Purification and biochemical properties of a bacteriocin from Actinobacillus actinomycetemcomitans

Production of antagonistic substance by Eikenella corrodens isolated from the oral cavity of human beings with and without periodontal disease

AIMS

Antagonistic abilities may confer ecological advantages for micro-organisms in competitive ecosystems. However, reports regarding this phenomenon in Eikenella corrodens are not available.

METHODS AND RESULTS

Nineteen E. corrodens strains, isolated from the oral cavity of human beings without periodontal disease (n = 5) and with aggressive (n = 9) and chronic (n = 5) periodontitis, as well as a reference strain (E. corrodens ATCC23834), were evaluated for antagonistic activity. The following indicators were used: Porphyromonas gingivalis FDC381, Prevotella intermedia ATCC25611, Actinomyces israelii ATCC12102, Eubacterium lentum ATCC25559, Peptostreptococcus anaerobius ATCC27337, Actinobacillus actinomycetemcomitans FDCY4, Fusobacterium nucleatum ATCC10953, Streptococcus sanguinis ATCC10557, Streptococcus uberis ATCC9927, Streptococcus mutans IM/UFRJ, Staphylococcus aureus ATCC33591 and Candida albicans ATCC18804. All the strains showed antagonism against at least one of the indicator strains. This phenomenon was more frequently observed for strains isolated from patients with chronic periodontitis (36.4%), than those from healthy subjects (20.6%) and those with aggressive periodontitis (10.8%).

CONCLUSIONS

The heterogeneous antagonistic spectrum exhibited by E. corrodens isolates suggests their ability to produce more than one antagonistic substance, whose ecological relevance is yet to be demonstrated.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first description of antagonistic compound production by E. corrodens and its relationships with the clinical status of the patients.

Purification and partial characterization of a bacteriocin produced by Eikenella corrodens

AIMS

The purpose of this study was to purify and characterize a bacteriocin produced by Eikenella corrodens A32E2.

METHODS AND RESULTS

Peptostreptococcus anaerobius ATCC27337 was used as indicator strain in antagonistic assays for bacteriocin-producing E. corrodens A32E2. Protein extraction was influenced by pH and buffer composition. The protein was active in the pH range 6-8. Inhibitory activity was lost by both heating and treatment with proteolytic enzymes and decreased with organic solvents. The substance is rather unstable but maintains 100% of its activity after being exposed to acetone and when stored at -70 degrees C. The antagonistic substance was first precipitated by ammonium sulfate and further partially purified by Mono-Q FPLC and C-18 HPLC. Mass spectrometry analysis showed that the molecular mass was 23 625 Da, and the sequence obtained for the N-terminus was: Met-Asn-Phe-Asp-Glu-Lys-Val-Gly-Lys-Val-X-Phe-Lys-Val-Gly-Asp.

CONCLUSIONS

The evidence presented in this study supports the idea that an antagonistic substance produced by E. corrodens A32E2 isolated from a periodontal diseased site is a novel bacteriocin, which we designate corrodecin.

SIGNIFICANCE AND IMPACT OF THE STUDY

We anticipated that corrodecin might play an important role at the periodontal site. This compound could also be attractive in biotechnological applications as an interesting tool for oral ecosystem control.

Characterization of a bacteriocin produced by Prevotella nigrescens ATCC 25261

AIMS

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

METHODS AND RESULTS

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

CONCLUSION

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

SIGNIFICANCE AND IMPACT OF THE STUDY

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

Antiproliferative activity of Actinobacillus (Haemophilus) actinomycetemcomitans and Fusobacterium nucleatum in peripheral blood mononuclear cells

Several studies indicate Actinobacillus (Haemophilus) actinomycetemcomitans and Fusobacterium nucleatum as etiologic agents of periodontal disease. Immunosuppressive factors produced by microorganisms probably contribute to the initiation and evolution of this disease. This study evaluated the antiproliferative activity of ammonium precipitate fractions of A. (H.) actinomycetemcomitans and F. nucleatum isolates from humans and marmosets both with and without periodontal disease. All A. (H.) actinomycetemcomitans and most F. nucleatum strains inhibited PBMC proliferation in a dose-dependent manner. The degree of cell proliferative inhibition of each bacterial species differed among the strains and was independent of host clinical status. The in vitro inhibition of stimulated lymphocyte proliferation induced by different A. (H.) actinomycetemcomitans and F. nucleatum isolates demonstrated the importance of this phenomenon in bacterial virulence, playing a possible suppressor role in host defense mechanisms in vivo. Moreover, our findings pointed out a marked difference between A. (H.) actinomycetemcomitans and F. nucleatum cytoplasmic extracts in their antiproliferative activity, regarding the antigen concentration required for maximum inhibition and their vulnerability to heating and proteolytic treatment.

Influence of abiotic factors on the bacteriocinogenic activity of Actinobacillus actinomycetemcomitans

We evaluated the influence of abiotic factors on antagonistic activity of Actinobacillus actinomycetemcomitans strains isolated from periodontal pockets and two reference strains (ATCC 29523 and FDC Y4). Antagonistic assays were performed by the overlayer method on tryptic soy agar (TSA), brain heart infusion agar, thioglycollate agar and brucella agar, added with yeast extract and supplemented (S) or not with L-cystine and sodium bicarbonate. Iso-, auto-, and heteroantagonism against a wide range of indicator strains were assayed. The influence of incubation atmosphere (anaerobic chamber, anaerobic and candle jars) and pH (5.0 to 11.0) was also evaluated. Autoantagonism was not observed. TSA-S was shown to be the most adequate medium for antagonistic activity expression. The widest spectrum of heteroantagonistic activity was also observed on TSA-S. The incubation atmosphere affected only the isoantagonistic activity expression. Only at pH 8.0 did A. actinomycetemcomitans express bacteriocinogenic activity. The lack of standardized methodology to detect antagonistic activity can lead to discrepant results and can make data difficult to be compared. This study provides information on abiotic factors that influence bacteriocinogenic activity expression and suggests adequate culture conditions for testing A. actinomycetemcomitans bacteriocin production, contributing to the establishment of a reproducible and reliable methodology.

Bacteriocin production by Actinobacillus actinomycetemcomitans isolated from the oral cavity of humans with periodontal disease, periodontally healthy subjects and marmosets

The ability of Actinobacillus actinomycetemcomitans to produce bacteriocin has rarely been reported. Antagonistic substance production may confer an important ecological advantage for the producer microorganisms, especially in a competitive ecosystem such as the oral cavity. In the present study, 75 A. actinomycetemcomitans strains isolated from the oral cavity of human patients with periodontal disease, periodontally healthy subjects and marmosets, as well as two reference strains (A. actinomycetemcomitans ATCC 29523 and FDC Y4) were evaluated for auto-, iso-, and heteroantagonistic activity. Fifty-one (68.00%) strains exhibited antagonistic activity; heteroantagonism was observed more often than isoantagonism. Isolated strains antagonized 17 different species of gram-positive and gram-negative bacteria from the oral and nonoral microbiota. Sensitivity to heat and to proteolytic enzymes constituted strong evidence that the antagonistic substance has a proteic nature. Taken together, our data enabled us to confirm that the antagonistic substance detected was a bacteriocin. The wide spectrum of activity indicates the possibility that more than one antagonistic substance is produced and that these substances play an important role in the ecological balance of the oral ecosystem.

Virulence factors of Actinobacillus actinomycetemcomitans

A. actinomycetemcomitans has clearly adapted well to its environs; its armamentarium of virulence factors (Table 2) ensures its survival in the oral cavity and enables it to promote disease. Factors that promote A. actinomycetemcomitans colonization and persistence in the oral cavity include adhesins, bacteriocins, invasins and antibiotic resistance. It can interact with and adhere to all components of the oral cavity (the tooth surface, other oral bacteria, epithelial cells or the extracellular matrix). The adherence is mediated by a number of distinct adhesins that are elements of the cell surface (outer membrane proteins, vesicles, fimbriae or amorphous material). A. actinomycetemcomitans enhances its chance of colonization by producing actinobacillin, an antibiotic that is active against both streptococci and Actinomyces, primary colonizers of the tooth surface. The fact that A. actinomycetemcomitans resistance to tetracyclines, a drug often used in the treatment of periodontal disease, is on the rise is an added weapon. Periodontal pathogens or their pathogenic products must be able to pass through the epithelial cell barrier in order to reach and cause destruction to underlying tissues (the gingiva, cementum, periodontal ligament and alveolar bone). A. actinomycetemcomitans is able to elicit its own uptake into epithelial cells and its spread to adjacent cells by usurping normal epithelial cell function. A. actinomycetemcomitans may utilize these remarkable mechanisms for host cell infection and migration to deeper tissues. A. actinomycetemcomitans also orchestrates its own survival by elaborating factors that interfere with the host's defense system (such as factors that kill phagocytes and impair lymphocyte activity, inhibit phagocytosis and phagocyte chemotaxis or interfere with antibody production). Once the organisms are firmly established in the gingiva, the host responds to the bacterial onslaught, especially to the bacterial lipopolysaccharide, by a marked and continual inflammatory response, which results in the destruction of the periodontal tissues. A. actinomycetemcomitans has at least three individual factors that cause bone resorption (lipopolysaccharide, proteolysis-sensitive factor and GroEL), as well as a number of activities (collagenase, fibroblast cytotoxin, etc.) that elicit detrimental effects on connective tissue and the extracellular matrix. It is of considerable interest to know that A. actinomycetemcomitans possesses so many virulence factors but unfortunate that only a few have been extensively studied. If we hope to understand and eradicate this pathogen, it is critical that in-depth investigations into the biochemistry, genetic expression, regulation and mechanisms of action of these factors be initiated.

Bacteriocin production by Fusobacterium isolates recovered from the oral cavity of human subjects with and without periodontal disease and of marmosets

Bacteriocin production has been studied in very few anaerobic bacteria, and no report is available for Fusobacterium species. In the present study a total of 167 Fusobacterium isolates were tested for bacteriocin production: 70 isolates were obtained from the oral cavity of patients with periodontal disease, 47 were recovered from healthy oral sites of human subjects and 50 from the oral cavity of Callithrix penicillata. Autoantagonism and isoantagonism were observed when the bacteriocin-producing isolates were tested against themselves. Heteroantagonism was detected by testing the Fusobacterium isolates against 14 reference strains and 2 strains of Actinobacillus actinomycetemcomitans from our laboratory collection. The auto-, iso- and heteroantagonism phenomena observed in this comparative study suggest a possible ecological role for this (these) antagonistic substance(s) in the oral environment.

Models of invasion of enteric and periodontal pathogens into epithelial cells: a comparative analysis

Bacterial invasion of epithelial cells is associated with the initiation of infection by many bacteria. To carry out this action, bacteria have developed remarkable processes and mechanisms that co-opt host cell function and stimulate their own uptake and adaptation to the environment of the host cell. Two general types of invasion processes have been observed. In one type, the pathogens (e.g., Salmonella and Yersinia spp.) remain in the vacuole in which they are internalized and replicate within the vacuole. In the other type, the organism (e.g., Actinobacillus actinomycetemcomitans, Shigella flexneri, and Listeria monocytogenes) is able to escape from the vacuole, replicate in the host cell cytoplasm, and spread to adjacent host cells. The much-studied enteropathogenic bacteria usurp primarily host cell microfilaments for entry. Those organisms which can escape from the vacuole do so by means of hemolytic factors and C type phospholipases. The cell-to-cell spread of these organisms is mediated by microfilaments. The investigation of invasion by periodontopathogens is in its infancy in comparison with that of the enteric pathogens. However, studies to date on two invasive periodontopathogens. A actinomycetemcomitans and Porphyromonas (Bacteroides) gingivalis, reveal that these bacteria have developed invasion strategies and mechanisms similar to those of the enteropathogens. Entry of A. actinomycetemcomitans is mediated by microfilaments, whereas entry of P. gingivalis is mediated by both microfilaments and microtubules. A. actinomycetemcomitans, like Shigella and Listeria, can escape from the vacuole and spread to adjacent cells. However, the spread of A. actinomycetemcomitans is linked to host cell microtubules, not microfilaments. The paradigms presented establish that bacteria which cause chronic infections, such as periodontitis, and bacteria which cause acute diseases, such as dysentery, have developed similar invasion strategies.

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

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

Purification of a fibroblast-inhibitory factor from Actinobacillus actinomycetemcomitans Y4

A factor showing inhibitory activity against human gingival fibroblasts was extracted from the cytosol fraction of Actinobacillus actinomycetemocimitans Y4. The activity markedly inhibited the proliferation of human gingival fibroblasts, but had no effect on cell viability or gross morphology. No such activity was found in cytosol fractions from either Porphyromonas gingivalis 381 or Escherichia coli HB101. The extract from A. actinomycetemocomitans Y4 was then purified by anion-exchange chromatography, hydroxyapatite chromatography and gel-filtration chromatography to give a single band on SDS-PAGE with an apparent molecular mass of 65 kDa. The purification ratio was 183-fold with a recovery rate of 5% compared with the crude extract (starting material) when the activity was assessed by direct cell counts.

Longitudinal monitoring for disease progression of localized juvenile periodontitis

The present study was performed to investigate the factors associated with disease progression in localized juvenile periodontitis (LJP) patients by longitudinal monitoring of microbiological changes. Following a 9-month period, 9 LJP patients were divided into 2 groups based upon attachment loss, progressing and non-progressing. Both groups received scaling, root planing, and modified Widman flaps. Clinical and microbiological data were obtained at baseline, following the observation period, and at 6 and 12 months post-treatment. At 6 and 12 months post-treatment significantly more cocci were persistent in the non-progressing group than in the progressing group. Actinobacillus actinomycetemcomitans was also more frequently isolated in the progressing group than in the non-progressing group initially and following the 9-month observation period. Also after treatment, A. actinomycetemcomitans recolonized earlier in the progressing group than in the non-progressing group. These studies suggest that A. actinomycetemcomitans may play a role in disease progression in LJP; however, they do not eliminate the possibility that other organisms may also play a role, since A. actinomycetemcomitans was not detected in all of the patients in whom disease progressed.

Microbiological testing in the diagnosis of periodontal disease

The oral microbiota plays a primary role in the initiation and progression of the most common forms of periodontal disease. Because of the multiplicity of factors that control the establishment and long-term evolution of the oral microbiota, a great deal of heterogeneity exists in the composition of the periodontal microbiota among individual subjects. Despite these individual differences and the complex interactions between bacteria and the host and among bacteria, an association has been demonstrated between certain species and various forms of periodontal disease. However, the predictive value of either positive or negative tests for selected bacterial species has not proved to be high enough for routine use in clinical practice. Nevertheless, bacteriological tests have been of value in the management of patients with juvenile periodontitis and refractory forms of periodontal disease. The increasing availability of diagnostic laboratory services and diagnostic kits for office use will make it easier for the practitioner to select appropriate antimicrobial treatments and monitor patients undergoing antimicrobial therapy.

Bacteriocin-like activity of Bacteroides fragilis group isolated from marmosets

The ability of strains of the B. fragilis group, isolated from the oral cavity and intestine of marmosets, to produce bacteriorin-like substances in solid medium, in terms of auto-, iso- and heteroantagonism, was evaluated. Antagonistic activity was exhibited by 52% of the intestinal strains, 3 of which showed autoantagonistic activity. Three out of 9 oral strains isolated, tested against themselves, showed simultaneous isoantagonism to 4 indicator strains; but not autoantagonism. The same 9 oral strains, when tested against 16 reference strains, revealed interspecific activity only against 2 Gram-positive microorganisms. Higher activity, evaluated by the size of the inhibition halo, was observed in BHI-S agar, and greatest inhibition was obtained after 72 h of incubation.

Isolation and purification of bacteriocin from Prevotella intermedia (Bacteroides intermedius)

Thirty-three out of 46 strains of Prevotella intermedia (Bacteroides intermedius) isolated from gingival deposits of patients with adult periodontitis possessed the ability to inhibit growth of P. intermedia strain ATCC 25611, and 6 of the 33 showed strong inhibitory activity. Thirteen isolates did not have the ability to inhibit the growth of P. intermedia strain ATCC 25611. An inhibition factor from one of the isolates, P. intermedia TH14 which had strong inhibition, was purified and characterized. Bacteriocin TH14 activity was effective against only P. intermedia ATCC 25611 and Fusobacterium nucleatum, but not against other crevicular bacteria, including P. intermedia ATCC 33563, Porphyromonas gingivalis (Bacteroides gingivalis), Capnocytophaga sputigena and Actinobacillus actinomycetemcomitans. Streptococci, actinomyces, and veillonellas were not inhibited by bacteriocin TH14. Bacteriocin TH14 was heat sensitive, proteinaceous with molecular weight of 1,700 daltons and inhibited the growth of strain ATCC 25611 in 15 minutes. The growth inhibition of P. intermedia ATCC 25611 by bacteriocin TH14 was found to be due to the bactericidal activity of the bacteriocin.

Effect of Actinobacillus actinomycetemcomitans, Wolinella recta and Bacteroides gingivalis on the viability of retinoic acid-induced and dimethyl sulfoxide-induced HL-60 cells

We studied the interactions between viable and heat-killed, opsonized and unopsonized periodontopathic bacteria with both uninduced and induced HL-60 promyelocytic leukemia cells. The cells were induced to differentiate into granulocyte-like cells by incubation with retinoic acid (RA) or dimethyl sulfoxide (DMSO). When unopsonized, Wolinella recta ATCC 33228 significantly suppressed the net proliferation of uninduced HL-60 cells, Actinobacillus actinomycetemcomitans strain Y4 was markedly lethal to the cells, and Bacteroides gingivalis ATCC 33277 had no effect. Unopsonized and opsonized A. actinomycetemcomitans and W. recta had equally potent lethal effects on induced HL-60 cells. Unopsonized B. gingivalis was not lethal to the induced cells in the dose used (100 bacteria/HL-60 cell), but opsonized B. gingivalis was lethal, especially in the first 24 h. The killing effects of A. actinomycetemcomitans and W. recta were largely eliminated if they were heated (56 degrees C, 30 min) before being added to the induced HL-60 cells. RA-induced HL-60 cells were more sensitive to the lethal effects of A. actinomycetemcomitans and W. recta than were DMSO-induced cells. The results suggest that the HL-60 cell line may be a useful model for studying granulocyte-bacteria interactions.

A bacteriocin of Actinobacillus actinomycetemcomitans

An inhibitory factor from Actinobacillus actinomycetemcomitans Y4 was isolated, and its properties indicated that it was a bacteriocin (actinobacillicin). The bacteriocin was active against Streptococcus sanguis strains, Streptococcus uberis (FDC1), and Actinomyces viscosus T14 as well as other strains of A. actinomycetemcomitans, but not against other crevicular bacteria, including other streptococci and actinomycetes. The activity of this bacteriocin was inhibited by pronase, trypsin, and heat (45 min at 56 degrees C) but not by DNase, RNase, phospholipase, exposure to UV light, or low pH (1.0 to 6.5). Although actinobacillicin markedly inhibited glycolysis in S. sanguis, the primary mechanism of its bactericidal action appears to be alterations in cell permeability, with the resultant leakage of RNA, DNA, and other essential intracellular macromolecules. These findings provide an ecologic explanation for the reciprocal growth relationship between A. actinomycetemcomitans and S. sanguis/Actinomyces viscosus observed in localized juvenile periodontitis.