bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reference intervals for common coagulation tests of preterm infants (CME)
Authors: Christensen Robert D. , Baer Vickie L. , Lambert Diane K. , Henry Erick , Ilstrup Sarah J. , Bennett Sterling T. 
Published: July 2013

Background:Fresh‐frozen plasma (FFP) is sometimes administered to nonbleeding preterm neonates who are judged to be at risk for bleeding because they have abnormal coagulation tests. The benefits/risks of this practice are not well defined. One limitation to progress is lack of reference intervals for the common coagulation tests, thus limiting precision about whether coagulation tests are indeed abnormal.Study Design and Methods:In a sequential observational study, fetal blood was drawn at preterm birth (≤34 weeks) from the umbilical vein near the placenta. Fibrinogen, prothrombin time, activated partial thromboplastin time, D‐dimer, platelet (PLT) count, and mean PLT volume were measured. Reference intervals were constructed using 5th and 95th percentile values. Associations were then sought between abnormal coagulation values at birth and bleeding problems identified during the first week.Results:Coagulation tests were drawn at 175 preterm deliveries and the results were organized into reference intervals by gestational age. No abnormal coagulation value, either alone or in combination, predicted hemorrhage (intraventricular, gastrointestinal, or pulmonary) during the first week. However, fibrinogen exceeding the 95th percentile was associated with evidence of in utero infection/inflammation (correlations with elevated C‐reactive protein, p < 0.01, and elevated immature to total neutrophil ratio, p < 0.001).Conclusions:Abnormal coagulation values at preterm birth do not predict bleeding during the first week. This suggests to us that bleeding in the days after preterm birth is not generally the result of in utero coagulopathy. These findings bring into question the value of coagulation screening of nonbleeding preterm infants and prophylactic FFP administration to those with abnormal values.
The mechanism underlying maintenance of the endocochlear potential by the K+ transport system in fibrocytes of the inner ear
Authors: Adachi Naoko , Yoshida Takamasa , Nin Fumiaki , Ogata Genki , Yamaguchi Soichiro , Suzuki Toshihiro , Komune Sizuo , Hisa Yasuo , Hibino Hiroshi , Kurachi Yoshihisa 
Published: July 2013

Key points
The endocochlear potential (EP) of +80 mV in cochlear endolymph is essential for audition and controlled by K+ transport across the lateral cochlear wall composed of two epithelial barrier layers, the syncytium containing the fibrocytes and the marginal cells.
The EP depends upon the diffusion potential elicited by a large K+ gradient across the apical surface of the syncytium.
We examined by electrophysiological approaches an involvement of Na+,K+‐ATPase, which occurs at the syncytium's basolateral surface comprising the fibrocytes’ membranes and would mediate K+ transport across the lateral wall, in maintenance of the EP.
We show that the Na+,K+‐ATPase sustains the syncytium's high [K+] that is crucial for the K+ gradient across the apical surface of the syncytium.
The results help us better understand the mechanism underlying the establishment of the EP as well as the pathophysiological process for deafness induced by dysfunction of the ion transport apparatus.
Abstract  The endocochlear potential (EP) of +80 mV in the scala media, which is indispensable for audition, is controlled by K+ transport across the lateral cochlear wall. This wall includes two epithelial barriers, the syncytium and the marginal cells. The former contains multiple cell types, such as fibrocytes, which are exposed to perilymph on their basolateral surfaces. The apical surfaces of the marginal cells face endolymph. Between the two barriers lies the intrastrial space (IS), an extracellular space with a low K+ concentration ([K+]) and a potential similar to the EP. This intrastrial potential (ISP) dominates the EP and represents the sum of the diffusion potential elicited by a large K+ gradient across the apical surface of the syncytium and the syncytium's potential, which is slightly positive relative to perilymph. Although a K+ transport system in fibrocytes seems to contribute to the EP, the mechanism remains uncertain. We examined the electrochemical properties of the lateral wall of guinea pigs with electrodes sensitive to potential and K+ while perfusing into the perilymph of the scala tympani blockers of Na+,K+‐ATPase, the K+ pump thought to be essential to the system. Inhibiting Na+,K+‐ATPase barely affected [K+] in the IS but greatly decreased [K+] within the syncytium, reducing the K+ gradient across its apical surface. The treatment hyperpolarized the syncytium only moderately. Consequently, both the ISP and the EP declined. Fibrocytes evidently use the Na+,K+‐ATPase to achieve local K+ transport, maintaining the syncytium's high [K+] that is crucial for the K+ diffusion underlying the positive ISP.
Mutagenesis Mapping of the Protein-Protein Interaction Underlying FusB-Type Fusidic Acid Resistance
Authors: Cox Georgina , Edwards Thomas A. , O'Neill Alex J. 
Published: July 2013

ABSTRACT

FusB-type proteins represent the predominant mechanism of resistance to fusidic acid in staphylococci and act by binding to and modulating the function of the drug target (elongation factor G [EF-G]). To gain further insight into this antibiotic resistance mechanism, we sought to identify residues important for the interaction of FusB with EF-G and thereby delineate the binding interface within the FusB–EF-G complex. Replacement with alanine of any one of four conserved residues within the C-terminal domain of FusB (F
156
, K
184
, Y
187
, and F
208
) abrogated the ability of the protein to confer resistance to fusidic acid; the purified mutant proteins also lost the ability to bind
S. aureus
EF-G
in vitro. E. coli
EF-G, which is not ordinarily able to bind FusB-type proteins, was rendered competent for binding to FusB following deletion of a 3-residue tract (
529
SNP
531
) from domain IV of the protein. This study has identified key regions of both FusB and EF-G that are important for the interaction between the proteins, findings which corroborate our previous
in silico
prediction for the architecture of the complex formed between the resistance protein and the drug target (G. Cox, G. S. Thompson, H. T. Jenkins, F. Peske, A. Savelsbergh, M. V. Rodnina, W. Wintermeyer, S. W. Homans, T. A. Edwards, and A. J. O'Neill, Proc. Natl. Acad. Sci. U. S. A. 109:2102-2107, 2012).
In Vivo
Studies Suggest that Induction of VanS-Dependent Vancomycin Resistance Requires Binding of the Drug to
d
-Ala-
d
-Ala Termini in the Peptidoglycan Cell Wall
Authors: Kwun Min Jung , Novotna Gabriela , Hesketh Andrew R. , Hill Lionel , Hong Hee-Jeon 
Published: July 2013

ABSTRACT

VanRS two-component regulatory systems are key elements required for the transcriptional activation of inducible vancomycin resistance genes in bacteria, but the precise nature of the ligand signal that activates these systems has remained undefined. Using the resistance system in
Streptomyces coelicolor
as a model, we have undertaken a series of
in vivo
studies which indicate that the VanS sensor kinase in VanB-type resistance systems is activated by vancomycin in complex with the
d
-alanyl-
d
-alanine (
d
-Ala-
d
-Ala) termini of cell wall peptidoglycan (PG) precursors. Complementation of an essential
d
-Ala-
d
-Ala ligase activity by constitutive expression of
vanA
encoding a bifunctional
d
-Ala-
d
-Ala and
d
-alanyl-
d
-lactate (
d
-Ala-
d
-Lac) ligase activity allowed construction of strains that synthesized variable amounts of PG precursors containing
d
-Ala-
d
-Ala. Assays quantifying the expression of genes under VanRS control showed that the response to vancomycin in these strains correlated with the abundance of
d
-Ala-
d
-Ala-containing PG precursors; strains producing a lower proportion of PG precursors terminating in
d
-Ala-
d
-Ala consistently exhibited a lower response to vancomycin. Pretreatment of wild-type cells with vancomycin or teicoplanin to saturate and mask the
d
-Ala-
d
-Ala binding sites in nascent PG also blocked the transcriptional response to subsequent vancomycin exposure, and desleucyl vancomycin, a vancomycin analogue incapable of interacting with
d
-Ala-
d
-Ala residues, failed to induce
van
gene expression. Activation of resistance by a vancomycin–
d
-Ala-
d
-Ala PG complex predicts a limit to the proportion of PG that can be derived from precursors terminating in
d
-Ala-
d
-Lac, a restriction also enforced by the bifunctional activity of the VanA ligase.
Colistin Resistance in a Clinical Acinetobacter baumannii Strain Appearing after Colistin Treatment: Effect on Virulence and Bacterial Fitness
Authors: López-Rojas Rafael , McConnell Michael J. , Jiménez-Mejías Manuel Enrique , Domínguez-Herrera Juan , Fernández-Cuenca Felipe , Pachón Jerónimo 
Published: July 2013

ABSTRACT

The fitness and virulence costs associated with the clinical acquisition of colistin resistance by
Acinetobacter baumannii
were evaluated. The growth of strain CR17 (colistin resistant) was less than that of strain CS01 (colistin susceptible) when the strains were grown in competition (72-h competition index, 0.008). In a murine sepsis model, CS01 and CR17 reached spleen concentrations when coinfecting of 9.31 and 6.97 log
10
CFU/g, respectively, with an
in vivo
competition index of 0.016. Moreover, CS01 was more virulent than CR17 with respect to mortality and time to death.
Azole Heteroresistance in Cryptococcus neoformans: Emergence of Resistant Clones with Chromosomal Disomy in the Mouse Brain during Fluconazole Treatment
Authors: Sionov Edward , Chang Yun C. , Kwon-Chung Kyung J. 
Published: July 2013

ABSTRACT

We have previously reported that
Cryptococcus neoformans
strains are innately heteroresistant to fluconazole
in vitro
, producing minor, highly resistant subpopulations due to adaptive formation of disomic chromosomes. Using a mouse model, we assessed the emergence of heteroresistant clones in the brain during fluconazole treatment and found that the occurrence of heteroresistant clones
in vivo
with chromosomal disomy is strain dependent. Interestingly, emergence of heteroresistant clones
in vivo
was unrelated to the strain's MIC to fluconazole.
Impaired Virulence and Fitness of a Colistin-Resistant Clinical Isolate of Acinetobacter baumannii in a Rat Model of Pneumonia
Authors: Hraiech Sami , Roch Antoine , Lepidi Hubert , Atieh Thérèse , Audoly Gilles , Rolain Jean-Marc , Raoult Didier , Brunel Jean-Michel , Papazian Laurent , Brégeon Fabienne 
Published: July 2013

ABSTRACT

We compared the fitness and lung pathogenicity of two isogenic clinical isolates of
Acinetobacter baumannii
, one resistant (ABCR) and the other susceptible (ABCS) to colistin.
In vitro
, ABCR exhibited slower growth kinetics than ABCS. In a rat model of pneumonia, ABCR was associated with less pronounced signs of infection (lung bacterial count, systemic dissemination, and lung damage) and a better outcome (ABCR and ABCS mortality rates, 20 and 50%, respectively [
P
= 0.03]).
Genetic Basis for
In Vitro
and
In Vivo
Resistance to Lincosamides, Streptogramins A, and Pleuromutilins (LS
A
P Phenotype) in Enterococcus faecium
Authors: Isnard Christophe , Malbruny Brigitte , Leclercq Roland , Cattoir Vincent 
Published: July 2013

ABSTRACT

As opposed to
Enterococcus faecalis
, which is intrinsically resistant to lincosamides, streptogramins A, and pleuromutilins (LS
A
P phenotype) by production of the ABC protein Lsa(A),
Enterococcus faecium
is naturally susceptible. Since this phenotype may be selected for
in vivo
by quinupristin-dalfopristin (Q-D), the aim of this study was to investigate the molecular mechanism of acquired LS
A
P resistance in
E. faecium
. Six LS
A
P-resistant
in vitro
mutants of
E. faecium
HM1070 as well as three different pairs of clinical isolates (pre- and postexposure to Q-D) were studied. The full genome sequence of an
in vitro
mutant (
E. faecium
UCN90B) was determined by using 454 sequencing technology and was compared with that of the parental strain. Single-nucleotide replacement was carried out to confirm the role of this mutation. By comparative genomic analysis, a point mutation was found within a 1,503-bp gene coding for an ABC homologue showing 66% amino acid identity with Lsa(A). This mutation (C1349T) led to an amino acid substitution (Thr450Ile). An identical mutation was identified in all
in vitro
and
in vivo
resistant strains but was not present in susceptible strains. The wild-type allele was named
eat
(A) (for

E

nterococcus
A
BC
t
ransporter), and its mutated allelic variant was named
eat
(A)
v
. The introduction of
eat
(A)
v
from UCN90B into HM1070 conferred the LS
A
P phenotype, whereas that of
eat
(A) from HM1070 into UCN90B restored susceptibility entirely. This is the first description of the molecular mechanism of acquired LS
A
P resistance in
E. faecium
. Characterization of the biochemical mechanism of resistance and the physiological role of this ABC protein need further investigations.
Fidaxomicin versus Conventional Antimicrobial Therapy in 59 Recipients of Solid Organ and Hematopoietic Stem Cell Transplantation with Clostridium difficile-Associated Diarrhea
Authors: Clutter Dana S. , Dubrovskaya Yanina , Merl Man Yee , Teperman Lewis , Press Robert , Safdar Amar 
Published: July 2013

ABSTRACT

The feasibility of fidaxomicin versus vancomycin and metronidazole (conventional therapy) was assessed in 59 transplant recipients with 61 episodes of
Clostridium difficile
-associated diarrhea (CDAD). Overall clinical cure was achieved in 86% of episodes, and in 7% of episodes, infection recurred. Fidaxomicin was well tolerated. Clinical cures were not significantly different compared with conventional therapy (67% versus 89%, respectively;
P
= 0.06). Univariate analysis of predictors for lack of clinical cure included continued use of broad-spectrum systemic antibiotics (
P
= 0.026) and prior diagnosis of CDAD (95% confidence interval, 1.113 to 19.569; odds ratio, 4.667;
P
= 0.041). New-onset vancomycin-resistant
Enterococcus
(VRE) colonization was not noted after fidaxomicin therapy alone. However, this occurred in 10 of 28 patients (36%) following conventional therapy, and 2 of 3 patients with subsequent bacteremia died.
Complete Sequence of pSAM7, an IncX4 Plasmid Carrying a Novel
bla
CTX-M-14b
Transposition Unit Isolated from Escherichia coli and Enterobacter cloacae from Cattle
Authors: Stokes M. O. , AbuOun M. , Umur S. , Wu G. , Partridge S. R. , Mevius D. J. , Coldham N. G. , Fielder M. D. 
Published: July 2013

ABSTRACT

The same plasmid carrying
bla
CTX-M-14b
was identified from an
Escherichia coli
isolate and an
Enterobacter cloacae
isolate collected from cattle in the United Kingdom by complete plasmid sequencing. This 35,341-bp plasmid, pSAM7, had an IncX4 backbone that is 99% identical to that of pJIE143 from a human isolate in Australia. PCR screening identified pSAM7-like plasmids in three other
E. coli
isolates of different multilocus sequence types isolated from cattle on different farms in the United Kingdom.
KpnEF, a New Member of the Klebsiella pneumoniae Cell Envelope Stress Response Regulon, Is an SMR-Type Efflux Pump Involved in Broad-Spectrum Antimicrobial Resistance
Authors: Srinivasan Vijaya Bharathi , Rajamohan Govindan 
Published: July 2013

ABSTRACT

Klebsiella pneumoniae
has been frequently associated with nosocomial infections. Efflux systems are ubiquitous transporters that also function in drug resistance. Genome analysis of
K. pneumoniae
strain NTUH-K2044 revealed the presence of ∼15 putative drug efflux systems. We discuss here for the first time the characterization of a putative SMR-type efflux pump, an
ebrAB
homolog (denoted here as
kpnEF
) with respect to
Klebsiella
physiology and the multidrug-resistant phenotype. Analysis of hypermucoviscosity revealed direct involvement of
kpnEF
in capsule synthesis. The Δ
kpnEF
mutant displayed higher sensitivity to hyperosmotic (∼2.8-fold) and high bile (∼4.0-fold) concentrations. Mutation in
kpnEF
resulted in increased susceptibility to cefepime, ceftriaxone, colistin, erythromycin, rifampin, tetracycline, and streptomycin; mutated strains changed from being resistant to being susceptible, and the resistance was restored upon complementation. The Δ
kpnEF
mutant displayed enhanced sensitivity toward structurally related compounds such as sodium dodecyl sulfate, deoxycholate, and dyes, including clinically relevant disinfectants such as benzalkonium chloride, chlorhexidine, and triclosan. The prevalence of
kpnEF
in clinical strains broadens the diversity of antibiotic resistance in
K. pneumoniae
. Experimental evidence of CpxR binding to the efflux pump promoter and quantification of its expression in a
cpxAR
mutant background demonstrated
kpnEF
to be a member of the Cpx regulon. This study helps to elucidate the unprecedented biological functions of the SMR-type efflux pump in
Klebsiella
spp.
Malic Enzyme and Malolactic Enzyme Pathways Are Functionally Linked but Independently Regulated in Lactobacillus casei BL23
Authors: Landete José María , Ferrer Sergi , Monedero Vicente , Zúñiga Manuel 
Published: July 2013

ABSTRACTLactobacillus caseiis the only lactic acid bacterium in which two pathways forl-malate degradation have been described: the malolactic enzyme (MLE) and the malic enzyme (ME) pathways. Whereas the ME pathway enablesL. caseito grow onl-malate, MLE does not support growth. Themlegene cluster consists of three genes encoding MLE (mleS), the putativel-malate transporter MleT, and the putative regulator MleR. Themaegene cluster consists of four genes encoding ME (maeE), the putative transporter MaeP, and the two-component system MaeKR. Since both pathways compete for the same substrate, we sought to determine whether they are coordinately regulated and their role inl-malate utilization as a carbon source. Transcriptional analyses revealed that themleandmaegenes are independently regulated and showed that MleR acts as an activator and requires internalization ofl-malate to induce the expression ofmlegenes. Notwithstanding, bothl-malate transporters were required for maximall-malate uptake, although only anmleTmutation caused a growth defect onl-malate, indicating its crucial role inl-malate metabolism. However, inactivation of MLE resulted in higher growth rates and higher final optical densities onl-malate. The limited growth onl-malate of the wild-type strain was correlated to a rapid degradation of the availablel-malate tol-lactate, which cannot be further metabolized. Taken together, our results indicate thatL. caseil-malate metabolism is not optimized for utilization ofl-malate as a carbon source but for deacidification of the medium by conversion ofl-malate intol-lactate via MLE.
Peptidoglycan Fragment Release from Neisseria meningitidis
Authors: Woodhams Katelynn L. , Chan Jia Mun , Lenz Jonathan D. , Hackett Kathleen T. , Dillard Joseph P. 
Published: July 2013

ABSTRACT

Neisseria meningitidis
(meningococcus) is a symbiont of the human nasopharynx. On occasion, meningococci disseminate from the nasopharynx to cause invasive disease. Previous work showed that purified meningococcal peptidoglycan (PG) stimulates human Nod1, which leads to activation of NF-κB and production of inflammatory cytokines. No studies have determined if meningococci release PG or activate Nod1 during infection. The closely related pathogen
Neisseria gonorrhoeae
releases PG fragments during normal growth. These fragments induce inflammatory cytokine production and ciliated cell death in human fallopian tubes. We determined that meningococci also release PG fragments during growth, including fragments known to induce inflammation. We found that
N. meningitidis
recycles PG fragments via the selective permease AmpG and that meningococcal PG recycling is more efficient than gonococcal PG recycling. Comparison of PG fragment release from
N. meningitidis
and
N. gonorrhoeae
showed that meningococci release less of the proinflammatory PG monomers than gonococci and degrade PG to smaller fragments. The decreased release of PG monomers by
N. meningitidis
relative to
N. gonorrhoeae
is partly due to
ampG
, since replacement of gonococcal
ampG
with the meningococcal allele reduced PG monomer release. Released PG fragments in meningococcal supernatants induced significantly less Nod1-dependent NF-κB activity than released fragments in gonococcal supernatants and tended to induce less interleukin-8 (IL-8) secretion in primary human fallopian tube explants. These results support a model in which efficient PG recycling and extensive degradation of PG fragments lessen inflammatory responses and may be advantageous for maintaining meningococcal carriage in the nasopharynx.
Animal Models for Studying Female Genital Tract Infection with Chlamydia trachomatis
Authors: De Clercq Evelien , Kalmar Isabelle , Vanrompay Daisy 
Published: July 2013

ABSTRACTChlamydia trachomatisis a Gram-negative obligate intracellular bacterial pathogen. It is the leading cause of bacterial sexually transmitted disease in the world, with more than 100 million new cases of genital tract infections withC. trachomatisoccurring each year. Animal models are indispensable for the study ofC. trachomatisinfections and the development and evaluation of candidate vaccines. In this paper, the most commonly used animal models to study female genital tract infections withC. trachomatiswill be reviewed, namely, the mouse, guinea pig, and nonhuman primate models. Additionally, we will focus on the more recently developed pig model.
Engineering considerations for large dam removals
Authors: Hepler Thomas E. 
Published: July 2013

Abstract
The removal of a large dam requires special engineering considerations not normally required for the removal of smaller dams. Large dams generally provide greater project benefits, but they represent a higher downstream hazard in the event of failure and greater challenges to fish passage. The reservoirs associated with large dams can impound more sediment and affect downstream water quality to a greater degree. The environmental compliance and decision-making process for a large dam removal project can take many years and will normally require the evaluation of a full range of project alternatives with estimated costs, the performance of a comprehensive environmental impact analysis, and the identification and implementation of extensive mitigation measures. Streamflow diversion and demolition plans for the removal of a large dam must ensure acceptable construction risks from start to finish, and produce reservoir drawdown at a controlled rate for sediment management purposes and to prevent instability of natural or embankment slopes. Large dams require more time for removal, at a higher cost, and contain greater volumes of materials for which disposal sites must be found.