bluuebunny/crossref_metadata_2025_split huggingface dataset:
Total Variation in the
penA
Gene of
Neisseria meningitidis
: Correlation between Susceptibility to β-Lactam Antibiotics and
penA
Gene Heterogeneity
Authors: Thulin Sara , Olcén Per , Fredlund Hans , Unemo Magnus 
Published: September 2006

ABSTRACT

In recent decades, the prevalence of
Neisseria meningitidis
isolates with reduced susceptibility to penicillins has increased. The intermediate resistance to penicillin (Pen
i
) for most strains is due mainly to mosaic structures in the
penA
gene, encoding penicillin-binding protein 2. In this study, susceptibility to β-lactam antibiotics was determined for 60 Swedish clinical
N. meningitidis
isolates and 19 reference strains. The
penA
gene was sequenced and compared to 237
penA
sequences from GenBank in order to explore the total identified variation of
penA
. The divergent mosaic alleles differed by 3% to 24% compared to those of the designated wild-type
penA
gene. By studying the final 1,143 to 1,149 bp of
penA
in a sequence alignment, 130 sequence variants were identified. In a 402-bp alignment of the most variable regions, 84 variants were recognized. Good correlation between elevated MICs and the presence of
penA
mosaic structures was found especially for penicillin G and ampicillin. The Pen
i
isolates comprised an MIC of >0.094 μg/ml for penicillin G and an MIC of >0.064 μg/ml for ampicillin. Ampicillin was the best antibiotic for precise categorization as Pen
s
or Pen
i
. In comparison with the wild-type
penA
sequence, two specific Pen
i
sites were altered in all except two mosaic
penA
sequences, which were published in GenBank and no MICs of the corresponding isolates were described. In conclusion, monitoring the relationship between
penA
sequences and MICs to penicillins is crucial for developing fast and objective methods for susceptibility determination. By studying the
penA
gene, genotypical determination of susceptibility in culture-negative cases can also be accomplished.
Assessment of the Drug Susceptibility of
Plasmodium falciparum
Clinical Isolates from Africa by Using a
Plasmodium
Lactate Dehydrogenase Immunodetection Assay and an Inhibitory Maximum Effect Model for Precise Measurement of the 50-Percent Inhibitory Concentration
Authors: Kaddouri Halima , Nakache Serge , Houzé Sandrine , Mentré France , Le Bras Jacques 
Published: September 2006

ABSTRACT

The extension of drug resistance among malaria-causing
Plasmodium falciparum
parasites in Africa necessitates implementation of new combined therapeutic strategies. Drug susceptibility phenotyping requires precise measurements. Until recently, schizont maturation and isotopic in vitro assays were the only methods available, but their use was limited by technical constraints. This explains the revived interest in the development of replacement methods, such as the
Plasmodium
lactate dehydrogenase (pLDH) immunodetection assay. We evaluated a commercially controlled pLDH enzyme-linked immunosorbent assay (ELISA; the ELISA-Malaria antigen test; DiaMed AG, Cressier s/Morat, Switzerland) to assess drug susceptibility in a standard in vitro assay using fairly basic laboratory equipment to study the in vitro resistance of malaria parasites to major antimalarials. Five
Plasmodium falciparum
clones and 121 clinical African isolates collected during 2003 and 2004 were studied by the pLDH ELISA and the [8-
3
H]hypoxanthine isotopic assay as a reference with four antimalarials. Nonlinear regression with a maximum effect model was used to estimate the 50% inhibitory concentration (IC
50
) and its confidence intervals. The two methods were observed to have similar reproducibilities, but the pLDH ELISA demonstrated a higher sensitivity. The high correlation (
r
= 0.98) and the high phenotypic agreement (κ = 0.88) between the two methods allowed comparison by determination of the IC
50
s. Recently collected
Plasmodium falciparum
African isolates were tested by pLDH ELISA and showed drug resistance or decreased susceptibilities of 62% to chloroquine and 11.5% to the active metabolite of amodiaquine. No decreased susceptibility to lumefantrine or the active metabolite of artemisinin was detected. The availability of this simple and highly sensitive pLDH immunodetection assay will provide an easier method for drug susceptibility testing of malaria parasites.
Structure-Activity Relationships of
Bacillus cereus
and
Bacillus anthracis
Dihydrofolate Reductase: toward the Identification of New Potent Drug Leads
Authors: Joska Tammy M. , Anderson Amy C. 
Published: September 2006

ABSTRACT

New and improved therapeutics are needed for
Bacillus anthracis
, the etiological agent of anthrax. To date, antimicrobial agents have not been developed against the well-validated target dihydrofolate reductase (DHFR). In order to address whether DHFR inhibitors could have potential use as clinical agents against
Bacillus
, 27 compounds were screened against this enzyme from
Bacillus cereus
, which is identical to the enzyme from
B. anthracis
at the active site. Several 2,4-diamino-5-deazapteridine compounds exhibit submicromolar 50% inhibitory concentrations (IC
50
s). Four of the inhibitors displaying potency in vitro were tested in vivo and showed a marked growth inhibition of
B. cereus
; the most potent of these has MIC
50
and minimum bactericidal concentrations at which 50% are killed of 1.6 μg/ml and 0.09 μg/ml, respectively. In order to illustrate structure-activity relationships for the classes of inhibitors tested, each of the 27 inhibitors was docked into homology models of the
B. cereus
and
B. anthracis
DHFR proteins, allowing the development of a rationale for the inhibition profiles. A combination of favorable interactions with the diaminopyrimidine and substituted phenyl rings explains the low IC
50
values of potent inhibitors; steric interactions explain higher IC
50
values. These experiments show that DHFR is a reasonable antimicrobial target for
Bacillus anthracis
and that there is a class of inhibitors that possess sufficient potency and antibacterial activity to suggest further development.
Deletions of the Endocytic Components
VPS28
and
VPS32
in
Candida albicans
Lead to Echinocandin and Azole Hypersensitivity
Authors: Cornet Muriel , Gaillardin Claude , Richard Mathias L. 
Published: September 2006

ABSTRACT

Vps28p and Vps32p act in both the endocytic and the pH signaling pathways in yeasts and are required for
Candida albicans
virulence. Here, we show that deletions of
VPS28
and
VPS32
increase the susceptibility of
C. albicans
to cell wall disruption agents, echinocandin and azole antifungal agents.
Phase I Dose Escalation Study To Evaluate the Safety and Pharmacokinetic Profile of Tefibazumab in Subjects with End-Stage Renal Disease Requiring Hemodialysis
Authors: Hetherington Seth , Texter Michele , Wenzel Eric , Patti Joseph M. , Reynolds Laurie , Shamp Trish , Swan Suzanne 
Published: September 2006

ABSTRACT
Two cohorts of four subjects requiring hemodialysis received tefibazumab (10 or 20 mg/kg). The mean elimination half-life was between 17 and 18 days, the average volume of distribution was 7.3 liters, and the average clearance was 12 ml/h for both dose groups. At a dose of 20 mg/kg of body weight, plasma levels were 88 μg/ml at 21 days.
Potent Antihematozoan Activity of Novel Bisthiazolium Drug T16: Evidence for Inhibition of Phosphatidylcholine Metabolism in Erythrocytes Infected with
Babesia
and
Plasmodium
spp
Authors: Richier Eric , Biagini Giancarlo A. , Wein Sharon , Boudou Frederic , Bray Patrick G. , Ward Steve A. , Precigout Eric , Calas Michèle , Dubremetz Jean-François , Vial Henri J. 
Published: September 2006

ABSTRACT

A leading bisthiazolium drug, T16, designed to mimic choline, was shown to exert potent antibabesial activity, with 50% inhibitory concentrations of 28 and 7 nM against
Babesia divergens
and
B. canis
, respectively. T16 accumulated inside
Babesia
-infected erythrocytes (cellular accumulation ratio, >60) by a saturable process with an apparent

K
m

of 0.65 μM. Subcellular fractionation of
Babesia
parasites revealed the accumulation of T16 into a low-density fraction, while in malaria-infected erythrocytes a significant fraction of the drug was associated with heme malaria pigment. T16 exerts an early and specific inhibition of the de novo biosynthesis of phosphatidylcholine both in
B. divergens-
and
Plasmodium falciparum
-infected erythrocytes. Choline accumulation into isolated
Babesia
parasites was highly sensitive to inhibition by T16. These data are consistent with the hypothesis that bisthiazolium drugs target the de novo phosphatidylcholine biosynthesis of intraerythrocytic hematozoan parasites. In malaria parasites, which generate ferriprotoporphyrin IX during hemoglobin digestion, T16 binding to heme may enhance the accumulation and activity of the drug. The selectivity of accumulation and potent activity of this class of drug into parasite-infected erythrocytes offers unique advantages over more traditional antihematozoan drugs.
High-Throughput and Facile Assay of Antimicrobial Peptides Using pH-Controlled Fluorescence Resonance Energy Transfer
Authors: Kim Young Soo , Cha Hyung Joon 
Published: September 2006

ABSTRACT

Amphipathic antimicrobial peptides can destroy bacteria cells by inducing membrane permeabilization, forming one strategy for innate defense by various organisms. However, although the antimicrobial peptides are considered a promising alternative for use against multidrug-resistant bacteria, large-scale screening of potential candidate antimicrobial peptides will require a simple, rapid assay for antimicrobial activity. Here, we describe a novel fluorescence resonance energy transfer (FRET)-based assay system for antimicrobial peptides which takes advantage of pH-related changes in FRET efficiency due to the instability of enhanced yellow fluorescent protein versus the stability of enhanced cyan fluorescent protein in a reduced-pH environment. We successfully showed that quantification of antimicrobial activity is possible through a difference of FRET efficiency between ECFP-EYFP fusion molecules released from disrupted
Escherichia coli
in an extracellular environment (pH 6) and those retained in an intracellular environment (pH ∼7). Thus, we herein suggest a new simple, effective, and efficient pH-controlled FRET-based antimicrobial peptide screening method applicable to high-throughput screening of candidate peptide libraries.
In Vitro Susceptibility of
Clostridium difficile
Clinical Isolates from a Multi-Institutional Outbreak in Southern Québec, Canada
Authors: Bourgault Anne-Marie , Lamothe François , Loo Vivian G. , Poirier Louise ,   the CDAD-CSI Study Group
Published: September 2006

ABSTRACT

Clostridium difficile
isolates from a 2004 outbreak in Québec, Canada, were all found to be susceptible to metronidazole, vancomycin, rifampin, and meropenem but resistant to bacitracin, cefotaxime, ciprofloxacin, and levofloxacin, and most (>80%) were resistant to ceftriaxone, clarithromycin, gatifloxacin, and moxifloxacin. The predominant NAP1 isolates were susceptible to clindamycin, while the NAP2 isolates were resistant.
Enhanced Membrane Disruption and Antibiotic Action against Pathogenic Bacteria by Designed Histidine-Rich Peptides at Acidic pH
Authors: Mason A. James , Gasnier Claire , Kichler Antoine , Prévost Gilles , Aunis Dominique , Metz-Boutigue Marie-Hélène , Bechinger Burkhard 
Published: September 2006

ABSTRACT

The
histidine-rich amphipathic cationic peptide LAH4 has antibiotic and DNA
delivery capabilities. Here, we explore the interaction of peptides
from this family with model membranes as monitored by solid-state
2
H nuclear magnetic resonance and their antibiotic
activities against a range of bacteria. At neutral pH, the membrane
disruption is weak, but at acidic pH, the peptides strongly disturb the
anionic lipid component of bacterial membranes and cause bacterial
lysis. The peptides are effective antibiotics at both pH 7.2 and pH
5.5, although the antibacterial activity is strongly affected by the
change in pH. At neutral pH, the LAH peptides were active against both
methicillin-resistant and -sensitive
Staphylococcus aureus
strains but ineffective against
Pseudomonas aeruginosa
. In
contrast, the LAH peptides were highly active against
P.
aeruginosa
in an acidic environment, as is found in the
epithelial-lining fluid of cystic fibrosis patients. Our results show
that modest antibiotic activity of histidine-rich peptides can be
dramatically enhanced by inducing membrane disruption, in this case by
lowering the pH, and that histidine-rich peptides have potential as
future antibiotic
agents.
Comparative In Vitro Susceptibilities of 396 Unusual Anaerobic Strains to Tigecycline and Eight Other Antimicrobial Agents
Authors: Goldstein Ellie J. C. , Citron Diane M. , Merriam C. Vreni , Warren Yumi A. , Tyrrell Kerin L. , Fernandez Helen T. 
Published: September 2006

ABSTRACT

Tigecycline was tested against 396 strains of lesser-known anaerobic species encountered in human infections. It was active against all gram-positive strains and 228 of 232 gram-negative anaerobes at ≤1 μg/ml. One strain of
Prevotella oralis
was nonsusceptible at 8 μg/ml.
Development of a Human Immunodeficiency Virus Vector-Based, Single-Cycle Assay for Evaluation of Anti-Integrase Compounds
Authors: Bona Roberta , Andreotti Mauro , Buffa Viviana , Leone Pasqualina , Galluzzo Clementina Maria , Amici Roberta , Palmisano Lucia , Mancini Maria Grazia , Michelini Zuleika , Di Santo Roberto , Costi Roberta , Roux Alessandra , Pommier Yves , Marchand Christophe , Vella Stefano , Cara Andrea 
Published: September 2006

ABSTRACT
Therapeutic strategies aimed at inhibiting human immunodeficiency virus type 1 (HIV-1) replication employ a combination of drugs targeted to two viral enzymes (reverse transcriptase and protease) and to the viral entry/fusion step. However, the high propensity of HIV-1 to develop resistance makes the development of novel compounds targeting different steps of the HIV-1 life cycle essential. Among these, integrase (IN) inhibitors have successfully passed the early phases of clinical development. By preventing integration, IN inhibitors preclude viral replication while allowing production of extrachromosomal forms of viral DNA (E-DNA). Here, we describe an improved and standardized assay aimed at evaluating IN inhibitors by taking advantage of the transcriptional activity of E-DNA produced by HIV-derived vectors in the absence of replication-competent virus. In this context, the use of the firefly luciferase gene as a reporter gene provides a rapid and quantitative measure of viral-vector infectivity, thus making it a safe and cost-effective assay for evaluating novel IN inhibitors.
Origins and Evolution of Methicillin-ResistantStaphylococcus aureusClonal Lineages
Authors: Gomes A. R. , Westh H. , de Lencastre H. 
Published: September 2006

ABSTRACTMost methicillin-resistantStaphylococcus aureus(MRSA) isolates identified among blood isolates collected in Denmark between 1957 and 1970 belonged to either phage group III or the closely related 83A complex and had a PSTM antibiotype (resistance to penicillin [P], streptomycin [S], tetracycline [T], and methicillin [M]). Recently, some of these isolates were shown to have the same genetic backgrounds as contemporary epidemic MRSA isolates, and Danish methicillin-susceptibleS. aureus(MSSA) isolates from the 1960s with a PST antibiotype were proposed to have been the recipients of themecAgene in those lineages. In this study, we investigated the genetic backgrounds of isolates from the 83A complex that were fully susceptible or resistant to penicillin only in order to try to trace the evolutionary trajectory of contemporary MRSA lineages. We also studied MSSA and MRSA isolates from other phage groups in order to investigate if they had the potential to develop into contemporary MRSA clones. Most susceptible or penicillin-resistant isolates from phage group III or the 83A complex belonged to sequence type 8 (ST8) or ST5, while four isolates were ST254. STs 30, 45 and 25 were represented by MSSA isolates from other phage groups, which also included several singletons. Representatives of most of the current major epidemic MRSA lineages were identified among fully susceptible isolates collected in the 1960s, suggesting that these were MSSA lineages which carried genetic traits important for superior epidemicity before the acquisition of methicillin resistance.
Biofilm Formation by the Emerging Fungal Pathogen
Trichosporon asahii
: Development, Architecture, and Antifungal Resistance
Authors: Di Bonaventura Giovanni , Pompilio Arianna , Picciani Carla , Iezzi Manuela , D'Antonio Domenico , Piccolomini Raffaele 
Published: September 2006

ABSTRACT

Trichosporon asahii
is the most common cause of fatal disseminated trichosporonosis, frequently associated with indwelling medical devices. Despite the use of antifungal drugs to treat trichosporonosis, infection is often persistent and is associated with high mortality. This drove our interest in evaluating the capability of
T. asahii
to form a biofilm on biomaterial-representative polystyrene surfaces through the development and optimization of a reproducible
T. asahii
-associated biofilm model. Time course analyses of viable counts and a formazan salt reduction assay, as well as microscopy studies, revealed that biofilm formation by
T. asahii
occurred in an organized fashion through four distinct developmental phases: initial adherence of yeast cells (0 to 2 h), germination and microcolony formation (2 to 4 h), filamentation (4 to 6 h), and proliferation and maturation (24 to 72 h). Scanning electron microscopy and confocal scanning laser microscopy revealed that mature
T. asahii
biofilms (72-h) displayed a complex, heterogeneous three-dimensional structure, consisting of a dense network of metabolically active yeast cells and hyphal elements completely embedded within exopolymeric material. Antifungal susceptibility testing demonstrated a remarkable rise in the MICs of sessile
T. asahii
cells against clinically used amphotericin B, caspofungin, voriconazole, and fluconazole compared to their planktonic counterparts. In particular,
T. asahii
biofilms were up to 16,000 times more resistant to voriconazole, the most active agent against planktonic cells (MIC, 0.06 μg/ml). Our results suggest that the ability of
T. asahii
to form a biofilm may be a major factor in determining persistence of the infection in spite of in vitro susceptibility of clinical isolates.
Maribavir Antagonizes the Antiviral Action of Ganciclovir on Human Cytomegalovirus
Authors: Chou Sunwen , Marousek Gail I. 
Published: September 2006

ABSTRACT
The cytomegalovirus (CMV) UL97 kinase inhibitor maribavir antagonized the anti-CMV effect of ganciclovir, increasing the ganciclovir 50% inhibitory concentration against a sensitive strain by up to 13-fold. Antiviral activities of foscarnet and cidofovir were unaffected by maribavir.
Bile Salt-Stimulated Lipase from Human Milk Binds DC-SIGN and Inhibits Human Immunodeficiency Virus Type 1 Transfer to CD4
+
T Cells
Authors: Naarding Marloes A. , Dirac Annette M. , Ludwig Irene S. , Speijer Dave , Lindquist Susanne , Vestman Eva-Lotta , Stax Martijn J. , Geijtenbeek Teunis B. H. , Pollakis Georgios , Hernell Olle , Paxton William A. 
Published: September 2006

ABSTRACT

A wide range of pathogens, including human immunodeficiency virus type 1 (HIV-1), hepatitis C virus, Ebola virus, cytomegalovirus, dengue virus,
Mycobacterium
,
Leishmania
, and
Helicobacter pylori
, can interact with dendritic cell (DC)-specific ICAM3-grabbing nonintegrin (DC-SIGN), expressed on DCs and a subset of B cells. More specifically, the interaction of the gp120 envelope protein of HIV-1 with DC-SIGN can facilitate the transfer of virus to CD4
+
T lymphocytes in
trans
and enhance infection. We have previously demonstrated that a multimeric Le
X
component in human milk binds to DC-SIGN, preventing HIV-1 from interacting with this receptor. Biochemical analysis reveals that the compound is heat resistant, trypsin sensitive, and larger than 100 kDa, indicating a specific glycoprotein as the inhibitory compound. By testing human milk from three different mothers, we found the levels of DC-SIGN binding and viral inhibition to vary between samples. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blotting, and matrix-assisted laser desorption ionization analysis, we identified bile salt-stimulated lipase (BSSL), a Lewis X (Le
X
)-containing glycoprotein found in human milk, to be the major variant protein between the samples. BSSL isolated from human milk bound to DC-SIGN and inhibited the transfer of HIV-1 to CD4
+
T lymphocytes. Two BSSL isoforms isolated from the same human milk sample showed differences in DC-SIGN binding, illustrating that alterations in the BSSL forms explain the differences observed. These results indicate that variations in BSSL lead to alterations in Le
X
expression by the protein, which subsequently alters the DC-SIGN binding capacity and the inhibitory effect on HIV-1 transfer. Identifying the specific molecular interaction between the different forms may aid in the future design of antimicrobial agents.
Inhibition of Filamentation Can Be Used To Treat Disseminated Candidiasis
Authors: Saville Stephen P. , Lazzell Anna L. , Bryant Alexander P. , Fretzen Angelika , Monreal Alex , Solberg Erik O. , Monteagudo Carlos , Lopez-Ribot Jose L. , Milne G. Todd 
Published: September 2006

ABSTRACT

Candida albicans
remains the leading causative agent of invasive fungal infection. Although the importance of filamentation in
C. albicans
pathogenesis has been extensively investigated, in vivo studies to date have been unable to dissect the role of this developmental process in the establishment of infection versus the development of active disease as characterized by damage to the host leading to mortality. To address this issue, we genetically engineered a
C. albicans tet-NRG1
strain in which filamentation and virulence can be modulated both in vitro and in vivo simply by the presence or absence of doxycycline (DOX): this strain enabled us, in a prior study, to demonstrate that yeast-form cells were able to infect the deep organs but caused no disease unless filamentation (induced by the addition of DOX) was allowed to occur. In the present study, we examined whether inhibiting filamentation (by withdrawing the DOX) at 24 or 48 h postinfection could serve as an effective therapeutic intervention against candidiasis. The results obtained indicate that DOX removal led to an alteration in the morphology of the infecting fungal cells and a dramatic increase in survival, but as with conventional antifungal drug therapy regimens, mortality rates increased markedly the longer this intervention was delayed. These observations reinforce the importance of invasive filamentous growth in causing the damage to the host and the lethality associated with active disease and suggest this process could be fruitfully targeted for the development of new antifungal agents.
Reactivity of (1→3)-β-
d
-Glucan Assay with Commonly Used Intravenous Antimicrobials
Authors: Marty Francisco M. , Lowry Colleen M. , Lempitski Steven J. , Kubiak David W. , Finkelman Malcolm A. , Baden Lindsey R. 
Published: September 2006

ABSTRACT

Forty-four intravenous antimicrobials were tested for the presence of (1→3)-β-
d
-glucan (BG). Colistin, ertapenem, cefazolin, trimethoprim-sulfamethoxazole, cefotaxime, cefepime, and ampicillin-sulbactam tested positive for BG at reconstituted-vial concentrations but not when diluted to usual maximum plasma concentrations. False-positive BG assays may occur when some antimicrobials are administered; however, this needs to be confirmed.