bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitochondrial Ribosome as the Target for the Macrolide Antibiotic Clarithromycin in the Helminth
Echinococcus multilocularis
Authors: Mathis Alexander , Wild Peter , Boettger Erik C. , Kapel Christian M. O. , Deplazes Peter 
Published: July 2005

ABSTRACT

The mitochondrial rRNA of the tapeworm species
Echinococcus multilocularis
carries an adenine at sequence position 2058 (numbering according to that for
Escherichia coli
) of the large-subunit rRNA (lsrRNA), while the nucleus-encoded rRNA, as determined in this study, is characterized by 2058G. This indicates a dichotomy in the drug susceptibilities of ribosomes: cytoplasmic ribosomes are predicted to be resistant to macrolide antibiotics, while mitochondrial ribosomes lack the most common chromosomal resistance determinant, lsrRNA 2058G. Upon incubation with the macrolide clarithromycin, the formation of vesicles from metacestode tissue was reduced in a dose-dependent manner. Electron microscopy revealed distinct morphological alterations both of the mitochondria and of the vesicle wall (e.g., loss of microtriches) in drug-treated vesicles. Adult worms lost their motility and displayed morphological changes (shortening and constriction of proglottids and the presence of vacuoles) upon incubation with clarithromycin. Our findings demonstrate that macrolides have distinct in vitro effects on
E. multilocularis
, endorsing the use of sequence-based in silico approaches for exploitation of available ribosomal drugs as anthelmintic agents.
Specific Substitutions in the Echinocandin Target Fks1p Account for Reduced Susceptibility of Rare Laboratory and Clinical
Candida
sp. Isolates
Authors: Park S. , Kelly R. , Kahn J. Nielsen , Robles J. , Hsu M.-J. , Register E. , Li W. , Vyas V. , Fan H. , Abruzzo G. , Flattery A. , Gill C. , Chrebet G. , Parent S. A. , Kurtz M. , Teppler H. , Douglas C. M. , Perlin D. S. 
Published: July 2005

ABSTRACT

An association between reduced susceptibility to echinocandins and changes in the 1,3-β-
d
-glucan synthase (GS) subunit Fks1p was investigated. Specific mutations in
fks1
genes from
Saccharomyces cerevisiae
and
Candida albicans
mutants are described that are necessary and sufficient for reduced susceptibility to the echinocandin drug caspofungin. One group of amino acid changes in ScFks1p, ScFks2p, and CaFks1p defines a conserved region (Phe 641 to Asp 648 of CaFks1p) in the Fks1 family of proteins. The relationship between several of these
fks1
mutations and the phenotype of reduced caspofungin susceptibility was confirmed using site-directed mutagenesis or integrative transformation. Glucan synthase activity from these mutants was less susceptible to caspofungin inhibition, and heterozygous and homozygous Ca
fks1 C. albicans
mutants could be distinguished based on the shape of inhibition curves. The
C. albicans
mutants were less susceptible to caspofungin than wild-type strains in a murine model of disseminated candidiasis. Five
Candida
isolates with reduced susceptibility to caspofungin were recovered from three patients enrolled in a clinical trial. Four
C. albicans
strains showed amino acid changes at Ser 645 of CaFks1p, while a single
Candida krusei
isolate had a deduced R1361G substitution. The clinical
C. albicans
mutants were less susceptible to caspofungin in the disseminated candidiasis model, and GS inhibition profiles and DNA sequence analyses were consistent with a homozygous
fks1
mutation. Our results indicate that substitutions in the Fks1p subunit of GS are sufficient to confer reduced susceptibility to echinocandins in
S. cerevisiae
and the pathogens
C. albicans
and
C. krusei
.
Production and Characterization of Stable Amphotericin-Resistant Amastigotes and Promastigotes of
Leishmania mexicana
Authors: Al-Mohammed Hamdan I. , Chance Michael L. , Bates Paul A. 
Published: July 2005

ABSTRACT

The sensitivities of
Leishmania mexicana
amastigote and promastigote forms to amphotericin B were investigated in vitro and found to be strongly influenced by the culture media used. When differences in culture media were minimized, there was no significant difference in the 50% inhibitory concentration values between the two life cycle stages. Stable amphotericin B-resistant amastigote and promastigote lines were produced by the application of increasing drug pressure to long-term cultures. Lines capable of growth in concentrations of amphotericin B lethal to normal parasites were produced. Compared to normal parasites, these amphotericin-resistant lines showed marked differences in membrane sterol compositions, with very high levels of 4,14,dimethyl-cholesta-8,24-dienol and other methyl sterols. They also showed a consistent morphological feature, the presence of multilamellar membrane-like material in the flagellar pocket, revealed by transmission electron microscopy. Amphotericin-resistant parasites were capable of infecting BALB/c mice, but the resulting lesion growth was slower than that after infection with normal parasites. However, unlike normal parasites, the amphotericin-resistant parasites were unaffected by experimental chemotherapy with amphotericin B. These results show that amphotericin B resistance could arise as a result of increased clinical use of amphotericin B therapy.
Tn
5393
d, a Complex Tn
5393
Derivative Carrying the PER-1 Extended-Spectrum β-Lactamase Gene and Other Resistance Determinants
Authors: Mantengoli Elisabetta , Rossolini Gian Maria 
Published: July 2005

ABSTRACT

In
Alcaligenes faecalis
FL-424/98, a clinical isolate that produces the PER-1 extended-spectrum β-lactamase, the
bla
PER-1
gene was found to be carried on a 44-kb nonconjugative plasmid, named pFL424, that was transferred to
Escherichia coli
by electroporation. Investigation of the genetic context of the
bla
PER-1
gene in pFL424 by means of a combined cloning and PCR mapping approach revealed that the gene is associated with a transposonlike element of the Tn
3
family. This 14-kb element is a Tn
5393
derivative of original structure, named Tn
5393
d, which contains the transposition module and the
strAB
genes typical of other members of the Tn
5393
lineage plus additional resistance determinants, including the
bla
PER-1
gene and a new allelic variant of the
aphA6
aminoglycoside phosphotransferase gene, named
aphA6b
, whose product is active against kanamycin, streptomycin, and amikacin. Tn
5393
d apparently originated from the consecutive insertion of two composite transposons into a Tn
5393
backbone carrying the
aphA6b
and the
bla
PER-1
genes, respectively. The putative composite transposon carrying
bla
PER-1
, named Tn
4176
, is made of two original and nonidentical insertion sequences of the IS
4
family, named IS
1387
a and IS
1387
b, of which one is interrupted by the insertion of an original insertion sequence of the IS
30
family, named IS
1066
. In pFL424, Tn
5393
d is inserted into a Tn
501
-like mercury resistance transposon. Transposition of Tn
5393
d or modules thereof containing the
bla
PER-1
gene from pFL424 to small multicopy plasmids or to a bacterial artificial chromosome was not detected in an
E. coli
host harboring both replicons.
Efficacy of Cefepime and Imipenem in Experimental Murine Pneumonia Caused by Porin-Deficient
Klebsiella pneumoniae
Producing CMY-2 β-Lactamase
Authors: Pichardo Cristina , Rodríguez-Martínez José Manuel , Pachón-Ibañez María E. , Conejo Carmen , Ibáñez-Martínez José , Martínez-Martínez Luis , Pachón Jerónimo , Pascual Álvaro 
Published: July 2005

ABSTRACT

Previous studies have shown decreased in vitro activity of zwitterionic cephalosporins and carbapenems against porin-deficient
Klebsiella pneumoniae
expressing a plasmid-mediated AmpC-type β-lactamase (PACBL). The in vitro and in vivo activities of cefepime and imipenem were evaluated against the porin-deficient strain
K. pneumoniae
C2 and its CMY-2-producing derivative [
K. pneumoniae
C2(pMG248)]. The MICs (in micrograms/milliliter) of cefepime and imipenem against
K. pneumoniae
C2 were 0.125 and 0.25, respectively, while the corresponding values against
K. pneumoniae
C2(pMG248) were 8 and 16. Cefepime showed a greater inoculum effect than imipenem against both strains. Imipenem showed a significant postantibiotic effect (>2 h) against
K. pneumoniae
C2(pMG248) at 1×, 2×, 4×, 6×, and 8× MIC. The maximum concentrations of drug in serum of cefepime and imipenem in a pneumonia model using mice were 124.1 and 16.9 μg/ml, respectively. ΔT/MIC for
K. pneumoniae
C2 and C2(pMG248) were 1.29 h and 0.34 h for imipenem and 2.96 h and 1.27 h for cefepime. Both imipenem (30 mg/kg of body weight every 3 h) and cefepime (60 mg/kg every 4 h), administered for 72 h, increased the survival rate (86.6% and 100%) compared with untreated control animals (26.6%,
P
< 0.003) infected with
K. pneumoniae
C2. For the CMY-2-producing strain, imipenem, but not cefepime, increased the survival rate compared to the controls (86.6% and 40% versus 40%,
P
< 0.01). Bacterial concentration of the lungs was significantly decreased by both antimicrobials. In conclusion, imipenem was more active in terms of survival than cefepime for the treatment of murine pneumonia caused by a porin-deficient
K. pneumoniae
expressing PACBL CMY-2.
Antistaphylococcal Activity of DX-619, a New Des-F(6)-Quinolone, Compared to Those of Other Agents
Authors: Bogdanovich Tatiana , Esel Duygu , Kelly Linda M. , Bozdogan Bülent , Credito Kim , Lin Gengrong , Smith Kathy , Ednie Lois M. , Hoellman Dianne B. , Appelbaum Peter C. 
Published: July 2005

ABSTRACT

The in vitro activity of DX-619, a new des-F(6)-quinolone, was tested against staphylococci and compared to those of other antimicrobials. DX-619 had the lowest MIC ranges/MIC
50
s/MIC
90
s (μg/ml) against 131
Staphylococcus aureus
strains (≤0.002 to 2.0/0.06/0.5) and 128 coagulase-negative staphylococci (0.004 to 0.25/0.016/0.125). Among strains tested, 76
S. aureus
strains and 51 coagulase-negative staphylococci were resistant to ciprofloxacin. DX-619 had the lowest MIC
50
/MIC
90
values against 127 quinolone-resistant staphylococci (0.125/0.5), followed by sitafloxacin (0.5/4), moxifloxacin (2/8), gatifloxacin (4/16), levofloxacin (16/>32), and ciprofloxacin (>32/>32). Raised quinolone MICs were associated with mutations in GyrA (S84L) and single or double mutations in GrlA (S80F or Y; E84K, G, or V) in all
S. aureus
strains tested. A recent vancomycin-resistant
S.
aureus
(VRSA) strain (Hershey) was resistant to available quinolones and was inhibited by DX-619 at 0.25 μg/ml and
sitafloxacin at 1.0 μg/ml. Vancomycin (except VRSA), linezolid,
ranbezolid, tigecycline, and quinupristin-dalfopristin were active
against all strains, and teicoplanin was active against
S.
aureus
but less active against coagulase-negative staphylococci.
DX-619 produced resistant mutants with MICs of 1 to >32μ
g/ml after <50 days of selection compared to 16 to>
32 μg/ml for ciprofloxacin, sitafloxacin,
moxifloxacin, and gatifloxacin. DX-619 and sitafloxacin were also more
active than other tested drugs against selected mutants and had the
lowest mutation frequencies in single-step resistance selection. DX-619
and sitafloxacin were bactericidal against six quinolone-resistant
(including the VRSA) and seven quinolone-susceptible strains tested,
whereas gatifloxacin, moxifloxacin, levofloxacin, and ciprofloxacin
were bactericidal against 11, 10, 7, and 5 strains at 4× MIC
after 24 h, respectively. DX-619 was also bactericidal
against one other VRSA strain, five vancomycin-intermediate
S.
aureus
strains, and four vancomycin-intermediate
coagulase-negative staphylococci. Linezolid, ranbezolid, and
tigecycline were bacteriostatic and quinupristin-dalfopristin,
teicoplanin, and vancomycin were bactericidal against two, eight, and
nine strains, and daptomycin and oritavancin were rapidly bactericidal
against all strains, including the VRSA. DX-619 has potent in vitro
activity against staphylococci, including methicillin-, ciprofloxacin-,
and vancomycin-resistant
strains.
Quantifying Mixed Populations of Drug-Resistant Human Immunodeficiency Virus Type 1
Authors: Moser Michael J. , Ruckstuhl Meta , Larsen Christine A. , Swearingen Amanda J. , Kozlowski Miroslaw , Bassit Leda , Sharma Prem L. , Schinazi Raymond F. , Prudent James R. 
Published: July 2005

ABSTRACT
In order to survive prolonged treatment with antiretroviral nucleoside analogs, the human immunodeficiency virus type 1 (HIV-1) is selectively forced to acquire mutations in the reverse transcriptase (RT) gene. Some of these mutations are more common than others and have become markers for antiretroviral resistance. For the early detection of these markers, a novel MultiCode-RTx one-step testing system to rapidly and simultaneously characterize mixtures of HIV-1 targets was designed. For cDNA, nucleotide polymorphisms for codon M184V (ATG to GTG) and K65R (AAA to AGA) could be differentiated and quantified even when the population mixture varied as much as 1 to 10,000. Standard mixed-population curves using 1 to 100% of the mutant or wild type generated over 4 logs of total viral particle input did not affect the overall curves, making the method robust. The system was also applied to a small set of samples extracted from infected individuals on nucleoside reverse transcriptase inhibitor therapy. Of 13 samples tested, all were positive for HIV and 10 of the 13 genotypes determined were concordant with the line probe assay. MultiCode-RTx could be applied to other drug-selected mutations in the viral genome or for applications where single-base changes in DNA or RNA occur at frequencies reaching 0.01% to 1%, respectively.
Relationship between In Vitro Activities of Amphotericin B and Flucytosine and pH for Clinical Yeast and Mold Isolates
Authors: te Dorsthorst D. T. A. , Verweij P. E. , Meis J. F. G. M. , Mouton J. W. 
Published: July 2005

ABSTRACT

In this study, we investigated the pH dependency of the in vitro activities of amphotericin B (AMB) and flucytosine (5FC) against
Candida
spp.,
Cryptococcus neoformans
,
Aspergillus fumigatus
,
Rhizopus
spp., and
Scedosporium prolificans
in RPMI 1640 buffered with citrate buffer (pH 4.0, 5.0, 5.4, and 6.0), citrate-phosphate buffer (pH 5.4, 6.0, 6.4, and 7.0), and 3-[
N
-morpholino]propanesulfonic acid (MOPS) (pH 6.4, 7.0, 7.4, and 7.9). For 5FC, no significant differences were found between MICs obtained with the different buffers, while for AMB, significant differences were found. The MICs obtained with citrate-phosphate buffer were approximately 1 twofold-dilution step higher than the MICs obtained with MOPS. We demonstrated that the in vitro activities of AMB and 5FC against yeast and mold isolates were pH dependent. The in vitro activity of AMB decreased when the pH was lowered, while the in vitro activity of 5FC increased. The effect of the pH on the in vitro activities was dependent not only on the antifungal agent tested but also on the microorganism. For AMB, there was a nonlinear relationship (median
r
2
, 0.864) for
Candida
spp.,
C. neoformans
,
A. fumigatus
, and
Rhizopus
spp. over the pH range tested. The mean MICs ranged from 0.5 to 2.52 μg/ml at pH 7.0 and from 20.16 to 32 μg/ml at pH 5.0. For
S. prolificans
, there was no relationship. For 5FC, there was a linear relationship for
Candida
spp. (median
r
2
, 0.767) and a nonlinear relationship for
C. neoformans
and
A. fumigatus
(median
r
2
, 0.882) over the pH range tested. The mean MIC values ranged from 0.125 to 1,024 μg/ml at pH 7.0 and from 0.02 to 4 μg/ml at pH 5.0. For
Rhizopus
spp. and
S. prolificans
, the relationship could not be determined, since the MIC was >1,024 μg/ml over a pH range of 4.0 to 7.9.
Role of Efflux Pumps and Topoisomerase Mutations in Fluoroquinolone Resistance in
Campylobacter jejuni
and
Campylobacter coli
Authors: Ge Beilei , McDermott Patrick F. , White David G. , Meng Jianghong 
Published: July 2005

ABSTRACT

Point mutations in the topoisomerase (DNA gyrase A) gene are known to be associated with fluoroquinolone resistance in
Campylobacter
. Recent studies have shown that an efflux pump encoded by
cmeABC
is also involved in decreased susceptibilities to fluoroquinolones, as well as other antimicrobials. Genome analysis suggests that
Campylobacter jejuni
contains at least nine other putative efflux pumps. Using insertional inactivation and site-directed mutagenesis, we investigated the potential contributions of these pumps to susceptibilities to chloramphenicol, ciprofloxacin, erythromycin, and tetracycline in
C. jejuni
and
Campylobacter coli
. Insertional inactivation of
cmeB
resulted in 4- to 256-fold decreases in the MICs of chloramphenicol, ciprofloxacin, erythromycin, and tetracycline, with erythromycin being the most significantly affected. In contrast, inactivation of all other putative efflux pumps had no effect on susceptibility to any of the four antimicrobials tested. Mutation of
gyrA
at codon 86 (Thr-Ile) caused 128- and 64-fold increases in the MICs of ciprofloxacin and nalidixic acid, respectively. The replacement of the mutated
gyrA
with a wild-type
gyrA
allele resulted in a 32-fold decrease in the ciprofloxacin MIC and no change in the nalidixic acid MIC. Our findings indicate that CmeABC is the only efflux pump among those tested that influences antimicrobial resistance in
Campylobacter
and that a point mutation (Thr-86-Ile) in
gyrA
directly causes fluoroquinolone resistance in
Campylobacter
. These two mechanisms work synergistically in acquiring and maintaining fluoroquinolone resistance in
Campylobacter
species.
Population Pharmacokinetics of Tenofovir in Human Immunodeficiency Virus-Infected Patients Taking Highly Active Antiretroviral Therapy
Authors: Jullien Vincent , Tréluyer Jean-Marc , Rey Elisabeth , Jaffray Patrick , Krivine Anne , Moachon Laurence , Lillo-Le Louet Agnès , Lescoat Anne , Dupin Nicolas , Salmon Dominique , Pons Gérard , Urien Saïk 
Published: July 2005

ABSTRACT

The influence of renal function on tenofovir pharmacokinetics was investigated in 193 human immunodeficiency virus (HIV)-infected patients by the use of a population approach performed with the nonlinear mixed effects modeling program NONMEM. Tenofovir pharmacokinetics was well described by a two-compartment open model in which the absorption and the distribution rate constants are equal. Typical population estimates of apparent central distribution volume (

V
c

/
F
), peripheral distribution volume (

V
p

/
F
), intercompartmental clearance (
Q
/
F
), and plasma clearance (CL/
F
) were 534 liters, 1,530 liters, 144 liters/h and 90.9 liters/h, respectively. Apparent plasma clearance was related to body weight/serum creatinine ratio (BW/S
CR
) and to the existence of a tubular dysfunction. Concomitant treatment with lopinavir/ritonavir was found to decrease tenofovir clearance. Individual Bayesian estimates of CL/
F
were used to calculate the tenofovir area under the concentration-time curve from time zero to 24 h (AUC
0-24
). In patients without tubular dysfunction, AUC
0-24
values markedly decreased from 6.7 to 1.4 mg · h/liter for BW/S
CR
increasing from 0.44 to 1.73. The relevance of a dosage adjustment based on BW/S
CR
should be further evaluated.
Fluorescence Polarization Method To Characterize Macrolide-Ribosome Interactions
Authors: Yan Kang , Hunt Eric , Berge John , May Earl , Copeland Robert A. , Gontarek Richard R. 
Published: July 2005

ABSTRACTA fluorescence polarization assay is described that measures the binding of fluorescently labeled erythromycin to 70S ribosomes fromEscherichia coliand the displacement of the erythromycin from these ribosomes. The assay has been validated with several macrolide derivatives and other known antibiotics. We demonstrate that this assay is suitable for determining the dissociation constants of novel compounds that have binding sites overlapping those of macrolides. This homogeneous binding assay provides a valuable tool for defining structure-activity relationships among compounds during the discovery and development of new ribosome-targeting drugs.
Amprenavir and Efavirenz Pharmacokinetics before and after the Addition of Nelfinavir, Indinavir, Ritonavir, or Saquinavir in Seronegative Individuals
Authors: Morse Gene D. , Rosenkranz Susan , Para Michael F. , Segal Yoninah , DiFrancesco Robin , Adams Elizabeth , Brizz Barbara , Yarasheski Kevin E. , Reichman Richard C. 
Published: July 2005

ABSTRACTAdult AIDS Clinical Trials Group 5043 examined pharmacokinetic (PK) interactions between amprenavir (APV) and efavirenz (EFV) both by themselves and when nelfinavir (NFV), indinavir (IDV), ritonavir (RTV), or saquinavir (SQV) is added. A PK study was conducted after the administration of single doses of APV (day 0). Subjects (n= 56) received 600 mg of EFV every 24 h (q24h) for 10 days and restarted APV with EFV for days 11 to 13 with a PK study on day 14. A second protease inhibitor (PI) (NFV, 1,250 mg, q12h; IDV, 1,200 mg, q12h; RTV, 100 mg, q12h; or SQV, 1,600 mg, q12h) was added to APV and EFV on day 15, and a PK study was conducted on day 21. Controls continued APV and EFV without a second PI. Among subjects, the APV areas under the curve (AUCs) on days 0, 14, and 21 were compared using the Wilcoxon signed-rank test. Ninety-percent confidence intervals around the geometric mean ratios (GMR) were calculated. APV AUCs were 46% to 61% lower (median percentage of AUC) with EFV (day 14 versus day 0;Pvalues of <0.05). In the NFV, IDV, and RTV groups, day 21 APV AUCs with EFV were higher than AUCs for EFV alone. Ninety-percent confidence intervals around the GMR were 3.5 to 5.3 for NFV (P< 0.001), 2.8 to 4.5 for IDV (P< 0.001), and 7.8 to 11.5 for RTV (P= 0.004). Saquinavir modestly increased the APV AUCs (GMR, 1.0 to 1.4;P= 0.106). Control group AUCs were lower on day 21 compared to those on day 14 (GMR, 0.7 to 1.0;P= 0.042). African-American non-Hispanics had higher day 14 efavirenz AUCs than white non-Hispanics. We conclude that EFV lowered APV AUCs, but nelfinavir, indinavir, or ritonavir compensated for EFV induction.
Human Lactoferricin Is Partially Folded in Aqueous Solution and Is Better Stabilized in a Membrane Mimetic Solvent
Authors: Hunter Howard N. , Demcoe A. Ross , Jenssen Håvard , Gutteberg Tore J. , Vogel Hans J. 
Published: July 2005

ABSTRACTLactoferricins are highly basic bioactive peptides that are released in the stomach through proteolytic cleavage of various lactoferrin proteins. Here we have determined the solution structure of human lactoferricin (LfcinH) by conventional two-dimensional nuclear magnetic resonance methods in both aqueous solution and a membrane mimetic solvent. Unlike the 25-residue bovine lactoferricin (LfcinB), which adopts a somewhat distorted antiparallel β sheet, the longer LfcinH peptide shows a helical content from Gln14 to Lys29 in the membrane mimetic solvent but a nonexistent β-sheet character in either the N- or C-terminal regions of the peptide. The helical characteristic of the LfcinH peptide resembles the conformation that this region adopts in the crystal structure of the intact protein. The LfcinH structure determined in aqueous solution displays a nascent helix in the form of a coiled conformation in the region from Gln14 to Lys29. Numerous hydrophobic interactions create the basis for the better-defined overall structure observed in the membrane mimetic solvent. The 49-residue LfcinH peptide isolated for these studies was found to be slightly longer than previously reported peptide preparations and was found to have an intact peptide bond between residues Ala11 and Val12. The distinct solution structures of LfcinH and LfcinB represent a novel difference in the physical properties of these two peptides, which contributes to their unique physiological activities.