bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular and Biochemical Characterization of VEB-1, a Novel Class A Extended-Spectrum β-Lactamase Encoded by an
Escherichia coli
Integron Gene
Authors: Poirel Laurent , Naas Thierry , Guibert Michele , Chaibi El Bachir , Labia Roger , Nordmann Patrice 
Published: October 2018

ABSTRACT

A clinical isolate,
Escherichia coli
MG-1, isolated from a 4-month-old Vietnamese orphan child, produced a β-lactamase conferring resistance to extended-spectrum cephalosporins and aztreonam. In a disk diffusion test, a typical synergistic effect between ceftazidime or aztreonam and clavulanic acid was observed along with an unusual synergy between cefoxitin and cefuroxime. The gene for VEB-1 (Vietnamese extended-spectrum β-lactamase) was cloned and expressed in
E. coli
JM109. The recombinant plasmid pRLT1 produced a β-lactamase with a pI of 5.35 and conferred high-level resistance to extended-spectrum (or oxyimino) cephalosporins and to aztreonam.
V
max
values for extended-spectrum cephalosporins were uncommonly high, while the affinity of the enzyme for ceftazidime and aztreonam was relatively low.
bla
VEB-1
showed significant homology at the DNA level with only
bla
PER-1
and
bla
PER-2
. Analysis of the deduced protein sequence showed that VEB-1 is a class A penicillinase having very low levels of homology with any other known β-lactamases. The highest percentage of amino acid identity was 38% with PER-1 or PER-2, two uncommon class A extended-spectrum enzymes. Exploration of the genetic environment of
bla
VEB-1
revealed the presence of gene cassette features, i.e., (i) a 59-base element associated with
bla
VEB-1
; (ii) a second 59-base element just upstream of
bla
VEB-1
, likely belonging to the
aacA1-orfG
gene cassette; (iii) two core sites (GTTRRRY) on both sides of
bla
VEB-1
; and (iv) a second antibiotic resistance gene 3′ of
bla
VEB-1
,
aadB. bla
VEB-1
may therefore be the first class A extended-spectrum β-lactamase that is part of a gene cassette, which itself is likely to be located on a class 1 integron, as sulfamide resistance may indicate. Furthermore,
bla
VEB-1
is encoded on a large (>100-kb) transferable plasmid found in a
Klebsiella pneumoniae
MG-2 isolated at the same time from the same patient, indicating a horizontal gene transfer.
8-Aminoquinolines Active against Blood Stage
Plasmodium falciparum
In Vitro Inhibit Hematin Polymerization
Authors: Vennerstrom Jonathan L. , Nuzum Edwin O. , Miller Robert E. , Dorn Arnulf , Gerena Lucia , Dande Prasad A. , Ellis William Y. , Ridley Robert G. , Milhous Wilbur K. 
Published: October 2018

ABSTRACT

From the Walter Reed Army Institute of Research (WRAIR) inventory, thirteen 8-aminoquinoline analogs of primaquine were selected for screening against a panel of seven
Plasmodium falciparum
clones and isolates. Six of the 13 8-aminoquinolines had average 50% inhibitory concentrations between 50 and 100 nM against these
P. falciparum
clones and were thus an order of magnitude more potent than primaquine. However, excluding chloroquine-resistant clones and isolates, these 8-aminoquinolines were all an order of magnitude less potent than chloroquine. None of the 8-aminoquinolines was cross resistant with either chloroquine or mefloquine. In contrast to the inactive primaquine prototype, 8 of the 13 8-aminoquinolines inhibited hematin polymerization more efficiently than did chloroquine. Although alkoxy or aryloxy substituents at position 5 uniquely endowed these 13 8-aminoquinolines with impressive schizontocidal activity, the structural specificity of inhibition of both parasite growth and hematin polymerization was low.
Amphotericin B- and Fluconazole-Resistant
Candida
spp.,
Aspergillus fumigatus
, and Other Newly Emerging Pathogenic Fungi Are Susceptible to Basic Antifungal Peptides
Authors: Helmerhorst Eva J. , Reijnders Ingrid M. , van ’t Hof Wim , Simoons-Smit Ina , Veerman Enno C. I. , Amerongen Arie V. Nieuw 
Published: October 2018

ABSTRACT

The present study shows that a number of basic antifungal peptides, including human salivary histatin 5, a designed histatin analog designated dhvar4, and a peptide from frog skin, PGLa, are active against amphotericin B-resistant
Candida albicans
,
Candida krusei
, and
Aspergillus fumigatus
strains and against a fluconazole-resistant
Candida glabrata
isolate.
Pharmacodynamics of Vancomycin for the Treatment of Experimental Penicillin- and Cephalosporin-Resistant Pneumococcal Meningitis
Authors: Ahmed Amina , Jafri Hasan , Lutsar Irja , McCoig Cynthia C. , Trujillo Monica , Wubbel Loretta , Shelton Sharon , McCracken George H. 
Published: October 2018

ABSTRACT

With the emergence of β-lactam antibiotic resistance among strains of
Streptococcus pneumoniae
, vancomycin has assumed an important role in the treatment of bacterial meningitis. Using the rabbit meningitis model, we evaluated the pharmacokinetics and pharmacodynamics of vancomycin in this setting. Animals were given 80 mg/kg of body weight daily in two or four divided doses to determine the penetration and activity of vancomycin in cerebrospinal fluid (CSF); each regimen was administered with and without dexamethasone. Mean peak (2 h) concentrations in CSF that were four- to eightfold higher than the minimum bactericidal concentration (MBC; 0.5 μg/ml) for the pathogen were adequate for bacterial clearance. In both groups concentrations in CSF remained higher than the MBC for greater than 80% of the respective dosing intervals, and the penetration of vancomycin into CSF was 20%. Mean concentrations in CSF at 24 to 36 h of therapy were lower than those achieved during the first 12 h, consistent with a decline in the level of antibiotic entry into CSF as inflammation wanes. Rates of bacterial clearance were similar for the two regimens, and for all animals cultures of CSF were sterile by 36 h. The coadministration of dexamethasone significantly reduced the penetration of vancomycin into CSF by 29% and significantly lowered the rate of bacterial clearance during the first 6 h in animals receiving 20-mg/kg doses of vancomycin. For animals receiving 40-mg/kg doses, therapeutic peak concentrations in CSF were obtained even with steroid use, suggesting that the effect of steroids may be circumvented by the use of larger daily doses of vancomycin.
Antimycobacterial Activities of Isoxyl and New Derivatives through the Inhibition of Mycolic Acid Synthesis
Authors: Phetsuksiri Benjawan , Baulard Alain R. , Cooper Andrea M. , Minnikin David E. , Douglas James D. , Besra Gurdyal S. , Brennan Patrick J. 
Published: October 2018

ABSTRACT

Isoxyl (ISO), a thiourea (thiocarlide; 4,4′-diisoamyloxythiocarbanilide), demonstrated potent activity against
Mycobacterium tuberculosis
H37Rv (MIC, 2.5 μg/ml),
Mycobacterium bovis
BCG (MIC, 0.5 μg/ml),
Mycobacterium avium
(MIC, 2.0 μg/ml), and
Mycobacterium aurum
A+ (MIC, 2.0 μg/ml), resulting in complete inhibition of mycobacteria grown on solid media. Importantly, a panel of clinical isolates of
M. tuberculosis
from different geographical areas with various drug resistance patterns were all sensitive to ISO in the range of 1 to 10 μg/ml. In a murine macrophage model, ISO exhibited bactericidal killing of viable intracellular
M. tuberculosis
in a dose-dependent manner (0.05 to 2.50 μg/ml). The selective action of ISO on mycolic acid synthesis was studied through the use of [1,2-
14
C]acetate labeling of
M. tuberculosis
H37Rv,
M. bovis
BCG, and
M. aurum
A+. At its MIC for
M. tuberculosis
, ISO inhibited the synthesis of both fatty acids and mycolic acids (α-mycolates by 91.6%, methoxymycolates by 94.3%, and ketomycolates by 91.1%); at its MIC in
M. bovis
BCG, ISO inhibited the synthesis of α-mycolates by 87.2% and that of ketomycolates by 88.5%; and the corresponding inhibitions for
M. aurum
A+ were 87.1% for α-mycolates, 87.2% for ketomycolates, and 86.5% for the wax-ester mycolates. A comparison with isoniazid (INH) and ethionamide (ETH) demonstrated marked similarity in action, i.e., inhibition of the synthesis of all kinds of mycolic acids. However, unlike INH and ETH, ISO also inhibited the synthesis of shorter-chain fatty acids. ISO showed no acute toxicity against primary macrophage cell cultures as demonstrated by diminution of redox activity. A homologous series of ISO derivatives were synthesized. Most derivatives were as effective or more effective than the parent compound in the agar proportion assay. Thus, these thioureas, like INH and ETH, specifically inhibit mycolic acid synthesis and show promise in counteracting a wide variety of drug-sensitive and -resistant strains of
M. tuberculosis
.
Formation of Azole-Resistant
Candida albicans
by Mutation of Sterol 14-Demethylase P450
Authors: Asai Kentaro , Tsuchimori Noboru , Okonogi Kenji , Perfect John R. , Gotoh Osamu , Yoshida Yuzo 
Published: October 2018

ABSTRACT

The sterol 14-demethylase P450 (CYP51) of a fluconazole-resistant isolate of
Candida albicans
, DUMC136, showed reduced susceptibility to this azole but with little change in its catalytic activity. Twelve nucleotide substitutions, resulting in four amino acid changes, were identified in the DUMC136
CYP51
gene in comparison with a reported
CYP51
sequence from a wild-type, fluconazole-susceptible
C. albicans
strain. Seven of these substitutions, including all of those causing amino acid changes, were located within a region covering one of the putative substrate recognition sites of the enzyme (SRS-1). Polymorphisms within this region were observed in several
C. albicans
isolates, and some were found to be
CYP51
heterozygotes. Among the amino acid changes occurring in this region, only an alteration of Y132 was common among these fluconazole-resistant isolates, which suggests the importance of this residue to the fluconazole resistance of the target enzyme. DUMC136 and another fluconazole-resistant isolate were homozygotes with respect to
CYP51
, although the typical wild-type, fluconazole-susceptible
C. albicans
was a
CYP51
heterozygote. These findings suggest that part of the fluconazole-resistant phenotype of
C. albicans
DUMC136 was acquired through a mutation-prone area of
CYP51
, an area which might promote the formation of fluconazole-resistant CYP51, along with a mechanism(s) which allows the formation of a homozygote of this altered CYP51 in this diploid pathogenic yeast.
Safety and Pharmacokinetics of an Intramuscular Monoclonal Antibody (SB 209763) against Respiratory Syncytial Virus (RSV) in Infants and Young Children at Risk for Severe RSV Disease
Authors: Meissner H. Cody , Groothuis Jessie R. , Rodriguez William J. , Welliver Robert C. , Hogg Geoff , Gray Peter H. , Loh Richard , Simoes Eric A. F. , Sly Peter , Miller Ann K. , Nichols Alice I. , Jorkasky Diane K. , Everitt Daniel E. , Thompson Kathleen A. 
Published: October 2018

ABSTRACT

We conducted a multicenter, double-blind, placebo-controlled, randomized trial of a humanized monoclonal antibody against a respiratory syncytial virus (RSV) fusion protein (SB 209763) to evaluate its safety, pharmacokinetics, and fusion inhibition and neutralization titers. Forty-three infants who were either delivered prematurely (≤35 weeks’ gestation) or exhibited bronchopulmonary dysplasia were administered either single or repeat (two doses, 8 weeks apart) intramuscular injections of SB 209763 at a concentration of 0.25, 1.25, 5.0, or 10.0 mg/kg or of a placebo. Four of 229 adverse events were considered related to the study drug, including purpura (
n
= 3) and thrombocytosis (
n
= 1). No subject developed a detectable level of anti-SB 209763 antibody. Approximately 1 week after administration of the second dose of SB 209763 at 10 mg/kg, the mean plasma concentration (
n
= 9) was 68.5 μg/ml. The terminal half-life (
T
1/2
) determined by noncompartmental analysis ranged from 22 to 50 days. The population pharmacokinetics for SB 209763 following intramuscular administration was appropriately described by a one-compartment model with first-order input and elimination. Higher values for clearance and volume of distribution at steady state were observed for younger patients, with values decreasing to 0.143 (ml/h)/kg and 161 mL/kg, respectively, by a mean age of 298 days (∼10 months). The mean
T
1/2
of SB 209763 for the study population was 32.5 days. No other factor (dose, weight, gender, race, premature birth, or bronchopulmonary dysplasia) was observed to alter the population pharmacokinetics of SB 209763 in this study of infants and young children. The mean neutralization titer on day 6 was 286, and the mean fusion inhibition titer was 36. At least 57% of subjects dosed at 1.25 to 10.0 mg of SB 209763 per kg of body weight who were seronegative at baseline experienced a fourfold or greater increase in fusion inhibition titer. Nine RSV infections were documented during the 16-week course of the study; the numbers of RSV infections were similar for the different regimens, including the placebo. The doses of SB 209763 studied may have been insufficient to confer protection against RSV lower respiratory tract disease; these results suggest that additional trials using higher doses of monoclonal antibody for immunoprophylaxis should be considered.
Outer Membrane Permeability Barrier in
Escherichia coli
Mutants That Are Defective in the Late Acyltransferases of Lipid A Biosynthesis
Authors: Vaara Martti , Nurminen Marjatta 
Published: October 2018

ABSTRACT

The tight packing of six fatty acids in the lipid A constituent of lipopolysaccharide (LPS) has been proposed to contribute to the unusually low permeability of the outer membrane of gram-negative enteric bacteria to hydrophobic antibiotics. Here it is shown that the
Escherichia coli msbB
mutant, which elaborates defective, penta-acylated lipid A, is practically as resistant to a representative set of hydrophobic solutes (rifampin, fusidic acid, erythromycin, clindamycin, and azithromycin) as the parent-type control strain. The susceptibility index, i.e., the approximate ratio between the MIC for the
msbB
mutant and that for the parent-type control, was maximally 2.7-fold. In comparison, the
rfa
mutant defective in the deep core oligosaccharide part of LPS displayed indices ranging from 20 to 64. The
lpxA
and
lpxD
lipid A mutants had indices higher than 512. Furthermore, the
msbB
mutant was resistant to glycopeptides (vancomycin, teicoplanin), whereas the
rfa
,
lpxA
, and
lpxD
mutants were susceptible. The
msbB htrB
double mutant, which elaborates even-more-defective, partially tetra-acylated lipid A, was still less susceptible than the
rfa
mutant. These findings indicate that hexa-acylated lipid A is not a prerequisite for the normal function of the outer membrane permeability barrier.
Activity of Moxifloxacin, Administered Once a Day, against
Streptococcus pneumoniae
in an In Vitro Pharmacodynamic Model of Infection
Authors: MacGowan Alasdair P. , Bowker Karen E. , Wootton Mandy , Holt H. Alan 
Published: October 2018

ABSTRACT

The antibacterial effect of moxifloxacin was studied by using an in vitro pharmacodynamic model of infection with dosing simulations of 400 mg every 24 h for 48 h.
Streptococcus pneumoniae
was tested by using four wild-type strains for which the moxifloxacin MICs were 0.008, 0.12, 0.14, and 3.6 mg/liter. In addition, two isogenic mutants, generated from the strains for which the moxifloxacin MICs were ≤0.12 mg/liter and for which the MICs were 1.0 and 1.6 mg/liter, were also used. Antibacterial efficacy was measured by the following indices: log change in viable count at 12, 24, 36, and 48 h; area under the bacterial kill curve (AUBKC); and time to kill 99.9% of the initial inoculum. With the three strains for which the moxifloxacin MICs were ≤0.14 mg/liter, there was a marked reduction in viable count over 12 to 36 h; in contrast, with strains for which the MICs were ≥1.0 mg/liter, little killing occurred over 48 h. A sigmoid dose-response model indicated that the area under the curve/MIC ratio was strongly related to the log change in viable count at 24 and 48 h and to the AUBKC. These data indicate that moxifloxacin may have a role in management of
S. pneumoniae
infection.
Safety and Pharmacokinetics of Amprenavir (141W94), a Human Immunodeficiency Virus (HIV) Type 1 Protease Inhibitor, following Oral Administration of Single Doses to HIV-Infected Adults
Authors: Sadler Brian M. , Hanson Cynthia D. , Chittick Gregory E. , Symonds William T. , Roskell Neil S. 
Published: October 2018

ABSTRACT

We conducted a double-blind, placebo-controlled, parallel, dose-escalation trial to evaluate the pharmacokinetics and safety of single, oral doses of amprenavir (141W94; formerly VX-478), a potent inhibitor of human immunodeficiency virus (HIV) type 1 protease, administered as hard gelatin capsules in 12 HIV-infected subjects. The doses of amprenavir evaluated were 150, 300, 600, 900, and 1,200 mg. Amprenavir was rapidly absorbed, with the time to maximum concentration occurring within 1 to 2 h after dosing. On the basis of power model analysis, the increase in the maximum concentration of amprenavir in plasma (
C
max
) was less than dose proportional, and the increase in the area under the concentration-time curve from time zero to infinity (AUC
0–∞
) was greater than dose proportional; mean slopes (with 90% confidence intervals) were 1.25 (1.16 to 1.35) and 0.78 (0.78 to 0.86) for AUC
0–∞
and
C
max
, respectively. Amprenavir was eliminated slowly, with a terminal-phase half-life of 8 h. A second study was conducted to determine the bioavailability of the hard gelatin capsule relative to that of a subsequently developed soft gelatin capsule. The capsules were bioequivalent in terms of AUC
0–∞
but not in terms of
C
max
; geometric-least-squares means ratios (with 90% confidence intervals) were 1.03 (0.92 to 1.14) and 1.25 (1.03 to 1.53) for AUC
0–∞
and
C
max
, respectively. Administration of soft gelatin capsules of amprenavir with a high-fat breakfast resulted in a 14% decrease in the mean AUC
0–∞
(from 9.58 to 8.26 μg · h/ml), which is not likely to be clinically significant. The most common adverse events related to amprenavir were headache, nausea, and hypesthesia. Amprenavir appears to be safe and well tolerated over the dose range of 150 to 1200 mg. On the basis of the present single-dose studies, amprenavir is an HIV protease inhibitor with favorable absorption and clearance pharmacokinetics that are only minimally affected by administration with food.
Use of the Hepatitis B Virus Recombinant Baculovirus-HepG2 System to Study the Effects of (−)-β-2′,3′-Dideoxy-3′-Thiacytidine on Replication of Hepatitis B Virus and Accumulation of Covalently Closed Circular DNA
Authors: Delaney William E. , Miller Thomas G. , Isom Harriet C. 
Published: October 2018

ABSTRACT
(−)-β-2′,3′-Dideoxy-3′-thiacytidine (lamivudine [3TC]) is a nucleoside analog which effectively interferes with the replication of hepatitis B virus (HBV) DNA in vitro and in vivo. We have investigated the antiviral properties of 3TC in vitro in HepG2 cells infected with recombinant HBV baculovirus. Different types of information can be obtained with the HBV baculovirus-HepG2 system because (i) experiments can be carried out at various levels of HBV replication including levels significantly higher than those that can be obtained from conventional HBV-expressing cell lines, (ii) cultures can be manipulated and/or treated prior to or during the initiation of HBV expression, and (iii) high levels of HBV replication allow the rapid detection of HBV products including covalently closed circular (CCC) HBV DNA from low numbers of HepG2 cells. The treatment of HBV baculovirus-infected HepG2 cells with 3TC resulted in an inhibition of HBV replication, evidenced by reductions in the levels of both extracellular HBV DNA and intracellular replicative intermediates. The effect of 3TC on HBV replication was both dose and time dependent, and the reductions in extracellular HBV DNA that we observed agreed well with the previously reported efficacy of 3TC in vitro. As expected, levels of HBV transcripts and extracellular hepatitis B surface antigen and e antigen were not affected by 3TC. Importantly, the HBV baculovirus-HepG2 system made it possible to observe for the first time that CCC HBV DNA levels are lower in cells treated with 3TC than in control cells. We also observed that the treatment of HepG2 cells prior to HBV baculovirus infection resulted in a slight increase in the efficacy of 3TC compared to treatments starting 24 h postinfection. The treatment of HepG2 cells with the highest concentration of 3TC tested in this study (2 μM) prior to the initiation of HBV replication markedly inhibited the accumulation of CCC DNA, whereas treatment with the same concentration of 3TC at a time when CCC HBV DNA pools were established within the cells was considerably less effective. In addition, our results suggest that in HepG2 cells, non-protein-associated relaxed circular HBV DNA and particularly CCC HBV DNA are considerably more resistant to 3TC treatment than other forms of HBV DNA, including replicative intermediates and extracellular DNA. We conclude from these studies that the HBV baculovirus-HepG2 system has specific advantages for drug studies and can be used to complement other in vitro model systems currently used for testing antiviral compounds.
Antitrypanosomal Activity of Fluoroquinolones
Authors: Nenortas Elizabeth , Burri Christian , Shapiro Theresa A. 
Published: October 2018

ABSTRACT

Six fluoroquinolones presently in clinical use and four investigational tetracyclic fluoroquinolones were tested for in vitro activity against bloodstream-form
Trypanosoma brucei brucei
. All compounds had measurable activity, but the tetracyclic analogs were most potent, with 50% effective concentrations in the low micromolar range. In general, trypanosomes were more susceptible than L1210 leukemia cells. Consistent with the notion that they target type II topoisomerase in trypanosomes, the fluoroquinolones promote the formation of protein-DNA covalent complexes.
Effects of Enrofloxacin on Porcine Phagocytic Function
Authors: Schoevers E. J. , van Leengoed L. A. M. G. , Verheijden J. H. M. , Niewold T. A. 
Published: October 2018

ABSTRACT

The interaction between enrofloxacin and porcine phagocytes was studied with clinically relevant concentrations of enrofloxacin. Enrofloxacin accumulated in phagocytes, with cellular concentration/extracellular concentration ratios of 9 for polymorphonuclear leukocytes (PMNs) and 5 for alveolar macrophages (AMs). Cells with accumulated enrofloxacin brought into enrofloxacin-free medium released approximately 80% (AMs) to 90% (PMNs) of their enrofloxacin within the first 10 min, after which no further release was seen. Enrofloxacin affected neither the viability of PMNs and AMs nor the chemotaxis of PMNs at concentrations ranging from 0 to 10 μg/ml. Enrofloxacin (0.5 μg/ml) did not alter the capability of PMNs and AMs to phagocytize fluorescent microparticles or
Actinobacillus pleuropneumoniae
,
Pasteurella multocida
, and
Staphylococcus aureus
. Significant differences in intracellular killing were seen with enrofloxacin at 5× the MIC compared with that for controls not treated with enrofloxacin. PMNs killed all
S. aureus
isolates in 3 h with or without enrofloxacin. Intracellular
S. aureus
isolates in AMs were less susceptible than extracellular
S. aureus
isolates to the bactericidal effect of enrofloxacin.
P. multocida
was not phagocytosed by PMNs. AMs did not kill
P. multocida
, and similar intra- and extracellular reductions of
P. multocida
isolates by enrofloxacin were found. Intraphagocytic killing of
A. pleuropneumoniae
was significantly enhanced by enrofloxacin at 5× the MIC in both PMNs and AMs. AMs are very susceptible to the
A. pleuropneumoniae
cytotoxin. This suggests that in serologically naive pigs the enhancing effect of enrofloxacin on the bactericidal action of PMNs may have clinical relevance.