Dichelobacter nodosus: differentiation of virulent and benign strains by gene probe based dot blot hybridisation

Gene probes specific for benign and virulent strains of Dichelobacter nodosus were used in a dot blot hybridisation procedure involving 96 strains of D. nodosus isolated from cases of ovine footrot. The performance of the probes was compared with that of the elastase test. All 27 strains with elastase activity at 7 days and 12 of 25 strains with elastase activity at 14 days reacted with the virulent-specific probe. Twenty-four strains with elastase activity between 21-28 days, and 20 strains with negative elastase activity up to 28 days did not bind with this probe. On the other hand, the benign-specific probe failed to bind with the 27 strains with elastase activity at 7 days, and 13 of the 25 strains with elastase activity at 14 days but reacted with 20 of the 24 strains with elastase activity at 21-28 days, and 19 of the 20 strains with negative elastase activity up to 28 days. The 12 strains with elastase activity at 14 days which were detected by the virulent-specific probe were not those recognised by the benign-specific probe. The use of virulent and benign specific gene probes in combination provides a rapid and precise screening system for differentiation of virulent and higher intermediate footrot from benign and lower intermediate footrot.

Role of suspected periodontopathogens in microbiological monitoring of periodontitis

Periodontal disease is the clinical result of a complex interaction between the host and plaque bacteria. Although a specificity to some degree is found for Actinobacillus actinomycetemcomitans in localized juvenile periodontitis (LJP), it has been difficult to obtain evidence for a specific etiological role of the bacteria associated with periodontal disease in adults. What we see is the net result of host-parasite interactions which in an unpredictable moment accumulate and exceed the threshold of tissue integrity. This hypothesis is concomitant with the view of periodontal disease as a polymicrobial infection, predominantly anaerobic, which occurs commonly in the oral cavity or elsewhere in the body. Some micro-organisms (risk markers) occur more frequently than others and may significantly determine the outcome of this host-parasite interaction. Microbiological sampling and analysis seem to be of limited value in risk assessment; however, they can be used as tools in diagnosis in LJP patients and acute infections, and in treatment decision and therapy control in "refractory" patients. Suspected pathogens (risk markers) are Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and some species of spirochetes, while the roles of Prevotella intermedia, Bacteroidesforsythus, Fusobacterium nucleatum, Campylobacter rectus, and Peptostreptococcus micros are more uncertain. The presence of periodontopathogens as well as enterics, Staphylococcus aureus and Candida especially, should be considered in patients with systemic individual disorders--e.g., diabetes mellitus, neutropenia, agranulocytosis, and AIDS--or with implants.

Empyema due to Bacteroides gracilis: case report and in vitro susceptibilities to eight antimicrobial agents

We describe a patient with empyema due to Bacteroides gracilis and a viridans streptococcus. Therapy with both cefoxitin and imipenem failed, and the patient remained symptomatic even after thoracotomy was performed. Clinical response occurred after initiation of clindamycin therapy. The susceptibilities of the patient's isolate, other clinical strains, and the reference strain were determined by an agar dilution method. The isolates were generally susceptible to all the agents tested; however, some strains were resistant to clindamycin (MIC, 8 micrograms/mL), penicillin G (MIC90, 16 micrograms/mL), and metronidazole (MIC90, 64 micrograms/mL). The B. gracilis isolate from our patient was susceptible to all agents tested, including cefoxitin and imipenem.

Characterization of hemolytic bacteria in subgingival plaque

Three-quarters of the patients with periodontal diseases surveyed in this study had one or more distinct types of hemolytic bacteria in their subgingival plaque. Twelve different species of bacteria were identified, belonging to five genera (Actinomyces, Streptococcus, Staphylococcus, Prevotella, and Actinobacillus). Nine hemolytic isolates, consisting of four Prevotella denticola strains, two Actinomyces naeslundii genospecies 2 strains, and one each of P. melaninogenica, Streptococcus constellatus, and A. naeslundii genospecies 1 strains were characterized. Incorporation of pronase into blood agar medium inhibited hemolysis by all of the isolates, suggesting a proteinaceous component for each of their hemolysins. With one exception, hemolysin production appeared to be regulated by the concentration of environmental iron: exogenous hemin was found to inhibit hemolysin production, and the iron scavenging compound, 2,2'- dipyridyl, was found to promote hemolysin production by all of the strains except for the S. constellatus isolate. Genomic libraries of each of the hemolytic plaque isolates were prepared in Escherichia coli using pBR322. Hemolytic clones were isolated on blood agar medium containing ampicillin at frequencies ranging from 1-6.7 x 10(-4). Extensive restriction mapping revealed regions of homology in the case of clones derived from three P. denticola strains isolated from the same subjects. Two of the P. denticola-derived clones were virtually identical throughout the entrety of their > 5 Kb inserts. The clone derived from the third strain showed good homology to the other two within a 1.3 Kb region, but the flanking DNA showed no homology even though all three P. denticola isolates were shown to be clonally related by ribotyping.(ABSTRACT TRUNCATED AT 250 WORDS)

Porphyromonas gingivalis as putative pathogen in ovine periodontitis

Ovine periodontitis has clinical features similar to early onset periodontitis in man. Porphyromonas gingivalis has been implicated as a putative pathogen in this disease and its role in periodontitis in 107 sheep was investigated. The organism was recovered from most diseased sites at a significant percentage level of the total bacterial count. Antibody assays of 107 animals using an ELISA did not distinguish between diseased (46) and control adult (33) sheep for either P. gingivalis or any of the other putative periodontopathogens tested, but did differentiate adult sheep from healthy lambs (28) for all bacteria except one. It is suggested that sheep rather than human bacterial strains should be used in antibody studies of ovine periodontitis.

Molecular characterization of a genomic region associated with virulence in Dichelobacter nodosus

The major pathogen implicated in footrot, a highly contagious disease of sheep, is the strict anaerobe Dichelobacter nodosus (formerly Bacteroides nodosus). Sequence analysis of a 2,262-bp segment of the D. nodosus genome which is more prevalent in virulent isolates than in other isolates showed the presence of four open reading frames which appeared to have consensus transcriptional and translational start signals. These virulence-associated genes have been designated vapABCD. Two of the three copies of the vap region in the genome of the reference strain D. nodosus A198 were shown to carry all of the vap genes, whereas one copy contained only the vapD gene. The VapD protein was gel purified, shown to contain the predicted amino-terminal sequence, and used to raise rabbit antibodies. Western blots (immunoblots) showed that all of the D. nodosus strains tested that contained the vap region produced the VapD protein. The VapD protein had significant amino acid sequence identity with open reading frame 5 from the cryptic plasmid of Neisseria gonorrhoeae, and the vapBC operon had sequence similarity with the trbH region of the Escherichia coli F plasmid. It is proposed that these gene regions evolved from the integration of a conjugative plasmid from another bacterial species into the D. nodosus chromosome.

Further studies on some physical and biochemical characteristics of asaccharolytic pigmented Bacteroides of feline origin

The ultrastructure of the appendages of 24 strains of asaccharolytic pigmented Bacteroides spp. of cats was studied by transmission electron microscopy. All strains examined by thin section showed abundant fimbriae, outer membrane vesicles and capsules. Negative staining showed fimbriae which varied from long, fine and wavy in Bact. salivosus and cat Group 2 to shorter, less abundant and thicker fimbriae in cat strains of Bact. gingivalis as well as type strains of Porphyromonas gingivalis and P. asaccharolytica. Capsular material was very thick amorphous in human P. gingivalis, cat strains of Bact. gingivalis and in P. assaccharolytica but fine and fibrillary in preparations of Bact. salivosus and cat Group 2 organisms. Wet india ink preparations showed a large capsule although those of Bact. salivosus and Group 2 appeared largest. Five-day Group 2 broth cultures featured a thick ropy growth consistent with a large accumulation of extracellular slime. Enzymatic activities of the 24 strains measured by API ZYM system as well as the conventional biochemical tests showed it was possible to differentiate reliably Bact. salivosus from the other cat strains of asaccharolytic pigmented Bacteroides species and from human P. gingivalis and P. endodontalis by a combination of these tests. These tests suggest that Bact. salivosus is unlikely to belong to the genus Prevotella. Its place within the genus Porphyromonas is still to be determined.

Experimentally induced infection by oral anaerobic microorganisms in a mouse model

A mouse model was developed to study the abscessogenic potential of pure and mixed cultures of oral anaerobes associated with infections of endodontic origin. Maximum subcutaneous lesions were seen on their backs between 3 and 14 d after inoculation. Strains of Fusobacterium nucleatum, Peptostreptococcus anaerobius, and Veillonella parvula were pathogenic in pure culture. A mixed culture of F. nucleatum with either Porphyromonas gingivalis or Prevotella intermedia was significantly more pathogenic than F. nucleatum in pure culture. Histopathological examination of tissue sections from control mice injected with India ink in the medium demonstrated a pathway of particulate migration from the backs of the mice to their abdomen.

Laminin binding to Prevotella intermedia

The interaction of laminin (Lm), a basement membrane protein abundant in the periodontium, with 66 strains of Prevotella intermedia isolated from diseased pockets, was tested in a 125I-labeled protein binding assay. The mean binding value was 28% of the total protein added. The binding significantly increased to 35% when the environmental pH decreased from 7 to 6. The Lm interaction was characterized in a highly binding (about 65%) strain, OMGS105. The binding was rapid and required about 1 min and 1-2 h for 50% and 100% equilibrium respectively. The 125I-Lm binding was maximum in the pH interval 3.0 to 6.5 and could not be displaced by unlabeled Lm or inhibited by other proteins and carbohydrates. The interaction was stable in the presence of NaCl or urea (concentrations up to 4 M) but was dissociated by > or = 1 M KSCN. The Lm-binding component was thermolabile and sensitive to proteolytic enzymes. Sodium dodecylsulfate-polyacrylamide gel electrophoresis and Western blot analysis revealed a approximately 62 kDa Lm-binding protein, both in the whole cell extract and the outer membrane preparation. Weaker binding was also observed to other proteins. These data establish the ability of P. intermedia to interact with Lm via certain cell surface proteins, a property that might contribute to the colonization of this bacterium in the periodontal pocket.

Suppressive effect of soluble factor(s) derived from Prevotella loescheii ATCC 15930 on proliferation of human lymphocytes

Soluble sonic extracts of Prevotella loescheii caused a dose-dependent inhibition of human peripheral blood lymphocyte proliferation by mitogen and of the proliferation of a leukemic cell line, BALL-1, when assessed by DNA synthesis (3H-thymidine incorporation). RNA (3H-uridine incorporation) and protein (3H-leucine incorporation) synthesis were similarly altered after exposure to the extract. There was no effect on cell viability as measured by either trypan blue exclusion or extracellular release of the cytoplasmic enzyme lactate dehydrogenase. Preliminary characterization indicates the suppressive factor(s) derived from P. loescheii to be a protein since it is heat-labile and trypsin-sensitive. The factor eluted in a peak on a high-pressure liquid chromatography gel filtration corresponding to a molecular weight of approximately 32,000. Since black-pigmented anaerobic rods have been implicated in the pathogenesis of periodontal disease, the data suggest that P. loescheii contributes to the disease process by suppressing lymphocyte function.

Serum IgG reactive with oral anaerobic microorganisms associated with infections of endodontic origin

Numerous species of bacteria have been implicated with infections of endodontic origin. The purpose of this study was to compare the levels of serum IgG antibodies reactive with a panel of 10 oral anaerobic microorganisms implicated in infections of endodontic origin. Serum samples were collected from 4 patient groups that included healthy patients without endodontic or periodontal disease, patients with chronic adult periodontal disease, patients with endodontic disease and patients with combined endodontic-periodontal disease. When Prevotella intermedia was allowed to react with sera from the 4 patient groups, significant pairwise differences were shown between the healthy group and each of the other 3 groups. In addition, there was a significant difference between the periodontal disease group and the combined endodontic-periodontal disease group. When Porphyromonas gingivalis was allowed to react with sera from the 4 patient groups, significant pairwise differences were shown between the healthy group and the periodontal disease group, the healthy group and the combined endodontic-periodontal disease group, the endodontic disease group and the periodontal disease group and the endodontic disease group and the combined endodontic-periodontal disease group. The results of this investigation support other studies that associate P. intermedia with both endodontic disease and chronic adult periodontal disease. The results also support studies that implicate P. gingivalis as a periodontopathogen.

Immunosuppressive effects of Prevotella intermedia on in vitro human lymphocyte activation

In this study, we have assessed four strains of Prevotella intermedia, isolated from periodontally involved lesions, for their ability to inhibit lymphocyte functions. All four strains were found to cause a dose-dependent inhibition of B- and T-cell proliferation in response to mitogens and antigens. This was reflected in altered DNA, RNA, and protein syntheses. Furthermore, P. intermedia appeared to affect the early stages of cell activation. This was ascertained by kinetic analysis in which it was determined that the extract had to be present during the first 24 h of incubation to cause suppression. Moreover, direct assessment of the early stages of cell activation indicated that release of cytokines and expression of the interleukin 2 receptor and CD69 on T cells were inhibited by P. intermedia sonic extracts. Finally, preliminary characterization of the immunosuppressive agent indicates that it has a molecular mass of approximately 50 kDa and is heat labile. It has been proposed that impaired host defense may play a pivotal role in the pathogenesis of many infections. The data presented in this paper suggest that microbially mediated immunosuppression may contribute to the pathogenesis of periodontal disease by altering the nature and consequences of host-parasite interactions.

Elastolytic activity of Bacteroides nodosus isolated from sheep and goats with foot rot

The elastolytic activities of 82 Bacteroides nodosus strains were studied. Two substrates, insoluble elastin and soluble elastin, were used for this purpose. Roughly 15% of the strains which did not digest insoluble elastin were elastolytic with soluble elastin, the latter providing greater sensitivity, speed, and objectivity than its insoluble counterpart.

Identification of three gene regions associated with virulence in Dichelobacter nodosus, the causative agent of ovine footrot

Dichelobacter nodosus (formerly Bacteroides nodosus) is a Gram-negative strict anaerobe and is the primary pathogen involved in ovine footrot. A comparative hybridization strategy was used to isolate recombinant clones which hybridized to DNA from a virulent strain of D. nodosus but not with a benign isolate. Three virulence-associated gene regions were identified and one of these regions was shown to be present in multiple copies in the D. nodosus genome. Hybridization studies on 101 clinical isolates of D. nodosus showed that these strains could be divided into three hybridization categories which could be correlated with the virulence of the isolates. The recombinant clones have considerable potential for the development of a gene-probe-based method for the differential diagnosis of ovine footrot.

[Microbiology of periodontitis. 1. The infective nature of periodontitis]

In the last years, guided tissue regeneration (GTR) and implantology have opened new possibilities for practical periodontologists in the treatment of advanced cases. For both techniques the successful therapy of the local infection of the pocket is a prerequisite. In the near future rapid tests for microbiological diagnoses and slow release devices for antibiotics will be available to achieve this aim easier. The following article will present the microbiological aspects of periodontitis and plaque control and show their relevance for the practitioner.

Phagocytosis of virulent Porphyromonas gingivalis by human polymorphonuclear leukocytes requires specific immunoglobulin G

No studies to date clearly define the interactions between Porphyromonas gingivalis and human peripheral blood polymorphonuclear leukocytes (PMN), nor has a protective role for antibody to P. gingivalis been defined. Using a fluorochrome phagocytosis microassay, we investigated PMN phagocytosis and killing of P. gingivalis as a function of P. gingivalis-specific antibody. Sera from a nonimmune rabbit and a healthy human subject were not opsonic for virulent P. gingivalis A7436, W83, and HG405; phagocytosis of these strains (but not 33277) required opsonization with hyperimmune antiserum (RaPg). Diluting RaPg with a constant complement source decreased proportionally the number of P. gingivalis A7436 cells phagocytosed per phagocytic PMN. Enriching for the immunoglobulin G fraction of RAPg A7436 enriched for opsonic activity toward A7436. An opsonic evaluation of 18 serum samples from adult periodontitis patients revealed that only 3 adult periodontitis sera of 17 with elevated immunoglobulin G to P. gingivalis A7436 were opsonic for A7436 and, moreover, that the serum sample with the highest enzyme-linked immunosorbent assay titer was most opsonic (patient 1). However, the opsonic activity of serum from patient 1 was qualitatively and not just quantitatively different from that of the nonopsonic human sera (but was less effective opsonin than RaPg). Strain variability was observed in resistance of P. gingivalis to phagocytosis, and opsonization was strain specific for some, but not all, strains tested. An evaluation of killing of A7436 revealed that serum killing and extracellular killing of P. gingivalis were less effective alone when compared with intracellular PMN killing alone.

Reactivity of IgG from explant cultures of periapical lesions with implicated microorganisms

The presence of IgG in periapical inflammatory lesions suggests that immune responses participate in the disease process. The purpose of this investigation was to study the reactivity of IgG from the supernatant fluids of explant cultures of periapical lesions with microorganisms implicated in infections of endodontic origin. Ninety periapical lesions that had been contiguous with the apex of a root were removed and maintained in explant cultures. A dot-enzyme-linked immunosorbent assay (dot-ELISA) was used to demonstrate the presence of IgG in the supernatant fluids of the explant cultures reactive with a panel of microorganisms associated with infections of endodontic origin. The percentages of reactivity by dot-ELISA follow: Bacteroides intermedius (84%), B. buccae (12%), Porphyromonas (Bacteroides) gingivalis (50%), P. endodontalis (58%), P. asaccharolyticus (17%), Peptostreptococcus micros (44%), P. anaerobius (26%), Eubacterium alactolyticum (34%), Fusobacterium nucleatum (14%), and Actinomyces israelii (6%). At least one of the three species of B. intermedius, P. gingivalis, or P. endodontalis tested gave a positive dot-ELISA with 89% of the supernatant fluids from explant cultures of periapical lesions. A lack of cross reactivity of IgG in supernatant fluids from explants of periapical lesions was demonstrated for the four strains of black-pigmented Bacteroides/Porphyromonas by dot-ELISA.

A novel mouse model to study the virulence of and host response to Porphyromonas (Bacteroides) gingivalis

We describe here the development of a mouse subcutaneous chamber model that allows for the examination of host-parasite interactions as well as the determination of gross pathology with Porphyromonas (Bacteroides) gingivalis challenge. When inoculated into stainless-steel chambers implanted subcutaneously in female BALB/c mice, P. gingivalis W83, W50, and A7436 (10(8) to 10(10) CFU) caused cachexia, ruffling, general erythema and phlegmonous, ulcerated, necrotic lesions, and death. P. gingivalis W50/BEI, HG405, and 33277 (10(10) CFU) produced localized abscesses in the mouse chamber model with rejection of chambers at the injection site. Analysis of chamber fluid from 33277-, HG405-, and W50/BEI-infected mice by cytocentrifugation revealed inflammatory cell debris, polymorphonuclear leukocytes, and high numbers of dead bacteria. In contrast, fluid from A7436-, W50-, and W83-infected mice revealed infiltration predominantly of polymorphonuclear leukocytes and live bacteria. Bacteria were found primarily associated with polymorphonuclear leukocytes in the fluid from W50-, HG405-, and W83-infected mice but not from A7436-infected mice. Viable isolates were recoverable from the chamber fluid through day 3 for W50/BEI, day 5 for 33277, day 6 for HG405, day 7 for W50, day 14 for W83, and day 26 for A7436. All strains induced a systemic immunoglobulin G response in serum and chamber fluid samples. The use of this model will allow us to examine the virulence of P. gingivalis as defined by the interaction of host response to localized infection with P. gingivalis.

Phagocytosis and virulence of different strains of Porphyromonas gingivalis

In this study 17 strains of Porphyromonas gingivalis, both reference and clinical isolates, were investigated for their in vitro interaction with human polymorphonuclear leukocytes, hydrophobicity, density, and virulence in a mouse model. The results of the phagocytosis, hydrophobicity, and density experiments showed that P. gingivalis strains could be divided into two distinct groups. One group of strains were readily attached and phagocytosed when exposed to the leukocytes. These bacteria were hydrophobic and had a higher buoyant density than the other group, which were poorly phagocytosed, had a low buoyant density, and were hydrophilic. This latter group also exhibited an extracellular meshwork resembling a glycocalyx when examined by electron microscopy. There were also significant differences between strains in the mouse pathogenicity model. Two strains caused an invasive, spreading infection compared with the other 15 strains which produced small, localized abscesses. There was no clear correlation between the results of the phagocytosis assay and the virulence of the bacteria when injected subcutaneously in mice. Resistance to phagocytosis may be important for survival of these bacteria, but it does not in itself imply the ability to cause damage to the host.

Sequence of fimbrial subunit-encoding genes from virulent and benign isolates of Dichelobacter (Bacteroides) nodosus

Both virulent and benign isolates of the ovine pathogen Dichelobacter (Bacteroides) nodosus produce polar fimbriae which have been implicated in twitching motility. The fimbrial subunit-encoding genes from two virulent and two benign serogroup-B isolates of D. nodosus were cloned and sequenced. Analysis of the deduced amino acid (aa) sequences of these subunits indicated the presence of substitutions that appeared to correlate with the virulence phenotype. However, these aa substitutions were located in variable regions of the protein where they are unlikely to alter the functional properties of the fimbriae. The aa sequences of the serogroup-B subunits had a very high level (91-95%) of similarity, particularly at the N terminus, where the conserved region extended up to aa 61. Specific aa substitutions within the subunit of one isolate may reflect its serotypic variation from the other serogroup-B subunits studied.

Role of Neisseria gonorrhoeae and Chlamydia trachomatis in intraabdominal abscess formation in the rat

Our concept of the pathogenesis of acute salpingitis and advanced pelvic infection, such as tuboovarian abscess, is evolving. Although Neisseria gonorrhoeae and Chlamydia trachomatis are thought to play a significant role in acute pelvic inflammatory disease, other microorganisms, such as aerobes and anaerobes, have repeatedly been reported to play a significant role, also, particularly in the patient with advanced disease. A study was designed to evaluate the pathogenesis, and particularly any synergistic role, of some aerobes and anaerobes with N gonorrhoeae and C trachomatis abscess formation. Using the rat model developed by Weinstein and Onderdonk, the study demonstrated that N gonorrhoeae and C trachomatis alone do not produce abscesses. However, when combined with facultative or anaerobic bacteria, synergism with abscess formation is noted frequently. The data support the hypothesis that N gonorrhoeae and C trachomatis initiate infection and that aerobic and anaerobic bacteria act synergistically to produce abscesses. In addition, microorganisms not inoculated were found to be recruited into the infectious process. The organisms may gain access to the peritoneal cavity via the lower genital tract or from transmucosal migration from the intestinal flora.

Characterisation of virulent and benign strains of Bacteroides nodosus

The extracellular proteases of 395 isolates of B. nodosus from ovine, bovine and caprine foot lesions were classified as either thermostable or thermolabile. Stable protease was associated with one and unstable protease with four distinctive isoenzyme patterns, each pattern differentiated by the relative mobility of paired isoenzymes. Pathogenicity tests on 64 isolates showed a correlation between the production of stable protease and the production of virulent ovine footrot lesions. The mean values for total protease activity, twitching motility and colony diameter were significantly higher for virulent compared to benign isolates, but the range of values overlapped. SDS-PAGE whole-cell electrophoretic profiles of virulent isolates were similar to the profiles of some benign isolates.

Interaction of extracellular vesicles of Bacteroides gingivalis W50 with human polymorphonuclear leucocytes

The effects of B. gingivalis W50 extracellular vesicles (ECV) on neutrophil chemotaxis and viability were assessed and compared with those of whole cells and the extracellular non-dialysable soluble protein (EP) fraction. None of the fractions tested, including soluble fractions derived from cells and ECV by sonication, induced neutrophil chemotaxis. Only ECV and cells inhibited f-MLP-stimulated chemotaxis. ECV and cells were cytotoxic towards neutrophils. The cytotoxic response was time dependent. The soluble EP fraction did not influence cell viability.

Haemagglutinating and haemolytic activity of the extracellular vesicles of Bacteroides gingivalis W50

The extracellular vesicles (ECV) and extracellular protein (EP) fractions of Bacteroides gingivalis W50 showed haemagglutinating (HA) activity towards sheep erythrocytes. Similar fractions from the nonpathogenic strain W50/BE1 did not haemagglutinate. W50 ECV HA activity was not inhibited by various glycosidase, phospholipase or protease pretreatments, sugars or amino acids, including arginine or lysine. The haemagglutinating activity of ECV was associated only with the extracellular vesicle membrane. The EP and ECV of both strains displayed haemolytic activity. This activity was apparently depressed in the presence of 10 mM dithiothreitol (DTT). All EP and ECV fractions degraded certain structural sheep erythrocyte membrane proteins. The greatest activity was displayed by W50 ECV and W50/BE1 EP and was enhanced by DTT. In the presence of DTT, the ECV of both strains degraded purified human haemoglobin but this activity was greatly reduced in its absence.

Cytotoxic and immunostimulatory effects of Bacteroides cell products

The etiologic role of Bacteroides in both periodontal and periapical infections has been well documented, with current interest focusing on the specific pathogenic mechanisms involved. The effects of cell fractions derived from Bacteroides gingivalis (BG), Bacteroides intermedius (BI), and Bacteroides asaccharolyticus (BA) have been studied in vitro through: an assessment of the direct cytotoxic effects on human gingival fibroblasts using a tetrazolium dye reduction assay, an evaluation of murine lymphocyte stimulation and interleukin-1 release, and the induction of human lymphocyte-mediated cytotoxicity. Both BG and BI stimulated interleukin-1 release (P less than 0.001), while BA, a nonoral organism, was not significantly active in this respect. Only BG sonicates were able to induce lymphocyte-mediated cytotoxicity (P less than 0.005). All three Bacteroides species demonstrated direct cytotoxic effects on cultured gingival fibroblasts, and these effects were related to the relative protein content and endotoxin activity of the sonicate preparations for each organism. These data show that BG and BI possess factors which may enhance their virulence through activities not shared with BA.

Chorioamnionitis in relation to gestational outcome in a Swedish population

In a histopathological study, from a homogeneous Swedish population with a better than average socio-economic standard, placentas from 161 singleton infants small for gestational age (SGA) and 322 singleton infants appropriate for gestational age (AGA) were examined for the presence of inflammation in the placental parenchymal membranes, cord and decidua. Acute chorioamnionitis including funiculitis was found in 13.4% of the total material, in 17% of term AGA-infants (GA, greater than or equal to 38 weeks), in 13% of preterm AGA-infants (less than or equal to 37 weeks) and in 6.8% of SGA-infants (p less than 0.001, compared to term AGA). Acute chorioamnionitis was correlated to vaginal delivery (p less than 0.01), rupture of the membranes greater than 24 hours (p less than 0.01), nulliparity (p less than 0.05) and amniocentesis (RR = 1.7). In nulliparous, chorioamnionitis was related to duration of labor greater than 16 hours (p less than 0.01). Streptococcal (p less than 0.01) and anaerobic vaginal infections (p less than 0.05) were also related to chorioamnionitis. Of 17 infants with sepsis, 6 had chorioamnionitis (p less than 0.05). Decidual inflammation was chronic in type and found in 4.5% of the placentas and was not related to chorioamnionitis, but to parity (p less than 0.05) and term AGA-infants (p less than 0.001).

Measurement of protease thermostability, twitching motility and colony size of Bacteroides nodosus

Total extracellular protease activity of Bacteroides nodosus in TAS liquid culture varied directly with cell mass and buffer concentration between 20 and 50 mM HEPES, MOPS and TES buffers, but not with Tris which gave anomalous high cell counts, nor with Na2Co3 which showed a decline of protease activity and cell mass. The stability of HEPES-buffered crude protease preparations were estimated on the basis of temperature or Ca2+ activity. Variation of the estimates for cellular twitching was greater than that for colony diameter in benign and virulent strains of B. nodosus. Surface translocation, quantified on the basis of colony diameter, reached a limit after 72 h incubation on modified TAS agar, ranging from 0.04 to 0.14 mm per h for six isolates tested.

Iron-regulated outer membrane proteins in the periodontopathic bacterium, Bacteroides gingivalis

Hemin has been implicated in the pathogenesis of the oral pathogen, Bacteroides gingivalis. In order to elucidate the role of hemin (iron) in the growth and expression of outer membrane proteins, B. gingivalis strain W50 was grown with and without hemin to induce iron-limitation. Cells grew slower under iron stress and growth was completely inhibited in the absence of added hemin. The outer membrane protein profiles of B. gingivalis grown under iron-replete and iron-restricted conditions were studied by extrinsic radiolabelling with [125I] and polyacrylamide gel-electrophoresis. The induction of 10 surface proteins, with apparent molecular weights of 26, 29, 50, 56, 58, 60, 62, 71, 77, and 80 Kd, was observed in B. gingivalis grown under iron-restricted conditions. These proteins were repressed under iron-replete conditions. We postulate the involvement of the iron-regulated proteins in hemin uptake and virulence in B. gingivalis.

Suppression of bactericidal activity of human polymorphonuclear leukocytes by Bacteroides gingivalis

The direct effects of the culture supernatant of oral microorganisms on the bactericidal activity of human polymorphonuclear leukocytes (PMNs) were investigated. The bactericidal activity of PMNs, which were preincubated with the supernatant of Bacteroides gingivalis, Bacteroides intermedius, Bacteroides melaninogenicus or phosphate-buffered saline, was examined by counting the surviving bacteria. B. gingivalis-treated PMNs were found to have a diminished ability for killing bacteria in the presence or absence of serum. The chemiluminescence response of PMNs, which were preincubated with the culture supernatant of B. gingivalis, was strikingly reduced compared with that of PMNs preincubated with phosphate-buffered saline or other bacterial culture supernatants. The production of superoxide anion (O2-) by PMNs stimulated with either formyl-methionyl-leucyl-phenylalanine or phorbol myristate acetate was reduced in both cases after the PMNs were preincubated with the culture supernatant of B. gingivalis. However, it was observed that there was more reduction in superoxide anion (O2-) production stimulated with formyl-methionyl-leucyl-phenylalanine compared with that stimulated with phorbol myristate acetate. These results suggest that B. gingivalis releases a factor which interferes with the bactericidal activity of PMNs by modulating the generation of reactive oxygen species. These suppressive effects on bactericidal activity may be important in the pathogenesis of this microorganism.

Molecular analysis of periodontal pathogens

Both Bacteroides gingivalis and Actinobacillus actinomycetemcomitans have been implicated in the destruction of periodontal tissues. To understand better the role putative virulence factors from the two bacterial species may play in an infection, the collagenase gene from Bact. gingivalis and the leucotoxin gene from A. actinomycetemcomitans were cloned. As it is intended to generate strains carrying defined mutations in these genes for in vitro and in vivo experiments, extensive restriction mapping and sequence analyses of these clones are being undertaken. Furthermore a conjugation system for Bact. gingivalis and A. actinomycetemcomitans will be established.

Bacteroides loeschei PK1295 cells express two distinct adhesins simultaneously

Bacteroides loeschei synthesizes two distinct adhesins that mediate its coaggregation with Streptococcus sanguis 34 and Actinomyces israeli PK14. Streptococcal adhesin-specific and actinomyces adhesin-specific monoclonal antibodies were used to prepare antibody-coated 5- or 10-nm gold particles. These were used in immunoelectron microscopic studies to establish that essentially all bacteroides cells in a population express both adhesins. In general, the two sizes of gold particles representing each type of adhesin appeared to be spatially separated on neighboring fimbriae of B. loeschei. Deposition of antibody-coated gold particles, representing both types of adhesin, at or near the same fimbria was observed less frequently.

Increased periodontal bone loss in temporarily B lymphocyte-deficient rats

In order to study the role of T lymphocytes and B lymphocytes in the development of marginal periodontitis, experiments were performed on specific-pathogen-free (SPF) rats with various immunologic profiles. The study comprised nude (congenitally T lymphocyte-deficient), thymus-grafted nude (T-lymphocyte reconstituted), anti-mu treated (temporarily B lymphocyte-deficient), and normal rats. When they were 5 to 9 weeks old, some of the rats were inoculated with Actinomyces viscosus. Bacteroides gingivalis and a strain of oral spirochetes; 90 days later they were killed. A. viscosus and B. gingivalis colonized readily, but the spirochete strain could not be established permanently in the oral cavity of the rats, 95% of the inoculated rats raised serum IgG or IgM antibody against one or more of the microorganisms; nude rats tended to raise less antibody than the three other experimental groups. Inoculated rats had significantly less periodontal bone support than controls. Anti-mu treated inoculated rats had significantly less periodontal bone support than nude and normal rats, whereas no difference was found between normal, nude, and thymus-grafted rats. It is concluded that permanent T-lymphocyte deficiency did not interfere with the development of periodontal disease in this model, whereas a temporary and moderate reduction in B-lymphocyte numbers seemed to predispose for aggravation of periodontal bone loss.

The distribution of trypsin-like enzyme activity in cultures of a virulent and an avirulent strain of Bacteroides gingivalis W50

The distribution of trypsin-like enzyme activity was studied in 48- and 72-h batch cultures of Bacteroides gingivalis W50 and an avirulent variant (W50/BE1) of the parent strain. Activity was measured at pH 7.4 in cells, the extracellular vesicle (ECV) and soluble extracellular protein (EP) fractions recovered by ammonium sulphate precipitation from spent growth medium. Both organisms produced cell surface and extracellular vesicles, but whilst strain W50 produced more ECV, W50/BE1 yielded more of the EP fraction by weight. Whole cultures of W50 displayed a three-fold greater trypsin activity than those of W50/BE1. However, 90% of the total enzyme activity of W50 cultures was associated with the particulate fraction (cells and ECV totalled), whereas this fraction accounted for only 10-30% of the total for W50/BE1. Unlike W50/BE1, the specific activities of W50 cells and ECV rose in 72-h cultures. Conversely, cultures of W50/BE1 displayed an increase in the yield and specific activity of the EP fraction.

Lung abscess caused by Eikenella corrodens: report of a case

Eikenella corrodens is a slow-growing, facultatively anaerobic, gram-negative bacillus. It is part of the normal flora of the human upper respiratory tract. We report a 68-year-old man who developed lung abscesses caused by E. corrodens while on long-term corticosteroid therapy for polymyositis. It was isolated by percutaneous transthoracic aspiration of an abscess under real-time sonographic guidance. The organism has a very unusual antimicrobial susceptibility: sensitive to penicillin, ampicillin, cephapirin, chloramphenicol, minocycline and erythromycin but resistant to clindamycin, oxacillin and gentamicin. The patient was treated empirically with penicillin G and gentamicin. The latter was discontinued after the results of the bacterial culture and sensitivity test were available. He was discharged one month later with marked improvement. Our report clearly demonstrates that E. corrodens can be the sole pathogen of a respiratory tract infection.

Surface properties and ultrastructure of Porphyromonas gingivalis W50 and pleiotropic mutants

Cell surface ultrastructure and other surface properties of Porphyromonas gingivalis strain W50 and pleiotropic mutants W50/BP1 (brown), and W50/BE1 (beige) were studied. The percentage hydrophobicity of strains W50, W50/BP1, W50/BR1, and W50/BE1 gradually decreased from 24 to 9. Ruthenium red stained cells studied by transmission electron microscopy revealed a layer of extracellular polymeric material of varying thickness depending on the strain. The layer was thickest in W50/BP1 (15-20 nm), strains W50 and W50/BR1 both had a layer of 12-15 nm, while strain W50/BE1 completely lacked this layer. The results clearly showed that the hydrophobicity of P. gingivalis was related not only to the thickness of the layer but also to other factors like the composition of the capsular material, such that only strain W50/BE1, for example, showed no haemagglutinating activity. The surface properties of the pleiotropic mutants appeared to be stable characteristics as cells grown on either solid or in liquid media gave comparable results. The loss of virulence of the beige strain (W50/BE1) is probably partly due to the alteration of these surface properties. Both virulent and avirulent strains, however, possessed extracellular vesicles.

Effect of encapsulated Bacteroides asaccharolyticus and Bacteroides fragilis on the growth of aerobic and facultative bacteria in mixed infections

The effects of encapsulation of Bacteroides asaccharolyticus and Bacteroides fragilis on aerobic or facultative bacteria were evaluated using a subcutaneous abscess model in mice. The change in number of aerobic and facultative bacteria (AFB) was studied by comparing their number when injected with nonencapsulated, encapsulated Bacteroides species, and capsular material of Bacteroides species. In 14 combinations of AFB mixed with nonencapsulated Bacteroides species, an increase in the number of nonencapsulated Bacteroides species and an increase in the number of AFB occurred in two instances. An increase in the number of AFB occurred in 11 of the 14 combinations with encapsulated Bacteroides species. No change in the bacterial numbers was observed when the AFB were inoculated with capsular material of Bacteroides species. These data demonstrate the ability of viable encapsulated Bacteroides species to enhance the growth of aerobic or facultative bacteria.

Neuraminidase-enhanced attachment of Bacteroides intermedius to human erythrocytes and buccal epithelial cells

Bacteroides intermedius strains strongly agglutinated only neuraminidase-treated erythrocytes. The neuraminidase-dependent hemagglutinating activity of B. intermedius was abolished by heating or treating with protease. The adherence of these microorganisms to human buccal epithelial cells was enhanced by neuraminidase pretreatment of the cells (P less than 0.01).

Taxonomy, virulence and epidemiology of black-pigmented Bacteroides species in relation to oral infections

Black-pigmented Bacteroides species are recognized as suspected pathogens of oral infections. Developments in the taxonomy of this group include description of a new asaccharolytic species, Bacteroides salivosus, and proposal for the reclassification of the asaccharolytic species into a separate genus, Porphyromonas. Studies on the pathogenicity and virulence of black-pigmented Bacteroides species have identified Bacteroides gingivalis as the most virulent species. B. gingivalis and Bacteroides intermedius have been associated with periodontal diseases; Bacteroides endodontalis is isolated specifically from infections in the oral cavity, and other black-pigmented Bacteroides species are recovered from oral mucous sites. DNA restriction endonuclease analysis was adapted for typing of B. gingivalis and B. intermedius.

Heterogeneity of virulence among strains of Bacteroides gingivalis

The ability of fresh isolates of B. gingivalis to establish abscesses in the mouse model was studied by comparing them with established laboratory strains of B. gingivalis. Eight fresh isolates obtained from plaque associated with periodontal disease and grown under similar conditions as established strains were injected subcutaneously on the back of the mouse. All of these strains produced secondary lesions on the abdomen. Septicemia was associated with seven of the strains. Two commonly used laboratory strains, W50 and W83, also produced secondary lesions and septicemia. Five other laboratory strains produced only localized abscesses. On histologic examination, the strains that produced disseminated disease showed invasion of connective disease by individual bacteria that were not in clumps. The strains that produced localized abscesses were characterized by growing in colonies or clumps in the abscess cavity. Four synthetic enzyme substrates were examined to determine whether the differences between invasive and non-invasive strains were due to differences in proteolytic enzyme production. No differences in enzyme production could be demonstrated with the selected substrates.

Ultrastructure and enzyme activities of a virulent and an avirulent variant of Bacteroides gingivalis W50

The ultrastructure and enzyme activity of an avirulent, weakly-pigmenting, colonial variant (W50/BE1) was compared with that of the highly-virulent parent strain, Bacteroides gingivalis W50, in an attempt to identify significant virulence factors. Electron microscopy of thin sections of the organisms showed strain W50 to possess a 3-4-fold thicker layer of material external to the outer membrane. No significant differences between the strains were found with respect to collagen- or hyaluronic acid-breakdown activities at assay pH 7.5. However, cultures of strain W50 had over 3-fold more trypsin-like activity (P less than 0.01) than the avirulent variant. These results, when taken with other data, suggest that a thick external layer on the cell surface together with high trypsin-like activity might be important virulence factors of B. gingivalis.

Studies on the virulence properties and metabolism of pleiotropic mutants of Porphyromonas gingivalis (Bacteroides gingivalis) W50

Porphyromonas gingivalis (Bacteroides gingivalis) strain W50 and variants isolated from continuous culture designated W50/BP1 (black pigmented), W50/BR1 (brown pigmented) and W50/BE1 (beige or non-pigmented) were previously shown to lose virulence with the loss of pigmentation. Major properties which may affect the virulence and metabolism of P. gingivalis were compared amongst the 4 strains. The non-pigmented strain lost the ability to hemagglutinate sheep erythrocyte, had a reduced hydrophobicity and possessed lower levels of proteolytic activity. Defects in the electron transport system occurred at the level of cytochrome b but not menaquinone synthesis and resulted in an altered metabolic end product profile of the non-pigmented strain.

Collagenolytic activity of the extracellular vesicles of Bacteroides gingivalis W50 and an avirulent variant W50/BE1

The activities of the extracellular vesicle fractions of these two organisms were compared. Lytic activity against a native type I placental collagen substrate at 30 degrees C was assessed following sodium dodecyl sulphate-polyacrylamide gel electrophoresis and densitometry. A rapid rate of collagen depolymerization was achieved by the extracellular vesicle fraction of W50, yielding approx. 90% substrate degradation compared to 5% for W50/BE1 extracellular vesicles over 6 h incubation. The polypeptide digestion patterns produced by incubation with extracellular vesicle fractions of both organisms were identical, and similar to those yielded by incubation of substrate with whole W50 cells.