bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Reporter Cell Line To Evaluate the Sequential Emergence of Multiple Human Cytomegalovirus Mutations during In Vitro Drug Exposure
Authors: Gilbert C. , Boivin G. 
Published: November 2005

ABSTRACT
We developed a new reporter cell line for human cytomegalovirus (HCMV) drug susceptibility testing. This cell line was obtained by incorporating the luciferase reporter gene under the control of an HCMV-specific promoter into the genome of astrocytoma cells (U373MG). We then used our reporter cell line to evaluate phenotypic changes conferred by the sequential emergence of HCMV UL54 and UL97 mutations following long-term drug exposure. The laboratory strain AD169 was passaged in the presence of increasing concentrations of ganciclovir (one viral line) or foscarnet (two viral lines). Resistant viruses were plaque purified at five different concentrations of ganciclovir and at three different concentrations of foscarnet. In addition to the previously described M460I and L595S UL97 mutations and the L545S and V812L UL54 mutations, exposition to ganciclovir (up to 3,000 μM) resulted in the selection of two unreported UL54 mutations (P829S and D879G). Passages in the presence of foscarnet (up to 3,000 μM) resulted in the selection of seven not previously described UL54 mutations (K500N, T552N, S585A, N757K, L802V, L926V, and L957F) in addition to the N408D mutation that has been associated with ganciclovir and cidofovir resistance. Long-term exposure of HCMV to either ganciclovir or foscarnet ultimately resulted in the selection of multiple UL54 mutations that conferred high levels of resistance to all approved HCMV DNA polymerase inhibitors, i.e., ganciclovir, cidofovir, and foscarnet. Emergence of each viral mutation conferred stepwise increases in drug 50% inhibitory concentrations that could be objectively measured with the new reporter cell assay.
Inhibition of Human Immunodeficiency Virus Type 1 Reverse Transcriptase, RNase H, and Integrase Activities by Hydroxytropolones
Authors: Didierjean Joël , Isel Catherine , Querré Flore , Mouscadet Jean-François , Aubertin Anne-Marie , Valnot Jean-Yves , Piettre Serge R. , Marquet Roland 
Published: November 2005

ABSTRACT

Human immunodeficiency virus type I reverse transcriptase (RT) possesses distinct DNA polymerase and RNase H sites, whereas integrase (IN) uses the same active site to perform 3′-end processing and strand transfer of the proviral DNA. These four enzymatic activities are essential for viral replication and require metal ions. Two Mg
2+
ions are present in the RT polymerase site, and one or two Mg
2+
ions are required for the catalytic activities of RNase H and IN. We tested the possibility of inhibition of the RT polymerase and RNase H as well as the IN 3′-end processing and transfer activities of purified enzymes by a series of 3,7-dihydroxytropolones designed to target two Mg
2+
ions separated by ∼3.7 Å. The RT polymerase and IN 3′ processing and strand transfer activities were inhibited at submicromolar concentrations, while the RNase H activity was inhibited in the low micromolar range. In all cases, the lack of inhibition by tropolones and O-methylated 3,7-dihydroxytropolones was consistent with the active molecules binding the metal ions in the active site. In addition, inhibition of the DNA polymerase activity was shown to depend on the Mg
2+
concentration. Furthermore, selective inhibitors were identified for several of the activities tested, leaving some potential for design of improved inhibitors. However, all tested compounds exhibited cellular toxicity that presently limits their applications.
Treatment of
Candida glabrata
Infection in Immunosuppressed Mice by Using a Combination of Liposomal Amphotericin B with Caspofungin or Micafungin
Authors: Olson Jon A. , Adler-Moore Jill P. , Smith P. J. , Proffitt Richard T. 
Published: November 2005

ABSTRACT

While
Candida albicans
remains the most common
Candida
isolate,
Candida glabrata
accounts for approximately 15 to 20% of all
Candida
infections in the United States. In this study we used immunosuppressed mice infected with
C. glabrata
to investigate the efficacy of liposomal amphotericin B alone or in combination with the echinocandin caspofungin or micafungin. For monotherapy, mice were given six daily doses of liposomal amphotericin B (3 to 20 mg/kg of body weight), caspofungin (1 to 5 mg/kg), or micafungin (2.5 to 10 mg/kg). With concomitant therapy, mice received liposomal amphotericin B (7.5 mg/kg) in addition to caspofungin (2.5 mg/kg) or micafungin (2.5 mg/kg) for 6 days. For sequential therapy, liposomal amphotericin B was administered on days 1 to 3 and caspofungin or micafungin was given on days 4 to 6; conversely, caspofungin or micafungin was administered on days 1 to 3 and liposomal amphotericin B was given on days 4 to 6. Efficacy was based on the number of CFU per gram of kidney 21 days postchallenge. Monotherapy with liposomal amphotericin B (7.5 to 20 mg/kg) was significantly more effective than no drug treatment (control group) (
P
< 0.05) and demonstrated a dose-dependent response, with 20 mg/kg lowering the CFU/g from 6.3 to 4.2 (significantly different from the value for the control group [
P
< 0.001]). Monotherapy with all echinocandin doses lowered the CFU/g from 6.0 to 6.4 to 2.7 to 3.3 (significantly different from the value for the control group [
P
< 0.001]) with no dose-dependent response. Complete clearance of infection could be achieved only when liposomal amphotericin B was given either concomitantly with caspofungin or micafungin or if liposomal amphotericin B was given sequentially with caspofungin. In conclusion, the combination of liposomal amphotericin B with an echinocandin markedly improved the therapeutic outcome in murine
C. glabrata
systemic infection.
Optimization of Meropenem Minimum Concentration/MIC Ratio To Suppress In Vitro Resistance of
Pseudomonas aeruginosa
Authors: Tam Vincent H. , Schilling Amy N. , Neshat Shadi , Poole Keith , Melnick David A. , Coyle Elizabeth A. 
Published: November 2005

ABSTRACT

Suppression of resistance in a dense
Pseudomonas aeruginosa
population has previously been shown with optimized quinolone exposures. However, the relevance to β-lactams is unknown. We investigated the bactericidal activity of meropenem and its propensity to suppress
P. aeruginosa
resistance in an in vitro hollow-fiber infection model (HFIM). Two isogenic strains of
P. aeruginosa
(wild type and an AmpC stably derepressed mutant [MIC = 1 mg/liter]) were used. An HFIM inoculated with approximately 1 × 10
8
CFU/ml of bacteria was subjected to various meropenem exposures. Maintenance doses were given every 8 h to simulate the maximum concentration achieved after a 1-g dose in all regimens, but escalating unbound minimum concentrations (
C
mi
n
s) were simulated with different clearances. Serial samples were obtained over 5 days to quantify the meropenem concentrations, the total bacterial population, and subpopulations with reduced susceptibilities to meropenem (>3× the MIC). For both strains, a significant bacterial burden reduction was seen with all regimens at 24 h. Regrowth was apparent after 3 days, with the
C
min
/MIC ratio being ≤1.7 (time above the MIC, 100%). Selective amplification of subpopulations with reduced susceptibilities to meropenem was suppressed with a
C
min
/MIC of ≥6.2 or by adding tobramycin to meropenem (
C
min
/MIC = 1.7). Investigations that were longer than 24 h and that used high inocula may be necessary to fully evaluate the relationship between drug exposures and the likelihood of resistance suppression. These results suggest that the
C
min
/MIC of meropenem can be optimized to suppress the emergence of non-plasmid-mediated
P. aeruginosa
resistance. Our in vitro data support the use of an extended duration of meropenem infusion for the treatment of severe nosocomial infections in combination with an aminoglycoside.
Antimalarial Activities of New Pyrrolo[3,2-f]Quinazoline-1,3-Diamine Derivatives
Authors: Guan Jian , Zhang Quan , O'Neil Michael , Obaldia Nicanor , Ager Arba , Gerena Lucia , Lin Ai J. 
Published: November 2005

ABSTRACT

WR227825 is an antimalarial pyrroloquinazolinediamine derivative with a high potency but a low therapeutic index. A series of carbamate, carboxamide, succinimide, and alkylamine derivatives of WR227825 were prepared to search for compounds with an improved therapeutic index. The new acetamides and imide showed potent cell growth inhibition against four clones of
Plasmodium falciparum
(D-6, RCS, W-2, and TM91C235), with a 50% inhibitory concentration of ∼0.01 ng/ml, and were highly active against
Plasmodium berghei
, with 100% cure at doses from <0.1 mg/kg of body weight to 220 mg/kg. The carbamates and alkyl derivatives, however, showed weak activity against
Plasmodium falciparum
cell growth but were highly efficacious in tests against
P. berghei
by the Thompson test. The best compounds, bis-ethylcarbamate (compound 2a) and tetra-acetamide (3a) derivatives, further demonstrated high potency against the sporozoite
Plasmodium yoelii
in mice and
P. falciparum
and
Plasmodium vivax
in aotus monkeys. Against the AMRU-1 strain of
P. vivax
, which has four dihydrofolate reductase mutations and is highly resistant to antifolates, tetra-acetamide 3a cured the monkeys at doses of 1 and 3 mg/kg. Compound 2a cured only one out of two monkeys at 3 mg/kg. The results indicated that the new derivatives 2a and 3a not only have retained/improved the antimalarial efficacy of the parent compound WR227825 but also were less toxic to the animals used in the tests.
Antimicrobial Activities and Structures of Two Linear Cationic Peptide Families with Various Amphipathic β-Sheet and α-Helical Potentials
Authors: Jin Yi , Hammer Janet , Pate Michelle , Zhang Yu , Zhu Fang , Zmuda Erik , Blazyk Jack 
Published: November 2005

ABSTRACT
Many naturally occurring antimicrobial peptides comprise cationic linear sequences with the potential to adopt an amphipathic α-helical conformation. We designed a linear 18-residue peptide that adopted an amphipathic β-sheet structure when it was bound to lipids. In comparison to a 21-residue amphipathic α-helical peptide of equal charge and hydrophobicity, this peptide possessed more similar antimicrobial activity and greater selectivity in binding to and inducing leakage in vesicles composed of bacterial membrane lipids than vesicles composed of mammalian membrane lipids (J. Blazyk, R. Weigand, J. Klein, J. Hammer, R. M. Epand, R. F. Epand, W. L. Maloy, and U. P. Kari, J. Biol. Chem. 276:27899-27906, 2001). Here, we compare two systematically designed families of linear cationic peptides to evaluate the importance of amphipathicity for determination of antimicrobial activity. Each peptide contains six lysine residues and is amidated at the carboxyl terminus. The first family consists of five peptides with various capacities to form amphipathic β-sheet structures. The second family consists of six peptides with various potentials to form amphipathic α helices. Only those peptides that can form a highly amphipathic structure (either a β sheet or an α helix) possessed significant antimicrobial activities. Striking differences in the abilities to bind to and induce leakage in membranes and lipid vesicles were observed for the two families. Overall, the amphipathic β-sheet peptides are less lytic than their amphipathic α-helical counterparts, particularly toward membranes containing phosphatidylcholine, a lipid commonly found in mammalian plasma membranes. Thus, it appears that antimicrobial peptides that can form an amphipathic β-sheet conformation may offer a selective advantage in targeting bacterial cells.
Comparison of the Fungicidal Activities of Caspofungin and Amphotericin B against
Candida glabrata
Authors: Barchiesi Francesco , Spreghini Elisabetta , Tomassetti Serena , Arzeni Daniela , Giannini Daniele , Scalise Giorgio 
Published: November 2005

ABSTRACT

We investigated the fungicidal activity of caspofungin (CAS) and amphotericin B (AMB) against 16 clinical isolates of
Candida glabrata
. The minimum fungicidal concentrations (MFCs) of CAS were similar to those of AMB, ranging from 2.0 to >8.0 μg/ml. Time-kill assays performed on selected isolates showed that AMB was fungicidal at concentrations four times the MIC while CAS was not. A neutropenic-mouse model of disseminated infection was utilized to determine the residual fungal kidney burden. While doses as low as 0.3 and 1 mg/kg of body weight/day of CAS and AMB, respectively, were effective at reducing the counts with respect to controls, organ sterilization was reached when both drugs were administered at 5 mg/kg/day. Our study reveals that, similar to AMB, CAS has the potential for a fungicidal effect in vivo against this difficult-to-treat fungal pathogen.
Molecular Characterization of Pneumococci with Efflux-Mediated Erythromycin Resistance and Identification of a Novel
mef
Gene Subclass,
mef
(I)
Authors: Cochetti Ileana , Vecchi Manuela , Mingoia Marina , Tili Emily , Catania Maria R. , Manzin Aldo , Varaldo Pietro E. , Montanari Maria Pia 
Published: November 2005

ABSTRACT

The molecular genetics of macrolide resistance were analyzed in 49 clinical pneumococci (including an “atypical” bile-insoluble strain currently assigned to the new species
Streptococcus pseudopneumoniae
) with efflux-mediated erythromycin resistance (M phenotype). All test strains had the
mef
gene, identified as
mef
(A) in 30 isolates and
mef
(E) in 19 isolates (including the
S. pseudopneumoniae
strain) on the basis of PCR-restriction fragment length polymorphism analysis. Twenty-eight of the 30
mef
(A) isolates shared a pulsed-field gel electrophoresis (PFGE) type corresponding to the England
14
-9 clone. Of those isolates, 27 (20 belonging to serotype 14) yielded multilocus sequence type ST9, and one isolate yielded a new sequence type. The remaining two
mef
(A) isolates had different PFGE types and yielded an ST9 type and a new sequence type. Far greater heterogeneity was displayed by the 19
mef
(E) isolates, which fell into 11 PFGE types, 12 serotypes (though not serotype 14), and 12 sequence types (including two new ones and an undetermined type for the
S. pseudopneumoniae
strain). In all
mef
(A) pneumococci, the
mef
element was a regular Tn
1207.1
transposon, whereas of the
mef
(E) isolates, 17 carried the mega element and 2 exhibited a previously unreported organization, with no PCR evidence of the other open reading frames of mega. The
mef
gene of these two isolates, which did not match with the
mef
(E) gene of the mega element (93.6% homology) and which exhibited comparable homology (91.4%) to the
mef
(A) gene of the Tn
1207.1
transposon, was identified as a novel
mef
gene variant and was designated
mef
(I). While penicillin-nonsusceptible isolates (three resistant isolates and one intermediate isolate) were all
mef
(E) strains, tetracycline resistance was also detected in three
mef
(A) isolates, due to the
tet
(M) gene carried by a Tn
916
-like transposon. A similar mechanism accounted for resistance in four of the five tetracycline-resistant isolates carrying
mef
(E), in three of which mega was inserted in the Tn
916
-like transposon, giving rise to the composite element Tn
2009
. In the fifth
mef
(E)-positive tetracycline-resistant isolate (the
S. pseudopneumoniae
strain), tetracycline resistance was due to the presence of the
tet
(O) gene, apparently unlinked to
mef
(E).
Pharmacodynamic Model To Describe the Concentration-Dependent Selection of Cefotaxime-ResistantEscherichia coli
Authors: Olofsson Sara K. , Geli Patricia , Andersson Dan I. , Cars Otto 
Published: November 2005

ABSTRACTAntibiotic dosing regimens may vary in their capacity to select mutants. Our hypothesis was that selection of a more resistant bacterial subpopulation would increase with the time within a selective window (SW), i.e., when drug concentrations fall between the MICs of two strains. An in vitro kinetic model was used to study the selection of twoEscherichia colistrains with different susceptibilities to cefotaxime. The bacterial mixtures were exposed to cefotaxime for 24 h and SWs of 1, 2, 4, 8, and 12 h. A mathematical model was developed that described the selection of preexisting and newborn mutants and the post-MIC effect (PME) as functions of pharmacokinetic parameters. Our main conclusions were as follows: (i) the selection between preexisting mutants increased with the time within the SW; (ii) the emergence and selection of newborn mutants increased with the time within the SW (with a short time, only 4% of the preexisting mutants were replaced by newborn mutants, compared to the longest times, where 100% were replaced); and (iii) PME increased with the area under the concentration-time curve (AUC) and was slightly more pronounced with a long elimination half-life (T1/2) than with a shortT1/2situation, when AUC is fixed. We showed that, in a dynamic competition between strains with different levels of resistance, the appearance of newborn high-level resistant mutants from the parental strains and the PME can strongly affect the outcome of the selection and that pharmacodynamic models can be used to predict the outcome of resistance development.
Antichagasic Activity of Komaroviquinone Is Due to Generation of Reactive Oxygen Species Catalyzed by
Trypanosoma cruzi
Old Yellow Enzyme
Authors: Uchiyama Nahoko , Kabututu Zakayi , Kubata Bruno K. , Kiuchi Fumiyuki , Ito Michiho , Nakajima-Shimada Junko , Aoki Takashi , Ohkubo Kei , Fukuzumi Shunichi , Martin Samuel K. , Honda Gisho , Urade Yoshihiro 
Published: November 2005

ABSTRACT

A novel potent trypanocidal diterpene, komaroviquinone, was reduced by
Trypanosoma cruzi
old yellow enzyme (TcOYE) to its semiquinone radical. The reductase activity in trypanosome lysates was completely immunoabsorbed by anti-TcOYE antibody. Since TcOYE is expressed throughout the
T. cruzi
life cycle, komaroviquinone is an interesting candidate for developing new antichagasic drugs.
Assessing the In Vitro Effectiveness of Antimicrobials against
Mycoplasma mycoides
subsp.
mycoides
Small-Colony Type To Reduce Contagious Bovine Pleuropneumonia Infection
Authors: Ayling R. D. , Bisgaard-Frantzen S. , March J. B. , Godinho K. , Nicholas R. A. J. 
Published: November 2005

ABSTRACT

In vitro minimum inhibitory concentrations were determined for 21 antimicrobials against 41 isolates of
Mycoplasma mycoides
subsp.
mycoides
small-colony type, the cause of contagious bovine pleuropneumonia. Of the antimicrobials used most widely in Africa, oxytetracycline and tilmicosin were effective, while the isolates were resistant to tylosin. These results provide a baseline for monitoring antimicrobial resistance.
Cloning and Functional Analysis of the Gene Encoding the 33- to 36-Kilodalton Outer Membrane Protein Associated with Carbapenem Resistance in
Acinetobacter baumannii
Authors: Tomás Maria del Mar , Beceiro Alejandro , Pérez Astrid , Velasco David , Moure Rita , Villanueva Rosa , Martínez-Beltrán Jesús , Bou Germán 
Published: November 2005

ABSTRACT

We investigated a multiresistant strain of
Acinetobacter baumannii
isolated in our hospital. Analysis of the N-terminal peptide sequence of the outer membrane proteins (OMPs) purified from the strain allowed us to clone and sequence the nucleotides of the gene encoding the 33- to 36-kDa OMP associated with carbapenem resistance in
A. baumannii
High Rate of Resistance to Quinupristin-Dalfopristin in
Enterococcus faecium
Clinical Isolates from Korea
Authors: Oh Won Sup , Ko Kwan Soo , Song Jae-Hoon , Lee Mi Young , Park Sulhee , Peck Kyong Ran , Lee Nam Yong , Kim Choon-Kwan , Lee Hyuck , Kim Shin-Woo , Chang Hyun-Ha , Kim Yeon-Sook , Jung Sook-In , Son Jun Seong , Yeom Joon-Sup , Ki Hyun Kyun , Woo Gun-Jo 
Published: November 2005

ABSTRACT

We tested the in vitro susceptibilities of 603 enterococcal isolates from eight tertiary-care hospitals in Korea. The quinupristin-dalfopristin resistance rate in
Enterococcus faecium
was very high (25 isolates, 10.0%). It was suggested that both clonal spread and the sporadic emergence of quinupristin-dalfopristin-resistant isolates may explain the high prevalence of quinupristin-dalfopristin resistance in Korea.
Turbulence and Gravity Waves within an Upper-Level Front
Authors: Koch Steven E. , Jamison Brian D. , Lu Chungu , Smith Tracy L. , Tollerud Edward I. , Girz Cecilia , Wang Ning , Lane Todd P. , Shapiro Melvyn A. , Parrish David D. , Cooper Owen R. 
Published: November 2005

Abstract
High-resolution dropwindsonde and in-flight measurements collected by a research aircraft during the Severe Clear-Air Turbulence Colliding with Aircraft Traffic (SCATCAT) experiment and simulations from numerical models are analyzed for a clear-air turbulence event associated with an intense upper-level jet/frontal system. Spectral, wavelet, and structure function analyses performed with the 25-Hz in situ data are used to investigate the relationship between gravity waves and turbulence. Mesoscale dynamics are analyzed with the 20-km hydrostatic Rapid Update Cycle (RUC) model and a nested 1-km simulation with the nonhydrostatic Clark–Hall (CH) cloud-scale model.
Turbulence occurred in association with a wide spectrum of upward propagating gravity waves above the jet core. Inertia–gravity waves were generated within a region of unbalanced frontogenesis in the vicinity of a complex tropopause fold. Turbulent kinetic energy fields forecast by the RUC and CH models displayed a strongly banded appearance associated with these mesoscale gravity waves (horizontal wavelengths of ∼120–216 km). Smaller-scale gravity wave packets (horizontal wavelengths of 1–20 km) within the mesoscale wave field perturbed the background wind shear and stability, promoting the development of bands of reduced Richardson number conducive to the generation of turbulence. The wavelet analysis revealed that brief episodes of high turbulent energy were closely associated with gravity wave occurrences. Structure function analysis provided evidence that turbulence was most strongly forced at a horizontal scale of 700 m.
Fluctuations in ozone measured by the aircraft correlated highly with potential temperature fluctuations and the occurrence of turbulent patches at altitudes just above the jet core, but not at higher flight levels, even though the ozone fluctuations were much larger aloft. These results suggest the existence of remnant “fossil turbulence” from earlier events at higher levels, and that ozone cannot be used as a substitute for more direct measures of turbulence. The findings here do suggest that automated turbulence forecasting algorithms should include some reliable measure of gravity wave activity.