bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro Activities of 10 Combinations of Antifungal Agents against the Multiresistant Pathogen
Scopulariopsis brevicaulis
Authors: Cuenca-Estrella Manuel , Gomez-Lopez Alicia , Buitrago Maria J. , Mellado Emilia , Garcia-Effron Guillermo , Rodriguez-Tudela Juan L.
Published: May 2006

The activities of 10 combinations of antifungal agents against 25 clinical isolates of
Scopulariopsis brevicaulis
were tested by the checkerboard technique. An average indifferent effect was detected for all combinations. Synergy was observed for some isolates and combinations, particularly with posaconazole-terbinafine (68% of strains), amphotericin B-caspofungin (60%), and posaconazole-caspofungin (48%).
In Vitro Activities of Posaconazole, Fluconazole, Itraconazole, Voriconazole, and Amphotericin B against a Large Collection of Clinically Important Molds and Yeasts
Authors: Sabatelli F. , Patel R. , Mann P. A. , Mendrick C. A. , Norris C. C. , Hare R. , Loebenberg D. , Black T. A. , McNicholas P. M.
Published: May 2006

The in vitro activity of the novel triazole antifungal agent posaconazole (Noxafil; SCH 56592) was assessed in 45 laboratories against approximately 19,000 clinically important strains of yeasts and molds. The activity of posaconazole was compared with those of itraconazole, fluconazole, voriconazole, and amphotericin B against subsets of the isolates. Strains were tested utilizing Clinical and Laboratory Standards Institute broth microdilution methods using RPMI 1640 medium (except for amphotericin B, which was frequently tested in antibiotic medium 3). MICs were determined at the recommended endpoints and time intervals. Against all fungi in the database (22,850 MICs), the MIC
50
and MIC
90
values for posaconazole were 0.063 μg/ml and 1 μg/ml, respectively. MIC
90
values against all yeasts (18,351 MICs) and molds (4,499 MICs) were both 1 μg/ml. In comparative studies against subsets of the isolates, posaconazole was more active than, or within 1 dilution of, the comparator drugs itraconazole, fluconazole, voriconazole, and amphotericin B against approximately 7,000 isolates of
Candida
and
Cryptococcus
spp. Against all molds (1,702 MICs, including 1,423 MICs for
Aspergillus
isolates), posaconazole was more active than or equal to the comparator drugs in almost every category. Posaconazole was active against isolates of
Candida
and
Aspergillus
spp. that exhibit resistance to fluconazole, voriconazole, and amphotericin B and was much more active than the other triazoles against zygomycetes. Posaconazole exhibited potent antifungal activity against a wide variety of clinically important fungal pathogens and was frequently more active than other azoles and amphotericin B.
Targeting Antibacterial Agents by Using Drug-Carrying Filamentous Bacteriophages
Authors: Yacoby Iftach , Shamis Marina , Bar Hagit , Shabat Doron , Benhar Itai
Published: May 2006

Bacteriophages have been used for more than a century for (unconventional) therapy of bacterial infections, for half a century as tools in genetic research, for 2 decades as tools for discovery of specific target-binding proteins, and for nearly a decade as tools for vaccination or as gene delivery vehicles. Here we present a novel application of filamentous bacteriophages (phages) as targeted drug carriers for the eradication of (pathogenic) bacteria. The phages are genetically modified to display a targeting moiety on their surface and are used to deliver a large payload of a cytotoxic drug to the target bacteria. The drug is linked to the phages by means of chemical conjugation through a labile linker subject to controlled release. In the conjugated state, the drug is in fact a prodrug devoid of cytotoxic activity and is activated following its dissociation from the phage at the target site in a temporally and spatially controlled manner. Our model target wasStaphylococcus aureus, and the model drug was the antibiotic chloramphenicol. We demonstrated the potential of using filamentous phages as universal drug carriers for targetable cells involved in disease. Our approach replaces the selectivity of the drug itself with target selectivity borne by the targeting moiety, which may allow the reintroduction of nonspecific drugs that have thus far been excluded from antibacterial use (because of toxicity or low selectivity). Reintroduction of such drugs into the arsenal of useful tools may help to combat emerging bacterial antibiotic resistance.
Microdialysis Study of Imipenem Distribution in Skeletal Muscle and Lung Extracellular Fluids of
Acinetobacter baumannii
-Infected Rats
Authors: Dahyot Claire , Marchand Sandrine , Pessini Greisiele Lorena , Pariat Claudine , Debaene Bertrand , Couet William , Mimoz Olivier
Published: May 2006

The aim of this study was to investigate imipenem distribution in muscle and lung interstitial fluids of rats with
Acinetobacter baumannii
pulmonary infection. By combining microdialysis in blood and tissues, it was possible to demonstrate that free imipenem concentrations were virtually identical in blood, muscle, and lung.
Antimicrobial Susceptibility of Invasive
Streptococcus pneumoniae
Isolates in Portugal over an 11-Year Period
Authors: Dias Ricardo , Louro Deolinda ,   the Antimicrobial Resistance Surveillance Program in Portugal, Caniça Manuela
Published: May 2006

This national surveillance study presents the in vitro activities of the main antimicrobial agents against 1,331
S. pneumoniae
isolates as tested by an agar dilution method according to the guidelines of the Clinical and Laboratory Standards Institute (formerly NCCLS). The strains were isolated in several regions of Portugal from cases of invasive disease over an 11-year period (1994 to 2004). This study shows that the percentage of penicillin-nonsusceptible strains increased from 12% in 1994 to 28.5% in 2000. Then the rate declined to 17.7% in 2003 but increased again to 23.2% in 2004. Nevertheless, the rate of highly resistant isolates declined consistently, to 0.9% in 2001 to 2004. Ceftriaxone- and cefotaxime-nonsusceptible isolates became less frequent, from 4% and 8%, respectively, in 1994 to ≤1% in 2004. The macrolide-lincosamide-streptogramin B phenotype was the predominant macrolide phenotype found. The increase in the percentage of isolates that were only nonsusceptible to erythromycin (3.7% in 1994 to 1998 to 9.1% in 2002 to 2004) was similar to that for isolates with coresistance to penicillin and erythromycin (3.3% in 1994 to 1998 to 9.1% in 2002 to 2004). The nonsusceptibility to ciprofloxacin increased during recent years, from 0.5% in 2002 to 3.5% in 2004. Multidrug resistance also increased in recent years: from 7.9% in 2002 to 15.6% in 2004. The increasing use of macrolides could be causing the increase in penicillin and multidrug resistance, due to the coresistance to macrolides. The use of penicillin to treat empirical invasive pneumococci infections may need to be reconsidered.
Comparative Efficacies, Toxicities, and Tissue Concentrations of Amphotericin B Lipid Formulations in a Murine Pulmonary Aspergillosis Model
Authors: Olson Jon A. , Adler-Moore Jill P. , Schwartz Julie , Jensen Gerard M. , Proffitt Richard T.
Published: May 2006

Invasive aspergillosis, an important cause of morbidity and mortality in immunosuppressed (IS) patients, is often treated with amphotericin B lipid formulations. In the present study, liposomal amphotericin B (L-AMB) and amphotericin B lipid complex (ABLC) were compared in treatment of murine pulmonary aspergillosis. Uninfected, IS mice were treated for 4 days with 1, 4, 8, or 12 mg L-AMB or ABLC/kg of body weight, and their lungs were analyzed by high-performance liquid chromatography for drug concentrations. IS mice intranasally challenged with
Aspergillus fumigatus
were treated with 12, 15, or 20 mg/kg L-AMB or ABLC and monitored for survival, fungal burden (CFU), and tissue drug concentration. Blood urea nitrogen (BUN) levels and kidney histopathology were determined for uninfected and infected mice given 15 or 20 mg/kg L-AMB or ABLC. The results showed that both drugs had therapeutic levels of drug (>3.0 μg/g) in the lungs of uninfected or infected mice, and 24 h after the last dose, ABLC levels were significantly higher than L-AMB levels (
P
< 0.02). L-AMB and ABLC at 12 mg/kg both produced 57% survival, but only L-AMB at 15 or 20 mg/kg further increased survival to 80 to 90%, with BUN levels and kidney morphology similar to those of controls. Survival at 15 or 20 mg/kg ABLC was not significantly different than that of controls, and BUN levels were significantly elevated, with tubular alterations in uninfected animals and acute necrosis in kidney tubules of infected animals. In conclusion, although both drugs were effective in prolonging survival at 12 mg/kg, the reduced nephrotoxicity of L-AMB increased its therapeutic index, allowing for its safe and effective use at 15 or 20 mg/kg.
Clinical Correlation of the CLSI Susceptibility Breakpoint for Piperacillin- Tazobactam against Extended-Spectrum-β-Lactamase-Producing
Escherichia coli
and
Klebsiella
Species
Authors: Gavin Patrick J. , Suseno Mira T. , Thomson Richard B. , Gaydos J. Michael , Pierson Carl L. , Halstead Diane C. , Aslanzadeh Jaber , Brecher Stephen , Rotstein Coleman , Brossette Stephen E. , Peterson Lance R.
Published: May 2006

We assessed infections caused by extended-spectrum-β-lactamase-producing
Escherichia coli
or
Klebsiella
spp. treated with piperacillin-tazobactam to determine if the susceptibility breakpoint predicts outcome. Treatment was successful in 10 of 11 nonurinary infections from susceptible strains and in 2 of 6 infections with MICs of >16/4 μg/ml. All six urinary infections responded to treatment regardless of susceptibility.
Synergistic In Vitro Antiretroviral Activity of a Humanized Monoclonal Anti-CD4 Antibody (TNX-355) and Enfuvirtide (T-20)
Authors: Zhang Xing-Quan , Sorensen Meredith , Fung Michael , Schooley Robert T.
Published: May 2006

Recently, antiretroviral agents directed at several steps involved in viral entry have been shown to reduce viral replication in vitro and in vivo. We have demonstrated a high level of in vitro synergistic antiretroviral activity for two entry inhibitors that are directed at sequential steps in the entry process.
Using Interrupted Time Series Analysis To Assess Associations of Fluoroquinolone Formulary Changes with Susceptibility of Gram-Negative Pathogens and Isolation Rates of Methicillin-Resistant
Staphylococcus aureus
Authors: Bosso John A. , Mauldin Patrick D.
Published: May 2006

The use of fluoroquinolones has been linked to increasing bacterial resistance and infection and/or colonization with already resistant pathogens both as a risk factor and based on volume of use. Changes in individual fluoroquinolones used in an institution may also be related to these clinical problems. Interrupted time series analysis, which allows for assessment of the associations of an outcome attributable to a specific event in time, was used to study the effect of changes in our hospital's fluoroquinolone formulary on fluoroquinolone susceptibility rates in select gram-negative pathogens and the methicillin-resistant
Staphylococcus aureus
(MRSA) isolation rate. Susceptibility rates to ciprofloxacin were considered for the period of 1993 through 2004, while the MRSA isolation rate was assessed from 1995 through 2004. Levofloxacin was added to the formulary in 1999, and gatifloxacin was substituted for levofloxacin in 2001. Statistically significant changes in the already declining rates of susceptibility of
Pseudomonas aeruginosa
(
P
, 0.042) and
Escherichia coli
(
P
, 0.004) to ciprofloxacin and in the already rising MRSA isolation rate (
P
, 0.001) were associated with the addition of levofloxacin to the formulary. Substitution of gatifloxacin for levofloxacin on the formulary was associated with reversals in the downward trend in
E. coli
susceptibility to ciprofloxacin and the upward trend in MRSA isolation rate. No associations were detected on susceptibility of
Klebsiella pneumoniae
or
Proteus mirabilis
to ciprofloxacin. These findings suggest that potential changes in susceptibility to fluoroquinolones and isolation of MRSA may vary by both drug and organism.
In Vitro and In Vivo Antibacterial Activities of DW-224a, a New Fluoronaphthyridone
Authors: Park Hee-Soo , Kim Hyun-Joo , Seol Min-Jung , Choi Dong-Rack , Choi Eung-Chil , Kwak Jin-Hwan
Published: May 2006

DW-224a showed the most potent in vitro activity among the quinolone compounds tested against clinical isolates of gram-positive bacteria. Against gram-negative bacteria, DW-224a was slightly less active than the other fluoroquinolones. The in vivo activities of DW-224a against gram-positive bacteria were more potent than those of other quinolones.
Inhibition of Mammalian Mitochondrial Protein Synthesis by Oxazolidinones
Authors: McKee E. E. , Ferguson M. , Bentley A. T. , Marks T. A.
Published: May 2006

The effects of a variety of oxazolidinones, with different antibacterial potencies, including linezolid, on mitochondrial protein synthesis were determined in intact mitochondria isolated from rat heart and liver and rabbit heart and bone marrow. The results demonstrate that a general feature of the oxazolidinone class of antibiotics is the inhibition of mammalian mitochondrial protein synthesis. Inhibition was similar in mitochondria from all tissues studied. Further, oxazolidinones that were very potent as antibiotics were uniformly potent in inhibiting mitochondrial protein synthesis. These results were compared to the inhibitory profiles of other antibiotics that function by inhibiting bacterial protein synthesis. Of these, chloramphenicol and tetracycline were significant inhibitors of mammalian mitochondrial protein synthesis while the macrolides, lincosamides, and aminoglycosides were not. Development of future antibiotics from the oxazolidinone class will have to evaluate potential mitochondrial toxicity.
Impact of Human Immunodeficiency Virus Type 1 Subtype C on Drug Resistance Mutations in Patients from Botswana Failing a Nelfinavir-Containing Regimen
Authors: Doualla-Bell Florence , Avalos Ava , Gaolathe Tendani , Mine Madisa , Gaseitsiwe Simani , Ndwapi Ndwapi , Novitsky Vladimir A. , Brenner Bluma , Oliveira Maureen , Moisi Daniella , Moffat Howard , Thior Ibou , Essex Max , Wainberg Mark A.
Published: May 2006

Among 16 human immunodeficiency virus-infected (subtype C) Batswana patients who failed nelfinavir (NFV)-containing regimens, the most prevalent mutation observed was D30N (54%), followed by L90M (31%). L89I, K20T/I, and E35D polymorphic changes were also identified. These findings suggest that subtype C viruses in Botswana may develop resistance to NFV via subtype-specific pathways.
Model System To Evaluate the Effect ofampDMutations on AmpC-Mediated β-Lactam Resistance
Authors: Schmidtke Amber J. , Hanson Nancy D.
Published: May 2006

Mutations within the structural gene ofampDcan lead to AmpC overproduction and increases in β-lactam MICs in organisms with an inducibleampC. However, identification of mutations alone cannot predict the impact that those mutations have on AmpD function. Therefore, a model system was designed to determine the effect ofampDmutations on ceftazidime MICs using an AmpD−mutantEscherichia colistrain which produced an inducible plasmid-encoded AmpC.ampDgenes were amplified by PCR from strains ofE. coli,Citrobacter freundii, andPseudomonas aeruginosa. Also, carboxy-terminal truncations ofC. freundii ampDgenes were constructed representing deletions of 10, 21, or 25 codons. AmplifiedampDproducts were cloned into pACYC184 containing inducibleblaACT-1-ampR. Plasmids were transformed intoE. colistrains JRG582 (AmpD−) and K-12 259 (AmpD+). The strains were evaluated for a derepressed phenotype using ceftazidime MICs. Some mutatedampDgenes, including theampDgene of a derepressedC. freundiiisolate, resulted in substantial decreases in ceftazidime MICs (from >256 μg/ml to 12 to 24 μg/ml) for the AmpD−strain, indicating no role for these mutations in derepressed phenotypes. However,ampDtruncation products andampDfrom a partially derepressedP. aeruginosastrain resulted in ceftazidime MICs of >256 μg/ml, indicating a role for these gene modifications in derepressed phenotypes. The use of this model system indicated that alternative mechanisms were involved in the derepressed phenotype observed in strains ofC. freundiiandP. aeruginosa. The alternative mechanism involved in the derepressed phenotype of theC. freundiiisolate was downregulation ofampDtranscription.
Recombinant
Eimeria
Protozoan Protein Elicits Resistance to Acute Phlebovirus Infection in Mice but Not Hamsters
Authors: Gowen Brian B. , Smee Donald F. , Wong Min-Hui , Judge John W. , Jung Kie-Hoon , Bailey Kevin W. , Pace Anne M. , Rosenberg Barnett , Sidwell Robert W.
Published: May 2006

A protein antigen from an
Eimeria
protozoan has recently been reported to induce antitumor activity in mice. This activity most likely results from the strong induction of interkeukin-12 (IL-12) and gamma interferon (IFN-γ), which are also essential factors in the establishment of protective immunity against viral infection. We evaluated recombinant
Eimeria
antigen (rEA) as a potential immunotherapeutic agent in mouse and hamster models of acute phleboviral disease. Punta Toro virus (PTV) was highly sensitive to a single dose of nanogram quantities of rEA in the mouse infection model. Intraperitoneal treatment with rEA also reduced virus load and liver damage associated with PTV infection. IL-12 was elicited following exposure of uninfected mice to quantities of rEA of 10 ng or greater, and the levels peaked at between 3 and 8 h postexposure. IFN-γ release was induced more slowly and required less rEA (1 ng) to produce a significant rise in systemic levels. The induction of IL-12 and IFN-γ involved in the coordination of innate and adaptive immune responses to microbial pathogens required myeloid differentiation factor 88, a signaling adaptor shared by most members of the Toll-like receptor (TLR) family. Despite encouraging results in the murine system, rEA failed to protect hamsters challenged with PTV. Our findings suggest that hamsters may lack functional TLR11, which has recently been shown to recognize a profilin-like protein homologous to rEA from the protozoan
Toxoplasma gondii
. Further investigation into the immunostimulatory capacity of rEA in other mammalian systems is necessary.
Effect of Porins and Plasmid-Mediated AmpC β-Lactamases on the Efficacy of β-Lactams in Rat Pneumonia Caused by
Klebsiella pneumoniae
Authors: Padilla Emma , Alonso Diana , Doménech-Sánchez Antonio , Gomez Cristina , Pérez José Luis , Albertí Sebastián , Borrell Nuria
Published: May 2006

The in vivo activities of imipenem, meropenem, and cefepime were studied in a model of rat pneumonia caused by a plasmid-mediated AmpC β-lactamase ACT-1-producing
Klebsiella pneumoniae
strain (
K. pneumoniae
strain 12) and a derivative porin-deficient mutant (
K. pneumoniae
strain 12dp). No differences between these activities were seen with
K. pneumoniae
12. Only meropenem showed an activity slightly better than that of imipenem with
K. pneumoniae
12dp.
Novel Mobile Variants of Staphylococcal Cassette Chromosome
mec
in
Staphylococcus aureus
Authors: Jansen W. T. M. , Beitsma M. M. , Koeman C. J. , van Wamel W. J. B. , Verhoef J. , Fluit A. C.
Published: May 2006

Staphylococcus aureus
staphylococcal cassette chromosome
mec
type IV (SSC
mec
IV) is associated with virulent community-acquired methicillin-resistant
Staphylococcus aureus
(MRSA) and frequent horizontal transfer among staphylococci. To gain insight into the mechanism of transfer, we studied the
ccrA/B
type 2 recombinase-mediated excision of SCC
mec
IV (
n
= 5 strains) and SCC
mec
II (
n
= 2). In SCC
mec
IV- but not SCC
mec
II-containing strains, spontaneous excision of the cassette was observed. Introduction of
ccrA/B
type 2 recombinase genes under control of an
S. aureus
bacterial phage promoter in the different strains yielded excision of SCC
mec
II and multiple excision variants of SCC
mec
IV. Sequencing of the alternatively excised products in SCC
mec
IV strains identified a 100-bp shortened SCC
mec
′ variant and a 5,877-bp, conserved SCC-like element that lacks
mecA
and
ccrA/B
recombinases. Excision of the SCC-like element in wild-type
S. aureus
was dependent on the presence of SCC
mec
. The element could be excised separately or as part of a novel composite cassette together with SCC
mec
. The relative abundance of and variety in SCC
mec
IV excisions may contribute to the frequency of horizontal transfer and genetic plasticity in SCC
mec
IV MRSA strains.
Biosynthetic Pathway for Mannopeptimycins, Lipoglycopeptide Antibiotics Active against Drug-Resistant Gram-Positive Pathogens
Authors: Magarvey Nathan A. , Haltli Brad , He Min , Greenstein Michael , Hucul John A.
Published: May 2006

The mannopeptimycins are a novel class of lipoglycopeptide antibiotics active against multidrug-resistant pathogens with potential as clinically useful antibacterials. This report is the first to describe the biosynthesis of this novel class of mannosylated lipoglycopeptides. Included here are the cloning, sequencing, annotation, and manipulation of the mannopeptimycin biosynthetic gene cluster from
Streptomyces hygroscopicus
NRRL 30439. Encoded by genes within the mannopeptimycin biosynthetic gene cluster are enzymes responsible for the generation of the hexapeptide core (nonribosomal peptide synthetases [NRPS]) and tailoring reactions (mannosylation, isovalerylation, hydroxylation, and methylation). The NRPS system is noncanonical in that it has six modules utilizing only five amino acid-specific adenylation domains and it lacks a prototypical NRPS macrocyclizing thioesterase domain. Analysis of the mannopeptimycin gene cluster and its engineering has elucidated the mannopeptimycin biosynthetic pathway and provides the framework to make new and improved mannopeptimycins biosynthetically.
Mechanism of Enhanced Activity of Liposome-Entrapped Aminoglycosides against Resistant Strains of
Pseudomonas aeruginosa
Authors: Mugabe Clement , Halwani Majed , Azghani Ali O. , Lafrenie Robert M. , Omri Abdelwahab
Published: May 2006

Pseudomonas aeruginosa
is inherently resistant to most conventional antibiotics. The mechanism of resistance of this bacterium is mainly associated with the low permeability of its outer membrane to these agents. We sought to assess the bactericidal efficacy of liposome-entrapped aminoglycosides against resistant clinical strains of
P. aeruginosa
and to define the mechanism of liposome-bacterium interactions. Aminoglycosides were incorporated into liposomes, and the bactericidal efficacies of both free and liposomal drugs were evaluated. To define the mechanism of liposome-bacterium interactions, transmission electron microscopy (TEM), flow cytometry, lipid mixing assay, and immunocytochemistry were employed. Encapsulation of aminoglycosides into liposomes significantly increased their antibacterial activity against the resistant strains used in this study (MICs of ≥32 versus ≤8 μg/ml). TEM observations showed that liposomes interact intimately with the outer membrane of
P. aeruginosa
, leading to the membrane deformation. The flow cytometry and lipid mixing assays confirmed liposome-bacterial membrane fusion, which increased as a function of incubation time. The maximum fusion rate was 54.3% ± 1.5% for an antibiotic-sensitive strain of
P. aeruginosa
and 57.8% ± 1.9% for a drug-resistant strain. The fusion between liposomes and
P. aeruginosa
significantly enhanced the antibiotics' penetration into the bacterial cells (3.2 ± 2.3 versus 24.2 ± 6.2 gold particles/bacterium,
P
≤ 0.001). Our data suggest that liposome-entrapped antibiotics could successfully resolve infections caused by antibiotic-resistant
P. aeruginosa
through an enhanced mechanism of drug entry into the bacterial cells.
Postgenomic Scan of Metallo-β-Lactamase Homologues in Rhizobacteria: Identification and Characterization of BJP-1, a Subclass B3 Ortholog fromBradyrhizobium japonicum
Authors: Stoczko Magdalena , Frère Jean-Marie , Rossolini Gian Maria , Docquier Jean-Denis
Published: May 2006

The diffusion of metallo-β-lactamases (MBLs) among clinically important human pathogens represents a therapeutic issue of increasing importance. However, the origin of these resistance determinants is largely unknown, although an important number of proteins belonging to the MBL superfamily have been identified in microbial genomes. In this work, we analyzed the distribution and function of genes encoding MBL-like proteins in the classRhizobiales. Among 12 released complete genomes of members of the classRhizobiales, a total of 57 open reading frames (ORFs) were found to have the MBL conserved motif and identity scores with MBLs ranging from 8 to 40%. On the basis of the best identity scores with known MBLs, four ORFs were cloned intoEscherichia colifor heterologous expression. Among their products, one (blr6230) encoded by theBradyrhizobium japonicumUSDA110 genome, named BJP-1, hydrolyzed β-lactams when expressed inE. coli. BJP-1 enzyme is most closely related to the CAU-1 enzyme fromCaulobacter vibrioides(40% amino acid sequence identity), a member of subclass B3 MBLs. A kinetic analysis revealed that BJP-1 efficiently hydrolyzed most β-lactam substrates, except aztreonam, ticarcillin, and temocillin, with the highest catalytic efficiency measured with meropenem. Compared to other MBLs, BJP-1 was less sensitive to inactivation by chelating agents.
Diminished Macrophage Inflammatory Response to
Staphylococcus aureus
Isolates Exposed to Daptomycin versus Vancomycin or Oxacillin
Authors: English B. Keith , Maryniw Erik M. , Talati Ajay J. , Meals Elizabeth A.
Published: May 2006

Exposure of any of six clinical isolates of
Staphylococcus aureus
to daptomycin alone or in combination with vancomycin or oxacillin (compared with vancomycin or oxacillin alone) led to a dampened macrophage inflammatory response with diminished tumor necrosis factor secretion and reduced accumulation of inducible nitric oxide synthase protein.
DNA Microarray for Detection of Macrolide Resistance Genes
Authors: Cassone Marco , D'Andrea Marco M. , Iannelli Francesco , Oggioni Marco R. , Rossolini Gian Maria , Pozzi Gianni
Published: May 2006

A DNA microarray was developed to detect bacterial genes conferring resistance to macrolides and related antibiotics. A database containing 65 nonredundant genes selected from publicly available DNA sequences was constructed and used to design 100 oligonucleotide probes that could specifically detect and discriminate all 65 genes. Probes were spotted on a glass slide, and the array was reacted with DNA templates extracted from 20 reference strains of eight different bacterial species (
Streptococcus pneumoniae
,
Streptococcus pyogenes
,
Enterococcus faecalis
,
Enterococcus faecium
,
Staphylococcus aureus
,
Staphylococcus haemolyticus
,
Escherichia coli
, and
Bacteroides fragilis
) known to harbor 29 different macrolide resistance genes. Hybridization results showed that probes reacted with, and only with, the expected DNA templates and allowed discovery of three unexpected genes, including
msr
(SA) in
B. fragilis
, an efflux gene that has not yet been described for gram-negative bacteria.
Activity of Gatifloxacin in an In Vitro Pharmacokinetic-Pharmacodynamic Model against
Staphylococcus aureus
Strains either Susceptible to Ciprofloxacin or Exhibiting Various Levels and Mechanisms of Ciprofloxacin Resistance
Authors: Ba Boubakar B. , Arpin Corinne , Vidaillac Céline , Chausse Arnaud , Saux Marie-Claude , Quentin Claudine
Published: May 2006

Gatifloxacin (GAT) is a new 8-methoxy fluoroquinolone with enhanced activity against gram-positive cocci. Its activity was studied in an in vitro pharmacokinetic-pharmacodynamic model against five
Staphylococcus aureus
strains, either susceptible to ciprofloxacin or exhibiting various levels and mechanisms of ciprofloxacin (CIP) resistance: the ATCC 25923 reference strain (MICs of CIP and GAT: 0.5 and 0.1 μg/ml, respectively), its efflux mutant SA-1 (16 and 0.5 μg/ml; mutation in the
norA
promoter region), and three clinical strains, Sa2102 (2 and 0.2 μg/ml), Sa2667 (4 and 0.5 μg/ml), and Sa2669 (16 and 1 μg/ml), carrying mutations in the
grlA
(Ser80Tyr or Phe) and
gyrA
(Ser84Ala) quinolone resistance-determining regions (QRDRs) for Sa2669. Plasmatic pharmacokinetic profiles after daily 1-h perfusion of 400 mg for 48 h were accurately simulated. Thus, mean maximum concentration of drug in serum values for the two administration intervals were 5.36 and 5.80 μg/ml, respectively, and the corresponding half-life at β-phase values were 8.68 and 7.80 h (goodness of fit coefficient, >0.98). Therapeutic concentrations of GAT allowed the complete eradication of the susceptible strain within 12 h (difference between the bacterial counts at the beginning of the treatment and at a defined time: −2.18 at the 1-h time point [
t
1
] and −6.80 at
t
24
and
t
48
; the bacterial killing and regrowth curve from 0 to 48 h was 30.2 h × log CFU/milliliter). However, mutants (M) with GAT MICs increased by 4- to 40-fold were selected from the other strains. They acquired mutations either supplementary (MSa2102 and MSa2667) or different (Ala84Val for MSa2669) in
gyrA
or in both
gyrA
and
grlA
QRDRs (MSA-1). MSa2667 additionally overproduced efflux system(s) without
norA
promoter modification. Thus, GAT properties should allow the total elimination of ciprofloxacin-susceptible
S. aureus
, but resistant mutants might emerge from strains showing reduced susceptibility to older fluoroquinolones independently of the first-step mutation(s).
Pregnancy-Related Effects on Nelfinavir-M8 Pharmacokinetics: a Population Study with 133 Women
Authors: Hirt Déborah , Treluyer Jean-Marc , Jullien Vincent , Firtion Ghislaine , Chappuy Hélène , Rey Elisabeth , Pons Gérard , Mandelbrot Laurent , Urien Saïk
Published: May 2006

A relationship between nelfinavir antiretroviral efficacy and plasma concentrations has been previously established. As physiological changes associated with pregnancy have a large impact on the pharmacokinetics of many drugs, a nelfinavir population study with women was developed, and the large intersubject variability was analyzed in order to optimize individual treatment schedules for this drug during pregnancy. A population pharmacokinetic model was developed in order to describe the concentration time course of nelfinavir and its metabolite M8 in pregnant and nonpregnant women. Individual characteristics, such as age, body weight, and weeks of gestation or delivery, which may influence nelfinavir-M8 pharmacokinetics were investigated. Data from therapeutic drug monitoring in 133 women treated with nelfinavir were retrospectively analyzed with NONMEM. Nelfinavir pharmacokinetics was described by a one-compartment model with linear absorption and elimination and M8 produced from the nelfinavir central compartment. Mean pharmacokinetic estimates and the corresponding intersubject percent variabilities for a nonpregnant woman were the following: absorption rate, 0.83 h−1; absorption lag time, 0.85 h; apparent nelfinavir elimination clearance (CL10/F), 35.5 liters/h (50%); apparent volume of distribution (V/F), 596 liters (118%); apparent formation clearance to M8 (CL1M/F), 0.65 liters/h (69%); and M8 elimination rate constant (kM0), 3.3 h−1(59%). During pregnancy, we observed significant increases in nelfinavir (44.4 liters/h) and M8 (5 h−1) elimination but unchanged nelfinavir transformation clearance to M8, suggesting an induction of CYP3A4 but no effect on CYP2C19. Apparent nelfinavir clearance and volume showed a twofold increase on the day of delivery, suggesting a decrease in bioavailability on this day. The M8 elimination rate was increased by concomitant administration of nonnucleoside reverse transcriptase inhibitors. A trough nelfinavir plasma concentration above 1 mg/liter was previously shown to improve the antiretroviral response. The Bayesian individual pharmacokinetic estimates suggested that the dosage should not be changed in pregnant women but may be doubled on the day of delivery.
Caspofungin Susceptibility in
Aspergillus
and Non-
Aspergillus
Molds: Inhibition of Glucan Synthase and Reduction of β-
d
-1,3 Glucan Levels in Culture
Authors: Kahn Jennifer Nielsen , Hsu Ming-Jo , Racine Fred , Giacobbe Robert , Motyl Mary
Published: May 2006

Caspofungin inhibits synthesis of β-
d
-1,3 glucan, essential to cell walls in
Candida
and
Aspergillus
spp., but activity against less common molds is largely uncharacterized. We demonstrate that caspofungin inhibits β-
d
-1,3 glucan synthesis and reduces in vitro growth of clinical isolates from the genera
Alternaria
,
Curvularia
,
Scedosporium
,
Acremonium
,
Bipolaris
, and
Trichoderma.
Mutant Prevention Concentrations of Levofloxacin Alone and in Combination with Azithromycin, Ceftazidime, Colistin (Polymyxin E), Meropenem, Piperacillin-Tazobactam, and Tobramycin against
Pseudomonas aeruginosa
Authors: Zhanel George G. , Mayer Matthew , Laing Nancy , Adam Heather J.
Published: May 2006

The mutant prevention concentrations (MPCs) of levofloxacin alone and in combination with ceftazidime, colistin (polymyxin E), meropenem, piperacillin-tazobactam, and tobramycin were established against
Pseudomonas aeruginosa.
Antibiotic combinations using levofloxacin with any antibiotic with individual activity against
P. aeruginosa
resulted in synergistic lowering (an at-least-fourfold reduction) of the isolate's MPC.
Assessing Resistance to the Echinocandin Antifungal Drug Caspofungin in
Candida albicans
by Profiling Mutations in
FKS1
Authors: Balashov Sergey V. , Park Steven , Perlin David S.
Published: May 2006

Resistance of clinical isolates of
Candida albicans
to the echinocandin drug caspofungin is slowly emerging and is linked to mutations in short conserved regions in the
FKS1
gene. The most prominent changes occurred at the serine 645 position in Fks1p with substitutions of proline, tyrosine, and phenylalanine. An allele-specific real-time PCR molecular-beacon assay was developed for rapid identification of drug resistance by targeting
FKS1
mutations. Mutations altering serine 645 were reliably identified in both heterozygous and homozygous states. The molecular-beacon assay was used to evaluate two large collections of spontaneous mutants from separate strains of
C. albicans
with resistance (MICs, >16 μg/ml) to caspofungin with the goal of understanding the relationship between
FKS1
mutations and echinocandin resistance. Of 85 resistant isolates recovered, all were identified with mutations in
FKS1
; 93% showed changes at Ser645, with 62% displaying a characteristic S645P substitution expressed as either a homozygous or a heterozygous mutation in
FKS1
. Two other prominent amino acid substitutions, S645Y and S645F, were found at frequencies of 22% and 8%, respectively. Three new mutations were also identified: T1922C, G1932T, and C1934G, encoding F641S, L644F, and S645C substitutions, respectively. One strain had the double amino acid substitution L644F and S645C. Allele-specific probes were combined in a multiplex assay for reliable screening of known
FKS1
mutations. These data support the importance of FKS1p substitutions in echinocandin resistance and demonstrate the feasibility of applying molecular screening for routine resistance assessment.
Adenosine Deaminase in Nucleoside Synthesis. A Review
Authors: Gupta Mukta , Nair Vasu
Published: May 2006

Adenosine deaminase (ADA) is an enzyme in the purine salvage pathway that catalyzes the deamination of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. This deamination is an important factor in limiting the usefulness of adenosine analogues in chemotherapy. However, the biocatalysis by ADA is also a useful transformation in enzymatic synthesis. In this review, examples from both the principal investigator's laboratory and from the literature, which depict the synthetic usefulness of this enzyme in deamination, dehalogenation, demethoxylation reactions and in diastereoisomeric resolution, are presented. It is not the intent of this review to comprehensively list all of the biotransformations induced by adenosine deaminase, but rather to present representative examples to highlight the powerful synthetic utility of this enzyme. A review with 72 references.
Nucleoside H-Phosphonates. XXI. Synthetic and 31P NMR Studies on the Preparation of Dinucleoside H-Phosphonoselenoates
Authors: Kullberg Martin , Bollmark Martin , Stawinski Jacek
Published: May 2006

Using 31P NMR spectroscopy as a tool, we investigated the condensation of H-phosphonoselenoate monoesters with a hydroxy component in the presence of various coupling agents. On this basis, synthetic protocols that eliminate or significantly suppress side reactions which might occur during the condensation in synthesis of H-phosphonoselenoate derivatives, have been developed. Absolute configuration of the produced dinucleoside H-phosphonoselenoates has been determined by stereochemical correlation analysis.
Studies on Oxidative Transformations of Dinucleoside H-Phosphonoselenoates
Authors: Bollmark Martin , Kullberg Martin , Stawinski Jacek
Published: May 2006

The utility of a new type of synthetic intermediates, H-phosphonoselenoate diesters, in the preparation of potentially biologically important nucleotide analogues containing the P-Se bond, was explored by converting dinucleoside H-phosphonoselenoates 1 into various phosphorus(V) derivatives under oxidative conditions.
7-Azaindolyl- and indolyl-functionalized starburst molecules with a 1,3,5-triazine or a benzene core  Syntheses and luminescence
Authors: Huang Wei-Hua , Jia Wen-Li , Wang Suning
Published: May 2006

The syntheses of several new 7-azaindolyl-, indolyl-, and 3-methylindolyl-functionalized starburst molecules that contain either a 1,3,5-triazine, a benzene, a 2,4,6-triphenyl-2,4,6-triazine, a 1,3,5-triphenylbenzene, a 2,4,6-tris(biphenyl)-1,3,5-triazine, or a 1,3,5-tris(biphenyl)benzene core have been achieved. The synthetic methods used for these new compounds involve mostly Ullmann condensation and Suzuki coupling reactions. The thermal properties of the new molecules have been found to be highly dependent on the molecular weight and the central core. Glass transition temperatures greater than 150 °C were observed for the large starburst molecules based on the 2,4,6-tris(biphenyl)-1,3,5-triazine or the 1,3,5-tris(biphenyl)benzene core. The new starburst molecules are luminescent in the violet-blue region in solution and in the solid state. The emission energy and the quantum efficiency were found to be highly dependent on the central core and the functional group. In general, the triazine-based molecules were found to have a smaller HOMOLUMO energy gap than the benzene-based analogues. The triphenyltriazine- or triphenylbenzene-based molecules were found to display a higher emission quantum efficiency than the large tris(biphenyl)triazine- or tris(biphenyl)benzene-based molecules.Key words: 7-azaindolyl, indolyl derivative, triazine and benzene cores, starburst molecule, blue luminescence.
HR-MAS NMR studies of 15N-labeled cells confirm the structure of the O-methyl phosphoramidate CPS modification in Campylobacter jejuni and provide insight into its biosynthesis
Authors: McNally David J , Lamoureux Marc , Li Jianjun , Kelly John , Brisson Jean-Robert , Szymanski Christine M , Jarrell Harold C
Published: May 2006

Because Campylobacter jejuni is the leading cause of bacterial food-borne gastroenteritis throughout the world, there is intense effort to determine the mechanisms of infectivity associated with this bacterium. Capsular polysaccharide (CPS) has been shown to be an important virulence factor for C. jejuni and a recent study that examined the 11168V26 strain identified several phase-variable CPS modifications including an unusual O-methyl phosphoramidate (MeOPN) group on C-3 of the GalfNAc residue. In this study, we examined the MeOPN group using homo- and hetero-nuclear high-resolution magic angle spinning (HR-MAS) NMR experiments of whole bacterial cells grown on 15NH4Cl-enriched media. 1H31P HSQC NMR experiments showed that the level of 15N labeling within the MeOPN reached 80%, and a large 1J(15N31P) scalar coupling provided direct evidence that confirmed the structure of the MeOPN as CH3OP(O)(NH2)(OR). Because 15N was also detected within the major outer membrane protein as well as the NAc and NGro groups of CPS, ammonium was concluded to be an important building block used in the synthesis of amino acids and glycan structures in C. jejuni. HR-MAS NMR studies of 15N-labeled cells revealed an unanticipated level of complexity as multiple MeOPN signals were observed within 1H-31P HSQC spectra for the 11168V26 and 11168H strains. While some signals originated from the MeOPN at C-3 of GalfNAc, others were attributed to a novel MeOPN located on D-glycero-α-L-gluco-heptopyranose. Together, these HR-MAS NMR findings shed light on nitrogen metabolism in C. jejuni, confirm the chemical structure of the MeOPN, and demonstrate that the modification occurs on both furanose and pyranose CPS sugars for this bacterium.Key words: Campylobacter jejuni, capsular polysaccharide, HR-MAS NMR, isotope labeling, phosphoramidate.
Synthesis of the tetrasaccharide repeat unit of the O-antigen polysaccharide from Escherichia coli O77 employing the 2′-carboxybenzyl glycoside
Authors: Lee Bo Ram , Jeon Joo Mi , Jung Jae Hyuk , Jeon Heung Bae , Kim Kwan Soo
Published: May 2006

The synthesis of the suitably protected form (1) of the tetrasaccharide repeat unit, →2)-α-D-Manp-(1→2)-β-D-Manp-(1→3)-α-D-GlcpNAc-(1→6)-α-D-Manp-(1→ (A), of the O-antigen polysaccharide of the lipopolysaccharide from Escherichia coli O77 has been accomplished by latentactive glycosylation employing the 2′-carboxybenzyl (CB) gly coside method. In addition to previously used latent glycosyl donors, 2′-(benzyloxycarbonyl)benzyl (BCB) glycosides, new latent glycosyl donors, 2'-(allyloxycarbonyl)benzyl (ACB) glycosides, have been introduced as a direct precursor for the active CB glycosides. We also demonstrate that 4,6-O-benzylidene-2-azido-2-deoxy-α-D-mannopyranoside (7) has been readily prepared from D-glucosamine in good yield.Key words: Escherichia coli O77, glycosylation, 2′-carboxybenzyl (CB) glycosides, 2′-(allyloxycarbonyl)benzyl (ACB) glycosides, glycosyl donor.
Synthesis of 8-homocastanospermine
Authors: Paśniczek Konrad , Socha Dariusz , Jurczak Margarita , Solecka Jolanta , Chmielewski Marek
Published: May 2006

The 1,3-dipolar cycloaddition of a five-membered cyclic nitrone derived from malic acid (4) and unsaturated D-threo-hexaldonolactone (1) leads to a single adduct 6, which can be transformed into the 8-homocastanospermine (13) via a sequence involving rearrangement of the six-membered lactone ring into the five-membered one, removal of the terminal carbon atom from the sugar chain, cleavage of the NO bond, and the intramolecular alkylation of the nitrogen atom. The iminosugar (13) does not show any interesting inhibitory activity towards α- and β-glucosidases.Key words: iminosugars, homocastanospermine, nitrones, aldono-1,5-lactone, 1,3-dipolar cycloaddition, glucosidases.
Towards C-2 symmetrical macrocyles with an incorporated sucrose unit
Authors: Jarosz Sławomir , Listkowski Arkadiusz
Published: May 2006

The first C2 symmetrical macrocyclic receptor containing two sucrose molecules has been prepared, albeit in low yield, by reaction of hexa-O-benzyl-6′-O-acroyl-6-O-allylsucrose in the presence of a second generation Grubbs catalyst (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ruthenium alkylidene complex). Highly selective protection of the 6′-OH group in 1′,2,3,3′,4,4′-hexa-O-benzylsucrose was a key step in the preparation of the precursor used under ring closing metathesis (RCM) conditions.Key words: sucrose, macrocyclic receptors, metathesis, regioselective transformations.
A concise synthesis of α-D-ribofuranosyl alkylphosphonates  Putative substrate intermediates for the carbonphosphorous lyase system
Authors: Luo Yan , Zechel David L
Published: May 2006

Carbonphosphorous lyase is a multienzyme system found in many species of bacteria that is distinguished by its ability to hydrolyze a broad array of unactivated alkylphosphonates. α-D-Ribofuranosyl alkylphosphonates are potential metabolic intermediates generated by the carbonphosphorous lyase pathway. Here we describe a facile synthesis of α-D-ribofuranosyl alkylphosphonates using β-D-ribofuranosyl trichloracetimidate as a glycosyl donor.Key words: carbonphosphorous lyase, phn operon, phnN, phosphonates, glycosyl trichloroacetimidate donor, α-D-ribofuranosyl ethylphosphonate.
Ab initio DFT calculations of the configurational and conformational preferences of 2-phenylsulfinylcyclohexanones  Evidence for "exo-anomeric" interactions
Authors: Trapp Melissa L , Wojcik John F , Zajac, Jr. Walter W , Pinto B Mario
Published: May 2006

The conformational analysis of 2-phenylsulfinylcyclohexanone by ab initio density functional calculations is described. Six conformations corresponding to axial/equatorial isomers and rotation about the exocyclic C2S bond in each of the RR or RS diastereomers were calculated and the results were examined in terms of relative energies, electrostatic interactions, orbital interactions, and geometrical variations. The global minimum conformation was the RS isomer that positioned the phenylsulfinyl moiety in an equatorial orientation and the sulfinyl oxygen in an anti orientation with respect to the carbonyl carbon atom. Of the other three low energy conformations, only one had a gauche arrangement of these atoms, and only in one of the four lower energy conformations was evidence found for a S-O()···C(+)-O electrostatic interaction. In contrast, the results were consistent with the operation of nS → [Formula: see text] stabilizing orbital interactions. Further support for this hypothesis was obtained from the increased C=O bond lengths in these four conformations relative to the other conformations, and by the torsional angle distortion away from ideal geometry, presumably to maximize the stabilizing orbital interaction. We propose that this conformational preference is a manifestation of a generalized exo-anomeric effect. The longer C2S bond in the axial isomers was also interpreted in terms of a stabilizing πC=O → [Formula: see text] interaction, analogous to an endo-anomeric interaction. Comparison of the computational results to available experimental data on the conformational equilibrium of each diastereomer in solution suggests which conformers are present in each of the equilibria. The available data for the solid state indicate that the RR and RS isomers both crystallize in high energy conformations, stabilized by intermolecular interactions.Key words: 2-phenylsulfinylcyclohexanones, configurational isomers, conformational preferences, DFT calculations, exo-anomeric effect.
Synthesis of 6-(alkoxymethyl)- and 6-(alkylsulfanylmethyl)furo[2,3-d]pyrimidin-2(3H)-one analogues
Authors: Janeba Zlatko , Maklad Noha , Robins Morris J
Published: May 2006

Treatment of 6-(hydroxymethyl)furo[2,3-d]pyrimidin-2(3H)-one (2) with 1-iodoalkanes and potassium carbonate resulted in predominant formation of N3 (and minor amounts of O2) alkylated regioisomers. Treatment of the 3-alkyl products (3) with thionyl chloride gave highly reactive 6-chloromethyl intermediates (5). Direct solvolysis of 5 in alcohol solutions (~50 °C) produced 3-alkyl-6-(alkoxymethyl)furopyrimidin-2(3H)-ones (6), whereas extensive decomposition of 5 occurred with added base promoters. Sonication of 5 with sodium thioacetate in acetonitrile gave the air-stable 6-(alkylsulfanylmethyl) intermediates (7), which were subjected to deacetylation (methanolic sodium methoxide) and in situ alkylation to give 3-alkyl-6-(alkylsulfanylmethyl)furo[2,3-d]pyrimidin-2(3H)-ones (8). Lipophilic derivatives of furo[2,3-d]pyrimidin-2(3H)-one are of interest as potential inhibitors of viral penetration of cells.Key words: furo[2,3-d]pyrimidin-2(3H)-ones, alkyl, ether and thioether derivatives of furo[2,3-d]pyrimidin-2(3H)-one.