Characterization of hemolytic bacteria in subgingival plaque

Preliminary safety assessment of a new Bacteroides fragilis isolate

The novel commensal strain of Bacteroides fragilis HCK-B3 isolated from a healthy Chinese donor was discovered beneficial effects of attenuating lipopolysaccharides-induced inflammation. In order to contribute to the development of natural next-generation probiotic strains, the safety assessment was carried out with in vitro investigations of its morphology, potential virulence genes and antimicrobial resistance, and an in vivo acute toxicity study based on both healthy and immunosuppressed mice by cyclophosphamide injection. Consequently, the potential virulence genes in the genome of B. fragilis HCK-B3 have yet been identified as toxicity-associated. The absence of plasmids prevents the possibility of transferring antibiotic resistance features to other intestinal commensals. No intracorporal pathogenic properties were observed according to the body weight, hematological and liver parameters, cytokine secretions and tissue integrity. In addition, B. fragilis HCK-B3 performed alleviations on part of the side effects caused by the cyclophosphamide treatment. Thus, the novel strain of B. fragilis HCK-B3 was confirmed to be non-toxigenic and did not display adverse effects in both healthy and immune-deficient mice at a routinely applicable dose.

Serum and salivary ferritin and Hepcidin levels in patients with chronic periodontitis and type 2 diabetes mellitus

BACKGROUND

Iron disorder and abnormal expression of hepcidin play important roles in many diseases, but it is still unclear in chronic periodontitis (CP) and type 2 diabetes mellitus (T2DM). We aimed to assess ferritin and hepcidin levels in serum and saliva of CP patients with or without T2DM.

METHODS

Serum and unstimulated whole saliva samples were collected from 88 participants, who were categorized into 4 groups based on the presence or absence of CP or T2DM. Demographics and general health parameters were recorded. Full-mouth clinical periodontal parameters including probing pocket depth, clinical attachment loss, bleeding index, and plaque index were recorded. Chemiluminescence microparticle immunoassay and enzyme-linked immunosorbent assay were used to detect ferritin and hepcidin concentrations, respectively, in serum and saliva.

RESULTS

Serum ferritin and hepcidin levels in the CP and CP with T2DM groups were higher than in the control group (P < 0.05). Serum hepcidin and serum ferritin are linear correlated (P < 0.001). Serum hepcidin/ferritin values in the CP with T2DM group were significantly lower than those in the T2DM and control groups. Moreover, salivary ferritin levels in the CP and T2DM groups were higher than those in the control group (P < 0.05). There was positively correlation between salivary ferritin and serum ferritin (P = 0.017). Hepcidin concentrations were relatively low in saliva.

CONCLUSIONS

These results suggest that iron overload and hepcidin inadequacy existed in CP with T2DM patients. Salivary ferritin might provide a reference for body iron load.

TRIAL REGISTRATION

ChiCTR-ROC-17012780.

Association of clinical parameters with periodontal bacterial haemolytic activity

AIMS

To determine whether haemolytic activity of subgingival bacteria is associated with periodontitis clinical parameters and to identify which bacteria produce the haemolysins.

MATERIALS AND METHODS

Subgingival plaque samples from 22 untreated chronic periodontitis patients were investigated by culture and identified with matrix assisted laser desorption/ionisation time-of-flight mass spectrometry.

RESULTS

Total aerobic and anaerobic bacterial viable counts, percentage distribution of α- and β-haemolytic bacteria were significantly elevated in diseased sites in relation to healthy sites (p < 0.001). Periodontal pathogens were more frequently detected at diseased sites: Porphyromonas gingivalis, Tannerella forsythia, Treponema sp., Prevotella sp., Parvimonas micra, Fusobacterium sp., Campylobacter sp., Capnocytophaga sp., and Selenomonas sp. Haemolytic unidentifiable species and Gram-positive anaerobes such as Slackia exigua, Solobacterium moorei, and Bulledia extructa were also more frequently detected at diseased sites. In diseased sites, the presence of different haemolytic characteristics was more strongly correlated with clinical measures of disease than the mere absence or presence of specific species. The strongest correlation with probing pocket depth was observed for overall β-haemolytic toxicity (r = 0.73, p < 0.001).

CONCLUSION

A strong association was observed between subgingival bacterial haemolytic activity and clinical parameters in patients with chronic periodontitis. Further investigations are warranted to delineate the role of haemolysins in the pathogenesis of periodontitis.

The release of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from human erythrocyte membranes lysed by hemolysin of Prevotella oris

We found that a 38-kDa protein was released from erythrocyte membranes lysed by hemolysin of Prevotella oris, although hypotonic hemolysis did not show such a phenomenon. The 38-kDa protein was identified as glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by N-terminal amino acid sequencing. This study discusses the relationship between GAPDH and hemolysis.

Genomic recombination through plasmid-encoded recombinase enhances hemolytic activity and adherence to epithelial cells in the periodontopathogenic bacterium Eikenella corrodens

The periodontopathogenic bacterium Eikenella corrodens has an N-acetyl-D-galactosamine (GalNAc)-specific lectin, that contributes significantly to the pathogenicity of the bacterium. Recently, we reported that plasmid-mediated genomic recombination enhances the activity of this lectin. In this study, we investigated the effects of genomic recombination on certain virulence factors. Introduction of the recombinase gene resulted in hemolysis and significantly increased bacterial adhesion to epithelial cells. It was suggested that the enhanced adhesion was attributable to increased lectin activity due to genomic recombination, because it was inhibited by the addition of GalNAc. In contrast, invasion of the epithelial cells was remarkably reduced by genomic recombination. Although we assumed that this decrease in invasion resulted from a loss of type-IV pili, the phase variant did not show any decrease in invasion activity. This suggests that type-IV pili do not contribute to the invasive ability of E. corrodens. Our results suggest that genomic recombination enhances the pathogenicity of E. corrodens.

Ribotyping of bacteria from root canal and blood of patients receiving endodontic therapy

DNA restriction patterns and corresponding ribotypes of 26 bacterial isolates (Propionibacterium acnes, Peptostreptococcus prevotii, Fusobacterium nucleatum, Prevotella intermedia, Prevotella nigrescens, Actinomyces israelii, Streptococcus intermedius, and Streptococcus sanguis) recovered from patients with infected root canals and their peripheral blood, collected during and after endodontic therapy, were examined. Eleven additional reference strains including type strains were also examined. Purified DNA was digested with BglI,EcoRI, and HindIII. Hybridization was carried out with a digoxigenin-labeled cDNA probe obtained by reverse transcription of Escherichia coli 16S + 23S rRNA. Ribotypes of the bacteria recovered from root canal and blood showed identical characteristics within the patients, and differed between the patients. The results were confirmed when the similarity coefficient (S(AB)) of the ribotypes from the isolates were assessed by the Dendron computer-assisted system. These results suggested that the bacteria isolated from the blood originated from the root canal.

Characterization of hemoglobin binding to Actinobacillus actinomycetemcomitans

In this study, binding of hemoglobin to Actinobacillus actinomycetemcomitans was characterized. The ability of A. actinomycetemcomitans to utilize hemoglobin as an iron source was examined by growth studies. Although the bacterial growth was limited almost completely by adding 400 microM 2, 2'-dipyridyl to culture medium, addition of hemoglobin recovered the growth in a dose-dependent manner, revealing that hemoglobin can be utilized effectively as an iron source by A. actinomycetemcomitans. Binding of A. actinomycetemcomitans to hemoglobin was examined by dot-blot assay. Optimal hemoglobin-binding activity occurred at pH 6 and activity under acidic conditions was found to be higher than that under alkaline conditions. Hemoglobin-binding activity was higher under anaerobic conditions than under aerobic conditions, and iron restriction in culture medium decreased the activity by 55%. Heat and trypsin treatments of the bacterial components reduced the activity by 28% and 60%, respectively. Globin inhibited the activity by 49%, while transferrin, lactoferrin and tested amino acids and sugars had little or no inhibitory effects. These results indicate that proteinaceous components of the bacterial cells may be involved in hemoglobin binding and that globin moiety of the hemoglobin molecule may be essential for the binding. In order to identify hemoglobin-binding proteins, the bacterial cell components extracted with n-octyl-beta-D-thioglucoside were subjected to SDS-PAGE and transferred to a nitrocellulose membrane. The membrane was incubated with hemoglobin and bound hemoglobin was detected with anti-hemoglobin antibodies. About 40- and 65-kDa proteins from A. actinomycetemcomitans reacted with hemoglobin. The 65-kDa protein was detected despite the iron concentration in culture medium, whereas expression of the 40-kDa protein was enhanced only when the organism was grown in iron-restricted culture medium. From these results, it is suggested that 40- and 65-kDa proteins of A. actinomycetemcomitans may be involved in hemoglobin binding.

Properties of hemagglutination by Prevotella melaninogenica

Although Prevotella melaninogenica belongs to the commensal oral microbiota, some strains possess putative virulence factors. For example, we have previously described fimbriated, hemagglutinating strains of P. melaninogenica, isolated from patients with periodontal disease. The aim of this investigation was to compare some chemical and physical properties of hemagglutination (HA) of P. melaninogenica with those of other pigmented gram-negative anaerobes. HA of 13 P. melaninogenica strains proved to be considerably weaker than that of the major periodontal pathogen, Porphyromonas gingivalis. Vigorous shaking reduced HA of shaken cells but the shaken supernatant had the same hemagglutinating activity as non-shaken cells. The hemagglutinating agent on P. melaninogenica seemed to be a protein, which can be separated from the cell and binds to lactose-, galactose-, and raffinose-containing carbohydrates on the erythrocytes. Adherence to epithelial cells did not differ significantly between the hemagglutinating and non-hemagglutinating strains of P. melaninogenica. Although P. melaninogenica is able to agglutinate erythrocytes, this potential virulence factor is of a considerably lower magnitude than that of major periodontal pathogens.

Isolation and characterization of hemolysin activated by reductant from Prevotella intermedia

The hemolysin from Prevotella intermedia was partially purified from culture supernatant and then characterized. The hemolysin produced a clear beta-hemolytic zone on a blood agar plate. Hemolytic activity was 2.5-fold greater in culture supernatant compared to that cell-associated. The isolation and purification procedure involved ammonium sulfate and polyethylene glycol precipitations and ion-exchange chromatographies on DEAE-Sephacel and CM-Sepharose. The activity of this hemolysin was stimulated by reductants such as cysteine, dithiothreitol, glutathione etc., and was lost upon oxidation. Trypsin or heat treatment resulted in complete inhibition of hemolytic activity. Ca(2+), Mg(2+) and EDTA did not affect the activity. The optimal pH of this hemolysin was 7.5.

Two distinct hemolysins in Trichomonas tenax ATCC 30207

An oral protist Trichomonas tenax ATCC 30207 was investigated for the ability to lyse erythrocytes of sheep, rabbits, horses and humans. Five fractions, including intact cells, culture supernatant, culture filtrate, cell debris and lipid-enriched fractions, were prepared from the protozoan cells, and their hemolytic activities were assayed under various conditions. All the samples except culture supernatant had hemolytic activities, which were due to two different kinds of hemolysins. One hemolysin was protein-like and mainly found in cell-free fractions: culture supernatant and culture filtrate. It was heat-labile and inhibited by various cysteine-proteinase inhibitors. The other hemolysin was lipid-like and found in cell-associated fractions: intact cells, cell-debris and lipid-enriched fractions. It was heat-stable, organic solvent-tolerant and unaffected by various proteinase inhibitors and stimulators. These results suggested that T. tenax ATCC 30207 possessed two distinct hemolysins, protein and lipid.

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.

Porphyromonas gingivalis strain variability and periodontitis

To determine if there is variability in virulence among strains of Porphyromonas gingivalis in human periodontitis, their distribution in a group of subjects with clear indicators of periodontitis and in a healthy, age-matched control group was examined. The presence of heteroduplex types of P. gingivalis in the two groups was determined with a PCR-based assay. This assay relied on detection of polymorphisms in the ribosomal internal spacer region (ISR). ISR fragments generated by PCR with P. gingivalis-specific primers were hybridized to fragments from reference strains, and the formation of heteroduplexes from the hybridization of nonidentical sequences was observed by polyacrylamide gel electrophoresis. Characteristic fingerprints from comparison with a panel of reference strains allowed the identification of heteroduplex types in clinical samples. One hundred thirty adults with periodontitis and 181 controls were sampled. With this approach, 11 heteroduplex types of P. gingivalis were detected in the population. Sufficient numbers were available for statistical analysis of six of these types. Heteroduplex type hW83 was found to be very strongly associated with periodontitis (P = 0.0000), and two additional types, h49417 and hHG1691, were also significantly associated with disease. The remaining types, h23A4, h381, and hA7A1, were detected more frequently in subjects with periodontitis than in healthy subjects, but the difference was not significant. These data indicate that virulence in human periodontitis varies among strains of P. gingivalis, and they identify an apparently highly virulent subgroup.

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.

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.

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.

Identification of hemolytic activity in Prevotella intermedia

Hemolysin production was measured in strains of Prevotella intermedia. Zones of beta-hemolysis were detected on agar plates supplemented with either sheep, rabbit or human erythrocytes. A standard tube assay was performed on cell suspensions of the organism to measure hemolytic activity, which was found to be dose dependent, eliminated by heat treatment, and saturable with increasing concentrations of blood. Growth-phase experiments suggested that hemolysin production was increased during logarithmic growth and was reduced during stationary phase. Cell fractionation, performed on several strains of P. intermedia, localized the activity in the outer membrane and in cell vesicles. The biological implication of this study is that P. intermedia, by virtue of its hemolytic activity, is capable of liberating the hemoglobin from erythrocytes, thereby acquiring an essential nutrient, iron, for its metabolism.

Cloning and characterization of a Prevotella melaninogenica hemolysin

Hemolysins have been proven to be important virulence factors in many medically relevant pathogenic organisms. Their production has also been implicated in the etiology of periodontal disease. Hemolytic strain 361B of Prevotella melaninogenica, a putative etiologic agent of periodontal disease, was used in this study. The cloning, sequencing, and characterization of phyA, the structural gene for a P. melaninogenica hemolysin, is described. No extensive sequence homology could be identified between phyA and any reported sequence at either the nucleotide or amino acid level. As predicted from sequence analysis, this gene produces a 39-kDa protein which has hemolytic activity as measured by zymogram analysis. Unlike many Ca2+-dependent bacterial hemolysins, both the cloned and native PhyA proteins were enhanced by the presence of EDTA in a dose-dependent fashion with 40 mM EDTA allowing maximum activity. Ca2+ and Mg2+ were found to be inhibitory. The hemolytic activity also was found to have a dose-dependent endpoint. Through recovery of hemolytic activity from a spent reaction, this endpoint was shown to be the result of end product inhibition. This is the first report describing the cloning and sequencing of a gene from P. melaninogenica.

The role of Actinobacillus actinomycetemcomitans in the pathogenesis of periodontal disease

Periodontal disease consists of a constellation of complex bacterium-host cell interactions. One example of these oral pathogens, Actinobacillus actinomycetemcomitans, has an arsenal of putative virulence determinants that account for its potent periodontopathogenicity. Of these determinants, invasion of host cells and leukocytotoxicity have been studied extensively.

Characterization of Actinobacillus actinomycetemcomitans hemolysin

Twenty out of 33 Actinobacillus actinomycetemcomitans strains formed hemolytic colonies on horse blood agar plates under anaerobic conditions. The hemolytic activity found in A. actinomycetemcomitans strain 137HE was examined. This activity was detected in the late exponential to early stationary phases of growth. Human erythrocytes were the most susceptible, followed by rabbit, sheep, horse and swine red blood cells. The majority of activity was detected in the cell-associated vesicle fraction. Zwitterionic detergent 3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propanesulfonate (CHAPS) extract from whole cells was semipurified by ammonium sulfate precipitation, preparative isoelectric focusing (IEF) and gel-filtration chromatography to yield a major band on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with a molecular mass of 12 kDa. Heating at 80 C for 30 min and treatment with proteinase K or trypsin resulted in complete disappearance of the hemolytic activity. Sulphydryl reagents enhanced activity and small amounts of cholesterol inhibited it. In summary, we demonstrated the presence of hemolysin in A. actinomycetemcomitans, and examined and characterized it.

Isolation and characterization of hemolytic genes from Actinobacillus actinomycetemcomitans

Periodontopathic Actinobacillus actinomyceremcomitans produces hemolysin and other leukotoxins. In the present study, two distinct clones which lysed horse erythrocytes were isolated by screening genomic DNA libraries of A. actinomycetemcomitans ATCC 43718 on blood agar plates. DNA hybridization analysis indicates that there were two distinct hemolytic genes present. Sonicated extracts from both Escherichia coli clones possessed hemolytic activities on horse, sheep and human erythrocytes, but not those of rabbit. Rabbit antiserum to A. actinomycetemcomitans ATCC 43718 whole cells inhibited the hemolytic activities of these clones.

Haemolytic activity of Actinobacillus actinomycetemcomitans strains on different blood types

Haemolytic activity of sixty nine Actinobacillus actinomycetemcomitans strains on different animal and human blood types was examined by using a trypticase soy agar supplemented with yeast extract (0.5%). Blood types used were: rabbit, sheep and human (A, Rh+; A, Rh-; B, Rh+; B, Rh-; O, Rh+; O, Rh-; AB, Rh+; AB, Rh- groups). Plates were inoculated and, incubated in microaerophilic conditions, at 37 degrees C, for 48 h. The haemolytic activity of the tested strains was characterized as alpha-haemolysis. Only two isolates were not haemolytic on all blood types (2.9%), two strains were haemolytic only on human blood (one strain on AB, Rh+ group and another one on A, Rh+ and AB, Rh+ groups). No specificity between haemolysin produced by the tested strains and blood type was observed.