bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficacy of CS-758, a Novel Triazole, against Experimental Fluconazole-Resistant Oropharyngeal Candidiasis in Mice
Authors: Kamai Yasuki , Kubota Mikie , Fukuoka Takashi , Kamai Yoko , Maeda Naoyuki , Hosokawa Tsunemichi , Shibayama Takahiro , Uchida Katsuhisa , Yamaguchi Hideyo , Kuwahara Shogo 
Published: January 2003

ABSTRACT

The therapeutic efficacy of CS-758, a novel triazole, was evaluated against experimental murine oropharyngeal candidiasis induced by
Candida albicans
with various susceptibilities to fluconazole. Against infections induced by strains with various susceptibilities to fluconazole, the efficacy of fluconazole was strongly correlated with the MIC of fluconazole, as measured by the NCCLS method, and agreed with the NCCLS interpretive breakpoints, suggesting that the efficacies of new drugs could be predicted by using this model. The results of the fungal burden study corresponded with the results of the histopathological study. CS-758 exhibited potent in vitro activity (MICs, 0.004 to 0.06 μg/ml) against the strains used in this murine model including fluconazole-susceptible dose-dependent and fluconazole-resistant strains (fluconazole MICs, 16 to 64 μg/ml). CS-758 exhibited excellent efficacy against the infections induced by all the strains including a fluconazole-resistant strain, and the reductions in viable cell counts were significant at 10 and 50 mg/kg of body weight/dose. Fluconazole was not effective even at 50 mg/kg/dose against infections induced by a fluconazole-resistant strain (fluconazole MIC, 64 μg/ml). These results suggest that CS-758 is a promising compound for the treatment of oropharyngeal candidiasis including fluconazole-refractory infections.
NK-Lysin and Its Shortened Analog NK-2 Exhibit Potent Activities againstTrypanosoma cruzi
Authors: Jacobs Thomas , Bruhn Heike , Gaworski Iris , Fleischer Bernhard , Leippe Matthias 
Published: January 2003

ABSTRACTAntimicrobial peptides are widespread in nature and have been evolutionarily conserved as essential tools for combating a variety of pathogens. Among the plethora of natural peptides and synthetic analogs thereof studied in recent years for their antimicrobial activities, only a very few are known to be effective against protozoan parasites. In the present study we investigated the activity of NK-lysin, a broad-spectrum effector polypeptide of mammalian cytotoxic lymphocytes, against trypomastigotes of the human pathogenTrypanosoma cruziin vitro. Moreover, the activity of a synthetic peptide named NK-2 that corresponds to the cationic core region of NK-lysin was tested in parallel against this parasite.T. cruziwas found to be highly susceptible to both peptides, as evidenced by inhibition of the mobility of trypomastigotes. The peptides rapidly permeabilized the plasma membrane of the parasite since micromolar concentrations resulted in the release of cytosolic enzymes within minutes. NK-lysin and NK-2 were even found to kill trypanosomes residing inside the human glioblastoma cell line 86HG39, but only NK-2 left the host cells apparently unharmed.
Culture and Antibiotic Susceptibility of
Bartonella quintana
in Human Erythrocytes
Authors: Rolain Jean-Marc , Maurin Max , Mallet Marie-Noëlle , Parzy Daniel , Raoult Didier 
Published: January 2003

ABSTRACT

Bartonella quintana
, the agent of trench fever, has recently been implicated in various diseases, in particular, bacteremia and endocarditis in homeless people. The host cell of
Bartonella
spp. is believed to be the erythrocyte, and in the present study we demonstrate that
B. quintana
can be cultured in vitro in human erythrocytes. The bacteria were found to be intraerythrocytic by laser confocal microscopy with
Bartonella
species-specific monoclonal antibodies. Infections with
B. quintana
decreased the life span of erythrocytes in culture from 8.6 to 4.8 days. In the culture system we found that most of the antibiotics that we tested (doxycycline, fluoroquinolone compounds, and beta-lactams) were not bactericidal. Gentamicin was bactericidal at 4 μg/ml, as was rifampin, but to a lesser extent. At this concentration, gentamicin has been shown to enter erythrocytes slowly and to reach a peak level of 0.26 μg/ml after 24 h. At 0.26 μg/ml, however, we found that gentamicin was not able to kill extracellular
B. quintana
, even after 96 h of incubation. We hypothesize that erythrocytes may be a reservoir for
B. quintana
and that the bactericidal activity of gentamicin that we observed occurs mainly when the bacteria emerge from the erythrocytes and are found extracellularly. It would appear that gentamicin should be administered for at least 5 days to cure patients infected with
B. quintana
.
Effect of Amphotericin B on Larval Growth of
Echinococcus multilocularis
Authors: Reuter Stefan , Merkle Marion , Brehm Klaus , Kern Peter , Manfras Burkhard 
Published: January 2003

ABSTRACT

Alveolar echinococcosis is caused by the parasitic cestode
Echinococcus multilocularis
. Benzimidazoles, namely, mebendazole and albendazole, are the only drugs available for the treatment of inoperable alveolar echinococcosis. At present, no therapeutic alternative is available for patients with progressive disease under treatment or for patients who are unable to tolerate the side effects of the benzimidazoles. In addition, benzimidazoles are only parasitostatic for
E. multilocularis
. Thus, new therapeutic options are of paramount importance. In the present study we examined the in vitro effect of amphotericin B on
E. multilocularis
larvae.
E. multilocularis
metacestodes grown in the peritoneal cavities of Mongolian gerbils were transferred into a culture system. Vesicles budded from the tissue blocks and increased in number and size during the first 5 weeks. After 6 weeks drugs were added and deleterious effects on the vesicles were observed macroscopically and microscopically. By use of this in vitro tissue culture model we demonstrated that amphotericin B effectively inhibits the growth of
E. multilocularis
metacestodes. This destructive effect was significantly more rapid with amphotericin B than with the benzimidazoles. Cyclic treatment was effective in suppressing parasite growth. However, amphotericin B appears to be parasitostatic for
E. multilocularis
larvae, and regrowth occurs even after extended periods. In summary, amphotericin B constitutes the first promising alternative for the treatment of alveolar echinococcosis in cases of intolerance or resistance to benzimidazoles. It holds promise as an effective treatment option for otherwise fatal courses of disease.
Pharmacokinetics (PK), Pharmacodynamics (PD), and PK-PD Integration of Danofloxacin in Sheep Biological Fluids
Authors: Aliabadi F. Shojaee , Landoni M. F. , Lees P. 
Published: January 2003

ABSTRACTThe fluoroquinolone antimicrobial drug danofloxacin was administered to sheep intravenously (i.v.) and intramuscularly (i.m.) at a dose of 1.25 mg/kg of body weight in a two-period crossover study. The pharmacokinetic properties of danofloxacin in serum, inflamed tissue cage fluid (exudate), and noninflamed tissue cage fluid (transudate) were established by using a tissue cage model. The in vitro and ex vivo activities of danofloxacin in serum, exudate, and transudate against a pathogenic strain ofMannheimia haemolyticawere established. Integration of in vivo pharmacokinetic data with the in vitro MIC provided mean values for the area under the curve (AUC)/MIC for serum, exudate, and transudate of 60.5, 85.6, and 45.7 h, respectively, after i.v. dosing and 55.9, 77.9, and 49.1 h, respectively, after i.m. dosing. After i.m. dosing, the maximum concentration/MIC ratios for serum, exudate, and transudate were 10.8, 3.0, and 1.6, respectively. The ex vivo growth inhibition data after i.m. dosing were fitted to the inhibitory sigmoidEmaxequation to provide the values of AUC/MIC required to produce bacteriostasis, bactericidal activity, and elimination of bacteria. The respective values for serum were 17.8, 20.2, and 28.7 h, and slightly higher values were obtained for transudate and exudate. It is proposed that use of these data might provide a novel approach to the rational design of dosage schedules.
Methodologies and Cell Lines Used for Antimicrobial Susceptibility Testing of
Chlamydia
spp
Authors: Suchland R. J. , Geisler W. M. , Stamm Walter E. 
Published: January 2003

ABSTRACT

In vitro susceptibility testing was performed on strains of
Chlamydia trachomatis
,
Chlamydia pneumoniae
, and
Chlamydia psittaci
under various conditions, including the cell line utilized, the time between infection and the addition of an antimicrobial, the concentration of inoculum, and the effect of multiple passage on the minimal chlamydicidal concentrations for the antibiotics doxycycline, azithromycin, erythromycin, ofloxacin, and tetracycline. With macrolides, the MIC varied depending upon the cell line utilized. With all antimicrobials, the MIC was related to the time at which the antimicrobial was added after infection. By an optimized cell culture passage method, all strains of chlamydia tested demonstrated survival after exposure to high levels (>100 times the MIC) of antimicrobials. Furthermore, upon retest, these surviving organisms did not demonstrate increased MICs. Thus, this phenomenon does not reflect selection of antimicrobial-resistant mutants but rather survival of some organisms in high antimicrobial concentrations (heterotypic survival). An additional 44 clinical isolates of
C. trachomatis
from patients with single-incident infections were tested against those from patients with recurrent or persistent infections, and heterotypic survival was seen in all isolates tested; hence, in vitro resistance did not correlate with the patient's apparent clinical outcome.
MUC7 20-Mer: Investigation of Antimicrobial Activity, Secondary Structure, and Possible Mechanism of Antifungal Action
Authors: Bobek Libuse A. , Situ Hongsa 
Published: January 2003

ABSTRACT

This study was aimed at examining the spectrum of antimicrobial activity of MUC7 20-mer (N-LAHQKPFIRKSYKCLHKRCR-C; residues 32 to 51 of MUC7, the low-molecular-weight human salivary mucin, comprised of 357 residues) and comparing its antifungal properties to those of salivary histatin 5 (Hsn-5). We also examined the secondary structure of the 20-mer and the possible mechanism of its antifungal action. Our results showed that MUC7 20-mer displays potent killing activity against a variety of fungi and both gram-positive and gram-negative bacteria at micromolar concentrations. Time-dependent killing of
Candida albicans
and
Cryptococcus neoformans
by MUC7 20-mer and Hsn-5 indicated differences in killing rates between MUC7 20-mer and Hsn-5. The secondary structure prediction showed that MUC7 20-mer adopts an amphiphilic helix with distinguishable hydrophilic and hydrophobic faces (a characteristic that is associated with antimicrobial activity). In comparison to that of Hsn-5, the fungicidal activity of MUC7 20-mer against
C. albicans
seems to be independent of fungal cellular metabolic activity, as evidenced by its killing potency at a low temperature (4°C) and in the presence of inhibitors of oxidative phosphorylation in the mitochondrial system. Fluorescence microscopy showed the ability of MUC7 20-mer to cross the fungal cell membrane and to accumulate inside the cells. The internalization of MUC7 20-mer was inhibited by divalent cations. Confocal microscopy of cells doubly labeled with MUC7 20-mer and a mitochondrion-specific dye indicated that mitochondria are not the target of MUC7 20-mer for either
C. albicans
or
C. neoformans
.
Sterilizing Activities of Fluoroquinolones against Rifampin-Tolerant Populations of
Mycobacterium tuberculosis
Authors: Hu Yanmin , Coates Anthony R. M. , Mitchison Denis A. 
Published: January 2003

ABSTRACT

The bactericidal activities of ciprofloxacin, ofloxacin, levofloxacin, moxifloxacin, and gatifloxacin were tested in three models of rifampin-tolerant
Mycobacterium tuberculosis
persisters. Model 1 was a 100-day-old, unshaken, anaerobically adapted culture in which serial dilutions of the quinolones were incubated for 5 days and CFU counts were then done In models 2 and 3, 100 mg of rifampin/liter was added to the 100-day culture for 5 or 7 days to produce tolerant organisms that did not grow on plates; the rifampin was then washed off, fresh medium was added to allow recovery of growth on plates, and the culture was incubated for 7 days before CFU counts. In model 2, the quinolones were added after rifampin had been washed off, whereas in model 3 the quinolones were added to the cultures containing rifampin. In models 1 and 2, ciprofloxacin had the least bactericidal activity, ofloxacin and levofloxacin had greater activities, and moxifloxacin and gatifloxacin had the greatest activities. In model 3, ofloxacin had no detectable activity whereas moxifloxacin killed about log
10
0.279 CFU of the persisters per ml at concentrations attainable in lesions; isoniazid had virtually no activity. These findings predict that ofloxacin will not be found to have effective sterilizing activity in clinical studies now planned whereas moxifloxacin will be able to shorten treatment.
RWJ-54428 (MC-02,479), a New Cephalosporin with High Affinity for Penicillin-Binding Proteins, Including PBP 2a, and Stability to Staphylococcal Beta-Lactamases
Authors: Malouin Francois , Blais Johanne , Chamberland Suzanne , Hoang Monica , Park Craig , Chan Christin , Mathias Kristina , Hakem Samia , Dupree Kelly , Liu Eric , Nguyen Tien , Dudley Michael N. 
Published: January 2003

ABSTRACT

RWJ-54428 (MC-02,479) is a new cephalosporin active against gram-positive bacteria, including methicillin-resistant
Staphylococcus aureus
(MRSA). The potency of this new cephalosporin against MRSA is related to a high affinity for penicillin-binding protein 2a (PBP 2a), as assessed in a competition assay using biotinylated ampicillin as the reporter molecule. RWJ-54428 had high activity against MRSA strains COL and 67-0 (MIC of 1 μg/ml) and also showed affinity for PBP 2a, with a 50% inhibitory concentration (IC
50
) of 0.7 μg/ml. RWJ-54428 also displayed excellent affinity for PBP 5 from
Enterococcus hirae
R40, with an IC
50
of 0.8 μg/ml and a MIC of 0.5 μg/ml. The affinity of RWJ-54428 for PBPs of β-lactam-susceptible
S. aureus
(MSSA), enterococci (
E. hirae
), and
Streptococcus pneumoniae
showed that the good affinity of RWJ-54428 for MRSA PBP 2a and
E. hirae
PBP 5 does not compromise its binding to susceptible PBPs. RWJ-54428 showed stability to hydrolysis by purified type A β-lactamase isolated from
S. aureus
PC1. In addition, RWJ-54428 displayed low MICs against strains of
S. aureus
bearing the four classes of staphylococcal β-lactamases, including β-lactamase hyperproducers. The frequency of isolation of resistant mutants to RWJ-54428 from MRSA strains was very low. In summary, RWJ-54428 has high affinity to multiple PBPs and is stable to β-lactamase, properties that may explain our inability to find resistance by standard methods. These data are consistent with its excellent activity against β-lactam-resistant gram-positive bacteria.
AcrAB Multidrug Efflux Pump Is Associated with Reduced Levels of Susceptibility to Tigecycline (GAR-936) in
Proteus mirabilis
Authors: Visalli Melissa A. , Murphy Ellen , Projan Steven J. , Bradford Patricia A. 
Published: January 2003

ABSTRACT

Tigecycline has good broad-spectrum activity against many gram-positive and gram-negative pathogens with the notable exception of the
Proteeae
. A study was performed to identify the mechanism responsible for the reduced susceptibility to tigecycline in
Proteus mirabilis
. Two independent transposon insertion mutants of
P. mirabilis
that had 16-fold-increased susceptibility to tigecycline were mapped to the
acrB
gene homolog of the
Escherichia coli
AcrRAB efflux system. Wild-type levels of decreased susceptibility to tigecycline were restored to the insertion mutants by complementation with a clone containing a PCR-derived fragment from the parental wild-type
acrRAB
efflux gene cluster. The AcrAB transport system appears to be associated with the intrinsic reduced susceptibility to tigecycline in
P. mirabilis
.
Isoniazid Activation Defects in Recombinant
Mycobacterium tuberculosis
Catalase-Peroxidase (KatG) Mutants Evident in InhA Inhibitor Production
Authors: Wei Chih-Jen , Lei Benfang , Musser James M. , Tu Shiao-Chun 
Published: January 2003

ABSTRACT

Mycobacterium tuberculosis
KatG catalyzes the activation of the antitubercular agent isoniazid to yield an inhibitor targeting enoyl reductase (InhA). However, no firm biochemical link between many KatG variants and isoniazid resistance has been established. In the present study, six distinct KatG variants identified in clinical
Mycobacterium tuberculosis
isolates resistant to isoniazid were generated by site-directed mutagenesis, and the recombinant mutant proteins (KatG
A110V
, KatG
A139P
, KatG
S315N
, KatG
L619P
, KatG
L634F
, and KatG
D735A
) were purified and characterized with respect to their catalase-peroxidase activities (in terms of
k
cat
/

K
m

), rates of free-radical formation from isoniazid oxidation, and, moreover, abilities to activate isoniazid. The A110V amino acid replacement did not result in significant alteration of KatG activities except that the peroxidase activity was enhanced. The other mutations, however, resulted in modestly reduced catalase and peroxidase catalytic efficiencies and, for the four mutants tested, significantly lower activities to oxidize isoniazid. Compared to the wild-type enzyme, the ability of the KatG
L634F
, KatG
A139P
, and KatG
D735A
variants to activate isoniazid decreased by 36%, 76%, and 73%, respectively, whereas the KatG
S315N
and KatG
L619P
variants completely lost their abilities to convert isoniazid into the InhA inhibitor. In addition, the inclusion of exogenous Mn
2+
to the isoniazid activation reaction mix significantly improved the ability of wild-type and KatG mutants to produce the InhA inhibitor.
Genome-Wide Screening ofSaccharomyces cerevisiaeTo Identify Genes Required for Antibiotic Insusceptibility of Eukaryotes
Authors: Blackburn Alexandra S. , Avery Simon V. 
Published: January 2003

ABSTRACTThe adverse reactions provoked by many antibiotics in humans are well documented but are generally poorly understood at the molecular level. To elucidate potential genetic defects that could give rise to susceptibility to prokaryote-specific antibiotics in eukaryotes, we undertook genome-wide screens using the yeastSaccharomyces cerevisiaeas a model of eukaryotes; our previous work with a small number of yeast mutants revealed some specific gene functions required for oxytetracycline resistance. Here, the complete yeast deletion strain collection was tested for growth in the presence of a range of antibiotics. The sensitivities of mutants revealed by these screens were validated in independent tests. None of the ∼4,800 defined deletion strains tested were found to be sensitive to amoxicillin, penicillin G, rifampin, or vancomycin. However, two of the yeast mutants were tetracycline sensitive and four were oxytetracycline sensitive; encompassed among the latter were mutants carrying deletions in the same genes that we had characterized previously. Seventeen deletion strains were found to exhibit growth defects in the presence of gentamicin, with MICs for the strains being as low as 32 μg ml−1(the wild type exhibited no growth defects at any gentamicin concentration tested up to 512 μg ml−1). Strikingly, 11 of the strains that were most sensitive to gentamicin carried deletions in genes whose products are all involved in various aspects of vacuolar and Golgi complex (or endoplasmic reticulum) function. Therefore, these and analogous organelles, which are also the principal sites of gentamicin localization in human cells, appear to be essential for normal resistance to gentamicin in eukaryotes. The approach and data described here offer a new route to gaining insight into the potential genetic bases of antibiotic insusceptibilities in eukaryotes.
Tandem Amplification of a 28-Kilobase Region from the
Yersinia enterocolitica
Chromosome Containing the
blaA
Gene
Authors: Seoane Asunción , Sánchez Emilia , García-Lobo Juan M. 
Published: January 2003

ABSTRACT

Most
Yersinia enterocolitica
strains are resistant to β-lactam antibiotics due to the production of one or two chromosomally encoded β-lactamases. Strain Y56 is a
Y. enterocolitica
O:3 serotype natural isolate that is resistant to moderate amounts of penicillins and that produces a single class A β-lactamase. To select mutants with increased levels of resistance to β-lactam antibiotics, strain Y56 was grown on plates containing increasing amounts of ampicillin, and variants resistant to up to 500 μg of ampicillin per ml were obtained. Chromosomal DNA from hyperresistant isolates was analyzed by Southern hybridization with a
blaA
-specific probe to detect gene rearrangements. The use of pulsed-field gel electrophoresis revealed that the increase in the resistance level correlated with the amplification in tandem of a DNA fragment of about 28 kb containing the
blaA
gene. The phenotype of these isolates was not stable, and they recovered the basal low resistance level when the ampicillin used for selection was withdrawn from the growth medium. This loss of resistance was followed by the recovery of the original chromosomal structure. To understand this amplification process, the 28-kb amplification unit was cloned, and the ends were sequenced. The analysis of these sequences did not reveal the presence of either repeats or transposable elements to explain this process. However, we found short sequences similar to some DNA gyrase target sequences that have been described. In addition, we observed that the frequency of appearance of ampicillin-hyperresistant isolates by amplification of the
blaA
locus was lowered in the presence of the gyrase inhibitor novobiocin. These findings suggest that the DNA gyrase could be involved in this amplification event.
Effects of Organic Anion, Organic Cation, and Dipeptide Transport Inhibitors on Cefdinir in the Isolated Perfused Rat Kidney
Authors: Lepsy Christopher S. , Guttendorf Robert J. , Kugler Alan R. , Smith David E. 
Published: January 2003

ABSTRACTCefdinir (Omnicef; Abbott Laboratories) is a cephalosporin antibiotic primarily eliminated by the kidney. Nonlinear renal elimination of cefdinir has been previously reported. Cefdinir renal transport mechanisms were studied in the erythrocyte-free isolated perfused rat kidney. Studies were performed with drug-free perfusate and perfusate containing cefdinir alone to establish the baseline physiology and investigate cefdinir renal elimination characteristics. To investigate cefdinir renal transport mechanisms, inhibition studies were conducted by coperfusing cefdinir with inhibitors of the renal organic anion (probenecid), organic cation (tetraethylammonium), or dipeptide (glycylsarcosine) transport system. Cefdinir concentrations in biological samples were determined using reversed-phase high-performance liquid chromatography. Differences between treatments and controls were evaluated using analysis of variance and Dunnett's test. The excretion ratio (ER; the renal clearance corrected for the fraction unbound and glomerular filtration rate) for cefdinir was 5.94, a value indicating net renal tubular secretion. Anionic, cationic, and dipeptide transport inhibitors all significantly affected the cefdinir ER. With probenecid, the ER was reduced to 0.59, clearly demonstrating a significant reabsorptive component to cefdinir renal disposition. This finding was confirmed by glycylsarcosine studies, in which the ER was elevated to 7.95, indicating that reabsorption was mediated, at least in part, by the dipeptide transporter system. The effects of the organic cation tetraethylammonium, in which the ER was elevated to 7.53, were likely secondary in nature. The anionic secretory pathway was found to be the predominant mechanism for cefdinir renal excretion.