bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficacy of LY303366 against Amphotericin B-Susceptible and -Resistant
Aspergillus fumigatus
in a Murine Model of Invasive Aspergillosis
Authors: Verweij Paul E. , Oakley Karen L. , Morrissey Jacqui , Morrissey Graham , Denning David W. 
Published: October 2018

ABSTRACT

LY303366 is a novel antifungal echinocandin with excellent in vitro activity against
Aspergillus
spp. We compared four doses (1, 2.5, 10, and 25 mg/kg of body weight) of LY303366 with amphotericin B (0.5 to 5 mg/kg) in a temporarily neutropenic murine model of invasive aspergillosis against an amphotericin B-susceptible (AF210) and an amphotericin B-resistant (AF65)
Aspergillus fumigatus
isolate based on in vivo response. Mice were immunosuppressed with cyclophosphamide (200 mg/kg) and infected 3 days later. Treatment started 18 h after infection and lasted for 10 days. LY303366 was given once daily intravenously for 10 days, and amphotericin B (at 0.5, 2, and 5 mg/kg) was given once daily intraperitoneally for 10 days, or only on days 1, 2, 4, and 7 (at 5 mg/kg). Kidneys and lungs from survivors were cultured on day 11. Control mice in both experiments had 90 to 100% mortality. Amphotericin B at 0.5 mg/kg and LY303366 at 1 mg/kg yielded 10 to 20% survival rates for mice infected with either AF210 or AF65. Amphotericin B at 2 and 5 (both regimens) mg/kg yielded a 70 to 100% survival rate for mice infected with AF210 but a 10 to 30% survival rate for mice infected with AF65 (
P
= 0.01 to 0.04 compared with AF210). Against AF210 and AF65, LY303366 at 2.5, 10, and 25 mg/kg produced a survival rate of 70 to 80%, which was as effective as amphotericin B for AF210, but superior to amphotericin B for AF65 (
P
< 0.03 to 0.0006). For AF65, LY303366 at 10 and 25 mg/kg/day was superior to amphotericin B at 2 and 5 mg/kg/day in reducing tissue colony counts (
P
= 0.01 to 0.003), and for AF210, amphotericin B at 5 mg/kg/day and at 5 mg/kg in four doses was more effective than all four regimens of LY303366 in reducing renal culture counts (
P
= 0.01 to 0.0001). The present study shows, for the first time, that in vivo resistance of
A. fumigatus
to amphotericin B exists, although this could not be detected by in vitro susceptibility assays. Furthermore, LY303366 appears to be effective against amphotericin B-susceptible and -resistant
A. fumigatus
infection in this model and should be further evaluated clinically.
Use of a Rapid Throughput In Vivo Screen To Investigate Inhibitors of Eukaryotic Topoisomerase II Enzymes
Authors: Hammonds Timothy R. , Maxwell Anthony , Jenkins John R. 
Published: October 2018

ABSTRACT

Topoisomerase II catalyzes the passage of one DNA helix through another via a transient double-stranded break. The essential nature of this enzyme in cell proliferation and its mechanism of action make it an ideal target for cytotoxic agents.
Saccharomyces cerevisiae
topoisomerase II has been frequently used as a model for testing potential inhibitors of eukaryotic topoisomerase II as antitumor agents. The standard in vivo method of estimating the sensitivity of
S. cerevisiae
to the antitopoisomerase drugs is via inhibition or kill curves which rely on viable-cell counts and is labor intensive. We present an alternative to this, a high-throughput in vivo screen. This method makes use of a drug-permeable
S. cerevisiae
strain lacking endogenous topoisomerase II, which is modified to express either human topoisomerase IIα or IIβ or
S. cerevisiae
topoisomerase II carried on plasmids. Each modified strain expresses a full-length topoisomerase II enzyme, as opposed to the more commonly used temperature-sensitive
S. cerevisiae
mutant expressing yeast or yeast/human hybrid enzymes. A comparison of this new method with a plating-and-counting method gave similar drug sensitivity results, with increased accuracy and reduced manual input for the new method. The information generated has highlighted the sensitivities of different topoisomerase II enzymes and isoenzymes to several different classes of topoisomerase II inhibitor.
Increased Overall Antibiotic Susceptibility in
Staphylococcus aureus femAB
Null Mutants
Authors: Ling Baodong , Berger-Bächi Brigitte 
Published: October 2018

ABSTRACT

The staphylococcal pentaglycine side chain of the peptidoglycan is reduced to one glycine in
femAB
null mutants. This is associated with increased susceptibility to methicillin and to a whole range of unrelated antibiotics as well. Genetic evidence suggests that
femAB
null mutants are only viable because of a compensatory mutation in an unlinked site.
Identification ofSaccharomyces cerevisiaeGenes Conferring Resistance to Quinoline Ring-Containing Antimalarial Drugs
Authors: Delling Ulrike , Raymond Martine , Schurr Erwin 
Published: October 2018

ABSTRACTTo identify genes that can confer resistance to antimalarial drugs in yeast, we transformed the quinidine-sensitive strain CYX247-9A ofSaccharomyces cerevisiaewith a yeast genomic library and selected for transformants that grow in the presence of elevated levels of antimalarial drugs. Plasmids were rescued from such clones and were analyzed for the presence of individual open reading frames that can confer drug resistance. Using quinidine as the selective drug, we were able to identify three genes that can cause resistance to antimalarial drugs. Overexpression of the yeast genesCIN5(a member of the family of bZIP transcription factors),STI1(a Hsp90 cochaperone), andYOR273c(a member of the major facilitator superfamily of transmembrane transporters) conferred 3.9-, 7.0-, and 4.3-fold resistance to quinidine, respectively, over that of control yeast. Cross-resistance assays determined thatSTI1also conferred resistance to mefloquine (3.4-fold), whileCIN5also conferred resistance to mefloquine (9.6-fold) and chloroquine (5.4-fold). Using mefloquine as the selective drug, we determined that overexpression ofYBR233w, a member of the hnRNPK family of nuclear RNA binding proteins, conferred resistance to mefloquine (13.5-fold). Expression of the humanhnRNPKhomolog ofYBR233winS. cerevisiaealso conferred mefloquine resistance, suggesting that homologs of the identified resistance genes may perform similar functions in species other than yeast. Our experiments have identified heretofore unknown pathways of resistance to quinoline ring-containing antimalarial drugs inS. cerevisiae.
A237T as a Modulating Mutation in Naturally Occurring Extended-Spectrum TEM-Type β-Lactamases
Authors: Blázquez Jesús , Negri María-Cristina , Morosini María-Isabel , Gómez-Gómez J. M. , Baquero Fernando 
Published: October 2018

ABSTRACT

A TEM-1 β-lactamase derivative containing the single amino acid substitution A237T slightly increased (from 24 to 32 μg/ml) the cephalothin MIC for
Escherichia coli
RYC1000 but did not influence the activities of cefotaxime, ceftazidime, and aztreonam (MICs of 0.03, 0.12, and 0.06 μg/ml, respectively). Despite its apparent neutrality, addition of the A237T mutation to the pair of mutations characterizing TEM-10 (R164S and E240K) had a strong effect on substrate preference. Ceftazidime and aztreonam MICs decreased from 128 and 16 μg/ml to 16 and 2 μg/ml, respectively. In contrast, the cefotaxime MIC increased from 0.5 to 4 μg/ml. The acquisition of apparently neutral or even deleterious mutations results in a very effective mechanism of resistance to different β-lactams that may be simultaneously or subsequently present in the environment. We propose here that the mutation in position 237 is an example of a modulating mutation and that consideration of this type of mutation may be important for understanding the evolution of β-lactamases.
Sulfonamide Resistance in
Streptococcus pyogenes
Is Associated with Differences in the Amino Acid Sequence of Its Chromosomal Dihydropteroate Synthase
Authors: Swedberg Göte , Ringertz Signe , Sköld Ola 
Published: October 2018

ABSTRACT

Sulfonamide resistance in recent isolates of
Streptococcus pyogenes
was found to be associated with alterations of the chromosomally encoded dihydropteroate synthase (DHPS). There were 111 different nucleotides (13.8%) in the genes found in susceptible and resistant isolates, respectively, resulting in 30 amino acid changes (11.3%). These substantial changes suggested the possibility of a foreign origin of the resistance gene, in parallel to what has already been found for sulfonamide resistance in
Neisseria meningitidis
. The gene encoding DHPS was linked to at least three other genes encoding enzymes of the folate pathway. These genes were in the order GTP cyclohydrolase, dihydropteroate synthase, dihydroneopterin aldolase, and hydroxymethyldihydropterin pyrophosphokinase. The nucleotide differences in genes from resistant and susceptible strains extended from the beginning of the GTP cyclohydrolase gene to the end of the gene encoding DHPS, an additional indication for gene transfer in the development of resistance. Kinetic measurements established different affinities for sulfathiazole for DHPS enzymes isolated from resistant and susceptible strains.
Five-Day Cefdinir Treatment for Streptococcal Pharyngitis
Authors: Tack Kenneth J. , Henry Daniel C. , Gooch W. Manford , Brink Douglas N. , Keyserling Constance H. , Group The Cefdinir Pharyngitis Study 
Published: October 2018

ABSTRACT

A multicenter, randomized, controlled, investigator-blind study was performed to evaluate the safety and efficacy of oral cefdinir versus oral penicillin V for the treatment of pharyngitis due to group A beta-hemolytic streptococci (GABHS). Patients 13 years of age and older were randomized to receive either oral cefdinir (300 mg twice a day) for 5 days followed by placebo for 5 days or oral penicillin V (250 mg four times a day) for 10 days. Throat cultures were obtained, and signs and symptoms of pharyngitis were recorded at study admission and follow-up visits on study days 11 to 15, 16 to 20, and 25 to 31. Patients kept a diary to record medication intake and their assessment of throat pain at admission and at each day of study treatment. Five hundred fifty-eight patients were enrolled, of whom 432 (77.4%) were clinically and microbiologically evaluable. The GABHS eradication rates 5 to 10 days after completion of therapy were 193 of 218 (88.5%) in the cefdinir group and 176 of 214 (82.2%) in the penicillin group (
P
= 0.053). Clinical cure rates were 89.0 and 84.6%, respectively (
P
= 0.80). By the time of the long-term follow-up visit, 2 to 3 weeks after completion of treatment, 156 of 191 (81.7%) of the assessable cefdinir patients and 152 of 195 (77.9%) of the penicillin patients remained free of GABHS. Both treatments were well tolerated, with adverse reaction rates of 18.3% in the cefdinir study arm and 15.0% in the penicillin study arm (
P
= 0.278). Five-day treatment with cefdinir is safe and effective therapy for GABHS pharyngitis. Based on its twice-a-day dosage and shorter course of therapy, leading to potentially greater patient compliance, cefdinir may be considered for use in the treatment of pharyngitis caused by GABHS.
Pharmacodynamics of Fluconazole in a Murine Model of Systemic Candidiasis
Authors: Louie Arnold , Drusano George L. , Banerjee Partha , Liu Qing-Feng , Liu Weiguo , Kaw Pamela , Shayegani Mehdi , Taber Harry , Miller Michael H. 
Published: October 2018

ABSTRACT

In this study we defined the pharmacodynamic parameter that optimizes outcome in deep-seated
Candida albicans
infections treated with fluconazole. Using a murine model of systemic candidiasis, we conducted single-dose dose-ranging studies with fluconazole to determine the dosage of this drug that resulted in a 50% reduction in fungal densities (50% effective dose [ED
50
]) in kidneys versus the fungal densities in the kidneys of untreated controls. We found that the ED
50
of fluconazole given intraperitoneally was 4.56 mg/kg of body weight/day (95% confidence interval, 3.60 to 5.53 mg/kg/day), and the dose-response relationship was best described by an inhibitory sigmoid maximal effect (
E
max
) curve. To define the pharmacodynamics of fluconazole, we gave dosages lower than, approximating, and higher than the ED
50
of fluconazole (range, 3.5 to 5.5 mg/kg/day, equivalent to the ED
16
to the ED
75
) to various groups of infected animals using three dose-fractionation schedules. For each total dose of fluconazole examined, the dose-fractionation schedules optimized the ratio of the area under the concentration-time curve (AUC) to the MIC (the AUC/MIC ratio), the ratio of the maximum concentration of drug in serum (
C
max
) to the MIC, and the time that the drug remained above the MIC for the infecting
C. albicans
isolate. Similar reductions in fungal densities in kidneys were seen between groups that received the same total dose of fluconazole in one, two, or four equally divided doses. Thus, dose-fractionation studies demonstrated that the pharmacodynamic parameter of fluconazole that best predicted outcome was the AUC/MIC ratio.
CNI-H0294, a Nuclear Importation Inhibitor of the Human Immunodeficiency Virus Type 1 Genome, Abrogates Virus Replication in Infected Activated Peripheral Blood Mononuclear Cells
Authors: Haffar Omar K. , Smithgall Molly D. , Popov Serguei , Ulrich Peter , Bruce A. Gregory , Nadler Steven G. , Cerami Anthony , Bukrinsky Michael I. 
Published: October 2018

ABSTRACTActive nuclear importation of the human immunodeficiency virus (HIV) type 1 (HIV-1) preintegration complex (PIC) is required for the productive infection of nondividing cells, but it is believed to be dispensable for the infection of proliferating cells, such as activated T lymphocytes. To investigate this question, we exploited the properties of the small arylene bis (methyl ketone) compound CNI-H0294. We have previously shown that this compound associated with the HIV-1 matrix protein nuclear localization sequence and blocked binding of the HIV-1 PIC to yeast karyopherin α. CNI-H0294 abrogated nuclear importation of the HIV-1 genome in macrophages and effectively inhibited infection of nondividing cells. In this study we demonstrate that CNI-H0294 inhibits binding of the HIV-1 PIC to human karyopherin α and reduces nuclear importation of the viral genome in primary peripheral blood mononuclear cells (PBMCs). We also demonstrate that CNI-H0294 inhibits acute infection of PBMC cultures in vitro with a primary isolate of HIV-1 and reduces virus replication and virus load in cultures of endogenously infected PBMCs from seropositive individuals. Thus, as for infection of nondividing, terminally differentiated macrophages, HIV-1 uses active nuclear importation of the virus genome to infect activated CD4+T cells. These results support nuclear importation as a novel target and CNI-H0294 and its derivatives as novel compounds for therapeutic intervention in HIV infection and AIDS.
Sequencing, Disruption, and Characterization of the
Candida albicans
Sterol Methyltransferase (
ERG6
) Gene: Drug Susceptibility Studies in
erg6
Mutants
Authors: Jensen-Pergakes K. L. , Kennedy M. A. , Lees N. D. , Barbuch R. , Koegel C. , Bard M. 
Published: October 2018

ABSTRACT

The rise in the frequency of fungal infections and the increased resistance noted to the widely employed azole antifungals make the development of new antifungals imperative for human health. The sterol biosynthetic pathway has been exploited for the development of several antifungal agents (allylamines, morpholines, azoles), but additional potential sites for antifungal agent development are yet to be fully investigated. The sterol methyltransferase gene (
ERG6
) catalyzes a biosynthetic step not found in humans and has been shown to result in several compromised phenotypes, most notably markedly increased permeability, when disrupted in
Saccharomyces cerevisiae
. The
Candida albicans ERG6
gene was isolated by complementation of a
S. cerevisiae erg6
mutant by using a
C. albicans
genomic library. Sequencing of the
Candida ERG6
gene revealed high homology with the
Saccharomyces
version of
ERG6
. The first copy of the
Candida ERG6
gene was disrupted by transforming with the
URA3
blaster system, and the second copy was disrupted by both
URA3
blaster transformation and mitotic recombination. The resulting
erg6
strains were shown to be hypersusceptible to a number of sterol synthesis and metabolic inhibitors, including terbinafine, tridemorph, fenpropiomorph, fluphenazine, cycloheximide, cerulenin, and brefeldin A. No increase in susceptibility to azoles was noted. Inhibitors of the
ERG6
gene product would make the cell increasingly susceptible to antifungal agents as well as to new agents which normally would be excluded and would allow for clinical treatment at lower dosages. In addition, the availability of
ERG6
would allow for its use as a screen for new antifungals targeted specifically to the sterol methyltransferase.
Comparative Activities of Clinafloxacin against Gram-Positive and -Negative Bacteria
Authors: Ednie Lois M. , Jacobs Michael R. , Appelbaum Peter C. 
Published: October 2018

ABSTRACT
Activities of clinafloxacin, ciprofloxacin, levofloxacin, sparfloxacin, trovafloxacin, piperacillin, piperacillin-tazobactam, trimethoprim-sulfamethoxazole, ceftazidime, and imipenem against 354 ciprofloxacin-susceptible and -intermediate-resistant organisms were tested by agar dilution. Clinafloxacin yielded the lowest quinolone MICs (≤0.5 μg/ml against ciprofloxacin-susceptible organisms and ≤16.0 μg/ml against ciprofloxacin-intermediate-resistant organisms) compared to those of levofloxacin, trovafloxacin, and sparfloxacin. Ceftazidime, piperacillin alone or combined with tazobactam, trimethoprim-sulfamethoxazole, and imipenem usually yielded higher MICs against ciprofloxacin-resistant strains.
Antibacterial Activities and Inhibitory Effects of Sitafloxacin (DU-6859a) and Its Optical Isomers against Type II Topoisomerases
Authors: Akasaka Takaaki , Kurosaka Seiko , Uchida Yoko , Tanaka Mayumi , Sato Kenichi , Hayakawa Isao 
Published: October 2018

ABSTRACT

The in vitro inhibitory effects of sitafloxacin (DU-6859a) and its three stereoisomers on bacterial DNA gyrase from
Escherichia coli
, topoisomerase IV from
Staphylococcus aureus
, and topoisomerase II from human placenta were compared. No correlation was observed between the inhibitory activities of quinolones against bacterial type II topoisomerases and those against human topoisomerase II. Sitafloxacin showed the most potent inhibitory activities against bacterial type II topoisomerases and the lowest activity against human type II topoisomerase.
Recombinant Expression and Characterization of the Major β-Lactamase of
Mycobacterium tuberculosis
Authors: Voladri Rama Kishan R. , Lakey David L. , Hennigan Steven H. , Menzies Barbara E. , Edwards Kathryn M. , Kernodle Douglas S. 
Published: October 2018

ABSTRACT

New antibiotic regimens are needed for the treatment of multidrug-resistant tuberculosis.
Mycobacterium tuberculosis
has a thick peptidoglycan layer, and the penicillin-binding proteins involved in its biosynthesis are inhibited by clinically relevant concentrations of β-lactam antibiotics. β-Lactamase production appears to be the major mechanism by which
M. tuberculosis
expresses β-lactam resistance. β-Lactamases from the broth supernatant of 3- to 4-week-old cultures of
M. tuberculosis
H37Ra were partially purified by sequential gel filtration chromatography and chromatofocusing. Three peaks of β-lactamase activity with pI values of 5.1, 4.9, and 4.5, respectively, and which accounted for 10, 78, and 12% of the total postchromatofocusing β-lactamase activity, respectively, were identified. The β-lactamases with pI values of 5.1 and 4.9 were kinetically indistinguishable and exhibited predominant penicillinase activity. In contrast, the β-lactamase with a pI value of 4.5 showed relatively greater cephalosporinase activity. An open reading frame in cosmid Y49 of the DNA library of
M. tuberculosis
H37Rv with homology to known class A β-lactamases was amplified from chromosomal DNA of
M. tuberculosis
H37Ra by PCR and was overexpressed in
Escherichia coli
. The recombinant enzyme was kinetically similar to the pI 5.1 and 4.9 enzymes purified directly from
M. tuberculosis
. It exhibited predominant penicillinase activity and was especially active against azlocillin. It was inhibited by clavulanic acid and
m
-aminophenylboronic acid but not by EDTA. We conclude that the major β-lactamase of
M. tuberculosis
is a class A β-lactamase with predominant penicillinase activity. A second, minor β-lactamase with relatively greater cephalosporinase activity is also present.
Evaluation of Endpoints for Antifungal Susceptibility Determinations with LY303366
Authors: Klepser Michael E. , Ernst Erika J. , Ernst Michael E. , Messer Shawn A. , Pfaller Michael A. 
Published: October 2018

ABSTRACT

We have previously reported poor correlation between the in vitro fungicidal activity of LY303366 and MIC results in RPMI medium based upon the manufacturer’s suggested susceptibility endpoint, lack of visual growth. Additionally, we have noted a significant trailing effect with LY303366 when MICs are determined in RPMI medium. These observations have led us to evaluate an alternative susceptibility endpoint for LY303366, an 80% reduction in growth compared with control (similar to that utilized for azoles). Two isolates each of
Candida albicans
,
Candida glabrata
, and
Candida tropicalis
were selected for testing. MICs were determined for LY303366 in RPMI 1640 medium buffered with morpholinepropanesulfonic acid. MICs were determined with suggested (MIC
100
) and experimental (MIC
80
) endpoints. The minimal fungicidal concentration (MFC) of LY303366 for each isolate was also determined. Time-kill curves were determined in RPMI medium with each isolate at concentrations of LY303366 ranging from 0.125 to 16× MIC
80
to assess the correlation between MIC
80
and fungicidal activity. Lastly, fungi exposed to LY303366 were examined via scanning electron microscope (SEM) for evidence of drug-induced ultrastructure change. MIC
80
s for test isolates ranged from 0.015 to 0.12 μg/ml and were consistently three to five wells less than MIC
100
s. Good correlation was observed between fungicidal activity, as assessed by kill curves, and the MIC
80
. SEM data revealed significant ultrastructure changes induced by LY303366 even at sub-MIC
80
s. Based on our results demonstrating better correlation between MIC
80
and fungicidal activity, i.e., time-kill curves and MFCs, we suggest that 80% reduction in visible growth be utilized as the endpoint for susceptibility determinations with LY303366 in RPMI medium.