The importance of fimbriae in the virulence and ecology of some oral bacteria

Adsorption of components of the plasma kinin-forming system on the surface of Porphyromonas gingivalis involves gingipains as the major docking platforms

Enhanced production of proinflammatory bradykinin-related peptides, the kinins, has been suggested to contribute to the pathogenesis of periodontitis, a common inflammatory disease of human gingival tissues. In this report, we describe a plausible mechanism of activation of the kinin-generating system, also known as the contact system or kininogen-kallikrein-kinin system, by the adsorption of its plasma-derived components such as high-molecular-mass kininogen (HK), prekallikrein (PK), and Hageman factor (FXII) to the cell surface of periodontal pathogen Porphyromonas gingivalis. The adsorption characteristics of mutant strains deficient in selected proteins of the cell envelope suggested that the surface-associated cysteine proteinases, gingipains, bearing hemagglutinin/adhesin domains (RgpA and Kgp) serve as the major platforms for HK and FXII adhesion. These interactions were confirmed by direct binding tests using microplate-immobilized gingipains and biotinylated contact factors. Other bacterial cell surface components such as fimbriae and lipopolysaccharide were also found to contribute to the binding of contact factors, particularly PK. Analysis of kinin release in plasma upon contact with P. gingivalis showed that the bacterial surface-dependent mechanism is complementary to the previously described kinin generation system dependent on HK and PK proteolytic activation by the gingipains. We also found that several P. gingivalis clinical isolates differed in the relative significance of these two mechanisms of kinin production. Taken together, these data show the importance of this specific type of bacterial surface-host homeostatic system interaction in periodontal infections.

A streptococcal effector protein that inhibits Porphyromonas gingivalis biofilm development

Dental plaque formation is a developmental process involving cooperation and competition within a diverse microbial community, approximately 70 % of which is composed of an array of streptococci during the early stages of supragingival plaque formation. In this study, 79 cell-free culture supernatants from a variety of oral streptococci were screened to identify extracellular compounds that inhibit biofilm formation by the oral anaerobe Porphyromonas gingivalis strain 381. The majority of the streptococcal supernatants (61 isolates) resulted in lysis of P. gingivalis cells, and some (17 isolates) had no effect on cell viability, growth or biofilm formation. One strain, however, produced a supernatant that abolished biofilm formation without affecting growth rate. Analysis of this activity led to the discovery that a 48 kDa protein was responsible for the inhibition. Protein sequence identification and enzyme activity assays identified the effector protein as an arginine deiminase. To identify the mechanism(s) by which this protein inhibits biofilm formation, we began by examining the expression levels of genes encoding fimbrial subunits; surface structures known to be involved in biofilm development. Quantitative RT-PCR analysis revealed that exposure of P. gingivalis cells to this protein for 1 h resulted in the downregulation of genes encoding proteins that are the major subunits of two distinct types of thin, single-stranded fimbriae (fimA and mfa1). Furthermore, this downregulation occurred in the absence of arginine deiminase enzymic activity. Hence, our data indicate that P. gingivalis can sense this extracellular protein, produced by an oral streptococcus (Streptococcus intermedius), and respond by downregulating expression of cell-surface appendages required for attachment and biofilm development.

Identification of horizontal gene transfer and recombination of PsaA gene in streptococcus mitis group

Pneumococcal surface adhesin A (psaA) gene is universally confirmed as one of the Streptococcus pneumoniae adhesion genes, but it is disputed whether the psaA gene is a Streptococcus pneumoniae species-specific gene. In the present study, the presence of the psaA gene in 34 streptococcus mitis group isolates was identified by the PCR approach and a comparison of sequencing PCR products (Streptococcus pneumoniae R6 as the control strain). Also, the evolutionary scenarios of these psaA genes in these streptococcus mitis group isolates were analyzed by a phylogenetic tree based on the housekeeping genes (sodA and rnpB) and psaA genes. As a result, a high degree of conservation of open reading frame sequences in all six Streptococcus pneumoniae strains (100% similarity) and in the other species of the streptococcus mitis group (92.6-100% similarity) was revealed. Further genetics research based on housekeeping genes and psaA gene phylogenies showed that the psaA gene was of vertical inheritance only in Streptococcus pneumoniae; however, high-frequency horizontal psaA gene transfer and recombination occurred in the other species of the streptococcus mitis group. These findings confirmed that the psaA gene was not a Streptococcus pneumoniae species-specific gene, and high-frequency HGT and recombination events may explain the presence of the psaA gene in the other species of the streptococcus mitis group.

Distribution of Porphyromonas gingivalis fimA genotypes in primary endodontic infections

OBJECTIVE

Long fimbriae (FimA) are important virulence factors of Porphyromonas gingivalis. Based on the diversity of the fimA gene, this species is classified into 6 genotypes. This study surveyed samples from primary endodontic infections for the presence of these P. gingivalis fimA variants.

STUDY DESIGN

Genomic DNA isolated from samples taken from 25 root canals of teeth with chronic apical periodontitis and 25 aspirates from acute apical abscess was used as template in polymerase chain reaction (PCR) assays directed toward the detection of the different P. gingivalis fimA genotypes.

RESULTS

Porphyromonas gingivalis was detected by a 16S rRNA gene-based PCR in 36% of the total number of cases sampled (44% of chronic apical periodontitis and 28% of abscess aspirates). In cases of chronic apical periodontitis, P. gingivalis variant type IV was the most prevalent (24%), followed by types I (20%), II (16%), and III (8%). In acute abscess samples, variant type II was the most prevalent (12%), followed by types III and IV (8% of each) and type I (4%). Combinations of up to 3 different genotypes were detected in a few cases. No single fimA genotype variant or combination thereof was significantly associated with symptoms. Overall, fimA types IV (16%), II (14%), and I (12%) were the most prevalent.

CONCLUSIONS

Findings demonstrated that different P. gingivalis fimA genotypes can be present in primary endodontic infections.

Tobacco upregulates P. gingivalis fimbrial proteins which induce TLR2 hyposensitivity

BACKGROUND

Tobacco smokers are more susceptible to periodontitis than non-smokers but exhibit reduced signs of clinical inflammation. The underlying mechanisms are unknown. We have previously shown that cigarette smoke extract (CSE) represents an environmental stress to which P. gingivalis adapts by altering the expression of several virulence factors - including major and minor fimbrial antigens (FimA and Mfa1, respectively) and capsule - concomitant with a reduced pro-inflammatory potential of intact P. gingivalis.

METHODOLOGY/PRINCIPAL FINDINGS

We hypothesized that CSE-regulation of capsule and fimbrial genes is reflected at the ultrastructural and functional levels, alters the nature of host-pathogen interactions, and contributes to the reduced pro- inflammatory potential of smoke exposed P. gingivalis. CSE induced ultrastructural alterations were determined by electron microscopy, confirmed by Western blot and physiological consequences studied in open-flow biofilms. Inflammatory profiling of specific CSE-dysregulated proteins, rFimA and rMfa1, was determined by quantifying cytokine induction in primary human innate and OBA-9 cells. CSE up-regulates P. gingivalis FimA at the protein level, suppresses the production of capsular polysaccharides at the ultrastructural level, and creates conditions that promote biofilm formation. We further show that while FimA is recognized by TLR2/6, it has only minimal inflammatory activity in several cell types. Furthermore, FimA stimulation chronically abrogates the pro-inflammatory response to subsequent TLR2 stimulation by other TLR-2-specific agonists (Pam3CSK4, FSL, Mfa1) in an IkappaBalpha- and IRAK-1-dependent manner.

CONCLUSIONS/SIGNIFICANCE

These studies provide some of the first information to explain, mechanistically, how tobacco smoke changes the P. gingivalis phenotype in a manner likely to promote P. gingivalis colonization and infection while simultaneously reducing the host response to this major mucosal pathogen.

Synthesis and assembly of Porphyromonas gingivalis fimbrial protein in potato tissues

Periodontal disease caused by the gram-negative oral anaerobic bacterium Porphyromonas gingivalis is thought to be initiated by the binding of P. gingivalis fimbrial protein to saliva-coated oral surfaces. To assess whether biologically active fimbrial antigen can be synthesized in edible plants, a cDNA fragment encoding the C-terminal binding portion of P. gingivalis fimbrial protein, fimA (amino acids 266-337), was cloned behind the mannopine synthase promoter in plant expression vector pPCV701. The plasmid was transferred into potato (Solanum tuberosum) leaf cells by Agrobacterium tumefaciens in vivo transformation methods. The fimA cDNA fragment was detected in transformed potato leaf genomic DNA by PCR amplification methods. Further, a novel immunoreactive protein band of ~6.5 kDa was detected in boiled transformed potato tuber extracts by acrylamide gel electrophoresis and immunoblot analysis methods using primary antibodies to fimbrillin, a monomeric P. gingivalis fimbrial subunit. Antibodies generated against native P. gingivalis fimbriae detected a dimeric form of bacterial-synthesized recombinant FimA(266-337) protein. Further, a protein band of ~160 kDa was recognized by anti-FimA antibodies in undenatured transformed tuber extracts, suggesting that oligomeric assembly of plant-synthesized FimA may occur in transformed plant cells. Based on immunoblot analysis, the maximum amount of FimA protein synthesized in transformed potato tuber tissues was approximately 0.03% of total soluble tuber protein. Biosynthesis of immunologically detectable FimA protein and assembly of fimbrial antigen subunits into oligomers in transformed potato tuber tissues demonstrate the feasibility of producing native FimA protein in edible plant cells for construction of plant-based oral subunit vaccines against periodontal disease caused by P. gingivalis.

Surface components of Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Research on Porphyromonas gingivalis, a periodontopathogen, has provided a tremendous amount of information over the last 20 years, which may exceed in part than that on other closely related members in terms of phylogenetic as well as proteomic criteria, including Bacteroides fragilis and B. thetaiotaomicron as major anaerobic, opportunistic pathogens in the medical field. In this minireview, we focused on recent research findings concerning surface components such as outer membrane proteins and fimbriae, of P. gingivalis.

MATERIAL AND METHODS

Elucidation of the surface components in P. gingivalis was especially difficult because outer membrane proteins are tightly bound to lipopolysaccharide and they are resistant to dissociation and separation from each other, even during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, unless samples are appropriately heated. In addition, P. gingivalis is asaccharolytic and therefore a potent proteolytic bacterium, another factor causing difficulty in research. The study of the surface components was carefully carried out considering these unique features in P. gingivalis when compared with other gram-negative bacteria, including Escherichia coli and Pseudomonas aeruginosa.

RESULTS

Separation of outer membrane proteins, and characterization of OmpA-like proteins and RagAB as major proteins, is described herein. Our recent findings on FimA and Mfa1 fimbriae, two unique appendages in this organism, and on their regulation of expression are also described briefly.

CONCLUSION

Surface components of P. gingivalis somehow have contact with host tissues and cells because of the outermost cell elements. Therefore, such bacterial components are potentially important in the occurrence of periodontal diseases.

Immunogenicity of a cholera toxin B subunit Porphyromonas gingivalis fimbrial antigen fusion protein expressed in E. coli

The gram-negative anaerobic oral bacterium Porphyromonas gingivalis initiates periodontal disease through fimbrial attachment to saliva-coated oral surfaces. To study the effects of immunomodulation on enhancement of subunit vaccination, the expression in E. coli and immunogenicity of P. gingivalis fimbrial protein (FimA) linked to the C-terminus of the cholera toxin B subunit (CTB) were investigated. Complementary DNAs encoding the P. gingivalis 381 fimbrillin protein sequence FimA1 (amino acid residues 1-200) and FimA2 (amino acid residues 201-337) were cloned into an E. coli expression vector downstream of a cDNA fragment encoding the immunostimulatory CTB. CTB-FimA1 and CTB-FimA2 fusion proteins synthesized in E. coli BL21 (DE3) cells were purified under denaturing conditions by Ni2+-NTA affinity column chromatography. Renaturation of the CTB-FimA1 and CTB-FimA2 fusion proteins, permitted identification of CTB-FimA pentamers and restored CTB binding activity to GM1-ganglioside to provide a biologically active CTB-FimA fusion protein. Mice orally inoculated with purified CTB-FimA1 or CTB-FimA2 fusion proteins generated measurable FimA1 and FimA2 IgG antibody titers, while no serum fimbrial IgG antibodies were detected when mice were inoculated with FimA1 or FimA2 proteins alone. Immunoblot analysis confirmed that sera from mice immunized with CTB linked to FimA1 or FimA2 contained antibodies specific for P. gingivalis fimbrial proteins. In addition, mice immunized with FimA2 or CTB-FimA2 generated measurable intestinal IgA titers indicating the presence of fimbrial antibody class switching. Further, mice orally immunized with CTB-FimA1 generated higher IgA antibody titers than mice inoculated with FimA1 alone. The experimental data show that the immunostimulatory molecule CTB enhances B cell-mediated immunity against linked P. gingivalis FimA fusion proteins, in comparison to immunization with FimA protein alone. Thus, linkage of CTB to P. gingivalis fimbrial antigens can increase subunit vaccine immunogenicity to provide enhanced protection against periodontal disease.

Heterogenic virulence and related factors among clinical isolates of Porphyromonas gingivalis with type II fimbriae

BACKGROUND/AIMS

Porphyromonas gingivalis is a periodontal pathogen whose fimbriae are classified into six genotypes (types I-V and Ib) based on the diversity of the fimA genes encoding the fimbrial subunits. Accumulated evidence suggests that P. gingivalis strains with type II fimbriae are more virulent as compared to those with other types. However, it is unknown if strong virulence is uniformly conserved among clones with type II fimbriae. In the present study, we compared infectious inflammatory changes in clinical isolates of P. gingivalis with type II fimbriae using a mouse abscess model to examine their pathogenic heterogeneity and heterogeneity-related factors.

METHODS

Suspensions of nine different clinical isolates with type II fimbriae were subcutaneously injected into female BALB/c mice and inflammatory parameters, such as serum sialic acid concentration, were compared.

RESULTS

Many of the type II fimbrial isolates caused severe inflammation in the mice, though some were less causative, as was the control strain ATCC 33277 (type I fimbria strain). These results showed that pathogenic heterogeneity exists among P. gingivalis clones with type II fimbriae. Further, the heterogeneity-related factors of P. gingivalis strains were analyzed and the pathogenic potentials showed positive relationships to gingipain activities and invasive efficiency but not to hydrophobicity or autoaggregation. In addition, invasive efficiency was related to the activities of gingipains that were extracellularly secreted.

CONCLUSION

These results suggest that pathogenic heterogeneity has relationships with the invasive and proteolytic activities of P. gingivalis clones with type II fimbriae.

Activity of anti-Porphyromonas gingivalis egg yolk antibody against gingipains in vitro

INTRODUCTION

We investigated the effect of anti-Porphyromonas gingivalis egg yolk antibody against gingipains [immunoglobulin Y (IgY)-GP] on gingipain activity in vitro.

METHODS

IgY-GP was isolated from the yolks of White Leghorn hens immunized with purified gingipains. Control antibody (IgY) was isolated from the yolks of non-immunized hens. Gingipain activity was assessed according to the rate of enzymatic substrate hydrolysis. Human epithelial cells were cultured with or without gingipains and with gingipains pretreated with either IgY-GP or IgY.

RESULTS

Hydrolytic activity decreased in the presence of IgY-GP. Cells incubated with gingipains showed a dose-dependent loss of adhesion activity. Pretreatment of gingipains with IgY-GP was associated with strong inhibition of cell detachment, whereas pretreatment with IgY was not.

CONCLUSION

Our findings suggest that IgY-GP may be an effective immunotherapeutic agent in the treatment of periodontitis.

Involvement of minor components associated with the FimA fimbriae of Porphyromonas gingivalis in adhesive functions

The FimA fimbriae of Porphyromonas gingivalis, the causative agent of periodontitis, have been implicated in various aspects of pathogenicity, such as colonization, adhesion and aggregation. In this study, the four open reading frames (ORF1, ORF2, ORF3 and ORF4) downstream of the fimbrilin gene (fimA) in strain ATCC 33277 were examined. ORF2, ORF3 and ORF4 were demonstrated to encode minor components of the fimbriae and were therefore renamed fimC, fimD and fimE, respectively. Immunoblotting analyses revealed that inactivation of either fimC or fimD by an ermF-ermAM insertion, but not inactivation of ORF1, was accompanied by concomitant loss of the products from the downstream genes, raising the possibility that fimC, fimD and fimE constitute a transcription unit. The fimE mutant produced FimC and FimD, but fimbriae purified from it contained neither protein, suggesting that FimE is required for the assembly of FimC and FimD onto the fimbrilin (FimA) fibre. The fimC, fimD and fimE mutants lost autoaggregation abilities. Fimbriae purified from these three mutants showed attenuated binding activities to glyceraldehyde-3-phosphate dehydrogenase of Streptococcus oralis and to two extracellular matrix proteins, fibronectin and type I collagen. These results suggest that FimE, as well as FimC and FimD, play critical roles in the adhesive activities of the mature FimA fimbriae in P. gingivalis.

fimA genotypes and multilocus sequence types of Porphyromonas gingivalis from patients with periodontitis

Fimbriae are important virulence factors of pathogenic bacteria, facilitating their attachment to host and bacterial cells. In the periodontal pathogen Porphyromonas gingivalis, the fimA gene is classified into six types (genotypes I, Ib, II, III, IV, and V) on the basis of different nucleotide sequences, with fimA genotypes II and IV being prevalent in isolates from patients with periodontitis. The aims of this study were to examine the distribution of fimA genotypes in a collection of 82 P. gingivalis isolates from adult periodontitis patients of worldwide origin and to investigate the relationship between the fimA genotypes and the sequence types (STs), as determined by multilocus sequence typing (MLST), of the isolates. The fimA gene was amplified by PCR with primer sets specific for each genotype. The STs of all strains were assigned according to the MLST database for P. gingivalis (www.pubmlst.org/pgingivalis). The 82 strains showed extensive genetic diversity and were assigned to 69 STs. Only isolates with closely related STs harbored the same fimA genotype. Twenty-eight (34.1%) strains harbored fimA genotype II, while only the reference strain for fimA genotype V reacted with the primers specific for this genotype. Twenty-one isolates (25.6%) were positive by more than one of the fimA PCR assays; the most frequent combinations were genotypes I, Ib, and II (eight isolates) and genotypes I and II (four isolates). Sequencing of the fimA gene from selected isolates did not support the observed specific fimA genotype combinations, suggesting that the genotyping method used for the major fimbriae in P. gingivalis should be reevaluated.

Role of the hemin-binding protein 35 (HBP35) of Porphyromonas gingivalis in coaggregation

Hemin-binding protein 35 (HBP35) in Porphyromonas gingivalis is one of the outer membrane proteins and has been reported to be a non-fimbrial coaggregation factor. In this study, a P. gingivalis HBP35-deficient mutant (MD774) was constructed from wild-type strain FDC381 by insertion mutagenesis in order to provide a better understanding of this protein's role in coaggregation. The intact cells and vesicles in FDC381 were found to have strong aggregation activities with Gram-positive bacteria. But neither the vesicles nor the intact cells showed aggregation activity in MD774. In addition, MD774 reduced autoaggregation activity. Immunoblot analysis of MD774 showed the presence of a non-maturated 45-kDa fimbrillin protein. Electron microscopy showed that the MD774 had no long fimbriae on the cell surface. Arg- and Lys-gingipain activity in MD774 was significantly decreased, compared with FDC381. Real-time RT-PCR demonstrated a significant reduction in the expression of gingipain-associated genes rgpA, rgpB, and kgp. In conclusion, we suggest that the reduction in coaggregation was caused by the combined reduction of a variety of molecules, including HBP35, gingipains, and fimbriae. Our results suggest that the HBP35 protein directly influences not only coaggregation as an adhesion molecule but also indirectly influences the expression of other coaggregation factors.

Maturation of fimbria precursor protein by exogenous gingipains in Porphyromonas gingivalis gingipain-null mutant

Porphyromonas gingivalis expresses several virulence factors such as fimbriae and proteases, termed gingipains, which are enzymes that process precursor fimbriae proteins. Thus, gingipain-null mutants lack mature fimbriae. Membrane vesicle-depleted supernatants (VDS) containing soluble gingipains were prepared as an exogenous gingipain fraction. Precursor proteins were treated with VDS and a fimbriated gingipain-null mutant was successfully generated. Experiments showed that the wild strain adhered to and invaded epithelial cells at a greater level than the fimbriated gingipain-null mutant, while adhesion/invasion was prevented in the presence of fetal calf serum, which inhibits gingipain activity. The findings of this study suggest that gingipains expose cellular cryptic ligands in a proteolytic manner and promote fimbriae binding to epithelial cells.

Indigenous Microflora and Innate Immunity of the Head and Neck

The normal flora of the head and neck exists in a delicate balance within tightly regulated ecologic niches, counterbalanced by a highly efficient innate immune system of the host. Invasion by the normal oral flora is rare when mucosal defenses remain intact. An understanding of the indigenous microflora and the innate mucosal defense mechanisms is necessary for an appropriate evaluation of infections and therapies in this area.

Bacterial pathogenesis and mediators in apical periodontitis

Apical periodontitis is a group of inflammatory diseases caused by microorganisms (mainly bacteria) infecting the necrotic root canal system. The pathogenesis of different types of apical periodontitis and even the same type in different individuals is unlikely to follow a stereotyped fashion with regard to the involved bacterial mediators. Disease pathogenesis is rather complex and involves a multitude of bacteria- and host-related factors. This review article discusses the bacterial pathogenesis of acute and chronic apical periodontitis, with the main focus on the bacterial mediators conceivably involved in the different stages of the infectious process, including secreted products (enzymes, exotoxins, N-formyl-methionyl-leucyl-phenylalanine peptides, heat-shock proteins and metabolic end-products) and structural components (lipopolysaccharide, peptidoglycan, lipoteichoic acid, lipoproteins, fimbriae, flagella, outer membrane proteins and vesicles, DNA, and exopolysaccharides). Knowledge of the bacterial factors involved in the pathogenesis of apical periodontitis is important to the understanding of the disease process and to help establishing proper therapeutic measures to inactivate this bacterial "artillery".

Immunoglobulin G subclass antibody profiles in Porphyromonas gingivalis-associated aggressive and chronic periodontitis patients

BACKGROUND/AIMS

The immunoglobulin G (IgG) antibody response is considered to be protective and beneficial for the control of periodontal lesions. This study analysed IgG subclass antibody levels of Porphyromonas gingivalis in patients with both aggressive periodontitis (AgP) and chronic periodontitis (CP).

METHODS

Subgingival plaque and peripheral blood samples were collected from patients with localized AgP (n = 13), generalized AgP (n = 28) and generalized CP (n = 27) and from 14 periodontally healthy controls. P. gingivalis was identified in subgingival pockets using a polymerase chain reaction. Simultaneously, serum IgG subclass antibody against P. gingivalis whole cells/P. gingivalis fimbriae were measured using enzyme-linked immunosorbent assay.

RESULTS

P. gingivalis was frequently detected in periodontitis patients. Anti-P. gingivalis whole cell IgG1 was elevated in all P. gingivalis-positive patients in the three periodontitis groups. Although increased anti-P. gingivalis IgG1 was also observed in the bacterium-positive healthy controls, the level was lower than that found in the three periodontitis groups. Levels of IgG1, IgG2, IgG3 and IgG4 to P. gingivalis did not differ among bacterium-positive patients in the three periodontitis groups; a significant increase of IgG2 level was not observed in localized AgP. Anti-fimbriae IgG subclass levels of IgG1, IgG2 and IgG4 did not differ among bacterium-positive subjects in all groups, while the anti-fimbriae IgG3 level in generalized CP was significantly higher than that in localized and generalized AgP.

CONCLUSIONS

P. gingivalis infection elicited an IgG subclass antibody response in both periodontitis patients and healthy subjects, while higher anti-P. gingivalis IgG1 levels were found in the three periodontitis groups compared with the healthy control group.

Virulence of Porphyromonas gingivalis is altered by substitution of fimbria gene with different genotype

Porphyromonas gingivalis is a periodontal pathogen whose fimbriae are classified into six genotypes based on the diversity of the fimA genes encoding each fimbria subunit. It was suggested that P. gingivalis strains with type II fimbriae were more virulent than type I strains. For the present study, we generated the mutants in which fimA was substituted with different genotypes to study virulence of type II fimbriae. Using plasmid vectors, fimA of ATCC33277 (type I strain) was substituted with type II fimA, and that of OMZ314 (type II strain) with type I fimA. The substitution of type I fimA with type II enhanced bacterial adhesion/invasion to epithelial cells, whereas substitution with type I fimA resulted in diminished efficiency. Following bacterial invasion, type II clones swiftly degraded cellular paxillin and focal adhesion kinase, and inhibited cellular migration, whereas type I clones and DeltafimA mutants did not. BIAcore analysis demonstrated that type II fimbriae possess greater adhesive abilities for their receptor alpha5beta1-integrin than those of type I. In a mouse abscess model, the type II clones significantly induced serum IL-1beta and IL-6, as well as other infectious symptoms. These results suggest that type II fimbriae are a critical determinant of P. gingivalis virulence.

Enhanced biofilm formation and loss of capsule synthesis: deletion of a putative glycosyltransferase in Porphyromonas gingivalis

Periodontitis is a biofilm-mediated disease. Porphyromonas gingivalis is an obligate anaerobe consistently associated with severe manifestations of this disease. As an opportunistic pathogen, the ability to proliferate within and disseminate from subgingival biofilm (plaque) is central to its virulence. Here, we report the isolation of a P. gingivalis transposon insertion mutant altered in biofilm development and the reconstruction and characterization of this mutation in three different wild-type strains. The mutation responsible for the altered biofilm phenotype was in a gene with high sequence similarity ( approximately 61%) to a glycosyltransferase gene. The gene is located in a region of the chromosome that includes up to 16 genes predicted to be involved in the synthesis and transport of capsular polysaccharide. The phenotype of the reconstructed mutation in all three wild-type backgrounds is that of enhanced biofilm formation. In addition, in strain W83, a strain that is encapsulated, the glycosyltransferase mutation resulted in a loss of capsule. Further experiments showed that the W83 mutant strain was more hydrophobic and exhibited increased auto-aggregation. Our results indicate that we have identified a gene involved in capsular-polysaccharide synthesis in P. gingivalis and that the production of capsule prevented attachment and the initiation of in vitro biofilm formation on polystyrene microtiter plates.

Invasion of epithelial cells and proteolysis of cellular focal adhesion components by distinct types of Porphyromonas gingivalis fimbriae

Porphyromonas gingivalis fimbriae are classified into six types (types I to V and Ib) based on the fimA genes encoding FimA (a subunit of fimbriae), and they play a critical role in bacterial interactions with host tissues. In this study, we compared the efficiencies of P. gingivalis strains with distinct types of fimbriae for invasion of epithelial cells and for degradation of cellular focal adhesion components, paxillin, and focal adhesion kinase (FAK). Six representative strains with the different types of fimbriae were tested, and P. gingivalis with type II fimbriae (type II P. gingivalis) adhered to and invaded epithelial cells at significantly greater levels than the other strains. There were negligible differences in gingipain activities among the six strains; however, type II P. gingivalis apparently degraded intracellular paxillin in association with a loss of phosphorylation 30 min after infection. Degradation was blocked with cytochalasin D or in mutants with fimA disrupted. Paxillin was degraded by the mutant with Lys-gingipain disrupted, and this degradation was prevented by inhibition of Arg-gingipain activity by Nalpha-p-tosyl-l-lysine chloromethyl ketone. FAK was also degraded by type II P. gingivalis. Cellular focal adhesions with green fluorescent protein-paxillin macroaggregates were clearly destroyed, and this was associated with cellular morphological changes and microtubule disassembly. In an in vitro wound closure assay, type II P. gingivalis significantly inhibited cellular migration and proliferation compared to the cellular migration and proliferation observed with the other types. These results suggest that type II P. gingivalis efficiently invades epithelial cells and degrades focal adhesion components with Arg-gingipain, which results in cellular impairment during wound healing and periodontal tissue regeneration.

Inhibitory effects of macrocarpals on the biological activity of Porphyromonas gingivalis and other periodontopathic bacteria

BACKGROUND/AIMS

Macrocarpals, which are phloroglucinol derivatives contained in eucalyptus leaves, exhibit antimicrobial activity against a variety of bacteria including oral bacteria. This study examined effects of macrocarpals A, B, and C on periodontopathic bacteria, especially Porphyromonas gingivalis.

METHODS

Macrocarpals A, B, and C were purified from a 60% ethanol-extract of Eucalyptus globules leaves. To investigate antibacterial activity, representative periodontopathic bacteria were cultured in media with or without various amounts of macrocarpals; subsequently, the optical density at 660 nm was measured. Macrocarpal inhibition of P. gingivalis Arg- and Lys-specific proteinases was assessed by spectrofluorophotometric assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The effect of macrocarpals on P. gingivalis binding to saliva-coated hydroxyapatite beads was examined with (3)H-labeled P. gingivalis.

RESULTS

Growth of P. gingivalis was inhibited more strongly than growth of Prevotella intermedia or Prevotella nigrescens and Treponema denticola by macrocarpals, however, Actinobacillus actinomycetemcomitans and Fusobacterium nucleatum were much more resistant. Macrocarpals inhibited P. gingivalis Arg- and Lys-specific proteinases in a dose-dependent manner. The enzyme-inhibitory effect of macrocarpals was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis in which hemoglobin degradation by P. gingivalis proteinase was inhibited by macrocarpals. P. gingivalis binding to saliva-coated hydroxyapatite beads was also strongly attenuated by macrocarpals.

CONCLUSIONS

Macrocarpals A, B and C demonstrated antibacterial activity against periodontopathic bacteria. Among tested bacteria, P. gingivalis displayed the greatest sensitivity to macrocarpals; additionally, its trypsin-like proteinase activity and binding to saliva-coated hydroxyapatite beads were inhibited by macrocarpals. These results indicate that eucalyptus leaf extracts may be useful as a potent preventative of periodontal disease.

Periodontitis is associated with preeclampsia in pregnant women

BACKGROUND

Recent investigations have demonstrated a positive association between periodontitis and pregnancy complications. The purpose of this study was to determine the effect of periodontitis and the subgingival microbial composition on preeclampsia.

METHODS

A case-control study was carried out in Cali, Colombia that included 130 preeclamptic and 243 non-preeclamptic women between 26 to 36 weeks of pregnancy. Sociodemographic data, obstetric risk factors, periodontal status, and subgingival microbial composition were determined in both groups. Preeclampsia was defined as blood pressure>or=140/90 mm Hg, and >or=2+ proteinuria, confirmed by 0.3 g proteinuria/24 hours of urine specimens. Controls were healthy pregnant women. Odds ratios (ORs) for periodontitis and subgingival microbiota compositions were calculated.

RESULTS

A total of 83 out of 130 preeclamptic women (63.8%) and 89 out of 243 controls (36.6%) had chronic periodontitis (OR: 3.0; 95% confidence interval (CI): 1.91 to 4.87; P<0.001). Clinical attachment loss increased in the case group (4.0+/-0.10 mm) compared to the control group (3.0+/-0.08 mm) (P<0.001). The average newborn birth weight from preeclamptic mothers was 2.453 g, whereas in controls was 2.981 g (P<0.001). Two red complex microorganisms, Porphyromonas gingivalis and Tannerella forsythensis, and the green complex microorganism Eikenella corrodens were more prevalent in the preeclamptic group than in controls (P<0.01).

CONCLUSIONS

Chronic periodontal disease and the presence of P. gingivalis, T. forsythensis, and E. corrodens were significantly associated with preeclampsia in pregnant women. Further research is needed to establish pathogenic mechanisms of active periodontal disease and subgingival periodontopathogens related to preeclampsia development.

Apple- and Hop-Polyphenols Protect Periodontal Ligament Cells Stimulated With Enamel Matrix Derivative FromPorphyromonas gingivalis

BACKGROUND

Enamel matrix derivative (EMD) is a tissue regenerative agent used clinically as an adjunct to periodontal surgery. It was previously demonstrated that Porphyromonas gingivalis, a periodontal pathogen, significantly diminished the efficacy of EMD with periodontal ligament (PDL) cells through the proteolytic actions of Arg- and Lys-gingipains (Rgp and Kgp). Thus, antiproteolytic supplements are considered clinically desirable for effective periodontal regenerative therapies. In the present study, we examined apple- (AP) and hop-polyphenols to determine their ability to protect EMD-stimulated PDL cells from P. gingivalis.

METHODS

AP, apple condensed tannin (ACT), hop bract polyphenol (HBP), high and low molecular weight fractions of HBP (HMW-HBP and LMW-HBP), and epigallocatechin gallate (EGCg) were used. PDL cells were grown on EMD-coated dishes and infected with P. gingivalis, and cellular migration and proliferation were evaluated with an in vitro assay of wound healing assay in the presence or absence of the polyphenols.

RESULTS

Each polyphenol significantly enhanced the viability of PDL cells infected with P. gingivalis, whereas only EGCg demonstrated cytotoxicity. Further, all polyphenols significantly inhibited Rgp activity, with AP, ACT, and HBP more effective toward Kgp. P. gingivalis markedly diminished the migration and proliferation of EMD-stimulated PDL cells, whereas the addition of AP, ACT, HBP, and HMW-HBP significantly protected the cells from bacterial cytotoxicity. In contrast, EGCg and LMW-HBP did not show protective effects.

CONCLUSION

These results suggest that AP, ACT, AP, HBP, and HMW-HBP protect EMD-stimulated PDL cells from P. gingivalis and may be therapeutically useful supplements for EMD therapy.

Synthesis and assembly of an adjuvanted Porphyromonas gingivalis fimbrial antigen fusion protein in plants

The gram-negative anaerobic oral bacterium Porphyromonas gingivalis initiates periodontal disease by binding to saliva-coated oral surfaces. To assess whether edible plants can synthesize biologically active P. gingivalis fimbrial antigen, for application as an oral vaccine, a cDNA fragment encoding the C-terminal binding portion of P. gingivalis fimbrial protein (FimA), was cloned into a plant expression vector immediately downstream of a cDNA fragment encoding the cholera toxin B subunit (CTB). The chimeric plasmid was transferred into potato (Solanum tuberosum) cells and the ctb-fimA cDNA fragment detected in transformed leaf genomic DNA by PCR amplification methods. A novel protein band of 21 kDa was detected in transformed potato tuber extracts by immunoblot analysis. Oligomeric CTB-FimA (266-337) fusion protein was identified in the extracts through the binding of anti-CTX and anti-native fimbriae antibodies. The pentameric structure of CTB-FimA fusion protein was confirmed by ELISA measurements of GM1 ganglioside receptor binding. Quantification of the CTB-FimA fusion protein by ELISA indicated that the chimeric protein made up about 0.33% of total soluble tuber protein. The biosynthesis of immunologically detectable CTB-FimA fusion proteins and the assembly of fusion protein monomers into biologically active pentamers in transformed potato tuber tissues demonstrate the feasibility of synthesizing adjuvanted fimbrial protein in edible plants for development of adjuvanted mucosal vaccines against P. gingivalis generated periodontal disease.

Roles of Arg- and Lys-gingipains in coaggregation of Porphyromonas gingivalis: identification of its responsible molecules in translation products of rgpA, kgp, and hagA genes

Arg- (Rgp) and Lys-gingipains (Kgp) are two individual cysteine proteinases produced by Porphyromonas gingivalis , an oral anaerobic bacterium, and are implicated as major virulence factors in a wide range of pathologies of adult periodontitis. Coaggregation of this bacterium with other oral bacteria is an initial and critical step in infectious processes, yet the factors and mechanisms responsible for this process remain elusive. Here we show that the initial translation products of the rgpA , kgp and hemagglutinin hagA genes are responsible for coaggregation of P. gingivalis and that the proteolytic activity of Rgp and Kgp is indispensable in this process. The rgpA rgpB kgp- and rgpA kgp hagA -deficient triple mutants exhibited no coaggregation activity with Actinomyces viscosus , whereas the kgp -null and rgpA rgpB -deficient double mutants significantly retained this activity. Consistently, the combined action of Rgp- and Kgp-specific inhibitors strongly inhibited the coaggregation activity of the bacterium, although single use of Rgp- or Kgp-specific inhibitor significantly retained this activity. We also demonstrate that the 47- and 43-kDa proteins produced from the translation products of the rgpA , kgp , and hagA genes by proteolytic activity of both Rgp and Kgp are responsible for the coaggregation of P. gingivalis.

Properties of hemagglutination by Prevotella melaninogenica

Although Prevotella melaninogenica belongs to the commensal oral microbiota, some strains possess putative virulence factors. For example, we have previously described fimbriated, hemagglutinating strains of P. melaninogenica, isolated from patients with periodontal disease. The aim of this investigation was to compare some chemical and physical properties of hemagglutination (HA) of P. melaninogenica with those of other pigmented gram-negative anaerobes. HA of 13 P. melaninogenica strains proved to be considerably weaker than that of the major periodontal pathogen, Porphyromonas gingivalis. Vigorous shaking reduced HA of shaken cells but the shaken supernatant had the same hemagglutinating activity as non-shaken cells. The hemagglutinating agent on P. melaninogenica seemed to be a protein, which can be separated from the cell and binds to lactose-, galactose-, and raffinose-containing carbohydrates on the erythrocytes. Adherence to epithelial cells did not differ significantly between the hemagglutinating and non-hemagglutinating strains of P. melaninogenica. Although P. melaninogenica is able to agglutinate erythrocytes, this potential virulence factor is of a considerably lower magnitude than that of major periodontal pathogens.

Inhibitory effects of Porphyromonas gingivalis fimbriae on interactions between extracellular matrix proteins and cellular integrins

Porphyromonas gingivalis is a predominant periodontal pathogen, whose fimbriae are considered to be a major virulence factor, especially for bacterial adherence and invasion of host cells. In the present study, we investigated the influence of fimbriae on the interactions between alphavbeta3- and alpha5beta1-integrins and their ligand extracellular matrix (ECM) proteins (vitronectin and fibronectin), using human alphavbeta3- and alpha5beta1-integrin-overexpressing CHO cell lines (CHOalphavbeta3 and CHOalpha5beta1, respectively). P. gingivalis was found to have significantly greater binding to CHOalphavbeta3 and CHOalpha5beta1 than to control cells, whereas a fimbria-deficient mutant showed negligible binding to any of the tested cell lines. CHOalphavbeta3 and CHOalpha5beta1 cells attached to the polystyrene culture dishes in the presence of their ligand ECM proteins, while fimbriae markedly inhibited those attachments in a dose-dependent manner, with the highest dose of fimbriae achieving complete inhibition. In addition, the binding of vitronectin and fibronectin to CHOalphavbeta3 and CHOalpha5beta1 was inhibited by P. gingivalis cells. These results suggest that P. gingivalis fimbriae compete with ECM proteins for alphavbeta3- and alpha5beta1-integrins, and inhibit integrin/ECM protein-related cellular functions.

Direct detection of cell surface interactive forces of sessile, fimbriated and non-fimbriated Actinomyces spp. using atomic force microscopy

Actinomyces species are predominant early colonizers of the oral cavity and prime mediators of inter-bacterial adhesion and coaggregation. Previous workers have evaluated the adhesion of Actinomyces spp. by quantitative assessment of sessile, as opposed to planktonic cells attached to substrates, but did not quantify the cell surface interactive forces. Therefore we used atomic force microscopy to directly detect the interactive force between an approaching silicon tip and sessile Actinomyces spp. adhering to a substrate, at nanonewton (nN) range force levels. A total of eight strains each belonging to fimbriated and non-fimbriated Actinomyces species were employed, namely A. bovis, A. gerencseriae, A. israelii, A. meyeri, A. naeslundii genospecies 1 and 2, A. odontolyticus and A. viscosus. The sterile mica discs, used as the adhesion substrate, were immersed in mono-species bacterial suspensions for five days to obtain a thin bacterial biofilm. Interactive forces were measured using a silicon nitride cantilever attached to a Nanoscope IIIA atomic force microscope. The interactive forces between the approaching silicon nitride tip and bacterial biofilm surfaces were randomly quantified at three different locations on each cell; namely, the cell surface proper, the periphery of the cell and the substrate and, the interface between two cells. When the interactive forces at these locations of the same species were compared, significantly higher force levels at the cell-cell interface than the other two locations were noted with A. gerencseriae (P < 0.001), A. viscosus (P < 0.01) and A. israelii (P < 0.05). When the interactive forces of different Actinomyces spp. at an identical location were compared, fimbriated A. naeslundii genospecies 2 showed the greatest interactive force at the cell surface proper (-32.6 +/- 8.7 nN, P < 0.01). A. naeslundii genospecies 1, 2 and A. viscosus demonstrated greater interactive force at the cell-mica periphery than the other five species (P < 0.05); A. viscosus (-34.6 +/- 10.5 nN) displayed greater interactive force at the cell-cell interface than the others (P < 0.01), except for A. gerencseriae (P > 0.05). These data indicate that fimbriated Actinomyces spp., including A. naeslundii genospecies 1, 2 and A. viscosus exert higher cell surface interactive forces than those devoid of fimbriae and, such variable force levels may modulate their adhesion and coaggregation during biofilm formation.

Effect of enamel matrix derivative on periodontal ligament cells in vitro is diminished by Porphyromonas gingivalis

BACKGROUND

Enamel matrix derivative (EMD) has been shown to possess a mitogenic effect to induce effective periodontal regeneration, however, it is unclear whether periodontal pathogens can modulate the effect of EMD. The present study examined the influence of Porphyromonas gingivalis on EMD-stimulated periodontal ligament (PDL) cells.

METHODS

P. gingivalis ATCC33277 and its mutants deficient in fimbriae (delta fimA) or gingipains (delta rgpA delta rgpB, delta kgp, and delta rgpA delta rgpB delta kgp) were employed. PDL cells were grown on EMD-coated dishes and infected with P. gingivalis wild strain or a mutant. Cell migration and proliferation were then evaluated with an in vitro wound healing assay. The expression of transforming growth factor-beta1 (TGF-beta1) and insulin-like growth factor I (IGF-I) mRNA by PDL cells was examined. Further, the degradation and phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) as well as paxillin in infected PDL cells were estimated using Western blot analysis.

RESULTS

P. gingivalis ATCC33277 inhibited the migration and proliferation of PDL cells on EMD-coated dishes, and the mutants delta fimA, delta rgpA delta rgpB, and delta kgp showed the same effects. Further, each of these organisms diminished the expression of TGF-beta1 and IGF-I mRNA, as well as the phosphorylation of ERK1/2 from EMD-stimulated PDL cells. In addition, total paxillin protein was markedly degraded by both the wild-type strain and each of the mutants except for delta rgpA delta rgpB delta kgp, which showed a negligible effect in all of the assays with EMD-stimulated PDL cells.

CONCLUSION

These results suggest that P. gingivalis diminishes the effect of EMD on PDL cells in vitro through a cooperative action of gingipains.

Distribution of fimA genotypes of Porphyromonas gingivalis in subjects with various periodontal conditions

Fimbria encoded by the gene fimA is considered one of the main factors in the colonization of the oral cavity by Porphyromonas gingivalis. Allelic variation in fimA led to the classification of strains of P. gingivalis into six genotypes. The occurrence of P. gingivalis was determined by polymerase chain reaction using 16S rRNA primers in 302 subgingival samples obtained from 102 Brazilian subjects exhibiting different periodontal conditions. Distribution of fimA genotypes was assessed in 146 P. gingivalis positive samples by polymerase chain reaction using primers pairs homologous to the different fimA genes. P. gingivalis was detected in 51 of 57 (89.4%) patients with periodontal attachment loss, in six of 20 gingivitis patients (30.0%) and in two of 25 (8.0%) subjects with a healthy periodontium. Variant type II was the only type detected in 53 sites (39.3%), distributed among 19 periodontitis patients (37.3%) and in one patient with no periodontal destruction. Type Ib was the second most prevalent genotype in periodontitis patients (19.6%). Genotype V was not detected in the studied population. Type IV was the most commonly type found among gingivitis patients, either alone or in combination with other genotypes. Multiple genotypes were detected in nine sites (6.1%). A fimA genotype was not identified in 26 sites (17.8%) of 146 sites positive for P. gingivalis, suggesting that other alleles of fimA not yet sequenced may be prevalent in this population. These data demonstrated that P. gingivalis type II strains followed by type Ib are more prevalent in periodontitis patients from a multiracial population in Brazil, suggesting an increased pathogenic potential of these types.

Differential gene induction in macrophage-like human cells by two types of Porphyromonas gingivalis: a microarray study

Several studies have provided clinical evidence that FimA clonal variation may contribute to the periodontopathogenicity of Porphyromonas gingivalis (P.g.). We studied the gene expression profiling of the macrophage-like human cell line U937 after infection of two types of P.g. (fimA type I; Pg-I and fimA type II; Pg-II) using microarray. Of 1088 genes examined, 394 genes were detectable. Bioinformatics algorithms were used to analyze the detectable genes. Hierarchical clustering analysis showed that gene expression patterns of Pg-II and the control (no infection) were grouped together. K-means clustering grouped 79 genes into Pg-II dominance and 88 genes into Pg-I dominance. A large number of genes related to cell signaling, extracellular communication proteins, cell receptors (by ligands), protein turnover and cell adhesion receptors/proteins were grouped into clusters of Pg-I dominance. Our results indicate that compared with Pg-I, Pg-II induces a low host response as measured by its weak induction of gene expression.

Differential cytokine induction by two types of Porphyromonas gingivalis

The presence of Porphyromonas gingivalis with type II fimA is strongly associated with adult periodontitis. However, the importance of specific fimA types in the immune response is unknown. Two types of P. gingivalis (type I and type II) and Actinomyces naeslundii were assessed for their degree of cytokine induction in the macrophage-like human cell line U937. Real-time reverse transcriptase polymerase chain reaction was used to determine mRNA expression of 12 cytokines. Significant levels of interleukin (IL)-8 induction and a similar cytokine expression pattern were observed at 6 h postinfection for all three bacterial strains. However, type II P. gingivalis infection showed statistically higher levels of IL-1beta, IL-8, IL-12 and tumor necrosis factor-alpha mRNA induction than those of control at 24 h postinfection, whereas type I P. gingivalis and A. naeslundii showed no significant induction of these cytokines. These data suggest that compared with A. naeslundii and type I P. gingivalis, type II P. gingivalis prolongs the cytokine response. Although other factors may also be involved, the sustained cytokine response induced by type II P. gingivalis may play an important role in enhanced periodontal tissue inflammation and destruction.

The csp operon of Streptococcus salivarius encodes two predicted cell-surface proteins, one of which, CspB, is associated with the fimbriae

A Tn917 mutant library was generated to identify genes involved in the biogenesis of Streptococcus salivarius fimbriae. A fimbria-deficient mutant was isolated by negative selection using an immunomagnetic separation technique with specific anti-fimbriae polyclonal antibodies (pAbs). The transposon was inserted in an ORF, called orf176, which encoded a protein of unknown function. The transposon prevented the transcription of orf176 as well as two genes located downstream, which are designated cspA and cspB and which form the csp operon. Sequence analyses of CspA and CspB revealed that both proteins possessed the classic cell-wall-anchoring motif (LPXTG) of Gram-positive bacterial surface proteins. Recombinant CspA (rCspA) and CspB (rCspB) proteins were generated in Escherichia coli and used to produce pAbs. Immunolocalization experiments showed that anti-rCspB, but not anti-rCspA antibodies specifically recognized S. salivarius fimbriae. Our results suggested that the csp operon encoded predicted cell-surface proteins, one of which, CspB, was associated with the fimbriae.

ANTI-PHAGOCYTIC ROLE OF SURFACE FIBROUS STRUCTURE OF AN INVASIVE PORPHYROMONAS GINGIVALIS STRAIN

Recent studies have shown that invasive and non-invasive strains of Porphyromonas gingivalis can both be isolated from patients with periodontitis. We examined the interaction between an invasive 16-1 P. gingivalis strain and phagocytes obtained from human peripheral blood and guinea pig peritoneal cavity. Phagocytes from human peripheral blood, mainly polymorphonuclear leukocytes (PMNs) isolated by centrifugation in Ficoll Hypaque, and macrophages collected from the peritoneal cavity of guinea pigs, were exposed to P. gingivalis cells. After this exposure, greater numbers of the non-invasive P. gingivalis ATCC 33277 were observed in human PMNs and guinea pig macrophages compared with the invasive P. gingivalis 16-1. Electron microscopic observations showed that invasive 16-1 within phagosomes in human PMNs and guinea pig macrophages retained their surface fibrous structures as well as their outer membranes. Electron microscopic examination showed that destruction and damage to the cell membranes and inner structures were clear in human PMNs and guinea pig macrophages after exposure to invasive 16-1 for 6 and 24 hours; this was a clear difference from exposure to the non-invasive ATCC 33277. Release of lactate dehydrogenase (LDH) activities into the culture supernatant of PMNs after exposure to the invasive 16-1 for 4 and 6 hours was significantly greater than that after exposure to the non-invasive ATCC 33277 (p<0.05). On the other hand, the LDH activity after exposure for 21 hours to the invasive 16-1 was significantly lower than that of untreated cells and cells after exposure to the non-invasive ATCC 33277 strain (p<0.05). The PMN viabilities after exposure to cells of the invasive 16-1 for 3, 4, and 6 hours as evaluated by trypan blue staining were similar to those after exposure to cells of the non-invasive ATCC 33277, but that after exposure to the invasive 16-1 strain for 21 hours was significantly lower than that after exposure to cells of the non-invasive ATCC 33277 strain.

Direct detection of Actinomyces spp. from infected root canals in a Chinese population: a study using PCR-based, oligonucleotide-DNA hybridization technique

OBJECTIVES

The poor sensitivity of phenotypic identification techniques has hampered the taxonomic differentiation of Actinomyces. Hence we developed a sensitive and specific, PCR-based oligonucleotide-DNA hybridization technique to detect Actinomyces spp. and, used this method to detect these organisms in samples directly obtained from infected root canals.

METHODS

A total of 32 samples from 28 Chinese patients, with primary root canal infections, aseptically exposed at the first patient visit, were studied. Whole bacterial genomic DNA was isolated directly from paper point samples. The variable regions of 16S ribosomal DNA of bacteria were amplified and labeled with digoxigenin for further hybridization and detection. A total of seven oligonucleotide probes specific for A. bovis, A. gerencseriae, A. israelii, A. meyeri, catalase-negative A. naeslundii (genospecies 1 and 2), catalase-positive A. naeslundii genospecies 2 and A. odontolyticus were used.

RESULTS

16 of the 32 teeth were infected with one or more Actinomyces species. The prevalence rates of the examined species were: A. odontolyticus 31.3%, A. meyeri 9.4%, A. naeslundii 9.4%, A. israelii 6.3% and A. gerencseriae 3.1%; no A. bovis was detected in any of the canals. Furthermore, A. odontolyticus was isolated more frequently from root canals with caries or a history of caries (Fisher's exact test: P=0.0496; Odds ratio=9.00, 95% confidence interval: 0.97-83.63), and A. naeslundii was significantly associated with traumatized teeth (Fisher's exact test: P=0.0121; Odds ratio=57.00, 95% confidence interval: 2.10-1546.90). However, no significant correlation was found between Actinomyces spp. and clinical symptoms and signs, such as pain, swelling, percussion to tenderness, sinus and periapical radiolucency.

CONCLUSION

Actinomyces spp. may be important pathogens of root canal infections. A. naeslundii in particular may be related with traumatized teeth. A. odontolyticus appears to be involved in infections related to caries, exposure of dentinal tubules during cavity preparation and/or leaking restoration, but further clarification with large samples is necessary.

Coaggregation of Streptococcus salivarius with periodontopathogens: evidence for involvement of fimbriae in the interaction with Prevotella intermedia

Streptococcus salivarius is divided into two serological subgroups that carry either fibrils or fimbriae. Although fimbriae have been observed on up to 50% of S. salivarius strains in the human oral cavity, no function has yet been assigned to them. To determine whether S. salivarius fimbriae have a role in adhesion, we examined the ability of S. salivarius to coaggregate with selected microorganisms involved in periodontal diseases. Our results show that S. salivarius coaggregated with Fusobacterium nucleatum, Porphyromonas gingivalis, and Prevotella intermedia. However, only fimbriated S. salivarius cells were able to coaggregate with P. intermedia, suggesting a specific role for these structures in the interaction. Heat treatment, sensitivity to sugars, amino acids, and EDTA, as well as protease treatment were also used to further characterize coaggregation between S. salivarius and periodontopathogens.