bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genomic Analysis of a Pathogenicity Island in Uropathogenic
Escherichia coli
CFT073: Distribution of Homologous Sequences among Isolates from Patients with Pyelonephritis, Cystitis, and CatheterAssociated Bacteriuria and from Fecal Samples
Authors: Guyer Debra M. , Kao Jyh-Shyang , Mobley Harry L. T. 
Published: March 2020

ABSTRACT

Urinary tract infection is the most frequently diagnosed kidney and urologic disease and
Escherichia coli
is by far the most common etiologic agent. Uropathogenic strains have been shown to contain blocks of DNA termed pathogenicity islands (PAIs) which contribute to their virulence. We have defined one of these regions of DNA within the chromosome of a highly virulent
E. coli
strain, CFT073, isolated from the blood and urine of a woman with acute pyelonephritis. The 57,988-bp stretch of DNA has characteristics which define PAIs, including a size greater than 30 kb, the presence of insertion sequences, distinct segmentation of K-12 and J96 origin, GC content (42.9%) different from that of total genomic DNA (50.8%), and the presence of virulence genes (
hly
and
pap
). Within this region, we have identified 44 open reading frames; of these 44, 10 are homologous to entries in the complete K-12 genome sequence, 4 are nearly identical to the sequences of
E. coli
J96 encoding the HlyA hemolysin, 11 encode P fimbriae, and 19 show no homology to J96 or K-12 entries. To determine whether sequences found within the junctions of the PAI of CFT073 were common to other uropathogenic strains of
E. coli
, 11 probes were isolated along the length of the PAI and were hybridized to dot blots of genomic DNA isolated from clinical isolates (67 from patients with acute pyelonephritis, 38 from patients with cystitis, 49 from patients with catheter-associated bacteriuria, and 27 from fecal samples). These sequences were found significantly more often in strains associated with the clinical syndromes of acute pyelonephritis (79%) and cystitis (82%) than in those associated with catheter-associated bacteriuria (58%) and in fecal strains (22%) (
P
< 0.001). From these regions, we have identified a putative iron transport system and genes other than
hly
and
pap
that may contribute to the virulent phenotype of uropathogenic
E. coli
strains.
Early Events in Phagosome Establishment Are Required for Intracellular Survival ofLegionella pneumophila
Authors: Wiater Lawrence A. , Dunn Kenneth , Maxfield Frederick R. , Shuman Howard A. 
Published: March 2020

ABSTRACTDuring infection, the Legionnaires’ disease bacterium,Legionella pneumophila, survives and multiplies within a specialized phagosome that is near neutral pH and does not fuse with host lysosomes. In order to understand the molecular basis of this organism’s ability to control its intracellular fate, we have isolated and characterized a group of transposon-generated mutants which were unable to kill macrophages and were subsequently found to be defective in intracellular multiplication. These mutations define a set of 20 genes (19icm[for intracellular multiplication] genes anddotA[for defect in organelle trafficking]). In this report, we describe a quantitative assay for phagosome-lysosome fusion (PLF) and its use to measure the levels of PLF in cells that have been infected with either wild-typeL. pneumophilaor one of several mutants defective in differenticmgenes ordotA. By using quantitative confocal fluorescence microscopy, PLF could be scored on a per-bacterium basis by determining the extent to which fluorescein-labeledL. pneumophilacolocalized with host lysosomes prelabeled with rhodamine-dextran. Remarkably, mutations in the six genes that were studied resulted in maximal levels of PLF as quickly as 30 min following infection. These results indicate that several, and possibly all, of theicmanddotAgene products act at an early step during phagosome establishment to determine whetherL. pneumophila-containing phagosomes will fuse with lysosomes. Although not ruled out, subsequent activity of these gene products may not be necessary for successful intracellular replication.
Alteration of HLA-B27 Peptide Presentation after Infection of Transfected Murine L Cells byShigella flexneri
Authors: Boisgérault Florence , Mounier Joëlle , Tieng Vannary , Stolzenberg Marie-Claude , Khalil-Daher Iman , Schmid Michel , Sansonetti Philippe , Charron Dominique , Toubert Antoine 
Published: March 2020

ABSTRACTShigella flexneriis a triggering agent for reactive arthritis in HLA-B27-susceptible individuals. Considering the intracellular multiplication of bacteria, it seems likely that bacterial peptides may be presented by the major histocompatibility complex (MHC) class I pathway. To examine this hypothesis, we infected HLA-B*2705- and/or human β2-microglobulin-transfected murine L-cell lines with M90T, an invasive strain ofS. flexneri. Bacterial infection induced no detectable modifications in the biosynthesis and expression level of HLA-B27, as assessed by immunoprecipitation, Northern blot analysis, and flow cytometry. Using confocal microscopy, we observed that bacterial infection induced a clustering of HLA-B27 molecules during macropinocytosis and before bacterial dissemination from cell to cell. Peptides naturally bound to HLA-B27 molecules were acid eluted from infected cells and separated by high-performance liquid chromatography. Major differences were observed in high-performance liquid chromatography profiles and in the nature of peptides presented following bacterial infection. Although most of the antigens presented were not accessed by Edman degradation, we obtained two sequences partially homologous to bacterial proteins. These peptides lacked the major HLA-B27 peptide anchor (Arg) at position 2, and one had an unusual length of 14 amino acids. These data suggest that alterations in the peptide presentation by HLA-B27 occur during infection, which could be relevant to the pathogenesis of HLA-B27-related arthritis.
Beta Interferon Is Produced by
Chlamydia trachomatis
-Infected Fibroblast-Like Synoviocytes and Inhibits Gamma Interferon-Induced HLA-DR Expression
Authors: Rödel Jürgen , Groh Annemarie , Vogelsang Heinz , Lehmann Marc , Hartmann Matthias , Straube Eberhard 
Published: March 2020

ABSTRACT

Infection of fibroblast-like synovial cells with
Chlamydia trachomatis
(serotype D strain IC Cal 8) in culture induced the secretion of beta interferon (IFN-β). Chlamydial infection inhibited IFN-γ-induced expression of HLA-DR antigen in the cells. Addition of IFN-β antibody directly to infected cultures mitigated HLA-DR inhibition, suggesting involvement of produced IFN-β.
Synthesis and Characterization of a Protective Peptide-Based Vaccine againstSchistosoma mansoni
Authors: Tarrab-Hazdai Rebeca , Schechtman Deborah , Arnon Ruth 
Published: March 2020

ABSTRACTTwo synthetic peptides, corresponding to the N-terminal sequence of the 45-kDa subunit of the protective 9B antigen ofSchistosoma mansoniand differing in only one amino acid residue, were synthesized. These peptides were recognized by the protective monoclonal antibody 152-66-9B, as well as by sera of mice and humans infected with schistosomiasis. The peptides were coupled to a protein carrier and used for immunization. One of the peptides, 9B-peptide1, induced in mice significant protection against challenge infection, manifested in a 40 to 50% reduction in worm burden.
The pH 6 Antigen of
Yersinia pestis
Binds to β1-Linked Galactosyl Residues in Glycosphingolipids
Authors: Payne Dean , Tatham David , Williamson E. Diane , Titball Richard W. 
Published: March 2020

ABSTRACT

The
Yersinia pestis
pH 6 antigen was expressed by, and purified from,
Escherichia coli
containing cloned
psa
genes. By an enzyme-linked immunosorbence-based assay, purified pH 6 antigen bound to gangliotetraosylceramide (GM1A), gangliotriaosylceramide (GM2A), and lactosylceramide (LC) (designations follow the nomenclature of L. Svennerholm [J. Neurochem. 10:613–623, 1963]). Binding to GM1A, GM2A, and LC was saturable, with 50% maximal binding occurring at 498 ± 4, 390, and 196 ± 3 nM, respectively. Thin-layer chromatography (TLC) overlay binding confirmed that purified pH 6 antigen bound to GM1A, GM2A, and LC and also revealed binding to hydroxylated galactosylceramide. Intact
E. coli
cells which expressed the pH 6 antigen had a specificity similar to that of purified pH 6 in the TLC overlay assay except that nonhydroxylated galactosylceramide was also bound. The binding patterns observed indicate that the presence of β1-linked galactosyl residues in glycosphingolipids is the minimum determinant required for binding of the pH 6 antigen.
papG
Alleles among
Escherichia coli
Strains Causing Urosepsis: Associations with Other Bacterial Characteristics and Host Compromise
Authors: Johnson James R. 
Published: March 2020

ABSTRACT

Alleles I, II, and III of the P adhesin gene
papG
were sought by PCR among 75
Escherichia coli
blood isolates from adults with urosepsis, and the
papG
genotype was compared with associated bacterial characteristics and host compromise status. Allele II predominated over allele III in the total population (71% of the strains versus 7% for allele III;
P
< 0.01). Allele I was not encountered. In comparison with allele II, allele III was significantly associated with the presence of
hly
and the absence of
iuc
(which encode hemolysin and aerobactin biosynthesis), nonagglutination of digalactoside-coated beads, absence of aerobactin production, membership in serogroups O6 and O18, and host compromise, particularly cancer and upper urinary tract abnormalities.
The Alternative Sigma Factor, ς
E
, Is Critically Important for the Virulence of
Salmonella typhimurium
Authors: Humphreys Sue , Stevenson Andrew , Bacon Andrew , Weinhardt A. Barbara , Roberts Mark 
Published: March 2020

ABSTRACT

In
Escherichia coli
, extracytoplasmic stress is partially controlled by the alternative sigma factor, RpoE (ς
E
). In response to environmental stress or alteration in the protein content of the cell envelope, ς
E
upregulates the expression of a number of genes, including
htrA
. It has been shown that
htrA
is required for intramacrophage survival and virulence in
Salmonella typhimurium
. To investigate whether ς
E
-regulated genes other than
htrA
are involved in salmonella virulence, we inactivated the
rpoE
gene of
S. typhimurium
SL1344 by allelic exchange and compared the phenotype of the mutant (GVB311) in vitro and in vivo with its parent and an isogenic
htrA
mutant (BRD915). Unlike
E. coli
, ς
E
is not required for the growth and survival of
S. typhimurium
at high temperatures. However, GVB311 did display a defect in its ability to utilize carbon sources other than glucose. GVB311 was more sensitive to hydrogen peroxide, superoxide, and antimicrobial peptides than SL1344 and BRD915. Although able to invade both macrophage and epithelial cell lines normally, the
rpoE
mutant was defective in its ability to survive and proliferate in both cell lines. The effect of the
rpoE
mutation on the intracellular behavior of
S. typhimurium
was greater than that of the
htrA
mutation. Both GVB311 and BRD915 were highly attenuated in mice. Neither strain was able to kill mice via the oral route, and the 50% lethal dose (LD
50
) for both strains via the intravenous (i.v.) route was very high. The i.v. LD
50
s for SL1344, BRD915, and GVB311 were <10, 5.5 × 10
5
, and 1.24 × 10
7
CFU, respectively. Growth in murine tissues after oral and i.v. inoculation was impaired for both the
htrA
and
rpoE
mutant, with the latter mutant being more severely affected. Neither mutant was able to translocate successfully from the Peyer’s patches to other organs after oral infection or to proliferate in the liver and spleen after i.v. inoculation. However, the
htrA
mutant efficiently colonized the livers and spleens of mice infected i.v., but the
rpoE
mutant did not. Previous studies have shown that salmonella
htrA
mutants are excellent live vaccines. In contrast, oral immunization of mice with GVB311 was unable to protect any of the mice from oral challenge with SL1344. Furthermore, i.v. immunization with a large dose (∼10
6
CFU) of GVB311 protected less than half of the orally challenged mice. Thus, our results indicate that genes in the ς
E
regulon other than
htrA
play a critical role in the virulence and immunogenicity of
S. typhimurium
.
Immunological Characterization of a Protective Antigen of
Erysipelothrix rhusiopathiae
: Identification of the Region Responsible for Protective Immunity
Authors: Shimoji Yoshihiro , Mori Yasuyuki , Fischetti Vincent A. 
Published: March 2020

ABSTRACT

The gene encoding a protective protein antigen of the gram-positive bacterium
Erysipelothrix rhusiopathiae
, an important veterinary pathogen responsible for erysipelas in swine and a variety of diseases in animals, was cloned and sequenced. The gene encodes a polypeptide of 597 amino acids plus a putative signal sequence of 29 amino acids, resulting in a mature protein with a molecular mass of 69,017 Da. Sequence analysis of the gene product revealed a C-terminal region composed of nine tandem repeats of 20 amino acids and a total sequence that is nearly identical to that of the 64-kDa cell surface protein (SpaA) of the bacterium. Because of this similarity, the protein was designated SpaA.1. In this study, we examined whether the SpaA.1 protein could induce protective antibodies and whether we could identify the region involved in protective immunity. Both the mature SpaA.1 protein and its C-terminal repeat region, but not the N-terminal segment, were expressed in
Escherichia coli
and purified as a histidine-tagged fusion recombinant protein. Rabbit antiserum raised against the mature SpaA.1 protein passively protected mice from lethal challenge with a virulent homologous strain, Fujisawa-SmR, suggesting that protection is mediated by humoral antibodies. To determine which domain of the SpaA.1 protein is responsible for the observed protection, mice were actively immunized with either the mature SpaA.1 protein or the C-terminal repeat region and then challenged with Fujisawa-SmR. The result showed that mice immunized with the mature SpaA.1 protein, but not the C-terminal repeat region, were protected, suggesting that the protection-eliciting epitope(s) is located within the N-terminal two-thirds of the SpaA.1 molecule. This was confirmed by passive immunization experiments in which the protective activity of rabbit antiserum, raised against mature SpaA.1 protein, was not abolished by absorption with the purified recombinant C-terminal repeat region. In addition, antibodies specific for the C-terminal repeat region were unable to protect mice from lethal challenge. These results show that the N-terminal two-thirds of the SpaA.1 molecule may constitute a good vaccine candidate against erysipelas.
Construction and Characterization of Mutations within the
Klebsiella mrkD
1P
Gene That Affect Binding to Collagen Type V
Authors: Sebghati Tricia A. , Clegg Steven 
Published: March 2020

ABSTRACT

The fimbria-associated MrkD
1P
protein mediates adherence of type 3 fimbriate strains of
Klebsiella pneumoniae
to collagen type V. Currently, three different MrkD adhesins have been described in
Klebsiella
species, and each possesses a distinctive binding pattern. Therefore, the binding abilities of mutants possessing defined mutations within the
mrkD
1P
gene were examined in order to determine whether specific regions of the adhesin molecule were responsible for collagen binding. Both site-directed and chemically induced mutations were constructed within
mrkD
1P
, and the ability of the gene products to be incorporated into fimbrial appendages or bind to collagen was determined. Binding to type V collagen was not associated solely with one particular region of the MrkD
1P
protein, and two classes of nonadhesive mutants were isolated. In one class of mutants, the MrkD adhesin was not assembled into the fimbrial shaft, whereas in the second class of mutants, the adhesin was associated with fimbriae but did not bind to collagen. Both hemagglutinating and collagen-binding activities were associated with the MrkD
1P
molecule, since P pili and type 3 fimbriae carrying adhesive MrkD proteins exhibited identical binding properties.
Differential Protective Efficacy of DNA Vaccines Expressing Secreted Proteins ofMycobacterium tuberculosis
Authors: Kamath Arun T. , Feng Carl G. , Macdonald Murdo , Briscoe Helen , Britton Warwick J. 
Published: March 2020

ABSTRACTThe development of more-effective antituberculosis vaccines would assist in the control of the global problem of infection withMycobacterium tuberculosis. One recently devised vaccination strategy is immunization with DNA plasmids encoding individual microbial genes. Using the genes for theM. tuberculosissecreted proteins MPT64 (23 kDa), Ag85B (30 kDa), and ESAT-6 (6 kDa) as candidate antigens, DNA vaccines were prepared and tested for immunogenicity and protective efficacy in a murine model of aerosolized tuberculosis (TB). Intramuscular immunization with DNA-64 or DNA-85B resulted in the activation of CD4+T cells, which produce gamma interferon (IFN-γ), and high titers of specific immunoglobulin G antibodies. Further, DNA-64 induced major histocompatibility complex class I-restricted CD8+cytotoxic T cells. The addition of a eukaryotic leader sequence tompt64did not significantly increase the T-cell or antibody response. Each of the three DNA vectors stimulated a significant reduction in the level ofM. tuberculosisinfection in the lungs of mice challenged 4 weeks after immunization, but not to the levels resulting after immunization withMycobacterium bovisBCG. The vaccines showed a consistent hierarchy of protection, with the most effective being Ag85B, followed by ESAT-6 and then MPT64. Coimmunization with the three vectors resulted in a greater degree of protection than that induced by any single vector. This protective efficacy was associated with the emergence of IFN-γ-secreting T cells earlier than in infected animals immunized with a control vector. The efficacy of these DNA vaccines suggests that multisubunit vaccination may contribute to future vaccine strategies against TB.
Protein H, an Antiphagocytic Surface Protein inStreptococcus pyogenes
Authors: Kihlberg Britt-Marie , Collin Mattias , Olsén Arne , Björck Lars 
Published: March 2020

ABSTRACTSurface-associated M protein is a major virulence factor inStreptococcus pyogeneswhich confers bacterial resistance to phagocytosis. However, manyS. pyogenesstrains also express additional structurally related so-called M-like proteins. The strain studied here is of the clinically important M1 serotype and expresses two structurally related surface proteins, the M1 protein and protein H. Mutants were generated that expressed only one or none of these proteins at the bacterial surface. For survival in human blood either protein H or M1 protein was sufficient, whereas the double mutant was rapidly killed. The protein-binding properties of protein H, M1 protein, and the mutants suggest that bacterial binding of immunoglobulin G and factor H or factor H-like protein 1, which are regulatory proteins in the complement system, contribute to the antiphagocytic property.
A Novel Urease-Negative
Helicobacter
Species Associated with Colitis and Typhlitis in IL-10-Deficient Mice
Authors: Fox James G. , Gorelick Peter L. , Kullberg Marika C. , Ge Zhongming , Dewhirst Floyd E. , Ward Jerrold M. 
Published: March 2020

ABSTRACT

A spiral-shaped bacterium with bipolar, single-sheathed flagella was isolated from the intestines of IL-10 (interleukin-10)-deficient (IL-10
−/−
) mice with inflammatory bowel disease. The organism was microaerobic, grew at 37 and 42°C, and was oxidase and catalase positive but urease negative. On the basis of 16S rRNA gene sequence analysis and biochemical and phenotypic criteria, the organism is classified as a novel helicobacter. Cesarean section-rederived IL-10
−/−
mice without helicobacter infection did not have histological evidence of intestinal inflammation. However, helicobacter-free IL-10
−/−
, SCID/NCr, and A/JNCr mice experimentally inoculated with the novel urease-negative
Helicobacter
sp. developed variable degrees of inflammation in the lower intestine, and in immunocompetent mice, the experimental infection was accompanied by a corresponding elevated immunoglobulin G antibody response to the novel
Helicobacter
sp. antigen. These data support other recent studies which demonstrate that multiple
Helicobacter
spp. in both naturally and experimentally infected mice can induce inflammatory bowel disease. The mouse model of helicobacter-associated intestinal inflammation should prove valuable in understanding how specific microbial antigens influence a complex disease process.
Extracellular Cysteine Protease Produced byStreptococcus pyogenesParticipates in the Pathogenesis of Invasive Skin Infection and Dissemination in Mice
Authors: Lukomski Slawomir , Montgomery Charles A. , Rurangirwa Jacqueline , Geske Robert S. , Barrish James P. , Adams Gerald J. , Musser James M. 
Published: March 2020

ABSTRACTThe role of an extracellular cysteine protease encoded by thespeBgene in group AStreptococcus(GAS) skin infection was studied with a mouse model. Mice were injected subcutaneously with a wild-type GAS serotype M3 strain or a cysteine protease-inactivated isogenic derivative grown to stationary phase. The mortality rate of mice injected with the M3speBmutant strain was significantly decreased (P< 0.0008) compared to that of animals injected with the wild-type parental organism. The abscesses formed in animals infected with the cysteine protease mutant strain were significantly smaller (P< 0.0001) than those caused by the wild-type organism and slowly regressed over 3 to 4 weeks. In striking contrast, infection with the wild-type GAS isolate generated necrotic lesions, and in some animals the GAS disseminated widely from the injection site and produced extensive cutaneous damage. All of these animals developed bacteremia and died. GAS dissemination was accompanied by severe tissue and blood vessel necrosis. Cysteine protease expression in the infected tissue was identified by immunogold electron microscopy. These data demonstrate that cysteine protease expression contributes to soft tissue pathology, including necrosis, and is required for efficient systemic dissemination of the organism from the initial site of skin inoculation.
Human Embryonic Gastric Xenografts in Nude Mice: a New Model of
Helicobacter pylori
Infection
Authors: Lozniewski Alain , Muhale Filipe , Hatier Renee , Marais Armelle , Conroy Marie-Christine , Edert Danielle , le Faou Alain , Weber Michele , Duprez Adrien 
Published: March 2020

ABSTRACT

In vitro or animal models have been used to investigate the pathogenesis of
Helicobacter pylori
infection. However, extrapolation to humans of results obtained with these heterologous models remains difficult. We have developed a new model for the study of
H. pylori
infection that uses human entire embryonic stomachs engrafted in nude mice. At 80 days after implantation, 22 of these xenografts, which exhibited a mature gastric epithelium, were inoculated with 10
7
to 10
8
CFU of either
H. pylori
LB1, a freshly isolated
H. pylori
strain (
n
= 12), or
H. pylori
ATCC 49503 (
n
= 10). After 12-week examination,
H. pylori
LB1 persistently colonized the antrum of all inoculated grafts, as assessed by culture (mucus and mucosa), immunohistochemistry (mucosa), and a rapid urease test (mucus).
H. pylori
ATCC 49503, either before or after in vivo passage, permitted only a transient 2-week colonization in one of the five inoculated grafts in both groups. Colonization was always associated with an increase of gastric juice pH. A mild neutrophil infiltration of the gastric mucosa was noted solely in infected grafts. Transmission electron microscopy showed adherence of
H. pylori
organisms to epithelial cell surface. In six animals, intracytoplasmic location of this bacterium was observed in the antrum or the fundus. These results allow us to propose this model as a new ex vivo model for the study of specific
H. pylori
-gastric cell interactions.