bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Interferon, Ribavirin, and Iminosugar Derivatives on Cells Persistently Infected with Noncytopathic Bovine Viral Diarrhea Virus
Authors: Durantel David , Carrouée-Durantel Sandra , Branza-Nichita Norica , Dwek Raymond A. , Zitzmann Nicole 
Published: January 2004

ABSTRACT
Persistent infection with hepatitis C virus (HCV) is a major cause of chronic hepatitis in humans. In chronic carriers, the viral infection induces liver damage that predisposes the patient for cirrhosis and can lead to hepatocellular carcinoma. Current chemotherapies are limited to alpha interferon (IFN-α) used either alone or in combination with ribavirin (RBV). In addition to its limited efficacy, this treatment is frequently poorly tolerated because of its side effects. The urgently needed development of new drugs is made difficult by the lack of an in vitro or in vivo infectivity model, and no cell line has been found so far to reliably and reproducibly support HCV infection. For this reason, the closely related pestivirus bovine viral diarrhea virus (BVDV) has sometimes been used as a surrogate in vitro infectivity model. In this study we used an MDBK cell line persistently infected with noncytopathic BVDV to assess the antiviral effect of IFN-α and RBV, the two drugs currently in clinical use against HCV. The same system was then used to evaluate the potential of two classes of iminosugar derivates to clear noncytopathic BVDV infection from MDBK cells. We show that treatment with long-alkyl-chain deoxynojirimycin derivatives, which are inhibitors of the endoplasmic reticulum (ER)-resident α-glucosidases, can greatly reduce the amount of secreted enveloped viral RNA. Long-alkyl-chain deoxygalactonojirimycin derivatives, which do not inhibit ER α-glucosidases, were less potent but still more effective in this system than IFN-α or ribavirin.
Genetic Analysis and Complete Primary Structure of Microcin L
Authors: Pons Anne-Marie , Delalande François , Duarte Mariela , Benoit Stéphanie , Lanneluc Isabelle , Sablé Sophie , Van Dorsselaer Alain , Cottenceau Gilles 
Published: January 2004

ABSTRACT

Escherichia coli
LR05, in addition to producing MccB17, J25, and D93, secretes microcin L, a newly discovered microcin that exhibits strong antibacterial activity against related
Enterobacteriaceae
, including
Salmonella enterica
serovars Typhimurium and Enteritidis. Microcin L was purified using a two-step procedure including solid-phase extraction and reverse-phase C
18
high-performance liquid chromatography. A 4,901-bp region of the DNA plasmid of
E. coli
LR05 was sequenced revealing that the microcin L cluster consists of four genes,
mclC
,
mclI
,
mclA
, and
mclB
. The structural gene
mclC
encoded a 105-amino-acid precursor with a 15-amino-acid N-terminal extension ending with a Gly-Ala motif upstream of the cleavage site. This motif is typical of the class II microcins and other gram-positive bacteriocins exported by ABC transporters. The
mclI
immunity gene was identified upstream of the
mclC
gene and encodes a 51-amino-acid protein with two potential transmembrane domains. Located on the reverse strand, two genes,
mclA
and
mclB
, encoded the proteins MclA and MclB, respectively. They bear strong relatedness with the ABC transporter proteins and accessory factors involved in the secretion of microcins H47, V, E492, and 24. The microcin L genetic system resembles the genetic organization of MccV. Furthermore the MccL primary structure has been determined. It is a 90-amino-acid peptide of 8,884 Da with two disulfide bridges. The N-terminal region has significant homologies with several gram-positive bacteriocins. The C-terminal 32-amino-acid sequence is 87.5% identical to that of MccV. Together, these results strongly indicate that microcin L is a gram-negative class II microcin.
Streptomyces clavuligerus
Has a Second Copy of the Proclavaminate Amidinohydrolase Gene
Authors: Jensen Susan E. , Wong Annie , Griffin Alison , Barton Barry 
Published: January 2004

ABSTRACT

Past genetic studies have indicated that the genes encoding early enzymes of clavulanic acid biosynthesis may be duplicated in
Streptomyces clavuligerus
. We observed cross-hybridizing bands upon Southern analyses of proclavaminate amidinohydrolase (
pah
)-defective mutant strains of
S. clavuligerus
screened with a
pah
-specific probe. The DNA fragment responsible for this cross hybridization was cloned and sequenced and shown to encode a second copy of the
pah
gene. The new
pah
gene (
pah1
) was 1,056 bp in length, and its sequence was 72% identical to that of the original
pah
gene (
pah2
). Disruption mutants with defects in
pah1
showed no significant effects on production of clavulanic acid or any of the clavam metabolites with stereochemistries opposite that of clavulanic acid (
5S
clavams) produced by
S. clavuligerus
when they were grown on starch asparagine or soy medium. However, double mutants with defects in both
pah1
and
pah2
were defective in the production of both clavulanic acid and all of the
5S
clavam metabolites.
Pharmacokinetics of Total and Unbound Ertapenem in Healthy Elderly Subjects
Authors: Musson D. G. , Majumdar A. , Holland S. , Birk K. , Xi L. , Mistry G. , Sciberras D. , Muckow J. , Deutsch P. , Rogers J. D. 
Published: January 2004

ABSTRACT

Ertapenem is a new once-a-day parenteral carbapenem antimicrobial agent. The pharmacokinetics of unbound and total concentrations of ertapenem in plasma were investigated in elderly subjects and compared with historical data from young adults. In a single- and multiple-dose study, healthy elderly males and females (
n
= 14) 65 years old or older were given a 1-g intravenous (i.v.) dose once daily for 7 days. Plasma and urine samples collected for 24 h on days 1 and 7 following administration of the 1-g doses were analyzed by reversed-phase high-performance liquid chromatography. Areas under the concentration-time curve from 0 h to infinity (AUC
0-∞
) for elderly females and males were similar following administration of 1-g single i.v. doses, and thus, the genders were pooled in subsequent analyses. Concentrations in plasma and the half-life of ertapenem were generally higher and longer, respectively, in elderly subjects than in young adults. The mean AUC
0-∞
of total ertapenem in the elderly was 39% higher than that in young subjects following administration of a 1-g dose. The differences were slightly greater for the mean AUC
0-∞
of unbound ertapenem (71%). The unbound fraction of ertapenem in elderly subjects (∼5 to 11%) was generally greater than that in young adults (∼5 to 8%). As in young adults, ertapenem did not accumulate upon multiple dosing in the elderly. The pharmacokinetics of ertapenem in elderly subjects, while slightly different from those in young adults, do not require a dosage adjustment for elderly patients.
New Class of Bacterial Phenylalanyl-tRNA Synthetase Inhibitors with High Potency and Broad-Spectrum Activity
Authors: Beyer Dieter , Kroll Hein-Peter , Endermann Rainer , Schiffer Guido , Siegel Stephan , Bauser Marcus , Pohlmann Jens , Brands Michael , Ziegelbauer Karl , Haebich Dieter , Eymann Christine , Brötz-Oesterhelt Heike 
Published: January 2004

ABSTRACT

Phenylalanyl (Phe)-tRNA synthetase (Phe-RS) is an essential enzyme which catalyzes the transfer of phenylalanine to the Phe-specific transfer RNA (tRNA
Phe
), a key step in protein biosynthesis. Phenyl-thiazolylurea-sulfonamides were identified as a novel class of potent inhibitors of bacterial Phe-RS by high-throughput screening and chemical variation of the screening hit. The compounds inhibit Phe-RS of
Escherichia coli
,
Haemophilus influenzae
,
Streptococcus pneumoniae
, and
Staphylococcus aureus
, with 50% inhibitory concentrations in the nanomolar range. Enzyme kinetic measurements demonstrated that the compounds bind competitively with respect to the natural substrate Phe. All derivatives are highly selective for the bacterial Phe-RS versus the corresponding mammalian cytoplasmic and human mitochondrial enzymes. Phenyl-thiazolylurea-sulfonamides displayed good in vitro activity against
Staphylococcus
,
Streptococcus
,
Haemophilus
, and
Moraxella
strains, reaching MICs below 1 μg/ml. The antibacterial activity was partly antagonized by increasing concentrations of Phe in the culture broth in accordance with the competitive binding mode. Further evidence that inhibition of tRNA
Phe
charging is the antibacterial principle of this compound class was obtained by proteome analysis of
Bacillus subtilis
. Here, the phenyl-thiazolylurea-sulfonamides induced a protein pattern indicative of the stringent response. In addition, an
E. coli
strain carrying a
relA
mutation and defective in stringent response was more susceptible than its isogenic
relA
+
parent strain. In vivo efficacy was investigated in a murine
S. aureus
sepsis model and a
S. pneumoniae
sepsis model in rats. Treatment with the phenyl-thiazolylurea-sulfonamides reduced the bacterial titer in various organs by up to 3 log units, supporting the potential value of Phe-RS as a target in antibacterial therapy.
Epidemiology of Conjugative Plasmid-Mediated AmpC β-Lactamases in the United States
Authors: Alvarez M. , Tran J. H. , Chow N. , Jacoby G. A. 
Published: January 2004

ABSTRACT

A sample of 752 resistant
Klebsiella pneumoniae
,
Klebsiella oxytoca
, and
Escherichia coli
strains from 70 sites in 25 U.S. states and the District of Columbia was examined for transmissibility of resistance to ceftazidime and the nature of the plasmid-mediated β-lactamase involved. Fifty-nine percent of the
K. pneumoniae
, 24% of the
K. oxytoca
, and 44% of the
E. coli
isolates transferred resistance to ceftazidime. Plasmids encoding AmpC-type β-lactamase were found in 8.5% of the
K. pneumoniae
samples, 6.9% of the
K. oxytoca
samples, and 4% of the
E. coli
samples, at 20 of the 70 sites and in 10 of the 25 states. ACT-1 β-lactamase was found at eight sites, four of which were near New York City, where the ACT-1 enzyme was first discovered; ACT-1 β-lactamase was also found in Massachusetts, Pennsylvania, and Virginia. FOX-5 β-lactamase was also found at eight sites, mainly in southeastern states but also in New York. Two
E. coli
strains produced CMY-2, and one
K. pneumoniae
strain produced DHA-1 β-lactamase. Pulsed-field gel electrophoresis and plasmid analysis suggested that AmpC-mediated resistance spread both by strain and plasmid dissemination. All AmpC β-lactamase-containing isolates were resistant to cefoxitin, but so were 11% of strains containing transmissible SHV- and TEM-type extended-spectrum β-lactamases. A β-lactamase inhibitor test was helpful in distinguishing the two types of resistance but was not definitive since 24% of clinical isolates producing AmpC β-lactamase had a positive response to clavulanic acid. Coexistence of AmpC and extended-spectrum β-lactamases was the main reason for these discrepancies. Plasmid-mediated AmpC-type enzymes are thus responsible for an appreciable fraction of resistance in clinical isolates of
Klebsiella
spp. and
E. coli
, are disseminated around the United States, and are not so easily distinguished from other enzymes that mediate resistance to oxyimino-β-lactams.
Duplex Real-Time PCR Assay for Rapid Detection of Ampicillin-Resistant
Enterococcus faecium
Authors: Mohn Stein Christian , Ulvik Arve , Jureen Roland , Willems Rob J. L. , Top Janetta , Leavis Helen , Harthug Stig , Langeland Nina 
Published: January 2004

ABSTRACT

Rapid and accurate identification of carriers of resistant microorganisms is an important aspect of efficient infection control in hospitals. Traditional identification methods of antibiotic-resistant bacteria usually take at least 3 to 4 days after sampling. A duplex real-time PCR assay was developed for rapid detection of ampicillin-resistant
Enterococcus faecium
(ARE). Primers and probes that are used in this assay specifically detected the
d-
Ala
-d-
Ala ligase gene of
E. faecium
and the modified penicillin-binding protein 5 gene (
pbp5
) carrying the Glu-to-Val substitution at position 629 (Val-629) in a set of 129 tested
E. faecium
strains with known
pbp5
sequence. Presence of the Val-629 in the strain set from 11 different countries was highly correlated with ampicillin resistance. In a screening of hospitalized patients, the real-time PCR assay yielded a sensitivity and a specificity for the detection of ARE colonization of 95% and 100%, respectively. The results were obtained 4 h after samples were harvested from overnight broth of rectal swab samples, identifying both species and the resistance marker mutation in
pbp5
. This novel assay reliably identifies ARE 2 to 3 days more quickly than traditional culture methods, thereby increasing laboratory throughput, making it useful for rectal screening of ARE. The assay demonstrates the advantages of real-time PCR for detection of nosocomial pathogens.
Differential Gene Expression in Auristatin PHE-Treated
Cryptococcus neoformans
Authors: Woyke Tanja , Berens Michael E. , Hoelzinger Dominique B. , Pettit George R. , Winkelmann Günther , Pettit Robin K. 
Published: January 2004

ABSTRACT

The antifungal pentapeptide auristatin PHE was recently shown to interfere with microtubule dynamics and nuclear and cellular division in the opportunistic pathogen
Cryptococcus neoformans.
To gain a broader understanding of the cellular response of
C. neoformans
to auristatin PHE, mRNA differential display (DD) and reverse transcriptase PCR (RT-PCR) were applied. Examination of approximately 60% of the cell transcriptome from cells treated with 1.5 times the MIC (7.89 μM) of auristatin PHE for 90 min revealed 29 transcript expression differences between control and drug-treated populations. Differential expression of seven of the transcripts was confirmed by RT-PCR, as was drug-dependent modulation of an additional seven transcripts by RT-PCR only. Among genes found to be differentially expressed were those encoding proteins involved in transport, cell cycle regulation, signal transduction, cell stress, DNA repair, nucleotide metabolism, and capsule production. For example,
RHO1
and an open reading frame (ORF) encoding a protein with 91% similarity to the
Schizophyllum commune
14-3-3 protein, both involved in cell cycle regulation, were down-regulated, as was the gene encoding the multidrug efflux pump Afr1p. An ORF encoding a protein with 57% identity to the heat shock protein HSP104 in
Pleurotus sajor
-
caju
was up-regulated. Also, three transcripts of unknown function were responsive to auristatin PHE, which may eventually contribute to the elucidation of the function of their gene products. Further study of these differentially expressed genes and expression of their corresponding proteins are warranted to evaluate how they may be involved in the mechanism of action of auristatin PHE. This information may also contribute to an explanation of the selectivity of auristatin PHE for
C. neoformans
. This is the first report of drug action using DD in
C. neoformans.
Three-Dimensional Models of Wild-Type and Mutated Forms of Cytochrome P450 14α-Sterol Demethylases from
Aspergillus fumigatus
and
Candida albicans
Provide Insights into Posaconazole Binding
Authors: Xiao Li , Madison Vincent , Chau Andrew S. , Loebenberg David , Palermo Robert E. , McNicholas Paul M. 
Published: January 2004

ABSTRACT

The cytochrome P450 sterol 14α-demethylase enzyme (CYP51) is the target of azole antifungals. Azoles block ergosterol synthesis, and thereby fungal growth, by binding in the active-site cavity of the enzyme and ligating the iron atom of the heme cofactor through a nitrogen atom of the azole. Mutations in and around the CYP51 active site have resulted in azole resistance. In this work, homology models of the CYP51 enzymes from
Aspergillus fumigatus
and
Candida albicans
were constructed based on the X-ray crystal structure of CYP51 from
Mycobacterium tuberculosis
. Using these models, binding modes for voriconazole (VOR), fluconazole (FLZ), itraconazole (ITZ), and posaconazole (POS) were predicted from docking calculations. Previous work had demonstrated that mutations in the vicinity of the heme cofactor had a greater impact on the binding of FLZ and VOR than on the binding of POS and ITZ. Our modeling data suggest that the long side chains of POS and ITZ occupy a specific channel within CYP51 and that this additional interaction, which is not available to VOR and FLZ, serves to stabilize the binding of these azoles to the mutated CYP51 proteins. The model also predicts that mutations that were previously shown to specifically impact POS susceptibility in
A. fumigatus
and
C. albicans
act by interfering with the binding of the long side chain.
Determination of ddATP Levels in Human Immunodeficiency Virus-Infected Patients Treated with Dideoxyinosine
Authors: Le Saint Cecile , Terreux Raphael , Duval Daniele , Durant Jacques , Ettesse Helene , Dellamonica Pierre , Guedj Roger , Vincent Jean Pierre , Cupo Anny 
Published: January 2004

ABSTRACT
Clinical failures of the highly active antiretroviral therapy could result from inefficient intracellular concentrations of antiviral drugs. The determination of drug contents in target cells of each patient would be useful in clinical investigations and trials. The purpose of this work was to quantify the intracellular concentration of ddATP, the active metabolite of dideoxyinosine (ddI), in peripheral blood mononuclear cells (PBMCs) of human immunodeficiency virus (HIV)-infected patients treated with ddI. We have raised antibodies against ddA-citrate, a stable isostere of ddATP selected on the basis of its structural and electronic analogies with ddATP. The anti-ddA-citrate antibodies recognized ddATP and ddA with nanomolar affinities and cross-reacted neither with any of the nucleotide reverse transcriptase inhibitors used in HIV therapy nor with their phosphorylated metabolites. The three phosphorylated metabolites of ddI (ddAMP, ddADP, and ddATP) were purified by anion exchange chromatography and the amount of each metabolite was determined by radioimmunoassay with or without prior phosphatase treatment. The intracellular levels of the three ddI metabolites were measured both in an in vitro model and in PBMCs of HIV-infected patients under ddI treatment. The possibility to measure intracellular levels of ddATP from small blood samples of HIV-infected patients treated with ddI could be exploited to develop individual therapeutic monitoring.
Multiplex PCR Amplimer Conformation Analysis for Rapid Detection of
gyrA
Mutations in Fluoroquinolone-Resistant
Mycobacterium tuberculosis
Clinical Isolates
Authors: Cheng Augustine F. B. , Yew Wing W. , Chan Edward W. C. , Chin Miu L. , Hui Mamie M. M. , Chan Raphael C. Y. 
Published: January 2004

ABSTRACT

A new strategy known as multiplex PCR amplimer conformation was developed for detection of mutation in the
gyrA
gene of 138 clinical isolates of
Mycobacterium tuberculosis
. The method generated a single-stranded and heteroduplex DNA banding pattern of multiplex PCR amplimers of the region of interest that was extremely sensitive to specific mutations, thus enabling much more sensitive and reliable mutation analysis compared to the standard single-stranded conformation polymorphism technique. The genetic profiles of the
gyrA
gene of the 138 isolates as detected by MPAC were confirmed by nucleotide sequencing and were found to correlate strongly with the in vitro susceptibilities of the mutant strains to six fluoroquinolones (ofloxacin, levofloxacin, sparfloxacin, moxifloxacin, gatifloxacin, and sitafloxacin). All 32 isolates that contained
gyrA
mutations exhibited cross-resistance to the six fluoroquinolones (ofloxacin MIC for 90% of strains > 16 mg/liter), although moxifloxacin, gatifloxacin, and sitafloxacin (MIC for 90% of strains ≤ 4 mg/liter) were apparently more active than ofloxacin, levofloxacin, and sparfloxacin (MIC for 90% of strains ≥ 16 mg/liter). All
gyrA
mutations were clustered in codons 90, 91, and 94, and aspartic acid 94 was most frequently mutated. Twenty-three isolates without
gyrA
mutations were also found to exhibit reduced susceptibility to ofloxacin (MIC for 90% of strains = 4 mg/liter), but largely remained susceptible to other drugs (MIC for 90% of strains ≤ 1 mg/liter). Another 83 isolates without mutations were fully susceptible to all six fluoroquinolones (ofloxacin MIC for 90% of strains = 1 mg/liter). In conclusion, high-level phenotypic resistance to fluoroquinolones among
M. tuberculosis
clinical isolates, which appears to be predominantly due to
gyrA
mutations, may be readily detected by genotyping techniques such as multiplex PCR amplimer conformation.
In Vitro Activities of New Antimicrobials against
Nocardia brasiliensis
Authors: Vera-Cabrera Lucio , Gonzalez Eva , Choi Sung H. , Welsh Oliverio 
Published: January 2004

ABSTRACT

The in vitro sensitivities of 30 strains of
Nocardia brasiliensis
to DA-7867, gatifloxacin, moxifloxacin, and BMS-284756 (garenoxacin) were determined using the broth microdilution method. All
N. brasiliensis
strains were sensitive to these antimicrobials. The most active drug in vitro was DA-7867, with a MIC at which 90% of the isolates tested were inhibited of 0.03 μg/ml and a MIC at which 50% of the isolates tested were inhibited of 0.06 μg/ml.
Activities of Cethromycin and Telithromycin against Recent North American Isolates of
Streptococcus pneumoniae
Authors: Jorgensen James H. , Crawford Sharon A. , McElmeel M. Leticia , Whitney Cynthia G. 
Published: January 2004

ABSTRACT

The in vitro activities of two investigational ketolides, cethromycin (formerly ABT-773) and telithromycin, were determined for a selected group of 312
Streptococcus pneumoniae
isolates from a national surveillance program. The MIC of cethromycin at which 50% of the isolates were inhibited was 0.008 μg/ml, and the MIC at which 90% of the isolates were inhibited was 0.06 μg/ml; the corresponding values for telithromycin were ≤0.015 and 0.25 μg/ml, respectively. For six quinupristin-dalfopristin-resistant strains, the cethromycin MICs were 0.25 to 16 μg/ml and the telithromycin MICs were 1 to 4 μg/ml. However, there was only 0.3% resistance to telithromycin.
Replacement of ParC α4 Helix with That of GyrA Increases the Stability and Cytotoxicity of Topoisomerase IV-Quinolone-DNA Ternary Complexes
Authors: Pfeiffer Emily S. , Hiasa Hiroshi 
Published: January 2004

ABSTRACT

Replacement of the α4 helix of ParC with that of GyrA increased the stability of topoisomerase IV-quinolone-DNA ternary complexes. This mutant topoisomerase IV-mediated cell killing was more efficient than topoisomerase IV-mediated cell killing in
Escherichia coli
. Thus, the α4 helix plays critical roles in determining the stability and the cytotoxicity of ternary complexes.
fexA
, a Novel
Staphylococcus lentus
Gene Encoding Resistance to Florfenicol and Chloramphenicol
Authors: Kehrenberg Corinna , Schwarz Stefan 
Published: January 2004

ABSTRACT

The
Staphylococcus lentus
plasmid pSCFS2 carries a novel florfenicol-chloramphenicol resistance gene, designated
fexA
, encoding a protein of 475 amino acids with 14 transmembrane domains. The FexA protein differs from all previously known proteins involved in the efflux of chloramphenicol and florfenicol. Induction of
fexA
expression by chloramphenicol and florfenicol occurs via translational attenuation.
Ribosomal Alterations Contribute to Bacterial Resistance against the Dipeptide Antibiotic TAN 1057
Authors: Limburg E. , Gahlmann R. , Kroll H.-P. , Beyer D. 
Published: January 2004

ABSTRACT

TAN 1057-resistant
Staphylococcus aureus
and
Escherichia coli
strains were selected to elucidate the mechanism of resistance and the mode of action of this dipeptide antibiotic. Cell-free translation with isolated ribosomes and S150 fractions from sensitive and resistant
S. aureus
strains demonstrated that alterations in the ribosomes contribute to the resistance of the bacteria.