bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Epidemiological and Phylogenetic Associations of Two Novel Putative Virulence Genes,
iha
and

iroN
E. coli

, among
Escherichia coli
Isolates from Patients with Urosepsis
Authors: Johnson James R. , Russo Thomas A. , Tarr Phillip I. , Carlino Ulrike , Bilge Sima S. , Vary James C. , Stell Adam L. 
Published: July 2002

ABSTRACT

Two novel putative
Escherichia coli
virulence genes,
iha
and
iroN
from
E. coli
(

iroN
E. coli

), were detected in 55 and 39%, respectively, of 67
E. coli
isolates from patients with urosepsis.
iha
and

iroN
E. coli

exhibited divergent associations with other putative virulence genes, phylogenetic markers, host characteristics, and antimicrobial resistance.
Extending the CD4+T-Cell Epitope Specificity of the Th1 Immune Response to an Antigen Using aSalmonella entericaSerovar Typhimurium Delivery Vehicle
Authors: Lo-Man Richard , Langeveld Jan P. M. , Dériaud Edith , Jehanno Muguette , Rojas Marie , Clément Jean-Marie , Meloen Robert H. , Hofnung Maurice , Leclerc Claude 
Published: July 2002

ABSTRACTWe analyzed the CD4 T-cell immunodominance of the response to a model antigen (Ag), MalE, when delivered by an attenuated strain ofSalmonella entericaserovar Typhimurium (SL3261*pMalE). Compared to purified MalE Ag administered with adjuvant, the mapping of the peptide-specific proliferative responses showed qualitative differences when we used theSalmonellavehicle. We observed the disappearance of one out of eight MalE peptides' T-cell reactivity upon SL3261*pMalE immunization, but this phenomenon was probably due to a low level of T-cell priming, since it could be overcome by further immunization. The most striking effect of SL3261*pMalE administration was the activation and stimulation of new MalE peptide-specific T-cell responses that were silent after administration of purified Ag with adjuvant. Ag presentation assays performed with MalE-specific T-cell hybridomas showed that infection of Ag-presenting cells by this intracellular attenuated bacterium did not affect the processing and presentation of the different MalE peptides by major histocompatibility complex (MHC) class II molecules and therefore did not account for immunodominance modulation. Thus, immunodominance of the T-cell response to microorganisms is governed not only by the frequency of the available T-cell repertoire or the processing steps in Ag-presenting cells that lead to MHC presentation but also by other parameters probably related to the infectious process and to the bacterial products. Our results indicate that, upon infection by a microorganism, the specificity of the T-cell response induced against its Ags can be much more effective than with purified Ags and that it cannot completely be mimicked by purified Ags administered with adjuvant.
Overexpression of Protective Antigen as a Novel Approach To Enhance Vaccine Efficacy ofBrucella abortusStrain RB51
Authors: Vemulapalli Ramesh , He Yongqun , Cravero Silvio , Sriranganathan Nammalwar , Boyle Stephen M. , Schurig Gerhardt G. 
Published: July 2002

ABSTRACTBrucella abortusstrain RB51 is an attenuated rough strain that is currently being used as the official live vaccine for bovine brucellosis in the United States and several other countries. We reasoned that overexpression of a protective antigen(s) ofB. abortusin strain RB51 should enhance its vaccine efficacy. To test this hypothesis, we overexpressed Cu/Zn superoxide dismutase (SOD) protein ofB. abortusin strain RB51. This was accomplished by transforming strain RB51 with a broad-host-range plasmid, pBBR1MCS, containing thesodCgene along with its promoter. Strain RB51 overexpressing SOD (RB51SOD) was tested in BALB/c mice for its ability to protect against challenge infection with virulent strain 2308. Mice vaccinated with RB51SOD, but not RB51, developed antibodies and cell-mediated immune responses to Cu/Zn SOD. Strain RB51SOD vaccinated mice developed significantly (P< 0.05) more resistance to challenge than those vaccinated with strain RB51 alone. The presence of the plasmid alone in strain RB51 did not alter its vaccine efficacy. Also, overexpression of SOD did not alter the attenuation characteristic of strain RB51.
Biosynthesis and Functions of Melanin in
Sporothrix schenckii
Authors: Romero-Martinez Rafael , Wheeler Michael , Guerrero-Plata Antonieta , Rico Guadalupe , Torres-Guerrero Haydée 
Published: July 2002

ABSTRACT

Sporothrix schenckii
is a human pathogen that causes sporotrichosis, an important cutaneous mycosis with a worldwide distribution. It produces dark-brown conidia, which infect the host. We found that
S. schenckii
synthesizes melanin via the 1,8-dihydroxynaphthalene pentaketide pathway. Melanin biosynthesis in the wild type was inhibited by tricyclazole, and colonies of the fungus were reddish brown instead of black on tricyclazole-amended medium. Two melanin-deficient mutant strains were analyzed in this study: an albino that produced normal-appearing melanin on scytalone-amended medium and a reddish brown mutant that accumulated and extruded melanin metabolites into its medium. Scytalone and flaviolin obtained from cultures of the reddish brown mutant were identified by thin-layer chromatography, high-performance liquid chromatography, and UV spectra. Transmission electron microscopy showed an electron-dense granular material believed to be melanin in wild-type conidial cell walls, and this was absent in conidial walls of the albino mutant unless the albino was grown on a scytalone-amended medium. Melanized cells of wild-type
S. schenckii
and the albino grown on scytalone-amended medium were less susceptible to killing by chemically generated oxygen- and nitrogen-derived radicals and by UV light than were conidia of the mutant strains. Melanized conidia of the wild type and the scytalone-treated albino were also more resistant to phagocytosis and killing by human monocytes and murine macrophages than were unmelanized conidia of the two mutants. These results demonstrate that melanin protects
S. schenckii
against certain oxidative antimicrobial compounds and against attack by macrophages.
Comparison of Protection in Rabbits against Host-Adapted and CultivatedBorrelia burgdorferifollowing Infection-Derived Immunity or Immunization with Outer Membrane Vesicles or Outer Surface Protein A
Authors: Shang Ellen S. , Champion Cheryl I. , Wu Xiao-Yang , Skare Jonathan T. , Blanco David R. , Miller James N. , Lovett Michael A. 
Published: July 2002

ABSTRACTIn this study, infection-derived immunity in the rabbit model of Lyme disease was compared to immunity following immunization with purified outer membrane vesicles (OMV) isolated fromBorrelia burgdorferiand recombinant outer surface protein A (OspA). Immunization of rabbits with OMV isolated from virulent strain B31 and its avirulent derivative B313 (lacking OspA and DbpA) conferred highly significant protection against intradermal injection with 6 × 104in vitro-cultivated virulentB. burgdorferi. This is the first demonstration of protective immunogenicity induced by OMV. While immunization with OspA and avirulent B31 OMV provided far less protection against this challenge, rabbits with infection-derived immunity were completely protected. Protection against host-adaptedB. burgdorferiwas assessed by implantation of skin biopsies taken from rabbit erythema migrans (a uniquely rich source ofB. burgdorferiin vertebrate tissue) containing up to 108spirochetes. While all of the OMV- and OspA-immunized rabbits were fully susceptible to skin and disseminated infection, rabbits with infection-derived immunity were completely protected. Analysis of the antibody responses to outer membrane proteins, including DbpA, OspA, and OspC, suggests that the remarkable protection exhibited by the infection-immune rabbits is due to antibodies directed at antigens unique to or markedly up-regulated in host-adaptedB. burgdorferi.
Influence of β2-Integrin Adhesion Molecule Expression and Pulmonary Infection withPasteurella haemolyticaon Cytokine Gene Expression in Cattle
Authors: Lee Haa-Yung , Kehrli Marcus E. , Brogden Kim A. , Gallup Jack M. , Ackermann Mark R. 
Published: July 2002

ABSTRACTβ2-Integrins are leukocyte adhesion molecules composed of alpha (CD11a, -b, -c, or -d) and beta (CD18) subunit heterodimers. Genetic CD18 deficiency results in impaired neutrophil egress into tissues that varies between conducting airways and alveoli of the lung. In this study, we investigated whether CD18 deficiency in cattle affects proinflammatory cytokine (PIC) expression in pulmonary tissue after respiratory infection withPasteurella haemolytica. Cattle were infected withP. haemolyticavia fiberoptic deposition of organisms into the posterior part of the right cranial lung lobe. Animals were euthanized at 2 or 4 h postinoculation (p.i.), and tissues were collected to assess PIC gene expression using antisense RNA probes specific for bovine interleukin-1α (IL-1α), IL-1β, IL-6, gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α) along with the β-actin (β-Act) housekeeping gene. Expression of PIC was induced at 2 h p.i. inP. haemolytica-infected cattle and continued to 4 h p.i. At 2 h p.i., induction of gene expression and increase of cells that expressed PIC were observed both in CD18+and CD18−cattle after inoculation ofP. haemolytica. The induction of gene expression withP. haemolyticainoculation was more prominent in CD18−cattle than in CD18+cattle by comparison to pyrogen-free saline (PFS)-inoculated control animals. At 4 h p.i., however, the induction of PIC, especially IL-1α, IL-6, and IFN-γ, in the lungs of CD18+cattle inoculated withP. haemolyticawas greater than that in lungs of the CD18−cattle. IFN-γ and TNF-α genes were not increased inP. haemolytica-inoculated CD18−cattle lungs compared to the PFS-inoculated control lungs at 4 h p.i. In PFS-inoculated lungs, we generally observed a higher percentage of cells and higher level of gene expression in the lungs of CD18−cattle than in the lungs of CD18+cattle, especially at 4 h p.i. The rate of neutrophil infiltration into the lungs of CD18−cattle at 2 h p.i. was significantly higher than that of CD18+cattle; at 4 h p.i., there was no difference between the two groups. These data suggest that β2-integrins may contribute to the induction of expression of some PIC genes, as a consequence ofP. haemolyticainfection.
Influence of Platelets and Platelet Microbicidal Protein Susceptibility on the Fate of
Staphylococcus aureus
in an In Vitro Model of Infective Endocarditis
Authors: Mercier Renee-Claude , Rybak Michael J. , Bayer Arnold S. , Yeaman Michael R. 
Published: July 2002

ABSTRACT

Several lines of evidence indicate that platelets protect against endovascular infections such as infective endocarditis (IE). It is highly likely that a principal mechanism of this platelet host defense role is the release of platelet microbicidal proteins (PMPs) in response to agonists generated at sites of endovascular infection. We studied the ability of platelets to limit the colonization and proliferation of
Staphylococcus aureus
in an in vitro model of IE. Three isogenic
S. aureus
strains, differing in their in vitro susceptibility to thrombin-induced platelet microbicidal protein-1 (tPMP), were used: ISP479C (parental strain; highly susceptible to tPMP [tPMP
s
]); ISP479R (transposon mutant derived from ISP479; tPMP resistant [tPMP
r
]); or 757-5 (tPMP
r
transductant of the ISP479R genotype in the ISP479 parental background). Time-kill assays and in vitro IE models were used to examine the temporal relationship between thrombin-induced platelet activation and
S. aureus
killing. In time-kill studies, early platelet activation (30 min prior to bacterial exposure) correlated with a significant bactericidal effect against tPMP
s
ISP479C (
r
2
> 0.90,
P
< 0.02) but not against tPMP
r
strains, ISP479R or 757-5. In the IE model, thrombin activation significantly inhibited proliferation of ISP479C within simulated vegetations compared to strains ISP479R or 757-5 (
P
< 0.05). The latter differences were observed despite there being no detectable differences among the three
S. aureus
strains in initial colonization of simulated vegetations. Collectively, these data indicate that platelets limit intravegetation proliferation of tPMP
s
but not tPMP
r
S. aureus
. These findings underscore the likelihood that platelets play an important antimicrobial host defense role in preventing and/or limiting endovascular infections due to tPMP
s
pathogens.
Transcriptional Analysis ofp30Major Outer Membrane Multigene Family ofEhrlichiacanisin Dogs, Ticks, and Cell Culture at Different Temperatures
Authors: Unver Ahmet , Ohashi Norio , Tajima Tomoko , Stich Roger W. , Grover Debra , Rikihisa Yasuko 
Published: July 2002

ABSTRACTEhrlichiacanis, an obligatory intracellular bacterium of monocytes and macrophages, causes canine monocytic ehrlichiosis.E.canisimmunodominant 30-kDa major outer membrane proteins are encoded by a polymorphic multigene family consisting of more than 20 paralogs. In the present study, we analyzed the mRNA expression of 14 paralogs in experimentally infected dogs andRhipicephalussanguineusticks by reverse transcription-PCR using gene-specific primers followed by Southern blotting. Eleven out of 14 paralogs inE.caniswere transcribed in increasing numbers and transcription levels, while the mRNA expression of the 3 remaining paralogs was not detected in blood monocytes of infected dogs during the 56-day postinoculation period. Three different groups ofR.sanguineusticks (adult males and females and nymphs) were separately infected withE.canisby feeding on the infected dogs. In these pools of acquisition-fed ticks as well as in the transmission-fed adult ticks, the transcript from only one paralog was detected, suggesting the predominant transcription of that paralog or the suppression of the remaining paralogs in ticks. Expression of the same paralog was higher whereas expression of the remaining paralogs was lower inE.caniscultivated in dog monocyte cell line DH82 at 25°C than inE.caniscultivated at 37°C. Analysis of differential expression ofp30multigenes in dogs, ticks, or monocyte cell cultures would help in understanding the role of these gene products in pathogenesis andE.canistransmission as well as in designing a rational vaccine candidate immunogenic against canine ehrlichiosis.
Use of Operon Fusions inMannheimia haemolyticaTo Identify Environmental andcis-Acting Regulators of Leukotoxin Transcription
Authors: Marciel Ann Marie , Highlander Sarah K. 
Published: July 2002

ABSTRACTThe leukotoxin ofMannheimia haemolyticais an important virulence factor that contributes to much of the pathology observed in the lungs of animals with bovine shipping fever pneumonia. We believe that identification of factors that regulate leukotoxin expression may provide insight intoM. haemolyticapathogenicity. The DNA sequence upstream of the leukotoxin operon is divergently shared by PlapT, which transcribes an arginine permease gene. The intergenic region contains several elements that are potential sites for transcriptional modulation of the promoters. We have developed plasmid-borne chloramphenicol acetyltransferase (cat) operon fusions, as well aslktC::catchromosomal fusions, to study transcription initiation inM. haemolytica. Using these genetic tools, we have identifiedcis-acting sequences and environmental conditions that modulate transcription of the leukotoxin andlapTpromoters. By deletion analysis, promoters were shown to rely on sequences upstream of their −10 and −35 regions for full activity. Direct repeats of the sequence TGT-N(11)-ACA and a static bend region caused by phased adenine tracts were necessary for full activation of Plkt. A computer-generated model of the promoter's structure shows how DNA bending brings the repeat sequences within close proximity to the PlktRNA polymerase, and we hypothesize that these repeats are a binding site for an activator of leukotoxin transcription. ThelktC::catoperon fusion was also used to demonstrate that, like that of other RTX toxins, leukotoxin transcription is environmentally regulated. Roles for iron deprivation and temperature change were identified.
Pulmonary Hypertension Syndrome in Broilers Caused byEnterococcus faecalis
Authors: Tankson J. D. , Thaxton J. P. , Vizzier-Thaxton Y. 
Published: July 2002

ABSTRACTA field strain ofEnterococcus faecaliswas administered to broiler chicks at doses of 0, 3 × 106, 1.5 × 107, and 2 × 107bacteria/bird either intra-abdominally or intravenously. In trials 1 to 3, birds were reared communally in a broiler house on pine shaving litter. In trial 4, challenged and control birds were maintained in separate isolation rooms in metal cages with raised wire floors. Challenged birds exhibited a characteristic cavity or depression in the external wall of the right ventricle. A subjective scoring system was devised to quantify challenge effects by assigning each heart a score of 1 to 4. The average number of birds, over all trials and over all dose levels, exhibiting the ventricular cavity was 93%. This value in controls was 5%. The average heart score for challenged birds was 3.1, and that for controls was 0.20. Heart scores of challenged and control chicks were not different in birds reared communally or in separate isolation rooms. Additionally, both routes of administration were equally effective. Results suggest that challenge withE. faecaliscaused pulmonary hypertension.
High-Level Expression of NRAMP1 in Peripheral Blood Cells and Tuberculous Granulomas fromMycobacterium bovis-Infected Bovines
Authors: Estrada-Chávez Ciro , Pereira-Suárez Ana L. , Meraz Marco A. , Arriaga Camila , Garcı́a-Carrancá Alejandro , Sánchez-Rodriguez Cristina , Mancilla Raúl 
Published: July 2002

ABSTRACTBy Western blotting, we demonstrate high-level expression of NRAMP1 proteins in peripheral blood cells and granulomas ofMycobacterium bovis-infected bovines. Immunohistochemistry of granulomatous lesions showed heavily labeled epithelioid macrophages and Langhans cells. These data suggest thatM. bovisinfection enhances NRAMP1 expression and that active tuberculosis can occur despite this response.
Pneumococcal Conjugate Vaccines Overcome Splenic Dependency of Antibody Response to Pneumococcal Polysaccharides
Authors: Breukels Mijke A. , Zandvoort Andre , van den Dobbelsteen Germie P. J. M. , van den Muijsenberg Adrie , Lodewijk Monique E. , Beurret Michel , Klok Pieter A. , Timens Wim , Rijkers Ger T. 
Published: July 2002

ABSTRACT

Protection against infections with
Streptococcus pneumoniae
depends on the presence of antibodies against capsular polysaccharides that facilitate phagocytosis. Asplenic patients are at increased risk for pneumococcal infections, since both phagocytosis and the initiation of the antibody response to polysaccharides take place in the spleen. Therefore, vaccination with pneumococcal polysaccharide vaccines is recommended prior to splenectomy, which, as in the case of trauma, is not always feasible. We show that in rats, vaccination with a pneumococcal conjugate vaccine can induce good antibody responses even after splenectomy, particularly after a second dose. The spleen remains necessary for a fast, primary response to (blood-borne) polysaccharides, even when they are presented in a conjugated form. Coadministration of a conjugate vaccine with additional nonconjugated polysaccharides of other serotypes did not improve the response to the nonconjugated polysaccharides. We conclude that pneumococcal conjugate vaccines can be of value in protecting asplenic or hyposplenic patients against pneumococcal infections.
Rapid, Transient Phosphatidylserine Externalization Induced in Host Cells by Infection withChlamydiaspp
Authors: Goth Samuel R. , Stephens Richard S. 
Published: July 2002

ABSTRACTChlamydiaorganisms are obligate intracellular bacterial pathogens responsible for a range of human diseases. Persistent infection or reinfection withChlamydia trachomatisleads to scarring of ocular or genital tissues, andChlamydia pneumoniaeinfection is associated with the development of atherosclerosis. We demonstrate thatC. trachomatisandC. pneumoniaeinfection in vitro elicits the externalization of the lipid phosphatidylserine on the surface of human epithelial, endothelial, granulocytic, and monocytic cells. Phosphatidylserine externalization is associated with cellular development, differentiation, and death. Infection-induced phosphatidylserine externalization was immediate, transient, calcium dependent, and infectious dose dependent and was unaffected by a broad-spectrum caspase inhibitor.Chlamydia-infected cells accelerated plasma clotting and increased the macrophage phagocytosis of infected cells that was phosphatidylserine dependent. The rapid externalization of phosphatidylserine by infected cells may be an important factor in the pathogenesis of chlamydial infections.
Modulation of Cytokine Release in Ex Vivo-Stimulated Blood from Borreliosis Patients
Authors: Diterich Isabel , Härter Luc , Hassler Dieter , Wendel Albrecht , Hartung Thomas 
Published: July 2002

ABSTRACTIn lipopolysaccharide-stimulated blood from 71 late-stage borreliosis patients, the ex vivo cytokine release capacity of tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ) was reduced to 28% ± 5% and to 31% ± 5% (P≤ 0.001), respectively, compared to that of 24 healthy controls. White blood cell counts were normal in both groups. To investigate direct interactions between the pathogen and the immune cells, blood from healthy controls was exposed in vitro to live or heat-killedBorreliaor toBorrelialysate. Compared to the pattern induced by bacterial endotoxins, a reduced release of TNF-α and IFN-γ and an enhanced secretion of interleukin-10 and granulocyte colony-stimulating factor was found. In blood from 10 borreliosis patients stimulated withBorrelialysate, TNF-α formation was decreased to 31% ± 14% and IFN-γ formation was decreased to 8% ± 3% (P≤ 0.001) compared to the cytokine response of blood from healthy controls (n= 24). We propose to consider anti-inflammatory changes in the blood cytokine response capacity elicited byBorreliaas a condition that might favor the persistence of the spirochete.
Clostridium difficile
Toxins Disrupt Epithelial Barrier Function by Altering Membrane Microdomain Localization of Tight Junction Proteins
Authors: Nusrat A. , von Eichel-Streiber C. , Turner J. R. , Verkade P. , Madara J. L. , Parkos C. A. 
Published: July 2002

ABSTRACT

The anaerobic bacterium
Clostridium difficile
is the etiologic agent of pseudomembranous colitis.
C. difficile
toxins TcdA and TcdB are UDP-glucosyltransferases that monoglucosylate and thereby inactivate the Rho family of GTPases (W. P. Ciesla, Jr., and D. A. Bobak, J. Biol. Chem. 273:16021–16026, 1998). We utilized purified reference toxins of
C. difficile
, TcdA-10463 (TcdA) and TcdB-10463 (TcdB), and a model intestinal epithelial cell line to characterize their influence on tight-junction (TJ) organization and hence to analyze the mechanisms by which they contribute to the enhanced paracellular permeability and disease pathophysiology of pseudomembranous colitis. The increase in paracellular permeability induced by TcdA and TcdB was associated with disorganization of apical and basal F-actin. F-actin restructuring was paralleled by dissociation of occludin, ZO-1, and ZO-2 from the lateral TJ membrane without influencing the subjacent adherens junction protein, E-cadherin. In addition, we observed decreased association of actin with the TJ cytoplasmic plaque protein ZO-1. Differential detergent extraction and fractionation in sucrose density gradients revealed TcdB-induced redistribution of occludin and ZO-1 from detergent-insoluble fractions constituting “raft-like” membrane microdomains, suggesting an important role of Rho proteins in maintaining the association of TJ proteins with such microdomains. These toxin-mediated effects on actin and TJ structure provide a mechanism for early events in the pathophysiology of pseudomembranous colitis.