Attachment of Bacteroides melaninogenicus subsp. asaccharolyticus to oral surfaces and its possible role in colonization of the mouth and of periodontal pockets

Effect of host responses on the pathogenicity of strains of Porphyromonas gingivalis

Porphyromonas gingivalis is implicated in the etiology of periodontitis. Strains of P. gingivalis have been classified as invasive or noninvasive based on their ability to form abscesses in a mouse model. The purpose of this study was to investigate the ability of P. gingivalis strains to cause abscesses and periodontal bone loss in an experimental rat model and the effect of serum and salivary responses on the pathogenicity of these strains. Subcutaneous injection of animals with P. gingivalis 33277, A7A1-28, W50 or 381 resulted in abscesses in a higher percentage of mice than rats. P. gingivalis 33277 caused lesions at the site of injection, whereas strains A7A1-28 and W50 induced abscesses at distant sites in both mice and rats. Local lesions were seen in rats injected with strain 381, whereas lesions formed distant from the site of injection in mice. When periodontal bone loss was assessed in the experimental rat model, animals challenged with 33277 had the highest amount of horizontal and vertical bone loss. Rats challenged with strain A7A1-28, W50 or 381 had some or no periodontal bone loss compared with controls. Assessment of antibody responses to P. gingivalis in these animals revealed that rats challenged with 33277 had lower levels of serum immunoglobulin G-(IgG) and especially salivary IgA antibody activity than A7A1-28-challenged rats. Serum IgG and in particular salivary IgA anti-P. gingivalis responses were seen in W50- and 381-challenged rats. These results indicate that the ability of P. gingivalis strains to cause abscesses does not relate directly to their periodontal pathogenicity as assessed by periodontal bone loss in the same animal model. The results further suggest the importance of salivary IgA antibody responses in protection against experimental periodontal bone loss after challenge with P. gingivalis.

Bacterial adherence to the surface and isolated cell epithelium of the palatine tonsils

Bacterial adherence to the oropharyngeal epithelium is a significant factor in normal microecology, etiopathogenesis of diseases (tonsillitis, gingivitis) and possibly also induction of immune response. Bacterial adhesion to human tonsillar epithelium of whole tonsils and swabs was studied by fluorescence, scanning, and transmission electron microscopy. The epithelial cell borders were well demarcated. On the apical surface of the cells there were irregular microridges. All forms of microscopy visualized epithelial cells with attached bacteria, often forming microcolonies on the free surface. Some bacteria formed excavations on the cell surface. Most attached bacteria were coccoid, but variously sized rods were also visible. In transmission electron microscopy, epithelial cells with intracellular bacteria were regularly observed.

Phototoxicity of argon laser irradiation on biofilms of Porphyromonas and Prevotella species

Species of Prevotella (Pr.) and Porphyromonas (Po.) and other microorganisms were cultivated as biofilms on agar medium and examined for their susceptibility to argon laser irradiation (continuous mode; wavelengths, 488-514 nm; fluences, 20-200 J cm(-2)). Fluences of 35 to 80 J cm(-2) inhibited biofilm growth in Po. endodontalis, Po. gingivalis, Pr. denticola, Pr. intermedia, Pr. melaninogenica and Pr. nigrescens. A fluence of 70 J cm(-2) did not affect biofilm growth in species of Bacillus, Candida, Enterobacter, Proteus, Pseudomonas, Staphylococcus and Streptococcus. The phototoxic effects of argon laser irradiation against Prevotella and Porphyromonas species were: (1) caused by the radiation alone; (2) modified by biofilm age; (3) dependent on the presence of atmospheric oxygen; (4) influenced by medium supplements of hemin, hemoglobin and blood; (5) greater when compared with other microbial species; (6) demonstrated without augmentation with an exogenous photosensitizer; and (7) apparently unrelated to the protoporphyrin content of the cells. Overall, these in vitro findings suggest that low doses of argon laser radiation may be effective in the treatment and/or prevention of clinical infections caused by biofilm-associated species of Prevotella or Porphyromonas.

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.

Human oral microbial ecology and dental caries and periodontal diseases

In the human oral cavity, which is an open growth system, bacteria must first adhere to a surface in order to be able to colonize. Ability to colonize a non-shedding tooth surface is necessary prior to any odontopathic or periodontopathic process. Complex microbe-host relationships occur and must be studied before the commensal-to-pathogenic nature of the human indigenous oral flora can be understood. Medical pathogens, if present in the appropriate host, always produce specific disease. Caries and periodontal diseases are conditional diseases, requiring numbers of certain indigenous species at various sites, particularly the tooth surface. In the case of caries, the condition is related to sugar consumption. Periodontal disease/s may require certain host and environmental conditions, such as local environment or nutritional factors in gingival crevicular fluids. Nonetheless, critical numbers of certain indigenous species must be present in order for these diseases to occur. The aim of this review is to understand the acquisition of the indigenous oral flora and the development of human dental plaque. The role of the salivary pellicle and adherence of indigenous bacteria to it are critical first steps in plaque development. Bacterial interactions with saliva, nutritional factors, growth factors, and microbial physiologic processes are all involved in the overall process of microbial colonization.

Construction and preliminary characterization of three hemagglutinin mutants of Porphyromonas gingivalis

Targeted insertional mutagenesis was used to construct hagA, hagB, and hagC hemagglutinin mutants of Porphyromonas gingivalis. pJRD215-derived plasmids containing tetA(Q)2 and portions of the targeted genes were conjugated into P. gingivalis. Interruption of the three loci was confirmed by Southern hybridization, sequencing, reverse transcription-PCR, and microtiter hemagglutination assays. No significant differences in hydrophobicity or coadherence to Actinomyces viscosus were detected between the mutants and the wild-type strain.

Duplication and differential expression of hemagglutinin genes in Porphyromonas gingivalis

A third hemagglutinin gene, defined as hagC, was cloned from Porphyromonas gingivalis 381 and sequenced. This gene was found to encode a protein highly homologous (98.6%) to the previously reported HagB hemagglutinin protein. The upstream and downstream regions of hagB and hagC were found to share less than 40% homology compared with 99% for their open reading frames. The antigenic relationship between the two hemagglutinins was demonstrated by Western blot analysis. When expressed in an in vitro transcription-translation system, both genes encoded a protein with a molecular mass of 49 kDa. As determined by reverse transcription polymerase chain reaction, the steady-state levels of hagB and hagC mRNAs were found to vary according to the growth phase and hemin concentration. The amount of transcripts decreased in hemin-limited conditions or in the absence of hemin. Furthermore, hagB mRNAs were detected in the early logarithmic growth phase compared with the hagC transcripts, which were detected only in the mid-exponential phase of growth.

Selection and phenotypic characterization of nonhemagglutinating mutants of Porphyromonas gingivalis

To further investigate the relationship between fimbriae and the hemagglutinating adhesin HA-Ag2 of Porphyromonas gingivalis, three spontaneous mutants of the type strain ATCC 33277 were selected by a hemadsorption procedure. They were characterized for hemagglutination, trypsin-like and lectin-binding activities, and hydrophobicity and for the presence of fimbriae. The presence of the 42-kDa (the fimbrilin subunit) and the 43- and 49-kDa (the HA-Ag2 components) polypeptides was investigated by immunoblotting using polyclonal and monoclonal antibodies directed to fimbriae and to the hemagglutinating adhesin HA-Ag2. Cells from two of the three mutants (M1 and M2) exhibited no or little hemagglutination activity and very low trypsin-like activity and did not show the 43- and 49-kDa polypeptides. Abnormal fimbriation in M1 was deduced from the following observations of cells grown for 18 h: absence of the 42-kDa polypeptide and of a 14-kDa polypeptide and no fimbriae visible on electron micrographs. While the cells of mutant M2, irrespective of the age of the culture, were found to lack the 43- and 49-kDa polypeptides and hemagglutination activity, the supernatants of cultures grown for 72 h had high hemagglutination and trypsin-like activities and revealed the presence of the 42-, 43-, and 49-kDa polypeptides. This suggests that M2 may be missing some molecules which anchor the components to the cell surface. Mutant M3 showed levels of activities similar to those of the parental strain but lacked the 43-kDa polypeptide. Other pleiotropic effects observed for the mutants included loss of dark pigmentation and lower hydrophobicity. The data from this study fuel an emerging consensus whereby fimbriation, hemagglutination, and proteolytic activities, as well as other functions in P. gingivalis, are intricate.

Prevotella intermedia fimbriae mediate hemagglutination

Our earlier studies demonstrated that clinical strains of Prevotella intermedia, isolated from human periodontal pockets, possess various types of fimbria (surface appendages) as determined ultrastructurally. These bacteria have the ability to agglutinate selected mammalian erythrocytes. Hemagglutinating activity exhibited by these cells may be attributable to these surface structures. Strain 17, which possess fimbriae of 8 nm in diameter and readily agglutinates human, monkey, sheep, rabbit, and mouse erythrocytes was selected to determine whether these fimbriae possessed the hemagglutinating activity. Fimbriae were mechanically sheared, concentrated by ammonium sulfate precipitation, solubilized in 10 mM Tris-HCl buffer containing 0.5% deoxycholate and partly purified by ultracentrifugation in a 10-50% linear sucrose gradient. Isolated fimbriae banded at a density of 1.20-1.15 g/ml, appeared fairly uniform ultrastructurally, and possessed hemagglutinating activity. The hemagglutinating activity of P. intermedia whole cells and isolated fimbriae was reduced by treatment with proteases and eliminated by treatment with heat at 80 degrees C for 10 min. The optimal pH for the hemagglutination was 7.0. In the process of hemagglutination, P. intermedia whole cells and isolated fimbriae bound to rabbit erythrocytes as observed by: (a) decrease in the hemagglutinating activity of bacterial whole cells and isolated fimbriae after incubation with rabbit erythrocytes, (b) increase in hemagglutinating activity of the red cells used for absorption, and (c) the presence of P. intermedia whole cells and fimbriae on red cells after absorption as revealed by immunoelectron microscopy. Both the immune immunoglobulin G of the rabbit polyclonal anti-fimbriae antibody and the immune immunoglobulin G and its Fab fragments of the murine monoclonal anti-fimbriae antibody were effective inhibitors of hemagglutination mediated by isolated fimbriae. Immunogold labeling showed that the monoclonal antibody bound specifically to P. intermedia fimbriae. These results collectively suggest that the hemagglutination exhibited by P. intermedia may be attributable to the fimbriae or the fimbrial-associated components.

Porphyromonas gingivalis endotoxin affinity for dental ceramics

This study evaluated the effects of chemical composition, surface treatment, and initial exposure dose on Porphyromonas gingivalis lipopolysaccharide adherence to and elution from dental ceramics. Lipopolysaccharide, commonly known as endotoxin, can initiate a variety of biologic responses. Opaque, body, and Dicor ceramic disks were individually exposed to 250, 1000, or 2500 EU/ml 3H-lipopolysaccharide and incubated for 24 hours at 37 degrees C. Disks were then transferred to fresh lipopolysaccharide-free water and incubated for up to 96 hours to evaluate elution. Mean initial lipopolysaccharide adherence ranged from 0.397 +/- 0.048 EU/mm2 to 5.056 +/- 0.117 EU/mm2. Greater initial exposure levels resulted in greater adherence, and at higher lipopolysaccharide exposure levels, lipopolysaccharide adherence differences were based on ceramic type. Mean lipopolysaccharide elution levels ranged from 0.063 +/- 0.02 EU/mm2 to 0.00 EU/mm2 at 96 hours for all groups. Greater initial adherence resulted in greater elution. Ceramic type did not affect elution. Surface finish affected elution at the 2500 EU exposure level. The affinity of lipopolysaccharide for dental ceramics could contribute to a periodontal inflammatory process.

Interbacterial binding among strains of pathogenic and commensal oral bacterial species

Strong interspecies adherence was demonstrated among the periodontal pathogens Treponema denticola, Bacteroides forsythus and Porphyromonas gingivalis, and between these pathogens and the commensal plaque organism Streptococcus crista. Adherence showed specificity and demonstrated saturation binding kinetics. Binding between B. forsythus and P. gingivalis appeared to be a unimodal protein-protein interaction. Binding between the other organisms was at least bimodal involving interactions between combinations of proteins and carbohydrates with a variety of sugar specificities. Salivary molecules prevented adherence between T. denticola and S. crista, and serum eliminated B. forsythus binding to P. gingivalis. All other interactions occurred to some degree in the presence of serum and saliva. Such interbacterial binding interactions may be important in the establishment of periodontopathic plaque.

Antigenic, structural, and functional relationships between fimbriae and the hemagglutinating adhesin HA-Ag2 of Porphyromonas gingivalis

While the adhesive properties of Porphyromonas gingivalis are known to allow colonization of the subgingival tissues, the roles of fimbriae and adhesin molecules in hemagglutination remain unclear. The purpose of this study was to analyze the antigenic, structural, and functional relationships of these two components. Five populations of monoclonal antibodies were produced against (i) the hemagglutinating adhesin HA-Ag2 resolved by crossed immunoelectrophoresis (CIE), (ii) native fimbriae, and (iii) each of the three immunoprecipitates, Ag8a, Ag8b, and Ag8c, that define fimbriae by CIE. The tests used for characterization of the monoclonal antibodies included immunoblot reactivity, inhibition of hemagglutination, capacity to dissociate immunoprecipitates by CIE, localization of recognized epitopes by immunoelectron microscopy, and epitope mapping by competition enzyme-linked immunosorbent assay. The results from the different immunochemical tests clearly showed a close antigenic relationship between fimbriae and the hemagglutinating adhesin HA-Ag2. We were able to establish that the epitopic domain H1 of HA-Ag2 is hemagglutinin specific and that domain F2 is fimbria specific. Our data indicate that the polymeric structural unit of fimbriae must be complexed to HA-Ag2, the adhesin, to confer hemagglutination activity to the bacterial cells.

Reactive antibodies in sera from pubertal and adult gingivitis patients against various Porphyromonas gingivalis antigens

This study was undertaken to determine the immunodominant antigens from Porphyromonas gingivalis which reacted with sera from patients of pubertal and adult gingivitis. The patients with cultivable P. gingivalis and the patients without cultivable P. gingivalis were compared by immunoblots. Fifty subjects participated in this study: 20 with gingivitis, 20 periodontally healthy, and 10 with adult periodontitis. The groups with gingivitis and healthy periodontium each contained 10 pubescent subjects and 10 adult subjects. P. gingivalis was isolated from 9 of 20 patients with gingivitis and from all of 10 with periodontitis by culture study. Approximate molecular weight 43 KDa fimbriae antigen, 57, 53, 46, 28 KDa antigens from outer membrane, and 57, 44, 40, 18.5 KDa antigens from sonicated extracts of P. gingivalis reacted significantly more frequently with sera from the P. gingivalis culture-positive gingivitis patients than with sera from the culture-negative patients by Fisher's exact test. A molecular weight 75, 31 KDa antigen from outer membrane and a 46 KDa antigen from sonicated extract were immunodominant in sera from adult patients with periodontitis. These findings indicate that the specific antigens which reacted with sera from P. gingivalis culture-positive patients are markers of infection with P. gingivalis. Additionally, reactivity to antigens were slightly different between sera from patients with gingivitis and those from patients with periodontitis.

Porphyromonas gingivalis invasion of gingival epithelial cells

Porphyromonas gingivalis, a periodontal pathogen, can invade primary cultures of gingival epithelial cells. Optimal invasion occurred at a relatively low multiplicity of infection (i.e., 100) and demonstrated saturation at a higher multiplicity of infection. Following the lag phase, during which bacteria invaded poorly, invasion was independent of growth phase. P. gingivalis was capable of replicating within the epithelial cells. Invasion was an active process requiring both bacterial and epithelial cell energy production. Invasion was sensitive to inhibitors of microfilaments and microtubules, demonstrating that epithelial cell cytoskeletal rearrangements are involved in bacterial entry. P. gingivalis, but not epithelial cell, protein synthesis was necessary for invasion. Invasion within the epithelial cells was not blocked by inhibitors of protein kinase activity. Invasion was inhibited by protease inhibitors, suggesting that P. gingivalis proteases may be involved in the invasion process. Low-passage clinical isolates of P. gingivalis invaded with higher efficiency than the type strain. Serum inhibited invasion of the type strain but had no effect on the invasion of a clinical isolate. Invasion of gingival epithelial cells by P. gingivalis may contribute to the pathology of periodontal diseases.

Porphyromonas gingivalis lipopolysaccharide affinity for two casting alloys

With the exception of plaque, the affinity of biologically active bacterial products for restorative materials and the influence of that affinity on periodontal health has not been detailed. This study recognized that Porphyromonas gingivalis endotoxin, which is cell envelope lipopolysaccharide (LPS) produced by a bacterium that is common to the crevicular microbial flora, has an affinity for dental casting alloys. Regardless of surface finish, no difference in LPS initial adherence or elution was recorded between a type III gold or nickel-chromium-beryllium alloy (p > 0.05), but LPS readily adhered and remained attached to both alloys. LPS affinity could contribute to periodontal inflammation in tissues that approximate restorations fabricated from either alloy.

Structural study on the free lipid A isolated from lipopolysaccharide of Porphyromonas gingivalis

The chemical structure of lipid A isolated from Porphyromonas gingivalis lipopolysaccharide was elucidated by compositional analysis, mass spectrometry, and nuclear magnetic resonance spectroscopy. The hydrophilic backbone of free lipid A was found to consisted of beta(1,6)-linked D-glucosamine disaccharide 1-phosphate. (R)-3-Hydroxy-15-methylhexadecanoic acid and (R)-3-hydroxyhexadecanoic acid are attached at positions 2 and 3 of the reducing terminal residue, respectively, and positions 2' and 3' of the nonreducing terminal unit are acylated with (R)-3-O-(hexadecanoyl)-15-methylhexadecanoic acid and (R)-3-hydroxy-13-methyltetradecanoic acid, respectively. The hydroxyl group at position 4' is partially replaced by another phosphate group, and the hydroxyl groups at positions 4 and 6' are unsubstituted. Considerable heterogeneity in the fatty acid chain length and the degree of acylation and phosphorylation was detected by liquid secondary ion-mass spectrometry (LSI-MS). A significant pseudomolecular ion of lipid A at m/z 1,769.6 [M-H]- corresponding to a diphosphorylated GlcN backbone bearing five acyl groups described above was detected in the negative mode of LSI-MS. Predominant ions, however, were observed at m/z 1,434.9 [M-H]- and m/z 1,449.0 [M-H]-, each representing monophosphoryl lipid A lacking (R)-3-hydroxyhexadecanoic and (R)-3-hydroxy-13-methyltetradecanoic acids, respectively. The presence of mono- and diphosphorylated lipid A species was also confirmed by LSI-MS of de-O-acylated lipid A (m/z 955.3 and 1,035.2, respectively).

Revised sequence of the Porphyromonas gingivalis prtT cysteine protease/hemagglutinin gene: homology with streptococcal pyrogenic exotoxin B/streptococcal proteinase

The prtT gene from Porphyromonas gingivalis ATCC 53977 was previously isolated from an Escherichia coli clone possessing trypsinlike protease activity upstream of a region encoding hemagglutinin activity (J. Otogoto and H. Kuramitsu, Infect. Immun. 61;117-123, 1993). Subsequent molecular analysis of this gene has revealed that the PrtT protein is larger than originally reported, encompassing the hemagglutination region. Results of primer extension experiments indicate that the translation start site was originally misidentified. An alternate open reading frame of nearly 2.7 kb, which encodes a protein in the size range of 96 to 99 kDa, was identified. In vitro transcription-translation experiments confirm this size, and Northern (RNA) blot experiments indicate that the protease is translated from a 3.3-kb mRNA. Searching the EMBL protein database revealed that the amino acid sequence of the revised PrtT is similar to sequences of two related proteins from Streptococcus pyogenes. PrtT is 31% identical and 73% similar over 401 amino acids to streptococcal pyrogenic exotoxin B. In addition, it is 36% identical and 74% similar over 244 amino acids with streptococcal proteinase, which is closely related to streptococcal pyrogenic exotoxin B. The similarity is particularly high at the putative active site of streptococcal proteinase, which is similar to the active sites of the family of cysteine proteases. Thus, we conclude that PrtT is a 96- to 99-kDa cysteine protease and hemagglutinin with significant similarity to streptococcal enzymes.

Effect of binding of fibrinogen to each bacterium on coaggregation between Porphyromonas gingivalis and Streptococcus oralis

Fibrinogen inhibits the coaggregation between Porphyromonas gingivalis and Streptococcus oralis. In this study, we determined which bacterium interacts with fibrinogen in this inhibitory process. Although preincubation of each bacterium with fibrinogen did not inhibit coaggregation, its activity was completely eliminated by the addition of protease inhibitors such as N-ethylmaleimide (NEM), p-chloromercuriphenyl sulfonate and N alpha-p-tosyl-L-lysine chloromethyl ketone to the preincubation mixture with fibrinogen and P. gingivalis. However, the inhibition of coaggregation was not found after preincubation of S. oralis with fibrinogen in the presence or absence of the protease inhibitors. Labelled materials were recovered from the extract of P. gingivalis cells incubated with radioiodinated fibrinogen in the presence of NEM but not in the absence of NEM. In the binding experiment, P. gingivalis showed a much higher binding activity to fibrinogen than S. oralis. These findings suggest that fibrinogen and its fragment(s) may mask directly or indirectly the aggregation site with S. oralis on the P. gingivalis cells in its inhibitory process of coaggregation.

The influence of supragingival plaque control on clinical and microbial outcomes following the use of antibiotics for the treatment of periodontitis

Although supragingival plaque control is essential to successful periodontal therapy, the role of plaque control following systemic antibiotic use in periodontal disease has not been well defined. This study evaluated, following antibiotic use, which clinical and microbial parameters appeared to be influenced primarily by the antibiotics, independent of plaque control, and which outcomes appeared to be dependent on plaque control. Two hundred thirty-six patients (236) with moderate to severe periodontitis were clinically evaluated and microbial samples were taken by their private-practice periodontists. All patients were treated with scaling and root planing and a variety of systemic antibiotics, which were selected based on the microbial and clinical profile of the patient. Three months after therapy, patients were reevaluated and grouped by post-treatment plaque control, as either having very good oral hygiene (LoPl: N = 143; < or = 10% plaque-covered surfaces) or poor oral hygiene (HiPl: N = 93; > or = 25% plaque-covered surfaces). The two groups had different plaque and bleeding scores initially, but similar numbers of pockets probing > 5 mm and similar microbial patterns. Although the LoPl group had a significantly greater reduction in plaque than the HiPl group, bleeding scores and probing depths changed comparably in both groups after antibiotic therapy. Plaque control influenced outcomes significantly, but in a complex manner. The LoPl group exhibited a significantly greater reduction in certain bacteria, for example P. gingivalis. Interactions between plaque control and specific microbial parameters significantly affected clinical outcomes, although neither alone was sufficient to predict outcomes following antibiotic therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Salivary receptors for recombinant fimbrillin of Porphyromonas gingivalis

Fimbriae are considered important in the adherence and colonization of Porphyromonas gingivalis in the oral cavity. It has been demonstrated that purified fimbriae bind to whole human saliva adsorbed to hydroxyapatite (HAP) beads, and the binding appears to be mediated by specific protein-protein interactions. Recently, we expressed the recombinant fimbrillin protein (r-Fim) of P. gingivalis corresponding to amino acid residues 10 to 337 of the native fimbrillin (A. Sharma, H.T. Sojar, J.-Y. Lee, and R.J. Genco, Infect. Immun. 61:3570-3573, 1993). We examined the ability of individual salivary components to promote the direct attachment of r-Fim to HAP beads. Purified r-Fim was radiolabeled with 125I and incubated with HAP beads which were coated with saliva or purified individual salivary components. Whole, parotid, and submandibular-sublingual salivas increased the binding of 125I-r-Fim to HAP beads. Submandibular-sublingual saliva was most effective in increasing the binding of 125I-r-Fim to HAP beads (1.8 times greater than that to uncoated HAP beads). The binding of 125I-r-Fim to HAP beads coated with acidic proline-rich protein 1 (PRP1) or statherin was four and two times greater, respectively, than that to uncoated HAP beads. PRP1 and statherin molecules were also found to bind 125I-r-Fim in an overlay assay. The binding of intact P. gingivalis cells to HAP beads coated with PRP1 or statherin was also enhanced, by 5.4 and 4.3 times, respectively, over that to uncoated HAP beads. The interactions of PRP1 and statherin with 125I-r-Fim were not inhibited by the addition of carbohydrates or amino acids. PRP1 and statherin in solution did not show inhibitory activity on 125I-r-Fim binding to HAP beads coated with PRP1 or statherin. These results suggest that P. gingivalis fimbriae bind strongly through protein-protein interactions to acidic proline-rich protein and statherin molecules which coat surfaces.

Host-related genotypic heterogeneity of Porphyromonas gingivalis strains in the beagle dog

The present investigation explored the genotypic heterogeneity of Porphyromonas gingivalis using restriction endonuclease analysis and ribotyping of 64 P. gingivalis isolates, recovered from the periodontal pockets of 3 beagle dogs, 2 of which were reared together. The isolates originated from both healthy and periodontal disease affected sites and thereby enabled the study of bacterial genotype with respect to (i) individual host, (ii) ecological niche (site within host) and (iii) level of periodontal health. Whole genomic DNA was extracted from each isolate and digested by the restriction endonuclease KpnI. Digestion fragments were separated by electrophoresis and transferred onto nylon membranes. The blots were hybridized with a digoxigenin-labeled 16S rDNA probe, and hybridization bands were detected using an anti-digoxigenin antibody conjugated with alkaline phosphatase and enhanced chemiluminescence. Fourteen genomic fingerprints and 13 ribotypes were observed among the 64 isolates. As many as 8 distinct fingerprints were detected within a single host and up to 4 fingerprints within a single periodontal pocket. The dogs reared together shared 2 common clonal types but also exhibited clonal types unique to each dog. No clear association between clonal type and periodontal health status could be made. The results revealed an extensive intra-host genotypic heterogeneity of P. gingivalis strains in the beagle dog and indicated that ribotyping was a sensitive method for differentiating clonal types within species.

Coaggregation between Porphyromonas gingivalis and mutans streptococci

Coaggregation occurred between Porphyromonas gingivalis and mutans streptococci. The coaggregation was completely inhibited by L-arginine, N alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK), and a trypsin inhibitor, and weakly inhibited by L-lysine, N-ethylmaleimide, lysozyme, and human whole saliva. The results of heat and proteinase K treatment suggested that a heat-labile proteinaceous substance of P. gingivalis and a heat-stable substance of mutans streptococci may play a role in the coaggregation. Mutans streptococci also aggregated in the presence of the heat-labile factor in the supernatant of P. gingivalis. The aggregation was also inhibited by L-arginine, TLCK, and a trypsin inhibitor.

Construction and characterization of a fimA mutant of Porphyromonas gingivalis

Although fimbriae of Porphyromonas gingivalis have been implicated as playing a major role in adherence to gingival tissue surfaces, no conclusive genetic evidence has yet been obtained. The fimA gene, the determinant for the major fimbrial subunit protein, was cloned and sequenced (D. P. Dickinson, M. A. Kubiniec, F. Yoshimura, and R. J. Genco, J. Bacteriol. 170:1658-1665, 1988). We undertook to inactivate the fimA gene by a homologous recombination technique and examined the fimA mutant for changes in surface properties, including production of fimbriae, adherence to human gingival fibroblasts and epithelial cells, hemagglutinating activity, and surface hydrophobicity. To inactivate the fimA gene, we disrupted a fimA clone by insertion of a DNA segment containing an erythromycin resistance (Emr) gene. This was then delivered into P. gingivalis ATCC 33277 from an Escherichia coli K-12 strain, SM10 lambda pir, by using a mobilizable suicide vector, pGP704; recombination at the fimA locus led to the isolation of a fimA mutant. Disruption of the fimA locus and disappearance of FimA production were confirmed by Southern hybridization with a fimA-specific DNA probe and Western immunoblotting with a monoclonal antibody against the FimA protein, respectively. The fimA mutant constructed failed to express long (0.5- to 1.0-micron) fimbriae from the bacterial surface and had a diminished adhesive capacity to tissue-cultured human gingival fibroblasts and epithelial cells. Observation of the bacteria adhering to human gingival fibroblasts by scanning electron microscopy revealed that the wild-type strain had dramatic local changes in the appearance of the microvilli at the point of contact with large bacterial clumps, whereas the fimA mutant did not. In contrast, neither the hemagglutinating activity nor the surface hydrophobicity was changed in the fimA mutant. These data thus constitute the first direct genetic evidence demonstrating that the FimA protein of P. gingivalis is essential for the interaction of the organism with human gingival tissue cells through a function(s) encoded by the fimA gene.

Relationship between salivary blood group antigens, microbial flora and periodontal condition in young adults

To investigate a possible rôle for salivary blood-group antigens in the relative frequencies of selected periodontal pathogens and commensal oral micro-organisms, we studied the clinical and microbiological condition in young adults with or without blood group reactive substances in saliva (secretors or non-secretors respectively). Clinical measurements were recorded at the Ramfjord teeth in 81 1st-year dental students. In addition, presence of interproximal loss of attachment (LA) was assessed at sites with a pocket depth of > or = 4 mm. Microbiological samples were taken from one of the Ramfjord teeth (site without interproximal LA), from interproximal sites of > or = 4 mm in conjunction with LA, and from the saliva. The samples were analyzed for the presence of Actinomyces naeslundii, Actinomyces viscosus, Campylobacter rectus, Fusobacterium nucleatum, Peptostreptococcus micros, Prevotella intermedia, Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans. Clinically, no statistically significant differences were found in the periodontal status between secretors (78% of our population) and non-secretors. Furthermore, the occurrence of the monitored micro-organisms was not correlated to the secretor status. It is concluded that bacterial colonization with the micro-organisms tested in this study, apparently occurred independent of secretor status. Among the periodontal pathogens, only P. intermedia was more frequently recovered from the saliva of subjects with interproximal LA (49%) than in those without (33%; p = 0.03). This finding was irrespective of the secretor status. Therefore, P. intermedia may be an important micro-organism in relation to the onset of periodontal destruction in young adults.

Inactivation of the Porphyromonas gingivalis fimA gene blocks periodontal damage in gnotobiotic rats

Fimbrial production by Porphyromonas gingivalis was inactivated by insertion-duplication mutagenesis, using the cloned gene for the P. gingivalis major fimbrial subunit protein, fimA. by several criteria, this insertion mutation rendered P. gingivalis unable to produce fimbrilin or an intact fimbrial structure. A nonfimbriated mutant, DPG3, hemagglutinated sheep erythrocytes normally and was unimpaired in the ability to coaggregate with Streptococcus gordonii G9B. The cell surface hydrophobicity of DPG3 was also unaffected by the loss of fimbriae. However, DPG3 was significantly less able to bind to saliva-coated hydroxyapatite than wild-type P. gingivalis 381. This suggested that P. gingivalis fimbriae are important for adherence of the organism to saliva-coated oral surfaces. Further, DPG3 was significantly less able to cause periodontal bone loss in a gnotobiotic rat model of periodontal disease. These observations are consistent with other data suggesting that P. gingivalis fimbriae play an important role in the pathogenesis of human periodontal disease.

Inhibition of coaggregation between Porphyromonas gingivalis and Streptococcus oralis by fibrinogen fragments

The localization of regions of fibrinogen that inhibit coaggregation between Porphyromonas gingivalis and Streptococcus oralis was investigated. The coaggregation was inhibited by A alpha and gamma chains, but not by B beta chain. The inhibitory activity of fragment D was more potent than that of fragment E. Some cyanogen bromide-treated fragments isolated from A alpha and gamma chains including the NH2-terminal 148-207 amino acid residues of A alpha chain (A alpha 148-207) and gamma 1-78 showed inhibitory activities. A alpha 148-207 was further digested with lysyl endopeptidase. A alpha 158-176 and A alpha 192-206 which contained four and two arginine residues, respectively, retained the inhibitory activities. When the arginine residues of these two peptides were modified by phenylglyoxal, the inhibitory activities were much reduced. These findings suggest that the arginine residues of some specific regions of fibrinogen may play an important role in the inhibition of the coaggregation.

Involvement of Porphyromonas gingivalis fimbriae in adherence to Streptococcus gordonii

Adherence of Porphyromonas gingivalis to early plaque bacteria, such as Streptococcus gordonii, is considered an important colonization mechanism. The molecules that mediate this interspecies binding have not been determined. Fimbriae were prepared from P. gingivalis 33277 by mild agitation, ammonium sulfate precipitation and DEAE-Sepharose chromatography. In a nitrocellulose blot adherence assay, purified fimbriae inhibited S. gordonii G9B-P. gingivalis 33277 binding by up to 54%. In addition, fimbriae bound to S. gordonii cells in a dot-blot assay. Incubation of fimbriae with S. gordonii cells followed by washing, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), electroblotting and probing with P. gingivalis antibodies also revealed that the fimbriae bind to S. gordonii. In contrast, S. gordonii did not interact with fimbriae that were first subjected to SDS-PAGE and electroblotting or deposited on a nitrocellulose membrane, suggesting that conformational determinants of the fimbriae may be important in binding. The results indicate that binding between P. gingivalis and S. gordonii is mediated, at least in part, by the porphyromonads' fimbriae.

Microbial associations in periodontitis sites before and after treatment

Duplicate samples from 110 periodontal sites of 6 mm or more pocket depth in 16 patients were analyzed for the presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Capnocytophaga spp., Campylobacter rectus, Eikenella corrodens and Fusobacterium nucleatum. The sites were sampled before and after nonsurgical periodontal treatment. No statistically significant associations were found before treatment between any of the analyzed species. After treatment, statistically significant associations were found between E. corrodens and all the other species, F. nucleatum and P. intermedia; Capnocytophaga spp. and C. rectus; P. intermedia vs Capnocytophaga spp. and P. gingivalis; and C. rectus vs Capnocytophaga spp. and A. actinomycetemcomitans. Some of these associations could be explained either by patient-related factors or site-related characteristics such as the pocket depth. The proportion of P. gingivalis seemed to be unrelated to the proportion of P. intermedia in the samples. If one of the analyzed microbes was found in one of the sampled pockets in a patient, the probability of finding that microbe in all the sampled sites in the same patient before treatment was more than 50%. This probability was reduced after treatment for many species, especially P. gingivalis, which showed a probability of zero. The probability of detecting a bacterial species on at least one additional site if it was present on one in the same individual was nearly 100%, both before and after treatment, for all species studied. This study has shown several potential microbial associations in the subgingival plaque flora of deep periodontal pockets.(ABSTRACT TRUNCATED AT 250 WORDS)

Adherence and hydrophobicity of invasive and noninvasive strains of Porphyromonas gingivalis

The adherence of Porphyromonas gingivalis to cell surfaces of periodontal tissues may play an important role in its pathogenicity. In this study, 12 strains of P. gingivalis, including both invasive and noninvasive strains, were investigated for adherence to gingival ligament components. The test strains of P. gingivalis adhered to collagen, fibronectin, and laminin to significantly different degrees. An overall positive correlation was noted between hydrophobicity and the number of cells that attached to collagen coated on hydroxyapatite beads. Invasive strains had low hydrophobicity and bound less to collagen than did noninvasive strains that possessed strong hydrophobic properties. 3H-fimbriae extracted from P. gingivalis were found to attach to collagen-coated hydroxyapatite. The fimbriae extracted from noninvasive strains bound strongly to collagen, whereas invasive strains' fimbriae with low hydrophobicity bound weakly to collagen or saliva-coated hydroxyapatite. These data suggest that 1) fimbriae play an important role in colonization through their hydrophobic activity; 2) fimbriae of noninvasive strains are associated with the major adhesin for attachment to gingival tissue, whereas fimbriae of invasive strains are weakly involved in adherence; and 3) there is no correlation between colonization and the invasiveness of P. gingivalis.

Transmission of Porphyromonas gingivalis between spouses

Porphyromonas gingivalis has been associated with severe forms of periodontitis. The question can be raised about the origin of this suspected periodontal pathogen. The purpose of the present investigation was to study the possibility of transmission of P. gingivalis between spouses. 18 patients were selected with severe periodontitis and colonized with P. gingivalis. 10 of their spouses appeared to be colonized with P. gingivalis too. 8 of the patients and their spouses were investigated further clinically and microbiologically. Microbiological evaluation revealed mostly high %s of P. gingivalis in the pockets, not only of the patients (5-48% of the cultivable flora), but also in 7 of the 8 spouses (0.2-61%). Furthermore, this species was isolated often from the saliva, the tongue, the buccal mucosa and the tonsillar area from both patients and spouses. For typing purposes, bacterial DNA was isolated, treated with the restriction endonucleases Bam HI or Pst I, after which the DNA fragments were separated by agarose gelelectrophoresis. With one exception, each individual was colonized with only one clonal type of P. gingivalis. The DNA patterns of all P. gingivalis isolates from unrelated individuals were found to be distinct. In contrast, in 6 of the 8 couples, the DNA patterns of isolates from husband and wife were indistinguishable. From these data, it can be concluded that it is most likely, that P. gingivalis can be transmitted between spouses. It remains to be investigated whether transmission of P. gingivalis is a risk factor for developing periodontal destruction.

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.

Modulation of intergeneric adhesion of oral bacteria by human saliva

Porphyromonas gingivalis adheres in vitro to biofilms containing Streptococcus and Actinomyces species. On initial entry to the mouth, this interbacterial adhesion may enable P. gingivalis to colonize dental plaque and to avoid clearance by saliva flow. Saliva may also interfere directly with P. gingivalis colonization of dental plaque; a 43-kDa glycoprotein in human submandibular-sublingual saliva binds to P. gingivalis surfaces and diminishes interbacterial adhesion activity. To avoid fouling of its surface by host components, P. gingivalis produces surface-localized proteases that can degrade adsorbed proteins and may serve to unmask bacterial adhesins. Successful management of P. gingivalis colonization might be achieved in the future by devising artificial methods to block its surface adhesins or to prevent bacterial proteolysis of native salivary molecules that have protective functions.

Black-pigmented gram-negative anaerobes in endodontic infections

Necrotic dental root canal infections are polymicrobial infections dominated by anaerobic bacteria. The number of different species in one canal is usually low, approx. 4-7 species. The species isolated most frequently belong to the genera Prevotella, Porphyromonas, Fusobacterium, Peptostreptococcus, Eubacterium and Streptococcus. The frequency of isolation of black-pigmented Gram-negative anaerobes in endodontic infections varies from 25% to > 50%. Pr. intermedia is the most commonly found pigmented species, followed by Pr. denticola and two Porphyromonas species, P. gingivalis and P. endodontalis. Several studies have shown that P. gingivalis and P. endodontalis are closely related to the presence of acute symptoms in endodontic infections, whereas other black-pigmented Gram-negative anaerobes are not. However, several other species may also be involved in acute infections. Moreover, Porphyromonas species have occasionally been isolated from cases with no symptoms. Although Porphyromonas spp. are clearly related to symptoms at the beginning of therapy, they are not important for the prognosis of the treatment.

Localization of the Fusobacterium nucleatum T18 adhesin activity mediating coaggregation with Porphyromonas gingivalis T22

Adherence of pathogenic bacteria is often an essential first step in the infectious process. The ability of bacteria to adhere to one another, or to coaggregate, may be an important factor in their ability to colonize and function as pathogens in the periodontal pocket. Previously, a strong and specific coaggregation was demonstrated between two putative periodontal pathogens, Fusobacterium nucleatum and Porphyromonas gingivalis. The interaction appeared to be mediated by a protein adhesin on the F. nucleatum cells and a carbohydrate receptor on the P. gingivalis cells. In this investigation, we have localized the adhesin activity of F. nucleatum T18 to the outer membrane on the basis of the ability of F. nucleatum T18 vesicles to coaggregate with whole cells of P. gingivalis T22 and the ability of the outer membrane fraction of F. nucleatum T18 to inhibit coaggregation between whole cells of F. nucleatum T18 and P. gingivalis T22. Proteolytic pretreatment of the F. nucleatum T18 outer membrane fraction resulted in a loss of coaggregation inhibition, confirming the proteinaceous nature of the adhesin. The F. nucleatum T18 outer membrane fraction was found to be enriched for several proteins, including a 42-kDa major outer membrane protein which appeared to be exposed on the bacterial cell surface. Fab fragments prepared from antiserum raised to the 42-kDa outer membrane protein were found to partially but specifically block coaggregation. These data support the conclusion that the 42-kDa major outer membrane protein of F. nucleatum T18 plays a role in mediating coaggregation with P. gingivalis T22.

Correlation between cell-adherent activity and surface structure in Porphyromonas gingivalis

The cell-adherent ability of 6 strains of Porphyromonas gingivalis (381, ATCC 33277, SU63, KD1, W50 and W83) was compared by using radiolabeled bacterial cells and human gingival fibroblasts (Gin 1), human periodontal ligament fibroblasts (HPLF) and human epithelial cells (Ca9-22) that had been grown on collagen beads. The cell-adherent activity of these organisms varied among strains; P. gingivalis strains 381, ATCC 33277 and SU63 bound to the target cells at a range of 14% to 72%, but the other 3 strains (KD1, W50 and W83) were scarcely bound (0.6% to 3.5%). On the other hand, whole bacterial cells and culture supernatants of all strains showed distinct hemagglutinating activity. The 3 strains showing high cell-adherent activity were hydrophobic and the other strains showing less activity were relatively hydrophilic. Furthermore, a number of peritrichous fimbriae were found on the surface of P. gingivalis strains 381, ATCC 33277 and SU63, which showed high adherent activity, whereas, fimbriae on the other 3 strains showing low adherent ability were barely apparent. Therefore, it was assumed that the cell-adherent activity of P. gingivalis was related to the hydrophobicity of the cell surface, which was related to the number of fimbriae.

Eikenella corrodens in human oral and non-oral infections: a review

There is substantial evidence in support of the existence of distinct clinical forms of human periodontal disease. Moreover, these different forms of periodontal disease may be associated with relatively distinct subgingival microflora, often involving microaerophilic or anaerobic Gram-negative bacterial species. Eikenella corrodens is a facultative Gram-negative bacillus which is a common inhabitant of the oral cavity and the intestinal and genital tracts. Its primary ecologic niche within the oral cavity appears to be dental plaque, both in periodontally healthy individuals and in periodontitis patients. However, E. corrodens is recognized as an infrequent human pathogen capable of causing extraoral infections, either as the sole infectious agent or as part of a mixed infection, its potential role in the etiology of periodontal disease is not well understood. E. corrodens is often present in the supra- and subgingival plaque of periodontally healthy subjects. On the basis of cross-sectional and longitudinal studies, E. corrodens appears to be somewhat more prevalent in subgingival plaque samples of periodontitis subjects than periodontally healthy individuals. However, the percentage of E. corrodens in the total cultivable microflora did not vary between the two groups. Microbiologic studies attempting to define the relationship between E. corrodens and periodontal disease assume that this species is essentially homogeneous and that all strains exhibit comparable pathogenic potential. However, E. corrodens exhibits 1) variable colony morphology, biochemical and serologic reactivity; 2) marked phenotypic diversity with respect to outer membrane protein and lipopolysaccharide structure; and 3) marked diversity in the restriction patterns of total genomic DNA. Thus, it is possible that a limited number of clones of E. corrodens may be associated with periodontal disease and/or extraoral infection, while other strains are relatively harmless commensals. Additional studies, possibly employing strain-specific nucleic acid probes, may be required to define the role of E. corrodens as a human periodontal pathogen.

The effect of supragingival plaque control on the composition of the subgingival flora in periodontal pockets

The effect of mechanical supragingival plaque control on the composition of the subgingival microflora in untreated 4-6 mm deep periodontal pockets was investigated. 13 subjects with chronic periodontitis were recruited for the study. Periodontally-diseased sites were subjected to professional plaque control 3 x weekly for a period of 3 weeks. Contralateral sites received no prophylaxis and served as controls. No instructions in oral hygiene procedures were given to the patients who maintained their habitual oral hygiene regime during the observation period. Clinical examination and darkfield microscopic analysis of bacterial samples were performed every week. The PlI scores for the experimental sites were reduced markedly, while those for the control sites remained stable throughout the observation period. No changes in the other clinical parameters were detected during the study. The composition of the subgingival microflora at the control sites did not change during the experimental period. In contrast, at the test sites, the proportion of spirochetes+motile rods decreased continuously. This decrease reached statistical significance at the end of the experiment. The results indicate that at periodontally diseased sites with an established subgingival ecosystem, supragingival plaque removal may influence the composition of the subgingival microflora.

Encapsulation and pilus formation of Bacteroides spp. in normal flora abscesses and blood

The presence of encapsulated and piliated Bacteroides spp. (mostly Bacteroides fragilis and melaninogenicus groups was investigated in isolates from blood, abscesses and normal flora. Of the strains of Bacteroides spp. isolated 45 of 54 (83%) recovered from blood and 31 of 40 (78%) found in abscesses were encapsulated. In contrast, only seven of 71 (10%) similar strains isolated from the faeces or pharynx of healthy persons were encapsulated (P < 0.001). Pili were observed in three of 54 (6%) of strains isolated from blood, 30 of 40 (75%) of those recovered from abscesses (P < 0.001), and 49 of 71 (69%) of those found in normal flora (P < 0.001). The predominance of encapsulated forms in all strains of B. fragilis and B. melaninogenicus in blood as well as in abscesses suggests an increased virulence of these compared with non-encapsulated isolates. In contrast, the presence of pili in Bacteroides spp. recovered mostly from abscesses and normal flora suggests that this structure may play a role in the ability of these organisms to adhere to mucous membranes and may interfere with their ability to spread systemically. These findings illustrate the morphological differences that may be observed in Bacteroides spp. from various anatomical sites.

Role of Porphyromonas gingivalis 40-kDa outer membrane protein in the aggregation of P. gingivalis vesicles and Actinomyces viscosus

Porphyromonas gingivalis, an important pathogen in periodontitis, produces extracellular vesicles that aggregate with Actinomyces viscosus cells. A 40-kDa outer membrane protein (OMP)-coding gene from P. gingivalis was cloned and the protein was found to be localized in these vesicles. The recombinant 40-kDa OMP did not show aggregation activity. However, affinity-purified antibody against the recombinant protein significantly inhibited aggregation of P. gingivalis vesicles with A. viscosus cells. The antibody also inhibited cellular coaggregation of several strains of P. gingivalis with A. viscosus cells, but not with other periodontal pathogens. Moreover, aggregation of A. viscosus cells with P. gingivalis vesicles was inhibited in a dose-dependent manner by pre-treatment of the A. viscosus cells with the recombinant protein. These findings suggest that the 40-kDa OMP may be an important aggregation factor of P. gingivalis.

Inhibition of Actinomyces viscosus--Porphyromonas gingivalis coadhesion by trypsin and other proteins

Protease activity is associated with the coadhesion of Actinomyces viscosus and Porphyromonas gingivalis. To try to distinguish whether the recognition/adhesion or degradative functions of proteases are more crucial for coadhesion, we determined the effect of trypsin and other purchased proteases and proteins on coadhesion when they were incorporated in the coadhesion assay buffer or when A. viscosus cells were pretreated with trypsin. Coadhesion was measured by the decrease in turbidity caused by the absorption of A. viscosus cells from aqueous suspension by P. gingivalis-coated hexadecane droplets. Pretreatment of A. viscosus with trypsin had no obvious effect on the kinetics of coadhesion. Likewise, trypsinization of A. viscosus failed to aid or enhance coaggregation by chemically induced, trypsin activity-deficient mutants of B. gingivalis. In contrast, incorporating trypsin in the buffer during the coadhesion assay yielded a concentration-dependent inhibition of coadhesion greater than the inhibition found with the same concentration of other proteases. Coadhesion was also impaired to a greater extent by similar wt/vol concentrations of nonproteolytic proteins (bovine serum albumin (BSA), defatted BSA, gelatin, and casein), by antisera against whole P. gingivalis cells and fimbriae, by preimmune serum, and by the amino acid arginine but not lysine. These findings suggest that the role of proteases in coadhesion is not solely to enzymatically "prime" A. viscosus for more avid coadhesion and that their role as potential protein or peptide seeking adhesins should be considered.

Salivary receptors for GalNAc beta-sensitive adherence of Actinomyces spp.: evidence for heterogeneous GalNAc beta and proline-rich protein receptor properties

The receptors for GalNAc beta 1-3Gal alpha Oethyl (GalNAc beta)-sensitive adherence of Actinomyces strains to salivary pellicles were investigated. Parotid and submaxillary saliva from one individual was size fractionated and utilized in hydroxyapatite adherence assays with Actinomyces naeslundii 12104 and A. viscosus 19246 and LY7 with and without GalNAc beta. Three parotid salivary fractions, the high-molecular-weight, acidic proline-rich protein (PRP), and statherin fractions, promote GalNAc beta-sensitive adherence of strain 12104, whereas only the high-molecular-weight fraction of submaxillary saliva promotes such adherence. In contrast, strain LY7, possessing a variant GalNAc beta specificity, shows GalNAc beta-sensitive adherence to the leading and trailing regions of the submaxillary PRP fractions but less distinct adherence to the parotid and submaxillary high-molecular-weight fractions. In addition, the PRP and statherin fractions promote adherence of strains LY7 and 19246 that is not inhibited by GalNAc beta. However, whereas strain LY7 binds more strongly to the PRP fraction than to the statherin fraction, strain 19246 binds preferentially to the statherin fractions of parotid and submaxillary saliva. These salivary protein fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunostained to detect glycosylated proteins. The different salivary receptor properties are paralleled by different glycosylation patterns. The variable GalNAc beta specificities may have evolved to match different salivary glycosylation patterns, and PRP and statherin binding properties seem to be heterogeneous among the Actinomyces strains.

Characterization of the adherence of Porphyromonas gingivalis to oral streptococci

Adherence of Porphyromonas gingivalis to strains of Streptococcus sanguis and Streptococcus mitis deposited on nitrocellulose paper was investigated. A variety of laboratory strains and clinical isolates of P. gingivalis bound to both S. sanguis and S. mitis. Binding of P. gingivalis to all but one of the streptococci was not inhibited by salivary molecules. Pretreatment of P. gingivalis with periodate and pretreatment of S. sanguis and S. mitis with pronase decreased binding, suggesting that adherence may be mediated by a protein on the streptococci interacting with a carbohydrate on P. gingivalis. Binding was not inhibited by a selection of simple sugars. The ability to adhere to early plaque bacteria such as S. sanguis and S. mitis may be important in the colonization of the mouth by P. gingivalis.

Correlation of haemagglutination activity with trypsin-like protease activity of Porphyromonas gingivalis

Porphyromonas gingivalis is a Gram-negative anaerobic bacterium associated with various forms of periodontal disease. Several characteristics of P. gingivalis are thought to contribute to its pathogenicity; these include haemagglutination and trypsin-like protease activity. Previous studies suggest an association between haemagglutination and trypsin-like protease activity of P. gingivalis. To investigate this, two complementary quantitative experimental approaches were taken. Five independent mutants of P. gingivalis deficient in trypsin-like protease activity were shown to exhibit reduced haemagglutination activity. In addition, enhancers (cysteine and dithiothreitol) and inhibitors (N-ethylmaleimide, N-p-tosyl-L-lysine-chloromethyl ketone, and phenylmethylsulphonyl fluoride) of trypsin-like protease activity were shown, respectively, to significantly enhance and inhibit haemagglutination activity of washed, wild-type P. gingivalis cells (p less than 0.05, paired t-test). Statistical analysis indicated a strong correlation between haemagglutination and trypsin-like protease activity (r = 0.85, p less than 0.001, Spearman rank correlation). The effect of the protease enhancers and inhibitors on haemagglutination activity was specific for P. gingivalis, as they did not significantly change the haemagglutination activity of Fusobacterium nucleatum. These results suggest that the proteolytic site of the trypsin-like protease participates in haemagglutination activity of P. gingivalis.

Inhibition of Porphyromonas gingivalis adhesion to Streptococcus gordonii by human submandibular-sublingual saliva

Porphyromonas gingivalis W50 adheres in vitro to biofilms of Streptococcus gordonii G9B. This phenomenon is believed to facilitate the initial colonization of the oral cavity by P. gingivalis and to contribute to the maturation of dental plaque. In this report, we describe the modulating effects of human submandibular-sublingual saliva (HSMSL) on this in vitro model of intergeneric bacterial adhesion (coaggregation). HSMSL inhibited P. gingivalis adhesion to S. gordonii by 50% at a concentration of 57 micrograms of protein per ml. Maximum inhibitory activity was associated with a 43-kDa protein obtained by sequential Sephadex G200 gel filtration and CM52 ion-exchange chromatography of HSMSL. Pools of other column fractions of HSMSL showed no effect or were slightly stimulatory for bacterial adhesion. The binding of radioiodinated column fractions containing the 43-kDa protein by P. gingivalis was accompanied by their rapid enzymatic degradation. Treating P. gingivalis at 60 degrees C for 30 min or with protease inhibitors (phenylmethylsulfonyl fluoride and sodium iodoacetate) reduced adherence to streptococcal biofilms. These treatments did not prevent P. gingivalis from binding soluble HSMSL saliva components, although subsequent proteolysis was nearly eliminated. These observations indicate that surface-associated proteases of P. gingivalis, either independently or in concert with adjacent surface adhesins, interact with surfaces of oral streptococci to facilitate interbacterial adhesion. The adhesion-blocking properties of HSMSL, particularly the 43-kDa protein, may represent an important host defense mechanism in the oral cavity.

Physicochemical and structural investigation of the surfaces of some anaerobic subgingival bacteria

The surfaces of nine clinical isolates of Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans, and Peptostreptococcus micros and that of laboratory strain P. gingivalis W83 were studied by using contact angle measurements, X-ray photoelectron spectroscopy, infrared spectroscopy, microelectrophoresis of whole cells, and transmission electron microscopy of whole and sectioned cells. P. intermedia strains were hydrophilic, as judged from their small water contact angles, and had highly negative zeta potentials, consistent with the presence of a prominent ruthenium red (RR)-staining layer and fibrillar appendages which are probably partly carbohydrate. The two clinical isolates of P. gingivalis were also hydrophilic and highly negatively charged despite the presence of prominent fibrils, which usually yield less negative zeta potentials. This finding suggests that the RR-staining layer dominates the suspension characteristics of P. gingivalis and P. intermedia strains. P. gingivalis W83 had no demonstrable fibrils and a morphologically distinct RR-staining layer, and it was more hydrophobic than the two clinical isolates of P. gingivalis. P. micros isolates were hydrophobic and much less negatively charged than the other species. The A. actinomycetemcomitans strains displayed long, prominent fibrils and a very thin RR-staining layer, which resulted in high hydrophobicity but distinctly different zeta potentials for the two. Physicochemical data on microbial cell surfaces usually have clear and predictable relationships with each other. For the strains in this study that did not follow these relationships, their aberrant behavior could be explained as due to a masking effect caused by specific surface architecture. We conclude that this combined analysis provides a detailed image of subgingival bacterial surface architecture.

Influence of diet and spiramycin on Actinomyces viscosus-associated experimental periodontitis

The effect of two diets, with and without the antibiotic spiramycin, on Actinomyces viscosus-induced experimental periodontitis was studied in albino hamsters. Severe periodontitis and root caries developed in A. viscosus-infected hamsters fed a high sucrose diet. Hamsters heavily infected with A. viscosus but fed a finely powdered laboratory chow comprised of whole grains and oats formed discrete marginal plaques, but did not develop periodontitis. A. viscosus was not recovered from the plaque microflora of animals receiving spiramycin, and periodontal pathosis did not occur. These findings suggest that dietobacterial interactions and spiramycin may influence initiation of A. viscosus-associated periodontitis in albino hamsters.