bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transcriptional Profiling of Staphylococcus aureus During Growth in 2 M NaCl Leads to Clarification of Physiological Roles for Kdp and Ktr K
+
Uptake Systems
Authors: Price-Whelan Alexa , Poon Chun Kit , Benson Meredith A. , Eidem Tess T. , Roux Christelle M. , Boyd Jeffrey M. , Dunman Paul M. , Torres Victor J. , Krulwich Terry A. 
Published: August 2013

ABSTRACT

Staphylococcus aureus
exhibits an unusually high level of osmotolerance and Na
+
tolerance, properties that support survival in various host niches and in preserved foods. The genetic basis of these traits is not well understood. We compared the transcriptional profiles of
S. aureus
grown in complex medium with and without 2 M NaCl. The stimulon for growth in high-osmolality media and Na
+
included genes involved in uptake of K
+
, other compatible solutes, sialic acid, and sugars; capsule biosynthesis; and amino acid and central metabolism. Quantitative PCR analysis revealed that the loci responded differently from each other to high osmolality imposed by elevated NaCl versus sucrose. High-affinity K
+
uptake (
kdp
) genes and capsule biosynthesis (
cap5
) genes required the two-component system KdpDE for full induction by osmotic stress, with
kdpA
induced more by NaCl and
cap5B
induced more by sucrose. Focusing on K
+
importers, we identified three
S. aureus g
enes belonging to the lower-affinity Trk/Ktr family that encode two membrane proteins (KtrB and KtrD) and one accessory protein (KtrC). In the absence of osmotic stress, the
ktr
gene transcripts were much more abundant than the
kdpA
transcript. Disruption of
S. aureus kdpA
caused a growth defect under low-K
+
conditions, disruption of
ktrC
resulted in a significant defect in 2 M NaCl, and a Δ
ktrC
Δ
kdpA
double mutant exhibited both phenotypes. Protective effects of
S. aureus
Ktr transporters at elevated NaCl are consistent with previous indications that both Na
+
and osmolality challenges are mitigated by the maintenance of a high cytoplasmic K
+
concentration.

IMPORTANCE
There is general agreement that the osmotolerance and Na
+
tolerance of
Staphylococcus aureus
are unusually high for a nonhalophile and support its capacity for human colonization, pathogenesis, and growth in food. Nonetheless, the molecular basis for these properties is not well defined. The genome-wide response of
S. aureus
to a high concentration, 2 M, of NaCl revealed the upregulation of expected genes, such as those for transporters of compatible solutes that are widely implicated in supporting osmotolerance. A high-affinity potassium uptake system, KdpFABC, was upregulated, although it generally plays a physiological role under very low K
+
conditions. At higher K
+
concentrations, a lower-affinity and more highly expressed type of K
+
transporter system, Ktr transporters, was shown to play a significant role in high Na
+
tolerance. This study illustrates the importance of the K
+
status of the cell for tolerance of Na
+
by
S. aureus
and underscores the importance of monovalent cation cycles in this pathogen.
Emergence of Epidemic Multidrug-Resistant Enterococcus faecium from Animal and Commensal Strains
Authors: Lebreton François , van Schaik Willem , Manson McGuire Abigail , Godfrey Paul , Griggs Allison , Mazumdar Varun , Corander Jukka , Cheng Lu , Saif Sakina , Young Sarah , Zeng Qiandong , Wortman Jennifer , Birren Bruce , Willems Rob J. L. , Earl Ashlee M. , Gilmore Michael S. 
Published: August 2013

ABSTRACT

Enterococcus faecium
, natively a gut commensal organism, emerged as a leading cause of multidrug-resistant hospital-acquired infection in the 1980s. As the living record of its adaptation to changes in habitat, we sequenced the genomes of 51 strains, isolated from various ecological environments, to understand how
E. faecium
emerged as a leading hospital pathogen. Because of the scale and diversity of the sampled strains, we were able to resolve the lineage responsible for epidemic, multidrug-resistant human infection from other strains and to measure the evolutionary distances between groups. We found that the epidemic hospital-adapted lineage is rapidly evolving and emerged approximately 75 years ago, concomitant with the introduction of antibiotics, from a population that included the majority of animal strains, and not from human commensal lines. We further found that the lineage that included most strains of animal origin diverged from the main human commensal line approximately 3,000 years ago, a time that corresponds to increasing urbanization of humans, development of hygienic practices, and domestication of animals, which we speculate contributed to their ecological separation. Each bifurcation was accompanied by the acquisition of new metabolic capabilities and colonization traits on mobile elements and the loss of function and genome remodeling associated with mobile element insertion and movement. As a result, diversity within the species, in terms of sequence divergence as well as gene content, spans a range usually associated with speciation.

IMPORTANCE
Enterococci, in particular vancomycin-resistant
Enterococcus faecium
, recently emerged as a leading cause of hospital-acquired infection worldwide. In this study, we examined genome sequence data to understand the bacterial adaptations that accompanied this transformation from microbes that existed for eons as members of host microbiota. We observed changes in the genomes that paralleled changes in human behavior. An initial bifurcation within the species appears to have occurred at a time that corresponds to the urbanization of humans and domestication of animals, and a more recent bifurcation parallels the introduction of antibiotics in medicine and agriculture. In response to the opportunity to fill niches associated with changes in human activity, a rapidly evolving lineage emerged, a lineage responsible for the vast majority of multidrug-resistant
E. faecium
infections.
Load-Dependent Assembly of the Bacterial Flagellar Motor
Authors: Tipping Murray J. , Delalez Nicolas J. , Lim Ren , Berry Richard M. , Armitage Judith P. 
Published: August 2013

ABSTRACT
It is becoming clear that the bacterial flagellar motor output is important not only for bacterial locomotion but also for mediating the transition from liquid to surface living. The output of the flagellar motor changes with the mechanical load placed on it by the external environment: at a higher load, the motor runs more slowly and produces higher torque. Here we show that the number of torque-generating units bound to the flagellar motor also depends on the external mechanical load, with fewer stators at lower loads. Stalled motors contained at least as many stators as rotating motors at high load, indicating that rotation is unnecessary for stator binding. Mutant stators incapable of generating torque could not be detected around the motor. We speculate that a component of the bacterial flagellar motor senses external load and mediates the strength of stator binding to the rest of the motor.

IMPORTANCE
The transition between liquid living and surface living is important in the life cycles of many bacteria. In this paper, we describe how the flagellar motor, used by bacteria for locomotion through liquid media and across solid surfaces, is capable of adjusting the number of bound stator units to better suit the external load conditions. By stalling motors using external magnetic fields, we also show that rotation is not required for maintenance of stators around the motor; instead, torque production is the essential factor for motor stability. These new results, in addition to previous data, lead us to hypothesize that the motor stators function as mechanosensors as well as functioning as torque-generating units.
Ferrous Iron Is a Significant Component of Bioavailable Iron in Cystic Fibrosis Airways
Authors: Hunter Ryan C. , Asfour Fadi , Dingemans Jozef , Osuna Brenda L. , Samad Tahoura , Malfroot Anne , Cornelis Pierre , Newman Dianne K. 
Published: August 2013

ABSTRACT

Chronic, biofilm-like infections by the opportunistic pathogen
Pseudomonas aeruginosa
are a major cause of mortality in cystic fibrosis (CF) patients. While much is known about
P. aeruginosa
from laboratory studies, far less is understood about what it experiences
in vivo
. Iron is an important environmental parameter thought to play a central role in the development and maintenance of
P. aeruginosa
infections, for both anabolic and signaling purposes. Previous studies have focused on ferric iron [Fe(III)] as a target for antimicrobial therapies; however, here we show that ferrous iron [Fe(II)] is abundant in the CF lung (~39 µM on average for severely sick patients) and significantly correlates with disease severity (ρ = −0.56,
P
= 0.004), whereas ferric iron does not (ρ = −0.28,
P
= 0.179). Expression of the
P. aeruginosa
genes
bqsRS
, whose transcription is upregulated in response to Fe(II), was high in the majority of patients tested, suggesting that increased Fe(II) is bioavailable to the infectious bacterial population. Because limiting Fe(III) acquisition inhibits biofilm formation by
P. aeruginosa
in various oxic
in vitro
systems, we also tested whether interfering with Fe(II) acquisition would improve biofilm control under anoxic conditions; concurrent sequestration of both iron oxidation states resulted in a 58% reduction in biofilm accumulation and 28% increase in biofilm dissolution, a significant improvement over Fe(III) chelation treatment alone. This study demonstrates that the chemistry of infected host environments coevolves with the microbial community as infections progress, which should be considered in the design of effective treatment strategies at different stages of disease.

IMPORTANCE
Iron is an important environmental parameter that helps pathogens thrive in sites of infection, including those of cystic fibrosis (CF) patients. Ferric iron chelation therapy has been proposed as a novel therapeutic strategy for CF lung infections, yet until now, the iron oxidation state has not been measured in the host. In studying mucus from the infected lungs of multiple CF patients from Europe and the United States, we found that ferric and ferrous iron change in concentration and relative proportion as infections progress; over time, ferrous iron comes to dominate the iron pool. This information is relevant to the design of novel CF therapeutics and, more broadly, to developing accurate models of chronic CF infections.
Is the interpretation of rapid antigen testing for respiratory syncytial virus as simple as positive or negative?
Authors: Walsh Paul , Overmyer Christina , Hancock Christine , Heffner Jacquelyn , Walker Nicholas , Nguyen Thienphuc , Shanholtzer Lucas , Caldera Enrique , Pusavat James , Mordechai Eli , Adelson Martin E , Iacono Kathryn T 
Published: August 2013

ObjectiveTo measure the performance characteristics of an immunochromatographic rapid antigen test for respiratory syncytial virus (RSV) and determine how its interpretation should be contextualised in patients presenting to the emergency department (ED) with bronchiolitis.DesignDiagnostic accuracy study of a rapid RSV test.SettingCounty hospital ED.InterventionWe took paired nasal samples from consecutively enrolled infants with bronchiolitis and tested them with a rapid immunochromatographic antigen test and reverse transcriptase PCR gold standard.Outcome measuresSensitivity, specificity, the effect of point prevalence, clinical findings and overall context on predictive values. We used these to construct a graphical contextual model to show how the results of RSV antigen tests from infants presenting within 24 h should influence interpretation of subsequent antigen tests.ResultsWe analysed 607 patients. The sensitivity and specificity for immunochromatographic testing was 79.4% (95% CI 73.9% to 84.2%) and 67.1% (95% CI 61.9% to 72%) respectively. We found little evidence of spectrum bias. In our contextual model the best predictor of a positive RT-PCR test was a positive antigen test OR 5.47 (95% CI 3.65 to 8.18) and the number of other infants having positive tests within 24 h OR 1.48 (95% CI 1.26 to 1.72) per infant. Increasing numbers presenting to the ED with bronchiolitis in a given day increases the probability of RSV infection.ConclusionsThe RSV antigen test we examined had modest performance characteristics. The results of the antigen test should be interpreted in the context of the results of previous tests.
Fellowships in international emergency medicine in the USA: a comparative survey of program directors’ and fellows’ perspectives on the curriculum
Authors: Jacquet Gabrielle A , Vu Alexander , Ewen William B , Hansoti Bhakti , Andescavage Steven , Price David , Suter Robert E , Bayram Jamil D 
Published: August 2013

Abstract

Objective
Experts have proposed core curriculum components for international emergency medicine (IEM) fellowships. This study examined perceptions of program directors (PDs) and fellows on whether IEM fellowships cover these components, whether their perspectives differ and the barriers preventing fellowships from covering them.

Methods
From 1 November 2011 to 30 November 2011, a survey was administered to PDs, current fellows and recent graduates of the 34 US IEM fellowships. Respondents quantified their fellowship experience in six proposed core curriculum areas: emergency medicine (EM) systems development, EM education, humanitarian assistance, public health, emergency medical services and disaster medicine. Analysis was performed regarding what per cent of programmes fulfil the six curriculum areas. A paired t test determined the difference between PDs’ and fellows’ responses. Agreement between PDs and fellows within the same programme was determined using a κ statistic.

Results
Only 1/18 (6%) (according to fellows) to 2/24 (8%) (according to PDs) of programmes expose fellows to all six components. PDs consistently reported higher exposure than fellows. The difference in mean score between PDs and fellows was statistically significant (p&lt;0.05) in three of the 6 (50%) core curriculum elements: humanitarian aid, public health and disaster medicine. Per cent agreement between PDs and fellows within each programmes ranged from poor to fair.

Conclusions
While IEM fellowships have varying structure, this study highlights the importance of further discussion between PDs and fellows regarding delineation and objectives of core curriculum components. Transparent curricula and open communication between PDs and fellows may reduce differences in reported experiences.
Novel Treatment for Mantle Cell Lymphoma Including Therapy-Resistant Tumor by NF-κB and mTOR Dual-Targeting Approach
Authors: Chaturvedi Nagendra K. , Rajule Rajkumar N. , Shukla Ashima , Radhakrishnan Prakash , Todd Gordon L. , Natarajan Amarnath , Vose Julie M. , Joshi Shantaram S. 
Published: August 2013

Abstract
Mantle cell lymphoma (MCL) is one of the most aggressive B-cell non-Hodgkin lymphomas with a median survival of approximately five years. Currently, there is no curative therapy available for refractory MCL because of relapse from therapy-resistant tumor cells. The NF-κB and mTOR pathways are constitutively active in refractory MCL leading to increased proliferation and survival. Targeting these pathways is an ideal strategy to improve therapy for refractory MCL. Therefore, we investigated the in vitro and in vivo antilymphoma activity and associated molecular mechanism of action of a novel compound, 13-197, a quinoxaline analog that specifically perturbs IκB kinase (IKK) β, a key regulator of the NF-κB pathway. 13-197 decreased the proliferation and induced apoptosis in MCL cells including therapy-resistant cells compared with control cells. Furthermore, we observed downregulation of IκBα phosphorylation and inhibition of NF-κB nuclear translocation by 13-197 in MCL cells. In addition, NF-κB–regulated genes such as cyclin D1, Bcl-XL, and Mcl-1 were downregulated in 13-197–treated cells. In addition, 13-197 inhibited the phosphorylation of S6K and 4E-BP1, the downstream molecules of mTOR pathway that are also activated in refractory MCL. Further, 13-197 reduced the tumor burden in vivo in the kidney, liver, and lungs of therapy-resistant MCL-bearing nonobese diabetic severe-combined immunodeficient (NOD/SCID) mice compared with vehicle-treated mice; indeed, 13-197 significantly increased the survival of MCL-transplanted mice. Together, results suggest that 13-197 as a single agent disrupts the NF-κB and mTOR pathways leading to suppression of proliferation and increased apoptosis in malignant MCL cells including reduction in tumor burden in mice. Mol Cancer Ther; 12(10); 2006–17. ©2013 AACR.
Molecular Radiotherapy Using Cleavable Radioimmunoconjugates That Target EGFR and γH2AX
Authors: Cornelissen Bart , Waller Andrew , Able Sarah , Vallis Katherine A. 
Published: August 2013

Abstract
Many anticancer therapies, including ionizing radiation (IR), cause cytotoxicity through generation of DNA double-strand breaks (DSB). Delivery of therapeutic radionuclides to DNA DSB sites can amplify this DNA damage, for additional therapeutic gain. Herein, we report on two radiopharmaceuticals, radiolabeled with the Auger electron emitter 111In, with dual specificity for both the intranuclear, DNA damage repair signaling protein γH2AX and the EGF receptor (EGFR). The EGFR ligand EGF was conjugated to a fluorophore- or 111In-labeled anti-γH2AX antibody, linked via a nuclear localization sequence (NLS) to ensure nuclear translocation. EGF conjugation was achieved either through a noncleavable PEG linker (PEO6) or a cleavable disulfide bond. Both conjugates selectively bound EGFR on fixed cells and γH2AX in cell extracts. Both compounds enter EGFR-expressing cells in an EGF/EGFR-dependent manner. However, only the cleavable compound was seen to associate with γH2AX foci in the nuclei of irradiated cells. Intracellular retention of the cleavable compound was prolonged in γH2AX-expressing cells. Clonogenic survival was significantly reduced when cells were exposed to IR (to induce γH2AX) plus 111In-labeled cleavable compound compared to either alone and compared to nonspecific controls. In vivo, uptake of 111In-labeled cleavable compound in MDA-MB-468 xenografts in athymic mice was 2.57 ± 0.47 percent injected dose/g (%ID/g) but increased significantly to 6.30 ± 1.47%ID/g in xenografts where γH2AX was induced by IR (P &lt; 0.01). This uptake was dependent on EGF/EGFR and anti-γH2AX/γH2AX interactions. We conclude that tumor-specific delivery of radiolabeled antibodies directed against intranuclear epitopes is possible using cleavable antibody–peptide conjugates. Mol Cancer Ther; 12(11); 2472–82. ©2013 AACR.
Vitamin E δ-Tocotrienol Prolongs Survival in the LSL-KrasG12D/+;LSL-Trp53R172H/+;Pdx-1-Cre (KPC) Transgenic Mouse Model of Pancreatic Cancer
Authors: Husain Kazim , Centeno Barbara A. , Chen Dung-Tsa , Hingorani Sunil R. , Sebti Said M. , Malafa Mokenge P. 
Published: August 2013

Abstract
Previous work has shown that vitamin E δ-tocotrienol (VEDT) prolongs survival and delays progression of pancreatic cancer in the LSL-KrasG12D/+;Pdx-1-Cre mouse model of pancreatic cancer. However, the effect of VEDT alone or in combination with gemcitabine in the more aggressive LSL-KrasG12D/+;LSL-Trp53R172H/+;Pdx-1-Cre (KPC) mouse model is unknown. Here, we studied the effects of VEDT and the combination of VEDT and gemcitabine in the KPC mice. KPC mice were randomized into four groups: (i) vehicle [olive oil, 1.0 mL/kg per os twice a day and PBS 1.0 mL/kg intrapertoneally (i.p.) twice a week], (ii) gemcitabine (100 mg/kg i.p. twice a week), (iii) VEDT (200 mg/kg per os twice a day), and (iv) gemcitabine + VEDT. Mice received treatment until they displayed symptoms of impending death from pancreatic cancer, at which point animals were euthanized. At 16 weeks, survival was 10% in the vehicle group, 30% in the gemcitabine group, 70% in the VEDT group (P &lt; 0.01), and 90% in the VEDT combined with gemcitabine group (P &lt; 0.05). VEDT alone and combined with gemcitabine resulted in reversal of epithelial-to-mesenchymal transition in tumors. Biomarkers of apoptosis (plasma CK18), PARP1 cleavage, and Bax expression were more greatly induced in tumors subjected to combined treatment versus individual treatment. Combined treatment induced cell-cycle inhibitors (p27Kip1 and p21Cip1) and inhibited VEGF, vascularity (CD31), and oncogenic signaling (pAKT, pMEK, and pERK) greater than individual drugs. No significant differences in body weight gain between drug treatment and control mice were observed. These results strongly support further investigation of VEDT alone and in combination with gemcitabine for pancreatic cancer prevention and treatment. Cancer Prev Res; 6(10); 1074–83. ©2013 AACR.
Prospective Quality Initiative to Maximize Dysphagia Screening Reduces Hospital-Acquired Pneumonia Prevalence in Patients With Stroke
Authors: Titsworth W. Lee , Abram Justine , Fullerton Amy , Hester Jeannette , Guin Peggy , Waters Michael F. , Mocco J 
Published: August 2013

Background and Purpose—
Dysphagia can lead to pneumonia and subsequent death after acute stroke. However, no prospective study has demonstrated reduced pneumonia prevalence after implementation of a dysphagia screen.

Methods—
We performed a single-center prospective interrupted time series trial of a quality initiative to improve dysphagia screening. Subjects included all patients with ischemic or hemorrhagic stroke admitted to our institution over 42 months with a 31-month (n=1686) preintervention and an 11-month (n=648) postintervention period. The intervention consisted of a dysphagia protocol with a nurse-administered bedside dysphagia screen and a reflexive rapid clinical swallow evaluation by a speech pathologist.

Results—

The dysphagia initiative increased the percentage of patients with stroke screened from 39.3% to 74.2% (
P
<0.001). Furthermore, this initiative coincided with a drop in hospital-acquired pneumonia from 6.5% to 2.8% among patients with stroke (
P
<0.001). Patients admitted postinitiative had 57% lower odds of pneumonia, after controlling for multiple confounds (odds ratio=0.43; confidence interval, 0.255–0.711;
P
=0.0011). The best predictors of pneumonia were stroke type (
P
<0.0001), oral intake status (
P
<0.0001), dysphagia screening status (
P
=0.0037), and hospitalization before the beginning of the quality improvement initiative (
P
=0.0449).

Conclusions—
A quality improvement initiative using a nurse-administered bedside screen with rapid bedside swallow evaluation by a speech pathologist improves screening compliance and correlates with decreased prevalence of pneumonia among patients with stroke.