Sternoclavicular Septic Arthritis Due to Invasive Pneumococcal Infection After Type A Influenza Virus Infection

A 24-year-old female patient who had a type A influenza virus infection prior to admission visited our hospital complaining of a fever and right sternoclavicular pain. Blood culture was positive for penicillin-sensitive Streptococcus pneumoniae (pneumococcus). Magnetic resonance imaging of the right sternoclavicular joint (SCJ) showed a high signal intensity area on the diffusion-weighted images. Consequently, the patient was diagnosed with septic arthritis due to invasive pneumococcus. When a patient complains of gradually increasing chest pain after an influenza virus infection, SCJ septic arthritis should be considered in the differential diagnosis.

Diagnostic error rates and associated factors for lower gastrointestinal perforation

Lower gastrointestinal perforation is rare and challenging to diagnose in patients presenting with an acute abdomen. However, no study has examined the frequency and associated factors of diagnostic errors related to lower gastrointestinal perforation. This large-scale multicenter retrospective study investigated the frequency of diagnostic errors and identified the associated factors. Factors at the level of the patient, symptoms, situation, and physician were included in the analysis. Data were collected from nine institutions, between January 1, 2015 and December 31, 2019. Timely diagnosis was defined as diagnosis at the first visit in computed tomography (CT)-capable facilities or referral to an appropriate medical institution immediately following the first visit to a non-CT-capable facility. Cases not meeting this definition were defined as diagnostic errors that resulted in delayed diagnosis. Of the 439 cases of lower gastrointestinal perforation identified, delayed diagnosis occurred in 138 cases (31.4%). Multivariate logistic regression analysis revealed a significant association between examination by a non-generalist and delayed diagnosis. Other factors showing a tendency with delayed diagnosis included presence of fever, absence of abdominal tenderness, and unavailability of urgent radiology reports. Initial misdiagnoses were mainly gastroenteritis, constipation, and small bowel obstruction. In conclusion, diagnostic errors occurred in about one-third of patients with a lower gastrointestinal perforation.

Synthesis, Crystal Structure, and Luminescence Properties of a White-Light-Emitting Nitride Phosphor, Ca0.99Eu0.01AlSi4N7

Colorless transparent single crystals of a new europium-doped calcium aluminum silicon nitride, Ca_0.99Eu_0.01AlSi₄N₇, were synthesized by heating a mixture of binary nitrides (Ca₃N₂, EuN, AlN, Si₃N₄, and Mg₃N₂) at 2150 °C under a nitrogen gas pressure of 0.85 MPa. The X-ray diffraction reflections from a single crystal were indexed with orthorhombic cell parameters a = 11.6819(3) Å, b = 21.0193(6) Å, and c = 4.91770(10) Å. The crystal structure was isomorphic to that of SrAlSi₄N₇:Eu (space group Pna2₁). One of the Ca/Eu sites was split into two sites of 4-fold and 8-fold nitrogen coordination. A white-light emission spectrum with two peaks at wavelengths of 498 and 614 nm was observed from the single crystals under 400 nm near-ultraviolet-light irradiation. The CIE1931 chromaticity of the white light was plotted at x = 0.378 and y = 0.429; the mean color-rendering index Ra was 81.

Synthesis, Crystal Structure, and Photoluminescence of the Boron-Aluminum-Silicon Nitride Phosphor Sr3BAl5Si9N20:Eu

Single crystals of new boron-aluminum-silicon nitrides, Sr₃BAl₅Si₉N₂₀ and Sr_2.91Eu_0.09BAl₅Si₉N₂₀, were synthesized by heating binary nitride mixtures at 2030 °C under a N₂ pressure of 0.85 MPa. The X-ray diffraction spots from single crystals of these two compounds were indexed with the trigonal cell parameters a = 22.7406(8) Å, c = 5.7066(2) Å and a = 22.7439(8) Å, c = 5.7050(2) Å, respectively, and the crystal structures were determined to have the space group P3 c1, with B atoms situated at planar 3-fold-coordinated N sites. A three-dimensional framework structure is constructed for these materials based on the sharing of N atoms of Al/Si-N₄ tetrahedra and B-N₃ triangles. In this framework, Sr/Eu atoms are located at three sites, surrounded by 10 N atoms. Single crystals of Sr_2.91Eu_0.09BAl₅Si₉N₂₀ emitted yellow light with a peak wavelength of 565 nm and a full width at half-maximum of 106 nm under 450 nm light irradiation. The emission intensity of these crystals at 200 °C was found to be 12% of the intensity at 25 °C.

Role of Mfa5 in Expression of Mfa1 Fimbriae in Porphyromonas gingivalis

Fimbriae are protein-based filamentous appendages that protrude from the bacterial cell surface and facilitate host adhesion. Two types of fimbriae, FimA and Mfa1, of the periodontal pathogen Porphyromonas gingivalis are responsible for adherence to other bacteria and to host cells in the oral cavity. Both fimbrial forms are composed of 5 proteins, but there is limited information about their polymerization mechanisms. Here, the authors evaluated the function of Mfa5, one of the Mfa1 fimbrial accessory proteins. Using mfa5 gene disruption and complementation studies, the authors revealed that Mfa5 affects the incorporation of other accessory proteins, Mfa3 and Mfa4, into fibers and the expression of fimbriae on the cell surface. Mfa5 is predicted to have a C-terminal domain (CTD) that uses the type IX secretion system (T9SS), which is limited to this organism and related Bacteroidetes species, for translocation across the outer membrane. To determine the relationship between the putative Mfa5 CTD and the T9SS, mutants were constructed with in-frame deletion of the CTD and deletion of porU, a C-terminal signal peptidase linked to T9SS-mediated secretion. The ∆CTD-expressing strain presented a similar phenotype to the mfa5 disruption mutant with reduced expression of fimbriae lacking all accessory proteins. The ∆porU mutants and the ∆CTD-expressing strain showed intracellular accumulation of Mfa5. These results indicate that Mfa5 function requires T9SS-mediated translocation across the outer membrane, which is dependent on the CTD, and subsequent incorporation into fibers. These findings suggest the presence of a novel polymerization mechanism of the P. gingivalis fimbriae.

A Major Fimbrilin Variant of Mfa1 Fimbriae in Porphyromonas gingivalis

The periodontal pathogen Porphyromonas gingivalis is known to express 2 distinct types of fimbriae: FimA and Mfa1 fimbriae. However, we previously reported that fimbria-like structures were found in a P. gingivalis strain in which neither FimA nor Mfa1 fimbriae were detected. In this study, we identified a major protein in the bacterial lysates of the strain, which has been reported as the 53-kDa major outer membrane protein of P. gingivalis (53K protein) and subsequently reported as a major fimbrilin of a novel-type fimbria. Sequencing of the chromosomal DNA of the strain showed that the 53k gene (encoding the 53K protein) was located at a locus corresponding to the mfa1 gene (encoding the Mfa1 protein, which is a major fimbrilin of Mfa1 fimbriae) of the ATCC 33277 type strain. However, the 53K and Mfa1 proteins showed a low amino acid sequence homology and different antigenicity. The 53K protein was detected in 34 of 84 (41%) P. gingivalis strains, while the Mfa1 protein was detected in 44% of the strains. No strain expressed both 53K and Mfa1 proteins. Additionally, fimbriae were normally expressed in mutants in which the 53k and mfa1 genes were interchanged. These results indicate that the 53K protein is another major fimbrilin of Mfa1 fimbriae in P. gingivalis.

Domination of second-sphere shrinkage effect to improve photoluminescence of red nitride phosphors

Red Ca0.99Al(1-4δ/3-x)Si(1+δ+x)N(3-x)C(x):Eu(2+)0.01 (δ = 0.345; x = 0-0.2) nitride phosphors exhibit a blue-shifted emission with increased eye sensitivity function and excellent thermal stability. The variations in the photoluminescence in the Ca0.99Al(1-4δ/3-x)Si(1+δ+x)N(3-x)C(x):Eu(2+)0.01 (δ = 0.345; x = 0-0.2) system are thoroughly investigated. The enhanced emission energy and the improved thermal stability with increasing x are dominated by the second-sphere shrinkage effect via the substitution of small Si(4+) for large Al(3+) with simultaneous charge compensation. Related proofs of the second-sphere shrinkage effect control for photoluminescence are confirmed via high-resolution neutron powder diffraction, EXAFS, and (29)Si solid-state NMR techniques.

Localization and function of the accessory protein Mfa3 in Porphyromonas gingivalis Mfa1 fimbriae

The fimbriae of Porphyromonas gingivalis, the causative agent of periodontitis, have been implicated in various aspects of pathogenicity, such as colonization, adhesion and aggregation. Porphyromonas gingivalis ATCC 33277 has two adhesins comprised of the FimA and Mfa1 fimbriae. We characterized the PGN0289 (Mfa3) protein, which is one of the three accessory proteins of Mfa1 fimbriae in P. gingivalis. The Mfa3 protein was present in two different sizes, 40 and 43 kDa, in the cell. The 43-kDa and 40-kDa Mfa3 were detected largely in the inner membrane and the outer membrane, respectively. Purified Mfa1 fimbriae contained the 40-kDa Mfa3 alone. Furthermore, the 40-kDa Mfa3 started with the Ala(44) residue of the deduced amino acid sequence, indicating that the N-terminal region of the nascent protein expressed from the mfa3 gene is processed in the transport step from the inner membrane into fimbriae. Immuno-electron microscopy revealed that Mfa3 localized at the tip of the fimbrial shaft. Interestingly, deletion of the mfa3 gene resulted in the absence of other accessory proteins, PGN0290 and PGN0291, in the purified Mfa1 fimbriae, suggesting that Mfa3 is required for integration of PGN0290 and PGN0291 into fimbriae. A double mutant of mfa3 and fimA genes (phenotype Mfa1 plus, FimA minus) showed increased auto-aggregation and biofilm formation similar to a double mutant of mfa1 and fimA genes (phenotype Mfa1(-) , FimA(-) ). These findings suggest that the tip protein Mfa3 of the Mfa1 fimbriae may function in the integration of accessory proteins and in the colonization of P. gingivalis.

Genetic and antigenic analyses of Porphyromonas gingivalis FimA fimbriae

The periodontal pathogen Porphyromonas gingivalis generally expresses two distinct fimbriae, FimA and Mfa1, which play a role in biofilm formation. The fimA gene that encodes FimA fimbrilin is polymorphic, and polymerase chain reaction analysis has identified six genotypes called types I-V and Ib. We found recently that fimbriae exhibit antigenic heterogeneity among the genotypes. In the present study, we analysed the fimA DNA sequences of 84 strains of P. gingivalis and characterized the antigenicity of FimA fimbriae. Strains analysed here comprised 10, 16, 29, 13, 10 and 6 strains of types I, Ib, II, III, IV and V, respectively. DNA sequencing revealed that type Ib does not represent a single cluster and that type II sequences are remarkably diverse. In contrast, the fimA sequences of the other types were relatively homogeneous. Antigenicity was investigated using antisera elicited by pure FimA fimbriae of types I-V. Antigenicity correlated generally with the respective genotype. Type Ib strains were recognized by type I antisera. However, some strains showed cross-reactivity, especially, many type II strains reacted with type III antisera. The levels of fimbrial expression were highly variable, and expression was positively correlated with ability of biofilm formation on a saliva-coated plate. Further, two strains without FimA and Mfa1 fimbriae expressed fimbrial structures, suggesting that the strains produce other types of fimbriae.

Mechanism and implications of CXCR4-mediated integrin activation by Porphyromonas gingivalis

In monocytes and macrophages, the interaction of Porphyromonas gingivalis with Toll-like receptor 2 (TLR2) leads to the activation of a MyD88-dependent antimicrobial pathway and a phosphatidylinositol-3 kinase (PI3K) -dependent pro-adhesive pathway, which activates the β2 -integrin complement receptor 3 (CR3). By means of its fimbriae, P. gingivalis binds CXC-chemokine receptor 4 (CXCR4) and induces crosstalk with TLR2 that inhibits the MyD88-dependent antimicrobial pathway. In this paper, we investigated the impact of the P. gingivalis-CXCR4 interaction on the pro-adhesive pathway. Using human monocytes, mouse macrophages, or receptor-transfected cell lines, we showed that the binding of P. gingivalis fimbriae to CXCR4 induces CR3 activation via PI3K, albeit in a TLR2-independent manner. An isogenic strain of P. gingivalis expressing mutant fimbriae that do not interact with CXCR4 failed to efficiently activate CR3, leading to enhanced susceptibility to killing in vivo compared with the wild-type organism. This in vivo observation is consistent with previous findings that activated CR3 mediates safe entry of P. gingivalis into macrophages. Taken together with our previous work, these results indicate that the interaction of P. gingivalis with CXCR4 leads to inhibition of antimicrobial responses and enhancement of pro-adhesive responses, thereby maximizing its adaptive fitness in the mammalian host.

Energy filtering transmission electron microscopy immunocytochemistry and antigen retrieval of surface layer proteins from Tannerella forsythensis using microwave or autoclave heating with citraconic anhydride

Tannerella forsythensis (Bacteroides forsythus), an anaerobic Gram-negative species of bacteria that plays a role in the progression of periodontal disease, has a unique bacterial protein profile. It is characterized by two unique protein bands with molecular weights of more than 200 kDa. It also is known to have a typical surface layer (S-layer) consisting of regularly arrayed subunits outside the outer membrane. We examined the relationship between high molecular weight proteins and the S-layer using electron microscopic immunolabeling with chemical fixation and an antigen retrieval procedure consisting of heating in a microwave oven or autoclave with citraconic anhydride. Immunogold particles were localized clearly at the outermost cell surface. We also used energy-filtering transmission electron microscopy (EFTEM) to visualize 3, 3'-diaminobenzidine tetrahydrochloride (DAB) reaction products after microwave antigen retrieval with 1% citraconic anhydride. The three-window method for electron spectroscopic images (ESI) of nitrogen by the EFTEM reflected the presence of moieties demonstrated by the DAB reaction with horseradish peroxidase (HRP)-conjugated secondary antibodies instead of immunogold particles. The mapping patterns of net nitrogen were restricted to the outermost cell surface.

Identification and characterization of novel glycoproteins involved in growth and biofilm formation by Porphyromonas gingivalis

Porphyromonas gingivalis has been implicated as a major pathogen associated with chronic periodontitis. To extend our knowledge of post-translational protein glycosylation in P. gingivalis, a proteomic analysis involving two-dimensional polyacrylamide gel electrophoresis combined with carbohydrate staining and mass spectrometry was performed. Four novel glycoproteins, PGN0743, PGN0876, PGN1513 and PGN0729, in P. gingivalis ATCC 33277 were identified. These four identified glycoproteins possess a range of biochemical activities and cellular localization. PGN0743 contains a sequence motif identifying it as a FKBP-type cis-trans isomerase, which has activity usually associated with chaperone functions. PGN0876 and PGN1513 contain tetratricopeptide repeat domains that mediate protein-protein interactions. PGN0729 encodes the outer membrane protein 41 precursor, which was previously identified as Pgm6, and is homologous to the OmpA protein in Escherichia coli. Several different types of glycoprotein were identified, suggesting that P. gingivalis possesses a general mechanism for protein glycosylation. PGN0743-deficient and PGN0876-deficient mutants were constructed to examine the role(s) of the two identified glycoproteins. Both mutants showed a decreased growth rate under nutrient-limited conditions and reduced biofilm formation activity. These results suggest that the novel glycoproteins PGN0743 and PGN0876 play an important role in the growth and colonization of P. gingivalis.

OmpA-like protein influences cell shape and adhesive activity of Tannerella forsythia

Tannerella forsythia, a gram-negative fusiform rod, is implicated in several types of oral anaerobic infections. Most gram-negative bacteria have OmpA-like proteins that are homologous to the OmpA protein in Escherichia coli. We identified an OmpA-like protein in T. forsythia encoded by the tf1331 gene as one of the major proteins by mass spectrometric analysis. Two-dimensional, diagonal electrophoresis showed that the OmpA-like protein formed a dimeric or trimeric structure via intermolecular disulfide bonds. A biotin labeling experiment revealed that a portion of the protein was exposed on the cell surface, even though T. forsythia possesses an S-layer at the outermost cell surface. Using a tf1331-deletion mutant, we showed that the OmpA-like protein affected cell morphology. The length of the mutant cell was reduced almost by half. Cell swelling was observed in more than 40% of the mutant cells. Moreover, the mutant exhibited decreased adhesion to fibronectin, retarded autoaggregation, and reduced cell surface hydrophobicity. These results suggest that the OmpA-like protein in T. forsythia plays an important role in cellular integrity and adhesive function.

FimB regulates FimA fimbriation in Porphyromonas gingivalis

The periodontitis-associated pathogen Porphyromonas gingivalis colonizes and forms a biofilm in gingival crevices through fimbriae. It is known that the often-used strains ATCC 33277 and 381 produce long FimA fimbriae. We found a possible nonsense mutation within fimB, immediately downstream from fimA, coding a major subunit of FimA fimbriae of the strains. Indeed, P. gingivalis strains, except for ATCC 33277 and 381, universally expressed FimB, the gene product of fimB. Electron micrographs revealed that a FimB-restored strain had short and dense, "toothbrush"-like, FimA fimbriae. FimA overexpression elongated the fimbriae, whereas FimB overexpression shortened them. FimB restoration increased production of FimA and its accessory proteins. Thus, FimB regulates the length and expression of FimA fimbriae. Additionally, FimB restoration significantly reduced the release of FimA fimbriae from the cell surface, suggesting that FimB functions as an anchor of the fimbriae. The restoration enhanced adherent activity as well.

Differential virulence and innate immune interactions of Type I and II fimbrial genotypes of Porphyromonas gingivalis

INTRODUCTION

The fimA-encoded fimbriae of the periodontal pathogen Porphyromonas gingivalis display genetic diversity. Type I fimbriated P. gingivalis (Pg-I) has been most widely studied at the molecular level, whereas Pg-II is the most frequent isolate from severe periodontitis.

METHODS

To investigate virulence differences between Types I and II fimbriae, we examined strains 33277 (Pg-I) and OMZ314 (Pg-II), reciprocal swap mutants (i.e. expressing the heterologous fimbrial type), and their respective FimA-deficient derivatives. These organisms were tested in a mouse periodontitis model and in interactions with mouse macrophages, a cell type that plays important roles in chronic infections.

RESULTS

Strain 33277 induced significantly more periodontal bone loss than OMZ314 and substitution of Type II fimbriae with Type I in OMZ314 resulted in a more virulent strain than the parent organism. However, the presence of Type II fimbriae was associated with increased proinflammatory and invasive activities in macrophages.

CONCLUSION

The inverse relationship between proinflammatory potential and ability to cause experimental periodontitis may suggest that an aggressive phenotype could provoke a host response that would compromise the persistence of the pathogen.

A morphological and immunolabeling study of freeze-substituted Bacteroides forsythus

We used a rapid freezing and freeze-substitution technique without glutaraldehyde and OsO4 fixation for the electron microscopic immunocytochemical demonstration of the surface structure of Bacteroides forsythus, an anaerobic Gram-negative periodontopathogen. Cells were applied to pieces of filter paper and freeze-substituted by plunge-freezing in liquid propane, substituted in methanol containing 0.5% uranyl acetate, and infiltrated with LR White resin. The membrane ultrastructure of B. forsythus was preserved well, and the labeling density of the freeze-submitted cells was compared to a conventional processing method. Our results show the usefulness of the freeze-substitution method for immunohistochemical studies of B. forsythus.

Surface components of Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Research on Porphyromonas gingivalis, a periodontopathogen, has provided a tremendous amount of information over the last 20 years, which may exceed in part than that on other closely related members in terms of phylogenetic as well as proteomic criteria, including Bacteroides fragilis and B. thetaiotaomicron as major anaerobic, opportunistic pathogens in the medical field. In this minireview, we focused on recent research findings concerning surface components such as outer membrane proteins and fimbriae, of P. gingivalis.

MATERIAL AND METHODS

Elucidation of the surface components in P. gingivalis was especially difficult because outer membrane proteins are tightly bound to lipopolysaccharide and they are resistant to dissociation and separation from each other, even during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, unless samples are appropriately heated. In addition, P. gingivalis is asaccharolytic and therefore a potent proteolytic bacterium, another factor causing difficulty in research. The study of the surface components was carefully carried out considering these unique features in P. gingivalis when compared with other gram-negative bacteria, including Escherichia coli and Pseudomonas aeruginosa.

RESULTS

Separation of outer membrane proteins, and characterization of OmpA-like proteins and RagAB as major proteins, is described herein. Our recent findings on FimA and Mfa1 fimbriae, two unique appendages in this organism, and on their regulation of expression are also described briefly.

CONCLUSION

Surface components of P. gingivalis somehow have contact with host tissues and cells because of the outermost cell elements. Therefore, such bacterial components are potentially important in the occurrence of periodontal diseases.

Further evidence that major outer membrane proteins homologous to OmpA in Porphyromonas gingivalis stabilize bacterial cells

INTRODUCTION

Porphyromonas gingivalis is one of the most important bacteria in the progression of chronic periodontal disease. We hypothesized that the major outer membrane proteins Pgm6/7, which are homologous to the OmpA protein in Escherichia coli, might contribute to the stabilization of the cell surface. In this study, the effects of Pgm6/7 on the cell surface were examined morphologically.

METHODS

Deletion mutants of Pgm6/7 (Delta694, Delta695 and Delta695-694) were constructed using the polymerase chain reaction-based overlap extension method. Wild-type ATCC 33277 and Pgm6/7 mutants were grown under anaerobic conditions. Whole cells and thin sections of fixed cells were stained and examined by transmission electron microscopy.

RESULTS

Compared with the wild-type, numerous vesicles released from cells were observed in each deletion mutant. The outer membrane appeared wavy and irregular. Increased numbers of vesicles were confirmed after their preparation from the culture supernatant. Total gingipain activity in vesicles was increased five- to 10-fold in the deletion mutants.

CONCLUSION

This report provides further evidence that Pgm6/7 proteins in P. gingivalis play an important role in the maintenance of bacterial outer membrane integrity.

Downregulation of inhibitor of apoptosis proteins in apoptotic human chondrocytes treated with tumor necrosis factor-alpha and actinomycin D

OBJECTIVE

Apoptosis of chondrocytes plays a pivotal role in cartilage degeneration. Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine and has been assumed to cause the degradation of human cartilage. To investigate the mechanisms of TNF-alpha-mediated apoptosis of human chondrocytes from a point of view of the balance between the caspase-cascade and the expression of inhibitor of apoptosis proteins (IAPs), although both of them are induced with TNF-signals.

METHODS

The expression of TNF-receptors (TNF-Rs) in normal human articular chondrocyte (NHAC-kn) was examined with immunocytochemistry. Subconfluent cultures of NHAC-kn were tested with TNF-alpha and/or actinomycin D (actD), and the induction of apoptosis was evaluated by the frequency of apoptotic cells visualized with nuclear staining using Hoechst 33342. The activation of caspases and the expression of IAPs were examined with Western blot analyses.

RESULTS

NHAC-kn expressed TNF-R1 and -R2. When NHAC-kn was treated with TNF-alpha (10 ng/ml) and actD (0.2 microg/ml) for 24 h, the frequency of apoptotic cells increased to more than 25%. TNF-alpha alone, however, induced the apoptosis insufficiently (up to 8.3%), even when used at the concentration of 100 ng/ml for 48 h. In apoptotic human chondrocytes induced with TNF-alpha (10 ng/ml) and actD (0.2 microg/ml), the caspase-3, -8, and -9 were activated and the protein expression of XIAP and c-IAP1 decreased.

CONCLUSIONS

In apoptotic human chondrocytes induced with TNF-alpha and actD, the balance between caspase activation and IAPs' expression lay with the executioner caspase (caspase-3) and led to decreased expression of XIAP and c-IAP1.

Localization of Porphyromonas gingivalis-carrying fimbriae in situ in human periodontal pockets

Fimbriae, which are involved in adherence, constitute an important pathogenic factor of Porphyromonas gingivalis. In vivo, however, the distribution of P. gingivalis-carrying fimbriae is unknown. The localization of P. gingivalis-carrying fimbriae was examined in situ. From 19 patients with severe periodontitis and P. gingivalis, we obtained 20 teeth with periodontal tissue attached, with and without immunolocalized fimbriae. Eleven teeth were subjected to light microscopy, 9 to electron microscopy. In 6 of the 11 samples examined, we detected positive reactions with an anti-P. gingivalis-fimbriae serum, located in the cementum-attached plaque area in the deep pocket zones. In the so-called 'plaque-free zones', P. gingivalis-carrying fimbriae were immunocytochemically observed to reside in contact with the dental cuticle in 6 of the 9 samples examined. These findings suggest that P. gingivalis-carrying fimbriae are strongly related to adherence to the root surface at the bottoms of human periodontal pockets.

Bacteroides forsythus hemagglutinin is inhibited by N-acetylneuraminyllactose

Bacteroides forsythus, which has been recognized as a pathogen associated with periodontitis, produces a hemagglutinin. The hemagglutinin was localized in the envelope of B. forsythus. The hemagglutinating activity was inhibited by lactose at concentrations as low as 1 mM, and by L-arginine and L-lysine at concentrations of 100 mM. N-Acetylneuraminyllactose (NeuAc-lactose) was at least 100 times more potent an inhibitor than lactose, as it completely inhibited the hemagglutination at concentrations below 10 microM. This is similar to the Helicobacter pylori hemagglutinin. The hemagglutinin was heat-labile, and resistant to treatment with proteases such as trypsin. A specific antibody raised against one of the S-layer proteins that are major species-specific proteins had no inhibitory effect on the hemmaglutination. These results suggest that the NeuAc-lactose-sensitive adhesin of B. forsythus may play an important role in colonization in the oral cavity.

A MATE family multidrug efflux transporter pumps out fluoroquinolones in Bacteroides thetaiotaomicron

We cloned a gene, bexA, that codes for a multidrug efflux transporter from the chromosomal DNA of Bacteroides thetaiotaomicron ATCC 29741 by using an Escherichia coli DeltaacrAB DeltaacrEF mutant as a host. Although the initial recombinant construct contained other open reading frames, the presence of bexA alone was sufficient to confer to the E. coli host elevated levels of resistance to norfloxacin, ciprofloxacin, and ethidium bromide. Disruption of bexA in B. thetaiotaomicron made the strain more susceptible to norfloxacin, ciprofloxacin, and ethidium bromide, showing that this gene is expressed in this organism and functions as a multidrug efflux pump. The deduced BexA protein sequence was homologous to the protein sequence of Vibrio parahaemolyticus NorM, a multidrug efflux transporter, and thus, BexA belongs to the multidrug and toxic compound extrusion (MATE) family.

Localization of major, high molecular weight proteins in Bacteroides forsythus

Bacteroides forsythus produces species-specific major proteins with high molecular weights of 270 and 230-kDa (270K and 230K). A specific antibody raised against 270K was used for Western blot analysis and immunoelectron microscopy. Western blot analysis showed that the 270K and 230K proteins were immunologically similar. Immunogold labeling of ultrathin-sectioned bacterial cells and biochemical fractionation revealed that these proteins were localized at the outermost cell surface, not in the cytoplasm. These results suggest that major proteins ubiquitous to this species may form the S-layer.

Identification of a two-component signal transduction system involved in fimbriation of Porphyromonas gingivalis

Porphyromonas gingivalis, a periodontopathogen, is an oral anaerobic gram-negative bacterium with numerous fimbriae on the cell surface. Fimbriae have been considered to be an important virulence factor in this organism. We analyzed the genomic DNA of transposon-induced, fimbria-deficient mutants derived from ATCC 33277 and found that seven independent mutants had transposon insertions within the same restriction fragment. Cloning and sequencing of the disrupted region from one of the mutants revealed two adjacent open reading frames (ORFs) which seemed to encode a two-component signal transduction system. We also found that six of the mutants had insertions in a gene, fimS, a homologue of the genes encoding sensor kinase, and that the insertion in the remaining one disrupted the gene immediately downstream, fimR, a homologue of the response regulator genes in other bacteria. These findings suggest that this two-component regulatory system is involved in fimbriation of P. gingivalis.

Characterization of an outer membrane protein gene, pgmA, and its gene product from Porphyromonas gingivalis

A gene upstream from fimA, the gene encoding fimbrilin, on the chromosome of Porphyromonas gingivalis was sequenced and shown to be the gene encoding an outer membrane protein in this organism based on homology and biochemical analyses. Therefore, the gene (formerly ORF5) was designated pgmA, the P. gingivalis outer membrane protein A gene. The gene product, PgmA, was sensitive to protease, and was detected as a 60-kDa protein from wild-type strains with trichloroacetic acid treatment, which was carried out to destroy intrinsic proteases, and from protease-deficient mutants without this treatment prior to electrophoresis. PgmA was indeed present in the membrane fraction. Its nature was determined to be that of outer membrane proteins in gram-negative bacteria based on attempts at differential extraction of inner membrane proteins with detergents. No evidence has been found thus far from functional analyses that this protein is related to fimbrial morphogenesis and functions or to serum resistance of this organism.

Fimbria-mediated coaggregation between human oral anaerobes Treponema medium and Porphyromonas gingivalis

Bacterial binding phenomena among different bacterial genera or species play an important role in bacterial colonization in a mixed microbiota such as in the human oral cavity. The coaggregation reaction between two gram-negative anaerobes, Treponema medium and Porphyromonas gingivalis, was characterized using fimbria-deficient mutants of P. gingivalis and specific antisera against purified fimbriae and bacterial whole cells. T. medium ATCC 700273 strongly coaggregated with fimbriate P. gingivalis strains ATCC 33277 and 381, but not with afimbriate strains including transposon-induced fimbria-deficient mutants and KDP98 as a fimA-disrupted mutant of P. gingivalis ATCC 33277. In the P. gingivalis-T. medium coaggregation assay, the presence of rabbit antiserum against the purified fimbriae or the whole cells of P. gingivalis ATCC 33277 produced different "aggregates" consisting predominantly of P. gingivalis cells with few spirochetes, but both preimmune serum and the antiserum against the afimbriate KDP98 cells did not inhibit the coaggregation reaction. Heated P. gingivalis cells lost their ability to bind both heated and unheated T. medium cells. This T. medium-P. gingivalis coaggregation reaction was inhibited by a cysteine proteinase inhibitor, leupeptin, and also by arginine and lysine, but not by EDTA or sugars including lactose. A binding assay on nitrocellulose membranes and immunoelectron microscopy demonstrated that a heat-stable 37 kDa surface protein on the T. medium cell attached to the P. gingivalis fimbriae.

Changes in VEGF expression and in the vasculature during the growth of early-stage ethylnitrosourea-induced malignant astrocytomas in rats

Vascular endothelial growth factor (VEGF), a potent angiogenic and vascular permeability factor, may be important as a mediator of brain tumour progression. However, it is still not clear whether VEGF plays a causative role in the early stage of glioma development. We investigated the relationship between VEGF protein expression (as assayed by immunohistochemistry) and different morphological parameters reflecting tumour progression (tumour diameter, vascular density and vascular diameter) in tumours at various stages. As a tumour model, ethylnitrosourea (ENU)-induced rat malignant astrocytoma was used. Tumours were classified by size and level of vascularity estimated by the von Willebrand factor (vWF) staining. Tumours less than 10 mm in diameter were designated early stage neoplastic lesions. All 34 early astroglial tumours were found to be VEGF positive. Increase in the VEGF immunopositive rate of tumour cells correlated significantly with increase in vascular density and vascular diameter. We suggest that VEGF induces angiogenesis and growth of microvessels, promoting growth of the early stage malignant astrocytoma.

Arg-gingipain acts as a major processing enzyme for various cell surface proteins in Porphyromonas gingivalis

Arg-gingipain (RGP) is an Arg-X-specific cysteine proteinase produced by the Gram-negative anaerobe Porphyromonas gingivalis and has been shown to be a potent virulence factor in progressive periodontal disease (Nakayama, K., Kadowaki, T., Okamoto, K., and Yamamoto, K. (1995) J. Biol. Chem. 270, 23619-23626). In this study, we provide evidence that RGP acts as a major processing enzyme for various cell surface and secretory proteins in P. gingivalis. Fimbrilin, a major component of fimbriae, remained in the precursor form in the RGP-null mutant. Prefimbrilin expressed in Escherichia coli was converted to the mature fimbrilin in vitro when incubated with purified RGP, but its conversion was suppressed by potent RGP inhibitors. The results were consistent with the electron microscopic observation indicating little or no fimbriation in the RGP-null mutant. The immunogenic 75-kDa cell surface protein was also shown to retain its proform in the RGP-null mutant. In addition, Lys-gingipain (KGP) was found to be abnormally processed in the RGP-null mutant. In contrast, both prefimbrilin and the 75-kDa protein precursor were processed to their respective mature forms in the KGP-null mutant, suggesting that KGP is not involved in the normal processing mechanisms of these proteins. These results suggest that RGP not only acts as a direct virulence factor but also makes a significant contribution as a major processing enzyme to the virulence of P. gingivalis.

Active efflux of norfloxacin by Bacteroides fragilis

Norfloxacin was actively pumped out by Bacteroides fragilis, which is intrinsically resistant to most fluoroquinolones. Reserpine moderately inhibited the efflux. A one-step spontaneous mutant had increased resistance to norfloxacin, ethidium bromide, and puromycin, a result suggesting that the efflux is catalyzed by a multidrug pump with specificity similar to that of NorA/Bmr.

Capsular polysaccharide-fimbrial protein conjugate vaccine protects against Porphyromonas gingivalis infection in SCID mice reconstituted with human peripheral blood lymphocytes

The effect of immunization with either a Porphyromonas gingivalis fimbrial protein, a capsular polysaccharide, or a capsular polysaccharide-fimbrial protein conjugate vaccine were compared in hu-PBL-SCID mice. A significantly higher human immunoglobulin G antibody response and the highest degree of in vivo protection against bacterial challenge was observed in the group immunized with the conjugate vaccine. It was concluded that capsular polysaccharide-fimbrial protein conjugate from P. gingivalis could potentially be developed as a vaccine against periodontal infection by P. gingivalis.

Isolation and characterization of transposon-induced mutants of Porphyromonas gingivalis deficient in fimbriation

Fimbriae are considered to be an important virulence factor of Porphyromonas gingivalis. In order to identify genes essential for fimbriation, other than fimA which encodes the major subunit protein of fimbriae, transposon mutagenesis and immunological screening techniques were used to isolate fimbria-deficient mutants. R751::*Omega4, a suicide vector that carries Tn4351, was transferred from Escherichia coli to P. gingivalis by conjugation. Twenty-two independent fimbria-deficient mutants were identified among the resulting transformants. Southern hybridization analysis with pBlue 4351, a transposon-specific probe, and R751 indicated that 45% of the mutants resulted from single transposon insertions and that the remaining 55% of the mutants resulted from cointegration of R751 sequences. Southern hybridization analysis with pUCBg12.1, a probe for the fimA region, indicated that nine of the mutants contained insertions within the 2.5 kb SacI DNA fragment of P. gingivalis that contains fimA, ORF1 (which encodes a 15 kDa protein), and the C-terminal portion of ORF5 (which encodes a 63 kDa protein). Polymerase chain reaction (PCR) analysis and further Southern hybridization analysis indicated that the insertion site(s) for all nine of these mutants was within the fimA gene. Southern hybridization analysis also indicated that the remaining thirteen mutants contained insertions somewhere outside the 10 kb fimA region. Analysis by pulsed field gel electrophoresis (PFGE) revealed that insertions for most of the thirteen mutants mapped to a 300 kb NotI fragment and are located at least approximately 200 kb away from fimA. These results identify genetic loci other than fimA, that are required for fimbriation of P. gingivalis. Future cloning and characterization of these genetic loci should be straightforward since they are now marked by antibiotic resistance genes carried by the transposon.

Isolation and characterization of a nonpigmented variant of Porphyromonas endodontalis

Porphyromonas endodontalis forms dark colonies on media containing blood. We isolated, from an infected root canal, a non-black-pigmented P. endodontalis variant, KSEW01, which forms beige colonies on blood agar media. To characterize this variant, we compared its properties with those of two black-pigmented P. endodontalis strains, ATCC35406 and KSE105. Strain KSEW01 had a gelatinase activity comparable to that of the pigmented strains. Cell lysates of these three strains resolved by SDS-PAGE electrophoresis showed similar protein patterns. Quantitative DNA-DNA hybridization experiments indicated high homology between the nonpigmented strain KSEW01 and the two dark-pigmented strains. From these results, we identified strain KSEW01 as a P. endodontalis nonpigmented variant. DNA restriction endonuclease analysis indicated that the variant was closely related to a pigmented strain, KSE105. In contrast to the pigmented strains, strain KSEW01 did not degrade hemoglobin and formed no vesicles when cultured in the presence of blood. The susceptibilities of these three strains to 22 antibiotics were similar except for vancomycin. The nonpigmented variant was the most resistant to vancomycin (MIC: ATCC35406, 6.25 micrograms/ml; KSE105,12.5 micrograms/ml; KSEW01, 100 micrograms/ml). Overall, a relationship may exist between the presence of black-pigmentation and outer membrane systems of P. endodontalis.

Sequence and product analyses of the four genes downstream from the fimbrilin gene (fimA) of the oral anaerobe Porphyromonas gingivalis

The downstream DNA region of the fimbrilin gene (fimA), which encodes the major subunit protein of Porphyromonas gingivalis fimbriae, was fully sequenced. Gene products, expressed from this region in Escherichia coli, were purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and their partial amino acid sequences were determined to verify open reading frames (ORFs) found in the region by DNA sequencing. Four ORFs, designated ORF1, ORF2, ORF3 and ORF4, were found in the 5.8-kb PstI fragment downstream from fimA, which was previously cloned and partially characterized by Yoshimura, Takahashi, Hibi, Takasawa, Kato, and Dickinson (Infect. Immun. 61: 5181-5189, 1993). The direction of transcription of all the ORFs was the same as that of fimA. The 50 and 80 kDa encoded proteins, ORF2 and ORF3, respectively, have been reported to be minor components associated with fimbriae. The 15 and 19 kDa proteins, ORF1 and ORF4, respectively, have been expressed in E. coli but not identified in P. gingivalis. However, all the gene products of the ORFs, expressed in E. coli, appeared to contain intact signal peptides based on their N-terminal amino acid sequences.

Ultrastructure of collagen fibers in the outer membrane of recurrent chronic subdural hematoma

The three-dimensional structure of the collagen fibers in the outer membrane of recurrent chronic subdural hematoma was studied by scanning electron microscopy (SEM). Specimens obtained at surgery were treated with NaOH at room temperature to digest away all cellular components and expose the collagen fibers. SEM observation of the dural side of the outer membrane showed the collagen fibers were woven into a compact feltwork with a dense arrangement. The fiber bundles had a honeycomb structure framed by the collagen fibers. Observation of the hematoma side found the collagen bundles had a sparse wavy appearance. The arrangement of the collagen fibers on the dural side is different from that on the hematoma side. The thick outer membrane may be formed by granulation resulting from inflammatory reaction. Collagen fibrillar networks are not fragile, and may reinforce the outer membrane of the recurrent hematoma.

The induction of polyclonal B-cell activation and interleukin-1 production by the 75-kDa cell surface protein from Porphyromonas gingivalis in mice

The immunobiological activities of 75-kDa protein, fimbrial protein and lipopolysaccharide lipopolysaccharide prepared from whole cells of Porphyromonas gingivalis 381 were compared. The 75-kDa protein was mitogenic for BALB/c nu/nu, BALB/c and lipopolysaccharide-responsive C3H/HeN mouse spleen cells and for lipopolysaccharide-non-responsive C3H/HeJ mouse spleen cells. The response was significant in BALB/c mouse spleen cells incubated with 1-100 micrograms/ml of the 75-kDa protein. Furthermore, the 75-kDa protein exhibited polyclonal B-cell activation in murine spleen cells, which was similar to the lipopolysaccharide of P. gingivalis. In contrast, fimbriae from P. gingivalis did not, or only weakly, activated murine spleen cells. C3H/HeN mouse macrophages exposed to 10 micrograms/ml of the 75-kDa protein released large amounts of interleukin-1 (IL-1), which were maximal for 48 h, whereas IL-6 activity in macrophage supernatants was not detected throughout the culture period. These results suggest that the 75-kDa protein is a potent polyclonal B-cell activator and that it stimulates IL-1 production from murine peritoneal macrophages as well as lipopolysaccharide, which may play an important part in the inflammatory response during the development of periodontal diseases.

Involvement of arginine-specific cysteine proteinase (Arg-gingipain) in fimbriation of Porphyromonas gingivalis

Arginine-specific cysteine proteinase (Arg-gingipain [RGP], a major proteinase secreted from the oral anaerobic bacterium Porphyromonas gingivalis, is encoded by two separate genes (rgpA and rgpB) on the P. gingivalis chromosome and widely implicated as an important virulence factor in the pathogenesis of periodontal disease (K. Nakayama, T. Kadowaki, K. Okamoto, and K. Yamamoto, J. Biol. Chem. 270:23619-23626, 1995). In this study, we investigated the role of RGP in the formation of P. gingivalis fimbriae which are thought to mediate adhesion of the organism to the oral surface by use of the rgp mutants. Electron microscopic observation revealed that the rgpA rgpB double (RGP-null) mutant possessed very few fimbriae on the cell surface, whereas the number of fimbriae of the rgpA or rgpB mutant was similar to that of the wild-type parent strain. The rgpB+ revertants that were isolated from the double mutant and recovered 20 to 40% of RGP activity of the wild-type parent possessed as many fimbriae as the wild-type parent, indicating that RGP significantly contributes to the fimbriation of P. gingivalis as well as to the degradation of various host proteins, disturbance of host defense mechanisms, and hemagglutination. Immunoblot analysis of cell extracts of these mutants with antifimbrilin antiserum revealed that the rgpA rgpB double mutant produced small amounts of two immunoreactive proteins with molecular masses of 45 and 43 kDa, corresponding to those of the precursor and mature forms of fimbrilin, respectively. The result suggests that RGP may function as a processing proteinase for fimbrilin maturation. In addition, a precursor form of the 75-kDa protein, one of the major outer membrane proteins of P. gingivalis, was accumulated in the rgpA rgpB double mutant but not in the single mutants and the revertants, suggesting an extensive role for RGP in the maturation of some of the cell surface proteins.

Transient global amnesia and dural arteriovenous fistula of the anterior cranial fossa

Dural arteriovenous fistula (AVF) of the anterior cranial fossa is associated usually with cerebral hemorrhage or subarachnoid hemorrhage, while an association with transient global amnesia has not been reported previously. A case presenting the latter unusual symptom is described and the surgical treatment of AVF is discussed. A 64-year-old woman was hospitalized complaining of transient memory impairment. Magnetic resonance (MR) imaging demonstrated a flow void in the left frontal lobe and temporal pole. Cerebral angiography revealed an AVF in the anterior cranial fossa, which was fed bilaterally by the ethmoidal arteries and by branches of the external carotid arteries. The AVF drained into the superior sagittal sinus and the superficial sylvian vein via large varices. Following transfemoral embolization, surgical treatment was carried out. Postoperative angiography revealed complete obliteration of the anomaly. There were no further episodes of amnesia. In our presented case, there is an association between the presenting symptoms and the AVF. The combination of ischemia and congestion in the frontal and temporal lobes may have caused transient memory impairment. From our surgical experience, the excision of the vascular connection between the dura and the frontal lobe following the coagulation of the dura mater of the anterior part of the base of the skull without extensive excision seems to be recommended.

Identification of Porphyromonas gingivalis prefimbrilin possessing a long leader peptide: possible involvement of trypsin-like protease in fimbrilin maturation

Fimbriae of Porphyromonas gingivalis have been shown to be important as one of the virulence factors for colonization on mucosal surfaces. The gene (fimA) encoding the fimbrial subunit (fimbrilin) was overexpressed in Escherichia coli by using a bacteriophage T7 promoter-polymerase expression vector system. Analysis of the resulting fimA gene product revealed that the prefimbrilin had a 46 amino acid leader peptide. This extremely long leader peptide was cleaved from the prefimbrilin by treatment with trypsin or P. gingivalis extracts containing trypsin-like protease activity, resulting in production of a mature fimbrilin. We also found that some transposon-induced trypsin-like protease deficient mutants of P. gingivalis exhibited deficiency in fimbriation and that one of the mutants accumulated a fimbrilin precursor possessing a 25 amino acid leader peptide in the cell. The presence of an extremely long leader peptide and the requirement for a leader peptidase with a substrate specificity similar to that of P. gingivalis trypsin-like protease for fimbrilin maturation indicate that P. gingivalis fimbrilin is a novel type that is different from fimbrilins of type I and IV families.

Active site structure of a hemagglutinating protease from Porphyromonas gingivalis: similarity to clostripain

The active site of a 44-kDa hemagglutinating arginine-specific protease from the putative periodontopathogen Porphyromonas gingivalis was specifically labeled with N alpha-[3H]acetyllysine chloromethyl ketone. After enzymatic digestion of the labeled enzyme, a labeled active site peptide was isolated by HPLC. The sequence of the active site peptide was determined, after its treatment with NaBH4 to reduce the ketone group of the reagent moiety, to be Asp-Val-Ala-Cys-Val-Asn-Gly. The cysteine residue was found to be the site for labeling. The sequence resembled the active site structure of the arginine-specific cysteine protease clostripain from Clostridium histolyticum.

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

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

Transposon-induced pigment-deficient mutants of Porphyromonas gingivalis

Trypsin-like protease activity, hemagglutination activity, and accumulation of heme-containing compounds (black pigment) are considered to be virulence factors of Porphyromonas gingivalis. Transposon-mutagenesis was used for the first time to isolate pigment-deficient mutants. These mutants exhibited simultaneous deficiency in trypsin-like protease activity and hemagglutination activity. Two major membrane-associated proteins, observed by SDS-PAGE with the parent strain, were essentially absent from the mutant strains. Immunoblot analysis indicated that these two proteins correspond to putative hemagglutinin and hemagglutinin/protease products of P. gingivalis. Each mutant contained only one transposon insertion, thus the pleiotropic phenotype resulted from single site-specific mutations. The results indicate that trypsin-like protease activity is required for accumulation of protoheme from hemoglobin by P. gingivalis and that genetic and/or physiological linkage exists between trypsin-like protease activity and hemagglutination activity.