bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Therapeutic Chemical Agents In Vitro and on Experimental Meningoencephalitis Due toNaegleria fowleri
Authors: Kim Jong-Hyun , Jung Suk-Yul , Lee Yang-Jin , Song Kyoung-Ju , Kwon Daeho , Kim Kyongmin , Park Sun , Im Kyung-Il , Shin Ho-Joon 
Published: September 2008

ABSTRACTNaegleria fowleriis a ubiquitous, pathogenic free-living amoeba; it is the most virulentNaegleriaspecies and causes primary amoebic meningoencephalitis (PAME) in laboratory animals and humans. Although amphotericin B is currently the only agent available for the treatment of PAME, it is a very toxic antibiotic and may cause many adverse effects on other organs. In order to find other potentially therapeutic agents forN. fowleriinfection, the present study was undertaken to evaluate the in vitro and in vivo efficacies of miltefosine and chlorpromazine against pathogenicN. fowleri. The result showed that the growth of the amoeba was effectively inhibited by treatment with amphotericin B, miltefosine, and chlorpromazine. WhenN. fowleritrophozoites were treated with amphotericin B, miltefosine, and chlorpromazine, the MICs of the drug were 0.78, 25, and 12.5 μg/ml, respectively, on day 2. In experimental meningoencephalitis of mice that is caused byN. fowleri, the survival rates of mice treated with amphotericin B, miltefosine, and chlorpromazine were 40, 55, and 75%, respectively, during 1 month. The average mean time to death for the amphotericin B, miltefosine, and chlorpromazine treatments was 17.9 days. In this study, the effect of drugs was found to be optimal when 20 mg/kg was administered three times on days 3, 7, and 11. Finally, chlorpromazine had the best therapeutic activity againstN. fowleriin vitro and in vivo. Therefore, it may be a more useful therapeutic agent for the treatment of PAME than amphotericin B.
Use of Gyrase Resistance Mutants To Guide Selection of 8-Methoxy-Quinazoline-2,4-Diones
Authors: German Nadezhda , Malik Muhammad , Rosen Jonathan D. , Drlica Karl , Kerns Robert J. 
Published: September 2008

ABSTRACT

A series of 1-cyclopropyl-8-methoxy-quinazoline-2,4-diones was synthesized and evaluated for lowering the ratio of the antimicrobial MIC in gyrase resistance mutants to that in the
gyr
+
(wild type) using isogenic strains of
Escherichia coli
. Dione features that lowered this ratio were a 3-amino group and C-7 ring structure (3-aminomethyl pyrrolidinyl < 3-aminopyrrolidinyl < diazobicyclo < 2-ethyl piperazinyl). The wild-type MIC was also lowered. With the most active derivative tested, many
gyrA
resistance mutant types were as susceptible as, or more susceptible than, wild-type cells. The most active 2,4-dione derivatives were also more active with two quinolone-resistant
gyrB
mutants than with wild-type cells. With respect to lethality, the most bacteriostatic 2,4-dione killed
E. coli
at a rate that was affected little by a
gyrA
resistance mutation, and it exhibited a rate of killing similar to its cognate fluoroquinolone at 10× the MIC. Population analysis with wild-type
E. coli
applied to agar showed that the mutant selection window for the most active 2,4-dione was narrower than that for the cognate fluoroquinolone or for ciprofloxacin. These data illustrate a new approach to guide early-stage antimicrobial selection. Use of antimutant activity (i.e., ratio of the antimicrobial MIC in a mutant strain to the antimicrobial MIC in a wild-type strain) as a structure-function selection criterion can be combined with traditional efforts aimed at lowering antimicrobial MICs against wild-type organisms to more effectively afford lead molecules with activity against both wild-type and mutant cells.
Interspecies Recombination Occurs Frequently in Quinolone Resistance-Determining Regions of Clinical Isolates of
Streptococcus pyogenes
Authors: Duesberg Christoph B. , Malhotra-Kumar Surbhi , Goossens Herman , McGee Lesley , Klugman Keith P. , Welte Tobias , Pletz Mathias W. R. 
Published: September 2008

ABSTRACT

Fluoroquinolone resistance in
Streptococcus pyogenes
has been reported only anecdotally, but a recent Belgian surveillance study found a rate of nonsusceptibility of 5.4%. From an analysis of these isolates, we show that interspecies horizontal gene transfer within the
parC
quinolone resistance-determining region is a frequent phenomenon that might contribute to fluoroquinolone resistance.
Repeated Administration of High-Dose Intermittent Rifapentine Reduces Rifapentine and Moxifloxacin Plasma Concentrations
Authors: Dooley Kelly , Flexner Charles , Hackman Judith , Peloquin Charles A. , Nuermberger Eric , Chaisson Richard E. , Dorman Susan E. 
Published: September 2008

ABSTRACT

Moxifloxacin- and rifapentine-based regimens are under investigation for the treatment of tuberculosis. However, rifapentine may induce enzymes that metabolize moxifloxacin, resulting in decreased moxifloxacin concentrations. In this phase I, two-period, sequential-design study, 13 subjects received 400 mg moxifloxacin daily for 4 days followed by daily moxifloxacin coadministered with 900 mg rifapentine thrice weekly. Pharmacokinetic analyses were performed after the 4th and 19th doses of moxifloxacin and after the 1st and 7th doses of rifapentine. For moxifloxacin, the mean area under the concentration-time curve from 0 to 24 h (AUC
0-24
) decreased by 17.2% (
P
= 0.0006) when the drug was coadministered with rifapentine, and the mean half-life (
t
1/2
) decreased from 11.1 to 8.9 h (
P
= 0.0033). For rifapentine, the mean AUC
0-48
after seven thrice-weekly doses decreased by 20.3% (
P
= 0.0035) compared to the AUC
0-48
after the first dose, and the mean
t
1/2
decreased from 18.5 to 14.8 h (
P
= 0.0004). The AUC
0-48
for the 25-desacetyl-rifapentine metabolite diminished 21%. Two days after completing the study drugs, one subject developed a fever and hepatitis, and another developed a flu-like illness with a rash. In conclusion, rifapentine modestly reduced moxifloxacin concentrations. Changes consistent with rifapentine autoinduction of metabolism were seen. Adverse reactions in two subjects may have represented rifamycin hypersensitivity syndrome, although some features were atypical.
Hitchhiking and Selective Sweeps of
Plasmodium falciparum
Sulfadoxine and Pyrimethamine Resistance Alleles in a Population from Central Africa
Authors: McCollum Andrea M. , Basco Leonardo K. , Tahar Rachida , Udhayakumar Venkatachalam , Escalante Ananias A. 
Published: September 2008

ABSTRACT

Sulfadoxine-pyrimethamine (SP) resistance in
Plasmodium falciparum
is encoded by a number of mutations in the dihydrofolate reductase (
dhfr
) and dihydropteroate synthetase (
dhps
) genes. Here, we have characterized point mutations in
dhfr
and
dhps
and microsatellite loci around
dhfr
on chromosome 4 and
dhps
on chromosome 8 as well as neutral markers on chromosomes 2 and 3 in 332 samples from Yaoundé, Cameroon. The triple mutant
dhfr
haplotype that originated in Southeast Asia is the most predominant in this sample set, but we also find additional independent haplotypes at low frequency and an incipient process of genetic differentiation among alleles of Southeast Asian origin. As reported for other African populations, we find evidence of a selective sweep for resistant
dhfr
mutants in this Cameroonian population due to drug selection. Although we find evidence for a selective sweep in
dhps
mutants associated with SP resistance, the dynamics of
dhps
mutants appear different than those observed for
dhfr
mutants. Overall, our results yield support for the use of microsatellite markers to track resistant parasites; however, the detection of resistant
dhfr
alleles in low frequency, the evidence of divergence among
dhfr
alleles that share a common evolutionary origin, and the distinct dynamics of resistant
dhps
alleles emphasize the importance of comprehensive, population-based investigations to evaluate the effects of drug selection on parasite populations.
Assessing the Efficacy of Cidofovir against Herpesvirus-Induced Genital Lesions in Goats Using Different Therapeutic Regimens
Authors: Tempesta M. , Crescenzo G. , Camero M. , Bellacicco A. L. , Tarsitano E. , Decaro N. , Neyts J. , Martella V. , Buonavoglia C. 
Published: September 2008

ABSTRACTCaprine herpesvirus 1 (CpHV-1) infection in goats induces genital vesicular-ulcerative lesions that strictly resemble those produced by human herpesvirus 2 in humans. In previous studies, the potent inhibition of CpHV-1 by cidofovir was demonstrated. Cidofovir antiherpetic activity was evaluated in goats infected experimentally by the vaginal route with CpHV-1 and then treated locally at different times after infection. The administration of 1% cidofovir cream onto vaginal mucosa was able to prevent the onset of genital lesions and to decrease significantly the titers of the virus shed by the infected animals, notably in the groups treated shortly after infection (24 and 48 h). The efficacy of cidofovir against caprine herpesvirus infection was higher when the treatment was started shortly after infection than when lesions were already present and advanced. Herpesvirus genital infection of goats is a useful animal model to study the activity of antiviral drugs against human herpesvirus infections.
KHM-1, a Novel Plasmid-Mediated Metallo-β-Lactamase from a
Citrobacter freundii
Clinical Isolate
Authors: Sekiguchi Jun-ichiro , Morita Koji , Kitao Tomoe , Watanabe Noboru , Okazaki Mitsuhiro , Miyoshi-Akiyama Tohru , Kanamori Masato , Kirikae Teruo 
Published: September 2008

ABSTRACT

A novel gene,
bla
KHM-1
, encoding a metallo-β-lactamase, KHM-1, was cloned from a clinical isolate of
Citrobacter freundii
resistant to most β-lactam antibiotics.
Escherichia coli
expressing
bla
KHM-1
was resistant to all broad-spectrum β-lactams except for monobactams and showed reduced susceptibility to carbapenems. Recombinant KHM-1 exhibited EDTA-inhibitable hydrolytic activity against most β-lactams, with an overall preference for cephalosporins.
In Vitro Activities of ER-119884 and E5700, Two Potent Squalene Synthase Inhibitors, against
Leishmania amazonensis
: Antiproliferative, Biochemical, and Ultrastructural Effects
Authors: Fernandes Rodrigues Juliany Cola , Concepcion Juan Luis , Rodrigues Carlos , Caldera Aura , Urbina Julio A. , de Souza Wanderley 
Published: September 2008

ABSTRACT

ER-119884 and E5700, novel arylquinuclidine derivatives developed as cholesterol-lowering agents, were potent in vitro growth inhibitors of both proliferative stages of
Leishmania amazonensis
, the main causative agent of cutaneous leishmaniasis in South America, with the 50% inhibitory concentrations (IC
50
s) being in the low-nanomolar to subnanomolar range. The compounds were very potent noncompetitive inhibitors of native
L. amazonensis
squalene synthase (SQS), with inhibition constants also being in the nanomolar to subnanomolar range. Growth inhibition was strictly associated with the depletion of the parasite's main endogenous sterols and the concomitant accumulation of exogenous cholesterol. Using electron microscopy, we identified the intracellular structures affected by the compounds. A large number of lipid inclusions displaying different shapes and electron densities were observed after treatment with both SQS inhibitors, and these inclusions were associated with an intense disorganization of the membrane that surrounds the cell body and flagellum, as well as the endoplasmic reticulum and the Golgi complex. Cells treated with ER-119884 but not those treated with E5700 had an altered cytoskeleton organization due to an abnormal distribution of tubulin, and many were arrested at cytokinesis. A prominent contractile vacuole and a phenotype typical of programmed cell death were frequently found in drug-treated cells. The selectivity of the drugs was demonstrated with the JC-1 mitochondrial fluorescent label and by trypan blue exclusion tests with macrophages, which showed that the IC
50
s against the host cells were 4 to 5 orders of magnitude greater that those against the intracellular parasites. Taken together, our results show that ER-119884 and E5700 are unusually potent and selective inhibitors of the growth of
Leishmania amazonensis
, probably because of their inhibitory effects on de novo sterol biosynthesis at the level of SQS, but some of our observations indicate that ER-119884 may also interfere with other cellular processes.
Vaccination of Mice with a Yop Translocon Complex Elicits Antibodies That Are Protective against Infection with F1
−
Yersinia pestis
Authors: Ivanov Maya I. , Noel Betty L. , Rampersaud Ryan , Mena Patricio , Benach Jorge L. , Bliska James B. 
Published: September 2008

ABSTRACT

Yersinia pestis
, the bacterial agent of plague, secretes several proteins important for pathogenesis or host protection. The F1 protein forms a capsule on the bacterial cell surface and is a well-characterized protective antigen but is not essential for virulence. A type III secretion system that is essential for virulence exports Yop proteins, which function as antiphagocytic or anti-inflammatory factors. Yop effectors (e.g., YopE) are delivered across the host cell plasma membrane by a translocon, composed of YopB and YopD. Complexes of YopB, YopD, and YopE (BDE) secreted by
Yersinia pseudotuberculosis
were purified by affinity chromatography and used as immunogens to determine if antibodies to the translocon could provide protection against
Y. pestis
in mice. Mice vaccinated with BDE generated high-titer immunoglobulin G antibodies specific for BDE, as shown by enzyme-linked immunosorbent assay and immunoblotting, and were protected against lethal intravenous challenge with F1
−
but not F1
+
Y. pestis.
Mice passively immunized with anti-BDE serum were protected from lethal challenge with F1
−
Y. pestis
. The YopB protein or a complex of YopB and YopD (BD) was purified and determined by vaccination to be immunogenic in mice. Mice actively vaccinated with BD or passively vaccinated with anti-BD serum were protected against lethal challenge with F1
−
Y. pestis
. These results indicate that anti-translocon antibodies can be used as immunotherapy to treat infections by F1
−
Y. pestis
.
Dynamin-2-Dependent Targeting ofMannheimia haemolyticaLeukotoxin to Mitochondrial Cyclophilin D in Bovine Lymphoblastoid Cells
Authors: Atapattu Dhammika N. , Albrecht Ralph M. , McClenahan David J. , Czuprynski Charles J. 
Published: September 2008

ABSTRACTExotoxins which belong to the family containing the RTX toxins (repeats in toxin) contribute to a variety of important human and animal diseases. One example of such a toxin is the potent leukotoxin (LKT) produced by the bovine respiratory pathogenMannheimia haemolytica.LKT binds to CD18, resulting in the death of bovine leukocytes. In this study, we showed that internalized LKT binds to the outer mitochondrial membrane, which results in the release of cytochromecand collapse of the mitochondrial membrane potential (ψm). Incubation of bovine lymphoblastoid cells (BL-3 cells) with the mitochondrial membrane-stabilizing agent cyclosporine (CSA) reduced LKT-mediated cytotoxicity, cytochromecrelease, and collapse of the ψm. Coimmunoprecipitation and intracellular binding studies suggested that LKT binds to the mitochondrial matrix protein cyclophilin D. We also demonstrated that LKT mobilizes the vesicle scission protein dynamin-2 from mitochondria to the cell membrane. Incubation with CSA depleted mitochondrial dynamin-2 in BL-3 cells, making it unavailable for vesicle scission and LKT internalization. The results of this study show that LKT trafficking and LKT-mediated cell death involve dynamin-2 and cyclophilin D, in a process that can be prevented by the mitochondrial membrane-protecting function of CSA.
Functional Mapping of YadA- and Ail-Mediated Binding of Human Factor H toYersinia enterocoliticaSerotype O:3
Authors: Biedzka-Sarek Marta , Salmenlinna Saara , Gruber Markus , Lupas Andrei N. , Meri Seppo , Skurnik Mikael 
Published: September 2008

ABSTRACTYersinia enterocoliticais an enteric pathogen that exploits diverse means to survive in the human host. UponY. enterocoliticaentry into the human host, bacteria sense and respond to variety of signals, one of which is the temperature. Temperature in particular has a profound impact onY. enterocoliticagene expression, as most of its virulence factors are expressed exclusively at 37°C. These include two outer membrane proteins, YadA and Ail, that function as adhesins and complement resistance (CR) factors. Both YadA and Ail bind the functionally active complement alternative pathway regulator factor H (FH). In this study, we characterized regions on both proteins involved in CR and the interaction with FH. Twenty-eight mutants having short (7 to 41 amino acids) internal deletions within the neck and stalk of YadA and two complement-sensitive site-directed Ail mutants were constructed to map the CR and FH binding regions of YadA and Ail. Functional analysis of the YadA mutants revealed that the stalk of YadA is required for both CR and FH binding and that FH appears to target several conformational and discontinuous sites of the YadA stalk. On the other hand, the complement-sensitive Ail mutants were not affected in FH binding. Our results also suggested that Ail- and YadA-mediated CR does not depend solely on FH binding.
Bacterial Conjugation in the Cytoplasm of Mouse Cells
Authors: Lim Yin Mei , de Groof Ad J. C. , Bhattacharjee Mrinal K. , Figurski David H. , Schon Eric A. 
Published: September 2008

ABSTRACT

Intracellular pathogenic organisms such as salmonellae and shigellae are able to evade the effects of many antibiotics because the drugs are not able to penetrate the plasma membrane. In addition, these bacteria may be able to transfer genes within cells while protected from the action of drugs. The primary mode by which virulence and antibiotic resistance genes are spread is bacterial conjugation. Salmonellae have been shown to be competent for conjugation in the vacuoles of cultured mammalian cells. We now show that the conjugation machinery is also functional in the mammalian cytosol. Specially constructed
Escherichia coli
strains expressing
Shigella flexneri
plasmid and chromosomal virulence factors for escape from vacuoles and synthesizing the invasin protein from
Yersinia pseudotuberculosis
to enhance cellular entry were able to enter 3T3 cells and escape from the phagocytic vacuole. One bacterial strain (the donor) of each pair to be introduced sequentially into mammalian cells had a conjugative plasmid. We found that this plasmid could be transferred at high frequency. Conjugation in the cytoplasm of cells may well be a general phenomenon.
Epithelial and Mesenchymal Cells in the Bovine Colonic Mucosa Differ in Their Responsiveness toEscherichia coliShiga Toxin 1
Authors: Stamm Ivonne , Mohr Melanie , Bridger Philip S. , Schröpfer Elmar , König Matthias , Stoffregen William C. , Dean-Nystrom Evelyn A. , Baljer Georg , Menge Christian 
Published: September 2008

ABSTRACTBovine colonic crypt cells express CD77 molecules that potentially act as receptors for Shiga toxins (Stx). The implication of this finding for the intestinal colonization of cattle by human pathogenic Stx-producingEscherichia coli(STEC) remains undefined. We used flow cytometric and real-time PCR analyses of primary cultures of colonic crypt cells to evaluate cell viability, CD77 expression, and gene transcription in the presence and absence of purified Stx1. A subset of cultured epithelial cells had Stx receptors which were located mainly intracellularly, with a perinuclear distribution, and were resistant to Stx1-induced apoptosis and Stx1 effects on chemokine expression patterns. In contrast, a population of vimentin-positive cells, i.e., mesenchymal/nonepithelial cells that had high numbers of Stx receptors on their surface, was depleted from the cultures by Stx1. In situ, CD77+cells were located in the lamina propria of the bovine colon by using immunofluorescence staining. A newly established vimentin-positive crypt cell line with high CD77 expression resisted the cytolethal effect of Stx1 but responded to Stx1 with a significant increase in interleukin-8 (IL-8), GRO-α, MCP-1, and RANTES mRNA. Combined stimulation with lipopolysaccharide and Stx1 increased IL-10 mRNA. Our results show that bovine colonic crypt cells of epithelial origin are resistant to both the cytotoxic and modulatory effects of Stx1. In contrast, some mucosal mesenchymal cells, preliminarily characterized as mucosal macrophages, are Stx1-responsive cells that may participate in the interaction of STEC with the bovine intestinal mucosa.
Conditions That Diminish Myeloid-Derived Suppressor Cell Activities Stimulate Cross-Protective Immunity
Authors: Heithoff Douglas M. , Enioutina Elena Y. , Bareyan Diana , Daynes Raymond A. , Mahan Michael J. 
Published: September 2008

ABSTRACTImmunity conferred by conventional vaccines is restricted to a narrow range of closely related strains, highlighting the unmet medical need for the development of vaccines that elicit protection against multiple pathogenic serotypes. Here we show that aSalmonellabivalent vaccine comprised of strains that lack and overproduce DNA adenine methylase (Dam) conferred cross-protective immunity to salmonella clinical isolates of human and animal origin. Protective immunity directly correlated with increased levels of cross-reactive opsonizing antibodies and memory T cells and a diminished expansion of myeloid-derived suppressor cells (MDSCs) that are responsible for the immune suppression linked to several conditions of host stress, including chronic microbial infections, traumatic insults, and many forms of cancer. Further, aged mice contained increased numbers of MDSCs and were more susceptible toSalmonellainfection than young mice, suggesting a role for these cells in the immune declines associated with the natural aging process. These data suggest that interventions capable of reducing MDSC presence and activities may allow corresponding increases in B- and T-cell stimulation and benefit the ability of immunologically diverse populations to be effectively vaccinated as well as reducing the risk of susceptible individuals to infectious disease.
RegA, an AraC-Like Protein, Is a Global Transcriptional Regulator That Controls Virulence Gene Expression in
Citrobacter rodentium
Authors: Hart Emily , Yang Ji , Tauschek Marija , Kelly Michelle , Wakefield Matthew J. , Frankel Gad , Hartland Elizabeth L. , Robins-Browne Roy M. 
Published: September 2008

ABSTRACT

Citrobacter rodentium
is an attaching and effacing pathogen which causes transmissible colonic hyperplasia in mice. Infection with
C. rodentium
serves as a model for infection of humans with enteropathogenic and enterohemorrhagic
Escherichia coli
. To identify novel colonization factors of
C. rodentium
, we screened a signature-tagged mutant library of
C. rodentium
in mice. One noncolonizing mutant had a single transposon insertion in an open reading frame (ORF) which we designated
regA
because of its homology to genes encoding members of the AraC family of transcriptional regulators. Deletion of
regA
in
C. rodentium
resulted in markedly reduced colonization of the mouse intestine. Examination of
lacZ
transcriptional fusions using promoter regions of known and putative virulence-associated genes of
C. rodentium
revealed that RegA strongly stimulated transcription of two newly identified genes located close to
regA
, which we designated
adcA
and
kfcC
. The cloned
adcA
gene conferred autoaggregation and adherence to mammalian cells to
E. coli
strain DH5α, and a
kfc
mutation led to a reduction in the duration of intestinal colonization, but the
kfc
mutant was far less attenuated than the
regA
mutant. These results indicated that other genes of
C. rodentium
whose expression required activation by RegA were required for colonization. Microarray analysis revealed a number of RegA-regulated ORFs encoding proteins homologous to known colonization factors. Transcription of these putative virulence determinants was activated by RegA only in the presence of sodium bicarbonate. Taken together, these results show that RegA is a global regulator of virulence in
C. rodentium
which activates factors that are required for intestinal colonization.