bluuebunny/crossref_metadata_2025 huggingface dataset:
Classification of Flow Patterns in Angled T-Junctions for the Evaluation of High Cycle Thermal Fatigue
Authors: Qian Shaoxiang , Frith James , Kasahara Naoto
Published: June 2014

Temperature fluctuations caused by the mixing of hot and cold streams at tee junctions may lead to high cycle thermal fatigue (HCTF) failure. It is necessary to evaluate the integrity of structures where the HCTF may occur. Therefore, the Japan Society of Mechanical Engineers (JSME) published “Guideline for Evaluation of High Cycle Thermal Fatigue of a Pipe (JSME S017),” in 2003, which provides the procedures and methods for evaluating the integrity of structures with the potential for HCTF. In JSME S017, one of the important procedures of thermal fatigue evaluation is to classify the flow patterns at tee junctions, because the degree of thermal fatigue damage is closely related to the flow pattern downstream of the mixing junction. The conventional characteristic equations for classifying flow patterns are only applicable to 90-deg tee junctions (T-junctions). However, angled tee junctions other than 90 deg (Y-junctions) are also used in chemical plants and refineries for reducing the pressure drop in the mixing zone and for weakening the force of the impingement of the branch pipe stream against the main pipe. The aim of this paper is to develop general characteristic equations applicable to both T- and Y-junctions. In this paper, general characteristic equations have been proposed based on the momentum ratio for all angles of tee junctions. Further, the validity of the proposed characteristic equations and their applicability to all angles of tee junctions have been confirmed using computational fluid dynamics (CFD) simulations. The results have also highlighted that the angle of the branch pipe has a significant effect on increasing the velocity ratio range for less damaging deflecting jet flow pattern, which is an important finding that could be used to extend the current design options for piping systems where HCTF may be a concern. In addition, categorization 3 is recommended as a more proper method for classifying flow patterns at tee junctions when evaluating the potential for thermal fatigue.
Centrifugal Turbines for Mini-Organic Rankine Cycle Power Systems
Authors: Casati Emiliano , Vitale Salvatore , Pini Matteo , Persico Giacomo , Colonna Piero
Published: June 2014

Organic Rankine cycle (ORC) power systems are rapidly diffusing as a technology for the conversion of thermal energy sources in the small-to-medium power range, e.g., from 150 kWe up to several MWe. The most critical component is arguably the expander, especially if the power capacity is small or very small, as it is the case for innovative high-potential applications such as waste heat recovery from truck engines, or distributed conversion of concentrated solar radiation. In these so-called high-temperature applications, the expansion ratio is very high; therefore, turbines are the expanders of choice. Recently, multistage radial-outflow turbines (ROT), a nonconventional turbine configuration, have been studied, and first commercial implementations in the MWe power range have been successful. The objective of this work is the evaluation of the radial-outflow arrangement for the turbine of high-temperature mini-ORC power systems, with power output of the order of 10 kWe. To this end, a method for the preliminary fluid-dynamic design is presented. It consists of an automated optimization procedure based on an in-house mean-line code for the one-dimensional preliminary design and efficiency estimation of turbines. It is first shown that usually adopted simplified design procedures, such as that of the so-called repeating-stage, cannot be extended to minicentrifugal turbines. The novel methodology is applied to the exemplary case of the 10 kWe turbine of an ORC power system for truck engine heat recovery documented in the literature. The expansion ratio is 45. The preliminary fluid-dynamic design of two miniturbines is presented, namely, a five-stage transonic and a three-stage slightly supersonic turbine. The outcome of the preliminary design leads to two turbine configurations whose fluid-dynamic efficiency exceeds 79% and 77%, respectively. The speed of revolution is around 12,400 and 15,400 RPM for the five-stage and the three-stage machine, respectively. These results show that the ROT configuration may allow for compact and efficient expanders for low power output applications.
Investigations on the Effects of Inflow Condition and Tip Clearance Size to the Performance of a Compressor Rotor
Authors: Zhang Chenkai , Hu Jun , Wang Zhiqiang
Published: June 2014

To clearly clarify the effects of different upstream boundary layer thickness and tip clearance size to the detailed tip flow field and flow mechanism, numerical simulations are performed on a subsonic compressor rotor, which is used for low-speed model testing of a rear stage embedded in a modern high-pressure compressor. First, available experimental data are adopted to validate the numerical method. Second, comparisons are made for tip leakage vortex (TLV) structure, the interface of leakage flow/mainflow, endwall loss, isentropic efficiency and pressure-rise among different operating conditions. Then, effects of different clearance sizes and inflow boundary layer thicknesses are investigated. Finally, the self-induced unsteadiness at one near-stall (NS) operating condition is studied for different cases. Results show that the increment of tip clearance size has a deleterious effect on rotor efficiency and pressure-rise performance over the whole operating range, while thickening the inflow boundary layer is almost the same except that its pressure-rise performance will be increased at mass flow rate larger than design operating condition. Self-induced unsteadiness occurs at NS operating conditions, and its appearance largely depends on tip clearance size, while the effect of upstream boundary layer thickness is little.
Natural Convective Boundary Layer Flow of Nanofluids Above an Isothermal Horizontal Plate
Authors: Pradhan Kaustav , Samanta Subho , Guha Abhijit
Published: June 2014

The natural convective boundary layer flow of a nanofluid over an isothermal horizontal plate is studied analytically. The model used for the nanofluid accounts for the effects of Brownian motion and thermophoresis. The analysis shows that the velocity, temperature, and nanoparticle volume fraction profiles in the respective boundary layers depend not only on the Prandtl number (Pr) and Lewis number (Le) but also on three additional dimensionless parameters: the Brownian motion parameter Nb, the buoyancy ratio parameter Nr and the thermophoresis parameter Nt. The velocity, temperature, and nanoparticle volume fraction profiles for the nanofluid are found to have a weak dependence on the values of Nb, Nr, and Nt. The effect of the above-mentioned parameters on the local skin-friction coefficient and Nusselt number has been studied extensively. It has been observed that as Nr increases, the local skin-friction coefficient decreases whereas local Nusselt number remains almost constant. As Nb or Nt increases, the local skin-friction coefficient increases whereas the local Nusselt number decreases.
Comparative Study on Heat Transfer Enhancement of Low Volume Concentration of Al2O3–Water and Carbon Nanotube–Water Nanofluids in Laminar Regime Using Helical Screw Tape Inserts
Authors: Chougule Sandesh S. , Sahu S. K.
Published: June 2014

An experimental study has been carried out to evaluate the heat transfer and friction factor characteristics of helical screw inserts in Al2O3–water and carbon nanotubes (CNT)–water nanofluids through a straight pipe in laminar flow regime with constant heat flux boundary condition. Tests have been performed by using 0.15% volume concentration Al2O3–water and CNT–water nanofluid with helical tape inserts of twist ratio (TR) = 1.5, 2.5, and 3. The helical screw tape inserts with CNT–water nanofluid exhibits higher thermal performance compared to Al2O3–water nanofluid. The maximum enhancement in heat transfer was obtained for CNT–water nanofluid with helical tape inserts of TR = 1.5. The increase in pressure drop of Al2O3–water nanofluid with helical screw tape inserts is found to be higher compared to CNT–water nanofluid with helical screw tape inserts at lower value of TR. For both the nanofluids (CNT–water and Al2O3–water), the thermal performance factor was found to be greater than unity for all TRs.
Barrier height inhomogeneities induced anomaly in thermal sensitivity of Ni/4H-SiC Schottky diode temperature sensor
Authors: Kumar Vibhor , Maan Anup Singh , Akhtar Jamil
Published: June 2014

This paper presents the thermal sensitivity variation trend of Ni/4H-nSiC (0001) Schottky diode based temperature sensor, equipped with floating metal guard ring and oxide field plate as edge terminations in low current regime, i.e., ranging from 1 nA to 5 pA. Various measurements were carried out at temperatures ranging from 233 K to 473 K in steps of 20 K. An imperative outcome of the present study, which is in contrast with the theory, is that there exists an anomaly in the device thermal sensitivity behaviour after a range of current. The thermal sensitivity of the fabricated device, calculated from the slope of forward voltage versus temperature plot, was found to be varied from 3.11 mV/K at 1 nA to 3.32 mV/K at 5 pA with standard error of ±0.03 mV/K. A detailed analysis of I-V-T characteristics by taking into account all the possibilities for variation in the barrier height and the ideality factor with temperature emphasizes that there exist barrier height inhomogeneities at the metal–semiconductor interface in the fabricated device. These observations indicate that anomaly in the device thermal sensitivity was due to the barrier height inhomogeneities present in the device.
LIMK-Dependent Actin Polymerization in Primary Sensory Neurons Promotes the Development of Inflammatory Heat Hyperalgesia in Rats
Authors: Li Yi , Hu Fang , Chen Hai-Jing , Du Yi-Juan , Xie Zhi-Ying , Zhang Ying , Wang Jun , Wang Yun
Published: June 2014

Inflammation-induced sensitivity to pain could be reduced by disrupting the actin cytoskeleton in primary sensory neurons.
Cancer at Single-Cell Resolution
Authors: Zahn Laura M.
Published: June 2014

Screening individual cancer cells within a brain tumor may help to guide treatment and predict prognosis.
Cytokine Rivalry
Authors: Colmone Angela C.
Published: June 2014

GM-CSF–producing T helper cells in humans follow a distinct regulation program as compared to T
H
17 cells and are associated with multiple sclerosis.
Preventing Myoblasts from Premature Differentiation
Authors: Gough Nancy R.
Published: June 2014

Endocannabinoids inhibit muscle differentiation.
Mobilizing Hematopoietic Stem Cells
Authors: VanHook Annalisa M.
Published: June 2014

Pathogen-induced signaling through Toll-like and NOD-like receptors mobilizes hematopoietic stem cells to the spleen.
A New Therapeutic Target in Uveal Melanoma
Authors: Ferrarelli Leslie K.
Published: June 2014

Inhibiting the transcriptional coactivator YAP in uveal melanoma with
GNAQ
or
GNA11
mutations may suppress tumor growth in patients.
The IL-4 Brown Out
Authors: Berndt Jason D.
Published: June 2014

Immune cell activation promotes thermogenesis in white fat.
Breaking Down the Invasion
Authors: Wong Wei
Published: June 2014

A pathway that triggers the breakdown of invadopodia in metastatic breast cancer cells is identified.
Defining Daptomycin Resistance Prevention Exposures in Vancomycin-Resistant Enterococcus faecium and E. faecalis
Authors: Werth B. J. , Steed M. E. , Ireland C. E. , Tran T. T. , Nonejuie P. , Murray B. E. , Rose W. E. , Sakoulas G. , Pogliano J. , Arias C. A. , Rybak M. J.
Published: June 2014

Daptomycin is used off-label for enterococcal infections; however, dosing targets for resistance prevention remain undefined. Doses of 4 to 6 mg/kg of body weight/day approved for staphylococci are likely inadequate against enterococci due to reduced susceptibility. We modeled daptomycin regimens
in vitro
to determine the minimum exposure to prevent daptomycin resistance (Dap
r
) in enterococci. Daptomycin simulations of 4 to 12 mg/kg/day (maximum concentration of drug in serum [
C
max
] of 57.8, 93.9, 123.3, 141.1, and 183.7 mg/liter; half-life [
t
1/2
] of 8 h) were tested against one
Enterococcus faecium
strain (S447) and one
Enterococcus faecalis
strain (S613) in a simulated endocardial vegetation pharmacokinetic/pharmacodynamic model over 14 days. Samples were plated on media containing 3× the MIC of daptomycin to detect Dap
r
. Mutations in genes encoding proteins associated with cell envelope homeostasis (
yycFG
and
liaFSR
) and phospholipid metabolism (cardiolipin synthase [
cls
] and cyclopropane fatty acid synthetase [
cfa
]) were investigated in Dap
r
derivatives. Dap
r
derivatives were assessed for changes in susceptibility, surface charge, membrane depolarization, cell wall thickness (CWT), and growth rate. Strains S447 and S613 developed Dap
r
after simulations of 4 to 8 mg/kg/day but not 10 to 12 mg/kg/day. MICs for Dap
r
strains ranged from 8 to 256 mg/liter. Some S613 derivatives developed mutations in
liaF
or
cls
. S447 derivatives lacked mutations in these genes. Dap
r
derivatives from both strains exhibited lowered growth rates, up to a 72% reduction in daptomycin-induced depolarization and up to 6-nm increases in CWT (
P
< 0.01). Peak/MIC and AUC
0–24
/MIC ratios (AUC
0–24
is the area under the concentration-time curve from 0 to 24 h) associated with Dap
r
prevention were 72.1 and 780 for S447 and 144 and 1561 for S613, respectively. Daptomycin doses of 10 mg/kg/day may be required to prevent Dap
r
in serious enterococcal infections.
Long-Term Dissemination of CTX-M-5-Producing Hypermutable Salmonella enterica Serovar Typhimurium Sequence Type 328 Strains in Russia, Belarus, and Kazakhstan
Authors: Kozyreva Varvara K. , Ilina Elena N. , Malakhova Maja V. , Carattoli Alessandra , Azizov Ilya S. , Tapalski Dmitry V. , Kozlov Roman S. , Edelstein Mikhail V.
Published: June 2014

In this paper, we present evidence of long-term circulation of cefotaxime-resistant clonally relatedSalmonella entericaserovar Typhimurium strains over a broad geographic area. The genetic relatedness of 88 isolates collected from multiple outbreaks and sporadic cases of nosocomial salmonellosis in various parts of Russia, Belarus, and Kazakhstan from 1996 to 2009 was established by multilocus tandem-repeat analysis (MLVA) and multilocus sequence typing (MLST). The isolates belong to sequence type 328 (ST328) and produce CTX-M-5 β-lactamase, whose gene is carried by highly related non-self-conjugative but mobilizable plasmids. Resistance to nalidixic acid and low-level resistance to ciprofloxacin is present in 37 (42%) of the isolates and in all cases is determined by various single point mutations in thegyrAgene quinolone resistance-determining region (QRDR). Isolates of the described clonal group exhibit a hypermutable phenotype that probably facilitates independent acquisition of quinolone resistance mutations.
Epidemiology and Predictors of Multidrug-Resistant Community-Acquired and Health Care-Associated Pneumonia
Authors: Gross Alan E. , Van Schooneveld Trevor C. , Olsen Keith M. , Rupp Mark E. , Bui Thu Hong , Forsung Elsie , Kalil Andre C.
Published: June 2014

There are limited U.S. data describing the risk factors for multidrug-resistant organism (MDRO) isolation in community-acquired pneumonia (CAP) and health care-associated pneumonia (HCAP). However, concern for the presence of these pathogens drives the prescribing of empiric broad-spectrum antibiotics for CAP and HCAP. A retrospective study of all adults hospitalized with community-onset pneumonia (CAP and HCAP) at a large U.S. medical center from January 2010 to December 2011 was conducted. The objective was to ascertain the rate of pneumonia caused by MDROs and to evaluate whether HCAP is a risk factor for MDRO pneumonia. Univariate and propensity score-adjusted multivariate analyses were performed. A total of 521 patients (50.5% CAP and 49.5% HCAP) were included. The most common etiologies of pneumonia were primary viral and
Streptococcus pneumoniae
. MDROs were isolated in 20 (3.8%) patients overall, and MDROs occurred in 5.9% and 1.9% of HCAP and CAP patients, respectively. The presence of an MDRO was not associated with HCAP classification (odds ratio [OR] = 1.95; 95% confidence interval [95% CI], 0.66 to 5.80;
P
= 0.23) or with most of its individual components (hemodialysis, home infusion, home wound care, and ≥48-h hospitalization in the last 90 days). Independent predictors of MDRO included the following:
Pseudomonas aeruginosa
colonization/infection in the previous year (OR = 7.43; 95% CI, 2.24 to 24.61;
P
< 0.001), antimicrobial use in the previous 90 days (OR = 2.90; 95% CI, 1.13 to 7.45;
P
= 0.027), admission from a nursing home (OR = 4.19; 95% CI, 1.55 to 11.31;
P
= 0.005), and duration of hospitalization in the previous 90 or 180 days (
P
= 0.013 and
P
= 0.002, respectively). MDROs were uncommon in HCAP and CAP. HCAP did not predict MDRO isolation. Local etiology of community onset pneumonia and specific MDRO risk factors should be integrated into therapeutic decisions to prevent empirical overprescribing of antibiotics for methicillin-resistant
Staphylococcus aureus
(MRSA) and
P. aeruginosa
.
Comparative Efficacies of Cloxacillin-Daptomycin and the Standard Cloxacillin-Rifampin Therapies against an Experimental Foreign-Body Infection by Methicillin-Susceptible Staphylococcus aureus
Authors: El Haj Cristina , Murillo Oscar , Ribera Alba , Vivas Mireia , Garcia-Somoza Dolors , Tubau Fe , Cabo Javier , Ariza Javier
Published: June 2014

We compared the efficacies of daptomycin (doses equivalent to 8 to 10 mg/kg of body weight/day in humans) and cloxacillin alone with those of cloxacillin-rifampin and cloxacillin-daptomycin combinations, using a tissue cage methicillin-susceptible
Staphylococcus aureus
(MSSA) infection model. Monotherapies were less effective than combinations (
P
< 0.05), and daptomycin resistance emerged. Cloxacillin-daptomycin proved as effective as cloxacillin-rifampin and prevented the appearance of resistance; this combination may be an alternative anti-MSSA therapy, which may offer greater benefits in the early treatment of prosthetic joint infections (PJI).
Micafungin at Physiological Serum Concentrations Shows Antifungal Activity against Candida albicans and Candida parapsilosis Biofilms
Authors: Guembe M. , Guinea J. , Marcos-Zambrano L. J. , Fernández-Cruz A. , Peláez T. , Muñoz P. , Bouza E.
Published: June 2014

We assessed the
in vitro
activity of micafungin against preformed
Candida
biofilms by measuring the concentration of drug causing the most fungal damage and inhibition of regrowth. We studied 37 biofilm-producing
Candida
spp. strains from blood cultures. We showed that micafungin was active against planktonic and sessile forms of
Candida albicans
strains and moderately active against
Candida parapsilosis
sessile cells. Concentrations of micafungin above 2 μg/ml were sufficiently high to inactivate regrowth of
Candida
sessile cells.
In Vitro
Efficacy of Brincidofovir against Variola Virus
Authors: Olson Victoria A. , Smith Scott K. , Foster Scott , Li Yu , Lanier E. Randall , Gates Irina , Trost Lawrence C. , Damon Inger K.
Published: June 2014

Brincidofovir (CMX001), a lipid conjugate of the acyclic nucleotide phosphonate cidofovir, is under development for smallpox treatment using “the Animal Rule,” established by the FDA in 2002. Brincidofovir reduces mortality caused by orthopoxvirus infection in animal models. Compared to cidofovir, brincidofovir has increased potency, is administered orally, and shows no evidence of nephrotoxicity. Here we report that the brincidofovir half-maximal effective concentration (EC
50
) against five variola virus strains
in vitro
averaged 0.11 μM and that brincidofovir was therefore nearly 100-fold more potent than cidofovir.
Effectiveness of Antimicrobial Peptide Immobilization for Preventing Perioperative Cornea Implant-Associated Bacterial Infection
Authors: Tan Xiao Wei , Goh Tze Wei , Saraswathi P. , Nyein Chan Lwin , Setiawan Melina , Riau Andri , Lakshminarayanan R. , Liu Shouping , Tan Donald , Beuerman Roger W. , Mehta Jodhbir S.
Published: June 2014

Titanium (Ti) is a promising candidate biomaterial for an artificial corneal skirt. Antimicrobial peptide (AMP) immobilization may improve the bactericidal effect of the Ti substrate. In this study, we tested the bactericidal efficacy of a functionalized Ti surface in a rabbit keratitis model. A corneal stromal pocket was created by a femtosecond laser. The Ti films were then inserted into the pocket, and
Staphylococcus aureus
or
Pseudomonas aeruginosa
was inoculated into the pocket above the implant films. The corneas with Ti-AMP implants were compared with the corneas implanted with unprotected Ti by slit lamp observation and anterior segment optical coherence tomography (AS-OCT). Inflammatory responses were evaluated by bacterium counting, hematoxylin-eosin staining, and immunostaining. There was a lower incidence and a lesser extent of infection on rabbit corneas with Ti-AMP implants than on those with unprotected Ti implants. The bactericidal effect of AMP against
S. aureus
was comparable to that of postoperative prophylactic antibiotic treatment; hence, SESB2V AMP bound to the Ti implant provided functional activity
in vivo
, but its efficacy was greater against
S. aureus
than against
P. aeruginosa
. This work suggests that SESB2V AMP can be successfully functionalized in a rabbit keratitis model to prevent perioperative corneal infection.
Bactericidal Activity, Absence of Serum Effect, and Time-Kill Kinetics of Ceftazidime-Avibactam against β-Lactamase-Producing Enterobacteriaceae and Pseudomonas aeruginosa
Authors: Keepers Tiffany R. , Gomez Marcela , Celeri Chris , Nichols Wright W. , Krause Kevin M.
Published: June 2014

Avibactam, a non-β-lactam β-lactamase inhibitor with activity against extended-spectrum β-lactamases (ESBLs), KPC, AmpC, and some OXA enzymes, extends the antibacterial activity of ceftazidime against most ceftazidime-resistant organisms producing these enzymes. In this study, the bactericidal activity of ceftazidime-avibactam against 18
Pseudomonas aeruginosa
isolates and 15
Enterobacteriaceae
isolates, including wild-type isolates and ESBL, KPC, and/or AmpC producers, was evaluated. Ceftazidime-avibactam MICs (0.016 to 32 μg/ml) were lower than those for ceftazidime alone (0.06 to ≥256 μg/ml) against all isolates except for 2
P. aeruginosa
isolates (1
bla
VIM
-positive isolate and 1
bla
OXA-23
-positive isolate). The minimum bactericidal concentration/MIC ratios of ceftazidime-avibactam were ≤4 for all isolates, indicating bactericidal activity. Human serum and human serum albumin had a minimal effect on ceftazidime-avibactam MICs. Ceftazidime-avibactam time-kill kinetics were evaluated at low MIC multiples and showed time-dependent reductions in the number of CFU/ml from 0 to 6 h for all strains tested. A ≥3-log
10
decrease in the number of CFU/ml was observed at 6 h for all
Enterobacteriaceae
, and a 2-log
10
reduction in the number of CFU/ml was observed at 6 h for 3 of the 6
P. aeruginosa
isolates. Regrowth was noted at 24 h for some of the isolates tested in time-kill assays. These data demonstrate the potent bactericidal activity of ceftazidime-avibactam and support the continued clinical development of ceftazidime-avibactam as a new treatment option for infections caused by
Enterobacteriaceae
and
P. aeruginosa
, including isolates resistant to ceftazidime by mechanisms dependent on avibactam-sensitive β-lactamases.
Pyochelin Potentiates the Inhibitory Activity of Gallium on Pseudomonas aeruginosa
Authors: Frangipani Emanuela , Bonchi Carlo , Minandri Fabrizia , Imperi Francesco , Visca Paolo
Published: June 2014

Gallium (Ga) is an iron mimetic that has successfully been repurposed for antibacterial chemotherapy. To improve the antibacterial potency of Ga on
Pseudomonas aeruginosa
, the effect of complexation with a variety of siderophores and synthetic chelators was tested. Ga complexed with the pyochelin siderophore (at a 1:2 ratio) was more efficient than Ga(NO
3
)
3
in inhibiting
P. aeruginosa
growth, and its activity was dependent on increased Ga entrance into the cell through the pyochelin translocon.
1,4-Azaindole, a Potential Drug Candidate for Treatment of Tuberculosis
Authors: Chatterji Monalisa , Shandil Radha , Manjunatha M. R. , Solapure Suresh , Ramachandran Vasanthi , Kumar Naveen , Saralaya Ramanatha , Panduga Vijender , Reddy Jitendar , KR Prabhakar , Sharma Sreevalli , Sadler Claire , Cooper Christopher B. , Mdluli Khisi , Iyer Pravin S. , Narayanan Shridhar , Shirude Pravin S.
Published: June 2014

New therapeutic strategies against multidrug-resistant (MDR) and extensively drug-resistant (XDR)
Mycobacterium tuberculosis
are urgently required to combat the global tuberculosis (TB) threat. Toward this end, we previously reported the identification of 1,4-azaindoles, a promising class of compounds with potent antitubercular activity through noncovalent inhibition of decaprenylphosphoryl-β-
d
-ribose 2′-epimerase (DprE1). Further, this series was optimized to improve its physicochemical properties and pharmacokinetics in mice. Here, we describe the short-listing of a potential clinical candidate, compound 2, that has potent cellular activity, drug-like properties, efficacy in mouse and rat chronic TB infection models, and minimal
in vitro
safety risks. We also demonstrate that the compounds, including compound 2, have no antagonistic activity with other anti-TB drugs. Moreover, compound 2 shows synergy with PA824 and TMC207
in vitro
, and the synergy effect is translated
in vivo
with TMC207. The series is predicted to have a low clearance in humans, and the predicted human dose for compound 2 is ≤1 g/day. Altogether, our data suggest that a 1,4-azaindole (compound 2) is a promising candidate for the development of a novel anti-TB drug.
Characterization of Drug-Resistant Influenza Virus A(H1N1) and A(H3N2) Variants SelectedIn Vitrowith Laninamivir
Authors: Samson Mélanie , Abed Yacine , Desrochers François-Marc , Hamilton Stephanie , Luttick Angela , Tucker Simon P. , Pryor Melinda J. , Boivin Guy
Published: June 2014

Neuraminidase inhibitors (NAIs) play a major role for managing influenza virus infections. The widespread oseltamivir resistance among 2007-2008 seasonal A(H1N1) viruses and community outbreaks of oseltamivir-resistant A(H1N1)pdm09 strains highlights the need for additional anti-influenza virus agents. Laninamivir is a novel long-lasting NAI that has demonstratedin vitroactivity against influenza A and B viruses, and its prodrug (laninamivir octanoate) is in phase II clinical trials in the United States and other countries. Currently, little information is available on the mechanisms of resistance to laninamivir. In this study, we first performed neuraminidase (NA) inhibition assays to determine the activity of laninamivir against a set of influenza A viruses containing NA mutations conferring resistance to one or many other NAIs. We also generated drug-resistant A(H1N1) and A(H3N2) viruses underin vitrolaninamivir pressure. Laninamivir demonstrated a profile of susceptibility that was similar to that of zanamivir. More specifically, it retained activity against oseltamivir-resistant H275Y and N295S A(H1N1) variants and the E119V A(H3N2) variant.In vitro, laninamivir pressure selected the E119A NA substitution in the A/Solomon Islands/3/2006 A(H1N1) background, whereas E119K and G147E NA changes along with a K133E hemagglutinin (HA) substitution were selected in the A/Quebec/144147/2009 A(H1N1)pdm09 strain. In the A/Brisbane/10/2007 A(H3N2) background, a large NA deletion accompanied by S138A/P194L HA substitutions was selected. This H3N2 variant had altered receptor-binding properties and was highly resistant to laninamivir in plaque reduction assays. Overall, we confirmed the similarity between zanamivir and laninamivir susceptibility profiles and demonstrated that both NA and HA changes can contribute to laninamivir resistancein vitro.
Phase I Safety, Pharmacokinetics, and Pharmacogenetics Study of the Antituberculosis Drug PA-824 with Concomitant Lopinavir-Ritonavir, Efavirenz, or Rifampin
Authors: Dooley Kelly E. , Luetkemeyer Anne F. , Park Jeong-Gun , Allen Reena , Cramer Yoninah , Murray Stephen , Sutherland Deborah , Aweeka Francesca , Koletar Susan L. , Marzan Florence , Bao Jing , Savic Rada , Haas David W.
Published: June 2014

There is an urgent need for new antituberculosis (anti-TB) drugs, including agents that are safe and effective with concomitant antiretrovirals (ARV) and first-line TB drugs. PA-824 is a novel antituberculosis nitroimidazole in late-phase clinical development. Cytochrome P450 (CYP) 3A, which can be induced or inhibited by ARV and antituberculosis drugs, is a minor (∼20%) metabolic pathway for PA-824. In a phase I clinical trial, we characterized interactions between PA-824 and efavirenz (arm 1), lopinavir/ritonavir (arm 2), and rifampin (arm 3) in healthy, HIV-uninfected volunteers without TB disease. Participants in arms 1 and 2 were randomized to receive drugs via sequence 1 (PA-824 alone, washout, ARV, and ARV plus PA-824) or sequence 2 (ARV, ARV with PA-824, washout, and PA-824 alone). In arm 3, participants received PA-824 and then rifampin and then both. Pharmacokinetic sampling occurred at the end of each dosing period. Fifty-two individuals participated. Compared to PA-824 alone, plasma PA-824 values (based on geometric mean ratios) for maximum concentration (
C
max
), area under the concentration-time curve from 0 to 24 h (AUC
0–24
), and trough concentration (
C
min
) were reduced 28%, 35%, and 46% with efavirenz, 13%, 17%, and 21% with lopinavir-ritonavir (lopinavir/r) and 53%, 66%, and 85% with rifampin, respectively. Medications were well tolerated. In conclusion, lopinavir/r had minimal effect on PA-824 exposures, supporting PA-824 use with lopinavir/r without dose adjustment. PA-824 exposures, though, were reduced more than expected when given with efavirenz or rifampin. The clinical implications of these reductions will depend upon data from current clinical trials defining PA-824 concentration-effect relationships. (This study has been registered at ClinicalTrials.gov under registration no. NCT01571414.)
Identification of Novel Coxiella burnetii Icm/Dot Effectors and Genetic Analysis of Their Involvement in Modulating a Mitogen-Activated Protein Kinase Pathway
Authors: Lifshitz Ziv , Burstein David , Schwartz Kierstyn , Shuman Howard A. , Pupko Tal , Segal Gil
Published: June 2014

Coxiella burnetii
, the causative agent of Q fever, is a human intracellular pathogen that utilizes the Icm/Dot type IVB secretion system to translocate effector proteins into host cells. To identify novel
C. burnetii
effectors, we applied a machine-learning approach to predict
C. burnetii
effectors, and examination of 20 such proteins resulted in the identification of 13 novel effectors. To determine whether these effectors, as well as several previously identified effectors, modulate conserved eukaryotic pathways, they were expressed in
Saccharomyces cerevisiae
. The effects on yeast growth were examined under regular growth conditions and in the presence of caffeine, a known modulator of the yeast cell wall integrity (CWI) mitogen-activated protein (MAP) kinase pathway. In the presence of caffeine, expression of the effectors CBU0885 and CBU1676 caused an enhanced inhibition of yeast growth, and the growth inhibition of CBU0388 was suppressed. Furthermore, analysis of synthetic lethality effects and examination of the activity of the CWI MAP kinase transcription factor Rlm1 indicated that CBU0388 enhances the activation of this MAP kinase pathway in yeast, while CBU0885 and CBU1676 abolish this activation. Additionally, coexpression of CBU1676 and CBU0388 resulted in mutual suppression of their inhibition of yeast growth. These results strongly indicate that these three effectors modulate the CWI MAP kinase pathway in yeast. Moreover, both CBU1676 and CBU0885 were found to contain a conserved haloacid dehalogenase (HAD) domain, which was found to be required for their activity. Collectively, our results demonstrate that MAP kinase pathways are most likely targeted by
C. burnetii
Icm/Dot effectors.
Protective Role of the Capsule and Impact of Serotype 4 Switching on Streptococcus mitis
Authors: Rukke Håkon V. , Kalluru Raja Sab , Repnik Urska , Gerlini Alice , José Ricardo J. , Periselneris Jimstan , Marshall Helina , Griffiths Gareth , Oggioni Marco Rinaldo , Brown Jeremy S. , Petersen Fernanda C.
Published: June 2014

The polysaccharide capsule surrounding
Streptococcus pneumoniae
is essential for virulence. Recently,
Streptococcus mitis
, a human commensal and a close relative of
S. pneumoniae
, was also shown to have a capsule. In this study, the
S. mitis
type strain switched capsule by acquisition of the serotype 4 capsule locus of
S. pneumoniae
TIGR4, following induction of competence for natural transformation. Comparison of the wild type with the capsule-switching mutant and with a capsule deletion mutant showed that the capsule protected
S. mitis
against phagocytosis by RAW 264.7 macrophages. This effect was enhanced in the
S. mitis
strain expressing the
S. pneumoniae
capsule, which showed, in addition, increased resistance against early clearance in a mouse model of lung infection. Expression of both capsules also favored survival in human blood, and the effect was again more pronounced for the capsule-switching mutant.
S. mitis
survival in horse blood or in a mouse model of bacteremia was not significantly different between the wild type and the mutant strains. In all models,
S. pneumoniae
TIGR4 showed higher rates of survival than the
S. mitis
type strain or the capsule-switching mutant, except in the lung model, in which significant differences between
S. pneumoniae
TIGR4 and the capsule-switching mutant were not observed. Thus, we identified conditions that showed a protective function for the capsule in
S. mitis
. Under such conditions,
S. mitis
resistance to clearance could be enhanced by capsule switching to serotype 4, but it was enhanced to levels lower than those for the virulent strain
S. pneumoniae
TIGR4.
Placental Cytokine and Chemokine Profiles Reflect Pregnancy Outcomes in Women Exposed to Plasmodium falciparum Infection
Authors: Chêne Arnaud , Briand Valérie , Ibitokou Samad , Dechavanne Sébastien , Massougbodji Achille , Deloron Philippe , Luty Adrian J. F. , Gamain Benoît , Fievet Nadine
Published: June 2014

Pregnancy-associated malaria (PAM) can lead to severe complications for both mother and baby. Certain placental cytokine/chemokine profiles have been shown to reflect poor pregnancy outcomes, including maternal anemia and low birth weight. In intervillous plasma samples from 400 Beninese women living in an area wherePlasmodium falciparumis endemic, we quantified 16 cytokines/chemokines. We assessed their profiles in groups with PAM, with maternal anemia, with preterm births, or with a low birth weight for gestational age. Repeated ultrasound measurements ensured that prematurity and low birth weight were highly accurate. Preliminary analyses revealed trends for lower cytokine/chemokine concentrations in placental plasma associated both with babies with low birth weight for gestational age and withP. falciparuminfection during pregnancy, while, as a function of the latter, the concentration of gamma interferon (IFN-γ)-inducible protein 10 (IP-10) was higher. Multivariate analyses showed that (i) higher placental plasma interleukin-10 (IL-10) levels were associated withP. falciparuminfections and (ii) independently ofP. falciparuminfections, lower concentrations of both IFN-γ and IL-5 were associated with low birth weight for gestational age. Our data further strengthen the idea that IL-10 and IP-10 could be useful diagnostic markers ofP. falciparuminfection during pregnancy. The concentrations of cytokines/chemokines in placental plasma may represent previously unrecognized markers of poor fetal growth.
Interplay between Two Bacterial Actin Homologs, MamK and MamK-Like, Is Required for the Alignment of Magnetosome Organelles in Magnetospirillum magneticum AMB-1
Authors: Abreu Nicole , Mannoubi Soumaya , Ozyamak Ertan , Pignol David , Ginet Nicolas , Komeili Arash
Published: June 2014

Many bacterial species contain multiple actin-like proteins tasked with the execution of crucial cell biological functions. MamK, an actin-like protein found in magnetotactic bacteria, is important in organizing magnetosome organelles into chains that are used for navigation along geomagnetic fields. MamK and numerous other magnetosome formation factors are encoded by a genetic island termed the magnetosome island. Unlike most magnetotactic bacteria,
Magnetospirillum magneticum
AMB-1 (AMB-1) contains a second island of magnetosome-related genes that was named the magnetosome islet. A homologous copy of
mamK
,
mamK-like
, resides within this islet and encodes a protein capable of filament formation
in vitro
. Previous work had shown that
mamK-like
is expressed
in vivo
, but its function, if any, had remained unknown. Though MamK-like is highly similar to MamK, it contains a mutation that in MamK and other actins blocks ATPase activity
in vitro
and filament dynamics
in vivo
. Here, using genetic analysis, we demonstrate that
mamK-like
has an
in vivo
role in assisting organelle alignment. In addition, MamK-like forms filaments
in vivo
in a manner that is dependent on the presence of MamK and the two proteins interact in a yeast two-hybrid assay. Surprisingly, despite the ATPase active-site mutation, MamK-like is capable of ATP hydrolysis
in vitro
and promotes MamK filament turnover
in vivo
. Taken together, these experiments suggest that direct interactions between MamK and MamK-like contribute to magnetosome alignment in AMB-1.
DNA Ligase C1 Mediates the LigD-Independent Nonhomologous End-Joining Pathway of Mycobacterium smegmatis
Authors: Bhattarai Hitesh , Gupta Richa , Glickman Michael S.
Published: June 2014

Nonhomologous end joining (NHEJ) is a recently described bacterial DNA double-strand break (DSB) repair pathway that has been best characterized for mycobacteria. NHEJ can religate transformed linear plasmids, repair ionizing radiation (IR)-induced DSBs in nonreplicating cells, and seal I-SceI-induced chromosomal DSBs. The core components of the mycobacterial NHEJ machinery are the DNA end binding protein Ku and the polyfunctional DNA ligase LigD. LigD has three autonomous enzymatic modules: ATP-dependent DNA ligase (LIG), DNA/RNA polymerase (POL), and 3′ phosphoesterase (PE). Although genetic ablation of
ku
or
ligD
abolishes NHEJ and sensitizes nonreplicating cells to ionizing radiation, selective ablation of the ligase activity of LigD
in vivo
only mildly impairs NHEJ of linearized plasmids, indicating that an additional DNA ligase can support NHEJ. Additionally, the
in vivo
role of the POL and PE domains in NHEJ is unclear. Here we define a LigD ligase-independent NHEJ pathway in
Mycobacterium smegmatis
that requires the ATP-dependent DNA ligase LigC1 and the POL domain of LigD.
Mycobacterium tuberculosis
LigC can also support this backup NHEJ pathway. We also demonstrate that, although dispensable for efficient plasmid NHEJ, the activities of the POL and PE domains are required for repair of IR-induced DSBs in nonreplicating cells. These findings define the genetic requirements for a LigD-independent NHEJ pathway in mycobacteria and demonstrate that all enzymatic functions of the LigD protein participate in NHEJ
in vivo
.
Suppression of Conformation-Compromised Mutants of Salmonella enterica Serovar Typhimurium MelB
Authors: Amin Anowarul , Ethayathulla Abdul S. , Guan Lan
Published: June 2014

The crystal structure of the Na
+
-coupled melibiose permease of
Salmonella enterica
serovar Typhimurium (MelB
St
) demonstrates that MelB is a member of the major facilitator superfamily of transporters. Arg residues at positions 295, 141, and 363 are involved in interdomain interactions at the cytoplasmic side by governing three clusters of electrostatic/polar interactions. Insertion of (one at a time) Glu, Leu, Gln, or Cys at positions R295, R141, and R363, or Lys at position R295, inhibits active transport of melibiose to a level of 2 to 20% of the value for wild-type (WT) MelB
St
, with little effect on binding affinities for both sugar and Na
+
. Interestingly, a spontaneous suppressor, D35E (periplasmic end of helix I), was isolated from the R363Q MelB
St
mutant. Introduction of the D35E mutation in each of the mutants at R295, R141 (except R141E), or R363 rescues melibiose transport to up to 91% of the WT value. Single-site mutations for the pair of D35 and R175 (periplasmic end of helix VI) were constructed by replacing Asp with Glu, Gln, or Cys and R175 with Gln, Asn, or Cys. All mutants with mutations at R175 are active, indicating that a positive charge at R175 is not necessary. Mutant D35E shows reduced transport; D35Q and D35C are nearly inactivated. Surprisingly, the D35Q mutation partially rescues both R141C and R295Q mutations. The data support the idea that Arg at position 295 and a positive charge at positions 141 and 363 are required for melibiose transport catalyzed by MelB
St
, and their mutation inhibits conformational cycling, which is suppressed by a minor modification at the opposite side of the membrane.
Acetyl Coenzyme A Synthetase Is Acetylated on Multiple Lysine Residues by a Protein Acetyltransferase with a Single Gcn5-Type
N
-Acetyltransferase (GNAT) Domain in Saccharopolyspora erythraea
Authors: You Di , Yao Li-li , Huang Dan , Escalante-Semerena Jorge C. , Ye Bang-Ce
Published: June 2014

Reversible lysine acetylation (RLA) is used by cells of all domains of life to modulate protein function. To date, bacterial acetylation/deacetylation systems have been studied in a few bacteria (e.g.,
Salmonella enterica
,
Bacillus subtilis
,
Escherichia coli
,
Erwinia amylovora
,
Mycobacterium tuberculosis
, and
Geobacillus kaustophilus
), but little is known about RLA in antibiotic-producing actinomycetes. Here, we identify the Gcn5-like protein acetyltransferase AcuA of
Saccharopolyspora erythraea
(
Sac
AcuA, SACE_5148) as the enzyme responsible for the acetylation of the AMP-forming acetyl coenzyme A synthetase (
Sac
AcsA, SACE_2375). Acetylated
Sac
AcsA was deacetylated by a sirtuin-type NAD
+
-dependent consuming deacetylase (
Sac
SrtN, SACE_3798).
In vitro
acetylation/deacetylation of
Sac
AcsA enzyme was studied by Western blotting, and acetylation of lysine residues Lys
237
, Lys
380
, Lys
611
, and Lys
628
was confirmed by mass spectrometry. In a strain devoid of
Sac
AcuA, none of the above-mentioned Lys residues of
Sac
AcsA was acetylated. To our knowledge, the ability of
Sac
AcuA to acetylate multiple Lys residues is unique among AcuA-type acetyltransferases. Results from site-specific mutagenesis experiments showed that the activity of
Sac
AcsA was controlled by lysine acetylation. Lastly, immunoprecipitation data showed that
in vivo
acetylation of
Sac
AcsA was influenced by glucose and acetate availability. These results suggested that reversible acetylation may also be a conserved regulatory posttranslational modification strategy in antibiotic-producing actinomycetes.
Sequence Variation in
tcdA
and
tcdB
of Clostridium difficile: ST37 with Truncated
tcdA
Is a Potential Epidemic Strain in China
Authors: Du Pengcheng , Cao Bo , Wang Jing , Li Wenge , Jia Hongbing , Zhang Wen , Lu Jinxing , Li Zhongjie , Yu Hongjie , Chen Chen , Cheng Ying
Published: June 2014

Clostridium difficile
is a well-known nosocomial infectious pathogen. Research on
C. difficile
infection has primarily focused on strains such as the hypervirulent PCR ribotype 027 (sequence type 1 [ST1]) emerging in Europe and North America. However, other new emerging ribotypes in some countries have attracted attention, such as PCR ribotype 17 (ST37) in Asia and Latin America. We collected 70 strains and sequenced their toxin genes,
tcdA
and
tcdB
. Multilocus sequence typing (MLST) was used to study their population structure. In addition,
tcdA
and/or
tcdB
sequences of 25 other isolates were obtained from GenBank. Single nucleotide polymorphisms (SNPs) were identified and analyzed. Phylogenetic analyses were performed to study toxin gene evolution. All
tcdA
and
tcdB
sequences were divided into 1 of 16 types (denoted A01 to -16 and B01 to -16, respectively). Hypervirulent strain RT027 is A13B12, and RT078 is A14B10, whereas the newly epidemic strain RT017 is A15B13. SNP analysis suggests the possibility of recombination in
tcdB
, perhaps through horizontal gene transfer. SNPs were also found in the sequences corresponding to the PCR primers widely used for toxin detection. Our study shows that ST037 shares a few genotypic features in its
tcdA
and
tcdB
genes with some known hypervirulent strains, indicating that they fall into a unique clade. Our findings can be used to map the relationships among
C. difficile
strains more finely than can be done with less sensitive methods, such as toxinotyping or even MLST, to reveal their inherent epidemiological characteristics.
Use of apixaban for an elderly patient with left atrial thrombus
Authors: Dobashi Shintaro , Fujino Tadashi , Ikeda Takanori
Published: June 2014

An 86-year-old man had long-standing persistent atrial fibrillation, but had not received any anticoagulants. Transthoracic echocardiography revealed a large thrombus formation in the left atrium. We hesitated to use the conventional anticoagulant, warfarin, because he was very old and had dementia. We decided to resolve the thrombus at our outpatient clinic. He was started on the novel oral anticoagulant, apixaban, 2.5 mg twice daily, which is a direct factor Xa (FXa) inhibitor. After 11 weeks on that therapy, the thrombus formation had almost resolved. During oral anticoagulant therapy, no serious bleeding complications, systemic embolisms or strokes were noted. To the best of our knowledge, we are the first to report that apixaban (5 mg/day) can possibly resolve a thrombus formation in the left atrium.
A hunt for the source of sepsis
Authors: Thistleton Samuel , Grandidge Lisa , Sharlala Hisham , Adebajo Adewale
Published: June 2014

A 42-year-old woman presented with a 2-day history of drowsiness, confusion, worsening headache, high fevers, urticarial rash, bilateral leg pains and urinary retention. Preceding this was a 1-month history of headache unresponsive to various analgesics for which her general practitioner started carbamazepine. Suspected central nervous system infection was investigated and treated with cefotaxime. A full septic screen, lumbar puncture and MRI of the spine were all inconclusive. After 3 days, the patient deteriorated and repeated blood tests—initially unremarkable—revealed neutropaenia and acutely deranged liver function. Connective tissue disorder was considered due to a negative septic screen and lack of response to antibiotics, but autoimmune screens failed to reveal a culprit. At this point, carbamazepine was suspected and stopped, after which the patient and her blood results recovered dramatically. This adds to previous reports of known reactions to carbamazepine and reinforces recommendations that patients should be made aware of potential complications of this drug.