Serological studies of Porphyromonas (Bacteroides) gingivalis and correlation with enzyme activity

The Antimicrobial Susceptibility of Porphyromonas gingivalis: Genetic Repertoire, Global Phenotype, and Review of the Literature

The in vitro antimicrobial susceptibility of 29 strains of the major periodontal pathogen Porphyromonas gingivalis and three P. gulae (as an ancestor) to nine antibiotics (amoxicillin, amoxicillin/clavulanate, clindamycin, metronidazole, moxifloxacin, doxycycline, azithromycin, imipenem, and cefoxitin) was evaluated by E-testing of minimal inhibitory concentration (MIC) according to international standards. The results were compared with 16 international studies reporting MICs from 1993 until recently. In addition, 77 currently available P. gingivalis genomes were screened for antimicrobial resistance genes. E-testing revealed a 100% sensitivity of P. gingivalis and P. gulae to all antibiotics. This was independent of the isolation year (1970 until 2021) or region, including rural areas in Indonesia and Africa. Regarding studies worldwide (675 strains), several method varieties regarding medium, McFarland inoculation standards (0.5-2) and incubation time (48-168 h) were used for MIC-testing. Overall, no resistances have been reported for amoxicillin + clavulanate, cefoxitin, and imipenem. Few strains showed intermediate susceptibility or resistance to amoxicillin and metronidazole, with the latter needing both confirmation and attention. The only antibiotics which might fail in the treatment of P. gingivalis-associated mixed anaerobic infections are clindamycin, macrolides, and tetracyclines, corresponding to the resistance genes erm(B), erm(F), and tet(Q) detected in our study here, as well as fluoroquinolones. Periodical antibiotic susceptibility testing is necessary to determine the efficacy of antimicrobial agents and to optimize antibiotic stewardship.

CXXC5 orchestrates Stat3/Erk/Akt signaling networks to modulate P. gingivalis-elicited autophagy in cementoblasts

The keystone pathogen Porphyromonas gingivalis (P. gingivalis) elicits inflammation and autophagy in periodontal tissues. Transcription factor CXXC-type zinc finger protein 5 (CXXC5) and various signals are sensitive to P. gingivalis invasion. Herein, we investigated the P. gingivalis-elicited autophagy activity, the contribution of CXXC5, and the involvement of signals in cementoblasts, tooth root surface cells crucial in periodontal and periapical regions. After coculture with P. gingivalis, cementoblasts exhibited inflammatory cytokine increase, light chain 3(LC3)-I/II conversion, autophagosome activation, and CXXC5 reduction. Cementoblasts with loss and gain of CXXC5 were developed. CXXC5 silencing suppressed autophagy and inflammation, thereby partially compensating for the effects of P. gingivalis, and vice versa. We then screened potential signals and verified the positive participation of Stat3/Akt/Erk networks through specific inhibitor employment. P. gingivalis and CXXC5 induced autophagy through Beclin1 and Atg5 activation. Intriguingly, Annexin V/PI assay and EdU detection revealed that P. gingivalis promoted apoptosis and repressed cell proliferation. In sum, coculture with P. gingivalis enhanced autophagy activity in cementoblasts, which was partially suppressed by CXXC5 downregulation and mediated by Jak/Stat3, PI3K-Akt, and Erk1/2 signaling. This process probably influenced cell apoptosis and proliferation.

Phenotypes, serotypes and antibiotic susceptibility of Swedish Porphyromonas gingivalis isolates from periodontitis and periodontal abscesses

This study was conducted to reveal phenotypic, serological subtypes and antibiotic susceptibility among fresh isolates of Porphyromonas gingivalis in a Swedish population with periodontitis and periodontal abscess. Fifty-five subgingival strains were isolated and tentatively designated as P. gingivalis from 55 consecutive paper-point samples taken from 51 patients with periodontitis (at least one site with >6-mm pocket depth) in Sweden and were sent in for microbiological evaluation. Eight P. gingivalis strains from periodontal abscesses were also included. Four P. gingivalis strains served as reference and another four type strains were included. The strains were characterized by colony morphology, biochemical tests, enzyme profile, gas-liquid chromatography and antibiotic susceptibility. The strains were further characterized for whole cell protein profiles using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and were identified to serotype by specific monoclonal antibodies. Among the 55 P. gingivalis strains 35 had smooth (S), 13 rough (R) and seven semi-rough colony morphologies. All strains were phenotypically homogeneous in biochemical tests, enzyme profile and antibiotic susceptibility. All strains produced phenylacetic acid and alpha-fucosidase. Almost all (96%) of the subgingival strains, but relatively fewer (62%) of the abscess strains, belonged to serotype A. Two subgingival and three abscess strains were classified as serotype B. No specific SDS-PAGE protein profiles were recorded for the two serotypes. The P. gingivalis strains from Swedish periodontitis cases showed homogeneity in terms of biochemical phenotypes and antibiotic susceptibility patterns. The strains fell into two serotypes, of which serotype A predominated in the periodontitis cases and serotype B was overrepresented in periodontal abscesses.

Fimbriae of Porphyromonas gingivalis induce opsonic antibodies that significantly enhance phagocytosis and killing by human polymorphonuclear leukocytes

Porphyromonas gingivalis has been strongly implicated in the pathogenesis of human periodontitis. Fimbriae mediate adherence and colonization of the oral cavity by this organism and may, therefore, have potential for use as antigen in an anti-P. gingivalis vaccine. The purpose of our study was to determine whether P. gingivalis fimbriae have opsonic target sites and whether they are accessible on the cell surfaces and cross-reactive among P. gingivalis fimbrial types and serotypes. Rabbits were immunized with a vaccine. The antiserum reacted with a 43-kDa fimbrillin monomer and a 43-kDa component in whole-cell sonicates of P. gingivalis 33277, but it showed only very weak reactivity in the 43-kDa region of Western blots of a whole-cell sonicate of strain DPG3, a mutant that does not express functional fimbriae. The antibody enhanced chemiluminescence approximately six-fold relative to preimmune serum values and significantly enhanced phagocytosis and killing of P. gingivalis 33277 by human polymorphonuclear leukocytes. Peak opsonic activity was observed at week 6 followed by a plateau that remained until week 16. The fimbria-deficient mutant DPG3 did not bind antifimbrial antibody and was not opsonized, whereas strain 381, the parent of the mutant, was opsonized. The specific antibody bound to and opsonized P. gingivalis strains 33277 and 381 (fimbria type I) but not W50, A7A-1-28, 9-14K-1 or FAY-19M-1 (fimbrial types II-V). Specific antibody bound to strain 2561 (fimbrial type I) but, as assessed by chemiluminescence, did not opsonize it. While fimbriae have opsonic target sites that are accessible on P. gingivalis cell surfaces, the relevant opsonic target sites do not appear to be shared across serotypes or fimbrial types. Thus, a vaccine containing, as antigen, fimbrial protein from a single P. gingivalis strain would likely be ineffective against infections by P. gingivalis strains expressing other fimbrial types.

Functional characteristics of antibodies induced by Arg-gingipain (HRgpA) and Lys-gingipain (Kgp) from Porphyromonas gingivalis

Arginine-specific gingipain (HRgpA) and lysine-specific gingipain (Kgp), enzymes produced by Porphyromonas gingivalis, may be candidates for an anti-P. gingivalis vaccine. The purpose of our study was to determine whether HRgpA and Kgp have opsonic target sites and whether these sites are available and accessible on intact P. gingivalis cells. Rabbits were used to generate polyclonal antibodies to both proteins. Animals were immunized and immunoglobulin G (IgG) fractions were isolated from preimmune and immune sera. Functional characteristics of the antibodies were assessed by determining antibody titers by enzyme-linked immunosorbent assay (ELISA), generating Western immunoblots, and measuring antibody enhancement of P. gingivalis opsonization, phagocytosis and killing by polymorphonuclear leukocytes (PMN) of intact cells of strains of P. gingivalis representative of the four serotypes. Strains studied included 33277 (serotype A), A7A1-28 (serotype B), W50 (serotype C) and 381 (serotype D). Both HRgpA and Kgp induced high titers of IgG antibody. Anti-HRgpA and anti-Kgp bound to both HRgpA and Kgp demonstrating a large proportion of shared antigenic epitopes. The two antibodies bound equally well to all four P. gingivalis serotypes with titers ranging from 77 to 205 ELISA units when compared to preimmune IgG set at 1 ELISA unit. The immunoblot patterns of binding of the two antibodies to HRgpA and Kgp and to sonicates of the four P. gingivalis serotypes were virtually identical. Both antibodies detected components in HRgpA at 27, 35 and 45 kDa and in Kgp at 27, 32, 35, 40 and 55 kDa. The antibodies also detected components at or near these same positions in addition to multiple high molecular mass components in the cell sonicates of P. gingivalis. Both proteins induced antibodies that significantly enhanced opsonization as assessed by chemiluminescence, with values ranging from 130 mV to 375 mV for anti-HRgpA IgG and from 240 mV to 475 mV for anti-Kgp IgG. Both antibodies significantly enhanced PMN-mediated bacterial killing of the four P. gingivalis serotypes, although the percentage of killing varied among the serotypes (24-81% for anti-HRgpA and 37-89% for anti-Kgp). Thus, both HRgpA and Kgp express opsonic target sites and induce high titers of antibodies that opsonize and enhance killing of all four serotypes of P. gingivalis. These two proteins appear to be potential candidate antigens for an anti-P. gingivalis vaccine.

Immunoglobulin G response of periodontitis patients to Porphyromonas gingivalis capsular carbohydrate and lipopolysaccharide antigens

Porphyromonas gingivalis clonal types that participate in periodontal infections express serologically distinct surface antigens. This investigation sought to determine whether serum antibodies titers against the serotype-specific capsular carbohydrate K antigen and lipopolysaccharide antigens of P. gingivalis might reveal which serotypes are most likely to be responsible for subgingival infections in subjects with adult periodontitis. Immunoglobulin G (IgG) titers to purified K antigen and lipopolysaccharide from different P. gingivalis strains were measured by ELISA for 28 healthy controls and 51 patients with periodontal pockets known to be infected with genetically and serologically distinct P. gingivalis clonal types. Titers to purified K antigen from strains W50, HG184, A7A1-28, 49417, HG1690 and HG1691, representing serotypes K1-K6, respectively, and lipopolysaccharide from strains 381, HG1691 and W50, representing serotypes O1-O3, respectively, were measured for all subjects. Chi-square likelihood ratios, Mann-Whitney tests and receiver-operating characteristic sensitivity-specificity plots were used to compare the accuracy with which titer results for different target antigens classified subjects with or without disease. Results from assays targeting K2, K3, K4, K5, O1 and O2 generally gave poor diagnostic accuracy, whether evaluated separately or as summed titer pairs corresponding to the K/O combinations actually expressed by the target antigen parent strains. Exceptions were O3 (from W50) and K5+O2 (both from HG1690), which gave moderate accuracy in classifying subjects. In contrast, highly significant diagnostic accuracy was achieved using individual K1 (W50) and K6 (HG1691) titer data and K1+O3 (W50) and K6+O2 (HG1691) titer sum values. These observations suggest that P. gingivalis clonal types expressing K/O serotypes matching those of W50 (K1/O3) and HG1691 (K6/O2) are more likely than others to participate in periodontal infections in adult periodontitis patients and thus are more likely than others to express relevant virulence factors.

Prevalence of specific genotypes of Porphyromonas gingivalis fimA and periodontal health status

Porphyromonas gingivalis fimA gene encoding fimbrillin, a subunit of fimbriae, has been classified into 5 genotypes (types I to V) based on their nucleotide sequences. Here, we investigated the relationship between the prevalence of these fimA genotypes and periodontal health status in adults. Dental plaque specimens obtained from 380 periodontally healthy adults and 139 periodontitis patients were analyzed by the PCR method. P. gingivalis was detected in 36.8% of the healthy subjects and in 87.1% of the periodontitis patients. Among the P. gingivalis-positive healthy adults, the most prevalent fimA type was type I (76.1%), followed by type V. In contrast, a majority of the periodontitis patients carried type II fimA organisms (66.1%), followed by type IV. The univariate analysis illustrated that periodontitis was associated with the occurrences of type I fimA (OR 0.16), type II (OR 44.44), type III (1.96), type IV (13.87), and type V (1.40). These findings clearly indicate that there are both disease-associated and non-disease-associated strains of P. gingivalis, and that their infectious traits influencing periodontal health status could be differentiated based on the clonal variation of fimA genes.

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.

Antigenic cross-reactivity among Porphyromonas gingivalis serotypes

The goal of our research program is to develop a Porphyromonas gingivalis vaccine. Vaccine development requires identification of antigenic components shared by the many clonal types of P. gingivalis. The purpose of the present study was to evaluate the extent and nature of antigenic cross-reactivity among serotypes of P. gingivalis and to identify shared antigenic components. Strains selected to represent serotypes A-D were 33277, A7A1-28 W50 and 381, respectively. Using intact cells, antibodies were raised in rabbits. Titers were assessed by enzyme-linked immunosorbent assay (ELISA) using intact cells as antigen, Western blots were prepared and biologic activity was measured as opsonization (chemiluminescence expressed as mV) and enhancement of phagocytosis and killing by polymorphonuclear leukocytes. Extensive cross-reactivity that varied greatly among serotypes was observed by ELISA. The Western blots showed an even greater extent of cross-reactivity, with shared protein components at approximately 140, 130, 37, 32 and 28 kDa and a shared variable molecular mass smear considered to be lipopolysaccharide and other carbohydrate. Additional protein components at 110, 85, 35 and 20 kDa appeared to be shared by some but not all serotypes. In the functional assays, strains 33277 and 381 were equally well opsonized by anti-33277 and anti-381 (500-650 mV) but opsonized to a much lesser extent by anti-A7A1-28 and anti-W50 (roughly 125 mV and 350 mV respectively). A7A1-28 and W50 were opsonized by all four immune sera almost equally but to a much lower extent (roughly 400 mV and 250 mV respectively). Enhancement of phagocytosis and killing in the presence of active complement mirrored opsonization with the exception that 381 was reasonably well opsonized by anti-A7A1-28 (400 mV) and anti-W50 (350 mV), but poorly killed. The protein components at 140, 130, 37 and 28 kDa shared by all of the four serotypes appear to have potential as vaccine candidate antigens.

Distribution and molecular characterization of Porphyromonas gingivalis carrying a new type of fimA gene

Fimbriae of Porphyromonas gingivalis are filamentous appendages on the cell surface and are thought to be one of the virulence factors. The fimA gene encoding the subunit protein of fimbriae, fimbrillin (FimA), was classified into four typeable variants (types I to IV). We previously examined the distribution of P. gingivalis in terms of fimA genotypes in periodontitis patients using a fimA type-specific PCR assay. However, some patients harbored P. gingivalis with untypeable fimA. In this study, we have cloned a new type (type V) of fimA from dental plaque samples. P. gingivalis with type V fimA was isolated from dental plaque of a periodontitis patient, and the isolate was named HNA-99. The deduced amino acid sequences were compared with those of type I P. gingivalis ATCC 33277, type II strain HW24D1, type III strain 6/26, and type IV strain HG564, and the homologies were found to be 45, 44, 43, and 55%, respectively. Southern blot analysis showed that the clinical isolate HNA-99 possessed P. gingivalis-specific genes sod and kgp. However, in terms of serological specificities, type V FimA showed a difference from other types of FimA. In addition, type V P. gingivalis bacteria were detected in 16.4% (12 of 73) of the P. gingivalis-positive patients with periodontitis by PCR assay using specific primers. Thus, a new type of fimA gene is now established, and the fimA genotyping could be useful in determining the disease-associated genotypes of P. gingivalis involved in the development of adult periodontitis.

Distribution of Porphyromonas gingivalis strains with fimA genotypes in periodontitis patients

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

Antigenic variation in Porphyromonas gingivalis ribotypes recognized by serum immunoglobulin G of adult periodontitis patients

We obtained clinical isolates of Porphyromonas gingivalis of known ribotype from patients diagnosed with adult periodontitis and used Western blot methodology to evaluate profiles of antigens recognized by IgG in heterologous and homologous patient sera. Our aims were to identify isolates belonging to different serogroups, to learn if serogroup membership is related to ribotype to assess variation in IgG responses of patients to antigens is homologous and heterologous ribotypes, and to determine the frequency of shared and variable antigens in different biochemical classes recognized across different serogroups and ribotypes. Blots of separation patterns of 28 isolates were developed in sera from patients and bound IgG was quantified by digital image densitometry. The membership of isolates in different serogroups was determined by correlation and hierarchical cluster analysis of isolate whole-cell IgG binding profiles. Two major isolate clusters, each with two subclusters, were found. Isolates within the same ribotype clustered together in some cases but not others. Homologous isolates ranked high in IgG binding levels relative to those from different patients irrespective of ribotype. Patient subgroups with IgG responses dominant for different ribotypes and serogroups were revealed by correlation analysis. The IgG binding profiles observed for individual protein and proteinase-resistant antigens across both homologous and heterologous isolates were very dissimilar. Furthermore, the frequency of antigens both shared across all ribotypes and recognized by IgG in patient sera was unexpectedly low. Only two protein antigens (Mr 44 kDa and 27 kDa) were strongly recognized across all ribotypes by different sera. We conclude that the IgG response of patients infected with a particular P. gingivalis serotype or ribotype is directed mainly against antigens that are not shared by other potentially infective clonal types.

Antigenic variation in Bacteroides forsythus detected by a checkerboard enzyme-linked immunosorbent assay

Evidence indicating that multiple serotypes of Bacteroides forsythus participate in rapidly progressing periodontal infections has not been reported previously. Our aim was to develop an assay for detecting subsets of B. forsythus clinical isolates which differ in serogroup membership and subsets of patients with immunoglobulin G (IgG) responses which differ in serogroup recognition. A checkerboard enzyme-linked immunosorbent assay (ELISA) was used to assess variation in the IgG binding profiles of 22 clinical isolates in sera from 28 patients with early-onset rapidly progressive periodontitis. To accommodate the maximum number of isolates and sera in a given assay run, a multiplate assay grid with standard 96-well microtest plates was established. Single dilutions of individual sera were placed in rows crossing columns of isolate-coated wells, and antigen-specific IgG immobilized in the wells was measured as ELISA absorbance. Pooled sera and isolates were assayed in parallel to serve as negative controls for variation in IgG binding profiles. Correlation and hierarchical cluster analysis of the absorbance data matrix showed that the isolates could be sorted into at least four clusters based on variations in their IgG binding profiles across different sera. Furthermore, at least two patient clusters were defined by variations in their serum IgG antigen recognition profiles across different isolates. We conclude that multiple serogroups of B. forsythus exist and that different serogroups are dominant in the antibody response of different patients. The method applied here could be used to serologically classify clinical isolates of other species which evoke a serum antibody response in patients.

Prevalence and distribution of six capsular serotypes of Porphyromonas gingivalis in periodontitis patients

Previous reports have described six serotypes based on K antigens in Porphyromonas gingivalis strains. The purpose of the present study was to investigate the prevalence and distribution of these serotypes in 185 patients with P. gingivalis-associated periodontitis. Polyclonal rabbit antisera, raised against each of the different type strains, were used in double-immunodiffusion and immunoelectrophoresis assays. In addition, a subset of 76 strains was investigated for the presence of capsular structures by means of the India ink and Bruce White staining techniques. These strains were also tested for auto-aggregation in phosphate-buffered saline (PBS). All six K serotypes were present in the study sample. In total, 84 (45.4%) patients were colonized with a K-typeable P. gingivalis strain with a predominance of types K5 (12%) and K6 (23.2%). A correlation was found between arbitrary age categories and the prevalence of currently known K serotypes, which were found in 60% of patients aged 12 to 30 years, in 49% of patients aged 31 to 50, and in 25% of patients aged 51 to 70 years. In the subset of 76 P. gingivalis strains, 32 (42.1%) were K-typeable. Fifty-three strains (69.7%) showed microscopic evidence of encapsulation, suggesting the existence of K serotypes other than K1 to K6. Twenty-one strains (27.6%) auto-aggregated in PBS and were not K-typeable, nor did they show any evidence of encapsulation. It was concluded that the majority of clinical P. gingivalis isolates is encapsulated and that encapsulation is associated with the presence of a K antigen. Auto-aggregation seems to be associated with the absence of a capsular structure and, consequently, the absence of a K antigen.

Detection of identical ribotypes of Porphyromonas gingivalis in patients residing in the United States, Sudan, Romania and Norway

Porphyromonas gingivalis has been isolated from periodontitis lesions in subjects from many geographical locations. The purpose of this investigation was to determine whether similar ribotypes of P. gingivalis could be detected among strains isolated in different countries. A total of 198 isolates of P. gingivalis were obtained from 52 periodontitis patients in Boston (130 isolates), Bergen, Norway (17 isolates), Khartoum, Sudan (26 isolates), and Bucharest, Romania (25 isolates). DNA was isolated from each strain, cut separately by the restriction endonucleases KpnI and PstI. The resulting preparations were subjected to electrophoresis in a 0.8% agarose gel using a Tris-acetate EDTA buffer. Uncut lambda and a 1000-bp fragment of 16S rRNA were included as internal standards in each lane. In addition, a HindIII digest of lambda was present in a separate lane in each run. The DNA fragments were transferred to a nylon membrane by downward capillary transfer. 16S rRNA bands were detected using a 1000-kb digoxigenin-labelled probe generated by a polymerase chain reaction. At the same time, a digoxigenin-labelled probe to lambda was employed to detect the internal and molecular weight standards. The bands were detected using antibody to digoxigenin conjugated to alkaline phosphatase and chemiluminescence. The positions of the bands relative to the internal standards were determined and normalized to correct for run-to-run variations, and the molecular weight of each band was determined by comparison with standards within each gel. The resulting data for the 2 enzymes were combined and subjected to cluster analysis using an average unweighted linkage sort. In some instances, isolates that appeared to be of identical ribotype using one endonuclease gave different ribotypes using the other. Strains of P. gingivalis within a subject were usually identical, except for 3 patients who harbored 2 different ribotypes/individual. All subsequent analyses employed a single ribotype strain for each subject. A total of 32 ribotypes were observed for isolates from distant countries. A total of 11.5% of the patients had isolates exhibiting the same ribotype: ribotype 7a. Identical ribotypes of P. gingivalis can be recovered from subgingival plaque samples of periodontitis patients in different countries.

Novel polysaccharide capsular serotypes in Porphyromonas gingivalis

Recently van Winkelhoff et al. (1) described 3 novel serotypes in virulent Porphyromonas gingivalis strains, which were based on different polysaccharide antigens. These antigens probably represent capsular structures and have been designated K1, K2 and K3. In the present study we report on 3 novel capsular serotypes, which are represented by P. gingivalis strains ATCC 49417, HG 1690 and HG 1691. The strains, isolated from patients with periodontitis, showed obvious encapsulation in wet India ink preparations. Thermostable antigens could be detected in the supernatant fractions of autoclaved cells. These antigens appeared to be negatively charged, sensitive to periodate degradation, and resistant to proteinase K treatment. On the basis of these characteristics we conclude that the antigens are probably extra-cellular polysaccharides representing a bacterial capsular structure. These K-antigens did not cross-react with K1, K2 or K3 immune-sera of P. gingivalis, with the exception of the K2 antiserum, which partially recognized K5- and K6-antigens. In contrast, K5 and K6 antisera did not react with the K2-antigen. After absorbtion of the K2 antiserum with cells of strains HG 1690 (K5) and HG 1691 (K6) cross-reactivity was no longer present. We propose these novel serotypes to be designated: K4 (ATCC 49417), K5 (HG 1960) and K6 (HG 1691).

Multiple restriction fragment length polymorphism genotypes of Porphyromonas gingivalis in single periodontal pockets

A total of 188 Porphyromonas gingivalis strains isolated from 13 periodontal pockets of 8 periodontitis patients were investigated by means of restriction fragment length polymorphism (RFLP) analysis using the fimA gene as a pobe. A total of 5 RFLP genotypes were identified, and over half of the isolates belonged to type I. Four of the 8 patients harbored only 1 RFLP genotype of P. gingivalis, and 1 patient harbored only 2 RFLP genotypes in different sites. On the other hand, in 3 other patients, multiple RFLP genotypes were found in single periodontal pockets. Further studies will be required to clarify whether multiple genotypes of P. gingivalis colonized a single periodontal pocket simultaneously or whether a mutation occurred in the fimbrilin gene locus of P. gingivalis.

Restriction fragment length polymorphism analysis of two hemagglutinin loci, serotyping and agglutinating activity of Porphyromonas gingivalis isolates

Restriction fragment length polymorphisms (RFLPs) of two hemagglutinin loci were analyzed in 36 Porphyromonas gingivalis isolates from human and monkey origins using portions of hagA and hagB as probes. The P. gingivalis strains were differentiated into 9 RFLP groups based on the heterogeneity of the hagA locus and 10 different groups based on hybridization with hagB. Homology to hagA was detected in all human derived and all but three monkey derived strains. All P. gingivalis isolates exhibited DNA homologous to hagB. Multiple alleles of the hemagglutinin genes were detected for most P. gingivalis strains. No DNA homologous to either hemagglutinin gene could be detected in 6 other bacterial species tested. Serotyping and hemagglutination titers of each P. gingivalis isolate were obtained in an attempt to establish a correlation between these pheno-typic parameters and RFLP group. Although no correlations were found with these parameters, a correlation between RFLP group and invasiveness in the mouse abscess model was noted.

Preliminary characterisation of antigens recognised by monoclonal antibodies raised to Porphyromonas gingivalis and by sera from patients with periodontitis

A panel of 15 monoclonal antibodies (MAbs) was raised to Porphyromonas gingivalis and used to characterise the antigens which they recognise by ELISA, immunofluorescence (IF), Western blotting and patient serum inhibition studies. All the MAbs were specific for P. gingivalis and did not recognise 24 other species. Eight MAbs gave bright ring-like staining patterns against the majority of serotypes of P. gingivalis tested by IF. The antibodies could be grouped into 5 different antigen recognition profiles on Western blotting, and ELISA indicated that 8 of them bound to a capsular extract. Five antibodies bound to antigenic determinants recognised by sera from patients with periodonitis and 4 of these (1A1, 2B/H9, 3B1, 7D5) bound to a P. gingivalis 47kDa protease preparation on Western blotting. These antibodies are potentially useful for the purification and characterisation of biologically active components of P. gingivalis that are recognised by sera from patients with periodontitis.

Host-related genotypic heterogeneity of Porphyromonas gingivalis strains in the beagle dog

The present investigation explored the genotypic heterogeneity of Porphyromonas gingivalis using restriction endonuclease analysis and ribotyping of 64 P. gingivalis isolates, recovered from the periodontal pockets of 3 beagle dogs, 2 of which were reared together. The isolates originated from both healthy and periodontal disease affected sites and thereby enabled the study of bacterial genotype with respect to (i) individual host, (ii) ecological niche (site within host) and (iii) level of periodontal health. Whole genomic DNA was extracted from each isolate and digested by the restriction endonuclease KpnI. Digestion fragments were separated by electrophoresis and transferred onto nylon membranes. The blots were hybridized with a digoxigenin-labeled 16S rDNA probe, and hybridization bands were detected using an anti-digoxigenin antibody conjugated with alkaline phosphatase and enhanced chemiluminescence. Fourteen genomic fingerprints and 13 ribotypes were observed among the 64 isolates. As many as 8 distinct fingerprints were detected within a single host and up to 4 fingerprints within a single periodontal pocket. The dogs reared together shared 2 common clonal types but also exhibited clonal types unique to each dog. No clear association between clonal type and periodontal health status could be made. The results revealed an extensive intra-host genotypic heterogeneity of P. gingivalis strains in the beagle dog and indicated that ribotyping was a sensitive method for differentiating clonal types within species.

Detection and strain identification of Actinobacillus actinomycetemcomitans by nested PCR

By using PCR, Actinobacillus actinomycetemcomitans strains were identified directly from plaque samples without the need to isolate or culture bacteria. DNA fragments were generated by a nested, two-step PCR amplification of the ribosomal spacer region between the 16S and 23S rRNA genes. For the first amplification, primers homologous to sequences common to all bacterial species were used. This was followed by a second amplification with primers specific to A. actinomycetemcomitans. The ribosomal DNA spacer region was amplified from as few as 10 bacterial cells within a total population of 10(8) cells (0.00001%), and cross-reactivity between species was not observed. DNA fragments specific for Porphyromonas gingivalis were generated from the same samples by using a P. gingivalis-specific primer, and equivalent sensitivity and specificity were observed. A. actinomycetemcomitans was detected in 60% and P. gingivalis was detected in 79% of 52 subjects tested. Sequence analysis of the spacer region DNA fragment for A. actinomycetemcomitans gave precise strain identification, producing unique sequences for seven reference strains and identification of nine plaque-derived isolates. A phylogenetic tree based on quantitative sequence relationships was constructed. Two-step PCR amplification directly from plaque samples combined with sequence analysis of the ribosomal DNA spacer region provides a sensitive assay for detection and strain identification of multiple species directly from a single plaque sample. This simplified approach provides a practical method for large-scale studies on the transmission and pathogenicity of periodontitis-associated bacteria.

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

Genetic analysis of Porphyromonas gingivalis strains may distinguish between virulent and nonvirulent strains and also may be used to trace individual strains in epidemiological studies. The present study examined the utility of the arbitrarily primed polymerase chain reaction for genotypic fingerprinting of P. gingivalis. DNA was extracted according to conventional methods. Ten-base oligonucleotide primers with arbitrary sequences were used with the polymerase chain reaction to amplify P. gingivalis genomic DNA. The amplification products were analyzed by agarose gel electrophoresis. The primer GACCGCTTGT grouped 73 P. gingivalis strains into 23 genotypes, including 16 genotypes containing a single strain each. The primer AGGGGTCTTG identified 45 different genotypes, 33 of which contained a single strain. P. gingivalis strains ATCC 33277T and 381 belonged to the same genotype. Likewise, strains W50 and W83 were of the same genetic clone. The present study indicates that the arbitrarily primed polymerase chain reaction represents a valuable and easy method for clonal analysis of P. gingivalis.

K-antigens in Porphyromonas gingivalis are associated with virulence

We investigated antigens in spreading and non-spreading Porphyromonas gingivalis strains. On the basis of differences in virulence in the mouse model, 8 strains were selected for antiserum production in rabbits. Hyperimmune sera were tested by double immunoprecipitation and immunoelectrophoresis. Besides a common antigen, differences in antigenic composition were observed in the thermolabile antigens between all strains tested. Two different heat-stable antigens were found after heating at 120 degrees C. One such antigen was detected after sonication of the pellet fraction of autoclaved P. gingivalis cells. This antigen cross-reacted with 6 of the 8 immune sera. This somatic antigen was almost neutrally charged and sensitive to sodium periodate treatment, suggestive of lipopolysaccharide. A second heat-stable antigen was detected in the supernatant of autoclaved strains of W83, W50, HG184 and A7A1-28. These non-somatic antigens were strain-specific, i.e., no cross-reactivity was found with heterologous hyperimmune sera. An exception was strain W50, which had a non-somatic heat-stable antigen which was recognized by W83 antiserum. These antigens were resistant to DNAse, RNAse and proteinase-K treatment but were degraded by sodium periodate. In immunoelectrophoresis, these antigens appeared to be negatively charged. These properties are characteristics of a K-antigen, which likely represent a thermostable carbohydrate capsule. The presence of K-antigen correlates very well with the serum resistance, the low chemiluminescence, the resistance to phagocytosis and the need for opsonization with specific antibodies for complement-mediated killing of virulent P. gingivalis strains.(ABSTRACT TRUNCATED AT 250 WORDS)

Classification and typing methods of black-pigmented gram-negative anaerobes

Until recently, black-pigmented Gram-negative anaerobes were classified as 'black-pigmented Bacteroides'. At present, 11 distinct species are recognized in this group. Because of major differences with Bacteroides fragilis, the type species of the genus Bacteroides, new genera have been proposed: Porphyromonas for three asaccharolytic species, and Prevotella for the saccharolytic species. Typing methods have been developed for some species of black-pigmented Gram-negative anaerobes. These include biotyping and serotyping, but relatively few types can be distinguished with these methods. Recently, DNA restriction endonuclease analysis has been used for typing of P. gingivalis, Pr. intermedia and P. endodontalis strains. Great heterogeneity was observed within all three species. This typing method can be useful for epidemiological studies.

Genetic structure of populations of Porphyromonas gingivalis associated with periodontitis and other oral infections

One hundred isolates of the oral pathogenic bacterium Porphyromonas gingivalis were genetically characterized by determining the electrophoretic mobilities of 16 metabolic enzymes and the presence or absence of catalase activity. A total of 78 distinct electrophoretic types (ETs), representing multilocus genotypes, were identified, and cluster analysis placed them in three major phylogenetic divisions. Division I (71 ETs) included all 88 human isolates examined, most of which had been recovered from patients with periodontitis, together with 4 monkey isolates. The strains in division II (four ETs) and division III (three ETs) are strongly differentiated from those in division I and apparently represent two previously unclassified (cryptic) species. The mean genetic diversity per enzyme locus among the 92 isolates of division I (P. gingivalis, strict sense) was 0.321, and the strains were distributed among 14 phylogenetic clusters and single-ET lineages. The population structure is basically clonal, with some clonal genotypes being widespread, and even global, in distribution. There was no evidence of association between specific genetic lineages or clusters of ETs and the type of disease (periodontitis or root canal infections), invasive potential, serogroup, or fimbrial restriction fragment length polymorphism group. The finding that dental patients are infected by strains of a wide variety of chromosomal genotypes suggests that interstrain variation in pathogenicity is small. On the basis of the observed genetic structure of natural populations of P. gingivalis, we hypothesize that the role of this microorganism in the pathogenesis of periodontitis and other dental infections is largely opportunistic.