bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential Gene Expression in Benznidazole-Resistant
Trypanosoma cruzi
Parasites
Authors: Villarreal Diana , Nirdé Philippe , Hide Mallorie , Barnabé Christian , Tibayrenc Michel 
Published: June 2005

ABSTRACT

We analyzed the differential gene expression among representative
Trypanosoma cruzi
stocks in relation to benznidazole exposures using a random differentially expressed sequences (RADES) technique. Studies were carried out with drug pressure both at the natural susceptibility level of the wild-type parasite (50% inhibitory concentration for the wild type) and at different resistance levels. The pattern of differential gene expression performed with resistant stocks was compared to the population structure of this parasite, established by random amplified polymorphic DNA analysis and multilocus enzyme electrophoresis. A RADES band polymorphism was observed, and over- or underexpression was linked to the resistance level of the stock. The analysis of RADES bands suggested that different products may be involved in benznidazole resistance mechanisms. No significant association was found between phylogenetic clustering and benznidazole susceptibility. Benznidazole resistance may involve several mechanisms, depending on the level of drug exposure.
Phenotyping of Cytomegalovirus Drug Resistance Mutations by Using Recombinant Viruses Incorporating a Reporter Gene
Authors: Chou Sunwen , Van Wechel Laura C. , Lichy Heather M. , Marousek Gail I. 
Published: June 2005

ABSTRACT

A new recombinant phenotyping method was developed for the analysis of drug resistance mutations in human cytomegalovirus (CMV). CMV strain T2211 was derived from strain AD169 by inserting unique restriction sites and a secreted alkaline phosphatase (SEAP) reporter gene for rapid viral quantitation. Specific viral UL97 and
pol
gene mutations were transferred by recombination into T2211, and their drug resistance phenotypes (for ganciclovir, foscarnet, or cidofovir) were determined by the drug concentrations required to reduce supernatant SEAP activity by 50% (IC
50
). Changes in the IC
50
conferred by the mutations tested (UL97 M460V, C592G, A594V, and L595S and
pol
del981-2) were similar to those previously reported in marker transfer and conventional plaque reduction assays. The combination of UL97 C592G and
pol
del981-2 conferred much higher ganciclovir resistance than either mutation alone. The UL97 polymorphism D605E had no measurable effect on ganciclovir susceptibility, alone or in combination with common UL97 resistance mutations. Transfer into strain T2211 facilitates the phenotyping of newly observed mutations, combinations of mutations, and clinical CMV sequences without an accompanying viral isolate.
New
lnu
(C) Gene Conferring Resistance to Lincomycin by Nucleotidylation in
Streptococcus agalactiae
UCN36
Authors: Achard Adeline , Villers Corinne , Pichereau Vianney , Leclercq Roland 
Published: June 2005

ABSTRACT

Streptococcus agalactiae
UCN36 was resistant to lincomycin (MIC = 16 μg/ml) but susceptible to clindamycin (MIC = 0.12 μg/ml) and erythromycin (MIC = 0.06 μg/ml). A 4-kb HindIII fragment was cloned from
S. agalactiae
UCN36 total DNA on plasmid pUC18 and introduced into
Escherichia coli
AG100A, where it conferred resistance to lincomycin. The sequence analysis of the fragment showed the presence of a 1,724-bp element delineated by imperfect inverted repeats (22 of 25 bp) and inserted in the operon for capsular synthesis of
S. agalactiae
UCN36. This element carried two open reading frames (ORF). The deduced amino acid sequence of the upstream ORF displayed similarity with transposases from anaerobes and IS
1
. The downstream ORF,
lnu
(C), encoded a 164-amino-acid protein with 26% to 27% identity with the LnuA
N2
, LnuA, and LnuA′ lincosamide nucleotidyltransferases reported for
Bacteroides
and
Staphylococcus
, respectively. Crude lysates of
E. coli
AG100A containing the cloned
lnu
(C) gene inactivated lincomycin and clindamycin in the presence of ATP and MgCl
2
. Mass spectrometry experiments demonstrated that the LnuC enzyme catalyzed adenylylation of lincomycin.
Antiviral Effect of Oral Administration of Tenofovir Disoproxil Fumarate in Woodchucks with Chronic Woodchuck Hepatitis Virus Infection
Authors: Menne Stephan , Cote Paul J. , Korba Brent E. , Butler Scott D. , George Andrea L. , Tochkov Ilia A. , Delaney William E. , Xiong Shelly , Gerin John L. , Tennant Bud C. 
Published: June 2005

ABSTRACTTenofovir disoproxil fumarate (TDF) is a nucleotide analogue approved for treatment of human immunodeficiency virus (HIV) infection. TDF also has been shown in vitro to inhibit replication of wild-type hepatitis B virus (HBV) and lamivudine-resistant HBV mutants and to inhibit lamivudine-resistant HBV in patients and HBV in patients coinfected with the HIV. Data on the in vivo efficacy of TDF against wild-type virus in non-HIV-coinfected or lamivudine-naïve chronic HBV-infected patients are lacking in the published literature. The antiviral effect of oral administration of TDF against chronic woodchuck hepatitis virus (WHV) infection, an established and predictive animal model for antiviral therapy, was evaluated in a placebo-controlled, dose-ranging study (doses, 0.5 to 15.0 mg/kg of body weight/day). Four weeks of once-daily treatment with TDF doses of 0.5, 1.5, or 5.0 mg/kg/day reduced serum WHV viremia significantly (0.2 to 1.5 log reduction from pretreatment level). No effects on the levels of anti-WHV core and anti-WHV surface antibodies in serum or on the concentrations of WHV RNA or WHV antigens in the liver of treated woodchucks were observed. Individual TDF-treated woodchucks demonstrated transient declines in WHV surface antigen serum antigenemia and, characteristically, these woodchucks also had transient declines in serum WHV viremia, intrahepatic WHV replication, and hepatic expression of WHV antigens. No evidence of toxicity was observed in any of the TDF-treated woodchucks. Following drug withdrawal there was prompt recrudescence of WHV viremia to pretreatment levels. It was concluded that oral administration of TDF for 4 weeks was safe and effective in the woodchuck model of chronic HBV infection.
Antibacterial Properties of Some Cyclic Organobismuth(III) Compounds
Authors: Kotani Toshiaki , Nagai Daisuke , Asahi Kensuke , Suzuki Hitomi , Yamao Fumiaki , Kataoka Nobumasa , Yagura Tatsuo 
Published: June 2005

ABSTRACTBismuth compounds are known for their low levels of toxicity in mammals, and various types of bismuth salts have been used to treat medical disorders. As part of our program to probe this aspect of bismuth chemistry, cyclic organobismuth compounds 1 to 8 bearing a nitrogen or sulfur atom as an additional ring member have been synthesized, and their antimicrobial activities against five standard strains of gram-negative and gram-positive bacteria were assessed. The eight-membered-ring compounds, compounds 1 to 3, exhibited MICs of less than 0.5 μg/ml againstStaphylococcus aureusand were more active than the six-membered ones, compounds 5 to 8 (MICs, 4.0 to 16 μg/ml). The gram-positive bacteria (Staphylococcus aureus,Bacillus subtilis, andEnterococcus faecalis) were more susceptible to both types of ring compounds than the gram-negative ones (Escherichia coliandPseudomonas aeruginosa). Treatment with polymyxin B nonapeptide increased the susceptibility ofE. colito cyclic organobismuth compounds, indicating the low permeability of the outer membrane of gram-negative bacteria to the compounds. Compound 1 also had activity against methicillin-resistantS. aureus, which had an MIC for 90% of the hospital stock strains of 1.25 μg/ml. The killing curves forS. aureustreated with compound 1 or 3 revealed a static effect at a low dose (2× the MIC). However, whenS. aureuswas treated with 10× the MIC of compound 1 or 3, there was an approximately 3-log reduction in the viable cell number after 48 h of treatment. Electron microscopic inspection demonstrated a considerable increase in the size ofS. aureusand the proportion of cells undergoing cell division after treatment with compound 1 at 0.5× the MIC.
Short-Course Gentamicin in Combination with Daptomycin or Vancomycin against
Staphylococcus aureus
in an In Vitro Pharmacodynamic Model with Simulated Endocardial Vegetations
Authors: Tsuji Brian T. , Rybak Michael J. 
Published: June 2005

ABSTRACT

The ability to maximize bactericidal activity while minimizing toxicity is a therapeutic goal in the treatment of infective endocarditis. We evaluated the impact of administering short-course regimens of gentamicin in combination with daptomycin or vancomycin against one methicillin-susceptible (MSSA 1199) and one methicillin-resistant (MRSA 494)
Staphylococcus aureus
isolate using an in vitro pharmacodynamic model with simulated endocardial vegetations over 96 h. Human therapeutic dosing regimens for daptomycin (6 and 8 mg/kg of body weight), vancomycin, and gentamicin were simulated. Short-course combination regimens involving gentamicin were administered either as a single 5-mg/kg dose or three 1-mg/kg doses for only the first 24 h and compared to the regimens administered for the full 96-h duration. For all experiments, physiologic conditions of albumin, calcium, and pH were simulated. Both regimens of daptomycin achieved 99.9% kill by 32 h and maintained bactericidal activity against both isolates, which was significantly different from vancomycin, which displayed bacteriostatic activity (
P
< 0.05). The effects of all short-course regimens of gentamicin were equal to those of the full-duration regimens in combination with daptomycin. Adding three doses of gentamicin (1 mg/kg) to daptomycin resulted in enhancement and bactericidal activity at 24 h against both MRSA and MSSA. The addition of a single dose of gentamicin (5 mg/kg) enhanced or improved the activity of daptomycin and resulted in early bactericidal activity at 4 h against both isolates. The addition of three doses of gentamicin (1 mg/kg) did not improve the activity of vancomycin. However, the addition of a single 5-mg/kg dose of gentamicin to vancomycin resulted in early enhancement at 4 h and 99.9% kill at 32 h for MRSA. These results suggest that a single high dose of gentamicin in combination with daptomycin or vancomycin may be of utility to maximize synergistic and bactericidal activity and minimize toxicity. Further investigation is warranted.
Constitutive
soxR
Mutations Contribute to Multiple-Antibiotic Resistance in Clinical
Escherichia coli
Isolates
Authors: Koutsolioutsou Anastasia , Peña-Llopis Samuel , Demple Bruce 
Published: June 2005

ABSTRACT

The
soxRS
regulon of
Escherichia coli
and
Salmonella enterica
is induced by redox-cycling compounds or nitric oxide and provides resistance to superoxide-generating agents, macrophage-generated nitric oxide, antibiotics, and organic solvents. We have previously shown that constitutive expression of
soxRS
can contribute to quinolone resistance in clinically relevant
S. enterica
. In this work, we have carried out an analysis of the mechanism of constitutive
soxS
expression and its role in antibiotic resistance in
E. coli
clinical isolates. We show that constitutive
soxS
expression in three out of six strains was caused by single point mutations in the
soxR
gene. The mutant SoxR proteins contributed to the multiple-antibiotic resistance phenotypes of the clinical strains and were sufficient to confer multiple-antibiotic resistance in a fresh genetic background. In the other three clinical isolates, we observed, for the first time, that elevated
soxS
expression was not due to mutations in
soxR
. The mechanism of such increased
soxS
expression remains unclear. The same
E. coli
clinical isolates harbored polymorphic
soxR
and
soxS
DNA sequences, also seen for the first time.
Macrolide Resistance in
Campylobacter jejuni
and
Campylobacter coli
: Molecular Mechanism and Stability of the Resistance Phenotype
Authors: Gibreel Amera , Kos Veronica N. , Keelan Monika , Trieber Cathy A. , Levesque Simon , Michaud Sophie , Taylor Diane E. 
Published: June 2005

ABSTRACT

A collection of 23 macrolide-resistant
Campylobacter
isolates from different geographic areas was investigated to determine the mechanism and stability of macrolide resistance. The isolates were identified as
Campylobacter jejuni
or
Campylobacter coli
based on the results of the hippurate biochemical test in addition to five PCR-based genotypic methods. Three point mutations at two positions within the peptidyl transferase region in domain V of the 23S rRNA gene were identified. About 78% of the resistant isolates exhibited an A→G transition at
Escherichia coli
equivalent base 2059 of the 23S rRNA gene. The isolates possessing this mutation showed a wide range of erythromycin and clarithromycin MICs. Thus, this mutation may incur a greater probability of treatment failure in populations infected by resistant
Campylobacter
isolates. Another macrolide-associated mutation (A→C transversion), at
E. coli
equivalent base 2058, was detected in about 13% of the isolates. An A→G transition at a position cognate with
E. coli
23S rRNA base 2058, which is homologous to the A2142G mutation commonly described in
Helicobacter pylori
, was also identified in one of the
C. jejuni
isolates examined. In the majority of
C. jejuni
isolates, the mutations in the 23S rRNA gene were homozygous except in two cases where the mutation was found in two of the three copies of the target gene. Natural transformation demonstrated the transfer of the macrolide resistance phenotype from a resistant
Campylobacter
isolate to a susceptible
Campylobacter
isolate. Growth rates of the resulting transformants containing A-2058→C or A-2059→G mutations were similar to that of the parental isolate. The erythromycin resistance of six of seven representative isolates was found to be stable after successive subculturing in the absence of erythromycin selection pressure regardless of the resistance level, the position of the mutation, or the number of the mutated copies of the target gene. One
C. jejuni
isolate showing an A-2058→G mutation, however, reverted to erythromycin and clarithromycin susceptibility after 55 subcultures on erythromycin-free medium. Investigation of ribosomal proteins L4 and L22 by sequence analysis in five representative isolates of
C. jejuni
and
C. coli
demonstrated no significant macrolide resistance-associated alterations in either the L4 or the L22 protein that might explain either macrolide resistance or enhancement of the resistance level.
Population Pharmacokinetics of Cefepime in the Neonate
Authors: Capparelli Edmund , Hochwald Christine , Rasmussen Maynard , Parham Amy , Bradley John , Moya Fernando 
Published: June 2005

ABSTRACT
Newborn infants cared for in neonatal intensive care units may develop nosocomial infections. Cefepime, a “fourth-generation” cephalosporin (i.e., with activity against virtually all of the chromosomal-beta-lactamase-producing and many extended-spectrum-beta-lactamase-producing organisms), provides excellent activity against many gram-negative pathogens resistant to expanded-spectrum cephalosporins currently used to treat neonatal infections. The purpose of this study was to determine the pharmacokinetics of cefepime in this population to optimize dosing and minimize potential adverse events. Premature and term infants <4 months of age hospitalized in two neonatal intensive care units were studied. Limited pharmacokinetic (PK) sampling occurred following a dose of cefepime at 50 mg/kg of body weight infused over 30 min. Population pharmacokinetic parameters were determined using the program NONMEM. Fifty-five infants were enrolled. Their average (± standard deviation) gestational age at birth was 30.5 ± 5.3 weeks, and their average postnatal age at PK evaluation was 14.5 ± 14.7 days. In the final PK model, cefepime clearance (CL) was strongly associated with serum creatinine (SCr) (CL [ml/min/kg] = 0.26 + 0.59/SCr). The volume of distribution for infants with a postconceptional age of <30 weeks was larger than that for infants with a postconceptional age of >30 weeks (0.51 versus 0.39 liter/kg, respectively). The Bayesian analysis-predicted cefepime trough concentration at a dose of 50 mg/kg every 12 h for infants ≤14 days of age was 29.9 ± 16.6 μg/ml. Cefepime, dosed at 30 mg/kg/dose every 12 h for infants less than 14 days of age, regardless of gestational age, should provide antibiotic exposure equivalent to or greater than 50 mg/kg every 8 h in older infants and children.
Novel Approach to Mapping of Resistance Mutations in Whole Genomes by Using Restriction Enzyme Modulation of Transformation Efficiency
Authors: Lerner Claude G. , Kakavas Stephan J. , Wagner Christian , Chang Richard T. , Merta Philip J. , Ruan Xiaoan , Metzger Randy E. , Beutel Bruce A. 
Published: June 2005

ABSTRACT

Restriction enzyme modulation of transformation efficiencies (REMOTE) is a method that makes use of genome restriction maps and experimentally observed differences in transformation efficiencies of genomic DNA restriction digests to discover the location of mutations in genomes. The frequency with which digested genomic DNA from a resistant strain transforms a susceptible strain to resistance is primarily determined by the size of the fragment containing the resistance mutation and the distance of the mutation to the end of the fragment. The positions of restriction enzyme cleavage sites immediately flanking the resistance mutation define these parameters. The mapping procedure involves a process of elimination in which digests that transform with high frequency indicate that the restriction enzyme cleavage sites are relatively far away from the mutation, while digests that transform with low frequency indicate that the sites are close to the mutation. The transformation data are compared computationally to the genome restriction map to identify the regions that best fit the data. Transformations with PCR amplicons encompassing candidate regions identify the resistance locus and enable identification of the mutation. REMOTE was developed using
Haemophilus influenzae
strains with mutations in
gyrA
,
gyrB
, and
rpsE
that confer resistance to ciprofloxacin, novobiocin, and spectinomycin, respectively. We applied REMOTE to identify mutations that confer resistance to two novel antibacterial compounds. The resistance mutations were found in genes that can decrease the intracellular concentration of compounds:
acrB
, which encodes a subunit of the AcrAB-TolC efflux pump; and
fadL
, which encodes a long-chain fatty acid transporter.
Structure-Based Phylogeny of the Metallo-β-Lactamases
Authors: Garau Gianpiero , Di Guilmi Anne Marie , Hall Barry G. 
Published: June 2005

ABSTRACT

The metallo-β-lactamases fall into two groups: Ambler class B subgroups B1 and B2 and Ambler class B subgroup B3. The two groups are so distantly related that there is no detectable sequence homology between members of the two different groups, but homology is clearly detectable at the protein structure level. The multiple structure alignment program MAPS has been used to align the structures of eight metallo-β-lactamases and five structurally homologous proteins from the metallo-β-lactamase superfamily, and that alignment has been used to construct a phylogenetic tree of the metallo-β-lactamases. The presence of genes from
Eubacteria
,
Archaebacteria
, and
Eukaryota
on that tree is consistent with a very ancient origin of the metallo-β-lactamase family.
Drug-Induced Regulation of the
MDR1
Promoter in
Candida albicans
Authors: Harry Jo Beth , Oliver Brian G. , Song Jia L. , Silver Peter M. , Little John T. , Choiniere Jake , White Theodore C. 
Published: June 2005

ABSTRACT

Resistance of
Candida albicans
to azole antifungal drugs is mediated by two types of efflux pumps, encoded by the
MDR1
gene and the
CDR
gene family.
MDR1
mRNA levels in a susceptible clinical isolate are induced by benomyl (BEN) but not by other drugs previously shown to induce
MDR1
. To monitor
MDR1
expression under several conditions, the
MDR1
promoter was fused to the
Renilla reniformis
luciferase reporter gene (
RLUC
). The promoter was monitored for its responses to four oxidizing agents, five toxic hydrophobic compounds, and an alkylating agent, all shown to induce major facilitator pumps in other organisms. Deletion constructs of the
MDR1
promoter were used to analyze the basal transcription of the promoter and its responses to the toxic compound BEN and the oxidizing agent
tert
-butyl hydrogen peroxide (T-BHP). The
cis
-acting elements in the
MDR1
promoter responsible for induction by BEN were localized between −399 and −299 upstream of the start codon. The
cis
-acting elements responsible for
MDR1
induction by T-BHP were localized between −601 and −500 upstream of the start codon. The T-BHP induction region contains a sequence that resembles the
YAP1
-responsive element (YRE) in
Saccharomyces cerevisiae
. This
Candida
YRE was placed upstream of a noninducible promoter in the luciferase construct, resulting in an inducible promoter. Inversion or mutation of the 7-bp YRE eliminated induction. Many of the drugs used in this analysis induce the
MDR1
promoter at concentrations that inhibit cell growth. These analyses define
cis
-acting elements responsible for drug induction of the
MDR1
promoter.
Multiple-Antibiotic Resistance in
Salmonella enterica
Serotype Paratyphi B Isolates Collected in France between 2000 and 2003 Is Due Mainly to Strains Harboring
Salmonella
Genomic Islands 1, 1-B, and 1-C
Authors: Weill François-Xavier , Fabre Laëtitia , Grandry Bernadette , Grimont Patrick A. D. , Casin Isabelle 
Published: June 2005

ABSTRACT

This study was conducted to investigate the occurrence of multiple-antibiotic resistance among 261 clinical isolates of
Salmonella enterica
serotype Paratyphi B strains collected between 2000 and 2003 through the network of the French National Reference Center for
Salmonella
. The 47 multidrug-resistant (MDR) isolates identified (18%), were characterized on the basis of the presence of several resistance genes (
bla
TEM
,
bla
PSE-1
,
bla
CTX-M
,
floR
,
aadA2
,
qacEΔ1
, and
sul1
), the presence of
Salmonella
genomic island 1 (SGI1) by PCR mapping and hybridization, and the clonality of these isolates by several molecular (ribotyping, IS
200
profiling, and pulsed-field gel electrophoresis [PFGE]) and phage typing methods. The results of PCR and Southern blot experiments indicated that 39 (83%) of the 47
S. enterica
serotype Paratyphi B biotype Java MDR isolates possessed the SGI1 cluster (MDR/SGI1). Among these 39 MDR/SGI1 isolates, only 3 contained variations in SGI1, SGI1-B (
n
= 1) and SGI1-C (
n
= 2). The 39 MDR/SGI1 isolates showed the same specific PstI-IS
200
profile 1, which contained seven copies from 2.6 to 18 kb. Two PstI ribotypes were found in MDR/SGI1 isolates, RP1 (
n
= 38) and RP6 (
n
= 1). Ribotype RP1 was also found in two susceptible strains. Analysis by PFGE using XbaI revealed that all the MDR/SGI1 isolates were grouped in two related clusters, with a similarity percentage of 82%. Isolation of MDR/SGI1 isolates in France was observed mainly between the second quarter of 2001 and the end of 2002. The source of the contamination has not been identified to date. A single isolate possessing the extended-spectrum β-lactamase
bla
CTX-M-15
gene was also identified during the study.