Clonal analysis of Porphyromonas gingivalis by the arbitrarily primed polymerase chain reaction

Comparison of cluster analysis of Porphyromonas gingivalis by arbitrarily primed-polymerase chain reaction between healthy and chronic periodontitis subjects

Introduction

Periodontitis is a chronic destructive inflammatory disease of the oral cavity. The main causative agent is presence of biofilm formed due to different micro-organisms. Among different micro- organisms "red complex" bacteria is known to be the main causative agent in progression of periodontitis. Porphyromonas gingivalis out of the red the complex organism plays a major role in progression of periodontitis. P. gingivalisis present in both in healthy and diseased individuals. The difference in the strains will determine the virulence factor of the organism and also progression of disease. Only few studies have been done showing variation in strains present between healthy and diseased.

Aims

To check the difference in heterogeneity of P. gingivalis in chronic periodontitis and healthy individuals through Arbitrarily Primed-PCR (AP-PCR).

Materials and Methods

A total of 400 subjects (200 each of chronic periodontitisandhealthy individuals) were included. Sub-gingival plaque was collected in the Reduced transport fluid (RTF) medium and processed at the institutional central research laboratory. Presence of P. gingivalis was, confirmed by culture andphenotypical analysis. Further confirmed cases were processed for PCR after DNA extraction using 16S rRNA. Positive cases of P. gingivalis were subjected for AP-PCR for clonal analysis using the specific 272 primer.

Results

In 152(76%) and 98(49%) were confirmed for P. gingivalis in chronic periodontitis and healthy individual respectively by PCR. AP-PCR analysis showed 6 clusters with similarity index in CP and 3 clusters with similarity index in Healthy individuals.

Conclusion

The present study showed difference in clusters between chronic periodontitis and healthy individual'sthussuggestive variantin genetic heterogeneity of P. gingivalis strain between healthy and chronic periodontitis. AP- PCR appears to be a promising tool for clonal analysis of P. gingivalis.

Identification of multiple strains of Porphyromonas gingivalis using heteroduplex polymerase chain reaction in varying severity of chronic periodontitis

Aim

Research has demonstrated that there are multiple strains of Porphyromonas gingivalis with varying potency to cause periodontal disease. The current study aims at using heteroduplex polymerase chain reaction (PCR) to detect the strain diversity of P. gingivalis in periodontitis lesions of varying severity in a sample of the Indian population.

Materials and Methods

Subgingival plaque samples were collected from 60 individuals with varying severity of chronic periodontitis and 30 individuals with a clinically healthy periodontium. The samples were subjected to PCR analysis to identify P. gingivalis, followed by heteroduplex analysis to identify the strain diversity in a given sample. Bacterial culture was carried out as a comparative standard.

Results

Of the 56 samples that were positive for P. gingivalis by PCR, 54 samples yielded eight different heteroduplex patterns. Analysis of these patterns indicated that two strains of P. gingivalis were present in 41 individuals (45.6%) and three strains were present in 13 individuals (14.4%). Detection of P. gingivalis by PCR was significantly more in the periodontitis group as compared to the healthy group.

Conclusions

Species-specific PCR and heteroduplex analysis provide a simple and accurate method to analyse the strain diversity of P. gingivalis. P. gingivalis was detected in both healthy periodontal sites as well as sites with periodontitis. The presence of two or three P. gingivalis strains was seen in 60% of the samples.

Qualitative, quantitative and genotypic evaluation of Aggregatibacter actinomycetemcomitans and Fusobacterium nucleatum isolated from individuals with different periodontal clinical conditions

Aggregatibacter actinomycetemcomitans and Fusobacterium nucleatum are strongly associated with periodontitis, and their evaluations are relevant to understand their role in the etiology and progression of periodontal diseases. In this study, the qualitative and quantitative detection of A. actinomycetemcomitans and F. nucleatum, as well as their genetic diversity, were evaluated in individuals with gingivitis, chronic periodontitis and periodontally healthy. In addition, the biotyping, serotyping, and prevalence of the ltx and cdt genes in A. actinomycetemcomitans were also determined. Subgingival biofilms obtained from gingivitis (70), periodontitis (75) and healthy (95) individuals were analyzed by cultures and PCR. Bacterial typing and presence of ltx and cdt genes in A. actinomycetemcomitans were also verified. DNA from A. actinomycetemcomitans and F. nucleatum was detected respectively, in 65.7% and 57.1% of gingivitis, 80% and 68% of periodontitis, and 57.8% and 37.8% of healthy. A. actinomycetemcomitans from gingivitis were biotypes I, II, IV, V, and X, and serotypes a, c, and e. In periodontitis, biotypes II, VI, and X, and serotypes a, b, and c were found. In healthy subjects, biotypes II and X, and serotypes b and c were found. The LTX and ltxA were observed in strains from gingivitis and periodontitis pockets. Subsequently, our data also showed no direct relationship between ltxA gene expression and leukotoxin gene 530-bp presence. On the other hand, cdt gene predominated during the inflammatory disease process. Our results strongly support a role of A. actinomycetemcomitans and F. nucleatum in advanced stage of periodontal disease.

Pathogenicity and genetic profile of oral Porphyromonas species from canine periodontitis

OBJECTIVE

In this study, the presence of the prtC and fimA genes involved in the pathogenicity of oral Porphyromonas spp. isolated from dogs with periodontitis and healthy, as well as their genetic diversity was investigated.

DESIGN

Thirty-two Beagle dogs, 24 with periodontitis and 8 healthy were evaluated. Subgingival samples from only one gingival site of both groups were collected. Bacteria grown in anaerobiosis were identified by RAPID ID 32A kits. From each strain the respective DNA was obtained and used to genotyping by conventional PCR and AP-PCR.

RESULTS

Dogs with periodontitis harbored 28 P. gulae, 2 P. creviocaricanis, 1 P. cangingivalis and 7 P. macacae; and from healthy dogs, 11 P. gulae and 5 P. circumdentaria. In P. gulae isolated from periodontal dogs the gene prtC was observed in 19 (67.85%) and in 7 (63.63%) from healthy dogs. P. gulae strains from periodontal dogs harbored either the gene fimA I or fimA II; while strains from healthy dogs harbored the gene fimA I, fimA II, fimA III or fimA IV, as well as 1 P. circumdentaria the gene fimA II. By AP-PCR strains were grouped in different clusters suggesting heterogeneity of these microorganisms.

CONCLUSIONS

The results presented herein inform that Porphyromonas spp. isolated from dogs with and without periodontitis harbored the prtC and fimA genes and it could be a role in the establishment of the infectious process.

Porphyromonas gingivalis strain diversity

Porphyromonas gingivalis is implicated in the etiology of chronic periodontitis. Genotyping studies suggest that genetic variability exists among P. gingivalis strains; however, the extent of variability remains unclear and regions of variability remain largely unidentified. To assess P. gingivalis strain diversity, we previously used heteroduplex analysis of the ribosomal operon intergenic spacer region (ISR) to type strains in clinical samples and identified 22 heteroduplex types. Additionally, we used ISR sequence analysis to determine the relatedness of P. gingivalis strains to one another and demonstrated a link between ISR sequence phylogeny and the disease-associated phenotype of the strains. In the current study, heteroduplex analysis of the ISR was used to determine the worldwide genetic variability and distribution of P. gingivalis, and microarray-based comparative genomic hybridization (CGH) analysis was used to more comprehensively examine the variability of major heteroduplex type strains by using the entire genome. Heteroduplex analysis of clinical samples from geographically diverse populations identified 6 predominant geographically widespread heteroduplex types (prevalence, > or = 5%) and 14 rare heteroduplex types (prevalence, <2%) which are found in one or a few locations. CGH analysis of the genomes of seven clinically prevalent heteroduplex type strains identified 133 genes from strain W83 that were divergent in at least one of the other strains. The relatedness of the strains to one another determined on the basis of genome content (microarray) analysis was highly similar to their relatedness determined on the basis of ISR sequence analysis, and a striking correlation between the genome contents and disease-associated phenotypes of the strains was observed.

Prevalence and clonal analysis of Porphyromonas gingivalis in primary endodontic infections

This study investigated the prevalence of Porphyromonas gingivalis in 62 teeth with primary endodontic infections by using a species-specific 16S rRNA gene-based nested polymerase chain reaction assay. P. gingivalis isolates recovered from 2 infected root canals were also analyzed for clonal diversity by using arbitrarily primed PCR. Overall, P. gingivalis was found in 48% of the samples. This species was specifically detected in 36% of canals of teeth with chronic apical periodontitis, in 46% of the cases of acute apical periodontitis, and in 67% of acute apical abscesses. P. gingivalis was significantly more frequent in abscess aspirates than in canals of teeth with chronic apical periodontitis (P < .05). Typing of colonies retrieved from 2 infected canals revealed 2 clones per individual. These findings confirmed that P. gingivalis can be an important endodontic pathogen, mostly associated with acute abscesses, and demonstrated that different clonal types of this species can colonize the root canal in the same individual.

Genotypic characterization of Porphyromonas gingivalis isolated from subgingival plaque and blood sample in positive bacteremia subjects with periodontitis

AIM

The objective of this study was to investigate clonal relationship among Porphyromonas gingivalis isolated from subgingival plaque and blood samples in positive transient bacteremia subjects with periodontitis.

MATERIAL AND METHODS

Unrelated patients with general chronic periodontitis or general aggressive periodontitis requiring scaling and root planing (SRP) were included in the study. Genotyping of each isolate was performed using pulsed field gel electrophoresis technique. Genetic relatedness of strains isolated within an individual or between different patients was determined by dendogram analysis.

RESULTS

Following SRP, from 16 patients, seven patients showed positive P. gingivalis bacteremia and nine were negative. Thirty-two strains were isolated from subgingival plaque and blood samples before and during induced transient bacteremia. The majority of the patients harboured one clonal type. Two patients showed different clones in plaque and blood samples suggesting that more than one clone can be found in subgingival plaque. P. gingivalis isolates from periodontitis patients after transient bacteremia following SRP, revealed a high heterogeneity among isolates.

CONCLUSION

In 6/16 subjects the same P. gingivalis isolate was found in the blood and in oral cavity. P. gingivalis heterogeneity suggests no association of a unique clonal type with transient bacteremia.

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

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

Increase in probing depth is correlated with a higher number of Prevotella intermedia genotypes

BACKGROUND

The aims of this study were to determine the genotypic diversity of Prevotella intermedia in subgingival plaque samples by using two techniques, arbitrarily primed polymerase chain reaction (AP-PCR) and heteroduplex analysis, and to assess the relationship of this diversity with increase in probing depth.

METHODS

The subgingival plaque samples were obtained from 12 patients using paper points inserted into periodontal pockets (diseased sites) and healthy gingival sulci (healthy sites) of the same subjects. After isolation and identification, AP-PCR was performed for genotypic characterization of P. intermedia (80 isolates). The clinical samples with a positive result for P. intermedia were amplified by 16S rRNA-based PCR method, and the amplicons were subjected to heteroduplex analysis.

RESULTS

The agreement between the two methods was very high; the AP-PCR and heteroduplex analysis showed that subjects harbored between one and five distinct genotypes of P. intermedia, with a positive association between numbers of genotypes by AP-PCR (P = 0.0042) or heteroduplex (P = 0.0099) and increase in probing depth. No matching of P. intermedia genotypes was observed between healthy and diseased sites of the same individual. Interindividual analyses demonstrated absence of identical clones and indicated a high level of genetic diversity in the species.

CONCLUSION

A clear relationship was observed between a higher number of genotypes and increase in probing depth; these results suggest that environmental challenges in the periodontal pockets may modulate the microbiota by selecting genotypes best able to exploit the environment.

Microbiological diagnostic testing in the treatment of periodontal diseases

A variety of microbiological diagnostic tests are available for clinicians to use for evaluation of patients with periodontal disease. Each one has its own unique set of advantages and disadvantages, and probably the most useful information for the clinician can be obtained using a combination of the various analytic methods. The tests appear to have their greatest utility when used on patients with chronic or aggressive periodontitis who do not respond favorable to conventional mechanical therapy. The major limitation of all microbiological tests is that the information obtained is relevant to the site sampled, and may not be representative of the microflora of the entire dentition. However, since it is often only specific sites that do not respond to initial therapy, knowing the constituents of the microflora that populate these sites is clinically relevant.

Multilocus sequence analysis of Porphyromonas gingivalis indicates frequent recombination

In this study, the genetic relationship of 19 Porphyromonas gingivalis isolates from patients with periodontitis was investigated by multilocus sequence analysis. Internal 400-600 bp DNA fragments of the 10 chromosomal genes ef-tu, ftsQ, hagB, gpdxJ, pepO, mcmA, dnaK, recA, pga and nah were amplified by PCR and sequenced. No two isolates were identical at all 10 loci. Phylogenetic analyses indicated a panmictic population structure of P. gingivalis. Split decomposition analysis, calculation of homoplasy ratios and analyses of clustered polymorphisms all indicate that recombination plays a major role in creating the genetic heterogeneity of P. gingivalis. A standardized index of association of 0.0898 indicates that the P. gingivalis genes analysed are close to linkage equilibrium.

Relationship Between Transmission ofPorphyromonas gingivalisandfimAType in Spouses

BACKGROUND

Porphyromonas gingivalis is one of the major microbial pathogens associated with chronic periodontitis. To eradicate such pathogens by periodontal therapy, it is essential to clarify the source of infection. Recent findings suggest that the genotype of the fimbriae is one of the important factors in infection by P. gingivalis. The objectives of the present study were to investigate the transmission of P. gingivalis between spouses and to determine the relationship between P. gingivalis fimA type and colonization.

METHODS

A total of 14 couples were selected to investigate the transmission of P. gingivalis and its association with the fimA types. To examine the distribution of fimA type in the general population, 32 subgingival plaque samples from 47 patients with periodontitis were also tested. The transmission of P. gingivalis strains was determined by using pulsed field gel electrophoresis (PFGE). P. gingivalis strains isolated from the couples and subgingival dental plaque samples were studied for fimA classification.

RESULTS

The PFGE patterns of P. gingivalis strains from matched husbands and wives were identical for six of the 14 couples. In five of these six couples (83.3%), P. gingivalis strains harboring the type II fimA gene were present. The proportion of type II fimA in the strains isolated from couples with probable intrafamilial transmission was significantly higher than that in patients with periodontitis or in the group of samples isolated from one member of a couple.

CONCLUSION

This study suggests that fimA type II, even though widely distributed in patients with periodontitis, may be an important factor in the transmission of P. gingivalis between spouses.

Distribution of Bacteroides forsythus genotypes in a Japanese periodontitis population

Bacteroides forsythus is an important pathogen in periodontal diseases and has been associated with advanced and refractory periodontitis. The difficulties associated with culturing this species have meant that the distribution and pathogenic mechanisms of B. forsythus remain unclear. In this study, the arbitrarily primed polymerase chain reaction (AP-PCR) method was used to investigate the genotype distribution of B. forsythus in a Japanese periodontitis population, as well as the relationship between AP-PCR genotypes and periodontal status. B. forsythus reference strain, ATCC 43037T and 137 clinical bacterial isolates from 64 subjects were separated into 11 distinct AP-PCR genotypes using a single randomly-sequenced primer, 5'-CCGGCGGCG-3' (A-05). The majority (80.9%) of B. forsythus strains examined belonged to AP-PCR genotypes I, II, III and IV (accounting for 39.7%, 20.6%, 10.3% and 10.3%, respectively). Types I and III primarily consisted of isolates from chronic periodontitis subjects (80.8% and 85.7%, respectively), while Types II and IV consisted mainly of isolates from aggressive periodontitis subjects (85.7% and 100%, respectively). Except for three subjects who harbored two different B. forsythus genotypes in the oral cavity, all subjects only infected with one genotype intraindividually. These results demonstrate that the AP-PCR method is useful for genotypic analysis of B. forsythus. This species showed a genetic diversity among the investigated population. A clonal nature of B. forsythus infection is suggested. Furthermore, different AP-PCR genotypes of B. forsythus appear to be associated with different types of periodontitis.

Genetic diversity of Porphyromonas gingivalis and its possible importance to pathogenicity

During recent years much effort has been put into understanding the genetic composition of the oral populations of black-pigmented anaerobic bacteria. One of them, Porphyromonas gingivalis, is a putative periodontopathogenic organism considered to be particularly relevant in the etiology of adult periodontitis. It has been shown in studies using molecular typing methods that most bacterial populations consist of numerous genetic clones, and that only a small proportion of these clones cause disease. Elucidation of a possible association of genotypic profiles with either disease or clinical healthy condition is important for understanding the pathogenic characteristics of bacteria. Studies addressing this issue as it relates to P. gingivalis are reviewed in the present article. Genotypic characterization of P. gingivalis strains has revealed extensive heterogeneity in natural populations of this bacterium. Some of the potential virulence factors of P. gingivalis have been purified and cloned and methods have been established to identify their genes. Although no studies have clearly defined the relationship between a specific genotype of P. gingivalis and periodontal status of the host, it seems that molecular typing tools, which are undergoing rapid improvements, will allow us to distinguish between virulent and avirulent strains of the same species in the near future.

An Examination of ‘Unidentified’Prevotella (Formerly PINLO) using RAPD-PCR and Partial 16S rRNA Gene Sequencing

Prevotella intermedia- and Prevotella nigrescens-like organisms (PINLO) have been described as organisms which are phenotypically and biochemically similar to P. intermedia and P. nigrescens and the species P. pallens was created to include some of them. Other PINLO groups which do not fit the definition of P. pallens exist, and in this study these 'unidentified' Prevotella sp. were compared with P. corporis, P. intermedia, P. nigrescens and P. pallens using commercial identification kits, GLC, RAPD-PCR and partial 16S rRNA gene sequencing. The Rapid ID 32 A and the RapID ANA II system both identified all 'unidentified' Prevotella as P. intermedia. Similarly they gave this identification to all the species tested (with the exception of P. corporis using the RapID ANA II system) clearly demonstrating biochemical similarities. Gas liquid chromatography (GLC) analysis of the volatile end-products of fermentation could not distinguish between strains. RAPD-PCR using arbitrary primer L10 demonstrated intra-species homogeneity within PINLO strains with amplification profiles which differed from other Prevotella species tested. Cluster analysis of the amplification profiles confirmed species divisions and yielded a distinct 'unidentified' Prevotella cluster. Comparison of partial 16S rDNA sequences displayed 98% sequence similarity between the 'unidentified' Prevotella strains, although 2 strains, HST 1156 and HST 2160 displayed 100% identity. The highest similarity between groups was seen between 'unidentified' Prevotella strains and P. corporis (approximately 94% similarity). The DNA techniques used here confirm that 'unidentified' Prevotella strains are distinct from the other species of Prevotella tested, including P. pallens. Partial 16S rDNA sequence comparisons suggested a close relationship with P. corporis.

Heterogeneity of the prtC gene of Porphyromonas gingivalis

In this study, the nucleotide sequences of the prtC genes of six clinical Porphyromonas gingivalis isolates obtained from patients with periodontitis and from reference strain 53977 were determined. All analyzed genes were heterogeneous in their nucleotide composition and differed in up to 13 nucleotides. Moreover, substantial differences were found in comparison to prtC of reference strain 53977. The prtC genes of 45 Porphyromonas gingivalis isolates were amplified by polymerase chain reaction (PCR) and the PCR products were also digested with restriction endonucleases Tsp509I, NlaIII and DraII (PCR-restriction fragment-length polymorphism). Nine different restriction pattern combinations were observed, with four being most frequent (28.9%, 26.7%, 17.8% and 11.1%). The data presented here demonstrates that prtC genes are heterogeneous in their nucleotide sequence and therefore may be used as a target for molecular epidemiological studies. The observed heterogeneity of prtC genes may be a result of microevolution processes.

Identification of Porphyromonas gingivalis strains by heteroduplex analysis and detection of multiple strains

Heteroduplex analysis has been used extensively to identify allelic variation among mammalian genes. It provides a rapid and reliable method for determining and cataloging minor differences between two closely related DNA sequences. We have adapted this technique to distinguish among strains or clonal types of Porphyromonas gingivalis. The ribosomal intergenic spacer region (ISR) was amplified directly from a subgingival plaque sample by PCR with species-specific primers, avoiding the need for culturing the bacteria. The PCR products were then directly compared by heteroduplex analysis with known strains of P. gingivalis for identification. We identified 22 distinct but closely related heteroduplex types of P. gingivalis in 1,183 clinical samples. Multiple strains were found in 34% of the samples in which P. gingivalis was detected. Heteroduplex types were identified from these multistrain samples without separating them by culturing or molecular cloning. PCR with species-specific primers and heteroduplex analysis makes it possible to reliably and sensitively detect and identify strains of P. gingivalis in large numbers of samples.

Sequencing of the ribosomal intergenic spacer region for strain identification of Porphyromonas gingivalis

The ribosomal intergenic spacer regions (ISRs) of 19 laboratory strains and 30 clinical samples of Porphyromonas gingivalis were amplified by PCR and sequenced to provide a strain identifier. The ISR is a variable region of DNA located between the conserved 16S and 23S rRNA genes. This makes it an ideal locus for differentiation of strains within a species: primers specific for the conserved flanking genes were used to amplify the ISR, which was then sequenced to identify the strain. We have constructed a P. gingivalis ISR sequence database to facilitate strain identification. ISR sequence analysis provides a strain identifier that can be easily reproduced among laboratories and catalogued for unambiguous comparison.

Clonal diversity of Actinobacillus actinomycetemcomitans isolates from young adults with minimal periodontal disease

Actinobacillus actinomycetemcomitans is a major periodontal pathogen which is associated with both early-onset periodontitis and adult cases refractory to conventional periodontal therapy, although the organism has also been shown to be widely distributed among dentate healthy individuals. The observed disease status may be associated with a variation in virulence of different strains or clones. The aim of the present study was to analyse genotype distribution as assessed by an arbitrarily primed polymerase chain reaction (AP-PCR) among 51 isolates of A. actinomycetemcomitans recovered from more than 200 young adult recruits with no or minor periodontal disease. In addition, isolates from 25 periodontitis patients as well as reference strains were genotyped. Primers amplifying (i) a specific sequence in the ltxA region, (ii) a specific 16S rRNA sequence and (iii) sequences in the leukotoxin promoter region were used to verify species identity of the strains. Three random oligonucleotide primers were employed to analyse genomic polymorphisms of the organism by means of PCR. A total of 19 genotypes could be distinguished, which were grouped by cluster analysis into 5 major clusters based on genetic similarity and a complete linkage sort. Whereas 3 clusters assembled A. actinomycetemcomitans genotypes isolated from both healthy subjects and periodontitis patients, one cluster containing 4 different genotypes exclusively comprised isolates from healthy or gingivitis subjects. Another cluster with 2 genotypes consisted of strains originating from periodontitis patients (p < 0.05). One strain characterized by a specific 530 bp deletion in the promoter region of the leukotoxin region was identified in a Ghanese patient with localized juvenile periodontitis. It was concluded that there is considerable clonal diversity of A. actinomycetemcomitans strains isolated from healthy or periodontally diseased subjects, and that genetically closely related groups might be associated with health or disease.

Genetic relatedness between oral and intestinal isolates of Porphyromonas endodontalis by analysis of random amplified polymorphic DNA

Genomic fingerprints from the DNA of 27 strains of Porphyromonas endodontalis from diverse clinical and geographic origins were generated as random amplified polymorphic DNA (RAPD) using the technique of PCR amplification with a single primer of arbitrary sequence. Cluster analysis of the combined RAPD data obtained with three selected 9- or 10-mer-long primers identified 25 distinct RAPD types which clustered as three main groups identifying three genogroups. Genogroups I and II included exclusively P. endodontalis isolates of oral origin, while 7/9 human intestinal strains of genogroup III which linked at a similarity level of 52% constituted the most homogeneous group in our study. Genotypic diversity within P. endodontalis, as shown by RAPD analysis, suggests that the taxon is composed of two oral genogroups and one intestinal genogroup. This hypothesis remains to be confirmed.

Survival of oral bacteria

The global distribution of individual species of oral bacteria demonstrates their ability to survive among their human hosts. Such an ubiquitous existence is the result of efficient transmission of strains and their persistence in the oral environment. Genetic analysis has identified specific clones of pathogenic bacteria causing infection. Presumably, these express virulence-associated characteristics enhancing colonization and survival in their hosts. A similar situation may occur with the oral resident flora, where genetic variants may express specific phenotypic characteristics related to survival. Survival in the mouth is enhanced by dental plaque formation, where persistence is associated with the bacteria's capacity not only to adhere and grow, but also to withstand oxygen, wide fluctuations in pH and carbohydrate concentration, and a diverse array of microbial interactions. Streptococcus mutans has been discussed as a 'model' organism possessing the biochemical flexibility that permits it to persist and dominate the indigenous microflora under conditions of stress.

Arbitrarily primed polymerase chain reaction fingerprinting for the genotypic identification of mutans streptococci from humans

Determining whether two strains of bacteria are unique, identical or clonally related depends upon comparisons of phenotypic and/or genotypic traits. Individual isolates can then be grouped according to differences or similarities among those traits. One method of genotyping strains of bacteria is commonly referred to as chromosomal DNA fingerprinting. Previously, we generated chromosomal DNA fingerprints of mutans streptococci to study the transmission of this organism within families. Here, we developed and evaluated an arbitrarily primed polymerase chain reaction (AP-PCR) method for the genotypic characterization of mutans streptococci. Results were compared to those derived from the more conventional chromosomal DNA fingerprinting method. First, we showed that randomly selected clinical isolates displayed a unique banding profile by both methods; the mean similarity indices between DNA fragment patterns were 0.69 for chromosomal DNA fingerprinting and 0.74 for AP-PCR. This indicated that AP-PCR demonstrated less diversity than chromosomal DNA fingerprinting. Subsequently, we tested the agreement between chromosomal DNA fingerprinting and AP-PCR in determining genotypic similarities among 21 mutans streptococci strains obtained from 10 mother-child pairs, and 5 mutans streptococci strains from 5 fathers. The Kappa value for agreement was 0.88. We conclude that AP-PCR, which generates patterns of 8 to 12 amplicons, is capable of distinguishing strains of mutans streptococci among non-related individuals. Moreover, AP-PCR can discern both homogeneity and heterogeneity of mutans streptococci genotypes among mother and child pairs. Overall, we found that AP-PCR gave results comparable to those of chromosomal DNA fingerprinting.

Can one acquire periodontal bacteria and periodontitis from a family member?

Recent findings suggest that two major periodontal pathogenes, Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis, are transmitted among family members. The authors discuss the evidence of person-to-person transmission of periodontal bacteria, the significance of saliva as a vehicle of transmission and the methods of verifying clonal similarity of bacterial strains obtained from family members. The authors also discuss the prophylactic and therapeutic implications of the person-to-person spread of periodontal bacteria.

Arbitrarily primed polymerase chain reaction fingerprinting and clonal analysis of oral Fusobacterium nucleatum isolates

F. nucleatum is the most commonly isolated microorganism from subgingival plaque, but the role of this microorganism in periodontal diseases remains undefined. Arbitrarily primed polymerase chain reaction (AP-PCR) was evaluated as a method for fingerprinting F. nucleatum isolates and for use in clonal analysis. Pulsed field gel electrophoresis was used to further differentiate F. nucleatum isolates, with identical AP-PCR patterns. Extremely heterogeneous AP-PCR fingerprints were observed among the 98 F. nucleatum isolates, with 36 different genotypes observed with primer C1 and 30 different genotype detected with primer C2. Combining the results of the AP-PCR genotype analysis from C1 and C2 primer amplifications revealed that up to 7 different genotypes could be distinguished from isolates from the same oral cavity and that up to 4 different genotypes were observed within a single site. An intense amplicon at approximately 450 bp generated in AP-PCR amplification with primer C2 was associated with F. nucleatum subsp. nucleatum (ATCC 25586) and with 15 F. nucleatum isolates from diseased sites and 2 isolates from healthy sites. Pulsed field gel electrophoresis confirmed the AP-PCR genotypes and demonstrated increased discriminatory power over AP-PCR. The results indicated that AP-PCR and pulsed field gel electrophoresis provide a simple and sensitive means for differentiating oral F. nucleatum isolates and further demonstrate the heterogeneity of this species. These techniques may serve as useful tools in the clonal and epidemiological analysis of F. nucleatum isolates, which may help define the role of these microorganisms in periodontal diseases.

Likelihood of transmitting Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis in families with periodontitis

This study examined the frequency of spouse-to-spouse and parent-child transmission of the periodontal pathogens Actinobacillus actinomycetemcomitans (124 subjects in 47 families) and Porphyromonas gingivalis (78 subjects in 31 families). The two test organisms were recovered from subgingival and tongue surface specimens using established microbiological techniques. Arbitrarily primed polymerase chain reaction (AP-PCR) was used to genetically characterize isolates of the test species. The probability of isolating identical AP-PCR types of A. actinomycetemcomitans and P. gingivalis in family members by chance was estimated from the AP-PCR genotype distribution of the two species among unrelated individuals. A probability of 5% or less for occurrence by chance alone suggests intra-familial transmission. With a bacterium-positive spouse, A. actinomycetemcomitans revealed inter-spousal transmission in 4/11 (36%) married couples and P. gingivalis in 2/10 (20%) married couples. Parent-child transmission of A. actinomycetemcomitans took place in 6/19 (32%) families. P. gingivalis was not transmitted from parent to child in any of the study families. The intra-familial transmission of A. actinomycetemcomitans and P. gingivalis may in part explain a familial pattern of periodontitis and may have important prophylactic and treatment implications.

Similarity of salivary and subgingival Prevotella intermedia and Prevotella nigrescens isolates by arbitrarily primed polymerase chain reaction

The distribution and the genetic similarity of Prevotella intermedia and Prevotella nigrescens in saliva and in subgingival samples recovered from the same subject were studied in 16 subjects with different periodontal status. The isolates (4 salivary and 4 subgingival P. intermedia/nigrescens group isolates per subject) were identified to species level by hybridization with species-specific oligonucleotide probes, and the clonal analysis was performed using arbitrarily primed polymerase chain reaction (AP-PCR) (all isolates) and ribotyping (isolates from 5 subjects). In addition, the applicability of AP-PCR in differentiating between P. intermedia and P. nigrescens species was tested using 18 P. intermedia and 20 P. nigrescens isolates from 34 subjects. P. intermedia was detected in 7 and P. nigrescens in 14 of the 16 subjects. In all subjects the same species was found both in saliva and in subgingival plaque. In 15 of the 16 subjects, similar AP-PCR types of P. intermedia and/or P. nigrescens between salivary and subgingival samples were found. The salivary and subgingival isolates that were similar by AP-PCR were indistinguishable also by ribotyping. The AP-PCR analysis revealed a P. intermedia or P. nigrescens species-specific AP-PCR product in most isolates. This study indicates that both P. intermedia and P. nigrescens were found both in salivary and in subgingival samples, and both sampling sites within the same individual were usually colonized with identical AP-PCR types of the species. Thus, in addition to a subgingival sample a salivary sample seems to be suitable for detection and clonal analysis of these species. The AP-PCR method proved to be a simple method applicable for differentiation and clonal analysis of P. intermedia and P. nigrescens.

Clonal diversity of Streptococcus mitis biovar 1 isolates from the oral cavity of human neonates

The clonal diversity of 101 isolates of the pioneer bacterium Streptococcus mitis biovar 1 obtained from the oral cavities of 40 human neonates 1 to 3 days, 2 weeks, and 1 month postpartum was examined by using rRNA gene restriction patterns. There was a high degree of genetic diversity, with the 101 isolates comprising 93 unique PvuII ribotypes. There were eight identical pairs of ribotype patterns, and seven of the eight pairs were obtained from individual neonates. Only one identical pair comprised isolates obtained from different neonates. In all but two cases, isolates with matching ribotypes were obtained at one visit. Two pairs of isolates with matching ribotype patterns were obtained from neonates on successive visits. The ribotype patterns of the isolates were examined by cluster analysis. The isolates forming each cluster were very similar, yet each cluster was well separated from its neighbors. When several isolates were obtained from individual neonates at a particular visit, in some instances they were contained in a single cluster, whereas in other cases each isolate was contained in a separate cluster. Isolates obtained from individual neonates on successive visits tended to be contained in different clusters. This high degree of diversity, which has been observed in other mucosal commensal bacteria, may serve as a mechanism for avoiding immune elimination of these bacteria.

Clonal diversity of oral Eikenella corrodens within individual subjects by arbitrarily primed PCR

The genetic diversity of 205 Eikenella corrodens isolates recovered from dental plaque, mucosal surfaces, and saliva of 24 subjects was examined by arbitrarily primed PCR. Twenty-two subjects were colonized by multiple clones (range, two to eight; mean, 3.7). This study demonstrates the utility of arbitrarily primed PCR for clonal analysis of E. corrodens and the multiclonal colonization of E. corrodens in the oral cavity.

Analysis of the prtP gene encoding porphypain, a cysteine proteinase of Porphyromonas gingivalis

The cloning and sequencing of the gene encoding porphypain, a cysteine proteinase previously isolated from detergent extracts of the Porphyromonas gingivalis W12 cell surface, are described. The prtP gene encoded a unique protein of 1,732 amino acids, including a putative signal sequence for protein secretion. The predicted molecular mass for the mature protein was 186 kDa, which was close to the observed molecular mass of 180 kDa. There was one copy of prtP in the genomes of seven P. gingivalis strains examined. The gene was located 5' to a region with a high degree of homology to the insertion element IS1126 in P. gingivalis W12. The PrtP protein had regions of high homology to HagA, a hemagglutinin of P. gingivalis, and to several purported proteinases of P. gingivalis that have Arg-X specificity. A detailed comparison of genes encoding the latter and cpgR suggested that rgp-1, prpR1, prtR, agp, cpgR, and possibly prtH were derived from identical genetic loci. Although an rgp-1-like locus was detected in seven P. gingivalis strains by Southern blot analyses, agp and cpgR were not detected, not even in the strains from which they were originally isolated. In addition, at least 20 copies of a repeat region common to PrtP, the Rgp-1-like proteins, and HagA were observed in each of the seven genomes examined. The repeat region hybridization patterns for strains W83 and W50 were very similar, and they were identical for strains 381 and ATCC 33277, providing further evidence that these strains are closely related genetically.

Clonal diversity of the taxon Porphyromonas gingivalis assessed by random amplified polymorphic DNA fingerprinting

A total of 97 strains of the periopathogen Porphyromonas gingivalis were collected. This collection included laboratory strains and clinical isolates of human origin with diverse clinical and geographical origins. Biological diversity was further increased by including 32 strains isolated from the oral cavities of nine different animal species. Genomic fingerprints of the 129 strains were generated as random amplified polymorphic DNAs (RAPDs) by the technique of PCR amplification with a single primer of arbitrary sequence. Four nonameric oligonucleotides were used as single primers, and the banding patterns of the DNA products separated on agarose gels were compared after ethidium ethidium bromide staining. Distance coeffients based on the positions of the major DNA fragments were calculated, and dendrograms were generated. We identified 102 clonal types (CTs) that could be assembled into three main groups by cluster analysis by the unweighted pair group method with mathematic averages. Group I (n = 79 CTs) included all 97 human strains and 6 monkey isolates. The strains in group II (n = 22 CTs) and III (n = 1 CT) were strongly differentiated from those in group I and included only strains of animal origin; they likely represent two cryptic species within the present P. gingivalis taxon. We observed that strains from Old World monkeys clustered together with the human genotype, whereas strains from New World monkeys clustered with the animal genotype. Our results with human strains also indicated that (i) the population structure is basically clonal, (ii) no dominant or widespread CT could be observed, and (iii) no relationship could be established between specific clusters of CTs and the periodontal status of the host. Our results corroborate previous findings by B. G. Loos, D. W. Dyer, T. S. Whittam, and R. K. Selander (Infect. Immun. 61:204-212, 1993) and suggest that P. gingivalis should be considered a commensal of the oral cavity acting as an opportunistic pathogen. Our results are not consistent with the hypothesis that only a few virulent clones of P. gingivalis are associated with disease.