The microbial challenge in periodontitis

Modulation of chronic enteric infection by distant oral infection

This investigation determined the effects of a distant oral infection (Porphyromonas gingivalis) on a concurrent local enteric infection (Echerichia coli). A modified murine subcutaneous tissue chamber model was used. Subcutaneously implanted chambers with different microbial makeups were monitored for sloughing and their contents assayed for prostaglandin E2. Bilaterally implanted chamber experiments revealed that a distant "chronic" (immunization with heat-killed organism, followed by live challenge) P. gingivalis infection offered protection against a local chronic E. coli infection, as evidenced by delaying the time for 50% of the chambers to reject from day 19 to day 25 and a statistically significant prostaglandin E2 decrease from 529.4 +/- 176.6 ng/ml to 191.5 +/- 100.9 ng/ml (p < 0.01) (Mann-Whitney test). An acute (live challenge only) distant P. gingivalis infection or immunization with the heat-killed organism alone had no effect on "chronic" E. coli infection in this model. These data suggest that the presence of low-grade chronic oral infection may modify the responses to other infectious challenges.

Secretion of functional salivary peptide by Streptococcus gordonii which inhibits fimbria-mediated adhesion of Porphyromonas gingivalis

Porphyromonas gingivalis, a putative periodontopathogen, can bind to human salivary components with its fimbriae. We have previously shown that fimbriae specifically bind to a peptide domain shared by a major salivary component, i.e., proline-rich (glyco)proteins (PRPs). The synthetic domain peptide PRP-C (pPRP-C) significantly inhibits the fimbrial binding to PRPs. In this study, a recombinant strain of Streptococcus gordonii secreting pPRP-C was generated as a model of a possible approach to prevent the oral colonization by the pathogen. A duplicate DNA fragment (prpC) encoding pPRP-C was obtained by self-complementary annealing of synthetic oligonucleotides. prpC was connected downstream to a promoter and a gene encoding a signal peptide of Streptococcus downei glucosyltransferase I in frame. The linked fragments were inserted into the plasmid pMNK-4 derived from pVA838. The constructed plasmid was inserted to produce the transformant S. gordonii G9B, which then successfully secreted recombinant pPRP-C (r-pPRP-C) of the expected size. The concentrated bacterial culture supernatant containing r-pPRP-C inhibited the binding of P. gingivalis cells and fimbriae to PRP1 in a dose-dependent manner up to 72 and 77%, respectively. The r-pPRP-C concentrate also inhibited the coaggregation of P. gingivalis with various streptococcal strains as effectively as synthetic pPRP-C in a dose-dependent manner. Collectively, pPRP-C was found to be able to prevent P. gingivalis adherence to salivary receptor protein and plaque-forming bacteria. These results suggest that this recombination approach with a nonperiodontopathic bacterium may be suitable for the therapeutic prevention of P. gingivalis adherence to the oral cavity.

Distribution of Porphyromonas gingivalis strains with fimA genotypes in periodontitis patients

Fimbriae (FimA) of Porphyromonas gingivalis are filamentous components on the cell surface and are thought to play an important role in the colonization and invasion of periodontal tissues. We previously demonstrated that fimA can be classified into four variants (types I to IV) on the basis of the nucleotide sequences of the fimA gene. In the present study, we attempted to detect the four different fimA genes in saliva and plaque samples isolated from patients with periodontitis using the PCR method. Four sets of fimA type-specific primers were designed for the PCR assay. These primers selectively amplified 392-bp (type I), 257-bp (type II), 247-bp (type III), and 251-bp (type IV) DNA fragments of the fimA gene. Positive PCR results were observed with reference strains of P. gingivalis in a type-specific manner. All other laboratory strains of oral and nonoral bacteria gave negative results. The sensitivity of the PCR assay for fimA type-specific detection was between 5 and 50 cells of P. gingivalis. Clinical samples were obtained from saliva and subgingival plaque from deep pockets (>/=4 mm) of 93 patients with periodontitis. Bacterial genomic DNA was isolated from the samples, and the targeted fragments were amplified by PCR. The presence of P. gingivalis was demonstrated in 73 patients (78.5%), and a single fimA gene was detected in most patients. The distribution of the four fimA types among the P. gingivalis-positive patients was as follows: type I, 5.4%; type II, 58.9%; type III, 6. 8%; type IV, 12.3%; types I and II, 6.8%; types II and IV, 2.7%; and untypeable, 6.8%. P. gingivalis with type II fimA was detected more frequently in the deeper pockets, and a significant difference of the occurrence was observed between shallow (4 mm) and deep (>/=8 mm) pockets. These results suggest that P. gingivalis strains that possess type II fimA are significantly more predominant in periodontitis patients, and we speculate that these organisms are involved in the destructive progression of periodontal diseases.

Simultaneous detection of Bacteroides forsythus and Prevotella intermedia by 16S rRNA gene-directed multiplex PCR

In a 16S rRNA gene-directed multiplex PCR, Prevotella intermedia- and Bacteroides forsythus-specific reverse primers were combined with a single conserved forward primer. A 660-bp fragment and an 840-bp fragment that were specific for both species could be amplified simultaneously. A total of 152 clinical samples, subgingival plaque and swabs of three different oral mucosae, from 38 periodontitis patients were used for the evaluation.

Adherence of Peptostreptococcus micros morphotypes to epithelial cells in vitro

Peptostreptococcus micros, which is associated with oral and non-oral mixed anaerobic infections, occurs in three colony morphotypes, the smooth type, the rough type and the smooth variant of the rough type. These types differ in surface structures; the rough type expresses large fibrillar surface appendages, which are absent on the surface of both the smooth and the smooth variant of the rough type. To determine the role of these surface structures in adherence we characterized the adherence of the three morphotypes of P. micros to epithelial cells in vitro. Although all three types adhered well to epithelial cells, adhering numbers of the rough type were significantly lower than those of the smooth and the smooth variant of the rough type. Protease treatment increased the adherence of the rough type of the level of the two other types. The adherence of all three types was reduced more than 85% by treatment with 10 mM sodium periodate. Furthermore, the adherence was pH independent and could not be blocked by incubation with antisera to the bacteria. In addition, we determined the capacity to invade epithelial cells by P. micros. In an acridine orange assay such invasion could not be detected. Our results suggest that the adherence of P. micros to epithelial cells is mediated by periodate-sensitive extracellular polysaccharides and that the protruding fibril-like protein surface structures of the rough type have an obstructive effect on the adherence.

Life below the gum line: pathogenic mechanisms of Porphyromonas gingivalis

Porphyromonas gingivalis, a gram-negative anaerobe, is a major etiological agent in the initiation and progression of severe forms of periodontal disease. An opportunistic pathogen, P. gingivalis can also exist in commensal harmony with the host, with disease episodes ensuing from a shift in the ecological balance within the complex periodontal microenvironment. Colonization of the subgingival region is facilitated by the ability to adhere to available substrates such as adsorbed salivary molecules, matrix proteins, epithelial cells, and bacteria that are already established as a biofilm on tooth and epithelial surfaces. Binding to all of these substrates may be mediated by various regions of P. gingivalis fimbrillin, the structural subunit of the major fimbriae. P. gingivalis is an asaccharolytic organism, with a requirement for hemin (as a source of iron) and peptides for growth. At least three hemagglutinins and five proteinases are produced to satisfy these requirements. The hemagglutinin and proteinase genes contain extensive regions of highly conserved sequences, with posttranslational processing of proteinase gene products contributing to the formation of multimeric surface protein-adhesin complexes. Many of the virulence properties of P. gingivalis appear to be consequent to its adaptations to obtain hemin and peptides. Thus, hemagglutinins participate in adherence interactions with host cells, while proteinases contribute to inactivation of the effector molecules of the immune response and to tissue destruction. In addition to direct assault on the periodontal tissues, P. gingivalis can modulate eucaryotic cell signal transduction pathways, directing its uptake by gingival epithelial cells. Within this privileged site, P. gingivalis can replicate and impinge upon components of the innate host defense. Although a variety of surface molecules stimulate production of cytokines and other participants in the immune response, P. gingivalis may also undertake a stealth role whereby pivotal immune mediators are selectively inactivated. In keeping with its strict metabolic requirements, regulation of gene expression in P. gingivalis can be controlled at the transcriptional level. Finally, although periodontal disease is localized to the tissues surrounding the tooth, evidence is accumulating that infection with P. gingivalis may predispose to more serious systemic conditions such as cardiovascular disease and to delivery of preterm infants.

Virulence of a polymicrobic complex, Treponema denticola and Porphyromonas gingivalis, in a murine model

The effect of a polymicrobic infection employing Treponema denticola and Porphyromonas gingivalis in the murine lesion model was used to determine the synergistic virulence of these two periodontopathic bacteria. At high doses of P. gingivalis W50, addition of T. denticola in the infection mixture had no effect on the formation and size of the spreading lesion caused by this microorganism. However, at low P. gingivalis challenge doses, T. denticola significantly enhanced the virulence of P. gingivalis compared with monoinfection of this microorganism. A potential role of the trypsin-like protease enzyme activity of P. gingivalis in this synergistic virulence was tested using P. gingivalis mutants deficient (i.e., BEI) or devoid (i.e., NG4B19) of this protease activity. These findings demonstrated that T. denticola-P. gingivalis complexes exhibit enhanced virulence in this model and that even using a polymicrobic challenge infection, the trypsin-like protease activity was important to P. gingivalis virulence expression.

Additional clinical and microbiological effects of amoxicillin and metronidazole after initial periodontal therapy

The aims of this study were to evaluate the clinical and microbiological effects of initial periodontal therapy (IT) and to determine the additional effects of systemic amoxicillin (Flemoxin Solutab) 375 mg TID plus metronidazole 250 mg TID therapy, in patients with adult Actinobacillus actinomycetemcomitans (Aa)-associated periodontitis in conjunction with either Porphyromonas gingivalis (Pg), Bacteroides forsythus (Bf) and/or Prevotella intermedia (Pi). In addition the adverse effects of the antimicrobial therapy were also documented. A total of 22 patients were enrolled. The deepest, bleeding pocket in each quadrant was selected and at these 4 experimental sites clinical measurements and microbiological testing was carried out at baseline, after (IT), i.e., 21 weeks after baseline, and after antimicrobial therapy (AM), i.e., 35 weeks after baseline. At baseline, the mean plaque index (PI) amounted 0.5, 0.1 after IT and 0.3 after systemic AM. The mean bleeding index decreased from 1.6 to 1.2 after IT and a further decrease to 0.7 after AM was noted. Suppuration was completely eliminated after AM. The mean change of probing pocket depth (PPD) after IT amounted 1.4 mm and was further reduced with an additional mean change of 1.1 mm after medication. Clinical attachment gain was 1.1 mm after IT and an additional 0.9 mm was observed after AM. One of the 22 Aa positive patients and 4 of 17 Pg positive patients became negative for these species after IT. The number of patients with detectable Pi decreased from 16 to 10 after IT. After AM, in comparison to baseline, suppression below detection level for Aa was achieved in 19 out of 22, for Pg in 9 out of 17, for Bf in 13 out of 14, and for Pi in 11 out of 16 patients. By contrast, higher frequencies of Peptostreptococcus micros and Fusobacterium nucleatum were found after AM. On the basis of the microbiological results the study group was separated into 2 subgroups: group A consisted of subjects who had no detectable levels of Aa, Pg, Bf and <5% of Pi after AM. Group B consisted of those who still showed presence of one of these 3 species and/or > or =5% levels of Pi. After AM, group B had significantly higher PI, BI, PPD and CAL scores then group A. It is concluded that group A showed low plaque scores and no detectable periodontal pathogens. This microbiological condition has been associated with a long-term stable periodontium.

Periodontal disease and diabetes mellitus: a two-way relationship

Severe periodontal disease often coexists with severe diabetes mellitus. Diabetes is a risk factor for severe periodontal disease. A model is presented whereby severe periodontal disease increases the severity of diabetes mellitus and complicates metabolic control. We propose that an infection-mediated upregulation cycle of cytokine synthesis and secretion by chronic stimulus from lipopolysaccharide (LPS) and products of periodontopathic organisms may amplify the magnitude of the advanced glycation end product (AGE)-mediated cytokine response operative in diabetes mellitus. In this model, the combination of these 2 pathways, infection and AGE-mediated cytokine upregulation, helps explain the increase in tissue destruction seen in diabetic periodontitis, and how periodontal infection may complicate the severity of diabetes and the degree of metabolic control, resulting in a 2-way relationship between diabetes mellitus and periodontal disease/infection. This proposed dual pathway of tissue destruction suggests that control of chronic periodontal infection is essential for achieving long-term control of diabetes mellitus. Evidence is presented to support the hypothesis that elimination of periodontal infection by using systemic antibiotics improves metabolic control of diabetes, defined by reduction in glycated hemoglobin or reduction in insulin requirements.

The pathobiology of periodontal diseases may affect systemic diseases: inversion of a paradigm

A new paradigm for the pathobiology of periodontitis is presented, and the manner in which periodontitis may relate to susceptibility for certain systemic diseases such as cardiovascular disease and preterm labor is described. Periodontitis is caused by a small group of Gram-negative bacteria present on the tooth root surfaces as bioffilms. Lipopolysaccharide (LPS) and other substances gain access to the gingival tissues, initiate and perpetuate immunoinflammation, resulting in production of high levels of proinflammatory cytokines. These induce production of matrix metalloproteinases which destroy the connective tissues of the gingiva and periodontal ligament, and prostaglandins which mediate alveolar bone destruction. Periodontitis may enhance susceptibility to systemic diseases in several ways. LPS and viable Gram-negative bacteria from the biofilms and proinflammatory cytokines from the inflamed periodontal tissues may enter the circulation in pathogenic quantities. In addition, periodontitis and certain systemic diseases, such as cardiovascular disease, share risk factors including tobacco smoking, male gender, race/ethnicity, stress, and aging.

Effect of increased community and professional awareness of plaque control on the management of inflammatory periodontal diseases

Data from CPITN studies indicate that severe periodontitis affects approximately 10 per cent of most populations. These data have remained static for a number of years. Of interest, however, is that despite the dramatic increase in the use of oral hygiene aids, efforts by the dental profession in oral hygiene instruction, and the associated general improvement in oral hygiene levels in the community, the incidence of severe chronic inflammatory periodontal disease has remained largely unaffected. The effects of changing oral hygiene may be reflected in slight shifts in the mild and moderate classifications of periodontal disease but the prevalence of advanced disease in presumably susceptible subjects has remained relatively unchanged. The ramifications of relatively non-specific plaque control measures in the management of advanced disease in susceptible subjects are still unclear and it may not be until the adoption of a more specific approach to the control of specific pathogens which inhabit the subgingival biofilm that major changes in the general incidence of the severe inflammatory periodontal diseases will be seen.