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PubMed1994

A Rab1 mutant affecting guanine nucleotide exchange promotes disassembly of the Golgi apparatus.

The Golgi apparatus is a dynamic organelle whose structure is sensitive to vesicular traffic and to cell cycle control. We have examined the potential role for rab1a, a GTPase previously associated with ER to Golgi and intra-Golgi transport, in the formation and maintenance of Golgi structure. Bacterially expressed, recombinant rab1a protein was microinjected into rat embryonic fibroblasts, followed by analysis of Golgi morphology by fluorescence and electron microscopy. Three recombinant proteins were tested: wild-type rab, mutant rab1a(S25N), a constitutively GDP-bound form (Nuoffer, C., H. W. Davidson, J. Matteson, J. Meinkoth, and W. E. Balch, 1994. J. Cell Biol. 125: 225-237), and mutant rab1a(N124I) defective in guanine nucleotide binding. Microinjection of wild-type rab1a protein or a variety of negative controls (injection buffer alone or activated ras protein) did not affect the appearance of the Golgi, as visualized by immunofluorescence of alpha-mannosidase II (Man II), used as a Golgi marker. In contrast, microinjection of the mutant forms promoted the disassembly of the Golgi stacks into dispersed vesicular structures visualized by immunofluorescence. When S25N-injected cells were analyzed by EM after immunoperoxidase labeling, Man II was found in isolated ministacks and large vesicular elements that were often surrounded by numerous smaller unlabeled vesicles resembling carrier vesicles. Golgi disassembly caused by rab1a mutants differs from BFA-induced disruption, since beta-COP remains membrane associated, and Man II does not redistribute to the ER. BFA can still cause these residual Golgi elements to fuse and disperse, albeit at a slower rate. Moreover, BFA recovery is incomplete in the presence of rab1 mutants or GTP gamma S. We conclude that GTP exchange and hydrolysis by GTPases, specifically rab1a, are required to form and maintain normal Golgi stacks. The similarity of Golgi disassembly seen with rab1a mutants to that occurring during mitosis, may point to a molecular basis involving rab1a for fragmentation of the Golgi apparatus during cell division.

Animals↗
PubMed2000

Antibacterial action of structurally diverse cationic peptides on gram-positive bacteria.

Antimicrobial cationic peptides are ubiquitous in nature and are thought to be a component of the first line of defense against infectious agents. It is widely believed that the killing mechanism of these peptides on bacteria involves an interaction with the cytoplasmic membrane. Cationic peptides from different structural classes were used in experiments with Staphylococcus aureus and other medically important gram-positive bacteria to gain insight into the mechanism of action. The membrane potential-sensitive fluorophore dipropylthiacarbocyanine was used to assess the interactions of selected antimicrobial peptides with the cytoplasmic membrane of S. aureus. Study of the kinetics of killing and membrane depolarization showed that, at early time points, membrane depolarization was incomplete, even when 90% or more of the bacteria had been killed. CP26, a 26-amino-acid alpha-helical peptide with a high MIC against S. aureus, still had the ability to permeabilize the membrane. Cytoplasmic-membrane permeabilization was a widespread ability and an action that may be necessary for reaching an intracellular target but in itself did not appear to be the killing mechanism. Transmission electron microscopy of S. aureus and Staphylococcus epidermidis treated with CP29 (a 26-amino-acid alpha-helical peptide), CP11CN (a 13-amino-acid, proline- and tryptophan-rich peptide), and Bac2A-NH(2) (a linearized version of the 12-amino-acid loop peptide bactenecin) showed variability in effects on bacterial structure. Mesosome-like structures were seen to develop in S. aureus, whereas cell wall effects and mesosomes were seen with S. epidermidis. Nuclear condensation and abherrent septation were occasionally seen in S. epidermidis. Our experiments indicated that these peptides vary in their mechanisms of action and that the mechanism of action likely does not solely involve cytoplasmic-membrane permeabilization.

Amino Acid Sequence↗
PubMed1998

Phosphorylcholine on the lipopolysaccharide of Haemophilus influenzae contributes to persistence in the respiratory tract and sensitivity to serum killing mediated by C-reactive protein.

Haemophilus influenzae undergoes phase variation in expression of the phosphorylcholine (ChoP) epitope, a structure present on several invasive pathogens residing in the human respiratory tract. In this study, structural analysis comparing organisms with and without this epitope confirmed that variants differ in the presence of ChoP on the cell surface-exposed outer core of the lipopolysaccharide. During nasopharyngeal carriage in infant rats, there was a gradual selection for H. influenzae variants that express ChoP. In addition, genotypic analysis of the molecular switch that controls phase variation predicted that the ChoP+ phenotype was predominant in H. influenzae in human respiratory tract secretions. However, ChoP+ variants of nontypable H. influenzae were more sensitive to the bactericidal activity of human serum unrelated to the presence of naturally acquired antibody to ChoP. Serum bactericidal activity required the binding of C-reactive protein (CRP) with subsequent activation of complement through the classical pathway. Results of this study suggested that the ability of H. influenzae to vary expression of this unusual bacterial structure may correlate with its ability both to persist on the mucosal surface (ChoP+ phenotype) and to cause invasive infection by evading innate immunity mediated by CRP (ChoP- phenotype).

Amino Acid Sequence↗
PubMed2004

[Characterization of an extracellular protease from Clostridium difficile].

Clostridium difficile is an intestinal pathogen, which produces two main virulence factors, the exotoxins A and B. Other bacterial structures have been implicated in the colonization of the gastrointestinal tract, which is the first step of the pathogenic process. C. difficile expresses adherence factors and also, displays some surface-associated proteolytic activity, which could play a role in the physiopathology of this bacterium. The aim of this work was to study the protein named Cwp84 which displays significant homologies with many cysteine proteases. The coding catalytic domain of this protein has been cloned in the expression system pGEX-6P-1, as an in-frame fusion with the gluthatione S-transferase, and subsequently purified. The purified fraction showed proteolytic activity on gelatine and BAPNA, but not on azocoll, suggesting a highly selective substrate specificity. The results obtained from inhibition experiments confirmed that Cwp84 belongs to the cysteine protease family. Cwp84 could play a role in degrading some specific host proteins or in the maturation of surface-associated bacterial proteins.

Amino Acid Sequence↗
PubMed2006

Structural similarity between the hydrophobic fluorescent probe and lipid A as a ligand of MD-2.

Toll-like receptors (TLRs) belong to the family of pattern recognition receptors, as they recognize molecules sharing a broad structural pattern rather than a single defined structure. Bacterial LPS is recognized by MD-2, which is associated with the extracellular domain of TLR4. Understanding the molecular recognition pattern of MD-2 could lead to efficient inhibitors of the excessive LPS signaling needed for early treatment of sepsis. The effect of the acyl chain variability of lipid A on its biological activity indicates that in addition to electrostatic interactions, the recognition must also involve hydrophobic interactions. We show that the fluorescent hydrophobic probe bis-ANS binds to MD-2 with a dissociation constant in the 10 nanomolar range, both to glycosylated and to nonglycosylated MD-2, and requires its native conformation. The binding site of bis-ANS overlaps with the binding site of LPS and is in the proximity of the single tryptophan residue. Furthermore, photoincorporation of bis-ANS by UV light inhibits the ability of MD-2 to confer the LPS responsiveness to the TLR4-transfected HEK293 cell line. Our results show that the structural pattern recognized by MD-2 is defined by the hydrophobic patch and a pair of separated negative charges.

Cell Line↗
PubMed2004

Application of single-cell cultures of mouse splenocytes as an assay system to analyze the immunomodulatory properties of bacterial components.

Recently, various bacterial components have been suggested as initiating and modulating immune activation, thereby substantially affecting the complex and dynamic host/pathogen interactions. Herein, we present a valuable and simple methodology for determining the capacity of bacteria as well as defined bacterial structures to stimulate cellular effectors of the innate and cognate immune system. This assay format is based on the exposure of freshly prepared single-cell cultures of splenic cells derived from naive mice with the immunogen of interest. Herein, the determination of exclusive panels of cytokines by the ELISA, ELISpot, and FACS technology will serve as an indicator for the activation of defined arms of the immune system. An increased knowledge about microbial components with immunomodulatory properties will substantially contribute to a more detailed understanding of the dynamic interplay between the host and potential pathogens and, based on this knowledge, to the development of novel substances for the prevention and therapy of microbial infections.

Animals↗
PubMed2006

The Wingless homolog WNT5A and its receptor Frizzled-5 regulate inflammatory responses of human mononuclear cells induced by microbial stimulation.

Microarray--assisted gene--expression screens of human macrophages revealed WNT5A, a homolog of Wingless, a key regulator of Drosophila melanogaster embryonic segmentation and patterning, to be consistently up-regulated following stimulation with different mycobacterial species and conserved bacterial structures. The expression of WNT5A required Toll-like receptor signaling and NF-kappaB activation, which identifies a novel induction pathway for a Wingless homolog. We show that human peripheral-blood mononuclear cells express the WNT5A receptor Frizzled-5 (FZD5). Both WNT5A and FZD5 also were detected in granulomatous lesions in the lungs of Mycobacterium tuberculosis-infected patients. Functional studies showed that WNT5A and FZD5 regulate the microbially induced interleukin-12 response of antigen-presenting cells and interferon-gamma production by mycobacterial antigen-stimulated T cells. Our findings implicate the evolutionarily conserved WNT/Frizzled signaling system in bridging innate and adaptive immunity to infections.

Antigen-Presenting Cells↗
PubMed1984

Developmentally regulated expression of chimeric genes containing muscle actin DNA sequences in transfected myogenic cells.

A recombinant plasmid containing 2/3 of the rat skeletal muscle actin structural gene plus 730 bp of its 5' flanking region, spliced to the 3' end of the human epsilon-globin gene, was introduced into cells of the rat myogenic line L8. Myogenic clones carrying the actin/globin chimeric gene were isolated. In many of these clones, the expression of the gene greatly increased during differentiation (up to greater than 50-fold) and, in some clones, the amount of the chimeric gene transcripts in the differentiated cultures exceeded that of the native muscle actin gene transcripts. Furthermore, the temporal relation between differentiation of the cultures and the accumulation of the transcripts from the transferred genes was very similar to that of the native skeletal muscle actin gene, suggesting a similar mechanism of regulation. Endonuclease S1 analysis indicated a correct initiation and termination of the mRNA but suggested that a fraction of the chimeric actin/globin transcripts was not properly processed. To test whether the increased expression of the transferred gene which occurred during differentiation was determined by DNA sequences in the 5' region of the muscle actin gene, a plasmid (p alpha-CAT) containing 730 bp of the 5' flanking region of the rat skeletal muscle actin gene (plus the exon of the 5' untranslated region, and 25 bp of the first intron), spliced to the bacterial structural gene coding for chloramphenicol acetyl transferase (CAT), was constructed and introduced into L8 cells. In the majority of the isolated clones containing this plasmid, CAT activity increased many-fold during differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed2005

Helicobacter pylori in the etiology of cholesterol gallstones.

GOALS: We aimed to investigate the presence of bacterial structures in cholesterol gallstones and particularly presence of Helicobacter spp/H. pylori in gallstones by microbiologic cultivation, histopathologic staining, and polymerase chain reaction (PCR). BACKGROUND: Many studies suggest that different mechanisms are responsible for the formation of pigmented gallstones and cholesterol gallstones. Recently, studies showed that infection could have an important role in the formation of cholesterol gallbladder stones. STUDY: We examined 77 mixed cholesterol gallstones. After cholecystectomy, gallbladder cultures were done for H. pylori and other bacterium. Gallbladder has also been examined by three histopathologic staining methods (Warthin-Starry, hematoxylin eosin, and gram staining) for Helicobacter spp. In addition, 16S rRNA-PCR amplification was performed for Helicobacter spp in gallstones. Twenty postmortem gallbladders without gallstones were investigated by the same histopathologic and PCR methods for Helicobacter spp. as a control group. RESULTS: Different bacterium were isolated from 22 gallbladder samples (12 Escherichia coli, 8 Pseudomonas, and 2 clostridium) and H. pylori was isolated in 6 gallbladder samples. Helicobacter spp was found in 7 gallstones by PCR amplification. Helicobacter-like organisms were demonstrated in 18 samples by three different histopathologic methods. Helicobacter-like organisms were also found in five samples by the same histopathologic methods (Warthin-Starry, hematoxylin-eosin, and gram staining). Only four samples were found positive for Helicobacter spp/H. pylori by all methods. CONCLUSIONS: Bacterial population including H. pylori could have a possible role in the formation of cholesterol gallstones.

Adolescent↗
PubMed1989

Type 1 fimbriate strains of Escherichia coli initiate renal parenchymal scarring.

The renal scarring which characterizes chronic pyelonephritis is initiated by bacterial infection and is independent on the activation of an inflammatory response. Although the presence of polymorphonuclear leukocytes (PMN) is essential for initiating the scarring process, the bacterial structures responsible for their activation have not been investigated. In an animal model of chronic pyelonephritis the surface area of the renal scars produced by Type 1 fimbriate escherichia coli (E. coli) was significantly greater than that of those produced by P fimbriate and non-fimbriate strains (P less than 0.01). The activation of human PMN by the same Type 1 fimbriate organisms resulted in a significant release of lysosomal neutral protease activity (P less than 0.001) and activation of the respiratory burst (P less than 0.01). The neutral protease release in response to P fimbriate and non-fimbriate organisms was not significantly increased. The extent of renal scarring also correlated with the release of neutral protease activity (P less than 0.02) and with the degree of activation of the respiratory burst (P less than 0.05). These results demonstrate that the ability of E. coli strains to cause renal scars may be related to their capacity to express Type 1 fimbria, which may be a causative factor in the in vivo activation of the inflammatory response.

Animals↗
PubMed1984

Isolation and characterization of an outer membrane protein of Salmonella paratyphi B: a mitogen and polyclonal activator of human B lymphocytes.

Salmonella paratyphi B (S. paratyphi B) has been previously characterized as a human T-independent polyclonal B cell activator. To define further the nature of the bacterial structure responsible for these properties, we studied the effects of autoclaving and enzyme treatment of S. paratyphi B on its stimulatory capacity. We found that both autoclaving and papain treatment decreased the ability of S. paratyphi B to induce B cell activation, while trypsin treatment did not affect this capacity. Neither type of treatment affected the binding of S. paratyphi B to lymphocytes, suggesting that binding and B cell stimulation are mediated by different structures. The observation that B cell stimulation was significantly reduced by papain treatment led us to attempt to purify membrane proteins so that we could investigate whether they shared the stimulating capacity of S. paratyphi B. A water-insoluble, 43-45,000 mol. wt. protein, rich in aspartic acid, glutamine, glycine, alanine and leucine, similar in mol. wt. and physicochemical chemical properties to the porins of other gram negative bacteria, was isolated and designated as outer membrane protein (OMP). This protein was equally efficient to S. paratyphi B in inducing T-independent B cell activation. By performing time-course studies of [3H]-thymidine incorporation we observed a burst of mitogenic activity after stimulation of PBL or purified B cells with both S. paratyphi B and OMP peaking at 48-96 hr of culture (compared to 96-120 hr for the PWM proliferation peak), and with a magnitude of roughly 10% of that observed after PWM stimulation. Given the fact that the proportion of B lymphocytes in PBL is 4-12%, it appears likely that the proliferation burst seen with S. paratyphi B and OMP corresponds to a mitogenic effect mainly restricted to the B cell population.

Amino Acids↗
PubMed2006

Chemokine production and pattern recognition receptor (PRR) expression in whole blood stimulated with pathogen-associated molecular patterns (PAMPs).

Recognition of conserved bacterial structures called pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs), may lead to induction of a variety of "early immediate genes" such as chemokines. In the current study, we have in an ex vivo whole blood model studied the induction of the chemokines MIP-1alpha, MCP-1 and IL-8 by various PAMPs. The rate of appearance of Escherichia coli-Lipopolysaccharide (LPS) induced chemokines differed. The production of MIP-1alpha and IL-8 was after 1 h of stimulation significantly higher when compared to unstimulated whole blood, whereas MCP-1 was not significantly elevated until after 3 h. At peak levels the MIP-1alpha concentration induced by E. coli-LPS was 3-5-fold higher than MCP-1 and IL-8. By specific cell depletion, we demonstrated that all three chemokines were mainly produced by monocytes. However, the mRNA results showed that IL-8 was induced in both monocytes and granulocytes. The production of all three chemokines, induced by the E. coli-LPS and Neisseria meningitidis-LPS, was significantly inhibited by antibodies against CD14 and TLR4, implying these receptors to be of importance for the effects of LPS in whole blood. The chemokine production induced by lipoteichoic acid (LTA) and non-mannose-capped lipoarabinomannan (AraLAM) was, however, less efficiently blocked by antibodies against CD14 and TLR2. E. coli-LPS and LTA induced a dose-dependent increase of CD14, TLR2 and TLR4 expression on monocytes in whole blood. These data show that PAMPs may induce chemokine production in whole blood and that antibodies against PRRs inhibit the production to different extent.

Antibodies, Monoclonal↗
PubMed1981

Activation of the alternative pathway of complement in human serum by Propionibacterium acnes (Corynebacterium parvum) cell fractions.

Activation of the alternative pathway of complement is known to be initiated by bacterial structures. We have fractionated Propionibacterium acnes cells, purified various cell fractions, and tested their complement-activating ability in human serum chelated with ethyleneglycol bis-(beta-aminoethylether)-N,N1-tetraacetic acid. The majority of complement-activating activity was localized in the wall fraction. This activity was resistant to lipid extraction, protease, RNAse, DNAse and lysozyme treatment. NaIO4, formamide, and hot (but not cold) trichloroacetic acid (TCA) extraction ablated the complement-activating capacity of cell walls. Compounds removed by extraction failed to consume significant hemolytic activity against antibody-coated sheep erythrocytes (EA). Addition of TCA-extracted soluble material to cell wall suspensions resulted in an inhibition of hemolytic consumption by the cell wall. These results indicate that, in P. acnes, complement-activating molecules are located in the cell wall and are carbohydrate in nature. Peptidoglycan, lipid, protein, and nucleic acid do not appear to contribute to the cell wall's ability to activate complement.

Carbohydrates↗
PubMed2005

TLR-2 gene Arg753Gln polymorphism is strongly associated with acute rheumatic fever in children.

The recently described family of toll-like receptors (TLRs) is a key player in host immunity by mediating inflammatory reactions against a wide range of pathogens. Mutations and polymorphisms in TLRs have revealed the importance of TLRs in human defence against diseases. TLR-2 is reported to interact with different bacterial structures, including lipoproteins, peptidoglycan and lipoteichoic acid. To assess the role of TLR-2 gene polymorphism in acute rheumatic fever (ARF) etiopathology, 61 independent Caucasian Turkish patients and 91 child and 116 adult controls were studied. Antistreptolycin O, C-reactive protein, sedimentation and white blood cell counts were studied to evaluate the clinical characteristics of the patients. Genomic DNA was extracted from peripheral blood using a standard column extraction technique. The Arg753Gln and Arg677Trp polymorphisms were genotyped by polymerase chain reaction (PCR) restriction fragment length polymorphism. The PCR products for the TLR-2 gene were analysed on 1.5% agarose gel pre-stained with ethidium bromide. Compared with healthy adult controls, the Arg753Arg genotype was significantly decreased in the entire group of ARF cases [odds ratio (OR) 0.01, 95% confidence interval (95% CI) 0.0034-0.031, p<0.0001]. Significantly, ARF patients were just 16 times more frequent with Gln allele (OR 15.6, 95% CI 7.87-30.8, p<0.0001). Moreover, evidence for an intensifying effect of the Gln allele was noteworthy when patients with Arg753Gln genotype were compared with healthy controls (OR 97.1, 95% CI 32.5-290, p<0.0001). However, no Arg677Trp polymorphism was detected in either patients or controls. Our data suggest that there is strong evidence for the biological role of TLR-2 in ARF. The common TLR-2 Arg to Gln polymorphism at position 753 significantly contributes to the pathogenesis of ARF. These results will allow the construction of a profile of individuals prone to ARF and may assist in developing new therapies.

Adult↗
PubMed1994

In vitro evaluation of cefdinir (FK482), a new oral cephalosporin with enhanced antistaphylococcal activity and beta-lactamase stability.

Cefdinir (FK482), a new oral cephalosporin with enhanced beta-lactamase stability, was tested by microbroth dilution against respiratory, urogenital, and skin and skin-structure bacterial pathogens. Included were beta-lactamase (beta LAC)-producing and -nonproducing isolates. Activity was compared with that of other orally administered beta-lactams. Cefdinir minimum inhibitory concentrations for 90% of isolates MIC90s (microgram/ml) were < or = 0.5 versus beta LAC+/oxacillin-susceptible Staphylococcus, aureus, S. epidermidis, and S. saprophyticus; < or = 0.06 versus Streptococcus groups A and B, and Neisseria gonorrhoeae beta LAC+; 0.125 versus S. pneumoniae penicillin-susceptible and Proteus mirabilis beta LAC+; 0.25 versus beta LAC+ versus strains of Moraxella catarrhalis, Escherichia coli, Klebsiella pneumoniae, and K. oxytoca; 0.5 versus Haemophilus influenzae beta LAC-; 1 versus H. influenzae beta LAC+; 4 versus Legionella pneumophila beta LAC+; and 8 versus Enterococcus faecalis beta LAC-strains. Cefdinir was equally effective against both standard and high inocula of S. aureus strains producing A, B, C, or D beta LAC types. MICs were also generated versus quality-control reference strains.

Bacteria↗
PubMed2005

Prokaryote diversity in the rumen of yak (Bos grunniens) and Jinnan cattle (Bos taurus) estimated by 16S rDNA homology analyses.

Prokaryote diversity in the rumen of yak (Bos grunniens) and Jinnan cattle (Bos taurus) was estimated by 16S rDNA homology analysis. Two rumen 16S rDNA libraries were constructed. Of the 194 clones in the library of yak rumen, the sequences were mainly clustered to two phyla, low G+C Gram-positive bacteria (LGCGPB, 54.12% total clones) and Bacteroidetes (30.93%), respectively. While in the 197 clone-library of the cattle rumen, the sequences were mainly related to three phyla, Bacteroidetes (39.59%), gamma-Proteobacteria (26.9%) and LGCGPB (22.34%), respectively. The sequence analysis indicated that more than half of the species harbored in yak rumen belonged to the not-yet-cultured groups at <90% 16S rDNA similarity levels with cultured species, while 36% 16S rDNA sequences amplified from the rumen of Jinnan cattle fell in these catalogues. By comparing the uncultured sequences in yak rumen with those in Jinnan cattle and cow, the former formed distinct clusters loosely related to the later, implying that yak rumen could harbor some special prokaryote phyla. 10.8% sequences retrieved in yak rumen were related to the known rumen fibrolytic bacterial species; however none was related to the known amylolysis species. While 4% and 17.8% sequences retrieved from Jinnan cattle rumen were related to cultured fibrolytic and amylolysis species, respectively. The bacterial structures seemed to be in accordance with the feed of the two kinds of animals. In both rumens, retrieved methanogenic Archaea-related 16S rDNA sequences were at an unreasonable low level; in addition, none sequence was related to Ruminococcus albus, a classical rumen fibrolytic species. The reason can be due to the experimental biases.

Journal Article↗
PubMed1981

Synthesis by DNA polymerase I on bleomycin-treated deoxyribonucleic acid: a requirement for exonuclease III.

phi X174 RFI DNA treated with bleomycin (BLM) under conditions permitting nicking does not serve as a template-primer for Escherichia coli DNA polymerase I. Purified exonuclease III from E. coli and extracts from wild-type E. coli strains are able to convert the BLM-treated DNA to suitable template-primer, but extracts from exonuclease III deficient strains are not. Brief digestion by exonuclease III is enough to create the template-primer, suggesting that the exonuclease III is converting the BLM-treated DNA by a modification of 3' termini. The exonucleolytic rather than the phosphatase activity of exonuclease III appears to be involved in the conversion. Comparative studies with micrococcal nuclease indicate that BLM-created nicks do not have a simple 3'-P structure. Bacterial alkaline phosphatase does not convert BLM-treated DNA to template-primer. The endonuclease VI activity associated with exonuclease III does not incise DNA treated with BLM under conditions not allowing nicking, in contrast to DNA with apurinic sites made by acid treatment, arguing that conversion does not require the endonuclease VI action on uncleaved sites.

Alkaline Phosphatase↗
PubMed1988

Dermatophilus congolensis and "hairy" leukoplakia.

The authors report the first human case (to our knowledge) of infection of the oral mucosa by Dermatophilus congolensis. Septate branching filaments morphologically identical to those of D. congolensis were identified in the lingual epithelium of a male homosexual employed as an animal handler. This actinomycete is the cause of dermatophilosis, a proliferative exudative dermatitis affecting many animal species. Clinical features suggested "hairy" leukoplakia (HL), a hyperkeratotic tongue lesion for which human papillomavirus (HPV) and Epstein-Barr virus (EBV) have been implicated as etiologic agents. Immunoperoxidase staining for HPV capsid antigen was negative. Direct immunofluorescent staining with a conjugate specific for D. congolensis identified the bacterial structures as those of this species while excluding morphologically similar organisms.

Actinomycetales↗