bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ribonucleoside Analogue That Blocks Replication of Bovine Viral Diarrhea and Hepatitis C Viruses in Culture
Authors: Stuyver Lieven J. , Whitaker Tony , McBrayer Tamara R. , Hernandez-Santiago Brenda I. , Lostia Stefania , Tharnish Phillip M. , Ramesh Mangala , Chu Chung K. , Jordan Robert , Shi Junxing , Rachakonda Suguna , Watanabe Kyoichi A. , Otto Michael J. , Schinazi Raymond F. 
Published: December 2002

ABSTRACT

A base-modified nucleoside analogue, β-
d
-N
4
-hydroxycytidine (NHC), was found to have antipestivirus and antihepacivirus activities. This compound inhibited the production of cytopathic bovine viral diarrhea virus (BVDV) RNA in a dose-dependant manner with a 90% effective concentration (EC
90
) of 5.4 μM, an observation that was confirmed by virus yield assays (EC
90
= 2 μM). When tested for hepatitis C virus (HCV) replicon RNA reduction in Huh7 cells, NHC had an EC
90
of 5 μM on day 4. The HCV RNA reduction was incubation time and nucleoside concentration dependent. The in vitro antiviral effect of NHC was additive with recombinant alpha interferon-2a and could be prevented by the addition of exogenous cytidine and uridine but not of other natural ribo- or 2′-deoxynucleosides. When HCV RNA replicon cells were cultured in the presence of increasing concentrations of NHC (up to 40 μM) for up to 45 cell passages, no resistant replicon was selected. Similarly, resistant BVDV could not be selected after 20 passages. NHC was phosphorylated to the triphosphate form in Huh7 cells, but in cell-free HCV NS5B assays, synthetic NHC-triphosphate (NHC-TP) did not inhibit the polymerization reaction. Instead, NHC-TP appeared to serve as a weak alternative substrate for the viral polymerase, thereby changing the mobility of the product in polyacrylamide electrophoresis gels. We speculate that incorporated nucleoside analogues with the capacity of changing the thermodynamics of regulatory secondary structures (with or without introducing mutations) may represent an important class of new antiviral agents for the treatment of RNA virus infections, especially HCV.
Roles of
Mycobacterium smegmatis
d
-Alanine:
d
-Alanine Ligase and
d
-Alanine Racemase in the Mechanisms of Action of and Resistance to the Peptidoglycan Inhibitor
d
-Cycloserine
Authors: Feng Zhengyu , Barletta Raúl G. 
Published: December 2002

ABSTRACT

d-
Cycloserine (DCS) targets the peptidoglycan biosynthetic enzymes
d-
alanine racemase (Alr) and
d-
alanine:
d-
alanine ligase (Ddl). Previously, we demonstrated that the overproduction of Alr in
Mycobacterium smegmatis
determines a DCS resistance phenotype. In this study, we investigated the roles of both Alr and Ddl in the mechanisms of action of and resistance to DCS in
M. smegmatis
. We found that the overexpression of either the
M. smegmatis
or the
Mycobacterium tuberculosis ddl
gene in
M. smegmatis
confers resistance to DCS, but at lower levels than the overexpression of the
alr
gene. Furthermore, a strain overexpressing both the
alr
and
ddl
genes displayed an eightfold-higher level of resistance. To test the hypothesis that inhibition of Alr by DCS decreases the intracellular pool of
d-
alanine, we determined the alanine pools in
M. smegmatis
wild-type and recombinant strains with or without DCS treatment. Alr-overproducing strain GPM14 cells not exposed to DCS displayed almost equimolar amounts of
l-
and
d-
alanine in the steady state. The wild-type strain and Ddl-overproducing strains contained a twofold excess of
l-
over
d-
alanine. In all strains, DCS treatment led to a significant accumulation of
l-
alanine and a concomitant decease of
d-
alanine, with approximately a 20-fold excess of
l-
alanine in the Ddl-overproducing strains. These data suggest that Ddl is not significantly inhibited by DCS at concentrations that inhibit Alr. This study is of significance for the identification of the lethal target(s) of DCS and the development of novel drugs targeting the
d-
alanine branch of mycobacterial peptidoglycan biosynthesis.
High-Throughput Growth Assay forToxoplasma gondiiUsing Yellow Fluorescent Protein
Authors: Gubbels Marc-Jan , Li Catherine , Striepen Boris 
Published: December 2002

ABSTRACTA high-throughput growth assay for the protozoan parasiteToxoplasma gondiiwas developed based on a highly fluorescent transgenic parasite line. These parasites are stably transfected with a tandem yellow fluorescent protein (YFP) and are 1,000 times more fluorescent than the wild type. Parasites were inoculated in optical-bottom 384-well culture plates containing a confluent monolayer of host cells, and growth was monitored by using a fluorescence plate reader. The signal was linearly correlated with parasite numbers over a wide array. Direct comparison of the YFP growth assay with the β-galactosidase growth assay by using parasites expressing both reporters demonstrated that the assays' sensitivities were comparable but that the accuracy of the YFP assay was higher, especially at higher numbers of parasites per well. Determination of the 50%-inhibitory concentrations of three known growth-inhibiting drugs (cytochalasin D, pyrimethamine, and clindamycin) resulted in values comparable to published data. The delayed parasite death kinetics of clindamycin could be measured without modification of the assay, making this assay very versatile. Additionally, the temperature-dependent effect of pyrimethamine was assayed in both wild-type and engineered drug-resistant parasites. Lastly, the development of mycophenolic acid resistance after transfection of a resistance gene inT. gondiiwas followed. In conclusion, the YFP growth assay limits pipetting steps to a minimum, is highly versatile and amendable to automation, and should enable rapid screening of compounds to fulfill the need for more efficient and less toxic antiparasitic drugs.
Contributions of Antibiotic Penetration, Oxygen Limitation, and Low Metabolic Activity to Tolerance of
Pseudomonas aeruginosa
Biofilms to Ciprofloxacin and Tobramycin
Authors: Walters Marshall C. , Roe Frank , Bugnicourt Amandine , Franklin Michael J. , Stewart Philip S. 
Published: December 2002

ABSTRACT

The roles of slow antibiotic penetration, oxygen limitation, and low metabolic activity in the tolerance of
Pseudomonas aeruginosa
in biofilms to killing by antibiotics were investigated in vitro. Tobramycin and ciprofloxacin penetrated biofilms but failed to effectively kill the bacteria. Bacteria in colony biofilms survived prolonged exposure to either 10 μg of tobramycin ml
−1
or 1.0 μg of ciprofloxacin ml
−1
. After 100 h of antibiotic treatment, during which the colony biofilms were transferred to fresh antibiotic-containing plates every 24 h, the log reduction in viable cell numbers was only 0.49 ± 0.18 for tobramycin and 1.42 ± 0.03 for ciprofloxacin. Antibiotic permeation through colony biofilms, indicated by a diffusion cell bioassay, demonstrated that there was no acceleration in bacterial killing once the antibiotics penetrated the biofilms. These results suggested that limited antibiotic diffusion is not the primary protective mechanism for these biofilms. Transmission electron microscopic observations of antibiotic-affected cells showed lysed, vacuolated, and elongated cells exclusively near the air interface in antibiotic-treated biofilms, suggesting a role for oxygen limitation in protecting biofilm bacteria from antibiotics. To test this hypothesis, a microelectrode analysis was performed. The results demonstrated that oxygen penetrated 50 to 90 μm into the biofilm from the air interface. This oxic zone correlated to the region of the biofilm where an inducible green fluorescent protein was expressed, indicating that this was the active zone of bacterial metabolic activity. These results show that oxygen limitation and low metabolic activity in the interior of the biofilm, not poor antibiotic penetration, are correlated with antibiotic tolerance of this
P. aeruginosa
biofilm system.
Comparison of Anti-Hepatitis B Virus Activities of Lamivudine and Clevudine by a Quantitative Assay
Authors: Abdelhamed Ayman M. , Kelley Colleen M. , Miller Thomas G. , Furman Phillip A. , Cable Edward E. , Isom Harriet C. 
Published: December 2002

ABSTRACTIn this study, we used a quantitative assay to measure the concentration-dependent effects of antivirals on extracellular hepatitis B virus (HBV) DNA as well as on different cytoplasmic and nuclear forms of HBV DNA that participate in HBV replication. HBV recombinant baculovirus, which efficiently delivers the HBV genome to HepG2 cells, was used for this study because (i) antivirals can be administered prior to initiation of HBV infection or after HBV infection and (ii) sufficiently high HBV replication levels are achieved that HBV covalently closed circular (CCC) DNA can be easily detected and individual HBV DNA species can be quantitatively analyzed separately from total HBV DNA. The results showed that the levels of HBV replicative intermediate and extracellular DNA decreased in a concentration-dependent fashion following antiviral treatment. The 50% effective concentration (EC50) and EC90values and the Hill slopes differed for the different HBV DNA species analyzed. The data clearly indicated that (i) nuclear HBV DNAs are more resistant to antiviral therapy than cytoplasmic or extracellular HBV DNAs and (ii) nuclear HBV CCC DNA is more resistant than the nuclear relaxed circular form. This report presents the first in vitro comparison of the effects of two antivirals administered prior to initiation of HBV infection and the first thorough in vitro quantitative study of concentration-dependent antiviral effects on HBV CCC DNA.
In34, a Complex In5 Family Class 1 Integron Containing orf513 and
dfrA10
Authors: Partridge Sally R. , Hall Ruth M. 
Published: December 2002

ABSTRACT

A complex class 1 integron, In34, found in a conjugative plasmid from a multidrug-resistant
Klebsiella pneumoniae
strain isolated in 1997 at a hospital in Sydney, Australia, was shown to have a backbone related to that of In2, which belongs to the In5 family. In In34, the
aadB
gene cassette replaces the
aadA1a
cassette in In2, and two additional resistance genes,
dfrA10
and
aphA1
, that are not part of a gene cassette are present. The
aphA1
gene is in a Tn
4352
-like transposon that is located in the
tniA
gene. The
dfrA10
gene lies adjacent to a 2,154-bp DNA segment, known as the common region, that contains an open reading frame predicting a product of 513 amino acids (Orf513). Orf513 is 66 and 55% identical to the products of two further open reading frames that, like the common region, are found adjacent to antibiotic resistance genes. A 27-bp conserved sequence was found at one end of each type of common region. The loss of
dfrA10
due to homologous recombination between flanking direct repeats and incorporation of the excised circle by homologous recombination were demonstrated. Part of In34 is identical to the sequenced portion of In7, which is from a multidrug-resistant
Escherichia coli
strain that had been isolated 19 years earlier in the same hospital. In34 and In7 are in plasmids that contain the same six resistance genes conferring resistance to ampicillin, chloramphenicol, gentamicin, kanamycin, neomycin, tobramycin, trimethoprim, and sulfonamides, but the plasmid backbones appear to be unrelated, suggesting that translocation of a multiple-drug-resistance-determining region as well as horizontal transfer may have occurred.
Activities of Moxifloxacin Alone and in Combination with Other Antimicrobial Agents against Multidrug-Resistant
Mycobacterium tuberculosis
Infection in BALB/c Mice
Authors: Fattorini Lanfranco , Tan Dejiang , Iona Elisabetta , Mattei Maurizio , Giannoni Federico , Brunori Lara , Recchia Simona , Orefici Graziella 
Published: December 2002

ABSTRACT

The activity of moxifloxacin was enhanced by the addition of ethionamide but not by that of cycloserine, thiacetazone, capreomycin,
para
-aminosalicylic acid, or linezolid in BALB/c mice infected with a strain of
Mycobacterium tuberculosis
resistant to isoniazid, rifampin, and six other drugs. These observations are important for the therapy of multidrug-resistant tuberculosis.
Clindamycin Modulates Inflammatory-Cytokine Induction in Lipopolysaccharide-Stimulated Mouse Peritoneal Macrophages
Authors: Nakano Tetsuji , Hiramatsu Kazufumi , Kishi Kenji , Hirata Norio , Kadota Jun-ichi , Nasu Masaru 
Published: December 2002

ABSTRACTWe investigated the mechanism by which clindamycin (CLI) modulates cytokine induction after lipopolysaccharide (LPS) stimulation. Although CLI decreased the intracellular expression levels of tumor necrosis factor alpha and interleukin 1β (IL-1β) and increased IL-6 expression in macrophages, cytokine mRNA expression levels were similar in CLI-treated and untreated groups. Our findings suggest that CLI modulates cytokine production in LPS-stimulated macrophages.
Penetration of Fosfomycin into Inflammatory Lesions in Patients with Cellulitis or Diabetic Foot Syndrome
Authors: Legat F. J. , Maier A. , Dittrich P. , Zenahlik P. , Kern T. , Nuhsbaumer S. , Frossard M. , Salmhofer W. , Kerl H. , Müller M. 
Published: December 2002

ABSTRACTWe investigated the distribution of the broad-spectrum antibiotic fosfomycin in infected soft tissue of patients with uncomplicated cellulitis of the lower extremities or diabetic foot infection using in vivo microdialysis. Our findings suggest that fosfomycin exhibits good and similar penetration into the fluid in the interstitial space in inflamed and noninflamed soft tissue in patients.
Synergistic Lethal Effect of a Combination of Phage Lytic Enzymes with Different Activities on Penicillin-Sensitive and -Resistant
Streptococcus pneumoniae
Strains
Authors: Loeffler J. M. , Fischetti V. A. 
Published: December 2002

ABSTRACT

Pal and Cpl-1, two purified bacteriophage lytic enzymes, were tested for their in vitro activity, alone and in combination, against several serotypes of
Streptococcus pneumoniae
, including penicillin-resistant strains. The enzymes demonstrated synergism in their ability to cleave the bacterial peptidoglycan and thus may be more efficient for the prevention and elimination of pneumococcal colonization.
In Vivo Selection of
Campylobacter
Isolates with High Levels of Fluoroquinolone Resistance Associated with
gyrA
Mutations and the Function of the CmeABC Efflux Pump
Authors: Luo Naidan , Sahin Orhan , Lin Jun , Michel Linda O. , Zhang Qijing 
Published: December 2002

ABSTRACT

Enrofloxacin treatment of chickens infected with fluoroquinolone(FQ)-sensitive
Campylobacter
promoted the emergence of FQ-resistant
Campylobacter
mutants which propagated in the intestinal tract and recolonized the chickens. The recovered isolates were highly resistant to quinolone antibiotics but remained susceptible to non-FQ antimicrobial agents. Specific single-point mutations in the
gyrA
gene and the function of the CmeABC efflux pump were linked to the acquired FQ resistance. These results reveal that
Campylobacter
is hypermutable in vivo under the selection pressure of FQ and highlight the need for the prudent use of FQ antibiotics.
Comparison of Linezolid Activities under Aerobic and Anaerobic Conditions against Methicillin-Resistant
Staphylococcus aureus
and Vancomycin-Resistant
Enterococcus faecium
Authors: Gunderson Brent W. , Ibrahim Khalid H. , Peloquin Charles A. , Hovde Laurie B. , Rotschafer John C. 
Published: December 2002

ABSTRACT

Methicillin-resistant
Staphylococcus aureus
and vancomycin-resistant
Enterococcus faecium
were exposed to linezolid (MIC of 2 mg/liter) under aerobic or anaerobic conditions in an in vitro pharmacodynamic model. Drug concentration and half-life were adjusted to simulate clinical dosing (600 mg twice daily) of linezolid. Linezolid produced a 2-log
10
killing at 24 h, and rates of killing against each of these facultative organisms as measured by mean survival time appeared similar under aerobic and anaerobic conditions.
Activities of the Glycylcycline Tigecycline (GAR-936) against 1,924 Recent European Clinical Bacterial Isolates
Authors: Milatovic D. , Schmitz F.-J. , Verhoef J. , Fluit A. C. 
Published: December 2002

ABSTRACT

The in vitro activities of tigecycline against 1,924 clinical isolates were examined. The new glycylcycline exhibited excellent activity against all gram-positive cocci (MICs at which 90% of the isolates tested were inhibited [MIC
90
s], ≤1 μg/ml). In addition, it was also very potent against most members of the
Enterobacteriaceae
, with most MIC
90
s being ≤2 μg/ml. Among the nonfermenters,
Acinetobacter
spp. and
Stenotrophomonas maltophilia
are included in the in vitro spectrum of tigecycline activity.
Activities of HMR 3787 and RU 64399 Compared with Those of Four Other Agents against
Haemophilus influenzae
and
Haemophilus parainfluenzae
Authors: Bozdogan Bülent , Clark Catherine , Bryskier Andre , Jacobs Michael R. , Appelbaum Peter C. 
Published: December 2002

ABSTRACT

Activities of HMR 3787, a new 2-fluoroketolide, and its (des)-fluor derivative, RU 64399, were tested against 111
Haemophilus influenzae
and 26
H. parainfluenzae
strains and compared with those of telithromycin, erythromycin, azithromycin, and clarithromycin. HMR 3787 and RU 64399 MICs were comparable with those of azithromycin but were less affected by incubation in CO
2
. Time-kill studies of 12 strains showed that HMR 3787, RU 64399, and telithromycin were bactericidal against all strains after 24 h at two times the MIC.
Correlation of Phenotypic Zidovudine Resistance with Mutational Patterns in the Reverse Transcriptase of Human Immunodeficiency Virus Type 1: Interpretation of Established Mutations and Characterization of New Polymorphisms at Codons 208, 211, and 214
Authors: Stürmer Martin , Staszewski Schlomo , Doerr Hans-Wilhelm , Larder Brendan , Bloor Stuart , Hertogs Kurt 
Published: December 2002

ABSTRACT
Zidovudine resistance (ZDV-R) is associated with classic genotypic changes at codons 41, 67, 70, 210, 215, and 219 of the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) gene as well as with the multinucleoside resistance (MNR) complexes (Q151M MNR complex; 6-bp insertion/A62V complex). In addition, enhanced resistance to ZDV in the context of the classic ZDV mutations plus the M184V mutation has been associated with additional mutations at positions 208, 211, 214, and 333. In this study we investigated phenotypic ZDV-R determined by a recombinant virus assay (Antivirogram; Virco) in 223 clinical samples in relation to the above genotypic changes. 150 out of 223 clinical samples had the M184V mutation. Phenotypic ZDV-R ranged from 0.3- to 5,338-fold. Sixteen samples (15 with high ZDV-R ranging from 90- to 3,571-fold) contained MNR-associated patterns. Analysis of classic mutational patterns broadly demonstrated increasing ZDV-R with increasing number of ZDV mutations. A comparable correlation was obtained when ZDV-R was analyzed only relative to the T215Y/F mutation. Site-directed mutagenesis experiments investigating the influence of the additional mutations H208Y, R211K, and L214F on ZDV-R resulted in a 7.4- or 21-fold increase in ZDV-R when the R211K/L214F or H208Y/R211K/L214F mutations, respectively, were added to a highly ZDV-R virus. In the clinical sample data set we analyzed, the combination of R211K/L214F appeared most frequently. The H208Y change was detected only in highly ZDV-R viruses, whereas the G333E/D change was distributed equally. All changes were independent of the M184V mutation. A 2.4- or 8-fold increase in ZDV-R was observed in the clinical samples with high ZDV-R containing the R211K/L214F or H208Y/R211K/L214F mutations, respectively. We have shown that the combination of the additional mutations H208Y, R211K, and L214F in HIV-1 RT may influence ZDV-R and should be considered when assessing ZDV-R.
Susceptibility ofCandida dubliniensisto Salivary Histatin 3
Authors: Fitzgerald Deirdre H. , Coleman David C. , O'Connell Brian C. 
Published: December 2002

ABSTRACTCandida dubliniensisis a recently describedCandidaspecies associated with oral candidiasis in human immunodeficiency virus (HIV)-infected patients and patients with AIDS. The majority ofC. dubliniensisclinical isolates tested to date are susceptible to the commonly used antifungal drugs, including fluconazole, ketoconazole, itraconazole, and amphotericin B. However, the appearance of fluconazole-resistantC. dubliniensisstrains in this patient group is increasing. Histatins are a family of basic histidine-rich proteins present in human saliva which have therapeutic potential in the treatment of oral candidiasis. The mechanism of action of histatin is distinct from that of commonly used azole and polyene drugs. Characterization of the antifungal activity of histatin has mainly been carried out usingC. albicansbut it is also effective in killingC. glabrataandC. krusei. Here we report thatC. dubliniensisis also susceptible to killing by histatin 3. The concentration of histatin 3 giving 50% killing (the IC50value) ranged from 0.043 to 0.196 mg/ml among different strains ofC. dubliniensis. The least-susceptibleC. dubliniensisstrain, P9224, was found to internalize histatin at a lower rate than theC. albicansreference strain CA132A. The dissociation constant (Kd) for the least-susceptible strain (C. dubliniensis9224) was ninefold higher than that for theC. albicansreference strain. These results suggest that histatin 3 may have potential as an effective antifungal agent, particularly in the treatment of oral candidiasis in HIV-infected patients and patients with AIDS in which resistance to the commonly used antifungal drug fluconazole has emerged.
D2 dopamine receptor gene in psychiatric and neurologic disorders and its phenotypes
Authors: Noble Ernest P. 
Published: December 2002

AbstractThe D2 dopamine receptor (DRD2) has been one of the most extensively investigated gene in neuropsychiatric disorders. After the first association of the TaqI A DRD2 minor (A1) allele with severe alcoholism in 1990, a large number of international studies have followed. A meta‐analysis of these studies of Caucasians showed a significantly higher DRD2 A1 allelic frequency and prevalence in alcoholics when compared to controls. Variants of the DRD2 gene have also been associated with other addictive disorders including cocaine, nicotine and opioid dependence and obesity. It is hypothesized that the DRD2 is a reinforcement or reward gene. The DRD2 gene has also been implicated in schizophrenia, posttraumatic stress disorder, movement disorders and migraine. Phenotypic differences have been associated with DRD2 variants. These include reduced D2 dopamine receptor numbers and diminished glucose metabolism in brains of subjects who carry the DRD2 A1 allele. In addition, pleiotropic effects of DRD2 variants have been observed in neurophysiologic, neuropsychologic, stress response, personality and treatment outcome characteristics. The involvement of the DRD2 gene in certain neuropsychiatric disorders opens up the potential of a targeted pharmacogenomic approach to the treatment of these disorders. © 2003 Wiley‐Liss, Inc.