bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selection and Persistence of CTX-M-Producing
Escherichia coli
in the Intestinal Flora of Pigs Treated with Amoxicillin, Ceftiofur, or Cefquinome
Authors: Cavaco L. M. , Abatih E. , Aarestrup F. M. , Guardabassi L. 
Published: July 2008

ABSTRACT

Extended-spectrum β-lactamases (ESBLs), mainly of the CTX-M family, have been associated with
Escherichia coli
strains of animal origin in Europe. An in vivo experiment was performed to study the effects of veterinary β-lactam drugs on the selection and persistence of ESBL-producing
E. coli
in the intestinal flora of pigs. Twenty pigs were randomly allocated into three treatment groups and one control group. All pigs were inoculated intragastrically with 10
10
CFU of a nalidixic acid (NAL)-resistant mutant derived from a CTX-M-1-producing
E. coli
strain of pig origin. Treatment with amoxicillin, ceftiofur, or cefquinome according to the instructions on the product label was initiated immediately after bacterial inoculation. Feces were collected from the rectum before inoculation and on days 4, 8, 15, 22, and 25 after the start of treatment. The total and resistant coliforms were counted on MacConkey agar with and without cefotaxime (CTX). Furthermore, MacConkey agar with CTX and NAL was used to count the number of CFU of the inoculated strain. Significantly higher counts of CTX-resistant coliforms were observed in the three treatment groups than in the control group for up to 22 days after the discontinuation of treatment. Ceftiofur and cefquinome exerted larger selective effects than amoxicillin, and the effects persisted beyond the withdrawal times recommended for these cephalosporins. The inoculated strain was detected in only nine animals on day 25. The increase in the number of CTX-resistant coliforms was mainly due to the proliferation of indigenous CTX-M-producing strains and the possible emergence of strains that acquired CTX-M genes by horizontal transfer. The study provides evidence that the cephalosporins used in pig production select for CTX-M-producing
E. coli
strains. Their use in animals should be carefully considered in view of the critical importance of cephalosporins and the zoonotic potential of ESBL-producing bacteria.
Plasmid-Mediated Quinolone Resistance Pump QepA2 in an
Escherichia coli
Isolate from France
Authors: Cattoir Vincent , Poirel Laurent , Nordmann Patrice 
Published: July 2008

ABSTRACT

One hundred twenty-one extended-spectrum β-lactamse-producing enterobacterial clinical isolates were screened for the
qepA
gene. A single CTX-M-15-positive
Escherichia coli
isolate (0.8%) that produced the putative pump QepA2 was identified. This
qepA2
gene was located onto a 90-kb mobilizable plasmid that conferred reduced susceptibility to hydrophilic fluoroquinolones.
Genomic Analysis Reveals a Point Mutation in the Two-Component Sensor Gene
graS
That Leads to Intermediate Vancomycin Resistance in Clinical
Staphylococcus aureus
Authors: Howden Benjamin P. , Stinear Timothy P. , Allen David L. , Johnson Paul D. R. , Ward Peter B. , Davies John K. 
Published: July 2008

ABSTRACT

Methicillin-resistant
Staphylococcus aureus
(MRSA), once restricted to hospitals, is spreading rapidly through the wider community. Resistance to vancomycin, the principal drug used to treat MRSA infections, has only recently emerged, is mainly low level, and characteristically appears during vancomycin therapy (vancomycin-intermediate
S. aureus
[VISA] and hetero-resistant VISA). This phenomenon suggests the adaptation of MRSA through mutation, although defining the mutations leading to resistance in clinical isolates has been difficult. We studied a vancomycin-susceptible clinical MRSA isolate (MIC of 1 μg/ml) and compared it with an isogenic blood culture isolate from the same patient, despite 42 days of vancomycin treatment (MIC of 4 μg/ml). A whole-genome sequencing approach allowed the nearly complete assembly of the genome sequences of the two isolates and revealed only six nucleotide substitutions in the VISA strain compared with the parent strain. One mutation occurred in
graS
, encoding a putative two-component regulatory sensor, leading to a change from a polar to a nonpolar amino acid (T136I) in the conserved histidine region of the predicted protein. Replacing the
graS
allele of the vancomycin-susceptible parent strain with the
graS
allele from the VISA derivative resulted in increased vancomycin resistance at a level between those of the vancomycin-susceptible
S. aureus
and VISA clinical isolates, confirming a role for
graRS
in VISA. Our study suggests that MRSA is able to develop clinically significant vancomycin resistance via a single point mutation, and the two-component regulatory system
graRS
is a key mediator of this resistance. However, additional mutations are likely required to express the full VISA phenotype.
Human Mast Cell Activation byStaphylococcus aureus: Interleukin-8 and Tumor Necrosis Factor Alpha Release and the Role of Toll-Like Receptor 2 and CD48 Molecules
Authors: Rocha-de-Souza Claudio M. , Berent-Maoz Beata , Mankuta David , Moses Allon E. , Levi-Schaffer Francesca 
Published: July 2008

ABSTRACTThe ability ofStaphylococcus aureusto invade and survive within host cells is believed to contribute to its propensity to cause persistent and metastatic infections. In addition,S. aureusinfections often are associated with atopic diseases such as dermatitis, rhinitis, and asthma. Mast cells, the key cells of allergic diseases, have a pivotal role in innate immunity and have the capacity of phagocytosis, and they can destroy some pathogenic bacteria. However, little is known about the ability of some other bacteria to survive and overcome mast cell phagocytosis. Therefore, we were interested in evaluating the interplay between mast cells andS. aureus. In this study, we show that human cord blood-derived mast cells (CBMC) can be infected by pathogenicS. aureus.S. aureusdisplayed a high adherence to mast cells as well as invasive and survival abilities within them. However, when infections were performed in the presence of cytochalasin D or when CBMC were preincubated with anti-Toll-like receptor 2 (TLR2) or anti-CD48 antibodies, the invasiveness and the inflammatory response were abrogated, respectively. Furthermore, we observed an increase of TLR2 and CD48 molecules on CBMC afterS. aureusinfection. The infection of CBMC withS. aureusalso caused the release of tumor necrosis factor alpha (TNF-α) and interleukin-8 (IL-8). Both live and killedS. aureusorganisms were found to trigger TNF-α and IL-8 release by CBMC in a time-dependent manner. Cumulatively, these findings suggest thatS. aureusinternalizes and survives in mast cells. This may play an important role in infections and in atopic diseases associated withS. aureus.
A Tripartite Efflux Pump Involved in Gastrointestinal Colonization by
Klebsiella pneumoniae
Confers a Tolerance Response to Inorganic Acid
Authors: Coudeyras Sophie , Nakusi Laurence , Charbonnel Nicolas , Forestier Christiane 
Published: July 2008

ABSTRACT

The colonization of the gastrointestinal tract of patients by the opportunistic gram-negative bacillus
Klebsiella pneumoniae
generally occurs prior to the development of nosocomial infections. Mutant strain C-81 was isolated owing to its reduced capacity to colonize the digestive tract in a murine model following transposon mutagenesis (N. Maroncle, D. Balestrino, C. Rich, and C. Forestier, Infect. Immun. 70:4729-4734, 2002). Nucleotide sequence analysis showed that the transposon had inserted into the first open reading frame,
eefA
, of a three-gene locus (
eefABC
) whose homologue encodes a tripartite efflux pump in
Enterobacter aerogenes
(M. Masi, J. M. Pages, C. Villard, and E. Pradel, J. Bacteriol. 187:3894-3897, 2005), and this operon includes an additional short (183-bp) potential open reading frame,
eefX
, upstream of
eefA
. In vivo assays showed that a Δ
eefA
isogenic mutant strain normally colonized the gastrointestinal tract in single-strain tests but was significantly impaired in competition against wild-type strain LM21. Although the cecum was the compartment with the highest number of CFU, the Δ
eefA
mutant also was detected in the stomach in numbers smaller than those of the wild-type strain. The expression of this potential efflux pump could not be linked to any antimicrobial drug resistance phenotype, but it conferred on the bacteria an acid tolerance response to inorganic acid. The expression of the
eef
promoter region, measured via a
lacZ
reporter construction, was slightly induced by an acidic environment and also by hyperosmolarity but not by the presence of bile salts. These results suggest that an efflux pump can confer measurable ecological benefits on
K. pneumoniae
in an environment with high competition potential.
The Antifungal Vaccine Derived from the Recombinant N Terminus of Als3p Protects Mice against the BacteriumStaphylococcus aureus
Authors: Spellberg Brad , Ibrahim Ashraf S. , Yeaman Michael R. , Lin Lin , Fu Yue , Avanesian Valentina , Bayer Arnold S. , Filler Scott G. , Lipke Peter , Otoo Henry , Edwards John E. 
Published: July 2008

ABSTRACTVaccination with the recombinant N terminus of the candidal adhesin Als3p (rAls3p-N) protects mice from lethal candidemia. Candidal Als3p also is structurally similar to the microbial surface components recognizing adhesive matrix molecule adhesin, clumping factor, fromStaphylococcus aureus.To determine the potential for cross-kingdom vaccination, we immunized mice with rAls3p-N or negative control proteins and challenged them via the tail vein withS. aureusor other gram-positive or gram-negative pathogens. The rAls3p-N vaccine, but neither tetanus toxoid nor a related Als protein (Als5p), improved the survival of vaccinated mice subsequently infected with multiple clinical isolates ofS. aureus, including methicillin-resistant strains. The rAls3p-N vaccine was effective againstS. aureuswhen combined with aluminum hydroxide adjuvant. However, the vaccine did not improve the survival of mice infected with other bacterial pathogens. Vaccinated, infected mice mounted moderated type 1 immune responses. T lymphocyte-deficient mice were more susceptible toS. aureusinfection, but B lymphocyte-deficient mice were not. Furthermore, T but not B lymphocytes from vaccinated mice mediated protection in adoptive transfer studies. The passive transfer of immune serum was not protective. These data provide the foundation for cross-kingdom vaccine development againstS. aureusandCandida, which collectively cause 200,000 bloodstream infections resulting in ≥40,000 to 50,000 deaths annually in the United States alone.
Cytolethal Distending Toxin Induces Caspase-Dependent and -Independent Cell Death in MOLT-4 Cells
Authors: Ohara Masaru , Hayashi Tomonori , Kusunoki Yoichiro , Nakachi Kei , Fujiwara Tamaki , Komatsuzawa Hitoshi , Sugai Motoyuki 
Published: July 2008

ABSTRACT

Cytolethal distending toxin (CDT) induces apoptosis using the caspase-dependent classical pathway in the majority of human leukemic T cells (MOLT-4). However, we found the process to cell death is only partially inhibited by pretreatment of the cells with a general caspase inhibitor, z-VAD-fmk. Flow cytometric analysis using annexin V and propidium iodide showed that a 48-h CDT treatment decreased the living cell population by 35% even in the presence of z-VAD-fmk. z-VAD-fmk completely inhibited caspase activity in 24 h CDT-intoxicated cells. Further, CDT with z-VAD-fmk treatment clearly increased the cell population that had a low level of intracellular reactive oxygen. This is a characteristic opposite to that of caspase-dependent apoptosis. Overexpression of
bcl2
almost completely inhibited cell death using CDT treatment in the presence of z-VAD-fmk. The data suggest there are at least two different pathways used in CDT-induced cell death: conventional caspase-dependent (early) apoptotic cell death and caspase-independent (late) death. Both occur via the mitochondrial membrane disruption pathway.
Pore-water pressures in soft to firm clay during driving of piles into underlying dense sand
Authors: Eigenbrod K D , Issigonis T 
Published: July 2008

During driving of steel piles through soft, sensitive clay into very dense sand and gravel, pore-water pressure responses were monitored. As a result of the large length of the piles and also because of the high sensitivity of the soft clays, the piles were driven in two stages. During the initial stage of driving in the soft clay, only very small pore-water pressure increases were recorded together with very low pile driving resistances; however, during the second stage of driving, high pore-water pressure increases were observed in the clay as soon as the piles penetrated into the underlying very dense sand and gravel. It was concluded that the clay deposit was loaded from below, as the piles were driven into very dense sand. The total stress changes and the resulting pore-water pressure changes in the clay were analyzed, assuming that the pile driving load was equivalent to a flexible load acting on the surface of an elastic half-space, which represents the soft clay deposit. This interpretation of the pore-water pressure increases is important for the assessment of the bearing capacity of engineering structures affected by piles driven through soft soils into very dense deposits. The potential for high pore-water pressure increases in the clay during undrained loading as well as for volume increases in the dense sand due to pile driving can be predicted from piezocone test data. Key words: pile driving, pore-water pressure, piezocone testing, soft sensitive clays, dense sand deposits.
Numerical study of parameters influencing the response of flexible retaining walls
Authors: Vaziri Hans H 
Published: July 2008

A practical numerical model is described for analysis of flexible retaining walls. In terms of capabilities, the model fits between traditional limit equilibrium methods and full finite element approaches; it overcomes many of the limitations associated with the former but is not equipped with the versatility offered by the latter. Using an approach similar to that adopted in boundary-element based models, the wall stiffness is represented by a series of elastic beam elements whose stiffness is combined with that of the prestressed struts and the soil to form, the overall stiffness matrix. The stiffness matrix of the soil is obtained by inversion of flexibility matrices generated by interpolation and sealing of flexibility matrices calculated for a simplified soil model using finite element methods. The soil behaves linearly elastically, as long as the pressures correspond to stress levels lying between the limits. Where the lateral displacement of the wall corresponds to a pressure outside of these allowable limits, correction forces are added until the resulting pressures are within the active or passive pressures. Arching is permitted by considering the forces acting on the wall compared with the forces consistent with possible failure surfaces within the soil. Other features that can be accomodated by the model include struts, variations in water table, and the effects of surcharges. The proposed model has been shown to capture the displacement, anchor loads, and lateral stresses for several field problems. Based on these studies and other field applications of the model a number of points have been observed that are of practical interest; these points are separately listed. Key words: numerical analysis, retaining wall, anchor, arching, soilstructure interaction, deflection.
Algorithm 876
Authors: Atkinson Kendall E. , Shampine Lawrence F. 
Published: July 2008

We present here the algorithms and user interface of a
Matlab
program, Fie, that solves numerically Fredholm integral equations of the second kind on an interval [
a
,
b
] to a specified, modest accuracy. The kernel function
K
(
s
,
t
) is moderately smooth on [
a
,
b
] ×[
a
,
b
] except possibly across the diagonal
s
=
t
. If the interval is finite, provides for kernel functions that behave in a variety of ways across the diagonal, that is,
K
(
s
,
t
) may be smooth, have a discontinuity in a low-order derivative, have a logarithmic singularity, or have an algebraic singularity. Fie also solves a large class of integral equations with moderately smooth kernel function on [0, ∞ ).
Fixed Points and Stability in Neutral Stochastic Differential Equations with Variable Delays
Authors: Wu Meng , Huang Nan-jing , Zhao Chang-Wen 
Published: July 2008

AbstractWe consider the mean square asymptotic stability of a generalized linear neutral stochastic differential equation with variable delays by using the fixed point theory. An asymptotic mean square stability theorem with a necessary and sufficient condition is proved, which improves and generalizes some results due to Burton, Zhang and Luo. Two examples are also given to illustrate our results.
Resveratrol Prevents Estrogen-DNA Adduct Formation and Neoplastic Transformation in MCF-10F Cells
Authors: Lu Fang , Zahid Muhammad , Wang Cheng , Saeed Muhammad , Cavalieri Ercole L. , Rogan Eleanor G. 
Published: July 2008

AbstractExposure to estrogens is a risk factor for breast cancer. Specific estrogen metabolites may initiate breast cancer and other cancers. Genotoxicity may be caused by cytochrome P450 (CYP)–mediated oxidation of catechol estrogens to quinones that react with DNA to form depurinating estrogen-DNA adducts. CYP1B1 favors quinone formation by catalyzing estrogen 4-hydroxylation, whereas NAD(P)H quinone oxidoreductase 1 (NQO1) catalyzes the protective reduction of quinones to catechols. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces CYP1B1 expression through the aryl hydrocarbon receptor (AhR). Resveratrol has anticancer effects in diverse in vitro and in vivo systems and is an AhR antagonist that decreases CYP expression but induces NQO1 expression. The chemopreventive effect of resveratrol on breast cancer initiation was investigated in MCF-10F cells. Its effects on estrogen metabolism and formation of estrogen-DNA adducts were analyzed in culture medium by high-performance liquid chromatography, whereas its effects on CYP1B1 and NQO1 were determined by immunoblotting and immunostaining. The antitransformation effects of resveratrol were also examined. TCDD induced expression of CYP1B1 and its redistribution in the nucleus and cytoplasm. Concomitant treatment with resveratrol dose-dependently suppressed TCDD-induced expression of CYP1B1, mainly in the cytoplasm. Resveratrol dose- and time-dependently induced expression of NQO1. NQO1 is mainly in the perinuclear membrane of control cells, but resveratrol induced NQO1 and its intracellular redistribution, which involves nuclear translocation of nuclear factor erythroid 2–related factor 2. Resveratrol decreased estrogen metabolism and blocked formation of DNA adducts in cells treated with TCDD and/or estradiol. Resveratrol also suppressed TCDD and/or estradiol-induced cell transformation. Thus, resveratrol can prevent breast cancer initiation by blocking multiple sites in the estrogen genotoxicity pathway.
Importance of Using Observations of Mixing Depths in order to Avoid Large Prediction Errors by a Transport and Dispersion Model
Authors: White J. M. , Bowers J. F. , Hanna S. R. , Lundquist J. K. 
Published: July 2008

Abstract
The mixing depth of the boundary layer is an input to most atmospheric transport and dispersion (ATD) models, which obtain mixing depths in one of four ways: 1) observations by radiosondes, sodars, or other devices; 2) simulations by regional or mesoscale meteorological models; 3) parameterizations based on boundary layer similarity theory; or 4) climatological averages. This paper describes a situation during a field experiment when exceptionally low mixing depths persisted in the morning and led to relatively high observed tracer concentrations. The low mixing depths were caused by synoptic effects associated with a nearby stationary front and the outflow from a mesoscale thunderstorm complex located 20–50 km away. For the same time period, the ATD model-parameterized mixing depth was a factor of 5–10 higher, leading to predicted concentrations that were less than the observations by a factor of 5–10. The synoptic situation is described and local radiosonde and radar observations of mixing depth are presented, including comparisons with other more typical days. Time series of local observations of near-surface sensible heat fluxes are also plotted to demonstrate the suppression of turbulence by negative sensible heat fluxes during the period in question.
Bioassay Research Methodology: Measuring CRH in Pregnancy
Authors: Latendresse Gwen , Ruiz Roberta Jeanne 
Published: July 2008

Background. There are documented associations between elevated maternal corticotropin-releasing hormone (CRH) levels and adverse pregnancy outcomes. However, reports of these findings often lack sufficient detail and rationale regarding the bioassay methodology. This shortcoming can be problematic for researchers who do not possess in-depth laboratory sciences knowledge but who want to include bioassays in their investigations or to evaluate published reports. The quality and reliability of CRH measurement results can be significantly affected by variables encountered during sample collection, processing, storage, and bioassay. Thus, it is important to establish research laboratory protocols that are based on well-informed rationales and to carefully consider and control for relevant variables. Approach. A synthesis of laboratory sciences literature regarding variables affecting CRH measurement in pregnancy is presented. Additionally, consultation with experienced researchers provided an in-depth understanding of CRH measurement. From these sources, a laboratory protocol for clinical research was developed. Results. Multiple variables that are specific to the reliability of CRH measurement in pregnancy have been identified. These include sample collection methods, sample processing, sample integrity, sample storage, and the actual assay selected. Conclusion. The reliability of CRH measurements can be significantly improved by identifying and controlling for variables encountered during sample collection, processing, storage, and bioassay. Adequate methodological details are difficult to glean solely from the published literature, thus consultation with well-informed researchers is necessary. A protocol for CRH bioassay in clinical research is proposed.
Analysis of the linker for activation of T cells and the linker for activation of B cells in natural killer cells reveals a novel signaling cassette, dual usage in ITAM signaling, and influence on development of the Ly49 repertoire
Authors: Whittaker Gillian C. , Burshtyn Deborah N. , Orr Selinda J. , Quigley Laura , Hodge Deborah L. , Pascal Véronique , Zhang Weiguo , McVicar Daniel W. 
Published: July 2008

AbstractThe linker for activation of T cells (LAT) and the linker for activation of B cells (LAB/NTAL/LAT2) are integral proteins in receptor coupling to downstream events. Both proteins are expressed in natural killer (NK) cells and LAT is phosphorylated during target cell interactions or ligation of the immunoreceptor tyrosine-based activation motif (ITAM)–coupled CD16. Regardless, Lat−/− mice exhibit normal natural and antibody-mediated killing. Here we place both LAT and LAB in the DAP12 pathway of NK cells. Moreover, we unveil a LAT-independent pathway that requires expression of Syk. Mice lacking either LAT or LAB have a skewed Ly49 repertoire, and activated NK cells from Lat−/− mice have reduced responses to the ITAM-coupled receptor NK1.1. In contrast, resting Lat−/− NK cells show intact NK1.1 responses, whereas NK cells without LAB are hyperactive. Elimination of both adaptors severely reduces NK1.1 signaling under both conditions. Together these data show that NK ITAMs preferentially use a signaling cassette regulated by interplay between LAT and LAB. Activation by interleukin-2 causes a shift to greater dependency on LAT due to suppression of Syk signaling. The overlapping use of multiple adaptors permits fine-tuning of NK-cell ITAM responses over the course of an immune response.