bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combination of Tigecycline and
N
-Acetylcysteine Reduces Biofilm-Embedded Bacteria on Vascular Catheters
Authors: Aslam Saima , Trautner Barbara W. , Ramanathan Venkat , Darouiche Rabih O. 
Published: January 2007

ABSTRACT

To assess the efficacy of an antibiofilm/antimicrobial agent combination, we incubated catheter segments colonized with one of six studied bacterial organisms in
N
-acetylcysteine, tigecycline,
N
-acetylcysteine-tigecycline, or saline. Segments were washed, sonicated, and cultured.
N
-acetylcysteine-tigecycline significantly decreased all viable biofilm-associated bacteria and was synergistic for methicillin-resistant
Staphylococcus aureus
and
Staphylococcus epidermidis
.
Genetics and Expression of the Carbapenem-Hydrolyzing Oxacillinase GeneblaOXA-23inAcinetobacter baumannii
Authors: Corvec Stéphane , Poirel Laurent , Naas Thierry , Drugeon Henri , Nordmann Patrice 
Published: January 2007

ABSTRACTThe genetic structures surrounding the plasmid-carriedblaOXA-23oxacillinase gene, encoding resistance to carbapenems, were studied inAcinetobacter baumannii. ISAba1and the novel element ISAba4were detected upstream of theblaOXA-23gene, providing promoter sequences for its expression. These insertion elements were likely involved in transposition processes at the origin of acquisition of this β-lactamase gene.
Zidovudine Inhibits Thymidine Phosphorylation in the Isolated Perfused Rat Heart
Authors: Susan-Resiga Delia , Bentley Alice T. , Lynx Matthew D. , LaClair Darcy D. , McKee Edward E. 
Published: January 2007

ABSTRACTZidovudine (AZT; 3′-azido-3′-deoxythymidine), a thymidine analog, has been a staple of highly active antiretroviral therapy. It is phosphorylated in the host to the triphosphate and functions by inhibiting the viral reverse transcriptase. However, long-term use of AZT is linked to various tissue toxicities, including cardiomyopathy. These toxicities are associated with mitochondrial DNA depletion, which is hypothesized to be caused by AZT triphosphate inhibition of mitochondrial DNA polymerase γ. In previous work with isolated heart mitochondria, we demonstrated that AZT phosphorylation beyond the monophosphate was not detected and that AZT itself was a potent inhibitor of thymidine phosphorylation. This suggests an alternative hypothesis in which depletion of the TTP pool may limit mitochondrial DNA replication. The present work extends these studies to the whole cell by investigating the metabolism of thymidine and AZT in the intact isolated perfused rat heart. [3H]thymidine is converted to [3H]TTP in a time- and concentration-dependent manner. The level of [3H]TMP is low, suggesting that the reaction catalyzed by thymidine kinase is the rate-limiting step in phosphorylation. [3H]AZT is converted in a time- and concentration-dependent manner to AZT monophosphate, the only phosphorylated product detected after 3 h of perfusion. Both compounds display negative cooperativity, similar to the observations with cloned and purified mitochondrial thymidine kinase 2. The presence of AZT in the perfusate inhibits the phosphorylation of [3H]thymidine with a 50% inhibitory concentration of 24 ± 4 μM. These data support the hypothesis that AZT-induced mitochondrial cardiotoxicity may be caused by a limiting pool of TTP that lowers mitochondrial DNA replication.
Activity of Daptomycin Alone and in Combination with Rifampin and Gentamicin against
Staphylococcus aureus
Assessed by Time-Kill Methodology
Authors: Credito Kim , Lin Gengrong , Appelbaum Peter C. 
Published: January 2007

ABSTRACT

The synergistic effects of daptomycin plus gentamicin or rifampin were tested against 50
Staphylococcus aureus
strains, with daptomycin MICs ranging between 0.25 and 8 μg/ml. Daptomycin sub-MICs combined with gentamicin concentrations lower than the MIC yielded synergy in 34 (68%) of the 50 strains. Daptomycin combined with rifampin yielded synergy in one vancomycin-intermediate
S. aureus
strain only, and virtually all synergy occurred between daptomycin and gentamicin.
Rectoanal Junction Colonization of Feedlot Cattle by
Escherichia coli
O157:H7 and Its Association with Supershedders and Excretion Dynamics
Authors: Cobbold Rowland N. , Hancock Dale D. , Rice Daniel H. , Berg Janice , Stilborn Robert , Hovde Carolyn J. , Besser Thomas E. 
Published: January 2007

ABSTRACT

Feedlot cattle were observed for fecal excretion of and rectoanal junction (RAJ) colonization with
Escherichia coli
O157:H7 to identify potential “supershedders.” RAJ colonization and fecal excretion prevalences were correlated, and
E. coli
O157:H7 prevalences and counts were significantly greater for RAJ samples. Based on a comparison of RAJ and fecal ratios of
E. coli
O157:H7/
E. coli
counts, the RAJ appears to be preferentially colonized by the O157:H7 serotype. Five supershedders were identified based on persistent colonization with high concentrations of
E. coli
O157:H7. Cattle copenned with supershedders had significantly greater mean pen
E. coli
O157:H7 RAJ and fecal prevalences than noncopenned cattle. Cumulative fecal
E. coli
O157:H7 excretion was also significantly higher for pens housing a supershedder.
E. coli
O157:H7/
E. coli
count ratios were higher for supershedders than for other cattle, indicating greater proportional colonization. Pulsed-field gel electrophoresis analysis demonstrated that isolates from supershedders and copenned cattle were highly related. Cattle that remained negative for
E. coli
O157:H7 throughout sampling were five times more likely to have been in a pen that did not house a supershedder. The data from this study support an association between levels of fecal excretion of
E. coli
O157:H7 and RAJ colonization in pens of feedlot cattle and suggest that the presence of supershedders influences group-level excretion parameters. An improved understanding of individual and population transmission dynamics of
E. coli
O157:H7 can be used to develop preslaughter- and slaughter-level interventions that reduce contamination of the food chain.
The Presence of the Internalin Gene in Natural Atypically Hemolytic
Listeria innocua
Strains Suggests Descent from
L. monocytogenes
Authors: Volokhov Dmitriy V. , Duperrier Sandra , Neverov Alexander A. , George Joseph , Buchrieser Carmen , Hitchins Anthony D. 
Published: January 2007

ABSTRACT

The atypical hemolytic
Listeria innocua
strains PRL/NW 15B95 and J1-023 were previously shown to contain gene clusters analogous to the pathogenicity island (LIPI-1) present in the related foodborne gram-positive facultative intracellular pathogen
Listeria monocytogenes
, which causes listeriosis. LIPI-1 includes the hemolysin gene, thus explaining the hemolytic activity of the atypical
L. innocua
strains. No other
L. monocytogenes
-specific virulence genes were found to be present. In order to investigate whether any other specific
L. monocytogenes
genes could be identified, a global approach using a
Listeria
biodiversity DNA array was applied. According to the hybridization results, the isolates were defined as
L. innocua
strains containing LIPI-1. Surprisingly, evidence for the presence of the
L. monocytogenes
-specific
inlA
gene, previously thought to be absent, was obtained. The
inlA
gene codes for the InlA protein which enables bacterial entry into some nonprofessional phagocytic cells. PCR and sequence analysis of this region revealed that the flanking genes of the
inlA
gene at the upstream, 5′-end region were similar to genes found in
L. monocytogenes
serotype 4b isolates, whereas the organization of the downstream, 3′-end region was similar to that typical of
L. innocua
. Sequencing of the
inlA
region identified a small stretch reminiscent of the
inlB
gene of
L. monocytogenes
. The presence of two clusters of
L. monocytogenes
-specific genes makes it unlikely that PRL/NW 15B95 and J1-023 are
L. innocua
strains altered by horizontal transfer. It is more likely that they are distinct relics of the evolution of
L. innocua
from an ancestral
L. monocytogenes
, as postulated by others.
A Portable Anaerobic Microbioreactor Reveals Optimum Growth Conditions for the Methanogen
Methanosaeta concilii
Authors: Steinhaus Benjamin , Garcia Marcelo L. , Shen Amy Q. , Angenent Largus T. 
Published: January 2007

ABSTRACT

Conventional studies of the optimum growth conditions for methanogens (methane-producing, obligate anaerobic archaea) are typically conducted with serum bottles or bioreactors. The use of microfluidics to culture methanogens allows direct microscopic observations of the time-integrated response of growth. Here, we developed a microbioreactor (μBR) with ∼1-μl microchannels to study some optimum growth conditions for the methanogen
Methanosaeta concilii
. The μBR is contained in an anaerobic chamber specifically designed to place it directly onto an inverted light microscope stage while maintaining a N
2
-CO
2
environment. The methanogen was cultured for months inside microchannels of different widths. Channel width was manipulated to create various fluid velocities, allowing the direct study of the behavior and responses of
M. concilii
to various shear stresses and revealing an optimum shear level of ∼20 to 35 μPa. Gradients in a single microchannel were then used to find an optimum pH level of 7.6 and an optimum total NH
4
-N concentration of less than 1,100 mg/liter (<47 mg/liter as free NH
3
-N) for
M. concilii
under conditions of the previously determined ideal shear stress and pH and at a temperature of 35°C.
Recombinant Polycistronic Structure of Hydantoinase Process Genes in
Escherichia coli
for the Production of Optically Pure
d
-Amino Acids
Authors: Martínez-Gómez Ana Isabel , Martínez-Rodríguez Sergio , Clemente-Jiménez Josefa María , Pozo-Dengra Joaquín , Rodríguez-Vico Felipe , Las Heras-Vázquez Francisco Javier 
Published: January 2007

ABSTRACT

Two recombinant reaction systems for the production of optically pure
d
-amino acids from different
d,l
-5-monosubstituted hydantoins were constructed. Each system contained three enzymes, two of which were
d
-hydantoinase and
d
-carbamoylase from
Agrobacterium tumefaciens
BQL9. The third enzyme was hydantoin racemase 1 for the first system and hydantoin racemase 2 for the second system, both from
A. tumefaciens
C58. Each system was formed by using a recombinant
Escherichia coli
strain with one plasmid harboring three genes coexpressed with one promoter in a polycistronic structure. The
d
-carbamoylase gene was cloned closest to the promoter in order to obtain the highest level of synthesis of the enzyme, thus avoiding intermediate accumulation, which decreases the reaction rate. Both systems were able to produce 100% conversion and 100% optically pure
d
-methionine,
d
-leucine,
d
-norleucine,
d
-norvaline,
d
-aminobutyric acid,
d
-valine,
d
-phenylalanine,
d
-tyrosine, and
d
-tryptophan from the corresponding hydantoin racemic mixture. For the production of almost all
d
-amino acids studied in this work, system 1 hydrolyzed the 5-monosubstituted hydantoins faster than system 2.
Use of Bimolecular Fluorescence Complementation To Study In Vivo Interactions between Cdc42p and Rdi1p of
Saccharomyces cerevisiae
Authors: Cole Karen C. , McLaughlin Heather W. , Johnson Douglas I. 
Published: January 2007

ABSTRACT

Saccharomyces cerevisiae
Cdc42p functions as a GTPase molecular switch, activating multiple signaling pathways required to regulate cell cycle progression and the actin cytoskeleton. Regulatory proteins control its GTP binding and hydrolysis and its subcellular localization, ensuring that Cdc42p is appropriately activated and localized at sites of polarized growth during the cell cycle. One of these, the Rdi1p guanine nucleotide dissociation inhibitor, negatively regulates Cdc42p by extracting it from cellular membranes. In this study, the technique of bimolecular fluorescence complementation (BiFC) was used to study the dynamic in vivo interactions between Cdc42p and Rdi1p. The BiFC data indicated that Cdc42p and Rdi1p interacted in the cytoplasm and around the periphery of the cell at the plasma membrane and that this interaction was enhanced at sites of polarized cell growth during the cell cycle, i.e., incipient bud sites, tips and sides of small- and medium-sized buds, and the mother-bud neck region. In addition, a ring-like structure containing the Cdc42p-Rdi1p complex transiently appeared following release from G
1
-phase cell cycle arrest. A homology model of the Cdc42p-Rdi1p complex was used to introduce mutations that were predicted to affect complex formation. These mutations resulted in altered BiFC interactions, restricting the complex exclusively to either the plasma membrane or the cytoplasm. Data from these studies have facilitated the temporal and spatial modeling of Rdi1p-dependent extraction of Cdc42p from the plasma membrane during the cell cycle.
Potential Role for Toll-Like Receptor 4 in Mediating
Escherichia coli
Maltose-Binding Protein Activation of Dendritic Cells
Authors: Fernandez Stefan , Palmer Dupeh R. , Simmons Monika , Sun Peifang , Bisbing John , McClain Sasha , Mani Sachin , Burgess Timothy , Gunther Vicky , Sun Wellington 
Published: January 2007

ABSTRACT

The
Escherichia coli
maltose-binding protein (MBP) is used to increase the stability and solubility of proteins in bacterial protein expression systems and is increasingly being used to facilitate the production and delivery of subunit vaccines against various pathogenic bacteria and viruses. The MBP tag is presumed inert, with minimum effects on the bioactivity of the tagged protein or its biodistribution. However, few studies have characterized the immunological attributes of MBP. Here, we analyze the phenotypic and functional outcomes of MBP-treated dendritic cells (DCs) and show that MBP induces DC activation and production of proinflammatory cytokines (interleukin-1β [IL-1β], IL-6, IL-8, tumor necrosis factor alpha, and IL-12p70) within 24 h and strongly increases Iκβ phosphorylation in treated cells. Interestingly, phosphorylation of Iκβ was largely abrogated by the addition of anti-human Toll-like receptor 4 (TLR4) antibodies, indicating that MBP activates signaling for DC maturation via TLR4. Consistent with this hypothesis, MBP activated the TLR4-expressing cell line 293-hTLR4A but not control cultures to secrete IL-8. The observed data were independent of lipopolysaccharide contamination and support a role for TLR4 in mediating the effects of MBP. These results provide insight into a mechanism by which MBP might enhance immune responses to vaccine fusion proteins.
SiiE Is Secreted by the
Salmonella enterica
Serovar Typhimurium Pathogenicity Island 4-Encoded Secretion System and Contributes to Intestinal Colonization in Cattle
Authors: Morgan Eirwen , Bowen Alison J. , Carnell Sonya C. , Wallis Timothy S. , Stevens Mark P. 
Published: January 2007

ABSTRACT

Here we report that
Salmonella enterica
serovar Typhimurium pathogenicity island 4 carries a type I secretion system (
siiCDF
) which secretes an ∼600-kDa protein (encoded by
siiE
). SiiE is surface expressed, and its production is regulated by HilA. SiiE and SiiF influence colonization in cattle and the invasion of bovine enterocytes.
Interleukin-12 Drives the Th1 Signaling Pathway inHelicobacter pylori-Infected Human Gastric Mucosa
Authors: Pellicanò Antonia , Sebkova Ladislava , Monteleone Giovanni , Guarnieri Giovanni , Imeneo Maria , Pallone Francesco , Luzza Francesco 
Published: January 2007

ABSTRACTIn this study we examined mechanisms that regulate T-helper lymphocyte 1 (Th1) commitment inHelicobacter pylori-infected human gastric mucosa. The levels of gamma interferon (IFN-γ), interleukin-4 (IL-4), and IL-12 in total extracts of gastric biopsies taken fromH. pylori-infected and uninfected patients were determined by an enzyme-linked immunosorbent assay. The levels of signal transducer and activator of transcription 4 (STAT4), STAT6, and T-box expressed in T cells (T-bet) in total proteins extracted from gastric biopsies were determined by Western blotting. Finally, the effect of a neutralizing IL-12 antibody on expression of Th1 transcription factors and the levels of IFN-γ in organ cultures ofH. pylori-infected biopsies was examined. Increased levels of IFN-γ and IL-12 were found in gastric biopsy samples ofH. pylori-infected patients compared to the levels in uninfected patients. In addition,H. pylori-infected biopsies exhibited high levels of expression of phosphorylated STAT4 and T-bet. Higher levels of IFN-γ and expression of Th1 transcription factors were associated with greater infiltration of mononuclear cells in the gastric mucosa. By contrast, production of IL-4 and expression of phosphorylated STAT6 were not associated with the intensity of mononuclear cell infiltration. In ex vivo organ cultures ofH. pylori-infected biopsies, neutralization of endogenous IL-12 down-regulated the expression of phosphorylated STAT4 and T-bet and reduced IFN-γ production. Our data indicated that IL-12 contributes to the Th1 cell commitment inH. pylori-infected human gastric mucosa.
Immunostimulatory Properties of the Emerging Pathogen
Stenotrophomonas maltophilia
Authors: Waters Valerie J. , Gómez Marisa I. , Soong Grace , Amin Sunil , Ernst Robert K. , Prince Alice 
Published: January 2007

ABSTRACT

Stenotrophomonas maltophilia
is a multiple-antibiotic-resistant opportunistic pathogen that is being isolated with increasing frequency from patients with health-care-associated infections and especially from patients with cystic fibrosis (CF). While clinicians feel compelled to treat infections involving this organism, its potential for virulence is not well established. We evaluated the immunostimulatory properties and overall virulence of clinical isolates of
S. maltophilia
using the well-characterized opportunistic pathogen
Pseudomonas aeruginosa
PAO1 as a control. The properties of CF isolates were examined specifically to see if they have a common phenotype. The immunostimulatory properties of
S. maltophilia
were studied in vitro by stimulating airway epithelial and macrophage cell lines. A neonatal mouse model of pneumonia was used to determine the rates of pneumonia, bacteremia, and mortality, as well as the inflammatory response elicited by
S. maltophilia
infection. Respiratory and nonrespiratory
S. maltophilia
isolates were highly immunostimulatory and elicited significant interleukin-8 expression by airway epithelial cells, as well as tumor necrosis factor alpha (TNF-α) expression by macrophages. TNF-α signaling appears to be important in the pathogenesis of
S. maltophilia
infection as less than 20% of TNFR1 null mice (compared with 100% of wild-type mice) developed pneumonia and bacteremia following intranasal inoculation. The
S. maltophilia
isolates were weakly invasive, and low-level bacteremia with no mortality was observed. Despite the lack of invasiveness of
S. maltophilia
, the immunostimulatory properties of this organism and its induction of TNF-α expression specifically indicate that it is likely to contribute significantly to airway inflammation.
Leishmania donovani-Induced Ceramide as the Key Mediator of Akt Dephosphorylation in Murine Macrophages: Role of Protein Kinase Cζ and Phosphatase
Authors: Dey Ranadhir , Majumder Nivedita , Bhattacharjee Surajit , Majumdar Suchandra Bhattacharyya , Banerjee Rajdeep , Ganguly Sandipan , Das Pradeep , Majumdar Subrata 
Published: January 2007

ABSTRACTLeishmania donovaniis an intracellular protozoan parasite that impairs the host macrophage immune response to render it suitable for its survival and establishment.L. donovani-induced immunosuppression and alteration of host cell signaling is mediated by ceramide, a pleiotropic second messenger playing an important role in regulation of several kinases, including mitogen-activated protein kinase and phosphatases. We observed that the endogenous ceramide generated during leishmanial infection led to the dephosphorylation of protein kinase B (PKB) (Akt) in infected cells. The study of ceramide-mediated Akt phosphorylation revealed that Akt was dephosphorylated at both Thr308 and Ser473 sites in infected cells. Further investigation demonstrated that ceramide was also responsible for the induction of PKCζ, an atypical Ca-independent stress kinase, as well as the ceramide-activated protein phosphatases (e.g., protein phosphatase 2A [PP2A]). We found that Akt dephosphorylation was mediated by ceramide-induced PKCζ-Akt association and PP2A activation. In addition, treatment ofL. donovani-infected macrophages with PKCζ-specific inhibitor peptide could restore the translocation of phosphorylated Akt to the cell membrane. This study also revealed that ceramide is involved in the inhibition of proinflammatory cytokine tumor necrosis factor alpha release by infected macrophages. These observations strongly suggest the importance of ceramide in the alteration of normal cellular functions, impairment of the kinase/phosphatase balance, and thereby establishment of leishmaniasis in the hostile macrophage environment.
Monocyte Chemoattractant Protein 1, Macrophage Inflammatory Protein 1α, and RANTES Recruit Macrophages to the Kidney in a Mouse Model of Hemolytic-Uremic Syndrome
Authors: Keepers Tiffany R. , Gross Lisa K. , Obrig Tom G. 
Published: January 2007

ABSTRACT
The macrophage has previously been implicated in contributing to the renal inflammation associated with hemolytic-uremic syndrome (HUS). However, there is currently no in vivo model detailing the contribution of the renal macrophage to the kidney disease associated with HUS. Therefore, renal macrophage recruitment and inhibition of infiltrating renal macrophages were evaluated in an established HUS mouse model. Macrophage recruitment to the kidney was evident by immunohistochemistry 2 h after administration of purified Stx2 and peaked at 48 h postinjection. Mice administered a combination of Stx2 and lipopolysaccharide (LPS) showed increased macrophage recruitment to the kidney compared to mice treated with Stx2 or LPS alone. Monocyte chemoattractants were induced in the kidney, including monocyte chemoattractant protein 1 (MCP-1/CCL2), macrophage inflammatory protein 1α (MIP-1α/CCL3), and RANTES (CCL5), in a pattern that was coincident with macrophage infiltration as indicated by immunohistochemistry, protein, and RNA analyses. MCP-1 was the most abundant chemokine, MIP-1α was the least abundant, and RANTES levels were intermediate. Mice treated with MCP-1, MIP-1α, and RANTES neutralizing antibodies had a significant decrease in Stx2 plus LPS-induced macrophage accumulation in the kidney, indicating that these chemokines are required for macrophage recruitment. Furthermore, mice exposed to these three neutralizing antibodies had decreased fibrin deposition in their kidneys, implying that macrophages contribute to the renal damage associated with HUS.