease. The purpose of the present study was to infect the clinical isolates of these periodontopathic bacteria and to induce a significant loss of alveolar bone in specific pathogen-free (SPF) rats in the absence of ligatures. P. intermedia YKD8 and F. nucleatum YKZ5 were isolated from a prepubertal periodontitis patient, while P. gingivalis MWB13 was from a patient with juvenile periodontitis. At first, SPF Sprague-Dawley rats (70 days of age, male) were infected with A. viscosus Ny1R and subsequently superinfected with P. gingivalis MWB13, P. intermedia YKD8, or F. nucleatum YKZ5, respectively. The control group was infected with A. viscosus Ny1R alone. All rats were killed and periodontal bone levels were assessed morphometrically 135 days after the first infection with A. viscosus. P. intermedia YKD8 was recovered frequently from rats, with serum antibody levels remaining highly elevated throughout the experiment. Significant loss of alveolar bone was found in rats infected with P. intermedia YKD8, the virulence of which was equivalent to that of P. gingivalis MWB13. F. nucleatum YKZ5 also induced alveolar bone loss, but not significantly when compared with rats infected with A. viscosus Ny1R alone.

Strong cytotoxicity to human gingival fibroblasts by Porphyromonas gingivalis ATCC 33277

The aim of the present study was to analyze the cytotoxicity of some bacterial species associated with periodontal diseases. The specificity of cytotoxicity was estimated against cells of various origin and from different individuals. The reference bacteria were Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Fusobacterium nucleatum. These bacteria were cultured for 24 h in liquid media and the supernatants were used in cytotoxicity assays. The target cells used were human gingival fibroblasts (GF), dermal fibroblasts (K4), gingival epithelial cells (E) and HeLa-cells (HeLa). These cells were exposed at 4 h or 24 h, respectively, to various concentrations of culture supernatants from the selected bacteria. The influence on the viability and metabolism of the cells were estimated quantitatively as increase in neutral red uptake and lactic acid production. Growth medium supernatants of P. gingivalis 33277 were strongly cytotoxic to gingival fibroblasts after 24 h incubation, compared to supernatants of P. gingivalis 381 or W 50, A. actinomycetemcomitans or F. nucleatum cultures. The toxic effect of P. gingivalis 33277 decreased drastically after heat inactivation, which indicates effects of proteins. By adding anti-sera the cytotoxicity of P. gingivalis 33277 could be dose dependently neutralized, which was not the case when supernatants of A. actino-mycetemcomitans was tested. Target cells of epithelial origin did not show increased cytotoxicity to P. gingivalis 33277. The results of the present study strengthen the hypothesis that P. gingivalis remains as a suspect causative key component in periodontal diseases.

Mixed infection with Porphyromonas gingivalis and Fusobacterium nucleatum in a murine lesion model: potential synergistic effects on virulence

These studies determined the characteristics of tissue destruction in a murine abscess model elicited by mixed infection with the periodontopathogens Fusobacterium nucleatum and Porphyromonas gingivalis. The interbacterial effects of this synergism, the kinetics of the relationship of the bacterial interaction, and the characteristics of the bacteria required for the tissue destruction were studied. Infection of mice with P. gingivalis and F. nucleatum strains elicited lesions of various sizes as a function of infective dose. Primary infection with F. nucleatum plus P. gingivalis at various ratios (i.e., <1:1) resulted in a significantly greater lesion size (P < 0.001) compared with that resulting from primary infection with P. gingivalis alone. At F. nucleatum/P. gingivalis ratios of > or = 1:1, spreading lesion formation and progression were significantly (P < 0.001) decreased, suggesting that bacterial interaction (i.e., coaggregation) may have inhibited the spread of the P. gingivalis infection to a site distant from the initial injection. Infection with F. nucleatum and P. gingivalis simultaneously (at different sites) or F. nucleatum administered within 4 h prior to or 1 h following P. gingivalis infection significantly enhanced the ability of P. gingivalis to form large phlegmonous lesions. Chemical inhibition of the P. gingivalis trypsin-like protease activity or the use of a trypsin-negative P. gingivalis strain abrogated tissue destruction either alone or in combination with F. nucleatum. Therefore, it was possible to examine aspects of virulence of these pathogens in a murine lesion model by either altering bacterial ratios, manipulating the time of infection, or targeting vital bacterial virulence factors.

Effects of sublethal exposure to an antiseptic mouthrinse on representative plaque bacteria

Although the mechanism responsible for the clinical antiplaque efficacy of oral antiseptics is generally considered to be primarily one of bactericidal activity, it has been suggested that oral antiseptics may have additional effects on bacteria exposed to sublethal levels. Studies reported herein, investigated the effects of sublethal levels of an essential oil-containing antiseptic mouthrinse (Listerine Antiseptic, Warner-Lambert Co., Morris Plains, NJ) on selected activities of representative plaque microorganisms using in vitro models. These studies demonstrated that sublethal exposure to the tested oral antiseptic can have significant effects in reducing intergeneric coaggregation, increasing bacterial generation time, and extracting endotoxin from Gram-negative bacteria. These in vitro activities can be correlated with features of plaque formation and pathogenicity seen in vivo; however, additional studies will be necessary to confirm that these mechanisms are, in fact, operative clinically.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

Endodontic pathogens: propagation of infection through patent dentinal tubules in traumatized monkey teeth

Periapical pathology indicating endodontic infection, when present in marginal periodontitis-affected teeth, has recently been shown to be an aggravating factor in progression of marginal destruction. This has been associated with patency of dentinal tubules in the tooth cervix, an area normally devoid of cementum following periodontal therapy. These studies are, however hampered by that only circumstantial evidence such as presence of periapical destruction have been applied as criteria of endodontic infection. The purpose of the present investigation was to study to what extent a predefined selection of endodontic pathogens inoculated in the root canal can influence periodontal pathology and healing in areas of the root covered by or devoid of cementum, using root resorption as a histomorphometric marker. Exposed dentine surfaces, in the present study showed significantly larger areas of resorption in infected roots compared to non-infected roots, while cementum surfaces showed an almost identical distribution of tissue reactions regardless of root canal infection or not. It was concluded that endodontic pathogens or their products were not able to penetrate the cementum barrier. The significantly larger areas of resorption on exposed dentine surfaces in infected roots compared to non-infected roots indicated that endodontic pathogens or their products could spread through dentinal tubules to a root surface void of cementum. Extrapolated to the marginal situation this indicated that endodontic pathogens in the root canal might be able to aggravate marginal infection in areas of root devoid of cementum.