bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discrimination of SHV β-Lactamase Genes by Restriction Site Insertion-PCR
Authors: Chanawong Aroonwadee , M'Zali Fatima Hannachi , Heritage John , Lulitanond Aroonlug , Hawkey Peter Michael 
Published: July 2002

ABSTRACT

Restriction site insertion-PCR (RSI-PCR) is a simple, rapid technique for detection of point mutations. This technique exploits primers with one to three base mismatches near the 3′ end to modulate a restriction site. We have developed this technique to identify described mutations of the
bla
SHV
genes for differentiation of SHV variants that cannot be distinguished easily by other techniques. To validate this method, eight standard strains were used, each producing a different SHV β-lactamase: SHV-1, SHV-2, SHV-3, SHV-4, SHV-5, SHV-6, SHV-8, and SHV-18. Mismatch primers were designed to detect mutations affecting amino acids at positions 8 (
Ssp
I), 179 (
Hin
fI), 205 (
Pst
I), 238 (Gly→Ala) (
Bsr
I), and 240 (
Nru
I) of
bla
SHV
genes. All amplimers of the
bla
SHV
genes used in this study yielded the predicted restriction endonuclease digestion products. In addition, this study also makes theoretical identification of
bla
SHV-6
,
bla
SHV-8
, and 12 novel
bla
SHV
variants using the PCR-restriction fragment length polymorphism (RFLP) technique possible. By using a combination of PCR-RFLP and RSI-PCR techniques, up to 27 SHV variants can now be distinguished rapidly and reliably. These simple techniques are readily applied to epidemiological studies of the SHV β-lactamases and may be extended to the characterisation of other resistance determinants.
Isolation of Rat Dihydrofolate Reductase Gene and Characterization of Recombinant Enzyme
Authors: Wang Yangzhou , Bruenn Jeremy A. , Queener Sherry F. , Cody Vivian 
Published: July 2002

ABSTRACT
While assays of many antifolate inhibitors for dihydrofolate reductase (DHFR) have been performed using rat DHFR as a target, neither the sequence nor the structure of rat DHFR is known. Here, we report the isolation of the rat DHFR gene through screening of a rat liver cDNA library. The rat liver DHFR gene has an open reading frame of 561 bp encoding a protein of 187 amino acids. Comparisons of the rat enzyme with those from other species indicate a high level of conservation at the primary sequence level and more so for the amino acid residues comprising the active site of the enzyme. Expression of the rat DHFR gene in bacteria produced a recombinant protein with high enzymatic activity. The recombinant protein also paralleled the human enzyme with respect to the inhibition by most of the antifolates tested with PT652 and PT653 showing a reversal in their patterns. Our results indicated that rat DHFR can be used as a model to study antifolate compounds as potential drug candidates. However, variations between rat and human DHFR enzymes, coupled with unique features in the inhibitors, could lead to the observed differences in enzyme sensitivity and selectivity.
Efficacies of ABT-773, a New Ketolide, against Experimental Bacterial Infections
Authors: Mitten M. J. , Meulbroek J. , Nukkala M. , Paige L. , Jarvis K. , Oleksijew A. , Tovcimak A. , Hernandez L. , Alder J. D. , Ewing P. , Or Y. S. , Ma Z. , Nilius A. M. , Mollison K. , Flamm R. K. 
Published: July 2002

ABSTRACT

ABT-773 is a novel ketolide effective against antibacterial-resistant respiratory tract pathogens. The pharmacokinetic profile of ABT-773 was studied in rats and consisted of a mean peak concentration in plasma of 1.07 μg/ml and an area under the concentration-time curve (AUC) of 12.03 μg · h/ml when the compound was delivered at a dose of 25 mg/kg of body weight. It concentrated in rat lung tissue, with a lung tissue-to-plasma ratio of 29 based on the AUC. In acute systemic infections in mice, ABT-773 showed efficacy against macrolide-susceptible strains of
Staphylococcus aureus
,
Streptococcus pneumoniae
,
S. pyogenes
, and
Listeria monocytogenes
. Additionally, ABT-773 improved the survival of mice infected with resistant
S. pneumoniae
containing either the
ermB
gene, the
mefE
gene, or altered penicillin binding protein genes. In a rat lung model of infection, ABT-773 demonstrated 50% effective doses lower than those of comparator macrolides when evaluated against the following strains of
S. pneumoniae
: a macrolide-lincosamide-streptogramin B-susceptible strain, an
ermB
strain, and an
mefE
strain
.
ABT-773 was also effective against
Haemophilus influenzae
lung infections in rats. Thus, ABT-773 may prove to be a useful new antibacterial agent for the treatment of respiratory tract infections.
Increased Glycan Chain Length Distribution and Decreased Susceptibility to Moenomycin in a Vancomycin-Resistant
Staphylococcus aureus
Mutant
Authors: Komatsuzawa Hitoshi , Ohta Kouji , Yamada Sakuo , Ehlert Kerstin , Labischinski Harald , Kajimura Junko , Fujiwara Tamaki , Sugai Motoyuki 
Published: July 2002

ABSTRACT

A vancomycin-resistant
Staphylococcus aureus
mutant, COL-VR1 (MIC, 16 μg/ml), was isolated from methicillin-resistant
S. aureus
COL by exposure to vancomycin. COL-VR1 also showed decreased susceptibility to teicoplanin (8-fold), methicillin (2-fold), macarbomycin (8-fold), and moenomycin (16-fold). Macarbomycin and moenomycin are thought to directly inhibit transglycosylase activity. Characterization of the mutant revealed a thickened cell wall and suppression of penicillin-induced lysis, although the amounts of the five penicillin-binding proteins (PBPs 1, 2, 3, 4, and 2′) and the profiles of peptidoglycan hydrolases were not altered. Analysis of muropeptide profile and glycan chain length distribution by reversed-phase high-pressure liquid chromatography revealed slightly decreased peptide cross-linking and an increased average glycan chain length compared to those of the parent. These results together suggest that a transglycosylase activity was enhanced in the mutant. This may represent a novel mechanism of glycopeptide resistance in
S. aureus
.
In Vitro Activity of Cephalosporin RWJ-54428 (MC-02479) against Multidrug-Resistant Gram-Positive Cocci
Authors: Johnson Alan P. , Warner Marina , Carter Michael , Livermore David M. 
Published: July 2002

ABSTRACT

RWJ-54428 (MC-02479) is a novel cephalosporin that binds to penicillin-binding protein (PBP) PBP 2′ (PBP 2a) of methicillin-resistant staphylococci. Its in vitro activity was assessed against 472 gram-positive cocci, largely selected as epidemiologically unrelated isolates with multidrug resistance. The MIC at which 50% of isolates are inhibited (MIC
50
) and MIC
90
of RWJ-54428 for methicillin-resistant
Staphylococcus aureus
(MRSA) were 1 and 2 μg/ml, respectively, whereas they were 0.5 and 0.5 μg/ml, respectively, for methicillin-susceptible
S. aureus
. The MIC
50
and MIC
90
were 1 and 4 μg/ml, respectively, for methicillin-resistant coagulase-negative staphylococci (MRCoNS), whereas they were 0.25 and 1 μg/ml, respectively, for methicillin-susceptible isolates. The highest MICs for MRSA and MRCoNS isolates were 2 and 4 μg/ml, respectively. The MIC
50
and MIC
90
of RWJ-54428 for
Enterococcus faecalis
were 0.5 and 1 μg/ml, respectively, but they were 4 and 8 μg/ml, respectively, for
Enterococcus faecium
. For penicillin-susceptible, -intermediate, and -resistant pneumococci, the MIC
90
s of RWJ-54428 were 0.03, 0.25, and 0.5 μg/ml, respectively, with the highest MIC for a pneumococcus being 1 μg/ml, recorded for a strain for which penicillin and cefotaxime MICs were 8 and 4 μg/ml. MICs for Lancefield group A, B, C, and G streptococci were ≤0.008 μg/ml; those for viridans group streptococci, including isolates not susceptible to penicillin, were from 0.015 to 0.5 μg/ml. RWJ-54428 did not select resistant mutants of MRSA or enterococci in challenge experiments and has the potential to be useful for the treatment of infections caused by gram-positive cocci.
Selection of Zone Size Interpretive Criteria for Disk Diffusion Susceptibility Tests of Three Antibiotics against
Streptococcus pneumoniae,
Using the New Guidelines of the National Committee for Clinical Laboratory Standards
Authors: Fuchs Peter C. , Barry Arthur L. , Brown Steven D. 
Published: July 2002

ABSTRACT

Disk diffusion and broth microdilution susceptibility tests were performed with cefotaxime, ceftriaxone, telithromycin, and erythromycin (control) against 407 selected isolates of
Streptococcus pneumoniae
. Scattergrams were prepared from the results of these tests, and the current NCCLS guidelines for setting disk diffusion test interpretive criteria were applied. Erythromycin zone diameter breakpoints were confirmed. Telithromycin interpretive criteria for the disk test could be easily set with acceptable discrepancy rates. For cefotaxime and ceftriaxone, the minor discrepancy rates for MICs in the intermediate category ± 1 dilution were far in excess of the acceptable 40% limit, i.e., 52 and 71%, respectively. We conclude that the 30-μg disk of these two drugs cannot be reliably used to test pneumococci.
Cleavable-Complex Formation by Wild-Type and Quinolone-Resistant
Streptococcus pneumoniae
Type II Topoisomerases Mediated by Gemifloxacin and Other Fluoroquinolones
Authors: Yague Genoveva , Morris Julia E. , Pan Xiao-Su , Gould Katherine A. , Fisher L. Mark 
Published: July 2002

ABSTRACT

Gemifloxacin is a recently developed fluoroquinolone with potent activity against
Streptococcus pneumoniae
. We show that the drug is more active than moxifloxacin, gatifloxacin, levofloxacin, and ciprofloxacin against
S. pneumoniae
strain 7785 (MICs, 0.03 to 0.06 μg/ml versus 0.25, 0.25, 1, and 1 to 2 μg/ml, respectively) and against isogenic quinolone-resistant
gyrA
-
parC
mutants (MICs, 0.5 to 1 μg/ml versus 2 to 4, 2 to 4, 16 to 32, and 64 μg/ml, respectively). Gemifloxacin was also the most potent agent against purified
S. pneumoniae
DNA gyrase and topoisomerase IV in both catalytic inhibition and DNA cleavage assays. The drug concentrations that inhibited DNA supercoiling or DNA decatenation by 50% (IC
50
s) were 5 to 10 and 2.5 to 5.0 μM, respectively. Ciprofloxacin and levofloxacin were some four- to eightfold less active against either enzyme; moxifloxacin and gatifloxacin showed intermediate activities. In assays of drug-mediated DNA cleavage by gyrase and topoisomerase IV, the same order of potency was seen: gemifloxacin > moxifloxacin > gatifloxacin > levofloxacin ≈ ciprofloxacin. For gemifloxacin, the drug concentrations that caused 25% linearization of the input DNA by gyrase and topoisomerase IV were 2.5 and 0.1 to 0.3 μM, respectively; these values were 4-fold and 8- to 25-fold lower than those for moxifloxacin, respectively. Each drug induced DNA cleavage by gyrase at the same spectrum of sites but with different patterns of intensity. Finally, for enzymes reconstituted with quinolone-resistant GyrA S81F or ParC S79F subunits, although cleavable-complex formation was reduced by at least 8- to 16-fold for all the quinolones tested, gemifloxacin was the most effective; e.g., it was 4- to 16-fold more active than the other drugs against toposiomerase IV with the ParC S79F mutation. It appears that the greater potency of gemifloxacin against both wild-type and quinolone-resistant
S. pneumoniae
strains arises from enhanced stabilization of gyrase and topoisomerase IV complexes on DNA.
Comparison of In Vitro Activities of ABT-773 and Telithromycin against Macrolide-Susceptible and -Resistant Streptococci and Staphylococci
Authors: Shortridge Virginia D. , Zhong Ping , Cao Zhensheng , Beyer Jill M. , Almer Laurel S. , Ramer Nancy C. , Doktor Stella Z. , Flamm Robert K. 
Published: July 2002

ABSTRACT

The activity of a new ketolide, ABT-773, was compared to the activity of the ketolide telithromycin (HMR-3647) against over 600 gram-positive clinical isolates, including 356
Streptococcus pneumoniae
, 167
Staphylococcus aureus
, and 136
Streptococcus pyogenes
isolates. Macrolide-susceptible isolates as well as macrolide-resistant isolates with ribosomal methylase (Erm), macrolide efflux (Mef), and ribosomal mutations were tested using the NCCLS reference broth microdilution method. Both compounds were extremely active against macrolide-susceptible isolates, with the minimum inhibitory concentrations at which 90% of the isolates tested were inhibited (MIC
90
s) for susceptible streptococci and staphylococci ranging from 0.002 to 0.03 μg/ml for ABT-773 and 0.008 to 0.06 μg/ml for telithromycin. ABT-773 had increased activities against macrolide-resistant
S. pneumoniae
(Erm MIC
90
, 0.015 μg/ml; Mef MIC
90
, 0.12 μg/ml) compared to those of telithromycin (Erm MIC
90
, 0.12 μg/ml; Mef MIC
90
, 1 μg/ml). Both compounds were active against strains with rRNA or ribosomal protein mutations (MIC
90
, 0.12 μg/ml). ABT-773 was also more active against macrolide-resistant
S. pyogenes
(ABT-773 Erm MIC
90
, 0.5 μg/ml; ABT-773 Mef MIC
90
, 0.12 μg/ml; telithromycin Erm MIC
90
, >8 μg/ml; telithromycin Mef MIC
90
, 1.0 μg/ml). Both compounds lacked activity against constitutive macrolide-resistant
Staphylococcus aureus
but had good activities against inducibly resistant
Staphylococcus aureus
(ABT-773 MIC
90
, 0.06 μg/ml; telithromycin MIC
90
, 0.5 μg/ml). ABT-773 has superior activity against macrolide-resistant streptococci compared to that of telithromycin.
Risk Factors for Piperacillin-Tazobactam-Resistant
Pseudomonas aeruginosa
among Hospitalized Patients
Authors: Harris Anthony D. , Perencevich Eli , Roghmann Mary-Claire , Morris Glenn , Kaye Keith S. , Johnson Judith A. 
Published: July 2002

ABSTRACT

Antimicrobial resistance is an emerging problem with
Pseudomonas aeruginosa
. This study determined risk factors for the recovery of piperacillin-tazobactam-resistant
P. aeruginosa
from clinical cultures from hospitalized patients. A case-control study design was used to compare two groups of case patients with control patients. The first group of case patients was defined by nosocomial isolation of piperacillin-tazobactam-resistant
P. aeruginosa
, and the second group of cases yielded piperacillin-tazobactam-susceptible
P. aeruginosa
. Controls were selected in a 6:1 ratio from the same medical or surgical services among which piperacillin-tazobactam-resistant
P. aeruginosa
arose in patients. Risk factors analyzed included antimicrobial drug exposure, comorbid conditions, and demographics. Bivariate and multivariable analyses were performed. Piperacillin-tazobactam-resistant
P. aeruginosa
was isolated from 179 patients, and piperacillin-tazobactam-susceptible
P. aeruginosa
was isolated from 624 patients over a 2.5-year period. Piperacillin-tazobactam (odds ratio [OR] = 6.82; 95% confidence interval [CI], 4.56 to 10.21), imipenem (OR = 2.42; 95% CI, 1.19 to 4.94), aminoglycosides (OR = 2.18; 95% CI, 1.44 to 3.28), vancomycin (OR = 1.87; 95% CI, 1.21 to 2.89), and broad-spectrum cephalosporins (OR = 2.38; 95% CI, 1.45 to 3.88) were the antibiotics associated with the isolation of piperacillin-tazobactam-resistant
P. aeruginosa
. Exposure to vancomycin (OR = 1.53; 95% CI, 1.13 to 2.06) or ampicillin-sulbactam (OR = 2.28; 95% CI, 1.62 to 3.21) was associated with recovery of piperacillin-tazobactam-susceptible
P. aeruginosa
. In this study, antibiotics associated with piperacillin-tazobactam-susceptible
P. aeruginosa
were different from antibiotics associated with piperacillin-tazobactam-resistant
P. aeruginosa
. Piperacillin-tazobactam was a strong risk factor for piperacillin-tazobactam-resistant
P. aeruginosa
. Our results suggest that the nosocomial isolation of piperacillin-tazobactam-resistant
P. aeruginosa
may be affected by multiple antibiotics.
Novel Use of a Guanosine Prodrug Approach To Convert 2',3'-Didehydro-2',3'-Dideoxyguanosine into a Viable Antiviral Agent
Authors: Ray Adrian S. , Yang Zhenjun , Chu Chung K. , Anderson Karen S. 
Published: July 2002

ABSTRACT
Transient kinetic studies with human immunodeficiency virus (HIV) type 1 reverse transcriptase suggest that nucleotide analogs containing the 2',3'-didehydro-2',3'-dideoxy ribose ring structure present in D4T (stavudine) triphosphate are among the most effective alternative substrates. For unclear reasons, however, the corresponding purine nucleoside, 2',3'-didehydro-2',3'-dideoxyguanosine (D4G), was found to be inactive in cell culture. We have found that the previously reported lack of activity of D4G is primarily due to solution instability, and in this report we describe a novel use of a guanosine prodrug approach to stabilize the nucleoside. D4G was modified at the 6 position of the purine ring to contain a cyclopropylamino group yielding the prodrug, cyclo-D4G. An evaluation of cyclo-D4G revealed that the prodrug possessed anti-HIV activity. In addition, cyclo-D4G had increased stability, lipophilicity, and solubility, as well as decreased toxicity relative to D4G, suggesting that further study is warranted.
In Vitro and In Vivo Activities of a Novel Cephalosporin, BMS-247243, against Organisms other than Staphylococci
Authors: Clark Junius , Fung-Tomc Joan C. , Minassian Beatrice , Tsai Yuan-Hwang , Yang Hyekyung , Huczko Elizabeth , Kolek Benjamin , Chaniewski Susan , Ferraro Cheryl , Drain Rebecca , Gradelski Elizabeth , Bonner Daniel P. 
Published: July 2002

ABSTRACT

BMS-247243, a novel cephalosporin inhibitory for methicillin-resistant staphylococci, primarily has activity against gram-positive bacteria. The activities of BMS-247243, cefotaxime, and ceftriaxone against streptococci and
Streptococcus pneumoniae
were similar. BMS-247243 inhibits
Enterococcus faecalis
but not
Enterococcus faecium
. BMS-247243 also inhibits many inherently vancomycin-resistant species (
Leuconstoc
,
Lactobacillus
,
Pediococcus
) and anaerobic gram-positive bacteria.
In Vitro Activities of a New Des-Fluoroquinolone, BMS 284756, and Seven Other Antimicrobial Agents against 151 Isolates of
Eikenella corrodens
Authors: Goldstein Ellie J. C. , Citron Diane M. , Merriam C. Vreni , Warren Yumi A. , Tyrrell Kerin L. , Fernandez Helen 
Published: July 2002

ABSTRACT

The des-fluoroquinolone BMS 284756 was active in vitro against all 151 clinical strains of
Eikenella corrodens
at a MIC of ≤0.25 μg/ml and was comparable in activity to moxifloxacin and levofloxacin. The MIC at which 90% of the isolates were inhibited by penicillin G was 2 μg/ml; MICs for 8.6% of the strains (13 of 151) were ≥4 μg/ml, including for two beta-lactamase-producing isolates. Amoxicillin-clavulanate and ampicillin-sulbactam inhibited all strains at a MIC of ≤1 μg/ml.
Candida albicans
Sterol C-14 Reductase, Encoded by the
ERG24
Gene, as a Potential Antifungal Target Site
Authors: Jia N. , Arthington-Skaggs B. , Lee W. , Pierson C. A. , Lees N. D. , Eckstein J. , Barbuch R. , Bard M. 
Published: July 2002

ABSTRACT

The incidence of fungal infections has increased dramatically, which has necessitated additional and prolonged use of the available antifungal agents. Increased resistance to the commonly used antifungal agents, primarily the azoles, has been reported, thus necessitating the discovery and development of compounds that would be effective against the major human fungal pathogens. The sterol biosynthetic pathway has proved to be a fertile area for antifungal development, and steps which might provide good targets for novel antifungal development remain. The sterol C-14 reductase, encoded by the
ERG24
gene, could be an effective target for drug development since the morpholine antifungals, inhibitors of Erg24p, have been successful in agricultural applications. The
ERG24
gene of
Candida albicans
has been isolated by complementation of a
Saccharomyces cerevisiae erg24
mutant. Both copies of the
C. albicans ERG24
gene have been disrupted by using short homologous regions of the
ERG24
gene flanking a selectable marker. Unlike
S. cerevisiae
, the
C. albicans ERG24
gene was not required for growth, but
erg24
mutants showed several altered phenotypes. They were demonstrated to be slowly growing, with doubling times at least twice that of the wild type. They were also shown to be significantly more sensitive to an allylamine antifungal and to selected cellular inhibitors including cycloheximide, cerulenin, fluphenazine, and brefeldin A. The
erg24
mutants were also slightly resistant to the azoles. Most importantly,
erg24
mutants were shown to be significantly less pathogenic in a mouse model system and failed to produce germ tubes upon incubation in human serum. On the basis of these characteristics, inhibitors of Erg24p would be effective against
C. albicans
.
Pharmacokinetics of Amino Acid Phosphoramidate Monoesters of Zidovudine in Rats
Authors: Song Heng , Griesgraber George W. , Wagner Carston R. , Zimmerman Cheryl L. 
Published: July 2002

ABSTRACT

In vitro studies have demonstrated that water-soluble, nontoxic phosphoramidates of azidothymidine (zidovudine [AZT]) have significant and specific anti-human immunodeficiency virus and anticancer activity. Although polar, these compounds are internalized and processed to the corresponding nucleoside monophosphates. Eight methyl amide and methyl ester phosphoramidate monoesters composed of
d
- or
l
-phenylalanine or tryptophan and AZT were synthesized. The plasma stability and protein binding studies were carried out in vitro. Then in vivo pharmacokinetic evaluations of six of the compounds were conducted. Sprague-Dawley rats received each compound by intravenous bolus dose, and serial blood and urine samples were collected. AZT and phosphoramidate concentrations in plasma and urine were quantitated by high-performance liquid chromatography with UV or fluorescence detection. Pharmacokinetic parameters were calculated by standard noncompartmental means. The plasma half-lives of the phosphoramidates were 10- to 20-fold longer than the half-life of AZT. Although the renal clearances of the phosphoramidates were similar to AZT, their total body clearances were significantly greater than that of AZT. The 3- to 15-fold-larger volume of distribution (
V
ss
) for the phosphoramidates relative to AZT appeared to be dependent on the stereochemistry of the amino acid, with the largest values being associated with the
l
-amino acids. The increased
V
ss
indicates a much greater tissue distribution of the phosphoramidate prodrugs than of AZT. Amino acid phosphoramidate monoesters of AZT have improved pharmacokinetic properties over AZT and significant potential as in vivo pronucleotides.
Comparative Pharmacodynamics of Three Newer Fluoroquinolones versus Six Strains of Staphylococci in an In Vitro Model under Aerobic and Anaerobic Conditions
Authors: Wright David H. , Gunderson Brent W. , Hovde Laurie B. , Ross Gigi H. , Ibrahim Khalid H. , Rotschafer John C. 
Published: July 2002

ABSTRACT

Six strains of staphylococci were exposed to levofloxacin, moxifloxacin, or trovafloxacin in an in vitro pharmacodynamic model under both aerobic and anaerobic conditions. Each agent demonstrated a rapid 3-log
10
kill versus susceptible isolates regardless of condition. Against clinical isolates with reduced susceptibility, regrowth occurred by 24 h and was frequently associated with further increases in MICs.