Microbial etiological agents of destructive periodontal diseases

Prevalence of Peptostreptococcus micros morphotypes in patients with adult periodontitis

The prevalence of the smooth and rough colonial morphotypes of Peptostreptococcus micros was examined with culture technique in 123 patients with adult periodontitis (age 24-68 years). Of all subgingival samples, 91% contained the smooth morphotype of P. micros. The smooth morphotype constituted a mean percentage of the total anaerobic viable biota of 6.0%, with a range of 0.02-35.7%. Of these samples, 49% contained colonies of the rough morphotype as well, with a mean percentage of the total anaerobic viable biota of 2.3% (range 0.01-16.2%). None of the samples contained only the rough morphotype. The total percentage of P. micros varied from 0.02-35.71% with a mean of 7.2%. No correlation was found between the prevalence of both morphotypes of P. micros and the age of the subjects or with loss of attachment or pocket depth.

Rapid chair-side DNA probe assay of Bacteroides forsythus and Porphyromonas gingivalis

This study compared a rapid, colorimetric DNA probe assay designed to be performed in a dental office within 40 min, with anaerobic culture and indirect immunofluorescence microscopy (IFM) for detection of Bacteroides forsythus and Porphyromonas gingivalis in subgingival plaque samples. The DNA probe assay used the Periodontal Microbial Identification Test (Saigene Corporation, Bothell, Washington, USA). B. forsythus was detected in 46 (52%), 49 (55%) and 39 (44%) of the samples by DNA probe, culture (at levels > or = 10(5)) and IFM, respectively. P. gingivalis was detected in 24 (27%), 18 (20%) and 29 (33%) of the samples by DNA probe, culture (at levels > or = 10(5)) and IFM, respectively. Results from the DNA probe assay were compared to culture. Culture negative, probe positive samples were re-evaluated by IFM, and IFM positive samples were considered positive in "resolved" data. Using resolved data. DNA probe detection sensitivity and specificity values for B. forsythus were 81% and 91% and for P. gingivalis were 80% and 95%, respectively. DNA probe test results were further compared with culture and IFM. For samples negative by both culture and IFM, probe specificity was 92% in 25 B. forsythus samples and 95% in 57 P. gingivalis samples. For samples positive by both reference methods, probe sensitivity was 82% in 27 B. forsythus samples and 73% in 15 P. gingivalis samples. B. forsythus was detected more frequently by culture compared with IFM; the reverse was observed for P. gingivalis. The rapid DNA probe assay for B. forsythus and P. gingivalis was comparable to cultivable and IF analyses.

Microbiota of health, gingivitis, and initial periodontitis

This study compared the subgingival microbiota in periodontal health, gingivitis and initial periodontitis using predominant culture and a DNA probe, checkerboard hybridization method. 56 healthy adult subjects with minimal periodontal attachment loss were clinically monitored at 3-month intervals for 12 months. More sites demonstrated small increments of attachment loss than attachment gain over the monitoring period. Sites, from 17 subjects, showing > or = 1.5 mm periodontal attachment loss during monitoring were sampled as active lesions for microbial analysis. Twelve subjects demonstrated interproximal lesions, and 5 subjects had attachment loss at buccal sites (recession). Cultural studies identified Bacteroides forsythus, Campylobacter rectus, and Selenomonas noxia as the predominant species associated with active interproximal lesions (9 subjects), whereas Actinomyces naeslundii, and Streptococcus oralis, were the dominant species colonizing buccal active sites. A. naeslundii, Campylobacter gracilis, and B. forsythus (at lower levels than active sites) were the dominant species cultured from gingivitis (10 subjects). Health-associated species (10 subjects) included Streptococcus oralis, A. naeslundii, and Actinomyces gerencseriae. DNA probe data identified higher mean levels of B. forsythus and C. rectus with active (7 subjects) compared to inactive periodontitis sites. Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans were detected infrequently. Cluster analysis of the cultural microbiota grouped 8/9 active interproximal lesions in one subcluster characterized by a mostly gram-negative microbiota, including B. forsythus and C. rectus. The data suggest that B. forsythus C. rectus and S. noxia were major species characterizing sites converting from periodontal health to disease. The differences in location and microbiota of interproximal and buccal active sites suggested that different mechanisms may be involved in increased attachment loss.

Microbial complexes in subgingival plaque

It has been recognized for some time that bacterial species exist in complexes in subgingival plaque. The purpose of the present investigation was to attempt to define such communities using data from large numbers of plaque samples and different clustering and ordination techniques. Subgingival plaque samples were taken from the mesial aspect of each tooth in 185 subjects (mean age 51 +/- 16 years) with (n = 160) or without (n = 25) periodontitis. The presence and levels of 40 subgingival taxa were determined in 13,261 plaque samples using whole genomic DNA probes and checkerboard DNA-DNA hybridization. Clinical assessments were made at 6 sites per tooth at each visit. Similarities between pairs of species were computed using phi coefficients and species clustered using an averaged unweighted linkage sort. Community ordination was performed using principal components analysis and correspondence analysis. 5 major complexes were consistently observed using any of the analytical methods. One complex consisted of the tightly related group: Bacteroides forsythus, Porphyromonas gingivalis and Treponema denticola. The 2nd complex consisted of a tightly related core group including members of the Fusobacterium nucleatum/periodonticum subspecies, Prevotella intermedia, Prevotella nigrescens and Peptostreptococcus micros. Species associated with this group included: Eubacterium nodatum, Campylobacter rectus, Campylobacter showae, Streptococcus constellatus and Campylobacter gracilis. The 3rd complex consisted of Streptococcus sanguis, S. oralis, S. mitis, S. gordonii and S. intermedius. The 4th complex was comprised of 3 Capnocytophaga species, Campylobacter concisus, Eikenella corrodens and Actinobacillus actinomycetemcomitans serotype a. The 5th complex consisted of Veillonella parvula and Actinomyces odontolyticus. A. actinomycetemcomitans serotype b, Selenomonas noxia and Actinomyces naeslundii genospecies 2 (A. viscosus) were outliers with little relation to each other and the 5 major complexes. The 1st complex related strikingly to clinical measures of periodontal disease particularly pocket depth and bleeding on probing.

Characterization of a novel N-acetylneuraminic acid-specific Fusobacterium nucleatum PK1594 adhesin

Fusobacterium nucleatum has been identified as significantly associated with sites with active periodontal disease and, as a group, the oral fusobacteria coaggregate with members of all oral bacteria genera tested. Monoclonal antibodies were prepared and used in conjunction with other potential inhibitors, such as simple sugars and amino acids, to characterize coaggregation interactions, of F. nucleatum PK1594. Four unique monoclonal antibodies, 5H11, 14C7, 19F2 and 29C12, were obtained by their ability to inhibit coaggregation of F. nucleatum PK1594 with Actinomyces israelii PK16. They were also capable of inhibiting other coaggregations including Streptococcus oralis H1, S. oralis J22, Capnocytophaga ochracea ATCC33596, Prevotella denticola PK1277 and Prevotella intermedia PK1511. All of these interactions were completely inhibited by N-acetylneuraminic acid. Neither N-acetylneuraminic acid nor monoclonal antibody 5H11 had any inhibitory effect on other F. nucleatum PK1594 interactions, including all galactose-inhibitable coaggregations. The results indicate that F. nucleatum PK1594 expresses upon its surface a distinct type of adhesin that mediates coaggregation interactions that are inhibited by N-acetylneuraminic acid.

Differential effects of systemic metronidazole and amoxicillin on Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis in intraoral habitats

48 adult patients with untreated periodontitis harboring subgingival Actinobacillus actinomycetemcomitans and/or Porphyromonas gingivalis were randomly assigned to receive full mouth scaling alone (control) or scaling with systemic metronidazole plus amoxicillin and supragingivai irrigation with chlorhexidine digluconate (test). Subgingival plaque and swab samples from tongue, tonsils, and buccal mucosa were taken at baseline, 10 days and 3, 6, 9, and 12 months. A. actinomycetemcomitans was detected in the oral cavity, i.e., subgingival plaque and/or mucous membranes, less frequently in test patients compared to controls at 9 and 12 months (p<0.01), whereas, the intraoral detection frequency of P. gingivalis was significantly reduced only 10 days following therapy (p<0.001). At any time after therapy, A. actinomycetemcomitans was not detected intraorally in 5 of 10 (50%) test and 1 of 13 (8%) control patients harboring this pathogen at baseline; P. gingivalis was not detected in only 1 of 18 (6%) test and none of the 17 control patients harboring this pathogen at baseline. Although the data indicated that the assessed antimicrobial therapy may suppress A. actinomycetemcomitans from the entire oral cavity below detectable levels over a minimum of 12 months, P. gingivalis persisted or reoccurred.

Periodontitis patient and the spouse: periodontal bacteria before and after treatment

Suspected periodontal pathogens can be transmitted between spouses. The treatment response may be unsuccessful in periodontitis patients, if the spouse harbors these bacteria. The aim of the present 6-month follow-up study was to clarify whether the microbiological treatment outcome of periodontitis patients is related to the detection of suspected periodontal pathogens in the saliva of the spouse. 10 patients with advanced periodontitis and their spouses were included in the study. The patients received mechanical periodontal treatment and 500 mg metronidazole systemically 2x a day for 7 days. The presence of visible plaque, gingival bleeding after probing, suppuration, supragingival and subgingival calculus and pocket depths were assessed at baseline and 1 and 6 months after treatment. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia/Prevotella nigrescens, Campylobacter rectus and Peptostreptococcus micros were cultured from pooled subgingival samples from the patients and from salivary samples from the spouses at corresponding occasions. Periodontal conditions in the patients improved after treatment as determined by the significantly lower values of clinical variables 1 and 6 months after treatment compared to those at baseline. However, the re-emergence of periodontal bacteria after treatment of the patients was not related to the concurrent detection of the respective bacteria in the saliva of the spouses. In this study design, it seemed that the salivary bacterial load in the spouse was of minor importance for the microbiological treatment outcome of the patient.

Identification of a Fusobacterium nucleatum PK1594 galactose-binding adhesin which mediates coaggregation with periopathogenic bacteria and hemagglutination

Attachment of Fusobacterium nucleatum to various oral surfaces is mediated by several adhesins anchored on its outer surface. Monoclonal antibodies (MAbs) were prepared and used to identify the putative galactose-binding adhesin of F. nucleatum PK1594. Four unique MAbs, 8G7, 26B9, 28G11, and 29D4, were isolated on the basis of their ability to inhibit coaggregation of F. nucleatum PK1594 with Porphyromonas gingivalis PK1924. All four MAbs were also capable of inhibiting galactose-inhibitable interactions of F. nucleatum PK1594 with other oral gram-negative bacteria and with erythrocytes. Preincubation of F. nucleatum PK1594 with MAb 26B9 or its Fab fragments at concentrations lower than 1 microg/ml resulted in complete inhibition of coaggregation with P. gingivalis PK1924 or hemagglutination. F. nucleatum PK1594 surface components prepared by mild sonication or by extracting whole cells with detergents were subjected to Western blot analysis. None of the MAbs were able to recognize any polypeptide in these experiments. Therefore, detergent extracts of F. nucleatum PK1594 surface components were subjected to three experimental procedures: (i) separation by ion-exchange chromatography and testing of fractions for reaction with MAb 26B9 in an enzyme-linked immunosorbent assay (ELISA), (ii) lactose-Sepharose affinity chromatography and testing of the lactose eluate in ELISA with MAb 26B9, and (iii) immunoseparation with either MAb 26B9 or 8G7. Collectively, the results suggest that the putative adhesin is a 30-kDa outer membrane polypeptide which mediates the coaggregation with P. gingivalis PK1924 as well as other galactose-sensitive interactions of F. nucleatum PK1594.

Oral food consumption and subgingival microorganisms: subgingival microbiota of gastrostomy tube-fed children and healthy controls

This study examined the effect of oral food consumption on the prevalence and levels of subgingival bacteria and yeasts in 20 gastrostomy tube-fed children and 24 healthy controls. Microbial identification was carried out using anaerobic culture and 16S rRNA-based PCR identification methods. Streptococcal and Actinomyces species were recovered from 100% and 76% of all subjects and averaged 66% and 11% of total cultivable organisms, respectively. In decreasing order of prevalence, Fusobacterium, enteric rods, Prevotella intermedia/Prevotella nigrescens, Capnocytophaga, Propionibacterium, yeasts, Actinobacillus actinomycetemcomitans, coagulase-negative Staphylococcus, Campylobacter rectus, Bacteroides forsythus, and Porphyromonas gingivalis were detected in 48% to 2% of the study subjects. The cultivable levels of these species varied widely among subjects. PCR detection showed C. rectus and Eikenella corrodens both to occur in 93% of the study subjects and to be the most prevalent putative periodontal pathogens examined. In decreasing order of prevalence, PCR identified Treponema denticola, A. actinomycetemcomitans, P. nigrescens, P. intermedia, B. forsythus, and P. gingivalis in 38% to 21% of the subjects studied. Tube-fed children and healthy controls exhibited similar subgingival microbial compositions. It appears from this study that oral food consumption is not a major determinant for the establishment of subgingival microbiota in children.

Absence of Porphyromonas asaccharolytica, Bacteroides fragilis and Chlamydia pneumoniae in human subgingival plaque

Little is known about the presence of common medical pathogens in the human oral cavity. Using a 16S rRNA-based PCR identification method, this study determined the occurrence of Porphyromonas asaccharolytica, Bacteroides fragilis and Chlamydia pneumoniae in subgingival plaque from 50 adults with advanced periodontitis. Each patient contributed samples from 3 deep periodontal pockets collected by paper points. The PCR primers were for P. asaccharolytica 5'-CTC TAG CTA GAG TGT ACT GG-3' and 5'-ATA GGG TTT ATA GAT TAG CTC TCT-3', for B. fragilis 5'-AAT GAT TCC GCA TGG TTT CAT TA-3' and 5'-GCG GTG ATT GCT CAC TGA CA-3', and for C. pneumoniae 5'- TGA CAA CTG TAG AAA TAC AGC-3' and 5'-CGC CTC TCT CCT ATA AAT-3'. The primers yielded a single amplicon with the respective reference strains and produced no amplicon with colonies of 25 groups of oral organisms. None of the three test species were detected in any of the 50 pooled subgingival samples tested. P. asaccharyolytica, B. fragilis and C. pneumoniae do not seem to be part of the periodontopathic microbiota in humans.

Porphyromonas gingivalis virulence in a murine lesion model: effects of immune alterations

This study utilized various mouse strains with documented alterations in immune system components to assess their contribution to modify the virulence of Porphyromonas gingivalis. P. gingivalis W50 was cultivated on blood agar plates, harvested and used to challenge mice by subcutaneous injection on the dorsolateral surface of the back. Soft tissue lesion development was estimated by measuring the area of the spreading lesion formed by this microorganism over a period of 15 days. Challenge of various normal inbred and outbred mouse strains including: BALB/cN, BALB/cJ, BALB/c nu/+, ICR, B10.A(4R), B10.MBR, A/J, C57BL/6J, CBA/CaH, C.B-17/Icv Tacf DF and C3H/HeN with 2 x 10(10) bacteria showed similar lesion size among these strains (approximately 400 mm2). Genetically deficient mouse strains [C.B-17/Icr Tac (SCID); DBA/2 (C5 deficient); BALB/c nu/nu (T cell deficient); CBA/CaHN-XID/J (B cell deficient) and C3H/HeJ (LPS hyporesponsive)] demonstrated a lesion size which was similar to normal animals. C57BL/6J-BgJ (NK cell deficient) mice exhibited a significantly more severe lesion than the other strains tested. Following healing of the lesions, we initiated a secondary infection of the surviving animals to estimate the acquisition of protective immunity following recovery from the primary infection. Normal mice demonstrated a delayed onset and decrease in lesion size of 15 to 30% compared with the primary infection. In contrast, each of the immunodeficient strains appeared unable to develop immune protection to the secondary challenge. The findings suggest that protection against primary infections with P. gingivalis are mediated by innate immune mechanisms (PMN. NK cells). Additionally, it appears that T-cell-dependent humoral responses are critical to developing immunity to subsequent P. gingivalis infection.

Comparison of the subgingival microbiota of periodontally healthy and diseased adults in northern Cameroon

Our study is the 1st report on subgingival microbiota in adult Cameronians. The aim was to investigate, using the checkerboard DNA-DNA hybridization technique, the prevalence of 18 oral species in subgingival plaque samples obtained from sex- and age-matched Cameronian adults with and without periodontal destruction. We also compared cultivation and the Affirm DP test with the checkerboard technique in their capability to detect some selected species among the 18. 21 adult periodontitis patients and 21 periodontally healthy subjects were examined and the results were compared statistically. Each periodontitis patient had at least 4 pockets of > or = 6 mm depth, while the healthy subjects had no sites more than 3 mm deep. Results of the checkerboard analysis showed that significantly (p < 0.05) more periodontitis patients tested positive for most of the 18 bacterial species. The Gram-positive species Actinomyces naeslundii, Streptococcus mitis and Streptococcus sanguis, known as microbiota of healthy sites, were detected significantly more frequently in the healthy group. Cultivation demonstrated P. gingivalis, B. forsythus, A. actinomycetemcomitans, P. intermedia and F. nucleatum in significantly lower %s of patients as compared to the checkerboard technique. Furthermore, the Affirm DP test detected P. gingivalis and B. forsythus in significantly fewer patients than did the checkerboard technique. A. actinomycetemcomitans was detected in 52.3% of the patients by the latter technique while the Affirm DP test failed to detect the bacterium in any of the samples. Overall, the results of the present study confirm the importance of the screening method and indicate that the prevalences of the investigated putative periodontal pathogens and beneficial species in the healthy and diseased adult Cameronians were similar to those reported for adults in the West and in some developing countries.

Evaluation of oral hygiene products: science is true; don't be misled by the facts

Most people in industrialized countries use oral hygiene products. When an oral health benefit is expected, it is important that sufficient scientific evidence exist to support such claims. Ideally, data should be cumulative derived from studies in vitro and in vivo. The data should be available to the profession for evaluation by publication in refereed scientific journals. Terms and phrases require clarification, and claims made by implication or derived by inference must be avoided. Similarity in products is not necessarily proof per se of efficacy. Studies in vitro and in vivo should follow the basic principles of scientific research. Studies must be ethical, avoid bias and be suitably controlled. A choice of controls will vary depending on whether an agent or a whole product is evaluated and the development stage of a formulation. Where appropriate, new products should be compared with products already available and used by the general public. Conformity with the guidelines for good clinical practice appears to be a useful way of validating studies and a valuable guide to the profession. Studies should be designed with sufficient power to detect statistically significant differences if these exist. However, consideration must be given to the clinical significance of statistically significant differences between formulations since these are not necessarily the same. Studies in vitro provide supportive data but extrapolation to clinical effect is difficult and even misleading, and such data should not stand alone as proof of efficacy of a product. Short-term studies in vivo provide useful information, particularly at the development stage. Ideally, however, products should be proved effective when used in the circumstances for which they are developed. Nevertheless, a variety of variable influence the outcome of home-use studies, and the influence of the variable cannot usually be calculated. Although rarely considered, the cost-benefit ratio of some oral hygiene products needs to be considered.

Porphyromonas gingivalis infection of oral epithelium inhibits neutrophil transepithelial migration

Periodontal diseases are inflammatory disorders caused by microorganisms of dental plaque that colonize the gingival sulcus and, subsequently, the periodontal pocket. As in other mucosal infections, the host response to plaque bacteria is characterized by an influx of polymorphonuclear leukocytes (PMNs) to the gingival crevice. Neutrophil migration through the epithelial lining of the gingival pocket is thought to be the first line of defense against plaque bacteria. In order to model this phenomenon in vitro, we used the oral epithelial cell line KB and human PMNs in the Transwell system and examined the impact of Porphyromonas gingivalis-epithelial cell interactions on subsequent PMN transepithelial migration. We demonstrate here that P. gingivalis infection of oral epithelial cells failed to trigger transmigration of PMNs. Furthermore, it significantly inhibited neutrophil transmigration actively induced by stimuli such as N-formylmethionyl leucyl phenylalanine, interleukin-8 (IL-8), and the intestinal pathogen enterotoxigenic Escherichia coli. The ability of P. gingivalis to block PMN transmigration was strongly positively correlated with the ability to adhere to and invade epithelial cells. In addition, P. gingivalis attenuated the production of IL-8 and the expression of intercellular adhesion molecule 1 by epithelial cells. The ability of P. gingivalis to block neutrophil migration across an intact epithelial barrier may critically impair the potential of the host to confront the bacterial challenge and thus may play an important role in the pathogenesis of periodontal disease.

Clinical and microbiological features of subjects with adult periodontitis who responded poorly to scaling and root planing

In a previous report, it was shown that scaling and root planing (SRP) decreased mean pocket depth and attachment level in subjects with adult periodontitis, as well as the levels and prevalence of Bacteroides forsythus, Porphyromonas gingivalis and Treponema denticola. However, a subset of subjects in that study exhibited mean loss of attachment following SRP. The purpose of the present investigation was to seek clinical and microbiological differences between subjects who responded well or poorly to SRP. 57 subjects with adult periodontitis were treated by full-mouth SRP under local anaesthetic. Clinical assessments of plaque, redness, suppuration, BOP, pocket depth and attachment level were made at 6 sites per tooth prior to and 3 months post-SRP. Attachment level measurements were repeated at each visit and differences in means between visits used to assess change. 18 subjects showed mean attachment loss 3 months post-SRP (poor response group), while 39 showed mean attachment level gain (good response group). The prevalence and levels of 40 subgingival taxa in subgingival plaque samples from the mesiobuccal site of each tooth (maximum 28 sites) in each subject prior to and 3 months post-SRP were assessed using checker-board DNA-DNA hybridization. The prevalence of each species was computed for each subject and averaged across subjects in the 2 treatment-response groups at each visit. Differences between groups were sought using the Mann-Whitney test. There were no statistically significant differences between the 2 response groups in any clinical parameter prior to therapy. Subjects in the good response group showed more attachment level gain at sites with baseline pocket depths of < 4 mm, 4-6 and > 6 mm than poor response subjects. Of 40 species evaluated, A. naeslundii genospecies 2 (A. viscosus), T. denticola, C. gracilis and C. rectus were significantly higher and more prevalent pre-therapy in the good response subjects. Mean attachment level change post SRP could be predicted using multiple linear regression with A. naeslundii genospecies 2 (A. viscosus) and T. denticola as the predictor variables (r2 = 0.373, p < 0.00001). Sites that gained > or = 2 mm of attachment post therapy showed a significant decrease in the counts of P. gingivalis (7.5 +/- 3.5 to 0.2 +/- 0.2 x 10(5)), T. denticola (8.2 +/- 3.5 to 1.8 +/- 1.1 x 10(5)) and B. forsythus (11.1 +/- 5.7 to 0.3 +/- 0.2 x 10(5)). The data of the present investigation indicate that SRP is most effective in subjects and sites with high levels of the subgingival species that this therapy affects.

The optimization of the BANA test as a screening instrument for gingivitis among subjects seeking dental treatment

Porphyromonas gingivalis, Treponema denticola and Bacteroides forsythus have been implicated in periodontal disease and each possesses an enzyme capable of hydrolyzing the synthetic trypsin substrate, BANA. We have used a chairside test for BANA hydrolysis to diagnose an anaerobic periodontal infection in patients with advanced forms of clinical disease using a 15-min/55 degrees C incubation protocol. However, the BANA test performance is dependent upon the length and temperature of incubation. In the present study, we have evaluated a 5-min/35 degrees C, a 5-min/55 degrees C and a 15-min/55 degrees C incubation protocol to determine whether the performance of the BANA test could be optimized using plaque samples obtained from subjects seeking dental treatment. Logistic regression models were tested with age, smoking status, and gingivitis scores as covariates. The best fitting model obtained with the 5-min/35 degrees C protocol had a sensitivity of 71%, a specificity of 68%, a false-positive proportion of 9%, a false-negative proportion of 65%, and an overall accuracy of 80%. When maximum likelihood estimates were obtained in this model, plaques from individuals who reported that they currently smoked were 9.57x, and those who quit smoking were 4.73x more likely to have a positive BANA score than someone who never smoked. Plaques were 4.55x more likely to be BANA-positive if they were removed from sites with gingivitis. These findings indicate that the performance of the BANA test is best using the 5-min/35 degrees C incubation protocol.

Estimation of serum antibody to subgingival species using checkerboard immunoblotting

Measurement of serum antibody to subgingival bacterial species has been useful in discriminating possible periodontal pathogens and in assessing the host's immune response to subgingival species. An immunoassay system was developed to measure the level of serum antibody to multiple subgingival species in multiple serum samples on a single nitrocellulose membrane. The principle steps of the assay are the following: 1) binding of antigens from bacterial preparations and protein A in parallel lanes on nitrocellulose membranes; 2) incubation of known concentrations of human immunoglobulin as well as various dilutions of serum from patients in lanes perpendicular to the antigen lanes; 3) incubation of the membrane with a peroxidase-conjugated second antibody; 4) detection of positive reactions by enhanced chemiluminescence. Emitted light was captured on a photographic film in which the positive reactions appeared as squares at the intersections of antigens with appropriate antibody. Antibody was quantified using a laser densitometer to compare the signal intensity of unknown samples with the ones generated by known amounts of human immunoglobulin captured on the same membrane. The assay permitted simultaneous screening and/or quantification of antibody in as many as 45 serum samples against up to 45 bacterial species. The mean and standard error of the coefficients of variation for replicates within an assay averaged 7.3 +/- 2.3%. Coefficients of variation of the assay run on different days for serum antibody to a range of subgingival species averaged 10.1 +/- 2.1%. Checkerboard immunoblotting is a simple and rapid immunoassay to permit quantification and/or screening of antibody to multiple subgingival species or antigens in multiple serum samples.

Scanning electron microscopy of microbial colonization of 'rapid' and 'slow' dental-plaque formers in vivo

The aim was to investigate the morphological features of supragingival plaque development in 'rapid' and 'slow' plaque formers using scanning electron microscopy (SEM). Forty-nine healthy volunteers were screened for their plaque-formation rate after 3 days of oral hygiene abstinence using the Plaque Index (PI). Five with the highest and six with the lowest mean PI were selected as 'rapid' and 'slow' plaque formers, respectively. Six enamel blocks measuring 2 x 2 x 1 mm were bonded onto the buccal surfaces of the upper left canine, premolars and first molar of each selected participant after a series of prophylaxes and oral hygiene instruction to ensure clinical gingival health. A 14-day period with no oral hygiene began thereafter. An enamel block was removed at 3 hr, 6 hr, 1 day, 3 days, 7 days and 14 days from each individual, fixed, and processed for SEM. Quantitatively, more bacteria were observed on the 3-hr to 1-day enamel blocks of the 'rapid' plaque formers. The day-1 specimens of the 'rapid' group showed a more complex supragingival plaque structure than those of the 'slow' group. From days 3 to 14, during the maturation period of supragingival plaque, there were no discernible differences between the two groups except that intermicrobial matrix was more prominent in the 'rapid' group. In general, the development of supragingival plaque followed known patterns. These observations indicate that morphological features of supragingival plaque in 'slow' and 'rapid' plaque formers differ, especially in the early developmental phases.

Therapy-resistant periodontitis (I). Clinical and treatment characteristics

The aim of this study was to evaluate the clinical criteria for classification of 2 different patient groups. From retrospective comparisons of pocket probing depth (PPD) charts, we classified 22 patients as either non-responding or responding to periodontal treatment. The non-responding patient group, in comparison with the responding patient group, showed a profile over time of less PPD reduction in response to periodontal treatment. Information registered in each patient's file regarding clinical periodontal conditions, as well as treatment procedure characteristics, was gathered. Bivariate analyses were performed. 3 clinical variables (frequency of mean PPD > or = 6 mm during the treatment period; at final registration; and the mobility score at the final registration) indicated that 2 separate patient groups had been identified. Although the patient groups exhibited advanced periodontitis at the beginning of treatment, both groups at the end of treatment had lost very few (1-2) teeth, probably as a result of regular supportive treatment. The characteristics of the selected clinical criteria warrant the use of these 2 patient groups in further analysis of the relation of psychosocial stress and microbiological characteristics of therapy-resistant periodontitis.

Therapy-resistant periodontitis (II). Compliance and general and dental health experiences

In this exploratory case-control study, somatic and psychological factors are used for exploring whether the anamnestic information gives support to the hypothesis of a relationship between therapy-resistant periodontitis and stress factors. From retrospective comparisons of pocket probing depth charts, we classified 22 patients as either non-responding or responding to periodontal treatment. The non-responding patient group, in comparison with the responding patient group, showed a profile over time of less pocket probing depth (PPD) reduction in response to periodontal treatment. Information registered in each patient's file regarding periodontal registrations and dental status was gathered, and an interview was conducted aiming at collecting information on dental experiences and attitudes. Bivariate and logistic multivariate regression analyses were performed. The NR-group patients experienced significantly more unpleasant feelings towards dental procedures and a higher tendency to experience pain in connection with dental procedures. This group was found to start smoking at an older age than the R-group. One reason for this may be that smoking debut at an older age is more related to stress conditions than debut at a younger age. The report highlights the possible contribution of stress factors in periodontal disease.

Activation of the interleukin-1beta precursor by Treponema denticola: a potential role in chronic inflammatory periodontal diseases

There are several indications suggesting that interleukin-1beta (IL-1beta) may play an important role in inflammatory periodontal diseases. We hypothesized that periodontal sites would represent a unique combination of both cellular sources of IL-1beta precursor (pro-IL-1beta) and microbial proteases and proposed that Treponema denticola, a suspected periodontal pathogen, would play a critical role in the inflammatory nature of adult chronic periodontitis by activating pro-IL-1beta. The aim of this study was thus to demonstrate the proteolytic cleavage and activation of the inactive precursor pro-IL-1beta by T. denticola. After incubation of bacterial cells with recombinant pro-IL-1beta, proteolytic cleavage was monitored by Western immunoblotting, and the biological activity of the digestion products was tested in a bioassay. We report here that T. denticola can cleave pro-IL-1beta to yield two fragments with molecular masses of 18 and 19 kDa. Cleavage products showed a dose-dependent biological activity in the thymocyte proliferation bioassay, and this activity was inhibited by anti-IL-1beta neutralizing antibodies. These results suggest that T. denticola may have a proinflammatory role in periodontal diseases.

Microbial ecology of Actinobacillus actinomycetemcomitans, Eikenella corrodens and Capnocytophaga spp. in adult periodontitis

Information on intraoral distribution of putative periodontal pathogens might be essential for controlling different forms of periodontal disease. Colonization may be either promoted or impeded by other bacteria competing in the subgingival ecosystem. In recent investigations microbial associations between dental organisms have been determined in a multitude of subgingival plaque samples within multiple patients and described by odds ratios, in most circumstances without taking into account the correlated structure of the observations within a single individual. The present investigation had 3 major objectives: (i) to describe the intraoral distribution of some facultatively anaerobic, Gram-negative rods, i.e. Actinobacillus actinomycetemcomitans, Eikenella corrodens-like organisms and Capnocytophaga spp., in a multitude of subgingival and extracrevicular samples of 10 adult subjects with A. actinomycetemcomitans-associated periodontitis; (ii) to analyse possible inconsistencies of microbial associations between these periodontal organisms; and (iii) to determine factors increasing the likelihood of isolating these bacteria in a given subgingival site by employing Generalized Estimation Equation (GEE) methods. Clinical examinations were carried out at 6 sites of every tooth present. In each subject, 13 extracrevicular (2 cheek mucosa, 3 tongue, 4 gingival, 2 tonsillar samples, 1 palatinal, 1 saliva sample) and between 22 and 44 subgingival samples from deepest sites of every tooth present (n = 296) were selectively cultivated for A. actinomycetemcomitans, E. corrodens and Capnocytophaga spp. In extracrevicular material, A. actinomycetemcomitans, Capnocytophaga spp. and E. corrodens were isolated in 9, 10 and 6 patients, and from 65, 82 and 15% samples, respectively. The organisms were recovered from 51, 62 and 27% subgingival plaque samples, respectively. Heterogeneity tests did not reveal significant inconsistencies of microbial associations between bacteria in subgingival plaque. Mantel-Haenszel's odds ratios ranged between 2.0 for A. actinomycetemcomitans and Capnocytophaga spp. and 18.7 for Capnocytophaga spp. and E. corrodens. An exchangeable working dependence structure was employed in the GEE approach. The odds of isolating A. actinomycetemcomitans was increased by factor 3.7 in 4-6 mm deep pockets, and 9.5 in > or = 7 mm deep pockets. The odds of presence of E. corrodens was increased by factor 10.8 in the case of presence of Capnocytophaga spp. and 2.1 in the case of presence of A. actinomycetemcomitans. Capnocytophaga spp. were associated with bleeding on probing and molar sites. Presence of E. corrodens was associated with clinical attachment loss but not periodontal probing depth. Results of the present study indicated an association of A. actinomycetemcomitans with periodontal pathology. Whereas this organism and Capnocytophagae were widely distributed in extracrevicular ecosystems of the mouth, E. corrodens only occasionally appeared in saliva or on mucous membranes of the oral cavity. In general, GEE methods seem to allow to determine factors associated with the presence of periodontal organisms in a multivariate approach and considering the correlated structure of the data.

beta-Lactamase producing bacteria in adult periodontitis

In 23 untreated adult periodontitis patients, the occurrence of beta-lactamase producing periodontal bacteria was determined. In addition to non-selective isolation media, selective isolation and growth of beta-lactamase positive subgingival bacterial species was carried out on blood agar plates supplemented with amoxicillin and plates with amoxicillin+clavulanic acid. Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans, Peptostreptococcus micros, Fusobacterium nucleatum, Bacteroides forsythus and Campylobacter rectus isolates from the non-selective medium were tested for beta-lactamase activity by a nitrocefin disk method (DrySlide) and by a laboratory chromogenic nitrocefin-based test. Isolates from the amoxicillin plates that were absent on the amoxicillin/clavulanic acid plates were identified and tested for beta-lactamase production. Based on the non-selective plates, six of 23 P. intermedia isolates, 2 of 19 B. forsythus isolates and 3 of 23 F. nucleatum isolates were beta-lactamase positive. The beta-lactamase positive species Prevotella loescheii, Prevotella buccae, Prevotella buccalis and Actinomyces spp were recovered from the selective amoxicillin plates. beta-Lactamase positive subgingival species were recovered from 17 of 23 patients (74%) but usually comprised low proportions of the subgingival microbiota (range < 0.01-15%). Comparison of the DrySlide test and the nitrocefin-based laboratory test revealed full agreement of test results. beta-Lactamase activity in whole subgingival plaque was detected in 12 patient samples (52%). It was concluded that beta-lactamase activity in subgingival bacteria in adult periodontitis is a common feature. However, since the majority of the samples showed only low-level enzymatic activity, the clinical relevance of this observation with regard to therapy with unprotected enzyme-susceptible beta-lactams is uncertain, though failure on the other hand, is difficult to rule out when a mechanism of resistance is present. The majority of beta-lactamase positive strains was found among species of the Prevotella genus.

Evidence for serum immunoglobulin G (IgG) antibody responses in Macaca fascicularis identified by monoclonal antibodies to human IgG subclasses

This investigation determined the capacity of murine monoclonal antibodies directed to human immunoglobulin G (IgG) subclasses to identify molecules with conserved epitopes in the serum of the nonhuman primate, Macaca fascicularis. We subsequently utilized this cross-reactivity to document the characteristics of IgG subclass antibody responses in M. fascicularis to parenteral immunization with intact oral microorganisms, antigens from oral microorganisms, and finally a defined protein toxin, tetanus toxoid. The IgG response in nonhuman primates immunized with tetanus toxoid showed a 40-fold and 110-fold increase after primary and secondary immunizations, respectively. The major IgG subclass responses were IgG1 and IgG3, with little, though significant, responses in the IgG4 and IgG2 subclasses. Seventy-five to 94% of the natural IgG antibody in nonhuman primate sera to Porphyromonas gingivalis, Prevotella intermedia and Campylobacter rectus was IgG1. IgG2 and IgG3 predominated to Bacteroides fragilis, IgG4 to Actinomyces viscosus and an equal distribution among the subclasses was noted in response to Fusobacterium nucleatum. Parenteral immunization of nonhuman primates with intact P. gingivalis elicited primarily IgG3 and IgG4, while the post-immunization IgG response to P. intermedia was largely IgG1. Nonhuman primates were also parenterally immunized with cell envelope antigens of P. gingivalis, P. intermedia, or a combination of cell envelope antigen from C. rectus and F. nucleatum and cell wall antigens of A. viscosus. The greatest IgG antibody response seen post-immunization was reactive with anti-human IgG1 for all of these antigens except to C. rectus which bound nonhuman primate antibody reactive with anti-human IgG2. It appears that the bacteria and their products exhibit unique differences in their induction of serum IgG subclass antibody responses. The characteristics of their immunogenicity as detected by the nonhuman primate may contribute to the ability of the immune responses to effectively interact with these pathogens.

Subgingival microbiota in adult Chinese: prevalence and relation to periodontal disease progression

The "checkerboard" Dna-Dna hybridization technology was used to study the epidemiology of 18 microbial species associated with various states of periodontal health and disease, in a sample of 148 Chinese subjects never exposed to systematic dental therapeutic intervention, aged 30 to 39 and 50 to 59 years. Our aims were to: 1) describe the prevalence of these microorganisms; 2) correlate the microbiological and clinical profiles of the subjects; and 3) examine the association between the microbiological variables and the longitudinal changes of periodontal status that occurred over a preceding 10-year period. A maximum of 14 subgingival samples were obtained from each subject-1,864 in all. The frequency of occurrence of the 18 species examined was high in this Chinese population, on both the subject and the tooth site level. However, all species were not found equally capable of reaching high numbers in the subgingival samples and, as a rule, colonized heavily only limited proportions of tooth sites within each mouth. There was a profound increase of certain species such as Porphyromonas gingivalis, Treponema denticola, and Bacteroides forsythus in deep pockets or progressing sites. Multivariate techniques using the subgingival profile could effectively discriminate between deep/shallow pockets and progressing/ stable tooth sites. The microbiological variables showed an enhanced discriminating potential when classifications were performed on the individual subject level. Colonization by P. gingivalis, B. forsythus, Campylobacter rectus, and T. denticola at levels exceeding certain thresholds entailed a significantly increased probability (odds ratios > 4) for an individual subject to harbor deep pockets or progressing tooth sites.

Host modulation of tissue destruction caused by periodontopathogens: effects on a mixed microbial infection composed of Porphyromonas gingivalis and Fusobacterium nucleatum

These studies determined the ability of selected periodontopathogens to synergistically initiate soft tissue destruction in a murine abscess model. The development of immunity following recovery from infection or by active immunization was also examined. Mice were infected with P. gingivalis W50, F. nucleatum T18, or a combination of the two microorganisms. F. nucleatum caused only a localized lesion in contrast to P. gingivalis which caused a spreading suppurative inflammatory lesion of the skin and subcutaneous tissues, which, depending upon the dose, could result in death. Infection of mice with a combination of P. gingivalis and F. nucleatum elicited a significantly greater lesion size (P<0.001) and lethality compared with P. gingivalis alone. Mice infected with a subclinical dose (no visible lesion) of P. gingivalis failed to develop protective immunity to a secondary P. gingivalis challenge. Mice that had recovered from P. gingivalis lesions demonstrated partial protection against subsequent P. gingivalis challenge; however, the immunity was less protective against the mixed F. nucleatum + P. gingivalis infection. Active immunization with P. gingivalis protected against both the P. gingivalis and F. nucleatum + P. gingivalis challenges and this protection was correlated with the levels of specific serum immunoglobulin G (IgG) antibody. The results indicated that the murine model is ideally suited to examine bacterially-mediated mixed infections that result in soft tissue destruction. This destruction can be minimized, but not abrogated, with development of immunity. Challenge with sufficient numbers of the pathogens can overwhelm the acquired immunity.

PCR-DNA probe assays for identification and detection of Prevotella intermedia sensu stricto and Prevotella nigrescens

The purpose of this study was to construct PCR-DNA probe assays specific for Prevotella intermedia sensu stricto and Prevotella nigrescens based on the ability of randomly amplified polymorphic DNA (RAPD) fingerprinting to generate species-specific markers. The strategy included four steps: (i) construction of first-generation DNA probes from a 850-bp RAPD marker for P. intermedia sensu stricto and a 1,300-bp RAPD marker for P. nigrescens, (ii) cloning and sequencing of each RAPD marker, (iii) designing of primer pairs flanking specific internal sequences of 754 bp for P. intermedia sensu stricto and of ca. 1,100 bp for P. nigrescens, and (iv) synthesis (by PCR amplification) and digoxigenin labeling of quantities of DNA probes 754 and ca. 1,100 bp in size. The PCR-DNA probe assays combine either PCR amplification of a 754-bp specific sequence in the genomic DNA of strains of P. intermedia sensu stricto and hybridization with the 754-bp digoxigenin-labeled probe or amplification of a ca. 1,100-bp sequence of P. nigrescens and hybridization with the ca. 1,100-bp probe. Specific hybridization was observed with the amplified DNAs from 25 strains of P. intermedia and 24 strains of P. nigrescens, and no reaction was observed with the PCR products from 20 foreign species. The PCR-DNA probe assays described here should allow a highly specific and sensitive detection of P. intermedia sensu stricto and P. nigrescens in mixed infections.

Characterization of Bacteroides forsythus isolates

Fifteen Bacteroides forsythus strains freshly isolated from patients with periodontitis were used together with three collection strains and one type strain for characterization of growth on various media; determination of enzymatic profiles, antibiotic susceptibility profiles, 16S rRNA ribotypes, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) outer membrane protein profiles, and pathogenicity; and gas chromatography analysis by using a wound chamber model in rabbits. All strains were stimulated by N-acetylmuramic acid, while one strain needed a further supplement such as yeast extract for optimal growth. All strains showed trypsin-like activity. While 10 different ribotypes were found, the SDS-PAGE profiles revealed similar patterns for all strains. All strains were sensitive to penicillin G (MICs, <0.5 microg/ml), ampicillin (MICs, <1.0 microg/ml), amoxicillin (MICs, <0.38 microg/ml), metronidazole (MICs, <0.005 microg/ml), tetracycline (MICs, <0.19 microg/ml), doxycycline (MICs, 0.05 microg/ml), erythromycin (MICs, <0.4 microg/ml), and clindamycin (MICs, <0.016 microg/ml), while they were less sensitive to ciprofloxacin (MICs, <4 microg/ml). B. forsythus did not cause abscess formation by monoinoculation. B. forsythus coinoculated with Fusobacterium nucleatum ATCC 10953 caused abscess formation in 75% of rabbits, while it caused abscess formation in 100% of rabbits when it was coinoculated with Porphyromonas gingivalis FDC 381. In the case of the latter combination, four of six rabbits died of sepsis after 6 to 7 days, and P. gingivalis and B. forsythus were recovered from the heart blood at a proportion of 10:1. B. forsythus strains were highly virulent and invasive in combination with P. gingivalis.

The influence of anatomic and iatrogenic root surface characteristics on bacterial colonization and periodontal destruction: a review

PERIODONTITIS IS A MULTIFACTORIAL infectious disease affecting primarily a subset of subjects and a subset of sites. Recent microbiological data have acknowledged that before disease progression can occur, a susceptible host and site are required, in addition to the presence of pathogenic bacteria. This review discusses factors affecting periodontal disease progression and focuses in particular on the influence of anatomic and iatrogenic root surface characteristics. Retrospective studies clearly suggest a strong association between anatomic aberrations and periodontal attachment loss. Cemental tear seems to have the potential to initiate an aseptic, rapid, site-specific periodontal breakdown in a non-infected environment, illustrating the complexity of the attachment loss process. Recent experimental findings, furthermore, demonstrate a significant influence of root surface instrumentation roughness upon subgingival plaque formation and gingival tissue reactions, as well as a significant and positive relationship between subgingival plaque accumulation and inflammatory cell mobilization. These results indicate that subgingivally located irregularities may form stagnant sites or ecological niches which favor both retention and growth of organisms. Such events in addition to the progressive inflammatory changes may critically influence the subgingival environment by turning a stable site into an unstable or active periodontitis site. Thus, local anatomic and iatrogenic root surface characteristics may have a more profound effect on gingival health than previously assumed, particularly on a site level.

Environmental regulation of fimbrial gene expression in Porphyromonas gingivalis

Porphyromonas gingivalis fimbriae are an important virulence factor involved in attachment and invasion. Fimbrillin, encoded by the fimA gene, is the major subunit protein of the fimbriae. To elucidate the influence of environmental signals on the expression of the fimA gene, a strain of P. gingivalis (designated PLE) containing a chromosomal transcriptional fusion between a promoterless lacZ gene and the fimA promoter region was constructed. Promoter activity was assessed by measurement of beta-galactosidase activity of PLE. An 11-fold increase in activity of fimA promoter was found as growth temperature declined from 39 to 34 degrees C. Promoter activity decreased by approximately 50% in response to hemin limitation and upon culture on solid medium. In addition, the presence of serum or saliva in the growth medium decreased fimA promoter activity by similar amounts. A correlation between fimA promoter activity and phenotypic properties dependent upon fimbriae was established. P. gingivalis grown at 34 degrees C, compared to 39 degrees C, showed an increased ability to adhere to Streptococcus gordonii and to invade primary cultures of gingival epithelial cells. These studies indicate that expression of the P. gingivalis fimA gene is regulated at the transcriptional level in response to several environmental conditions and that altered fimA expression can also modulate the adherence and invasion abilities of P. gingivalis.

Bacterial transmission in periodontal diseases: a critical review

This review paper addresses intra- and extra-familial transfer of bacteria associated with periodontal diseases. Recent advances in molecular biology provide sensitive methods to differentiate organisms within the same species, thereby facilitating tracking routes of their transmission. Evidence for the passing of microorganisms between parents and children is particularly strong. In this regard, molecular genetic techniques have demonstrated that if a child is colonized by a potentially pathogenic species, then one of the parents will usually harbor genotypically identical bacteria. The data also indicate that transfer of bacteria between spouses occur, but it appears to happen infrequently. Saliva appears to be a major vector for bacterial transmission. However, the transfer of organisms does not necessarily result in colonization or infection of the host. Furthermore, individuals who harbor putative pathogens frequently do not manifest any signs of periodontal disease. This is attributed to host defenses, bacterial antagonism, and possibly lack of pathogenicity of infecting organisms. It is concluded, based upon current evidence, that periodontal pathogens are communicable; however, they are not readily transmissible.

Release and activation of human neutrophil matrix metallo- and serine proteinases during phagocytosis of Fusobacterium nucleatum, Porphyromonas gingivalis and Treponema denticola

The phagocytic ingestion of reference strains and clinical isolates of Fusobacterium nucleatum, Porphyromonas gingivalis, and Treponema denticola by polymorphonuclear leukocytes (PMNs) and the concomitant release of PMN granule proteinases were studied by specific functional and immunological assays. PMNs were incubated with the microorganisms anaerobically at 37 degrees C for indicated time periods. The suspensions and pellets were used for phagocytic ingestion assay and electron microscopic study, respectively. The supernatants were used for the measurements of the amounts and activities of the released PMN enzymes including PMN gelatinase (MMP-9), collagenase (MMP-8), serine proteases (elastase and cathepsin G), and lactate dehydrogenase (LDH). Both fluorescence microscopy and transmission electron microscopy showed that F. nucleatum, P. gingivalis and T. denticola were ingested by the PMNs in comparable numbers. However, measurements of the enzymes released from the triggered PMNs revealed major differences among the three species. High amount of elastase was released from the PMNs triggered by F. nucleatum, but not by P. gingivalis or T. denticola. The treatment of PMNs with P. gingivalis whole cells resulted in the release of gelatinase partly in the 82 kD active form, suggesting proteolytic activation of the degranulated 92 kD proMMP-9. The 82 kD active form of gelatinase was not detected upon triggering the PMNs with F. nucleatum and T. denticola. The PMN-bacteria interaction did not result in release of LDH from triggered PMNs indicating the proteinase release was not due to the PMN cell death. The results show that the susceptibilities of the 3 potentially periodontopathogenic microorganisms, F. nucleatum, P. gingivalis and T. denticola to phagocytic ingestion are not directly related to the amounts and activities of PMN enzymes released during the bacteria-PMN interactions. As PMN degranulation is considered as one of the major pathogenic mechanisms in periodontitis, the observed differences among the microorganisms may be important virulence characteristics of these species.

Bacterial metabolites sodium butyrate and propionate inhibit epithelial cell growth in vitro

The structural and functional barrier preventing the free advancement of microbial plaque subgingivally along the tooth surface is formed by the junctional epithelial (JE) cells directly attached to the tooth (DAT cells). The mechanism leading to degeneration of the DAT cells is not known. In the present study we examined the possible role of short chain fatty acids (SCFAs) on epithelial cells by making use of 2 epithelial cell cultures (HaCaT and ERM) and an explant culture model of human JE. The SCFAs butyrate and propionate were used in concentrations found in human plaque and gingival crevicular fluid (0.25-16.0 mM). The SCFAs had no effect on primary cell adhesion nor on the epithelial attachment apparatus (EAA). By contrast, even 0.25 mM of butyrate significantly retarded epithelial cell growth. Similar effects with propionate were first observed at concentrations higher than 1.0 mM. The retardation of epithelial cell growth was found to be due to inhibition of cell division. Furthermore, after butyrate treatment dense accumulations of intermediate filaments and cytoplasmic vacuolization were characteristically seen in cells adjacent to cells of normal appearance. This suggests that some cells of the growing epithelial cell population are more sensitive to the SCFAs than others, and agrees with previous reports on the DAT cells of periodontally-involved teeth in vivo. The results suggest that SCFAs are microbial factors that play a role in the initiation and progression of periodontal pocket formation by impairing epithelial cell function rather than having a direct effect on the EAA.

Prevalence of suspected periodontal pathogens identified using ELISA in adolescents of differing ethnic origins

The aim of this study was to determine the prevalence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia in a group of adolescents and investigate the association of these organisms with various clinical parameters. A total of 527, 11-13-year-old children, of whom 333 (63%) were white Caucasian, 187 (35%) Indo-Pakistani and 7 (1%) Afro-Caribbean, participated in the study. Subgingival plaque samples, collected from the mesio-buccal of both upper first permanent molars using sterile paper points, were stored in phosphate buffered saline with 0.01% thiomersal and analysed for the presence of A. actinomycetemcomitans, P. gingivalis and P. intermedia using ELISA. The mesio-buccal sites of both upper 1st permanent molars were also examined and the presence/absence of supragingival plaque, subgingival calculus, bleeding on probing and pocket depths greater than 3 mm were recorded. The % of white Caucasian children in whom the monoclonal antibody identified at least 1 site with A. actinomycetemcomitans, P. gingivalis and P. intermedia were 4%, 3% and 2%, respectively, and for Indo-Pakistanis were 3%, 17% and 2%. The difference for P. gingivalis was statistically significant (p < 0.001). The associations between the clinical parameters and the 3 organisms were considered separately for both upper first molar sites. The prevalence of P. gingivalis was higher for sites with subgingival calculus, pockets > 3 mm and bleeding on probing (p < 0.01).

Design principles and statistical considerations in periodontal clinical trials

Although clinical trials are a small subset of conducted biomedical research, they have become powerful investigational tools for the evaluation and approval of new treatments by clinician groups and regulatory agencies like the US Food and Drug Administration. To impact the delivery of care, trials in general must meet three criteria: clarity, comparability, and generalizability. Accordingly, trials can offer meaningful data if they have procedures which are well defined and subjects who represent a reasonably homogeneous population. The evaluation of periodontitis interventions presents several challenges due to the disease's heterogeneity and its irregular, episodic pattern; nevertheless, the intent of these novel interventions is to prevent, diagnose, inhibit, or reverse periodontal disease progression. Careful consideration of the trial's objectives should dictate clinical endpoints (primary and surrogate), comparison groups (placebo, standard therapy, test therapy), and equivalence versus superiority as the basis for conclusions. Several design elements such as control population specification, randomization, masking, sample size calculation, and standardization of procedures for patient care and assessment can decrease potential bias and variability. In both parallel and paired (split-mouth) design trials, multiplicities of endpoints, treatments, and subgroups require strategies which address the broader scope of chance findings without excessive loss of study power. Also, the longitudinal assessment of multiple periodontal sites within patients produces correlated data structures for which analytic methods need to account for the appropriate sampling unit. With these design and analytic elements, clinical trials can provide important evidence to investigators, patients, and governmental agencies for the introduction of novel interventions in periodontal practice.

The nature of periodontal diseases

Periodontal diseases are infections. They have a number of properties in common with infections in other parts of the body, but have unique features resulting from the passage of the tooth through the soft tissue integument into the oral cavity. The tooth provides a solid, non-shedding surface for the colonization of potentially pathogenic bacterial species as well as a wide range of host-compatible species. Periodontal pathogens frequently colonize the periodontal area for prolonged periods of time prior to disease initiation. Disease is caused by a finite set of bacterial species leading to the development of multiple periodontal diseases. Disease occurs at individual periodontal sites and leaves an historical record of the damage to the periodontium in the form of periodontal attachment or bone loss. This feature provides difficulty in investigation since it is often unclear whether the infectious process is presently occurring or is a reflection of past destruction. Control of periodontal diseases is most effectively performed by eliminating or suppressing the organisms that cause them and establishing a host compatible microbiota. When tissue damage has been extensive, regenerative or replacement procedures should be instituted after the infection has been controlled.

Rapid diagnosis of periodontal infections: findings in AIDS patients

A small number of bacterial pathogens in the human oral cavity cause the different forms of periodontal disease. Of the approximately two hundred different oral bacterial species, about a dozen have been associated with these diseases including localized juvenile periodontitis, rapidly progressing periodontitis, and adult periodontitis. These species include Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Campylobacter rectus, Porphyromonas gingivalis, and Prevotella intermedia. Several rapid methods have been developed to detect these species in clinical samples. These include immunologic methods such as immunofluorescence, nucleic acid assays such as DNA-DNA hybridization in dot blots and enzyme assays. Immunofluorescence microscopy has been used to determine the prevalence and relative proportions of these pathogens in dental plaque samples from 194 subjects including HIV-infected and uninfected male homosexuals and intravenous drug users.

Short-chain carboxylic-acid-stimulated, PMN-mediated gingival inflammation

This communication reviews the effects of short-chain carboxylic acids on human cells of importance to the periodontium. The central hypothesis is that these acids can alter both cell function and gene expression, and thus contribute to the initiation and prolongation of gingival inflammation. Short-chain carboxylic acids [CH3-(CH2)x-COOH, x < 3] are metabolic intermediates with a broad range of apparently paradoxical biological effects. For example, lactic acid (CH3-CHOH-COOH), a 3-carbon alpha-hydroxy-substituted acid, is widely recognized for its cariogenicity. Lactic acid, however, also occurs in tropical fruits, and is the active ingredient in a variety of anti-wrinkle creams developed by dermatologists. In marked contrast, the unsubstituted 3-carbon propionic acid (CH3-CH2-COOH) is used as a food preservative and is the active principle for one class of non-steroidal anti-inflammatory agents. Interestingly, the addition of one carbon to propionic acid dramatically changes the biological effects. The unsubstituted 4-carbon butyric acid (CH3-CH2-CH2-COOH) is used by hematologists as a de-differentiating agent for the treatment of sickle cell anemia, but by oncologists as a differentiating agent for cancer chemotherapy. Finally, acting either individually or in concert, these acids can increase vascular dilation. Clearly, these acids, while metabolically derived, have a number of very divergent activities which are cell-type-specific (Fig. 1). It may be telling that periodontal bacteria produce these acids in millimolar concentrations, and that these bacteria can be characterized by their acid production profiles. It is no less interesting that these acids occur in the gingival crevices of human subjects with severe periodontal disease at millimolar levels which are > 10-fold higher than those found in mildly diseased subjects, and are undetectable in healthy subjects. Further, when applied directly to healthy human gingiva, short-chain carboxylic acids stimulate a gingival inflammatory response and inflammatory cytokine release. At the cellular level, these acids inhibit proliferation of gingival epithelial and endothelial cells, and inhibit leukocyte apoptosis and function, but can stimulate leukocyte cytokine release. At the molecular level, these acids can stimulate neutrophil gene transcription, translation, and protein expression. Thus, the likelihood is high that these acids, in addition to their cariogenic activity, can promote and prolong gingival inflammation. Our challenge will be to identify the cell or cells of the periodontium which respond to short-chain carboxylic acids, to delineate their responses and the molecular mechanism(s) of these effects, and to categorize the aspects of the inflammatory components which damage and those which protect the host. With this information, it may be possible to begin to rationally identify and test pharmaceutical agents which diminish the harmful aspects, while enhancing the beneficial components, of the inflammatory response.

Short-chain carboxylic acid concentration in human gingival crevicular fluid

Short-chain carboxylic acids (e.g., lactic acid, propionic acid, butyric acid) are metabolic by-products of bacterial metabolism which can accumulate in the gingival crevice. It is of no small consequence, therefore, that 1- to 5-mM concentrations of these acids exhibit significant biological activity, including the ability to alter cell proliferation and gene expression in cells of importance to the periodontium. This communication reports on the in vivo concentrations of propionic and butyric acid in the gingival crevices of periodontal subjects with severe and mild disease. The results indicated that severely diseased subjects exhibited a > 10-fold increase in the mM concentration of these acids when compared with mildly diseased subjects (mean propionic acid-severe = 9.5 +/- 1.8 mM, and mild = 0.8 +/- 0.3 mM; mean butyric acid-severe = 2.6 +/- 0.4 mM, and mild = 0.2 +/- 0.04 mM). These differences (mean +/- SE) were significant (p < 0.0001). The propionic and butyric acid concentrations were below detection limits in healthy sites of mildly diseased subjects. The propionic and butyric acid concentrations also associated significantly with clinical measures of disease severity (e.g., pocket depth, attachment level) and inflammation (e.g., subgingival temperature, % of sites bleeding when probed), and with the total microbial load (all p < 0.05). Taken together, these data suggest that short-chain carboxylic acids play a mediating role in periodontal disease pathogenesis.

The interleukin-1 genotype as a severity factor in adult periodontal disease

Although specific bacteria, dental plaque, and age are associated with periodontal disease, there are currently no reliable predictors of periodontitis severity. Studies in twins have suggested a genetic contribution to the pathogenesis of periodontitis, but previous attempts to identify genetic markers have been unsuccessful. The pro-inflammatory cytokines interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) are key regulators of the host responses to microbial infection. IL-1 is also a major modulator of extracellular matrix catabolism and bone resorption. We report a specific genotype of the polymorphic IL-1 gene cluster that was associated with severity of periodontitis in non-smokers, and distinguished individuals with severe periodontitis from those with mild disease (odds ratio 18.9 for ages 40-60 years). Functionally, the specific periodontitis-associated IL-1 genotype comprises a variant in the IL-1B gene that is associated with high levels of IL-1 production. In smokers severe disease was not correlated with genotype. In this study, 86.0% of the severe periodontitis patients were accounted for by either smoking or the IL-1 genotype. This study demonstrates that specific genetic markers, that have been associated with increased IL-1 production, are a strong indicator of susceptibility to severe periodontitis in adults.

Multiplex PCR using conserved and species-specific 16S rRNA gene primers for simultaneous detection of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis

Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis are strongly associated with periodontitis. However, little is known about their distribution in periodontally healthy individuals, because culturing techniques are not sufficiently sensitive. A modified multiplex PCR was developed to address that question. Our method uses two species-specific forward primers in combination with a single reverse primer. These primers target variable and conserved regions of the 16S rRNA gene. Sensitivity was determined by testing serial dilutions of A. actinomycetemcomitans and P. gingivalis cells. Primer specificity was tested against (i) six A. actinomycetemcomitans strains and four P. gingivalis strains, (ii) seven different species of oral bacteria, and (iii) supra- and subgingival plaque from 20 subjects. The multiplex PCR had a lower limit of detection of 2 A. actinomycetemcomitans and 30 P. gingivalis cells. Species-specific amplicons were obtained for all A. actinomycetemcomitans and P. gingivalis strains tested and did not occur with seven other bacterial species unless A. actinomycetemcomitans and P. gingivalis were added. Neither target species was detected in supragingival plaque; A. actinomycetemcomitans was detected in one subgingival specimen, and P. gingivalis was detected in another. When plaque samples were spiked with 10 A. actinomycetemcomitans cells and 100 P. gingivalis cells, species-specific amplicons were detected. These findings show our multiplex PCR to be highly sensitive and specific while allowing simultaneous detection of A. actinomycetemcomitans and P. gingivalis. This assay has potential applications in epidemiological studies, diagnosis, treatment planning, and monitoring of periodontal pathogens.

Specific antibody reactivity against a 110-kilodalton Actinobacillus actinomycetemcomitans protein in subjects with periodontitis

The purpose of the present study was to determine the serum immunoglobulin A (IgA), IgM, and IgG reactivities against proteins of Actinobacillus actinomycetemcomitans in patients with periodontitis. Serum samples from 20 patients with early-onset periodontitis, 20 patients with adult periodontitis, and 20 age- and sex-matched healthy controls were assessed by immunoblot analysis. IgG antibody reactivity against a sarcosyl-insoluble 110-kDa protein of A. actinomycetemcomitans was detected in 65 and 45% of patients with early-onset periodontitis and adult peritonitis, respectively, and IgA antibodies against this protein were found in 70 and 55% of these patients, respectively. However, control subjects showed no IgG reactivity, and IgA antibodies against the sarcosyl-insoluble 110-kDa protein were detected in only 5% of the patients (P < 0.05). There was no IgM antibody reactivity against this protein in any of the diseased or healthy subjects. The sensitivity and specificity of serum IgA antibody reactivity against the 110-kDa protein in detecting subgingival A. actinomycetemcomitans infection, as determined by PCR, were 77 and 66%, respectively. The results of the study indicated that the sarcosyl-insoluble 110-kDa protein is a potential candidate for use in the serodiagnosis of periodontal disease.

Putative periodontal pathogens, antibody titres and avidities to them in a longitudinal study of patients with resistant periodontitis

OBJECTIVE

To study changes in antibody titres and antibody avidities to putative periodontal pathogens in patients with resistant periodontitis and to compare these findings with the result of culture of these pathogens.

SUBJECTS AND METHODS

Patients meeting strict clinical criteria in whom periodontal therapy had failed to prevent disease progression were studied microbiologically and immunologically over a 75-week period. Particular reference was made to the isolation of Actinobacillus actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) together with changes in antibody titres and avidities to these organisms between baseline examination and week 75.

RESULTS

Pg was eliminated following antibiotic treatment but metronidazole and amoxycillin therapy failed to remove Aa in all cases. Antibody avidities to these pathogens were higher in patients than in matched controls but no change in avidity was noted during the course of treatment. Most antibody titres were not significantly higher in patients than in controls.

CONCLUSIONS

Continued disease progression characterised these patients who, nevertheless, mounted an immune response to the periodontal pathogens but this appeared to be inadequate to stop the disease.