bluuebunny/crossref_metadata_2025 huggingface dataset:
The Genomic Sequence of the Accidental Pathogen
Legionella pneumophila
Authors: Chien Minchen , Morozova Irina , Shi Shundi , Sheng Huitao , Chen Jing , Gomez Shawn M. , Asamani Gifty , Hill Kendra , Nuara John , Feder Marc , Rineer Justin , Greenberg Joseph J. , Steshenko Valeria , Park Samantha H. , Zhao Baohui , Teplitskaya Elita , Edwards John R. , Pampou Sergey , Georghiou Anthi , Chou I.-Chun , Iannuccilli William , Ulz Michael E. , Kim Dae H. , Geringer-Sameth Alex , Goldsberry Curtis , Morozov Pavel , Fischer Stuart G. , Segal Gil , Qu Xiaoyan , Rzhetsky Andrey , Zhang Peisen , Cayanis Eftihia , De Jong Pieter J. , Ju Jingyue , Kalachikov Sergey , Shuman Howard A. , Russo James J.
Published: September 2004

We present the genomic sequence of
Legionella pneumophila
, the bacterial agent of Legionnaires' disease, a potentially fatal pneumonia acquired from aerosolized contaminated fresh water. The genome includes a 45âkilobase pair element that can exist in chromosomal and episomal forms, selective expansions of important gene families, genes for unexpected metabolic pathways, and previously unknown candidate virulence determinants. We highlight the genes that may account for
Legionella
's ability to survive in protozoa, mammalian macrophages, and inhospitable environmental niches and that may define new therapeutic targets.
Fractionation of the Platinum-Group Elements During Mantle Melting
Authors: Bockrath Conny , Ballhaus Chris , Holzheid Astrid
Published: September 2004

Experiments in sulfide-silicate systems demonstrate that two sulfide phases are stable in the asthenospheric upper mantle: a crystalline osmium-iridiumruthenium–enriched monosulfide and a rhodium-platinum-palladium–enriched sulfide melt. During silicate melt segregation, monosulfide stays in the solid residue, dominating the noble metal spectrum of residual mantle. The sulfide melt is entrained as immiscible droplets in the segregating silicate melt, defining the noble metal inventory of the basaltic component.
A Triassic Aquatic Protorosaur with an Extremely Long Neck
Authors: Li Chun , Rieppel Olivier , LaBarbera Michael C.
Published: September 2004

By Middle Triassic time, a number of reptile lineages had diversified in shallow epicontinental seas and intraplatform basins along the margins of parts of Pangea, including the giraffe-necked protorosaurid reptile
Tanystropheus
from the Western Tethys (Europe and the Middle East), which grew to ~5 to 6 m long. Here we report another long-necked fossil,
Dinocephalosaurus
, from southwestern China, recently collected in Middle Triassic marine deposits ~230 million years old. This taxon represents unambiguous evidence for a fully aquatic protorosaur. Its extremely elongated neck is explained as an adaptation for aquatic life, perhaps for an increase in feeding efficiency.
Distance Communication Transfer of HIV Prevention Interventions to Service Providers
Authors: Kelly Jeffrey A. , Somlai Anton M. , Benotsch Eric G. , McAuliffe Timothy L. , Amirkhanian Yuri A. , Brown Kevin D. , Stevenson L. Yvonne , Fernandez M. Isa , Sitzler Cheryl , Gore-Felton Cheryl , Pinkerton Steven D. , Weinhardt Lance S. , Opgenorth Karen M.
Published: September 2004

Most acquired immunodeficiency syndrome (AIDS) service providers are in countries with little access to scientific developments relevant to their programs. It is critical to transfer advances from the scientific arena to service providers on a global scale. Human immunodeficiency virus (HIV) prevention organizations in 78 countries were randomized to receive either a control condition or a technology transfer condition with an interactive distance learning computer training curriculum and individualized distance consultation. Of 42 nongovernmental organizations in the technology transfer condition, 29 adopted the science-based program in their communities or trained other agencies to also use it. Advanced communication technologies can create a cost-effective infrastructure to disseminate new intervention models to service providers worldwide.
Ice Flow Direction Change in Interior West Antarctica
Authors: Siegert Martin J. , Welch Brian , Morse David , Vieli Andreas , Blankenship Donald D. , Joughin Ian , King Edward C. , Vieli Gwendolyn J.-M. C. Leysinger , Payne Antony J. , Jacobel Robert
Published: September 2004

Upstream of Byrd Station (West Antarctica), ice-penetrating radar data reveal a distinctive fold structure within the ice, in which isochronous layers are unusually deep. The fold has an axis more than 50 kilometers long, which is aligned up to 45° to the ice flow direction. Although explanations for the fold's formation under the present flow are problematic, it can be explained if flow was parallel to the fold axis ∼1500 years ago. This flow change may be associated with ice stream alterations nearer the margin. If this is true, central West Antarctica may respond to future alterations more than previously thought.
Amazonian Ecology: Tributaries Enhance the Diversity of Electric Fishes
Authors: Fernandes Cristina Cox , Podos Jeffrey , Lundberg John G.
Published: September 2004

Neotropical rivers support a diverse array of endemic taxa, including electric fishes of the order Gymnotiformes. A comprehensive survey of the main channels of the Amazon River and its major tributaries (>2000-kilometer transect) yielded 43 electric fish species. Biogeographical analyses suggest that local mainstem electric fish diversity is enhanced by tributaries. Mainstem species richness tends to increase downstream of tributary confluences, and species composition is most similar between tributaries and adjacent downstream mainstem locations. These findings support a “nodal” or heterogeneous model of riverine community organization across a particularly extensive and diverse geographical region.
Solar Wind-Induced Atmospheric Erosion at Mars: First Results from ASPERA-3 on Mars Express
Authors: Lundin R. , Barabash S. , Andersson H. , Holmström M. , Grigoriev A. , Yamauchi M. , Sauvaud J.-A. , Fedorov A. , Budnik E. , Thocaven J.-J. , Winningham D. , Frahm R. , Scherrer J. , Sharber J. , Asamura K. , Hayakawa H. , Coates A. , Linder D. R. , Curtis C. , Hsieh K. C. , Sandel B. R. , Grande M. , Carter M. , Reading D. H. , Koskinen H. , Kallio E. , Riihela P. , Schmidt W. , Säles T. , Kozyra J. , Krupp N. , Woch J. , Luhmann J. , McKenna-Lawler S. , Cerulli-Irelli R. , Orsini S. , Maggi M. , Mura A. , Milillo A. , Roelof E. , Williams D. , Livi S. , Brandt P. , Wurz P. , Bochsler P.
Published: September 2004

The Analyzer of Space Plasma and Energetic Atoms (ASPERA) on board the Mars Express spacecraft found that solar wind plasma and accelerated ionospheric ions may be observed all the way down to the Mars Express pericenter of 270 kilometers above the dayside planetary surface. This is very deep in the ionosphere, implying direct exposure of the martian topside atmosphere to solar wind plasma forcing. The low-altitude penetration of solar wind plasma and the energization of ionospheric plasma may be due to solar wind irregularities or perturbations, to magnetic anomalies at Mars, or both.
Self-Organized Patchiness and Catastrophic Shifts in Ecosystems
Authors: Rietkerk Max , Dekker Stefan C. , de Ruiter Peter C. , van de Koppel Johan
Published: September 2004

Unexpected sudden catastrophic shifts may occur in ecosystems, with concomitant losses or gains of ecological and economic resources. Such shifts have been theoretically attributed to positive feedback and bistability of ecosystem states. However, verifications and predictive power with respect to catastrophic responses to a changing environment are lacking for spatially extensive ecosystems. This situation impedes management and recovery strategies for such ecosystems. Here, we review recent studies on various ecosystems that link self-organized patchiness to catastrophic shifts between ecosystem states.
Recycling Endosomes Supply AMPA Receptors for LTP
Authors: Park Mikyoung , Penick Esther C. , Edwards Jeffrey G. , Kauer Julie A. , Ehlers Michael D.
Published: September 2004

Long-term potentiation (LTP) of synaptic strength, the most established cellular model of information storage in the brain, is expressed by an increase in the number of postsynaptic AMPA receptors. However, the source of AMPA receptors mobilized during LTP is unknown. We report that AMPA receptors are transported from recycling endosomes to the plasma membrane for LTP. Stimuli that triggered LTP promoted not only AMPA receptor insertion but also generalized recycling of cargo and membrane from endocytic compartments. Thus, recycling endosomes supply AMPA receptors for LTP and provide a mechanistic link between synaptic potentiation and membrane remodeling during synapse modification.
Visualization of Dislocation Dynamics in Colloidal Crystals
Authors: Schall Peter , Cohen Itai , Weitz David A. , Spaepen Frans
Published: September 2004

The dominant mechanism for creating large irreversible strain in atomic crystals is the motion of dislocations, a class of line defects in the crystalline lattice. Here we show that the motion of dislocations can also be observed in strained colloidal crystals, allowing detailed investigation of their topology and propagation. We describe a laser diffraction microscopy setup used to study the growth and structure of misfit dislocations in colloidal crystalline films. Complementary microscopic information at the single-particle level is obtained with a laser scanning confocal microscope. The combination of these two techniques enables us to study dislocations over a range of length scales, allowing us to determine important parameters of misfit dislocations such as critical film thickness, dislocation density, Burgers vector, and lattice resistance to dislocation motion. We identify the observed dislocations as Shockley partials that bound stacking faults of vanishing energy. Remarkably, we find that even on the scale of a few lattice vectors, the dislocation behavior is well described by the continuum approach commonly used to describe dislocations in atomic crystals.
A Checkered History
Authors: Jiggins Chris D.
Published: September 2004

On the Wings of Checkerspots
A Model System for Population Biology. Paul R. Ehrlich and Ilkka Hanski, Eds. Oxford University Press, New York, 2004. 391 pp. $64.50, £40. ISBN 0-19-515827-X.

The contributors synthesize results from the editors' long-term research projects in the Bay Area and Finland, which have made important contributions to our understanding of the ecological and evolutionary dynamics of populations and to conservation biology.
Lobster Tales
Authors: Sternberg Esther
Published: September 2004

The Secret Life of Lobsters
How Fishermen and Scientists Are Unraveling the Mysteries of Our Favorite Crustacean. by Trevor Corson. HarperCollins, New York, 2004. 299 pp. $24.95, C$34.95. ISBN 0-06-055558-0.

The author offers a fascinating and informative account of the activities of lobsters, the lobstermen who catch them, and the researchers who study them along the New England coast.
Telithromycin Treatment of Chronic
Chlamydia pneumoniae
Infection in C57BL/6J mice
Authors: Törmäkangas Liisa , Alakärppä Hannu , Bem David Denise , Leinonen Maija , Saikku Pekka
Published: September 2004

Chronic
Chlamydia pneumoniae
infections have been associated with atherosclerosis, but clear knowledge about how these infections should be treated is lacking. We studied the effect of a new ketolide antibiotic, telithromycin, on chronic
C. pneumoniae
lung infection. Female C57BL/6J mice on a 0.2% cholesterol diet were inoculated intranasally with
C. pneumoniae
either two or three times every fourth week. Telithromycin was given to the mice subcutaneously at 75 mg/kg of body weight once daily for 5 or 10 days, starting at 3 days after the last inoculation. Samples were taken at 4 and 12 weeks after the last inoculation. The presence of
C. pneumoniae
DNA in lung tissue was demonstrated by PCR and the detection of lipid accumulation in the aortic sinus by Oil-Red-O staining.
C. pneumoniae
DNA positivity and inflammatory reactions in the lung tissue of the mice inoculated twice were significantly affected by treatment after both inoculations or only after the second inoculation at 12 weeks. Intimal lipid accumulation in the aortic sinus was also slightly but significantly less abundant in the mice treated after both inoculations compared to the levels in those treated only after the second inoculation for 10 days (geometric means, 823 and 4,324 μm
2
, respectively;
P
= 0.033). No differences between the infected, untreated controls and the group inoculated three times and treated for 5 days were seen. We conclude that telithromycin is effective in preventing the development of chronic
C. pneumoniae
infection and intimal lipid accumulation in C56BL/6J mice when the treatment is given after each inoculation.
Multilayer Polyelectrolyte Films Functionalized by Insertion of Defensin: a New Approach to Protection of Implants from Bacterial Colonization
Authors: Etienne O. , Picart C. , Taddei C. , Haikel Y. , Dimarcq J. L. , Schaaf P. , Voegel J. C. , Ogier J. A. , Egles C.
Published: September 2004

Infection of implanted materials by bacteria constitutes one of the most serious complications following prosthetic surgery. In the present study, we developed a new strategy based on the insertion of an antimicrobial peptide (defensin from
Anopheles gambiae
mosquitoes) into polyelectrolyte multilayer films built by the alternate deposition of polyanions and polycations. Quartz crystal microbalance and streaming potential measurements were used to follow step by step the construction of the multilayer films and embedding of the defensin within the films. Antimicrobial assays were performed with two strains:
Micrococcus luteus
(a gram-positive bacterium) and
Escherichia coli
D22 (a gram-negative bacterium). The inhibition of
E. coli
D22 growth at the surface of defensin-functionalized films was found to be 98% when 10 antimicrobial peptide layers were inserted in the film architecture. Noticeably, the biofunctionalization could be achieved only when positively charged poly(
l
-lysine) was the outermost layer of the film. On the basis of the results of bacterial adhesion experiments observed by confocal or electron microscopy, these observations could result from the close interaction of the bacteria with the positively charged ends of the films, which allows defensin to interact with the bacterial membrane structure. These results open new possibilities for the use of such easily built and functionalized architectures onto any type of implantable biomaterial. The modified surfaces are active against microbial infection and represent a novel means of local host protection.
Pharmacodynamic Functions: a Multiparameter Approach to the Design of Antibiotic Treatment Regimens
Authors: Regoes Roland R. , Wiuff Camilla , Zappala Renata M. , Garner Kim N. , Baquero Fernando , Levin Bruce R.
Published: September 2004

There is a complex quantitative relationship between the concentrations of antibiotics and the growth and death rates of bacteria. Despite this complexity, in most cases only a single pharmacodynamic parameter, the MIC of the drug, is employed for the rational development of antibiotic treatment regimens. In this report, we use a mathematical model based on a Hill function—which we call the pharmacodynamic function and which is related to previously publishedEmaxmodels—to describe the relationship between the bacterial net growth rates and the concentrations of antibiotics of five different classes: ampicillin, ciprofloxacin, tetracycline, streptomycin, and rifampin. UsingEscherichia coliO18:K1:H7, we illustrate how precise estimates of the four parameters of the pharmacodynamic function can be obtained from in vitro time-kill data. We show that, in addition to their respective MICs, these antibiotics differ in the values of the other pharmacodynamic parameters. Using a computer simulation of antibiotic treatment in vivo, we demonstrate that, as a consequence of differences in pharmacodynamic parameters, such as the steepness of the Hill function and the minimum bacterial net growth rate attained at high antibiotic concentrations, there can be profound differences in the microbiological efficacy of antibiotics with identical MICs. We discuss the clinical implications and limitations of these results.
Ketolide Antimicrobial Activity Persists after Disruption of Interactions with Domain II of 23S rRNA
Authors: Novotny Guy W. , Jakobsen Lene , Andersen Niels M. , Poehlsgaard Jacob , Douthwaite Stephen
Published: September 2004

Ketolides are the latest derivatives developed from the macrolide erythromycin to improve antimicrobial activity. All macrolides and ketolides bind to the 50S ribosomal subunit, where they come into contact with adenosine 2058 (A2058) within domain V of the 23S rRNA and block protein synthesis. An additional interaction at nucleotide A752 in the rRNA domain II is made via the synthetic carbamate-alkyl-aryl substituent in the ketolides HMR3647 (telithromycin) and HMR3004, and this interaction contributes to their improved activities. Only a few macrolides, including tylosin, come into contact with domain II of the rRNA and do so via interactions with nucleotides G748 and A752. We have disrupted these macrolide-ketolide interaction sites in the rRNA to assess their relative importance for binding. Base substitutions at A752 were shown to confer low levels of resistance to telithromycin but not to HMR3004, while deletion of A752 confers low levels of resistance to both ketolides. Mutations at position 748 confer no resistance. Substitution of guanine at A2058 gives rise to the MLS
B
(macrolide, lincosamide, and streptogramin B) phenotype, which confers resistance to all the drugs. However, resistance to ketolides was abolished when the mutation at position 2058 was combined with a mutation in domain II of the same rRNA. In contrast, the same dual mutations in rRNAs conferred enhanced resistance to tylosin. Our results show that the domain II interactions of telithromycin and HMR3004 differ from each other and from those of tylosin. The data provide no indication that mutations within domain II, either alone or in combination with an A2058 mutation, can confer significant levels of telithromycin resistance.
Antimicrobial Evaluation of Nocathiacins, a Thiazole Peptide Class of Antibiotics
Authors: Pucci Michael J. , Bronson Joanne J. , Barrett John F. , DenBleyker Kenneth L. , Discotto Linda F. , Fung-Tomc Joan C. , Ueda Yasutsugu
Published: September 2004

Nocathiacins are cyclic thiazolyl peptides with inhibitory activity against gram-positive bacteria. BMS-249524 (nocathiacin I), identified from screening a library of compounds against a multiply antibiotic-resistant
Enterococcus faecium
strain, was used as a lead chemotype to obtain additional structurally related compounds. The MIC assay results of BMS-249524 and two more water-soluble derivatives, BMS-411886 and BMS-461996, revealed potent in vitro activities against a variety of gram-positive pathogens including methicillin-resistant
Staphylococcus aureus
, penicillin-resistant
Streptococcus pneumoniae
, vancomycin intermediate-resistant
S. aureus
, vancomycin-resistant enterococci,
Mycobacterium tuberculosis
and
Mycobacterium avium
. Analysis of killing kinetics revealed that these compounds are bactericidal for
S. aureus
with at least a 3-log
10
reduction of bacterial growth within 6 h of exposure to four times the MICs. Nocathiacin-resistant mutants were characterized by DNA sequence analyses. The mutations mapped to the
rplK
gene encoding the L11 ribosomal protein in the 50S subunit in a region previously shown to be involved in the binding of related thiazolyl peptide antibiotics. These compounds demonstrated potential for further development as a new class of antibacterial agents with activity against key antibiotic-resistant gram-positive bacterial pathogens.
Combinations of Adefovir with Nucleoside Analogs Produce Additive Antiviral Effects against Hepatitis B Virus In Vitro
Authors: Delaney William E. , Yang Huiling , Miller Michael D. , Gibbs Craig S. , Xiong Shelly
Published: September 2004

Combination therapies may be required for long-term management of some patients chronically infected with hepatitis B virus (HBV). Adefovir is a nucleotide analog that has similar activity against wild-type and lamivudine-resistant HBV. In contrast to lamivudine, clinical resistance to the prodrug adefovir dipivoxil emerges infrequently. Based on its clinical efficacy and low frequency of resistance, adefovir dipivoxil may form an important component of combination regimens. We therefore investigated the in vitro antiviral efficacy of combinations of adefovir with other nucleoside analogs (lamivudine, entecavir, emtricitabine [FTC],and telbivudine [L-dT]) and the nucleotide analog tenofovir. Using a novel stable cell line that expresses high levels of wild-type HBV, we assayed the antiviral activity of each drug alone and in combination with adefovir. All two-drug combinations resulted in greater antiviral effects than treatments with single agents and could be characterized as additive by the Bliss independence model. Analysis using the Loewe additivity model indicated that adefovir exerted additive antiviral effects when combined with lamivudine, FTC, or L-dT and moderately synergistic effects when combined with entecavir or tenofovir. There was no evidence of cytotoxicity with any of the drugs when used alone or in combination at the tested doses.
In Vitro Activities of 2,4-Diaminoquinazoline and 2,4-Diaminopteridine Derivatives against
Plasmodium falciparum
Authors: Ommeh Sheila , Nduati Eunice , Mberu Eddy , Kokwaro Gilbert , Marsh Kevin , Rosowsky Andre , Nzila Alexis
Published: September 2004

The activities of 28 6-substituted 2,4-diaminoquinazolines, 2,4-diamino-5,6,7,8-tetrahydroquinazolines, and 2,4-diaminopteridines against
Plasmodium falciparum
were tested. The 50% inhibitory concentrations (IC
50
s) of six compounds were <50 nM, and the most potent compound was 2,4-diamino-5-chloro-6-[
N
-(2,5-dimethoxybenzyl)amino]quinazoline (compound 1), with an IC
50
of 9 nM. The activity of compound 1 was potentiated by the dihydropteroate synthase inhibitor dapsone, an indication that these compounds are inhibitors of dihydrofolate reductase. Further studies are warranted to assess the therapeutic potential of this combination in vivo.
Antifungal Therapy of Murine
Aspergillus terreus
Infection
Authors: Graybill John R. , Hernandez Steve , Bocanegra Rosie , Najvar Laura K.
Published: September 2004

Aspergillus terreus
is a species which is being seen increasingly frequently and which is highly resistant to amphotericin B in vitro and clinically. We evaluated amphotericin B, caspofungin, and posaconazole in a murine model of acute invasive aspergillosis. Caspofungin and posaconazole both appeared beneficial and may be reasonable treatment alternatives for infection with
A. terreus
.
Epidemiology and Clinical Features of Bloodstream Infections Caused by AmpC-Type-β-Lactamase-Producing
Klebsiella pneumoniae
Authors: Pai Hyunjoo , Kang Cheol-In , Byeon Jeong-Hum , Lee Ki-Deok , Park Wan Beom , Kim Hong-Bin , Kim Eui-Chong , Oh Myoung-don , Choe Kang-Won
Published: September 2004

Cases of bacteremia caused by AmpC-type-β-lactamase-producing
Klebsiella pneumoniae
isolates were retrospectively studied to determine the epidemiologic features and clinical outcomes of bloodstream infections. Among 389 blood isolates recovered from 1998 to 2002, 65 isolates (16.7%) were found to be extended-spectrum β-lactamase (ESBL) or AmpC β-lactamase producers. The β-lactamases from 61 of the 65 isolates were characterized; 28 of 61 isolates produced AmpC-type enzymes (14 isolates each produced DHA-1 and CMY-1-like enzymes), 32 isolates produced TEM or SHV-related ESBLs, and 1 isolate produced a CTX-M-14-like enzyme. To compare the clinical features and outcomes of bloodstream infections caused by AmpC producers with those caused by TEM- or SHV-related ESBL producers, 27 patients infected with isolates producing AmpC-type enzymes (AmpC group) and 25 patients infected with isolates producing TEM- or SHV-related enzymes (ESBL group) were analyzed. There was no significant difference between the AmpC and the ESBL groups in terms of risk factors. When the initial response was assessed at 72 h after antimicrobial therapy, the treatment failure rate for the AmpC group was 51.9% (14 of 27 patients) and the 7- and 30-day mortality rates were 14.8 and 29.6%, respectively, which were similar to those for the ESBL group. When the mortality rate for the patients who received extended-spectrum cephalosporins as definitive treatment was assessed, all four patients in the DHA-1 group and one of three patients in the CMY-1-like group died. In summary, the prevalence of AmpC enzyme-producing
K. pneumoniae
was high at the Seoul National University Hospital, and the clinical features and outcomes for the patients infected with AmpC-producing organisms were similar to those for the patients infected with TEM- or SHV-related ESBL producers.
AcrAB-TolC Directs Efflux-Mediated Multidrug Resistance in
Salmonella enterica
Serovar Typhimurium DT104
Authors: Baucheron Sylvie , Tyler Shaun , Boyd David , Mulvey Michael R. , Chaslus-Dancla Elisabeth , Cloeckaert Axel
Published: September 2004

Multidrug-resistant
Salmonella enterica
serovar Typhimurium definitive phage type 104 (DT104) strains harbor a genomic island, called
Salmonella
genomic island 1 (SGI1), which contains an antibiotic resistance gene cluster conferring resistance to ampicillin, chloramphenicol, florfenicol, streptomycin, sulfonamides, and tetracyclines. They may be additionally resistant to quinolones. Among the antibiotic resistance genes there are two, i.e.,
floR
and
tet
(G), which code for efflux pumps of the major facilitator superfamily with 12 transmembrane segments that confer resistance to chloramphenicol-florfenicol and the tetracyclines, respectively. In the present study we determined, by constructing
acrB
and
tolC
mutants, the role of the AcrAB-TolC multidrug efflux system in the multidrug resistance of several DT104 strains displaying additional quinolone resistance or not displaying quinolone resistance. This study shows that the quinolone resistance and the decreased fluoroquinolone susceptibilities of the strains are highly dependent on the AcrAB-TolC efflux system and that single mutations in the quinolone resistance-determining region of
gyrA
are of little relevance in mediating this resistance. Overproduction of the AcrAB efflux pump, as determined by Western blotting with an anti-AcrA polyclonal antibody, appeared to be the major mechanism of resistance to quinolones. Moreover, chloramphenicol-florfenicol and tetracycline resistance also appeared to be highly dependent on the presence of AcrAB-TolC, since the introduction of mutations in the respective
acrB
and
tolC
genes resulted in a susceptible or intermediate resistance phenotype, according to clinical MIC breakpoints, despite the presence of the FloR and Tet(G) efflux pumps. Resistance to other antibiotics, ampicillin, streptomycin, and sulfonamides, was not affected in the
acrB
and
tolC
mutants of DT104 strains harboring SGI1. Therefore, AcrAB-TolC appears to direct efflux-mediated resistance to quinolones, chloramphenicol-florfenicol, and tetracyclines in multidrug-resistant
S. enterica
serovar Typhimurium DT104 strains.
Acquired Bacitracin Resistance in
Enterococcus faecalis
Is Mediated by an ABC Transporter and a Novel Regulatory Protein, BcrR
Authors: Manson Janet M. , Keis Stefanie , Smith John M. B. , Cook Gregory M.
Published: September 2004

Bacitracin resistance (bacitracin MIC, ≥256 μg ml
−1
) has been reported in
Enterococcus faecalis
, and in the present study we report on the genetic basis for this resistance. Mutagenesis was carried out with transposon Tn
917
to select for
E. faecalis
mutants with decreased resistance to bacitracin. Two bacitracin-sensitive mutants (MICs, 32 μg ml
−1
) were obtained and Tn
917
insertions were mapped to genes designated
bcrA
and
bcrB
. The amino acid sequences of BcrA (ATP-binding domain) and BrcB (membrane-spanning domain) are predicted to constitute a homodimeric ATP-binding cassette (ABC) transporter, the function of which is essential for bacitracin resistance in
E. faecalis
. The
bcrA
and
bcrB
genes were organized in an operon with a third gene,
bcrD
, that had homology to undecaprenol kinases. Northern analysis demonstrated that
bcrA
,
bcrB
, and
bcrD
were transcribed as a polycistronic message that was induced by increasing concentrations of bacitracin but not by other cell wall-active antimicrobials (e.g., vancomycin). Upstream of the
bcrABD
operon was a putative regulatory gene,
bcrR
. The
bcrR
gene was expressed constitutively, and deletion of
bcrR
resulted in a bacitracin-sensitive phenotype. No
bcrABD
expression was observed in a
bcrR
mutant, suggesting that BcrR is an activator of genes essential for bacitracin resistance (i.e.,
bcrABD
). The bacitracin resistance genes were found to be located on a plasmid that transferred at a high frequency to
E. faecalis
strain JH2-2. This report represents the first description of genes that are essential for acquired bacitracin resistance in
E. faecalis
.
Cell Wall Composition and Decreased Autolytic Activity and Lysostaphin Susceptibility of Glycopeptide-Intermediate
Staphylococcus aureus
Authors: Koehl Jennifer L. , Muthaiyan Arunachalam , Jayaswal Radheshyam K. , Ehlert Kerstin , Labischinski Harald , Wilkinson Brian J.
Published: September 2004

The cell wall composition and autolytic properties of passage-selected glycopeptide-intermediate
Staphylococcus aureus
(GISA) isolates and their parent strains were studied in order to investigate the mechanism of decreased vancomycin susceptibility. GISA had relatively modest changes in peptidoglycan composition involving peptidoglycan interpeptide bridges and somewhat decreased cross-linking compared to that of parent strains. The cell wall phosphorus content of GISA strains was lower than that of susceptible parent strains, indicating somewhat lower wall teichoic acid levels in the GISA strains. Similar to whole cells, isolated crude cell walls retaining autolytic activity of GISA had drastically reduced autolytic activity compared to that of parent strains, and this arose early in the development of the GISA phenotype. This was due to an alteration in the autolytic enzymes of GISA as revealed by normal susceptibility of GISA-purified cell walls to parental strain autolysin extract and lower activity and altered peptidoglycan hydrolase activity profiles in GISA autolysin extracts compared to those of parent strains. Northern blot analysis indicated that expression of
atl
, the major autolysin gene, was significantly downregulated in a GISA strain compared to that of its parent strain. In contrast to whole cells, which showed decreased lysostaphin susceptibility, purified cell walls of GISA showed increased susceptibility to lysostaphin. We suggest that in our GISA strains, decreased autolytic activity is involved in the tolerance of vancomycin and the activities of endogenous autolysins are important in conferring sensitivity to lysostaphin on whole cells.
Complete Nucleotide Sequence of a 92-Kilobase Plasmid Harboring the CTX-M-15 Extended-Spectrum Beta-Lactamase Involved in an Outbreak in Long-Term-Care Facilities in Toronto, Canada
Authors: Boyd David A. , Tyler Shaun , Christianson Sara , McGeer Allison , Muller Matthew P. , Willey Barbara M. , Bryce Elizabeth , Gardam Michael , Nordmann Patrice , Mulvey Michael R.
Published: September 2004

A major outbreak involving an
Escherichia coli
strain that was resistant to expanded-spectrum cephalosporins occurred in Toronto and surrounding regions in 2000 to 2002. We report the complete sequence of a plasmid, pC15-1a, that was found associated with the outbreak strain. Plasmid pC15-1a is a circular molecule of 92,353 bp consisting of two distinct regions. The first is a 64-kb region that is essentially homologous to the non-R-determinant region of plasmid R100 except for several point mutations, a few small insertions and deletions, and the absence of Tn
10
. The second is a 28.4-kb multidrug resistance region (MDR) that has replaced the R-determinant region of the R100 progenitor and consists mostly of transposons or partial transposons and five copies of the insertion element IS
26
. All drug resistance genes found in pC15-1a, including the beta-lactamase genes
bla
CTX-M-15
,
bla
OXA-1
, and
bla
TEM-1
, the tetracycline resistance gene
tetA
, and aminoglycoside resistance genes
aac
(
6
′)-
Ib
and
aac
(
3
)
-II
, are located in the MDR. The
bla
CTX-M-15
gene was found downstream of IS
Ecp1
as part of a transposition unit, as determined from the surrounding sequence. Examination of the plasmids from CTX-M-15-harboring strains isolated from hospitals across Canada showed that pC15-1a was found in several strains isolated from a site in western Canada. Comparison of pC15-1a and pCTX15, found in an
E. coli
strain isolated in India in 1999, revealed that the plasmids had several features in common, including an R100 backbone and several of the resistance genes, including
bla
CTX-M-15
,
bla
TEM-1
,
bla
OXA-1
,
tetA
, and
aac
(
6
′)
-Ib
.
Ertapenem Pharmacokinetics and Impact on Intestinal Microflora, in Comparison to Those of Ceftriaxone, after Multiple Dosing in Male and Female Volunteers
Authors: Pletz Mathias W. R. , Rau Mareike , Bulitta Juergen , De Roux Andres , Burkhardt Olaf , Kruse Guido , Kurowski Michael , Nord Carl E. , Lode Hartmut
Published: September 2004

The pharmacokinetics of ertapenem and ceftriaxone were investigated in an open, randomized, two-period crossover study after single- and multiple-dose administration in 10 healthy volunteers (five women and five men). Both antibiotics were administered intravenously once daily for 7 days at dosages of 1 g (ertapenem) and 2 g (ceftriaxone). The concentrations of the antibiotics in serum and urine were quantified by the agar well diffusion method bioassay and, in addition, for ertapenem only, by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). For ertapenem the maximum concentration of the drug in plasma (
C
max
) was 256 mg/liter, the half-life was 20.7 h, and the area under the plasma concentration-time curve (AUC) was 830 mg · h/liter. The concentrations in fecal samples were (mean value) 37.2 and 32.7 mg/kg on day 4 and day 8, respectively. Ceftriaxone exhibited a mean
C
max
of 315 mg/liter, a half-life of 7.6 h, and an AUC of 1,556 mg · h/liter. The mean concentrations in fecal samples were 153 and 258 mg/kg on day 4 and day 8, respectively. No accumulation of ertapenem or ceftriaxone was detected at steady state. A slightly but significantly decreased AUC for ertapenem was detected for the female volunteers. No serious adverse event was observed. Both antibiotics induced a marked decrease in the anaerobic microflora (4-log-unit decreases in lactobacilli, bifidobacteria, clostridia, and bacteroides) and
Escherichia coli
, whereas the number of enterococci increased (4 log units). A slight overgrowth of yeasts was observed with both regimens. In all cases the microflora returned to normal levels on days 21 to 35.
Azole Resistance in
Candida glabrata
: Coordinate Upregulation of Multidrug Transporters and Evidence for a Pdr1-Like Transcription Factor
Authors: Vermitsky John-Paul , Edlind Thomas D.
Published: September 2004

Candida glabrata
has emerged as a common cause of fungal infection. This yeast has intrinsically low susceptibility to azole antifungals such as fluconazole, and mutation to frank azole resistance during treatment has been documented. Potential resistance mechanisms include changes in expression or sequence of
ERG11
encoding the azole target. Alternatively, resistance could result from upregulated expression of multidrug transporter genes; in
C. glabrata
these include
CDR1
and
PDH1
. By RNA hybridization, 10 of 12 azole-resistant clinical isolates showed 6- to 15-fold upregulation of
CDR1
compared to susceptible strains. In 4 of these 10 isolates
PDH1
was similarly upregulated, and in the remainder it was upregulated three- to fivefold, while
ERG11
expression was minimally changed. Laboratory mutants were selected on fluconazole-containing medium with glycerol as carbon source (to eliminate mitochondrial mutants). Similar to the clinical isolates, six of seven laboratory mutants showed unchanged
ERG11
expression but coordinate
CDR1-PDH1
upregulation ranging from 2- to 20-fold. Effects of antifungal treatment on gene expression in susceptible
C. glabrata
strains were also studied: azole exposure induced
CDR1-PDH1
expression 4- to 12-fold. These findings suggest that these transporter genes are regulated by a common mechanism. In support of this, a mutation associated with laboratory resistance was identified in the
C. glabrata
homolog of
PDR1
which encodes a regulator of multidrug transporter genes in
Saccharomyces cerevisiae
. The mutation falls within a putative activation domain and was associated with
PDR1
autoupregulation. Additional regulatory factors remain to be identified, as indicated by the lack of
PDR1
mutation in a clinical isolate with coordinately upregulated
CDR1-PDH1
.
Effect of Glycine on
Helicobacter pylori
In Vitro
Authors: Minami Masaaki , Ando Takafumi , Hashikawa Shin-nosuke , Torii Keizo , Hasegawa Tadao , Israel Dawn A. , Ina Kenji , Kusugami Kazuo , Goto Hidemi , Ohta Michio
Published: September 2004

Glycine is the simplest amino acid and is used as a metabolic product in some bacteria. However, an excess of glycine inhibits the growth of many bacteria, and it is used as a nonspecific antiseptic agent due to its low level of toxicity in animals. The effect of glycine on
Helicobacter pylori
is not precisely known. The present study was conducted to investigate (i) the effect of glycine on clarithromycin (CLR)-resistant and -susceptible strains of
H. pylori
, (ii) the effect of glycine in combination with amoxicillin (AMX), and (iii) the postantibiotic effect (PAE). The MIC at which 90% of strains are inhibited for glycine was almost 2.5 mg/ml for 31 strains of
H. pylori
, including CLR-resistant strains. We constructed isogenic CLR-resistant mutant strains by natural transformation and investigated the difference between clinical wild-type strains and isogenic mutants. There were no differences in the MICs between CLR-resistant and -susceptible strains or between clinical wild-type and mutant strains. The combination of AMX and glycine showed synergistic activity, with the minimum bactericidal concentration of AMX with glycine decreasing to 1/10 that of AMX alone. Glycine showed no PAE against
H. pylori
. These results suggest that glycine may be a useful antimicrobial agent against
H. pylori
not only alone but also in combination with antibacterial drugs for the treatment of
H. pylori
-associated diseases. Glycine may represent a component of a new type of eradication therapy for CLR-resistant
H. pylori
.
Increasing Prevalence of Quinolone Resistance in Human Nontyphoid
Salmonella enterica
Isolates Obtained in Spain from 1981 to 2003
Authors: Marimón José M. , Gomáriz María , Zigorraga Carmen , Cilla Gustavo , Pérez-Trallero Emilio
Published: September 2004

From January 1981 to December 2003, susceptibility to nalidixic acid was tested in 10,504 nontyphoid
Salmonella enterica
isolates from patients with acute enteric disease in Gipuzkoa, Spain. The prevalence of nalidixic acid resistance steadily increased from less than 0.5% before 1991 to 38.5% in 2003, mainly due to the increase in resistance among isolates of the most prevalent serovar,
S. enterica
serovar Enteritidis. For nalidixic acid-resistant isolates, the ciprofloxacin MIC was eightfold higher than that for susceptible isolates, and the nalidixic acid-resistant isolates contained a single point mutation in the
gyrA
gene (at codons for Ser83 or Asp87). The same mutations were found in a sample of nalidixic acid-resistant nontyphoid
Salmonella
strains isolated between 1999 and 2003 from retail food for human consumption. In 2003, we identified five
S. enterica
serovar Typhimurium clinical isolates with high-level fluoroquinolone resistance (ciprofloxacin MIC, 16 μg/ml) with two point mutations in the
gyrA
gene (coding for Ser83→Phe and Asp87→Asn) and one point mutation in the
parC
gene (coding for Ser80→Arg). Strict sanitary controls are needed to avoid the spread of ciprofloxacin-resistant serovar Typhimurium isolates, and a more efficient veterinary policy must be adopted to decrease the large burden of
Salmonella
serovar Enteritidis infections in humans in our region.
Population Pharmacokinetics of Pyrimethamine and Sulfadoxine in Children Treated for Congenital Toxoplasmosis
Authors: Corvaisier Stéphane , Charpiat Bruno , Mounier Cyril , Wallon Martine , Leboucher Gilles , Al Kurdi Mounzer , Chaulet Jean-François , Peyron François
Published: September 2004

The population pharmacokinetics of pyrimethamine (PYR) and sulfadoxine (SDX) for a group of 32 children with congenital toxoplasmosis was investigated by nonparametric modeling analysis. A one-compartment model was used as the structural model, and individual pharmacokinetic parameters were estimated by Bayesian modeling. PYR (1.25 mg/kg of body weight) and SDX (25 mg/kg) were administered orally every 10 days for 1 year, with adjustment of the dose to body weight every 3 months. Drug concentrations were measured by high-performance liquid chromatography. A total of 101 measurements in serum were available for both drugs. Mean absorption rate constants, volumes of distribution, elimination rate constants, and half-lives were 0.915 h
−1
, 4.379 liters/kg, 0.00839 h
−1
, and 5.5 days for PYR and 1.659 h
−1
, 0.392 liters/kg, 0.00526 h
−1
, and 6.6 days for SDX, respectively. Wide interindividual variability was observed. The estimated minimum and maximum concentrations of PYR in serum differed 8- and 25-fold among patients, respectively, and those of SDX differed 4- and 5-fold, respectively. Increases in the concentration of PYR were observed for eight children, and increases in the SDX concentration were observed for seven children. Serum PYR-SDX concentrations are unpredictable even when the dose is standardized for body weight. The concentrations of the PYR-SDX combination that are most efficacious for children have not yet been established. A model such as ours, associated with long-term follow-up, is needed to study the correlation between exposure to these two drugs and clinical outcome in children.
Antifungal Activities of Posaconazole and Granulocyte-Macrophage Colony-Stimulating Factor Ex Vivo and in Mice with Disseminated Infection Due to
Scedosporium prolificans
Authors: Simitsopoulou M. , Gil-Lamaignere C. , Avramidis N. , Maloukou A. , Lekkas S. , Havlova E. , Kourounaki L. , Loebenberg D. , Roilides E.
Published: September 2004

Invasive infection due to
Scedosporium prolificans
is characterized by drug resistance and a high rate of mortality. The effects of posaconazole (POS), an investigational antifungal triazole, murine granulocyte-macrophage colony-stimulating factor (GM-CSF), and their combination against
S. prolificans
were evaluated ex vivo and in a newly developed murine model of disseminated infection due to this organism. When POS was combined with polymorphonuclear leukocytes from untreated or GM-CSF-treated mice (
P
< 0.01) ex vivo, it had increased activity in terms of the percentage of hyphal damage. Immunocompetent BALB/c mice were infected with 4 × 10
4
conidia of
S. prolificans
via the lateral tail vein. At 24 h postinfection the mice were treated with GM-CSF (5 μg/kg of body weight/day subcutaneously), POS (50 mg/kg/day by gavage), both agents, or saline only. Half of the brain, lung, liver, and kidney from each animal were cultured; and the other half of each organ was processed for histopathology. The mean survival times were 7.0 ± 0.3 days for the controls, 7.4 ± 0.4 days for POS-treated mice, 8.0 ± 0.3 days for GM-CSF-treated mice (
P
= 0.08 compared with the results for the controls), and 7.3 ± 0.3 days for POS-GM-CSF-treated mice. Fungal burdens (determined as the numbers of CFU per gram of tissue) were found in descending orders of magnitude in the kidneys, brains, livers, and lungs. The burdens were significantly reduced in the brains of GM-CSF-treated mice (
P
< 0.05) and the livers of POS-treated mice (
P
< 0.05). The numbers of lesions in the organs closely corresponded to the fungal burdens. GM-CSF tended to prolong survival (
P
= 0.08 compared with the results for the controls). While the combination of POS and GM-CSF showed enhanced activity ex vivo, it did not increase the activities of the two agents against this highly refractory filamentous fungus in mice.
Variant
Salmonella
Genomic Island 1 Antibiotic Resistance Gene Cluster Containing a Novel 3′-
N
-Aminoglycoside Acetyltransferase Gene Cassette,
aac
(3)-
Id
, in
Salmonella enterica
Serovar Newport
Authors: Doublet Benoît , Weill François-Xavier , Fabre Laetitia , Chaslus-Dancla Elisabeth , Cloeckaert Axel
Published: September 2004

Salmonella
genomic island 1 (SGI1) harbors an antibiotic resistance gene cluster and was previously identified in the multidrug-resistant
Salmonella enterica
serovars Typhimurium DT104, Agona, Paratyphi B, and Albany. This antibiotic resistance gene cluster is a complex class 1 integron and most often confers resistance to ampicillin (Ap), chloramphenicol (Cm)/florfenicol (Ff), streptomycin (Sm)/spectinomycin (Sp), sulfonamides (Su), and tetracycline (Tc) (ApCmFfSmSpSuTc profile). Recently, variant SGI1 antibiotic resistance gene clusters conferring different antibiotic resistance profiles have been identified in several
S. enterica
serovars and were classified as SGI1-A to -G. We identified a new variant SGI1 antibiotic resistance gene cluster in two multidrug-resistant
S. enterica
serovar Newport strains isolated from humans in France. In these strains, the Sm/Sp resistance gene cassette
aadA2
inserted at the first
attI1
site was replaced by two other aminoglycoside resistance gene cassettes. The first one contains a new resistance gene encoding an AAC(3)-I aminoglycoside 3-
N
-acetyltransferase that confers resistance to gentamicin (Gm) and sisomicin (Sc). This gene has been named
aac
(3)-
Id
. The second one harbors the Sm/Sp resistance gene
aadA7
. This gene cassette replacement in the SGI1 complex integron of serovar Newport strains constitutes a new variant SGI1 antibiotic resistance gene cluster named SGI1-H. The occurrence of SGI1 in different
S. enterica
serovars, now including serovar Newport, strengthens the hypothesis of horizontal transfer of SGI1.
Liquid Chromatography Assay for Routine Monitoring of Cellular Ribavirin Levels in Blood
Authors: Inoue Yoichi , Homma Masato , Matsuzaki Yasushi , Shibata Minoru , Matsumura Takuya , Ito Takayoshi , Mitamura Keiji , Tanaka Naomi , Kohda Yukinao
Published: September 2004

Ribavirin-induced hemolytic anemia is one cause for cessation of combination therapy with alpha interferon 2b and ribavirin for hepatitis C infection. Determining cellular ribavirin levels in blood, including the levels of its phosphorylated metabolites, might be useful for predicting ribavirin-induced anemia, because the metabolites accumulate in erythrocytes. We simplified an assay method developed previously to make it suitable for routine monitoring of cellular ribavirin. Whole blood diluted with a sixfold volume of ice-cold distilled water was subjected to acid phosphatase digestion to convert phosphorylated ribavirin metabolites to free ribavirin. The resulting mixture, spiked with an internal standard, was treated by phenyl boronic acid column extraction, followed by reverse-phase high-performance liquid chromatography analysis. The calibration curve for ribavirin levels in whole blood was linear at concentrations of 5.3 to 1,024 μM (r2= 0.9999). Validation coefficients of variation for intra- and interday assays were 2.9 to 5.8% and 4.3 to 8.3%, respectively. We tested this method by monitoring blood ribavirin concentrations in two hepatitis C patients receiving alpha interferon 2b-plus-ribavirin combination therapy.