bluuebunny/crossref_metadata_2025_split huggingface dataset:
Safety and Bactericidal Activity of Rifalazil in Patients with Pulmonary Tuberculosis
Authors: Dietze Reynaldo , Teixeira Luciléia , Rocha Lia Márcia Canedo , Palaci Moisés , Johnson John L. , Wells Charles , Rose Lynn , Eisenach Kathleen , Ellner Jerrold J. 
Published: July 2002

ABSTRACT

Rifalazil, also known as KRM-1648 or benzoxazinorifamycin, is a new semisynthetic rifamycin with a long half-life of approximately 60 h. Rifalazil has potent bactericidal activity against
Mycobacterium tuberculosis
in vitro and in animal models of tuberculosis (TB). Prior studies in healthy volunteers showed that once-weekly doses of 25 to 50 mg of rifalazil were well tolerated. In this randomized, open-label, active-controlled phase II clinical trial, 65 subjects with sputum smear-positive pulmonary TB received one of the following regimens for the first 2 weeks of therapy: 16 subjects received isoniazid (INH) (5 mg/kg of body weight) daily; 16 received INH (5 mg/kg) and rifampin (10 mg/kg) daily; 17 received INH (5 mg/kg) daily plus 10 mg of rifalazil once weekly; and 16 received INH (5 mg/kg) daily and 25 mg of rifalazil once weekly. All subjects were then put on 6 months of standard TB therapy. Pretreatment and day 15 sputum CFU of
M. tuberculosis
were measured to assess the bactericidal activity of each regimen. The number of drug-related adverse experiences was low and not significantly different among treatment arms. A transient decrease in absolute neutrophil count to less than 2,000 cells/mm
3
was detected in 10 to 20% of patients in the rifalazil- and rifampin-containing treatment arms without clinical consequences. Decreases in CFU counts were comparable among the four treatment arms; however, the CFU results were statistically inconclusive due to the variability in the control arms. Acquired drug resistance did not occur in any patient. Studies focused on determining a maximum tolerated dose will help elucidate the full anti-TB effect of rifalazil.
Antimicrobial Activity of Prosthetic Heart Valve Sewing Cuffs Coated With Minocycline and Rifampin
Authors: Darouiche Rabih O. , Fowler Vance G. , Adal Karim , Kielhofner Marcia , Mansouri David , Reller L. Barth 
Published: July 2002

ABSTRACT

Prosthetic heart valve sewing cuffs coated with minocycline and rifampin exhibited in vitro zones of inhibition against all 52 tested clinical isolates responsible for prosthetic valve endocarditis. An in vitro elution study of these coated sewing cuffs demonstrated residual zones of inhibition against
Staphylococcus epidermidis
for at least 4 weeks.
Oxazolidinone Antibiotics Target the P Site onEscherichiacoliRibosomes
Authors: Aoki Hiroyuki , Ke Lizhu , Poppe Susan M. , Poel Toni J. , Weaver Elizabeth A. , Gadwood Robert C. , Thomas Richard C. , Shinabarger Dean L. , Ganoza M. Clelia 
Published: July 2002

ABSTRACTThe oxazolidinones are a novel class of antimicrobial agents that target protein synthesis in a wide spectrum of gram-positive and anaerobic bacteria. The oxazolidinone PNU-100766 (linezolid) inhibits the binding of fMet-tRNA to 70S ribosomes. Mutations to oxazolidinone resistance inHalobacteriumhalobium,Staphylococcusaureus, andEscherichiacolimap at or near domain V of the 23S rRNA, suggesting that the oxazolidinones may target the peptidyl transferase region responsible for binding fMet-tRNA. This study demonstrates that the potency of oxazolidinones corresponds to increased inhibition of fMet-tRNA binding. The inhibition of fMet-tRNA binding is competitive with respect to the fMet-tRNA concentration, suggesting that the P site is affected. The fMet-tRNA reacts with puromycin to form peptide bonds in the presence of elongation factor P (EF-P), which is needed for optimum specificity and efficiency of peptide bond synthesis. Oxazolidinone inhibition of the P site was evaluated by first binding fMet-tRNA to the A site, followed by translocation to the P site with EF-G. All three of the oxazolidinones used in this study inhibited translocation of fMet-tRNA. We propose that the oxazolidinones target the ribosomal P site and pleiotropically affect fMet-tRNA binding, EF-P stimulated synthesis of peptide bonds, and, most markedly, EF-G-mediated translocation of fMet-tRNA into the P site.
TEM Derivative-Producing
Enterobacter aerogenes
Strains: Dissemination of a Prevalent Clone
Authors: Dumarche P. , De Champs C. , Sirot D. , Chanal C. , Bonnet R. , Sirot J. 
Published: July 2002

ABSTRACT

TEM-24 (CAZ-6) extended-spectrum β-lactamase (ESBL) was detected in 1988 in Clermont-Ferrand, France, in
Klebsiella pneumoniae
(
bla
TEM-24
) and
Enterobacter aerogenes
(
bla
TEM-24b
), and since 1994, a TEM-24-producing
E. aerogenes
clonal strain has been observed elsewhere in the country. To determine if the spread of this clonal strain was restricted to TEM-24-producing
E. aerogenes
strains, 84
E. aerogenes
strains (non-TEM/SHV-producing strains, TEM-1- or -2-producing strains, and different ESBL-producing strains), isolated from 1988 to 1999 in Clermont-Ferrand (
n
= 59) and in 11 other French hospitals in 1998 (
n
= 25), were studied. A clonal strain was found for TEM-24- but also for TEM-3- and TEM-1- or 2-producing isolates. This study shows that there is a clonal strain dependent on acquisition of the TEM-type enzyme (TEM-24 and other TEM types).
Comparative In Vitro Activities of Ertapenem (MK-0826) against 469 Less Frequently Identified Anaerobes Isolated from Human Infections
Authors: Goldstein Ellie J. C. , Citron Diane M. , Merriam C. Vreni , Warren Yumi A. , Tyrrell Kerin L. , Fernandez Helen 
Published: July 2002

ABSTRACT

We studied the in vitro activity of ertapenem against 469 less frequently identified anaerobes from 11 genera and 52 species isolated from human infections. Ertapenem was uniformly active against 460 of 469 (98%) strains at concentrations of ≤4 μg/ml. Only 4 of 14
Clostridium difficile
, 1 of 11
Clostridium innocuum
, and 4 of 6
Lactobacillus
sp. strains required ertapenem concentrations of ≥8 μg/ml for inhibition.
Characterization of Plasmids Carrying CMY-2 from Expanded-Spectrum Cephalosporin-Resistant
Salmonella
Strains Isolated in the United States between 1996 and 1998
Authors: Carattoli A. , Tosini F. , Giles W. P. , Rupp M. E. , Hinrichs S. H. , Angulo F. J. , Barrett T. J. , Fey P. D. 
Published: July 2002

ABSTRACT

Sequencing of DNA from 15 expanded-spectrum cephalosporin (e.g., ceftriaxone)-resistant
Salmonella
isolates obtained in the United States revealed that resistance to ceftriaxone in all isolates was mediated by
cmy-2.
Hybridization patterns revealed three plasmid structures containing
cmy-2
in these 15 isolates. These data suggest that the spread of
cmy-2
among
Salmonella
strains is occurring through mobilization of the
cmy-2
gene into different plasmid backbones and consequent horizontal transfer by conjugation.
PEPT1-Mediated Cefixime Uptake into Human Intestinal Epithelial Cells Is Increased by Ca
2+
Channel Blockers
Authors: Wenzel Uwe , Kuntz Sabine , Diestel Simone , Daniel Hannelore 
Published: July 2002

ABSTRACT

Ca
2+
channel blockers like nifedipine have been shown to increase the oral bioavailability of β-lactam antibiotics, such as cefixime, in humans. The molecular mode of action of Ca
2+
channel blockers on β-lactam absorption, however, has not yet been defined. Using the Caco-2 human intestinal epithelial cell line, we assessed whether alterations in intracellular free Ca
2+
ion (Ca
2+
in
) concentrations by Ca
2+
channel blockers or by Ca
2+
ionophores affect [
14
C]cefixime absorption. Reduction of Ca
2+
in
levels by Ca
2+
channel blockers (nifedipine, verapamil, diltiazem, or bepridil) at concentrations of 100 μM led to 35 to 50% increases in the cellular uptake of 1 mM [
14
C]cefixime. Increases in Ca
2+
in
levels by Ca
2+
ionophores, on the other hand, led to 40% reductions in [
14
C]cefixime absorption. Nifedipine increased the
V
max
of cefixime transport by 67%, whereas the

K
m

of cefixime transport remained unaffected. By measuring the pH in Caco-2 cells loaded with the pH-sensitive fluorescent dye 2′,7′-bis(2-carboxyethyl)-5-(6)-carboxyfluorescein, we show that cefixime transport mediated by the intestinal H
+
-coupled peptide transporter PEPT1 leads to intracellular acidification. This acid load was reduced by nifedipine, although the Ca
2+
channel blocker increased the level of H
+
and cefixime cotransport. Increases in Ca
2+
in
levels by ionomycin enhanced the decline in intracellular pH induced by cefixime alone, although ionomycin reduced the level of H
+
and cefixime cotransport. In conclusion, our studies demonstrate that alterations of Ca
2+
in
levels, e.g., by Ca
2+
channel blockers, affect pH regulatory systems, such as apical Na
+
and H
+
exchange, and thereby alter the H
+
gradient that serves as the driving force for uptake of β-lactams into intestinal epithelial cells.
Genetic Characterization of Soybean Rhizobia in Paraguay
Authors: Chen Lu Shi , Figueredo Antonio , Pedrosa Fábio O. , Hungria Mariangela 
Published: July 2002

ABSTRACT

The soybean is an exotic plant introduced in Paraguay in this century; commercial cropping expanded after the 1970s. Inoculation is practiced in just 15 to 20% of the cropping areas, but root nodulation occurs in most sites where soybeans grow. Little is known about rhizobial diversity in South America, and no study has been performed in Paraguay until this time. Therefore, in this study, the molecular characterization of 78 rhizobial isolates from soybean root nodules, collected under field conditions in 16 sites located in the two main producing states, Alto Paraná and Itapúa, was undertaken. A high level of genetic diversity was detected by an ERIC-REP-PCR analysis, with the majority of the isolates representing unique strains. Most of the 58 isolates characterized by slow growth and alkaline reactions in a medium containing mannitol as a carbon source were clustered with strains representative of the
Bradyrhizobium japonicum
and
Bradyrhizobium elkanii
species, and the 16S ribosomal DNA (rDNA) sequences of 5 of those isolates confirmed the species identities. However, slow growers were highly polymorphic in relation to the reference strains, including five carried in commercial inoculants in neighboring countries, thus indicating that the Paraguayan isolates might represent native bradyrhizobia. Twenty isolates highly polymorphic in the ERIC-REP-PCR profiles were characterized by fast growth and acid reactions in vitro, and two of them showed high 16S rDNA identities with
Rhizobium
genomic species Q. However, two other fast growers showed high 16S rDNA identity with
Agrobacterium
spp., and both of these strains established efficient symbioses with soybean plants.
Characterization ofColletotrichum acutatumCausing Anthracnose of Anemone (Anemone coronariaL.)
Authors: Freeman Stanley , Shabi Ezra , Katan Talma 
Published: July 2002

ABSTRACTAnthracnose, or leaf-curl disease of anemone, caused byColletotrichumsp., has been reported to occur in Australia, western Europe, and Japan. Symptoms include tissue necrosis, corm rot, leaf crinkles, and characteristic spiral twisting of floral peduncles. Three epidemics of the disease have been recorded in Israel: in 1978, in 1990 to 1993, and in 1996 to 1998. We characterized 92Colletotrichumisolates associated with anthracnose of anemone (Anemone coronariaL.) for vegetative compatibility (72 isolates) and for molecular genotype (92 isolates) and virulence (4 isolates). Eighty-six of the isolates represented the three epidemics in Israel, one isolate was from Australia, and five isolates originated from western Europe. We divided these isolates into three vegetative-compatibility groups (VCGs). One VCG (ANE-A) included all 10 isolates from the first and second epidemics, and 13 of 62 examined isolates from the third epidemic in Israel, along with the isolate from Australia and 4 of 5 isolates from Europe. Another VCG (ANE-F) included most of the examined isolates (49 of the 62) from the third epidemic, as well asColletotrichum acutatumfrom strawberry, in Israel. Based on PCR amplification with species-specific primers, all of the anemone isolates were identified asC. acutatum. Anemone and strawberry isolates of the two VCGs were genotypically similar and indistinguishable when compared by arbitrarily primed PCR of genomic DNA. Only isolate NL-12 from The Netherlands, confirmed asC. acutatumbut not compatible with either VCG, had a distinct genotype; this isolate represents a third VCG ofC. acutatum. Isolates from anemone and strawberry could infect both plant species in artificial inoculations. VCG ANE-F was recovered from natural infections of both anemone and strawberry, but VCG ANE-A was recovered only from anemone. This study ofC. acutatumfrom anemone illustrates the potential of VCG analysis to reveal distinct subspecific groups within a pathogen population which appears to be genotypically homogeneous by molecular assays.
Carbon Dioxide and Nisin Act Synergistically on
Listeria monocytogenes
Authors: Nilsson Lilian , Chen Yuhuan , Chikindas Michael L. , Huss Hans Henrik , Gram Lone , Montville Thomas J. 
Published: July 2002

ABSTRACT

This paper examines the synergistic action of carbon dioxide and nisin on
Listeria monocytogenes
Scott A wild-type and nisin-resistant (Nis
r
) cells grown in broth at 4°C. Carbon dioxide extended the lag phase and decreased the specific growth rate of both strains, but to a greater degree in the Nis
r
cells. Wild-type cells grown in 100% CO
2
were two to five times longer than cells grown in air. Nisin (2.5 μg/ml) did not decrease the viability of Nis
r
cells but for wild-type cells caused an immediate 2-log reduction of viability when they were grown in air and a 4-log reduction when they were grown in 100% CO
2
. There was a quantifiable synergistic action between nisin and CO
2
in the wild-type strain. The MIC of nisin for the wild-type strain grown in the presence of 2.5 μg of nisin per ml increased from 3.1 to 12.5 μg/ml over 35 days, but this increase was markedly delayed for cultures in CO
2
. This synergism between nisin and CO
2
was examined mechanistically by following the leakage of carboxyfluorescein (CF) from listerial liposomes. Carbon dioxide enhanced nisin-induced CF leakage, indicating that the synergistic action of CO
2
and nisin occurs at the cytoplasmic membrane. Liposomes made from cells grown in a CO
2
atmosphere were even more sensitive to nisin action. Liposomes made from cells grown at 4°C were dramatically more nisin sensitive than were liposomes derived from cells grown at 30°C. Cells grown in the presence of 100% CO
2
and those grown at 4°C had a greater proportion of short-chain fatty acids. The synergistic action of nisin and CO
2
is consistent with a model where membrane fluidity plays a role in the efficiency of nisin action.
Effect of Catalase on Hydrogen Peroxide Penetration into
Pseudomonas aeruginosa
Biofilms
Authors: Stewart Philip S. , Roe Frank , Rayner Joanna , Elkins James G. , Lewandowski Zbigniew , Ochsner Urs A. , Hassett Daniel J. 
Published: July 2002

ABSTRACT

The penetration of hydrogen peroxide into biofilms formed by wild-type and catalase-deficient
Pseudomonas aeruginosa
strains was measured using microelectrodes. A flowing stream of hydrogen peroxide (50 mM, 1 h) was unable to penetrate or kill wild-type biofilms but did penetrate and partially kill biofilms formed by an isogenic strain in which the
katA
gene was knocked out. Catalase protects aggregated bacteria by preventing full penetration of hydrogen peroxide into the biofilm.
Targeted Disruption of the
kstD
Gene Encoding a 3-Ketosteroid Δ
1
-Dehydrogenase Isoenzyme of
Rhodococcus erythropolis
Strain SQ1
Authors: van der Geize R. , Hessels G. I. , van Gerwen R. , Vrijbloed J. W. , van der Meijden P. , Dijkhuizen L. 
Published: July 2002

ABSTRACT

Microbial phytosterol degradation is accompanied by the formation of steroid pathway intermediates, which are potential precursors in the synthesis of bioactive steroids. Degradation of these steroid intermediates is initiated by Δ
1
-dehydrogenation of the steroid ring structure. Characterization of a 2.9-kb DNA fragment of
Rhodococcus erythropolis
SQ1 revealed an open reading frame (
kstD
) showing similarity with known 3-ketosteroid Δ
1
-dehydrogenase genes. Heterologous expression of
kstD
yielded 3-ketosteroid Δ
1
-dehydrogenase (KSTD) activity under the control of the
lac
promoter in
Escherichia coli
. Targeted disruption of the
kstD
gene in
R. erythropolis
SQ1 was achieved, resulting in loss of more than 99% of the KSTD activity. However, growth on the steroid substrate 4-androstene-3,17-dione or 9α-hydroxy-4-androstene-3,17-dione was not abolished by the
kstD
gene disruption. Bioconversion of phytosterols was also not blocked at the level of Δ
1
-dehydrogenation in the
kstD
mutant strain, since no accumulation of steroid pathway intermediates was observed. Thus, inactivation of
kstD
is not sufficient for inactivation of the Δ
1
-dehydrogenase activity. Native polyacrylamide gel electrophoresis of cell extracts stained for KSTD activity showed that
R. erythropolis
SQ1 in fact harbors two activity bands, one of which is absent in the
kstD
mutant strain.
Evaluation of a Fluorescent Lectin-Based Staining Technique for Some Acidophilic Mining Bacteria
Authors: Fife Dee Jay , Bruhn Debby F. , Miller Karen S. , Stoner Daphne L. 
Published: July 2002

ABSTRACT
A fluorescence-labeled wheat germ agglutinin staining technique (R. K. Sizemore et al., Appl. Environ. Microbiol. 56:2245–2247, 1990) was modified and found to be effective for staining gram-positive, acidophilic mining bacteria. Bacteria identified by others as being gram positive through 16S rRNA sequence analyses, yet clustering near the divergence of that group, stained weakly. Gram-negative bacteria did not stain. Background staining of environmental samples was negligible, and pyrite and soil particles in the samples did not interfere with the staining procedure.
Genotypic Heterogeneity of
Streptococcus oralis
and Distinct Aciduric Subpopulations in Human Dental Plaque
Authors: Alam S. , Brailsford S. R. , Adams S. , Allison C. , Sheehy E. , Zoitopoulos L. , Kidd E. A. , Beighton D. 
Published: July 2002

ABSTRACT

The genotypic heterogeneity of
Streptococcus oralis
isolated from the oral cavity was investigated using repetitive extragenic palindromic PCR. Unrelated subjects harbored unique genotypes, with numerous genotypes being isolated from an individual.
S. oralis
is the predominant aciduric bacterium isolated from noncarious tooth sites. Genotypic comparison of the aciduric populations isolated at pH 5.2 with those isolated from mitis-salivarius agar (MSA) (pH 7.0) indicated that the aciduric populations were genotypically distinct in the majority of subjects (χ
2
= 13.09;
P
= 0.0031). Neither the aciduric nor the MSA-isolated strains were stable, with no strains isolated at baseline being isolated 4 or 12 weeks later in the majority of subjects. The basis of this instability is unknown but is similar to that reported for
Streptococcus mitis
. Examination of
S. oralis
strains isolated from cohabiting couples demonstrated that in three of five couples, genotypically identical strains were isolated from both partners and this was confirmed by using
Salmonella enteritidis
repetitive element PCR and enterobacterial PCR typing. These data provide further evidence of the physiological and genotypic heterogeneity of non-mutans streptococci. The demonstration of distinct aciduric populations of
S. oralis
implies that the role of these and other non-mutans streptococci in the caries process requires reevaluation.
Tandem Repeat of a Transcriptional Enhancer Upstream of the Sterol 14α-Demethylase Gene (
CYP51
) in
Penicillium digitatum
Authors: Hamamoto Hiroshi , Hasegawa Koji , Nakaune Ryoji , Lee Young Jin , Makizumi Yoshiyuki , Akutsu Katsumi , Hibi Tadaaki 
Published: July 2002

ABSTRACT

We investigated the mechanism of resistance to demethylation inhibitors (DMI) in
Penicillium digitatum
by isolating the
CYP51
gene, which encodes the target enzyme (P450
14DM
) of DMI, from three DMI-resistant and three DMI-sensitive strains. The structural genes of all six strains were identical, but in the promoter region, a unique 126-bp sequence was tandemly repeated five times in the DMI-resistant strains and was present only once in the DMI-sensitive strains. Constitutive expression of
CYP51
in the resistant strains was about 100-fold higher than that in the sensitive strains. We introduced
CYP51
, including the promoter region, from a DMI-resistant strain into a DMI-sensitive strain, which rendered the transformants DMI resistant and increased
CYP51
expression. We also found that if the number of copies of the repeat was reduced to two, resistance and
CYP51
expression also decreased. These results indicate that the 126-bp unit acts as a transcriptional enhancer and that a tandem repeat of the unit enhances
CYP51
expression, resulting in DMI resistance. This is a new fungicide resistance mechanism for filamentous fungi.
Numerical Analysis of Grassland Bacterial Community Structure under Different Land Management Regimens by Using 16S Ribosomal DNA Sequence Data and Denaturing Gradient Gel Electrophoresis Banding Patterns
Authors: McCaig Allison E. , Glover L. Anne , Prosser James I. 
Published: July 2002

ABSTRACT
Bacterial diversity in unimproved and improved grassland soils was assessed by PCR amplification of bacterial 16S ribosomal DNA (rDNA) from directly extracted soil DNA, followed by sequencing of ∼45 16S rDNA clones from each of three unimproved and three improved grassland samples (A. E. McCaig, L. A. Glover, and J. I. Prosser, Appl. Environ. Microbiol. 65:1721–1730, 1999) or by denaturing gradient gel electrophoresis (DGGE) of total amplification products. Semi-improved grassland soils were analyzed only by DGGE. No differences between communities were detected by calculation of diversity indices and similarity coefficients for clone data (possibly due to poor coverage). Differences were not observed between the diversities of individual unimproved and improved grassland DGGE profiles, although considerable spatial variation was observed among triplicate samples. Semi-improved grassland samples, however, were less diverse than the other grassland samples and had much lower within-group variation. DGGE banding profiles obtained from triplicate samples pooled prior to analysis indicated that there was less evenness in improved soils, suggesting that selection for specific bacterial groups occurred. Analysis of DGGE profiles by canonical variate analysis but not by principal-coordinate analysis, using unweighted data (considering only the presence and absence of bands) and weighted data (considering the relative intensity of each band), demonstrated that there were clear differences between grasslands, and the results were not affected by weighting of data. This study demonstrated that quantitative analysis of data obtained by community profiling methods, such as DGGE, can reveal differences between complex microbial communities.