bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallization and preliminary X-ray analysis of the catalytic core of the alkylhydroperoxide reductase component AhpF from Escherichia coli
Authors: Bieger Boris , Essen Lars-Oliver 
Published: July 2002

Alkylhydroperoxide reductases (AhpR, E.C. 1.6.4.x) are essential for the oxygen tolerance of aerobic organisms, converting otherwise toxic hydroperoxides of lipids or nucleic acids to their corresponding alcohols. The AhpF component (521 amino-acid residues, 56.2 kDa) belongs to the family of pyridine nucleotide–disulfide oxidoreductases and channels electrons from NAD(P)H via a series of disulfides towards the AhpC component, which finally reduces the hydroperoxide substrates. Crystals of the proteolytically truncated AhpF component (residues Asn208–Ala521) of the alkyl hydroperoxide reductase from Escherichia coli were grown under oxidizing conditions. The crystals belong to space group P3221, with unit-cell parameters a = 60.4, c = 171.8 Å. X-ray diffraction data were collected to 1.9 Å resolution using synchrotron radiation. A molecular-replacement solution was found using the structure of thioredoxin reductase from Arabidopsis thaliana as a search model.
Angular Resolution of Parallel Foils on a Synchrotron Powder Diffractometer
Authors: Roberts M. A. , Tang C. C. 
Published: July 2002

In an attempt to improve the resolution in flat-plate diffraction geometry, a new set of parallel foils, 100 µm spacing, 365 mm long with an aperture of 20 × 20 mm2, has been commissioned. The study was carried out using the two-circle diffractometer of station 2.3 at the SRS. In order to properly quantify the improvements, a detailed and comparative study of the instrumental resolution using the new and existing foils, of 200 µm spacing, is reported. A number of cubic materials, BaF2, Si and CeO2, that are known to show well defined Bragg peaks over the full 2θ angular range available, were investigated.
Activities of LY333328 and Vancomycin Administered Alone or in Combination with Gentamicin against Three Strains of Vancomycin-Intermediate
Staphylococcus aureus
in an In Vitro Pharmacodynamic Infection Model
Authors: Aeschlimann Jeffrey R. , Allen George P. , Hershberger Ellie , Rybak Michael J. 
Published: July 2002

ABSTRACT

Staphylococcus aureus
with intermediate glycopeptide susceptibility (glycopeptide-intermediate
S. aureus
[GISA]) has been isolated from patients with apparent therapy failures. We studied the killing activity of vancomycin over a range of simulated conventional doses (1 to 1.5 g every 12 h) against three of these GISA strains in an in vitro pharmacodynamic infection model. We also studied the activity of a new glycopeptide (LY333328) at a simulated dose of 3 mg/kg of body weight every 24 h or 5 mg/kg every 24 h, as well as the potential for vancomycin and gentamicin synergy against these GISA strains. Four doses of vancomycin with or without gentamicin or two doses of LY333328 were administered over the 48-h study period. The vancomycin and LY333328 MICs and minimal bactericidal concentrations (MBCs) for the three GISA strains (strains 14379, 992, and Mu50) were 8 and 8 μg/ml and 1 and 2 μg/ml, respectively, for GISA 14379, 6 and 6 μg/ml and 1 and 1 μg/ml, respectively, for GISA 992, and 8 and 12 μg/ml and 2 and 8 μg/ml, respectively, for GISA Mu50. Vancomycin and LY333328 MICs and MBCs were 0.75 and 1.0 μg/ml and 1 and 1 μg/ml, respectively for a vancomycin-susceptible comparator strain (methicillin-resistant
S. aureus
[MRSA] 494). The addition of albumin to the growth medium increased the LY333328 MICs and MBCs approximately 8- to 16-fold. Vancomycin was bacteriostatic against the three GISA strains at doses of 1, 1.125, and 1.25 g every 12 h. Vancomycin was bactericidal at the dose of 1.5 g every 12 h against all strains; bactericidal activity occurred against the GISA strains at 8- to 10-fold lower ratios of the peak concentration to the MIC and the area under the concentration-time curve from time zero to 24 h (AUC
0–24
) to the MIC compared to those for the vancomycin-sensitive control strain. Overall, vancomycin activity was significantly correlated with the AUC
0–24
(
R
2
= 0.79;
P
< 0.001) by multiple stepwise regression analyses. The addition of gentamicin did not significantly affect killing activity against any strain. LY333328 was bactericidal against GISA strains 14379 and 992 and against MRSA 494 only with the 5-mg/kg/day dose simulations. The higher dose of LY333328 also prevented regrowth over the 48-h experiments for all strains tested. Higher doses of vancomycin (1.5 g every 12 h) and LY333328 (5 mg/kg every 24 h) may represent potential treatment options for infections caused by GISA strains.
Absolute Bioavailability and Disposition of (−) and (+) 2′-Deoxy- 3′-Oxa-4′-Thiocytidine (dOTC) following Single Intravenous and Oral Doses of Racemic dOTC in Humans
Authors: Smith Patrick F. , Forrest Alan , Ballow Charles H. , Martin David E. , Proulx Louise 
Published: July 2002

ABSTRACT

The purpose of this study was to characterize the pharmacokinetics and determine the absolute bioavailability of 2′-deoxy-3′-oxa-4′-thiocytidine (dOTC) (BCH-10652), a novel nucleoside analogue reverse transcriptase inhibitor, in humans. dOTC belongs to the 4′-thio heterosubstituted class of compounds and is a 1:1 mixture of its two enantiomers, (−) and (+) dOTC. Twelve healthy adult male volunteers each received oral (800-mg) and intravenous (100-mg) doses of dOTC in two study periods separated by at least 7 days. Sixteen plasma samples were obtained over 72 h and assayed for (−) and (+) dOTC, and the resultant data fit by candidate pharmacokinetic models. Data were weighted by the fitted inverse of the observation variance; model discrimination was by AIC. The pharmacokinetic model was a linear, three compartment model, with absorption occurring during one to three first-order input phases, each following a fitted lag time. The model goodness-of-fit was excellent;
r
2
ranged from 0.995 to 1.0. The mean absolute bioavailabilities of (+) and (−) dOTC were 77.2% (coefficient of variation [given as a percentage] [CV%], 14) and 80.7% (CV%, 15), respectively. The median steady-state volume of distribution for (+) dOTC, 74.7 (CV%, 19.2) liters/65 kg, was greater than that for (−) dOTC, 51.7 (CV%, 16.7) liters/65 kg (
P
< 0.05). The median total clearance of (+) dOTC was less than that of (−) dOTC, 11.7 (CV%, 17.3) versus 15.4 (CV%, 18.6) liters/h/65 kg, respectively (
P
< 0.05). The intersubject variability of these parameters was very low. The median terminal half-life of (+) dOTC was 18.0 (CV%, 31.5) h, significantly longer than the 6.8 (CV%, 69.9) h observed for (−) dOTC (
P
< 0.01). No serious adverse events were reported during the study. These results suggest that dOTC is well absorbed, widely distributed, and well tolerated. The terminal half-lives indicate that dosing intervals of 12 to 24 h would be reasonable.
Monotherapy with a Broad-Spectrum Beta-Lactam Is as Effective as Its Combination with an Aminoglycoside in Treatment of Severe Generalized Peritonitis: a Multicenter Randomized Controlled Trial
Authors: Dupont H. , Carbon C. , Carlet J. 
Published: July 2002

ABSTRACT
In a randomized trial conducted in 35 centers, we compared the clinical efficacy and safety of piperacillin plus tazobactam (TAZ) alone (monotherapy [MT]) versus those of TAZ combined with amikacin (AMK) (combined therapy [CT]) for the treatment of severe generalized peritonitis (SGP). Primary analysis consisted of blind assessment by an independent committee of the failure rate 30 days after the end of treatment in the modified intent-to-treat (ITT) analysis (mITT) population. Of the 241 patients with suspected SGP randomized into the study, 227 were eligible for ITT analysis, including 204 (99 in the MT group and 105 in the CT group) with confirmed SGP (mITT population). A total of 159 patients were eligible for per-protocol (PP) analysis. The clinical failure rates were equivalent in the mITT and PP populations (MT versus CT): 56 versus 52%, (odds ratio [OR] 0.87, 90% confidence interval [CI] = 0.6 to 1.27) for mITT and 49 versus 49% (OR = 1.03, 90% CI = 0.67 to 1.59) for PP analysis. Mortality rates (ITT population, 19%; PP population, 21%) and overall adverse event rates (ITT population, 55%; PP population, 54%) were also similar. Six patients (three in MT group and three in the CT group) developed acute renal failure. In conclusion, the addition of AMK to TAZ does not seem to be necessary for the treatment of SGP, even after adjustment for the simplified acute physiology score (SAPS II) and type of SGP.
Antimycobacterial Activities of Novel Levofloxacin Analogues
Authors: Kawakami Katsuhiro , Namba Kenji , Tanaka Mayumi , Matsuhashi Norikazu , Sato Kenichi , Takemura Makoto 
Published: July 2002

ABSTRACT

In order to investigate structure-activity relationships between antimycobacterial activities and basic substituents at the C-10 position of levofloxacin (LVFX), we synthesized a series of pyridobenzoxazine derivatives by replacement of the
N
-methylpiperazinyl group of LVFX with various basic substituents. A compound with a 3-aminopyrrolidinyl group had one-half the activity of LVFX against
Mycobacterium avium
,
M. intracellulare
, and
M. tuberculosis
. Mono- and dimethylation of the 3-amino moiety of the pyrrolidinyl group increased the activities against
M. avium
and
M. intracellulare
but not those against
M. tuberculosis
. On the other hand, dialkylation at the C-4 position of the 3-aminopyrrolidinyl group enhanced the activities against
M. avium
,
M. intracellulare
, and
M. tuberculosis
. Thus, introduction of an
N
-alkyl or a
C
-alkyl group(s) into the 3-aminopyrrolidinyl group may contribute to an increase in potency against
M. avium
,
M. intracellulare
, and/or
M. tuberculosis
, probably through elevation of the lipophilicity. However, among the compounds synthesized, compound VII, which was a 2,8-diazabicyclo[4.3.0]nonanyl derivative with relatively low lipophilicity, showed the most potent activity against mycobacterial species: the activity was 4- to 32-fold more potent than that of LVFX and two to four times as potent as that of gatifloxacin. These results suggested that an increase in the lipophilicity of LVFX analogues in part contributed to enhancement of antimycobacterial activities but that lipophilicity of the compound was not a critical factor affecting the potency.
Pharmacokinetics-Pharmacodynamics of a Sordarin Derivative (GM 237354) in a Murine Model of Lethal Candidiasis
Authors: Aviles P. , Falcoz C. , San Roman R. , Gargallo-Viola D. 
Published: July 2002

ABSTRACT

Sordarins are a new class of antifungal agents which selectively inhibit fungal protein synthesis (FPS) by impairing the function of elongation factor 2. The present study investigates possible correlations between sordarin pharmacokinetic (PK) properties and therapeutic efficacy, based on a murine model of invasive systemic candidiasis, and provides a rationale for dose selection in the first study of efficacy in humans. A significant correlation between PK parameters and the in vivo activity of GM 237354, taken as a representative FPS inhibitor, was demonstrated in a murine model of lethal systemic candidiasis. Area under the concentration-time curve (AUC) and maximum concentration of drug in serum (
C
max
) over 24 h were determined after a single GM 237354 subcutaneous (s.c.) dose (50 mg/kg of body weight) in healthy animals (no significant PK changes with infection were observed for other sordarin derivatives). These results have been used to simulate PK profiles obtained after several doses and/or schedules in animal therapy. A PK-pharmacodynamic (PD) parameter such as the time that serum drug concentrations remain above the MIC (
t
> MIC) was also determined. Treatment efficacies were evaluated in terms of the area under the survival time curve (AUSTC), using Kaplan-Meier survival analysis and in terms of kidney fungal burden (log CFU/gram) after s.c. doses of 2.5, 5, 10, 20, and 40 mg/kg every 4, 8, or 12 h (corresponding to total daily doses of 5 to 240 mg/kg). The results show all treatments to significantly prolong survival versus that of infected and nontreated controls (
P
< 0.05). Relationships between simulated PK and PK-PD parameters and efficacy were explored. A good correlation independent of the dosing interval was observed with AUC (but not
C
max
or
t
> MIC) and both AUSTC and kidney burden. Following repeated dosing every 8 h, AUC
50
(AUC at which 50% of the maximum therapeutic efficacy is obtained) was estimated as 21.7 and 37.1 μg · h/ml (total concentrations) for AUSTC and kidney burden using a sigmoid
E
max
and an inhibitory sigmoid
E
max
PK-PD model, respectively. For an efficacy target of 90% survival, AUC was predicted as 67 μg · h/ml. We conclude that the PK-PD approach is useful for evaluating relationships between PK parameters and efficacy in antifungal research. Moreover, the results obtained with this approach could be successfully applied to clinical studies.
In Vitro Activities of Six Fluoroquinolones against 250 Clinical Isolates of
Mycobacterium tuberculosis
Susceptible or Resistant to First-Line Antituberculosis Drugs
Authors: Ruiz-Serrano María Jesús , Alcalá Luis , Martínez Lucía , Díaz Marisol , Marín Mercedes , González-Abad María José , Bouza Emilio 
Published: July 2002

ABSTRACT

Two hundred fifty isolates of
Mycobacterium tuberculosis
were evaluated for susceptibility to ciprofloxacin, ofloxacin, levofloxacin, grepafloxacin, trovafloxacin, and gemifloxacin (SB-265805). Levofloxacin, ciprofloxacin, and grepafloxacin showed the greatest activity (MIC for 90% of strains tested [MIC
90
] 1 μg/ml), although ofloxacin also showed good activity, with an MIC
90
of 2 μg/ml. Trovafloxacin and gemifloxacin showed lower in vitro activity, with MIC
90
s of 64 and 8 μg/ml, respectively.
Inhibitory Effects of Plant Polyphenoloxidase on Colonization Factors of
Streptococcus sobrinus
6715
Authors: Cowan M. M. , Horst E. A. , Luengpailin S. , Doyle R. J. 
Published: July 2002

ABSTRACT

Exogenously added polyphenoloxidase (EC
1.14.18.1
), an enzyme which oxidizes tyrosine residues and is commonly found in many dietary components, abolished the aggregation of
Streptococcus sobrinus
6715 by high-molecular-weight dextran. The enzyme decreased glucan-binding lectin and/or glucosyltransferase I activities.
Development and Validation of Limited-Sampling Strategies for Predicting Amoxicillin Pharmacokinetic and Pharmacodynamic Parameters
Authors: Suarez-Kurtz Guilherme , Ribeiro Frederico Mota , Vicente Flávio L. , Struchiner Claudio J. 
Published: July 2002

ABSTRACT

Amoxicillin plasma concentrations (
n
= 1,152) obtained from 48 healthy subjects in two bioequivalence studies were used to develop limited-sampling strategy (LSS) models for estimating the area under the concentration-time curve (AUC), the maximum concentration of drug in plasma (
C
max
), and the time interval of concentration above MIC susceptibility breakpoints in plasma (T>MIC). Each subject received 500-mg amoxicillin, as reference and test capsules or suspensions, and plasma concentrations were measured by a validated microbiological assay. Linear regression analysis and a “jack-knife” procedure revealed that three-point LSS models accurately estimated (
R
2
, 0.92; precision, <5.8%) the AUC from 0 h to infinity (AUC
0-∞
) of amoxicillin for the four formulations tested. Validation tests indicated that a three-point LSS model (1, 2, and 5 h) developed for the reference capsule formulation predicts the following accurately (
R
2
, 0.94 to 0.99): (i) the individual AUC
0-∞
for the test capsule formulation in the same subjects, (ii) the individual AUC
0-∞
for both reference and test suspensions in 24 other subjects, and (iii) the average AUC
0-∞
following single oral doses (250 to 1,000 mg) of various amoxicillin formulations in 11 previously published studies. A linear regression equation was derived, using the same sampling time points of the LSS model for the AUC
0-∞
, but using different coefficients and intercept, for estimating
C
max
. Bioequivalence assessments based on LSS-derived AUC
0-∞
's and
C
max
's provided results similar to those obtained using the original values for these parameters. Finally, two-point LSS models (
R
2
= 0.86 to 0.95) were developed for T>MICs of 0.25 or 2.0 μg/ml, which are representative of microorganisms susceptible and resistant to amoxicillin.
Identification and Characterization of New Inhibitors of the
Escherichia coli
MurA Enzyme
Authors: Baum Ellen Z. , Montenegro Deborah A. , Licata Lisa , Turchi Ignatius , Webb Glenda C. , Foleno Barbara D. , Bush Karen 
Published: July 2002

ABSTRACT

The bacterial enzyme MurA catalyzes the transfer of enolpyruvate from phosphoenolpyruvate (PEP) to uridine diphospho-
N
-acetylglucosamine (UNAG), which is the first committed step of bacterial cell wall biosynthesis. From high-throughput screening of a chemical library, three novel inhibitors of the
Escherichia coli
MurA enzyme were identified: the cyclic disulfide RWJ-3981, the purine analog RWJ-140998, and the pyrazolopyrimidine RWJ-110192. When MurA was preincubated with inhibitor, followed by addition of UNAG and PEP, the 50% inhibitory concentrations (IC
50
s) were 0.2 to 0.9 μM, compared to 8.8 μM for the known MurA inhibitor, fosfomycin. The three compounds exhibited MICs of 4 to 32 μg/ml against
Staphylococcus aureus
; however, the inhibition of DNA, RNA, and protein synthesis in addition to peptidoglycan synthesis by all three inhibitors indicated that antibacterial activity was not due specifically to MurA inhibition. The presence of UNAG during the MurA and inhibitor preincubation lowered the IC
50
at least fivefold, suggesting that, like fosfomycin, the three compounds may interact with the enzyme in a specific fashion that is enhanced by UNAG. Ultrafiltration and mass spectrometry experiments suggested that the compounds were tightly, but not covalently, associated with MurA. Molecular modeling studies demonstrated that the compounds could fit into the site occupied by fosfomycin; exposure of MurA to each compound reduced the labeling of MurA by tritiated fosfomycin. Taken together, the evidence indicates that these inhibitors may bind noncovalently to the MurA enzyme, at or near the site where fosfomycin binds.
Eagle-Type Methicillin Resistance: New Phenotype of High Methicillin Resistance under
mec
Regulator Gene Control
Authors: Kondo Noriko , Kuwahara-Arai Kyoko , Kuroda-Murakami Hiroko , Tateda-Suzuki Eiko , Hiramatsu Keiichi 
Published: July 2002

ABSTRACT

We report a novel phenotype of methicillin resistance, designated “Eagle-type” resistance, which is characteristic in its resistance to high concentrations of methicillin (64 to 512 μg/ml) and susceptibility to low concentrations of methicillin (2 to 16 μg/ml). The type of resistance was expressed in mutant strains selected with high concentrations (e.g., 128 to 512 μg/ml) of methicillin from the pre-methicillin-resistant
Staphylococcus aureus
strain N315, whose
mecA
gene transcription is strongly repressed by the
mecI
gene-encoded repressor protein MecI. The Eagle-type mutant strains harbored no mutation in the
mecI
gene or in the operator region of
mecA
gene to which MecI repressor is supposed to bind. In the representative Eagle-type strain h4, repression of
mecA
gene transcription and penicillin-binding protein 2′ production were found to be released by exposing the cells to a high concentration (128 μg/ml) of methicillin but not to lower concentrations (1 and 8 μg/ml) of methicillin. The strain h4 expressed paradoxical susceptibility (Eagle effect) to the cytokilling activity of methicillin. Experimental deletion of
mecI
gene from the chromosome of h4 by
mecI
-specific gene substitution converted its Eagle-type resistance to homogeneously high methicillin resistance. We cloned two novel genes, designated
hmrA
and
hmrB
, from genomic library of h4, which conferred Eagle-type resistance to N315 when introduced into the cell in multiple copies. The genes were shown to confer homogeneous methicillin resistance to the heterogeneously methicillin-resistant strain LR5 when they were introduced into on multicopy plasmids. This result strongly indicated that the genetic alteration responsible for the expression of the Eagle phenotype is identical, or equivalent in its effect, to the genetic alteration underlying heterogeneous-to-homogeneous conversion of methicillin resistance in
S. aureus
.
In Vivo Efficacy of Trovafloxacin against
Bacteroides fragilis
in Mixed Infection with either
Escherichia coli
or a Vancomycin-Resistant Strain of
Enterococcus faecium
in an Established-Abscess Murine Model
Authors: Stearne Lorna E. T. , Gyssens Inge C. , Goessens Wil H. F. , Mouton Johan W. , Oyen Wim J. G. , van der Meer Jos W. M. , Verbrugh Henri A. 
Published: July 2002

ABSTRACT

The pharmacodynamic and pharmacokinetic properties of trovafloxacin were studied in a standardized murine model of established subcutaneous abscesses. Daily dosing regimens of 37.5 to 300 mg/kg every 8 h (q8h) or every 24 h (q24h) were started 3 days after inoculation with mixtures containing either
Bacteroides fragilis-Escherichia coli
-autoclaved cecal contents (ACC) or
B. fragilis
–vancomycin-resistant
Enterococcus faecium
(VREF)–ACC. Treatment was continued for 3 or 5 days. The efficacy of treatment was determined by the decrease in abscess bacterial counts and abscess weights, as well as by the reduction in inflammation (biodistribution of
99m
Tc-HYNIC immunoglobulin G) compared to saline-treated controls. Trovafloxacin showed a significant dose-response effect on the bacterial counts, weight, and inflammation of
B. fragilis-E. coli
abscesses after 3 and/or 5 days of treatment. A maximum 3.4 and 3.1 log
10
reduction in CFU/abscess in the respective
B. fragilis
and
E. coli
bacterial counts was attained after 5 days of treatment with daily doses of 300 mg/kg. The peak serum concentration was more predictive for effect than the area under the concentration-time curve. The
C
max
was the pharmacodynamic index most predictive for success, and the efficacy of the q24h regimens was significantly better than the q8h regimens. The antibiotic was ineffective against the VREF in mixed infection with
B. fragilis
, while the killing of the anaerobe in the same combination was significantly less than in the
E. coli
combination (
P
< 0.05). We conclude that this is a useful model for studying the activity of antimicrobials for the treatment of small (<1-cm), undrainable, mixed-infection abscesses. In addition, we have shown for the first time that a decrease in bacterial numbers also leads to a reduction in both abscess weight and inflammation.