Characterisation of black-pigmented anaerobes isolated from diseased and healthy periodontal sites

A randomized, placebo-controlled clinical trial evaluating of a mouthwash containing Sambucus williamsii var. coreana extract for prevention of gingivitits

The purpose of this study is to verify the clinical applicability by applying a mouthwash containing Sambucus williamsii var. coreana extract for preventing periodontal disease. A randomized, double-blind, placebo-controlled study was conducted on 64 patients, excluding those with insufficient data, who visited M dental clinic located in Busan, Korea. Thirty-two people were assigned respectively to the saline solution gargle group and the Sambucus williamsii var. coreana extract gargle group to conduct the O'Leary index, plaque index (PI), gingival index (GI), and subgingival plaques. For the homogeneity of the two groups, scaling was carried out one week before the experiment, and the participants were taught for oral care to conduct during the study period. SPSS 24.0 for Windows (IBM Corp., Armonk, NY, USA) was used to compare the saline solution gargle group and the Sambucus williamsii var. coreana extract gargle group as well as to analyze Baseline (before gargle application), Treatment (immediately after gargle application), and After 5 Days (5 days after gargle application). There was a significant difference in the O'Leary index, PI, GI and subgingival plaques after Treatment and After 5 days (p < 0.05). Also, the periodontal-related indexes improved as the application time increased in the Sambucus williamsii var. coreana extract gargle group. The antibacterial effect was also shown for gram-positive bacteria and gram-negative bacteria in subgingival plaques as the application time increased. The use of the mouthwash containing Sambucus williamsii var. coreana extract was found to be effective for oral periodontal-related indicators and bacteria causing periodontal disease. Therefore, using a mouthwash containing Sambucus williamsii var. coreana extract, a natural drug, will possibly maintain healthy periodontal health by inhibiting and preventing the progression of periodontal disease.

Discrimination of Bacterial Community Structures among Healthy, Gingivitis, and Periodontitis Statuses through Integrated Metatranscriptomic and Network Analyses

Periodontal disease is an inflammatory condition caused by polymicrobial infection. The inflammation is initiated at the gingiva (gingivitis) and then extends to the alveolar bone, leading to tooth loss (periodontitis). Previous studies have shown differences in bacterial composition between periodontal healthy and diseased sites. However, bacterial metabolic activities during the health-to-periodontitis microbiome shift are still inadequately understood. This study was performed to investigate the bacterial characteristics of healthy, gingivitis, and periodontitis statuses through metatranscriptomic analysis. Subgingival plaque samples of healthy, gingivitis, and periodontitis sites in the same oral cavity were collected from 21 patients. Bacterial compositions were then determined based on 16S rRNA reads; taxonomic and functional profiles derived from genes based on mRNA reads were estimated. The results showed clear differences in bacterial compositions and functional profiles between healthy and periodontitis sites. Co-occurrence networks were constructed for each group by connecting two bacterial species if their mRNA abundances were positively correlated. The clustering coefficient values were 0.536 for healthy, 0.600 for gingivitis, and 0.371 for periodontitis sites; thus, network complexity increased during gingivitis development, whereas it decreased during progression to periodontitis. Taxa, including Eubacterium nodatum, Eubacterium saphenum, Filifactor alocis, and Fretibacterium fastidiosum, showed greater transcriptional activities than those of red complex bacteria, in conjunction with disease progression. These taxa were associated with periodontal disease progression, and the health-to-periodontitis microbiome shift was accompanied by alterations in bacterial network structure and complexity.

IMPORTANCE The characteristics of the periodontal microbiome influence clinical periodontal status. Gingivitis involves reversible gingival inflammation without alveolar bone resorption. In contrast, periodontitis is an irreversible disease characterized by inflammatory destruction in both soft and hard tissues. An imbalance of the microbiome is present in both gingivitis and periodontitis. However, differences in microbiomes and their functional activities in the healthy, gingivitis, and periodontitis statuses are still inadequately understood. Furthermore, some inflamed gingival statuses do not consistently cause attachment loss. In this study, metatranscriptomic analyses were used to investigate the specific bacterial composition and gene expression patterns of the microbiomes of the healthy, gingivitis, and periodontitis statuses. In addition, co-occurrence network analysis revealed that the gingivitis site included features of networks observed in both the healthy and periodontitis sites. These results provide transcriptomic evidence to support gingivitis as an intermediate state between the healthy and periodontitis statuses.

Insertional Inactivation of Prevotella intermedia OxyR Results in Reduced Survival with Oxidative Stress and in the Presence of Host Cells

One of the most abundant bacteria in the subgingival pockets of patients with bleeding following mechanical periodontal therapy is Prevotella intermedia. However, despite its abundance, the molecular mechanisms of its contribution to periodontal disease are not well known. This is mainly due to the lack of genetic tools that would allow examination of the role of predicted virulence factors in the pathogenesis of this bacterium. Here, we report on the first mutant in the P. intermedia OMA14 strain. The mutation is an allelic exchange replacement of the sequences coding for a putative OxyR regulator with ermF sequences coding for the macrolide-lincosamide resistance in anaerobic bacteria. The mutant is severely impaired in its ability to grow with eukaryotic cells, indicating that it is an important target for interventional strategies. Further analyses reveal that its ability to grow with oxidative stress species, in the form of hydrogen peroxide and oxygen, is severely affected. Transcriptome analysis reveals that the major deregulated genes code for the alkylhydroperoxide reductase system, AhpCF, mediating protection from peroxide stress. Moreover, genes coding for Dps, CydA and Ftn are downregulated in the mutant strain, as further verified using qRT-PCR analysis. In conclusion, we succeeded in generating the first P. intermedia mutant and show that the OxyR-deficient strain is unable to survive with a variety of host cells as well as with oxidative stress.

Population-Genomic Insights into Variation in Prevotella intermedia and Prevotella nigrescens Isolates and Its Association with Periodontal Disease

High-throughput sequencing has helped to reveal the close relationship between Prevotella and periodontal disease, but the roles of subspecies diversity and genomic variation within this genus in periodontal diseases still need to be investigated. We performed a comparative genome analysis of 48 Prevotella intermedia and Prevotella nigrescens isolates that from the same cohort of subjects to identify the main drivers of their pathogenicity and adaptation to different environments. The comparisons were done between two species and between disease and health based on pooled sequences. The results showed that both P. intermedia and P. nigrescens have highly dynamic genomes and can take up various exogenous factors through horizontal gene transfer. The major differences between disease-derived and health-derived samples of P. intermedia and P. nigrescens were factors related to genome modification and recombination, indicating that the Prevotella isolates from disease sites may be more capable of genomic reconstruction. We also identified genetic elements specific to each sample, and found that disease groups had more unique virulence factors related to capsule and lipopolysaccharide synthesis, secretion systems, proteinases, and toxins, suggesting that strains from disease sites may have more specific virulence, particularly for P. intermedia. The differentially represented pathways between samples from disease and health were related to energy metabolism, carbohydrate and lipid metabolism, and amino acid metabolism, consistent with data from the whole subgingival microbiome in periodontal disease and health. Disease-derived samples had gained or lost several metabolic genes compared to healthy-derived samples, which could be linked with the difference in virulence performance between diseased and healthy sample groups. Our findings suggest that P. intermedia and P. nigrescens may serve as “crucial substances” in subgingival plaque, which may reflect changes in microbial and environmental dynamics in subgingival microbial ecosystems. This provides insight into the potential of P. intermedia and P. nigrescens as new predictive biomarkers and targets for effective interventions in periodontal disease.

Interaction of Prevotella intermedia strain 17 leucine-rich repeat domain protein AdpF with eukaryotic cells promotes bacterial internalization

Prevotella intermedia is an oral bacterium implicated in a variety of oral diseases. Although internalization of this bacterium by nonphagocytic host cells is well established, the molecular players mediating the process are not well known. Here, the properties of a leucine-rich repeat (LRR) domain protein, designated AdpF, are described. This protein contains a leucine-rich region composed of 663 amino acid residues, and molecular modeling shows that it folds into a classical curved solenoid structure. The cell surface localization of recombinant AdpF (rAdpF) was confirmed by electron and confocal microscopy analyses. The recombinant form of this protein bound fibronectin in a dose-dependent manner. Furthermore, the protein was internalized by host cells, with the majority of the process accomplished within 30 min. The internalization of rAdpF was inhibited by nystatin, cytochalasin, latrunculin, nocodazole, and wortmannin, indicating that microtubules, microfilaments, and signal transduction are required for the invasion. It is noteworthy that preincubation of eukaryotic cells with AdpF increased P. intermedia 17 internalization by 5- and 10-fold for HeLa and NIH 3T3 fibroblast cell lines, respectively. The addition of the rAdpF protein was also very effective in inducing bacterial internalization into the oral epithelial cell line HN4, as well as into primary cells, including human oral keratinocytes (HOKs) and human umbilical vein endothelial cells (HUVECs). Finally, cells exposed to P. intermedia 17 internalized the bacteria more readily upon reinfection. Taken together, our data demonstrate that rAdpF plays a role in the internalization of P. intermedia 17 by a variety of host cells.

Association of periodontitis with increased colonization by Prevotella nigrescens

AIM

To estimate differences in the prevalence of Prevotella intermedia and Prevotella nigrescens in the subgingival plaque of patients with periodontitis (including aggressive and advanced chronic periodontitis) compared to healthy controls, and to search for significant associations with clinical status.

METHODS

Sixteen patients and 16 healthy controls were enrolled in this study. Interproximal plaque index, oral hygiene index, gingival index, bleeding on probing, probing depth, and clinical attachment level were recorded. Samples of subgingival plaque were taken with paper points from four teeth of each individual and immediately plated on appropriate supplemented Columbia agar. Black pigmented colonies were identified with the Rapid ID32 A system, and further differentiated using matrix-assisted laser desorption ionization-time of flight mass spectrometry. For the statistical analysis, chi-squared test and the Mann-Whitney U-test were used.

RESULTS

Prevotella nigrescens was isolated from 10 patients and three controls, while P. intermedia was isolated from only two patients. P. nigrescens was found more frequently in the subgingival plaque of patients (P = 0.029), and was significantly associated with high values of clinical indices (P ≤ 0.025). Significant differences for P. intermedia were not found.

CONCLUSIONS

Periodontitis seems to be associated with increased colonization with P. nigrescens. Whether or not it is a major pathogen needs to be determined.

Detection and clonal analysis of anaerobic bacteria associated to endodontic-periodontal lesions

BACKGROUND

Microbial agents in root canal systems can induce periodontal inflammation. The aims of this study are to detect anaerobic microorganisms in endodontic-periodontal lesions, determine the genetic diversity among them, and assess the simultaneous colonization of the pulp and periodontal microenvironments by a single clone.

METHODS

Twenty-seven teeth of patients with endodontic-periodontal lesions were selected. Samples were spread on an agar-blood medium, the detection of each species was performed using a polymerase chain reaction, and the determination of the simultaneous presence of the same species in the microenvironments by one or more clones was determined using arbitrarily primed PCR.

RESULTS

Prevotella intermedia (Pi) was the most prevalent species of the colonies in periodontal pockets, whereas Porphyromonas gingivalis (Pg) and Pi were the more prevalent in root canals. Isolates of Pi and Pg were simultaneously identified in root canals and periodontal pockets. Eighteen percent of teeth exhibited the simultaneous colonization by Pg, Tannerella forsythia (previously T. forsythensis), and Porphyromonas endodontalis in the pulp and periodontal microenvironments. The presence of these species was noted even in niches from which no colonies were isolated. Seventeen different genotypes were found in periodontal and pulp sites, with the majority of sites colonized by one or two different genotypes. A high degree of genotype similarity was found for samples of Pg isolated from only one site as well as for those isolated from both microenvironments.

CONCLUSION

Different clones of Pi and Pg with a high intraspecific genotype similarity were found to colonize the same anatomic sites in endodontic-periodontal infections.

Genetic analysis of mobile tetQ elements in oral Prevotella species

Prevotella species are members of the bacterial oral flora and are opportunistic pathogens in polymicrobial infections of soft tissues. Antibiotic resistance to tetracyclines is common in these bacteria, and the gene encoding this resistance has been previously identified as tetQ. The tetQ gene is also found on conjugative transposons in the intestinal Bacteroides species; whether these related bacteria have transmitted tetQ to Prevotella is unknown. In this study, we describe our genetic analysis of mobile tetQ elements in oral Prevotella species. Our results indicate that the mobile elements encoding tetQ in oral species are distinct from those found in the Bacteroides. The intestinal bacteria may act as a reservoir for the tetQ gene, but Prevotella has incorporated this gene into an IS21-family transposon. This transposon is present in Prevotella species from more than one geographical location, implying that the mechanism of tetQ spread between oral Prevotella species is highly conserved.

AdpC is a Prevotella intermedia 17 leucine-rich repeat internalin-like protein

The oral bacterium Prevotella intermedia attaches to and invades gingival epithelial cells, fibroblasts, and endothelial cells. Several genes encoding proteins that mediate both the adhesion and invasion processes are carried on the genome of this bacterium. Here, we characterized one such protein, AdpC, belonging to the leucine-rich repeat (LRR) protein family. Bioinformatics analysis revealed that this protein shares similarity with the Treponema pallidum LRR (LRR(TP)) family of proteins and contains six LRRs. Despite the absence of a signal peptide, this protein is localized on the bacterial outer membrane, indicating that it is transported through an atypical secretion mechanism. The recombinant form of this protein (rAdpC) was shown to bind fibrinogen. In addition, the heterologous host strain Escherichia coli BL21 expressing rAdpC (V2846) invaded fibroblast NIH 3T3 cells at a 40-fold-higher frequency than control E. coli BL21 cells expressing a sham P. intermedia 17 protein. Although similar results were obtained by using human umbilical vein endothelial cells (HUVECs), only a 3-fold-increased invasion of V2846 into oral epithelial HN4 cells was observed. Thus, AdpC-mediated invasion is cell specific. This work demonstrated that AdpC is an important invasin protein of P. intermedia 17.

Invasive differences among Porphyromonas gingivalis strains from healthy and diseased periodontal sites

BACKGROUND AND OBJECTIVE

The purpose of this study was to determine any difference between Porphyromonas gingivalis isolates from periodontally healthy sites as compared to those from diseased sites with respect to the ability to invade host cells.

MATERIAL AND METHODS

Subgingival plaque samples were obtained from periodontally healthy and diseased sites using paper points. P. gingivalis colonies were isolated and tested, using an antibiotic protection assay, for their ability to invade KB cells. P. gingivalis 381 and Escherichia coli MC1061 were used as controls.

RESULTS

Mean values of 16.79 +/- 0.86 x 10(3) colony-forming units/mL and 26.14 +/- 2.11 x 10(3) colony-forming units/mL were observed in invasion assays for isolates from periodontally healthy and diseased sites, respectively. P. gingivalis present in diseased sites had significantly greater invasive abilities than strains isolated from healthy sites. No statistical difference was noted between male or female subjects concerning the degree of invasion; isolates from diseased sites from both genders had significantly greater invasion abilities than those from healthy sites. A significant correlation was found between the increased invasive capabilities of P. gingivalis isolates vs. an increased probing depth.

CONCLUSION

The increased invasion noted with P. gingivalis isolates from diseased sites vs. healthy sites, and the increased invasive capabilities with increasing probing depth, indicate that P. gingivalis isolates have a varying ability to invade host cells in the periodontal pocket.

Clinical and microbiological effects of fixed orthodontic appliances on periodontal tissues in adolescents

OBJECTIVE

To determine the effects of fixed orthodontic appliances on periodontal health and microbiological composition of subgingival dental plaque.

MATERIAL AND METHODS

This prospective longitudinal self-controlled study was conducted on 32 adolescents (13 males, 19 females), who were scheduled for fixed orthodontic treatment between 2002 and 2005. Dental plaque accumulation, gingival inflammation and pocket probing depth were measured at the mesio-vestibular angle of the examined group of teeth followed by collection of subgingival dental plaque samples in the same points. These periodontal indices and microbiological parameters were determined prior to the placement of fixed appliances and 1, 3 and 6 months after the beginning of orthodontic treatment.

RESULTS

All values of both clinical and microbiological parameters started to increase after the placement of fixed appliances. Maximum values were reached 3 months after fixed appliance placement followed by their decrease in the last registration period of 6 months after the placement of fixed appliances.

CONCLUSIONS

Treatment with fixed appliances in adolescents may transitionally increase the values of all periodontal indices and stimulate the growth of periodontopathogenic bacteria, but without destructive effects on deep periodontal tissues.

Effect of oral bacteria on growth and survival of Candida albicans biofilms

The purpose of this study was to evaluate the effect of eight aerobic and anaerobic oral commensal bacterial species on in vitro Candida albicans biofilm development. A single isolate of C. albicans 2560 g, and eight different species of oral bacteria comprising, Actinomyces israelii, Lactobacillus acidophilus, Prevotella nigrescens, Porphyromonas gingivalis, Pseudomonas aeruginosa, Escherichia coli, Streptococcus mutans, and Streptococcus intermedius were studied using an in vitro biofilm assay. Biofilm formation was quantified in terms of the ability of Candida to grow on polystyrene plastic surfaces co-cultured with the foregoing bacteria. A viable cell count was used to quantify the sessile yeast growth and scanning electron microscopy was employed to confirm and visualize biofilm formation. Co-culture with differing concentrations of bacteria had variable effects on Candida biofilm formation. Co-culture with the highest concentrations of each of the foregoing bacteria resulted in a consistent reduction in the yeast counts in the candidal biofilm (P<0.05), except for L. acidophilus, S. mutans, and, S. intermedius co-cultures. Further, on regression analysis a significant negative correlation between the co-culture concentration of either P. gingivalis or E. coli and viable yeast counts in the biofilm was noted (P<0.05) although this was not evident for the other bacterial species. Taken together, our data indicate that, quantitative and qualitative nature of the bacteria modulate C. albicans biofilm formation in mixed species environments such as the oral cavity.

Use of polymerase chain reaction techniques and sodium dodecyl sulfate-polyacrylamide gel electrophoresis for differentiation of oral Lactobacillus species

BACKGROUND/AIMS

The genus Lactobacillus has been associated with dental caries in humans, although it is seldom speciated due to lack of simple and nonlaborious identification methods. A considerable heterogeneity among Lactobacillus species has been demonstrated. The purpose of this study was to develop simple methods combining restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-amplified 16S rRNA (16S rRNA gene PCR-RFLP) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for the identification of 13 reference strains of Lactobacillus.

METHODS

The 16S rRNA gene sequences were amplified by PCR using universal primers and digestion of PCR products with the restriction endonucleases, HpaII and HaeIII. The 16S rRNA gene PCR-RFLP is reproducible and has been proved to be useful for differentiating Lactobacillus strains to species level. Seventy-seven Lactobacillus isolates from a Thai population were used to show the applicability of the identification test.

RESULTS

PCR-RFLP alone had limitations, because the RFLP patterns of Lactobacillus casei and Lactobacillus rhamnosus and of Lactobacillus acidophilus and Lactobacillus crispatus showed similar patterns; however, these could be differentiated by SDS-PAGE. Of the 77 isolates, 38 were identified as Lactobacillus fermentum, 25 as L. rhamnosus, 5 as Lactobacillus salivarius, 5 as L. casei, 3 as L. acidophilus and 1 as Lactobacillus plantarum.

CONCLUSION

16S rRNA gene PCR-RFLP, using HpaII and HaeIII, together with SDS-PAGE protein profiles could be an alternative method for the identification of oral Lactobacillus strains to species level, and may be applicable for large-scale studies on the association of Lactobacillus to dental caries.

Characterization of a bacteriocin produced by Prevotella nigrescens ATCC 25261

AIMS

To characterize the antimicrobial activity produced by Prevotella nigrescens ATCC 25261, and to evaluate its safety on cultured gingival fibroblasts.

METHODS AND RESULTS

An antimicrobial activity was obtained from purifying the culture supernatant of Pr. nigrescens ATCC 25261. Purification of the active compound was achieved with ammonium sulphate precipitation followed by anion-exchange and gel filtration chromatography. As revealed by SDS-PAGE, the active fraction was relatively homogeneous, showing a protein with an approximate molecular weight of 41 kDa. The antimicrobial compound, named nigrescin, exhibited a bactericidal mode of action against Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, and Actinomyces spp. Nigrescin was stable in a pH range between 6.5 and 9.5, at 100 degrees C for 10 min, and resistant to lyophilization. But its activity was lost after proteinase K treatment. Despite at very high concentrations beyond the minimum inhibitory concentration (MIC), nigrescin was not toxic to the gingival fibroblasts.

CONCLUSION

Nigrescin is a novel bacteriocin produced by Pr. nigrescens ATCC 25261. It exhibits antimicrobial activity against species that are implicated in periodontal diseases. The absence of toxicity on the gingival fibroblasts suggests the possibility in using of nigrescin for an application in periodontal treatment.

SIGNIFICANCE AND IMPACT OF THE STUDY

Novel evidence on nigrescin would make Pr. nigrescens ATCC 25261 attractive in biotechnological applications as an antimicrobial agent in clinical dentistry.

Multiplex polymerase chain reaction assay for simultaneous detection of black-pigmented Prevotella species in oral specimens

Prevotella species are a major component of the oral microflora and some have been implicated in various forms of periodontal disease. Despite the importance of understanding the prevalence of these organisms in the oral microflora, no rapid, simultaneous detection system for these species has been reported. This study developed a multiplex polymerase chain reaction assay for the simultaneous detection of four oral black-pigmented Prevotella species in various oral specimens. This assay will be useful for determining the prevalence of these organisms in the oral ecosystem. Furthermore, this assay system should prove a useful tool for analyzing the role of black-pigmented Prevotella species in the mouth.

Nitric oxide production and inducible nitric oxide synthase expression induced byPrevotella nigrescenslipopolysaccharide

We have examined the effects of lipopolysaccharide (LPS) from Prevotella nigrescens, one of the causative agents of inflammatory periodontal disease and endodontic infections, on the production of nitric oxide (NO) and expression of inducible nitric oxide synthase (iNOS) in the murine macrophage cell line RAW264.7. We also attempted to throw light on the signaling mechanisms involved in P. nigrescens LPS-induced NO production. We found that P. nigrescens LPS can induce iNOS expression and stimulate the release of NO without additional stimuli and demonstrated an important role of the transcription factor NF-kappaB and microtubule polymerization in NO production. The production of NO required l-arginine and protein tyrosine kinase but not activation of protein kinase C. The ability of P. nigrescens LPS to promote the production of NO may be important in the pathogenesis of inflammatory periodontal disease and endodontic infections.

The subgingival microflora in phenytoin-induced gingival hyperplasia

OBJECTIVES

Microbial flora and gingival conditions were compared between a group of patients with phenytoin-induced gingival hyperplasia as a test group, a control group of patients who were administered phenytoin without gingival hyperplasia and a blank group who took no phenytoin and no gingival hyperplasia in mentally retarded patients.

MATERIALS AND METHODS

Subgingival plaque samples were collected from a PHT-induced overgrown gingival pocket and microbiological experiments were performed by culture and PCR methods.

RESULTS

The predominant genera in total cultivable bacteria from subgingival plaque samples were streptococcus and actinomyces with recovery ranges of 37.6-42.1% and 23.4-25.5% of total bacteria, respectively, in all groups. The test group showed a significantly higher level of obligate Gram-negative rods than the control and blank groups. Black-pigmented obligate anaerobic Gram-negative rods were detected in 10.3% of total cultivable bacteria in the test group. The black-pigmented rods were predominantly Prevotella intermedia in the test group and Prevotella nigrescens in the control and blank groups. Porphyromonas gingivalis and Porphyromonas endodontalis were also detected in the test group with small values.

CONCLUSIONS

These results suggested that black-pigmented rods, particularly P. intermedia, could be habitable in the environment of gingival hyperplasia.

New bacterial species associated with chronic periodontitis

Recent investigations of the human subgingival oral flora based on ribosomal 16S cloning and sequencing have shown many of the bacterial species present to be novel species or phylotypes. The purpose of the present investigation was to identify potential periodontal pathogens among these newly identified species and phylotypes. Species-specific ribosomal 16S primers for PCR amplification were developed for detection of new species. Associations with chronic periodontitis were observed for several new species or phylotypes, including uncultivated clones D084 and BH017 from the Deferribacteres phylum, AU126 from the Bacteroidetes phylum, Megasphaera clone BB166, clone X112 from the OP11 phylum, and clone I025 from the TM7 phylum, and the named species Eubacterium saphenum, Porphyromonas endodontalis, Prevotella denticola, and Cryptobacterium curtum. Species or phylotypes more prevalent in periodontal health included two uncultivated phylotypes, clone W090 from the Deferribacteres phylum and clone BU063 from the Bacteroidetes, and named species Atopobium rimae and Atopobium parvulum.

Acid-neutralizing activity during amino acid fermentation by Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum

Acid-neutralizing activity during amino acid fermentation by washed cells of Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum was studied. When the washed cells of these strains were anaerobically incubated in the presence of aspartylaspartic acid or glutamylglutamic acid for P. gingivalis, aspartic acid for P. intermedia and glutamic acid for F. nucleatum at an initial pH of 5.0 or 5.5, the pH of the incubation mixtures rose toward neutral. F. nucleatum had the highest acid-neutralizing activity, followed by P. intermedia and P. gingivalis. The P. intermedia and F. nucleatum cells were used to measure the amounts of base produced at a fixed pH of 5.0. These cells generated significant amounts of base at pH 5.0 along with the production of organic acids and ammonia from aspartic or glutamic acid. Acid-base balance theoretically calculated from the amounts of consumed substrate and end products implies that the acid-neutralizing activity was derived from the decrease in acidity during the fermentation of amino acid into organic acids and ammonia.

Comparison of microbial cultivation and a commercial PCR based method for detection of periodontopathogenic species in subgingival plaque samples

OBJECTIVES

Microbiological laboratory procedures are involved in diagnosis and therapy control of progressive and refractory forms of periodontitis. In recent years techniques have been developed based on the detection of nucleic acids. The purpose of this study was to validate the commercially available micro-Dent(R) test which employs probes for A. actinomycetemcomitans, P. gingivalis, P. intermedia, B. forsythus and T. denticola.

METHODS

122 plaque samples obtained from periodontal pockets with various depths from 33 early onset periodontitis (EOP) patients and 15 periodontally healthy subjects were analysed by cultivation and the microDent(R) kit.

RESULTS

Both cultivation and the nucleic acid based assay showed a positive correlation of pocket depth with the frequency and quantity of periodontopathogenic species. T. denticola was found only in pockets > 4 mm in EOP patients. Comparison of the two methods revealed that the microDent(R) kit identified both P. gingivalis and B. forsythus more often than did the cultivation method.

CONCLUSIONS

Nucleic acid techniques should replace cultivation methods as gold standard in microbiological diagnosis of progressive periodontitis. The micro-Dent(R) kit can be recommended for microbiological laboratories analysing subgingival plaque samples.

Characterization of binding and utilization of hemoglobin by Prevotella nigrescens

The ability of Prevotella nigrescens to utilize and bind to hemoglobin was investigated. Growth studies showed that P. nigrescens was able to utilize hemoglobin efficiently as an iron source. Binding of P. nigrescens to hemoglobin was demonstrated by dot blot assay. Heat and trypsin treatments of the bacteria led to a decrease in activity. Globin gave nearly complete inhibition of activity. Additionally, lactoferrin partially inhibited activity. In contrast, transferrin, cytochrome C and catalase exerted little or no inhibitory effect. Although the sugars tested did not affect activity, several of the amino acids tested, including arginine, cysteine, histidine and lysine, inhibited activity. In a solid phase assay, 41-, 56- and 59-kDa proteins of P. nigrescens reacted with hemoglobin. These results suggest that P. nigrescens utilizes hemoglobin for growth and 41-, 56- and 59-kDa proteins may be involved in hemoglobin binding.

Effect of non-surgical periodontal treatment on clinical parameters and the numbers of Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans at adult periodontitis sites

BACKGROUND, AIMS

The purpose of this study was to relate the numbers of Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans cells to clinical parameters at diseased and healthy periodontal sites before and after non-surgical periodontal therapy using a sensitive quantitative PCR method (Q-PCR).

METHOD

The sensitivity of the Q-PCR was less than 10 cells for all three species. Subgingival plaque samples were collected from 541 sites in 50 adult periodontitis subjects pre-treatment, post-treatment and at a follow-up visit (3-6 months post-treatment). Pocket probing depth, attachment loss and bleeding on probing were recorded at each visit and both healthy and diseased sites in each subject were sampled.

RESULTS

Quantification revealed that P. gingivalis counts were associated with pocket depth (p=0.006) and attachment loss (p=0.010); however, neither P. intermedia nor A. actinomycetemcomitans was associated with the clinical signs examined. Post-treatment, there was a significant decrease in the numbers of all three species in both the diseased and healthy sites (86-99%) but none were eradicated. Positive associations were found between any two of the three species studied both pre- and post-therapy. By the follow-up visit, there was a significant improvement in the probing depth of deep sites (p=0.001) but in no other clinical parameters.

CONCLUSION

This study demonstrates the usefulness of Q-PCR for enumerating putative pathogens in clinical periodontal specimens and that the numbers of the three organisms in all sites decrease with non-surgical periodontal therapy.

Distribution of the tetracycline resistance determinant tetQ gene in oral isolates of black-pigmented anaerobes in Japan

We investigated the distribution of tetracycline resistance determinant tetQ in oral black-pigmented anaerobes using a polymerase chain reaction (PCR) METHOD: A total of 185 healthy subjects were divided into 3 groups based on subject age: young (6 to 10 years, n=58), middle (11 to 40 years, n=96), and elder (exactly 70 years, n=31). The prevalence of black-pigmented anaerobes in the gingival sulcus among these groups was 29.3%, 28.2%, and 64.5%, respectively. The prevalence of Prevotella nigrescens among these groups was 22.4%, 15.6%, and 32.3%, respectively, whereas the prevalence of Prevotella intermedia was 1.7%, 4.2%, and 35.5%, respectively. Porphyromonas gingivalis was found only in the elder group (16.1%). The prevalence of the tetQ gene in the black-pigmented anaerobes-positive subjects was almost the same among the 3 groups (approximately 30%). The tetQ gene was found in 27.5% (46 of 167) of P. nigrescens isolates, whereas it was found in only 6.4% (3 of 47) of P. intermedia isolates and in none of the 19 P. gingivalis isolates. Restriction endonuclease digestion patterns of the PCR products revealed 83.6% of 49 tetQ-positive isolates were of subtype A2H2 (AluI type 2, HpaII type 2).

Isolation and genotyping of black-pigmented anaerobes from periodontal sites of HIV-positive and non-infected subjects in Thailand

BACKGROUND, AIMS

The aims of this study were to investigate the prevalence of periodontitis, the prevalence of black-pigmented anaerobes and the genotypes of Porphyromonas gingivalis and Prevotella intermedia present in HIV-infected and control subjects in a heterosexual Thai population.

METHOD

50 AIDS patients and 50 control subjects were included in the study. Their periodontal condition was examined by assessment of bleeding on probing, attachment loss and probing depth, and presence of erythema around 6 teeth (16, 21, 24, 36, 41, 44). Subgingival plaque was collected from the mesiobuccal sites of these teeth and was cultured anaerobically for black-pigmented bacteria. Species were characterised using biochemical profiles and total protein profiles. Genotyping of each isolate was performed using PCR techniques.

RESULTS

There was little clinical evidence of HIV-associated periodontitis in the HIV-positive subjects and no difference was found in the prevalence or genotype distribution of black-pigmented anaerobes between HIV-infected and control subjects.

CONCLUSIONS

These data suggest lack of severe periodontal destruction due to HIV-infection in Thailand and that these subjects are not colonised by more numerous or characteristic clones of certain putative periodontal pathogens.

Occurrence of Prevotella intermedia and Prevotella nigrescens in relation to gingivitis and gingival health

AIM

The occurrence of Prevotella intermedia (Pi) and Prevotella nigrescens (Pn) in relation to natural gingivitis, gingival health and 14-day experimental gingivitis was investigated in 25 non-dental students.

MATERIALS AND METHODS

Samples were taken from the dorsum of the tongue, the tonsils (or tonsillar area), and the supra- and subgingival plaque.

RESULTS

The microbiological results show that 73% of the samples were positive for the bacterial species presumed to be Pi and/or Pn. In natural gingivitis, gingival health and in experimental gingivitis 25, 23 and 25 subjects were found to be positive for Pi and/or Pn, respectively. The results of the 889 isolates that were successfully purified and differentiated, show that almost all subjects were colonized with Pn whereas approximately half of the study population harboured Pi. These 2 species were isolated from both dental plaque and mucosal sites and were found to colonize the oral cavity simultaneously.

CONCLUSION

In natural gingivitis, at the start and after 14 days of experimental gingivitis, Pn was the predominant micro-organism.

Acquisition and colonization stability of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis in children

The presence of Porphyromonas gingivalis has been shown to be a risk factor for periodontitis in adults, and Actinobacillus actinomycetemcomitans has been implicated as a pathogen in early-onset periodontitis. Both species have been shown to establish stable colonization in adults. In cross-sectional studies, both A. actinomycetemcomitans and P. gingivalis have been detected in over one-third of apparently healthy children. Information on the stability of colonization with these organisms in children could help to elucidate the natural history of the development of periodontitis. For this purpose, samples previously collected from a cohort of 222 children between the ages of 0 and 18 years and previously examined for the presence of P. gingivalis with a PCR-based assay were examined for the presence of A. actinomycetemcomitans. It was detected in 48% of subjects and, like P. gingivalis, was found at similar frequencies among children of all ages (P = 0.53), suggesting very early initial acquisition. One hundred one of the original subjects were recalled after 1 to 3 years to determine the continuing presence of both A. actinomycetemcomitans and P. gingivalis. The prevalence of both species remained unchanged at resampling. However, in most children both species appeared to colonize only transiently, with random concordance between the results of the first and second sampling. Stability of colonization was unrelated to age for A. actinomycetemcomitans, but P. gingivalis was more stable in the late teenage years.

Incidence of Prevotella intermedia and Prevotella nigrescens carriage among family members with subclinical periodontal disease

We established a typing system for Prevotella intermedia and Prevotella nigrescens using the combination of PCR ribotyping and arbitrarily primed PCR (AP-PCR) fingerprinting and applied this system to the study of intrafamilial incidence of these species in the oral cavity. PCR ribotyping followed by subtyping by AP-PCR fingerprinting was applied to each type strain of P. intermedia and P. nigrescens and 54 isolates (32 isolates of P. intermedia and 24 isolates of P. nigrescens) from extraoral infections, resulting in an excellent discriminatory power (discrimination index, 0.99) for both species. A total of 18 subjects from six families, with the subjects from each family comprising the mother, the father, and a child who had subclinical early-stage to moderate adult periodontitis or simple gingivitis and who carried P. intermedia or P. nigrescens, or both, were enrolled in the study of intrafamilial carriage. When 20 colonies per specimen of subgingival plaque, if available, were picked from primary culture, 115 P. intermedia and 178 P. nigrescens isolates were recovered from the 18 subjects. Among the subjects studied, family members shared the same subtype strain(s) but non-family members did not. Multiple subtypes were found in 8 (57%) of the 14 P. nigrescens-positive subjects but in only 3 (27%) of the 11 P. intermedia-positive subjects; the difference was, however, not statistically significant (P = 0.14). These results suggest that the combination of PCR ribotyping and AP-PCR fingerprinting is well suited for the epidemiological study of P. intermedia and P. nigrescens and that each family seems to carry a distinct subtype(s) of these species.

Hemolytic and hemagglutinating activities of Prevotella intermedia and Prevotella nigrescens

A total of 91 isolates of Prevotella intermedia or Prevotella nigrescens from subgingival sites were identified by PCR using primers specific for sequences of 16S rRNA. The hemolytic and hemagglutinating activities of the P. intermedia isolates exhibited significantly higher levels compared to those of the P. nigrescens isolates by quantitative analysis. The hemagglutinin gene (phg) was found in 23 of 26 P. intermedia isolates (88.5%), whereas it was found in only two of 44 isolates (4.5%) of P. nigrescens. The high hemolytic and hemagglutinating activities of P. intermedia may be involved in the pathogenicity of P. intermedia in the progression of periodontal disease.

Cloning of Prevotella intermedia loci demonstrating multiple hemolytic domains

A gene bank was created from Prevotella intermedia strain 27 chromosomal DNA, and a clone was isolated that conferred the expression of two separate modes of hemolytic activity in recombinant Escherichia coli. The original recombinant hemolytic strain (EB34) contained plasmid, pEB34, with a 5.6-kb insert from Sau 3 AI-digested P. intermedia strain 27 chromosomal DNA cloned into the Bam HI site of pUC18. EB34 and deletion subclones were tested for expression of hemolytic activity in a standard tube assay, measuring lysis of erythrocytes spectrophotometrically as a function of hemoglobin release. Cell suspensions of EB34 demonstrated a dose-dependent hemolytic activity, inhibitable by proteases, and heat treatment but not dependent on calcium ions, and not inhibitable by osmoprotectants. Cell-free lysates also demonstrated a heat inhibitable, dose dependent hemolytic activity. Sub-cloning experiments localized the hemolytic region of the insert to a 3.9-kb fragment under direction of the lac promoter. Sequence analysis of the entire insert revealed the presence of multiple open reading frames (1 to 3) in this region which correlated to different forms of hemolytic expression, such that subclones containing all open reading frames 1 to 3 demonstrated strong hemolytic phenotype on blood plates and in the tube assay. Subclones containing only ORF1 demonstrated hemolysis on plates, but not in the tube assay. Subclones containing only open reading frames 2 and 3, but not ORF1 demonstrated hemolysis in the tube assay but not on plates. Homology searches of DNA and protein databases have not revealed significant homologies with reported hemolysins or proteins in any of the open reading frames.

Use of PCR and sodium dodecyl sulfate-polyacrylamide gel electrophoresis techniques for differentiation of Prevotella intermedia sensu stricto and Prevotella nigrescens

Primers were designed from 16S rRNA sequences of Prevotella intermedia sensu stricto and Prevotella nigrescens and were used to discriminate these two species by PCR. The results were compared with those from the PCR technique using primers designed from arbitrarily primed PCR products by Guillot and Mouton (E. Guillot and C. Mouton, J. Clin. Microbiol. 35:1876-1882, 1997). The specificities of both assays were studied by using P. intermedia ATCC 25611, P. nigrescens ATCC 33563, 174 clinical isolates of P. intermedia sensu lato, and 59 reference strains and 58 clinical isolates of other Prevotella species and/or common oral flora. In addition, the usefulness and reliability of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in the differentiation of the two species were examined by comparing the results with those from PCR assays. The controversial lipase test for distinguishing these species was also carried out. Unambiguous differentiation was made by both PCR assays, and the results matched each other. The SDS-PAGE assay was found to misidentify a few strains tested, compared with the results of PCR assays. The lipase test was positive for both species, including the reference strains of P. intermedia and P. nigrescens. We conclude that both PCR assays are simple, rapid, reliable, and specific methods which could be used in clinical studies and that the lipase test is not valuable in the differentiation. The reliable discrimination of the two species by SDS-PAGE is questionable.

Incidence of Prevotella intermedia and Prevotella nigrescens in periodontal health and disease

The incidence of black-pigmented rods (BPRs), especially Prevotella intermedia and Prevotella nigrescens, in periodontal health and disease were examined. Furthermore, the degradative enzyme activities of P. intermedia were compared among the strains from periodontal health and disease. Microbiological specimens were collected from subgingival crevice or periodontal pocket by paper point. The BPRs were found in 71.1% of periodontally healthy subjects (n=45), and in 47.1% of healthy sites (n=34) and 87.8% of active sites (n=41) among periodontally diseased patients. Porphyromonas gingivalis was detected only in active sites of periodontally diseased patients (17.8% of 180 strains). P. intermedia was the predominant BPR in both healthy and active sites (37.3 and 41.7%, respectively) of the patients. However, P. nigrescens was the predominant BPR (70.5% of 173 strains) in periodontally healthy subjects. The enzyme activities of esterase, esterase-lipase, acid-phosphatase and alpha-fucosidase of P. intermedia strains isolated from active sites in patients were significantly higher (P<0.05) than those of healthy subjects. The results suggest that P. intermedia might increase the activity of degradative enzymes under a certain condition and support the progression of periodontitis.

Prevalence of Porphyromonas gingivalis and periodontal health status

Periodontitis is a common, progressive disease that eventually affects the majority of the population. The local destruction of periodontitis is believed to result from a bacterial infection of the gingival sulcus, and several clinical studies have provided evidence to implicate Porphyromonas gingivalis. If P. gingivalis is a periodontal pathogen, it would be expected to be present in most subjects with disease and rarely detected in subjects with good periodontal health. However, in most previous studies, P. gingivalis has not been detected in the majority of subjects with disease, and age-matched, periodontally healthy controls were not included for comparison. The purpose of the study reported here was to compare the prevalence of P. gingivalis in a group with periodontitis to that of a group that is periodontally healthy. A comprehensive sampling strategy and a sensitive PCR assay were used to maximize the likelihood of detection. The target sequence for P. gingivalis-specific amplification was the transcribed spacer region within the ribosomal operon. P. gingivalis was detected in only 25% (46 of 181) of the healthy subjects but was detected in 79% (103 of 130) of the periodontitis group (P < 0.0001). The odds ratio for being infected with P. gingivalis was 11.2 times greater in the periodontitis group than in the healthy group (95% confidence interval, 6.5 to 19.2). These data implicate P. gingivalis in the pathogenesis of periodontitis and suggest that P. gingivalis may not be a normal inhabitant of a periodontally healthy dentition.

Detection of Prevotella intermedia in subgingival plaque of adult periodontitis patients by polymerase chain reaction

A PCR assay was developed that could specifically amplify DNA from the periodontal pathogen Prevotella intermedia. A pair of primers was selected from regions of the 16S rRNA gene of P. intermedia that were both divergent in sequence at their 3' ends with respect to the corresponding regions of the 16S rRNA gene of P. nigrescens, its most closely related species, and used in the PCR assay. Positivity was indicated by amplification of an 855 bp product. Using purified genomic DNA from these 2 species, assay conditions were determined under which only P. intermedia DNA and not P. nigrescens DNA was amplifiable. Absolute specificity of the assay was confirmed by the fact that no amplification products were obtained when using DNA from several other important periodontal organisms. The optimized PCR assay was used to identify P. intermedia in subgingival plaque samples of patients with adult periodontitis. Confirmation of amplification of P. intermedia DNA was achieved by digestion of PCR products with the restriction endonuclease RsaI, which gives different restriction patterns for P. intermedia and P. nigrescens. Of the 97 samples analysed, 38 (39%) were positive for P. intermedia. The results obtained confirm P. intermedia as a possible aetiological agent of adult periodontitis. Additionally, PCR primers targeting the corresponding region of the 16S rRNA gene of P. nigrescens were shown to be specific for the organism when used in a PCR assay, although P. nigrescens was not detectable in any of the subgingival plaques analysed.

Evaluation of the antimicrobial effect of lactoferrin on Porphyromonas gingivalis, Prevotella intermedia and Prevotella nigrescens

The antimicrobial effect of lactoferrin (apoLf) on the oral, black-pigmented anaerobes Porphyromonas gingivalis, Prevotella intermedia and P. nitrescens has been studied. ApoLf did not kill any of these species but it did inhibit the growth of P. gingivalis, while iron-saturated Lf (FeLf) had no effect. The other two species were unaffected by apoLf. This growth inhibitory effect of apoLf could not be explained on the basis of chelation of inorganic iron, since growth of P. gingivalis occurred in the presence of ethylenediamine di-o-hydroxyphenylacetic acid provided haemin was added. Both apoLf and FeLf reduced haemin uptake by all three species and caused the release of cell-bound haemin in a dose-dependent manner. In addition, haemin reduced the binding of both apoLf and FeLf to P. intermedia and P. nigrescens but stimulated the binding of Lf by P. gingivalis. These data suggest that Lf forms complexes with haemin in solution and competes for the binding of haemin to certain cell receptors, possibly lipopolysaccharides, but this is not sufficient to inhibit growth of the bacteria. P. gingivalis appears to bind Lf-haemin complexes, as well as haemin alone, which may facilitate access of the Lf to the outer and cytoplasmic membranes of P. gingivalis, so disrupting function.

A beta-lactamase belonging to group 2e from oral clinical isolates of Prevotella intermedia

A beta-lactamase in oral clinical isolates of Prevotella intermedia that hydrolyzed cefuroxime and cephalothin with rates of 600 and 53.3 respectively, relative to that for cephaloridine (100), was characterized as a 2e-cephalosporinase. Inhibition was observed by clavulanic acid (IC50 0.72 microM), tazobactam (IC50 0.21 microM) and sulbactam (IC50 0.07 microM) and was not inhibited by cloxacillin, EDTA, NaCl or p-CMB. The pI and pH optima were 4.7 and 5.4, respectively.

Acid tolerance and acid-neutralizing activity of Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum

The tolerance to acid and the acid-neutralizing activity of three important periodontopathic bacteria, Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum were studied. P. gingivalis strains grew only at neutral pH and did not utilize glucose, whereas strains of P. intermedia and F. nucleatum could grow under acidic conditions and increased their growth by utilizing glucose. P. gingivalis tended to raise the culture pH during growth. P. intermedia and F. nucleatum raised the culture pH during growth in the absence of glucose, while in the presence of glucose they decreased the pH. Resting cell suspensions of all the bacteria raised the pH in the presence of tryptone and casamino acids. Acid-neutralizing activity was confirmed by measuring base production at a fixed pH with a pH-stat. During neutralization, the cells produced cytotoxic substrates, ammonia and organic acids (butyric, isobutyric and isovaleric acids by P. gingivalis; isovaleric and succinic acids by P. intermedia; propionic and butyric acids by F. nucleatum). These findings suggest that deamination of amino acids into ammonia and organic acids occurs simultaneously with base production, resulting in acid neutralization. These results could partially explain the survival of P. intermedia and F. nucleatum in both supragingival and subgingival plaque and the apparent restriction of P. gingivalis to subgingival plaque. The former bacteria may aid in creation of an environment fostering colonization of subgingival plaque by P. gingivalis.

Occurrence of Prevotella nigrescens and Prevotella intermedia in infections of endodontic origin

The occurrence of Prevotella intermedia and Prevotella nigrescens in endodontic infections was studied using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of whole cell protein to distinguish between the species. Previous studies have shown an association between black-pigmented bacteria (BPB) and endodontic infections and that Prevotella intermedia (previously known as Bacteroides intermedius) was the most commonly isolated BPB. Recently, however, strains identified as P. intermedia were shown to in fact be composed of two separate species, P. intermedia and P. nigrescens. Fifty-six strains of BPB isolated from endodontic infections and previously identified as P. intermedia were used in this study. Following SDS-PAGE, P. nigrescens showed a unique 18.6 kDa band that was used to differentiate P. nigrescens from P. intermedia. Of the 56 strains of BPB, 41 (73.2%) were identified as P. nigrescens and 15 (26.8%) as P. intermedia. This study confirms that P. nigrescens, and not P. intermedia, is the BPB most often isolated from infections of endodontic origin.

Identification of a lactoferrin-binding protein in Prevotella nigrescens

A 40-kDa lactoferrin-binding protein was identified in a strain of Prevotella nigrescens isolated from a patient with periodontitis. The protein was purified by affinity column chromatography using a Sepharose-lactoferrin column and detergent-solubilized membranes. The N-terminal sequence revealed no apparent similarities with any other sequenced bacterial protein. The native conformation of the 40-kDa protein was a condition to bind either iron-free or iron-saturated lactoferrin. A possible function of this Lf-binding protein could be related with an iron acquisition mechanism in P. nigrescens.

Optimized oligonucleotides for the differentiation of Prevotella intermedia and Prevotella nigrescens

The gram-negative, anaerobic bacterium Prevotella intermedia plays an important role in the progression of periodontitis, whereas the etiological role of the closely related but phenotypically indistinguishable species Prevotella nigrescens is controversial. To differentiate between these species properly, 16S rDNA/RNA directed, computer-optimized oligonucleotides were designed and tested with 26 P. intermedia, 26 P. nigrescens and a number of closely and more distantly related strains. The oligonucleotides were used as primers in a polymerase chain reaction and could be demonstrated to be species specific with a detection limit of 50 bacterial cells, which could also be detected when diluted 1:10(5) with different plaque bacteria. In addition, the described oligonucleotides were digoxigenin-labeled at the 3' end and used as DNA probes in a dot blot hybridization assay. This assay, although slightly less sensitive than the polymerase chain reaction-based method, gave species-specific reactions and also allowed (semi-)quantification of bacterial cells in clinical specimens.

Distinction ofPrevotella intermediaandPrevotella nigrescensfrom Endodontic Bacteremia through their Fatty Acid Contents

Prevotella nigrescens has recently been recognized as a new species distinct from Prevotella intermedia. The distinction is based largely on DNA-DNA hybridization, electrophoretic migration of malate and glutamate dehydrogenase, and peptidase and lipase activities of type strains. Gas chromatography of cellular fatty acids can be a useful adjunct for characterization and identification of bacterial species. In the present study, cellular fatty acid profiles were determined for seven strains of P. intermedia and six strains of P. nigrescens. Six of these 13 strains were isolated from the root canal and blood of three patients during endodontic therapy of teeth with Asymptomatic apical periodontitis. The bacteria were cultivated anaerobically in 10 mL prereduced anaerobically sterilized peptone-yeast extract-glucose broth for 24 h. Dried cells of each isolate were methanolysed and their fatty acid contents determined by the Microbial Identification System software package by MIDI. The data were treated by principal component analysis, which distinguished P. nigrescensfromP. intermedia. Cellular fatty acid profiles of these strains of the species in blood matched the profiles of their respective root canal isolates, as demonstrated by Euclidean Distance Square assessment. This suggested that the organisms in the root canal had spread to the bloodstream during endodontic treatment.

Hydrolytic and depolymerising enzyme activity of Prevotella intermedia and Prevotella nigrescens

OBJECTIVE

Prevotella intermedia has been reported to be associated with periodontal disease whilst P. nigrescens has predominantly been isolated from more specific conditions and healthy sites. The aim of the present study was to compare the enzyme activity of these species.

MATERIALS AND METHODS

Nine strains of P. intermedia and 12 strains of P. nigrescens were studied. Lipolytic, saccharolytic, nucleolytic and proteolytic activity was determined by traditional microbiological and chromogenic substrate methods.

RESULTS

All strains hydrolysed gelatine, casein, DNA and RNA. Lipase activity was produced by all strains except P. nigrescens ATCC 33563T. Lipolytic activity of P. nigrescens strains decreased as the environmental glucose concentration was increased. Only two strains, both P. intermedia, hydrolysed benzyl-arg-rho-nitroanilide. All strains hydrolysed alkaline rho-nitrophenolphosphate (except P. intermedia DAL100), produced glycylprolyl dipeptidase activity and demonstrated elastase-like activity. All but three strains (2 P. intermedia and I P. nigrescens) hydrolysed suc-ala-ala-pro-phe-rho-nitroanilide. Overall, no qualitatively analysed enzyme activity was exclusive to all strains of either species. Quantitatively analysed activity exhibited a high degree of variability both within and between species.

CONCLUSIONS

P. intermedia and P. nigrescens degrade natural and synthetic substrates, but intra- and interspecies activity is variable.

Electrophoresis of whole-cell soluble proteins of microorganisms isolated from bacteremias in endodontic therapy

We have previously demonstrated that anaerobic bacteria are the microorganisms most frequently isolated from blood following endodontic therapy of teeth with apical periodontitis. Phenotypic characterisation of the isolates suggested that the bacteria in the blood originated from the root canal. The present experiment using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was carried out in an effort to verify these findings, and to further study the microorganisms involved in endodontic bacteremias. Soluble cellular proteins were extracted from 11 reference strains and 26 bacterial isolates recovered from the root canal and blood. These included Propionibacterium acnes, Peptostreptococcus prevotii, Fusobacterium nucleatum, Prevotella intermedia. Actinomyces israelii, Streptococcus intermedius, Streptococcus sanguis. The electrophoretic patterns mostly confirmed the identity of the isolates as determined by the biochemical and antimicrobial resistance tests. Furthermore, with this typing method the species Prevotella intermedia and Prevotella nigrescens could be differentiated. These species had been recovered from both root canal and blood. Also, differences between subspecies of Fusobacterium nucleatum became evident with SDS-PAGE, and the results indicated that the organism recovered from the root canal and blood was Fusobacterium nucleatum subsp. vincentii. The electrophoretic patterns of the different organisms isolated from the root canal and the blood were similar, providing further evidence that the bacteria found in the blood originated from the root canal.

Clonality of Porphyromonas gingivalis, Prevotella intermedia and Prevotella nigrescens isolated from periodontally diseased and healthy sites

Black-pigmented anaerobes have been implicated as major pathogens in the aetiology of adult periodontitis but these organisms are also found in healthy sites. This study aimed to examine the relationship between genotypes of black-pigmented anaerobes and disease status of periodontal sites using restriction endonuclease analysis (REA) and ribotyping. The main black-pigmented species recovered from sites were Porphyromonas gingivalis, Prevotella intermedia and Prevotella nigrescens. Each of the 58 subjects investigated harboured distinct genotypes of these three species. Most subjects appeared to be colonized by a single genotype of P. gingivalis and Pr. intermedia, whereas multiple types of Pr. nigrescens colonized many individuals. Plasmids were only found in a few Pr. nigrescens strains. No association was found between the disease status of sites and any specific or group of genotypes of either species or presence of a plasmid. Since the same genotypes of P. gingivalis, Pr. intermedia and Pr. nigrescens were found at both diseased and non-diseased sites in a subject, adult periodontitis is not explained by the presence of specially virulent clones of these organisms. Their role in periodontitis, therefore, is likely to be opportunistic.

Collagen-binding activity of Prevotella intermedia measured by a microtitre plate adherence assay

The ability of Prevotella intermedia to bind type I collagen was investigated. A simple method in which bacterial cells were allowed to attach to collagen-coated microtitre plate wells was used to characterize the activity. All strains of P. intermedia tested, as well as those of the closely related species Prevotella nigrescens, showed a capacity to attach to the collagen film. Exponential-phase cultures of P. intermedia demonstrated a greater binding capacity than older cells. Attachment to the collagen film was inhibited by the presence of EDTA, type I and IV collagen, denatured collagen (gelatin), fibrinogen or fibronectin. Pretreatment of bacterial cells with heat (60 degrees C, 30 min) or proteinase K also inhibited the binding. The collagen-binding activity could be solubilized from the bacterial cell surface by incubation with Zwittergent 3-14, a zwitterionic detergent. The collagen-binding capacity of P. intermedia demonstrated in the present study represents a mechanism of colonization allowing these bacteria to attach to a tissue matrix.