bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthetic Peptides That Exert Antimicrobial Activities in Whole Blood and Blood-Derived Matrices
Authors: Yeaman Michael R. , Gank Kimberly D. , Bayer Arnold S. , Brass Eric P. 
Published: November 2002

ABSTRACTPeptides that exert antimicrobial activity in artificial media may lack activity within blood or other complex biological matrices. To facilitate the evaluation of antimicrobial peptides for possible therapeutic utility, an ex vivo assay was developed to assess the extent and durability of peptide antimicrobial activities in complex fluid biomatrices of whole blood, plasma, and serum compared with those in conventional media. Novel antimicrobial peptides (RP-1 and RP-11) were designed based in part on platelet microbicidal proteins. RP-1, RP-11, or gentamicin was introduced into biomatrices either coincident with, or 2 h prior to, inoculation with anEscherichia colitarget organism. Antimicrobial activities of peptides were assessed by quantitative culture 2 h after bacterial inoculation and compared to those of peptide-free and gentamicin controls. In whole blood and homologous plasma or serum, introduction of RP-1 or RP-11 coincident withE. coliwas associated with a significant reduction in CFU per milliliter versus the respective peptide-free controls. Moreover, substantial antimicrobial activity remained when RP-1 or RP-11 was placed into whole blood or plasma 2 h prior toE. coliinoculation. These results suggest that the peptides were not rapidly inactivated within these biomatrices. Peptide antimicrobial activities were negatively affected by preincubation in serum or in heat-inactivated serum, compared with those of the respective controls. Peptides RP-1 and RP-11 were consistently effective at lower concentrations in biomatrices than in artificial media, indicating favorable antimicrobial interactions with components of blood or blood fractions. Collectively, these findings support the concept that synthetic peptides can be designed to exert potent antimicrobial activities in relevant and complex biological matrices.
Analysis of an 8.1-kb DNA Fragment Contiguous with the Erythromycin Gene Cluster of
Saccharopolyspora erythraea
in the
eryCI
-Flanking Region
Authors: Reeves Andrew R. , Weber Gerhard , Cernota William H. , Weber J. Mark 
Published: November 2002

ABSTRACT

An 8.1-kb region of the
Saccharopolyspora erythraea
genome, significant for its contiguity to the known genes of the erythromycin biosynthetic gene cluster, was mutationally analyzed and its DNA sequence was determined. The region lies immediately adjacent to
eryCI
. The newly characterized region is notable for a large, 3.0-kb segment, predicted not to be translated, followed by four probable genes: an acetyltransferase gene, a protease inhibitor gene, a methyltransferase gene, and a transposase gene. Because the probable functions of the genes in this region are not required for erythromycin biosynthesis or resistance and because a deletion of a 6.0-kb portion of this region had no effect on erythromycin biosynthesis, this region marks the outside boundary of the erythromycin gene cluster. Therefore,
eryCI
represents the end of the cluster. These results complete the analysis of the erythromycin gene cluster and eliminate the possibility that additional sought-after pathway-specific structural or regulatory genes might be found within or adjacent to the cluster.
ABC Transporters and Azole Susceptibility in Laboratory Strains of the Wheat Pathogen
Mycosphaerella graminicola
Authors: Zwiers Lute-Harm , Stergiopoulos Ioannis , Van Nistelrooy Johannes G. M. , De Waard Maarten A. 
Published: November 2002

ABSTRACT

Laboratory strains of
Mycosphaerella graminicola
with decreased susceptibilities to the azole antifungal agent cyproconazole showed a multidrug resistance phenotype by exhibiting cross-resistance to an unrelated chemical, cycloheximide or rhodamine 6G, or both. Decreased azole susceptibility was found to be associated with either decreased or increased levels of accumulation of cyproconazole. No specific relationship could be observed between azole susceptibility and the expression of ATP-binding cassette (ABC) transporter genes
MgAtr1
to
MgAtr5
and the sterol P450 14α-demethylase gene,
CYP51
. ABC transporter MgAtr1 was identified as a determinant in azole susceptibility since heterologous expression of the protein reduced the azole susceptibility of
Saccharomyces cerevisiae
and disruption of
MgAtr1
in one specific
M. graminicola
laboratory strain with constitutive
MgAtr1
overexpression restored the level of susceptibility to cyproconazole to wild-type levels. However, the level of accumulation in the mutant with an
MgAtr1
disruption did not revert to the wild-type level. We propose that variations in azole susceptibility in laboratory strains of
M. graminicola
are mediated by multiple mechanisms.
Virtual Inhibitory Quotient Predicts Response to Ritonavir Boosting of Indinavir-Based Therapy in Human Immunodeficiency Virus-Infected Patients with Ongoing Viremia
Authors: Shulman Nancy , Zolopa Andrew , Havlir Diane , Hsu Ann , Renz Cheryl , Boller Sheila , Jiang Ping , Rode Richard , Gallant Joel , Race Elizabeth , Kempf Dale J. , Sun Eugene 
Published: November 2002

ABSTRACTDepending on the degree of underlying resistance present, optimization of the pharmacokinetics of protease inhibitors may result in improved virologic suppression. Thirty-seven human immunodeficiency virus (HIV)-infected subjects who had chronic detectable viremia and who were receiving 800 mg of indinavir three times a day (TID) were switched to 400 mg of indinavir BID with 400 mg of ritonavir two times a day (BID) for 48 weeks. Full pharmacokinetic evaluations were obtained for 12 subjects before the switch and 3 weeks after the switch. Combination therapy increased the indinavir predose concentrations in plasma by 6.47-fold, increased the minimum concentration in serum by 3.41-fold, and reduced the maximum concentration in serum by 57% without significantly changing the area under the plasma concentration-time curve at 24 h. At week 3, 58% (21 of 36) of the subjects for whom postbaseline measurements were available achieved a viral load in plasma of <50 copies/ml or a reduction from the baseline load of ≥0.5 log10copies/ml. Of these subjects, 82% (14 of 17) whose viruses had three or fewer protease inhibitor mutations and 88% (14 of 16) whose viruses had an indinavir virtual phenotypic susceptibility test of more than sixfold less than that for the baseline isolate were considered virologic responders. The indinavir virtual inhibitory quotient, which is a function of baseline indinavir phenotypic resistance (estimated by virtual phenotype) and the indinavir predose concentration in plasma achieved with indinavir-ritonavir combination therapy, was the best predictor of a viral load reduction. Sixteen subjects discontinued the study by week 48 due to adverse events, predominantly related to hyperlipidemia. Pharmacokinetic intensification of indinavir-based therapy with ritonavir reduced the viral loads in subjects but added toxicity. The virtual inhibitory quotient, which incorporates both baseline viral resistance and the level of drug exposure in plasma, was superior to either baseline resistance or drug exposure alone in predicting the virologic response.
Inactivation of Human Immunodeficiency Virus Type 1 by Porphyrins
Authors: Vzorov Andrei N. , Dixon Dabney W. , Trommel Jenna S. , Marzilli Luigi G. , Compans Richard W. 
Published: November 2002

ABSTRACT

We have evaluated the anti-human immunodeficiency virus (HIV) activity of a series of natural and synthetic porphyrins to identify compounds that could potentially be used as microbicides to provide a defense against infection by sexually transmitted virus. For assays we used an epithelial HeLa-CD4 cell line with an integrated long terminal repeat-β-galactosidase gene. For structure-activity analysis, we divided the porphyrins tested into three classes: (i) natural porphyrins, (ii) metallo-tetraphenylporphyrin tetrasulfonate (metallo-TPPS4) derivatives, and (iii) sulfonated tetra-arylporphyrin derivatives. None of the natural porphyrins studied reduced infection by more than 80% at a concentration of 5 μg/ml in these assays. Some metal chelates of TPPS4 were more active, and a number of sulfonated tetra-aryl derivatives showed significantly higher activity. Some of the most active compounds were the sulfonated tetranaphthyl porphyrin (TNapPS), sulfonated tetra-anthracenyl porphyrin (TAnthPS), and sulfonated 2,6-difluoro-
meso
-tetraphenylporphine [TPP(2,6-F2)S] and its copper chelate [TPP(2,6-F2)S,Cu], which reduced infection by 99, 96, 94, and 96%, respectively. Our observations indicate that at least some of these compounds are virucidal, i.e., that they render the virus noninfectious. The active compounds were found to inhibit binding of the HIV type 1 gp120 to CD4 and also to completely inhibit the ability of Env proteins expressed from recombinant vectors to induce cell fusion with receptor-bearing target cells. These results support the conclusion that modified porphyrins exhibit substantial activity against HIV and that their target is the HIV Env protein.
Energy-Dependent Accumulation of Norfloxacin and Porin Expression in Clinical Isolates of
Klebsiella pneumoniae
and Relationship to Extended-Spectrum β-Lactamase Production
Authors: Martínez-Martínez Luis , Pascual Alvaro , Conejo María del Carmen , García Isabel , Joyanes Providencia , Doménech-Sánchez Antonio , Benedí Vicente Javier 
Published: November 2002

ABSTRACT

The relationships between porin deficiency, active efflux of fluoroquinolones, and extended-spectrum β-lactamase (ESBL) production were determined for 53 clinical isolates of
Klebsiella pneumoniae
. Thirty-two ESBL-positive strains (including 22 strains expressing porins and 10 strains lacking porins) and 21 ESBL-negative strains were evaluated. Active efflux of norfloxacin was defined as a ≥50% increase in the accumulation of norfloxacin in the presence of carbonyl cyanide
m
-chlorophenylhydrazone (CCCP) in comparison with the corresponding basal value in the absence of CCCP. The quinolone resistance-determining regions of both
gyrA
and
parC
from 13 strains, representing all isolates with different porin profiles and with or without active efflux, were determined. Porin loss was significantly more common among ESBL-positive strains (10 of 32 [31.2%]) than among ESBL-negative strains (0 of 2 [0%]) (
P
< 0.01). Active efflux was observed in 7 of 10 (70%) strains lacking porins and in 4 of 43 (9.3%) strains producing porins (
P
< 0.001). The 11 strains showing active efflux corresponded to 3 of 21 (14.3%) ESBL-negative strains and 8 of 32 (25.5%) ESBL-positive strains (
P
> 0.05). Basal values of norfloxacin accumulation were higher in strains lacking active efflux than in those that had this mechanism (
P
< 0.05). In the absence of topoisomerase changes, the contribution of either porin loss or active efflux to fluoroquinolone resistance in
K. pneumoniae
was negligible. It is concluded that among
K. pneumoniae
strains of clinical origin, porin loss was observed only in those producing ESBL, and that a significant number of porin-deficient strains also expressed active efflux of norfloxacin. In terms of fluoroquinolone resistance, both mechanisms are significant only in the presence of topoisomerase modifications.
Intramuscular Bioavailability and Clinical Efficacy of Artesunate in Gabonese Children with Severe Malaria
Authors: Nealon Claire , Dzeing Arnaud , Müller-Römer Ulrich , Planche Timothy , Sinou Veronique , Kombila Maryvonne , Kremsner Peter G. , Parzy Daniel , Krishna Sanjeev 
Published: November 2002

ABSTRACT
Artesunate (ARS) is a water-soluble artemisinin derivative that is a potential alternative to quinine for the treatment of severe childhood malaria. We studied the pharmacokinetics and bioavailability of ARS given by the intramuscular (i.m.) route in an open crossover study design. Fourteen children were randomized to receive intravenous (i.v.) ARS in a loading dose (2.4 mg/kg of body weight) followed 12 h later by an i.m. dose (1.2 mg/kg) (group I), and 14 children were randomized to receive i.m. ARS (2.4 mg/kg) followed by an i.v. dose of ARS (1.2 mg/kg) (group II). We carried out a two-compartment analysis of ARS and dihydroartemisinin (DHA; the principal antimalarial metabolite) levels in 21 children (groups I and II combined). Absorption of i.m. ARS was rapid, with the maximum concentration of DHA in serum being achieved in less than 1 h in most children (median time to the maximum concentration of drug in serum, 35.1 min; range, 10.8 to 71.9 min). The absolute bioavailability of DHA was a median of 86.4% (range, 11.4 to 462.1%), the median steady-state volume of distribution was 1.3 liters/kg (range, 0.5 to 7.9 liters/kg), and the median clearance was 0.028 liters/kg/min (range, 0.001 to 1.58 liters/kg/min). There were no major adverse events attributable to ARS. Parasite clearance kinetics were comparable between the two treatment groups. These results support the use of i.m. ARS in children with severe malaria.
Emergence of Tetracycline Resistance in
Helicobacter pylori
: Multiple Mutational Changes in 16S Ribosomal DNA and Other Genetic Loci
Authors: Dailidiene Daiva , Bertoli M. Teresita , Miciuleviciene Jolanta , Mukhopadhyay Asish K. , Dailide Giedrius , Pascasio Mario Alberto , Kupcinskas Limas , Berg Douglas E. 
Published: November 2002

ABSTRACT

Tetracycline is useful in combination therapies against the gastric pathogen
Helicobacter pylori
. We found 6 tetracycline-resistant (Tet
r
) strains among 159 clinical isolates (from El Salvador, Lithuania, and India) and obtained the following four results: (i) 5 of 6 Tet
r
isolates contained one or two nucleotide substitutions in one part of the primary tetracycline binding site in 16S rRNA (AGA
965-967
[
Escherichia coli
coordinates] changed to gGA, AGc, guA, or gGc [lowercase letters are used to represent the base changes]), whereas the sixth (isolate Ind75) retained AGA
965-967
; (ii) PCR products containing mutant 16S ribosomal DNA (rDNA) alleles transformed recipient strains to Tet
r
phenotypes, but transformants containing alleles with single substitutions (gGA and AGc) were less resistant than their Tet
r
parents; (iii) each of 10 Tet
r
mutants of reference strain 26695 (in which mutations were induced with metronidazole, a mutagenic anti-
H. pylori
agent) contained the normal AGA
965-967
sequence; and (iv) transformant derivatives of Ind75 and of one of the Tet
r
26695 mutants that had acquired mutant rDNA alleles were resistant to tetracycline at levels higher than those to which either parent strain was resistant. Thus, tetracycline resistance in
H. pylori
results from an accumulation of changes that may affect tetracycline-ribosome affinity and/or other functions (perhaps porins or efflux pumps). We suggest that the rarity of tetracycline resistance among clinical isolates reflects this need for multiple mutations and perhaps also the deleterious effects of such mutations on fitness. Formally equivalent mutations with small but additive effects are postulated to contribute importantly to traits such as host specificity and virulence and to
H. pylori
's great genetic diversity.
Therapeutic Efficacies of Artesunate-Sulfadoxine-Pyrimethamine and Chloroquine-Sulfadoxine-Pyrimethamine in Vivax Malaria Pilot Studies: Relationship to
Plasmodium vivax dhfr
Mutations
Authors: Tjitra Emiliana , Baker Joanne , Suprianto Sri , Cheng Qin , Anstey Nicholas M. 
Published: November 2002

ABSTRACT

Artemisinin-derivative combination therapies (ACT) are highly efficacious against multidrug-resistant
Plasmodium falciparum
malaria. Few efficacy data, however, are available for vivax malaria. With high rates of chloroquine (CQ) resistance in both vivax and falciparum malaria in Papua Province, Indonesia, new combination therapies are required for both species. We recently found artesunate plus sulfadoxine-pyrimethamine (ART-SP) to be highly effective (96%) in the treatment of falciparum malaria in Papua Province. Following a preliminary study of CQ plus sulfadoxine-pyrimethamine (CQ-SP) for the treatment of
Plasmodium vivax
infection, we used modified World Health Organization criteria to evaluate the efficacy of ART-SP for the treatment of vivax malaria in Papua. Nineteen of 22 patients treated with ART-SP could be evaluated on day 28, with no early treatment failures. Adequate clinical and parasitological responses were found by day 14 in all 20 (100%) of the patients able to be evaluated and by day 28 in 17 patients (89.5%). Fever and parasite clearance times were short, with hematological improvement observed in 70.6% of the patients. Double (at positions 58 and 117) and quadruple (at positions 57, 58, 61, and 117) mutations in the
P. vivax
dihydrofolate reductase (PvDHFR) were common in Papuan
P. vivax
isolates (46 and 18%, respectively). Treatment failure with SP-containing regimens was significantly higher with isolates with this PvDHFR quadruple mutation, which included a novel T→M mutation at residue 61 linked to an S→T (but not an S→N) mutation at residue 117. ART-SP ACT resulted in a high cure rate for both major
Plasmodium
species in Papua, though progression of DHFR mutations in both species due to the continued use of SP monotherapy for clinically diagnosed malaria threatens the future utility of this combination.
env
Chimeric Virus Technology for Evaluating Human Immunodeficiency Virus Susceptibility to Entry Inhibitors
Authors: Fikkert Valery , Cherepanov Peter , Van Laethem Kristel , Hantson Anke , Van Remoortel Barbara , Pannecouque Christophe , De Clercq Erik , Debyser Zeger , Vandamme Anne-Mieke , Witvrouw Myriam 
Published: November 2002

ABSTRACT

We describe the development of chimeric virus technology (CVT) for human immunodeficiency virus (HIV) type 1 (HIV-1)
env
genes
gp120
,
gp41
, and
gp160
for evaluation of the susceptibilities of HIV to entry inhibitors. This
env
CVT allows the recombination of
env
sequences derived from different strains into a proviral wild-type HIV-1 clone (clone NL4.3) from which the corresponding
env
gene has been deleted. An HIV-1 strain (strain NL4.3) resistant to the fusion inhibitor T20 (strain NL4.3/T20) was selected in vitro in the presence of T20. AMD3100-resistant strain NL3.4 (strain NL4.3/AMD3100) was previously selected by De Vreese et al. (K. De Vreese et al., J. Virol. 70:689-696, 1996). NL4.3/AMD3100 contains several mutations in its
gp120
gene (De Vreese et al., J. Virol. 70:689-696, 1996), whereas NL4.3/T20 has mutations in both
gp120
and
gp41
. Phenotypic analysis revealed that NL4.3/AMD3100 lost its susceptibility to dextran sulfate, AMD3100, AMD2763, T134, and T140 but not its susceptibility to T20, whereas NL4.3/T20 lost its susceptibility only to the inhibitory effect of T20. The recombination of
gp120
of NL4.3/AMD3100 and
gp41
of NL4.3/T20 or recombination of the
gp160
genes of both strains into a wild-type background reproduced the phenotypic (cross-)resistance profiles of the corresponding strains selected in vitro. These data imply that mutations in
gp120
alone are sufficient to reproduce the resistance profile of NL4.3/AMD3100. The same can be said for
gp41
in relation to NL4.3/T20. In conclusion, we demonstrate the use of
env
CVT as a research tool in the delineation of the region important for the phenotypic (cross-)resistance of HIV strains to entry inhibitors. In addition, we obtained a proof of principle that
env
CVT can become a helpful diagnostic tool in assessments of the phenotypic resistance of clinical HIV isolates to HIV entry inhibitors.
Evolution of Multiresistance in Nontyphoid
Salmonella
Serovars from 1984 to 1998 in Argentina
Authors: Orman Betina E. , Piñeiro Silvia A. , Arduino Sonia , Galas Marcelo , Melano Roberto , Caffer Maria I. , Sordelli Daniel O. , Centrón Daniela 
Published: November 2002

ABSTRACT

Molecular evolution of multiresistance in nontyphoid
Salmonella
spp. was investigated with 155 isolates obtained in Argentina from 1984 to 1998. In 74 isolates obtained from 1984 to 1988 resistance was associated with the presence of Tn
3
, Tn
9
, class I (In0) and II (Tn
7
) integrons, and the
aac
(
3
)
-IIa
gene. Extended-spectrum cephalosporin (ESC) resistance in
Salmonella
spp. emerged in 1989, and 81 isolates resistant to at least one ESC and one aminoglycoside were collected thereafter. Among these, two patterns of antimicrobial resistance mechanisms were found: from 1989 to 1992, resistance was related to the spreading of Tn
1331
and
bla
CTX-M-2
, in addition to the persistence of In0 and Tn
7
. From 1993 to 1998, several integrons were added to the first pattern and three integron groups (IG), namely, IG1 (38% of the isolates), IG2 (51%), and IG3 (11%), were identified. At least two β-lactamase genes were detected in 65% of the isolates (after 1989) by PCR analysis. Furthermore, five β-lactamase genes,
bla

CTX-M-

2

,
bla
OXA-9
,
bla
OXA-2
,
bla
TEM-1
, and
bla
PER-2
, were found in two isolates. The
bla
CTX-M-2
gene was found in several complex
sulI
-type integrons with different rearrays within the variable region of class I integrons, suggesting evolution of these integrons in nontyphoid
Salmonella
. In conclusion, progressive acquisition and accumulation of plasmid-mediated resistance determinants occurred from 1984 to 1998 in nontyphoid
Salmonella
isolates of the most prevalent serovars from Argentina. It is suggested that antimicrobial resistance mechanisms in these bacteria may have been the consequence of plasmid exchange between
Salmonella enterica
serovar Typhimurium and
Escherichia coli
or
Shigella flexneri
and/or spreading of mobile elements from the nosocomial environment.
Amino Acid Substitutions at Ambler Position Gly238 in the SHV-1 β-Lactamase: Exploring Sequence Requirements for Resistance to Penicillins and Cephalosporins
Authors: Hujer Andrea M. , Hujer Kristine M. , Helfand Marion S. , Anderson Vernon E. , Bonomo Robert A. 
Published: November 2002

ABSTRACT

Site saturation mutagenesis of the 238 position in the SHV β-lactamase was performed to identify the complete sequence requirements needed for the extended spectrum β-lactamase (ESBL) phenotype. MICs (in micrograms per milliliter) in an isogenic background,
Escherichia coli
DH10B, demonstrated that the Gly238Ala mutation conferred the most resistance to penicillins and cephalosporins. The absolute increase in resistance was greatest against cefotaxime for the Gly238Ala mutant (0.06 to 8 μg/ml). Except for the strain possessing the Gly238Pro β-lactamase, ceftazidime MICs were also elevated. None of the mutant SHV β-lactamases were expressed in as great an amount as the wild-type β-lactamase. Kinetic analysis of the Gly238Ala mutant revealed that penicillin and cephalosporin substrates have a lower

K
m

for the enzyme because of this mutation. Ampicillin and piperacillin MICs were inversely proportional to the side chain volume of the amino acid in cases larger than Ser, suggesting that steric considerations may be a primary requirement for penicillin resistance. Secondary structural effects explain increased resistance to oxyiminocephalosporins. Based upon this study, we anticipate that additional mutations of Gly238 in the SHV β-lactamase will continue to be discovered with an ESBL (ceftazidime or cefotaxime resistant) phenotype.
Structural Basis for Imipenem Inhibition of Class C β-Lactamases
Authors: Beadle Beth M. , Shoichet Brian K. 
Published: November 2002

ABSTRACT
To determine how imipenem inhibits the class C β-lactamase AmpC, the X-ray crystal structure of the acyl-enzyme complex was determined to a resolution of 1.80 Å. In the complex, the lactam carbonyl oxygen of imipenem has flipped by approximately 180° compared to its expected position; the electrophilic acyl center is thus displaced from the point of hydrolytic attack. This conformation resembles that of imipenem bound to the class A enzyme TEM-1 but is different from that of moxalactam bound to AmpC.