bluuebunny/crossref_metadata_2025 huggingface dataset:
CAN A FUNCTIONAL FOOD EXERT A CHOLESTEROL LOWERING EFFECT IN RENAL TRANSPLANT PATIENTS?
Authors: Sutton Debbie , Davey Trish , VenkatRaman G. , Hart Kathryn
Published: February 2009

This study examined whether stanols can exert their cholesterol lowering effect in renal transplant recipients who develop hypercholesterolaemia. The rise in cholesterol is related to the use of cyclosporine.

The study was a randomised parallel‐group intervention study. The Intervention group (I) was given three months supply of stanol containing food products. Fasting serum lipids were measured monthly. Parameters that might influence serum cholesterol were measured on all subjects at the start of the study period and at three months. These included body weight, blood pressure and drug therapy, dietary intake, exercise, smoking and alcohol intake. 84 patients completed the study. Cholesterol was reduced in both groups. The difference between control (C) and I group reached significance at p = 0.0196. Reduction in cholesterol in subjects also using statins was greater in the I group. Functional foods appear to be effective in reducing cholesterol in this group of patients. Data collection with respect to other factors that influence CV risk suggests that an overall assessment of diet and lifestyle as well as cholesterol lowering should be undertaken.
The Effect of Hetastarch (670/0.75) on Urine Specific Gravity and Osmolality in the Dog
Authors: Smart L. , Hopper K. , Aldrich J. , George J. , Kass P. , Haskins S.
Published: February 2009

Background: Urine specific gravity (USG) is used clinically to estimate urine osmolality (UOsm). Although USG has been shown to have a linear correlation with UOsm in dogs, the relationship is altered when there are significant numbers of high molecular weight (MW) molecules in the urine.

Hypothesis: USG would no longer predict UOsm in dogs given intravenous hetastarch (670/0.75)(HES).

Animals: Eight healthy employee‐owned adult dogs.

Methods: Prospective, controlled experimental study. USG and UOsm were measured every 30 minutes from t=0 minutes to t=360 minutes. Dogs were administered 20mL/kg of either NaCl 0.9% (control group, n=4) or HES (treatment group, n=8) IV over 1 hour starting at t=90 minutes.

Results: There was a decrease in UOsm in both groups starting at t=120 minutes and continuing for the study duration, and there was no significant difference in UOsm between treatment and control groups across all time points. There was an appropriate decrease in USG from t=120 minutes for the control group. In the treatment group, USG increased significantly at t=120 minutes (P= .0006), t=150 minutes (P= .0002), and t=180 minutes (P= .0044). The largest increase in USG occurred at t=150 minutes with a mean USG of 1.070 ± 0.021 (range 1.038‐1.104).

Conclusions and clinical importance: Urine specific gravity should not be used to estimate urine solute concentration in dogs following the administration of 20mL/kg of HES. In a clinical setting, the evaluation of USG following this dose of HES may lead to an overestimation of urine concentration.
Prevalence of Deafness in Dogs Heterozygous or Homozygous for the Merle Allele
Authors: Strain G.M. , Clark L.A. , Wahl J.M. , Turner A.E. , Murphy K.E.
Published: February 2009

Background: Deafness in dogs is frequently associated with the pigment genes piebald and merle. Little is known about the prevalence of deafness in dogs carrying the merle allele.

Objective: To determine the prevalence of deafness in dogs heterozygous and homozygous for the merle allele of the mouse Silver pigment locus homolog (SILV) gene.

Animals: One hundred and fifty‐three privately owned merle dogs of different breeds and both sexes.

Methods: Hearing was tested by brainstem auditory‐evoked response and classified as bilaterally hearing, unilaterally deaf, or bilaterally deaf. DNA from buccal cells was genotyped as either heterozygous or homozygous for the merle allele. Deafness association tests among merle genotype, eye color, and sex were performed by the χ2 test.

Results: Deafness prevalence in merles overall was 4.6% unilaterally deaf and 4.6% bilaterally deaf. There was a significant association between hearing status and heterozygous versus homozygous merle genotype. For single merles (Mm), 2.7% were unilaterally deaf and 0.9% were bilaterally deaf. For double merles (MM), 10% were unilaterally deaf and 15% were bilaterally deaf. There was no significant association with eye color or sex.

Conclusions: Deafness prevalence in merle dogs was greater than that in some dog breeds homozygous for the piebald gene, such as the English Cocker Spaniel, but comparable to, or lower than, that in the Dalmatian and white Bull Terrier. Dogs homozygous for the merle allele were significantly more likely to be deaf than heterozygotes.
Activity‐dependent development of inhibitory synapses and innervation pattern: role of GABA signalling and beyond
Authors: Huang Z. Josh
Published: February 2009

GABA‐mediated synaptic inhibition is crucial in neural circuit operations. The development of GABAergic inhibitory synapses and innervation pattern in mammalian neocortex is a prolonged process, extending well into the postnatal period, and is regulated by neural activity and experience. Accumulating evidence supports the hypothesis that GABA signalling acts beyond synaptic transmission and regulates inhibitory synapse development; in other words, similar to glutamate signalling at developing excitatory synapses, GABA may coordinate pre‐ and post‐synaptic maturation at inhibitory synapses. These findings raise numerous questions regarding the underlying mechanisms, including the role of GABA receptors and their link to synaptic adhesion molecules. Since synapse formation is a crucial component of axon growth, GABA signalling may also shape the axon arbor and innervation pattern of inhibitory neurons. A mechanism unique to GABAergic neurons is activity‐dependent GABA synthesis, largely mediated through activity‐regulated transcription of the rate‐limiting enzyme GAD67. Such cell‐wide as well as synaptic regulation of GABA signalling may constitute a mechanism by which input levels and patterns onto GABAergic neurons shape their innervation pattern during circuit development.
Mass∕Heat Transfer in Rotating, Smooth, High-Aspect Ratio (4:1) Coolant Channels With Curved Walls
Authors: Sethuraman Eashwar , Acharya Sumanta , Nikitopoulos Dimitris E.
Published: February 2009

The paper presents an experimental study of heat∕mass transfer coefficient in 4:1 aspect ratio smooth channels with nonuniform cross sections. Curved leading and trailing edges are studied for two curvatures of 9.06 m−1 (0.23 in.−1) and 15.11 m−1 (0.384 in.−1) and for two different curvature configurations. One configuration has curved walls with curvature corresponding to the blade profile (positive curvature on both leading and trailing walls) and the other configuration has leading and trailing walls that curve inward into the coolant passage (negative curvature on the leading surface and positive curvature on the trailing surface). A detailed study at Re=10,000 with rotation numbers in the range of 0–0.07 is undertaken for the two different curvature configurations. All experiments are done for a 90 deg passage orientation with respect to the plane of rotation. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. Only the radially outward flow is considered for the present study. The spanwise mass transfer distributions of fully developed regions of the channel walls are also presented. The mass transfer data from the curved wall channels are compared to those from a smooth 4:1 rectangular duct with similar flow parameters. The local mass transfer data are analyzed mainly for the fully developed region, and area-averaged results are presented to delineate the effect of the rotation number. Heat transfer enhancement especially in the leading wall is seen for the lower curvature channels, and there is a subsequent reduction in the higher curvature channel when compared to the 4:1 rectangular smooth channel. This indicates that an optimal channel wall curvature exists for which heat transfer is the highest.
Effects of Combustor Exit Profiles on Vane Aerodynamic Loading and Heat Transfer in a High Pressure Turbine
Authors: Barringer M. D. , Thole K. A. , Polanka M. D.
Published: February 2009

The flow and thermal fields exiting gas turbine combustors dictate the overall performance of the downstream turbine. The goal of this work was to investigate the effects of engine representative combustor exit profiles on high pressure turbine vane aerodynamics and heat transfer. The various profiles were produced using a nonreacting turbine inlet profile generator in the Turbine Research Facility (TRF) located at the Air Force Research Laboratory (AFRL). This paper reports how the pressure loading and heat transfer along the vane surface was affected by different turbine inlet pressure and temperature profiles at different span locations. The results indicate that the inlet total pressure profiles affected the aerodynamic loading by as much as 10%. The results also reveal that the combination of different total pressure and total temperature profiles significantly affected the vane heat transfer relative to a baseline test with uniform inlet total pressure and total temperature. Near the inner diameter endwall, the baseline heat transfer was reduced 30–40% over the majority of the vane surface. Near the outer dimeter endwall, it was found that certain inlet profiles could increase the baseline heat transfer by 10–20%, while other profiles resulted in a decrease in the baseline heat transfer by 25–35%. This study also shows the importance of knowing an accurate prediction of the local flow driving temperature when determining vane surface heat transfer.
Film Cooling From a Row of Holes Supplemented With Antivortex Holes
Authors: Dhungel Alok , Lu Yiping , Phillips Wynn , Ekkad Srinath V. , Heidmann James
Published: February 2009

The primary focus of this paper is to study the film cooling performance for a row of cylindrical holes each supplemented with two symmetrical antivortex holes, which branch out from the main holes. The antivortex design was originally developed at NASA-Glenn Research Center by James Heidmann, coauthor of this paper. This “antivortex” design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The hole design is intended to counteract the detrimental vorticity associated with standard circular cross-section film cooling holes. The geometry and orientation of the antivortex holes greatly affect the cooling performance downstream, which is thoroughly investigated. By performing experiments at a single mainstream Reynolds number of 9683 based on the freestream velocity and film hole diameter at four different coolant-to-mainstream blowing ratios of 0.5, 1, 1.5, and 2 and using the transient IR thermography technique, detailed film cooling effectiveness and heat transfer coefficients are obtained simultaneously from a single test. When the antivortex holes are nearer the primary film cooling holes and are developing from the base of the primary holes, better film cooling is accomplished as compared to other antivortex hole orientations. When the antivortex holes are laid back in the upstream region, film cooling diminishes considerably. Although an enhancement in heat transfer coefficient is seen in cases with high film cooling effectiveness, the overall heat flux ratio as compared to standard cylindrical holes is much lower. Thus cases with antivortex holes placed near the main holes certainly show promising results.
Migration of Combustor Exit Profiles Through High Pressure Turbine Vanes
Authors: Barringer M. D. , Thole K. A. , Polanka M. D. , Clark J. P. , Koch P. J.
Published: February 2009

The high pressure turbine stage within gas turbine engines is exposed to combustor exit flows that are nonuniform in both stagnation pressure and temperature. These highly turbulent flows typically enter the first stage vanes with significant spatial gradients near the inner and outer diameter endwalls. These gradients can result in secondary flow development within the vane passage that is different than what classical secondary flow models predict. The heat transfer between the working fluid and the turbine vane surface and endwalls is directly related to the secondary flows. The goal of the current study was to examine the migration of different inlet radial temperature and pressure profiles through the high turbine vane of a modern turbine engine. The tests were performed using an inlet profile generator located in the Turbine Research Facility at the Air Force Research Laboratory. Comparisons of area-averaged radial exit profiles are reported as well as profiles at three vane pitch locations to document the circumferential variation in the profiles. The results show that the shape of the total pressure profile near the endwalls at the inlet of the vane can alter the redistribution of stagnation enthalpy through the airfoil passage significantly. Total pressure loss and exit flow angle variations are also examined for the different inlet profiles.
A Conceptual Flutter Analysis of a Packet of Vanes Using a Mass-Spring Model
Authors: Corral Roque , Gallardo Juan Manuel , Martel Carlos
Published: February 2009

The linear aeroelastic stability of a simplified mass-spring model representing the basic dynamics of a packet of Na airfoils has been used to uncover a new type of coupled mode flutter. This simple model retains an essential dynamical feature of the vane packet: the presence of a cluster of Na−1 nearly identical purely structural natural frequencies due to the much larger stiffness of the lower platform as compared to that of the airfoil. Using this model it may be seen that this degeneracy makes the Na−1 associated mode shapes extremely sensible to the addition of small perturbations such as the aerodynamic forces. Since the determination of the aerodynamic vibrational correction (damping and frequency) requires knowing the mode shape, the aerodynamic corrections of the Na−1 cluster modes are now unavoidably coupled together. Moreover, the computation of the aerodynamic correction independently for each structural mode shape leads typically to dangerously overpredicting the stabilizing effect of vane packing. It is shown that the expected stabilizing effect due to the packets may be negligible, depending on the relative frequency split associated with the strength of the aerodynamic forces and realistic structural effects such as the finite stiffness of the lower platform. It is also shown that in these cases, the most unstable mode may be, in a first approximation, very similar to that obtained modeling the stator as a continuous ring.
Numerical Investigation of Tandem Airfoils for Subsonic Axial-Flow Compressor Blades
Authors: McGlumphy Jonathan , Ng Wing-Fai , Wellborn Steven R. , Kempf Severin
Published: February 2009

The tandem airfoil has potential to do more work as a compressor blade than a single airfoil without incurring significantly higher losses. Although tandem blades are sometimes employed as stators, they have not been used in any known commercial rotors. While the long-term goal for this program is development of a commercially viable tandem rotor, this paper discusses tandem airfoils in subsonic, shock-free rectilinear cascade flow. Existing literature data on tandem airfoils in rectilinear cascades have been compiled and presented in a Lieblein loss versus loading correlation. Large scatter in the data gave motivation to conduct an extensive 2D computational fluid dynamics (CFD) study evaluating the overall performance as a function of the relative positions of the forward and aft airfoils. CFD results were consistent with trends in the open literature, both of which indicate that a properly designed tandem airfoil can outperform a comparable single airfoil on and off design. The general agreement of the CFD and literature data serves as a validation for the computational approach.
Forced Convection Heat Transfer in Channels With Rib Turbulators Inclined at 45 deg
Authors: Tanda Giovanni , Abram Roberto
Published: February 2009

Local and average Nusselt numbers and friction factors are presented for rectangular channels with an aspect ratio of 5 and angled rib turbulators inclined at 45 deg with parallel orientations on one and two surfaces of the channel. The convective fluid was air, and the Reynolds number varied from 9000 to 35,500. The ratio of rib height to hydraulic diameter was 0.09, with the rib pitch-to-height ratio equal to 13.33 or 6.66. Experiments were based on the use of heating foils (for the attainment of uniform heat flux condition) and of the steady-state liquid crystal thermography (for the identification of isotherm lines and the reconstruction of local heat transfer coefficient). Local results showed quasiperiodic profiles of Nusselt number in the streamwise direction, whose features were strongly affected by the value of rib pitch and by the spanwise coordinate. For all the investigated geometries a heat transfer augmentation, relative to the fully developed smooth channel, was found; when inclined rib turbulators were placed on two opposite surfaces of the channel, the full-surface Nusselt number was higher (by 10–19%) than that for the one-ribbed wall channel, but pressure drop penalties also increased by a factor of about 3. For both the one- and two-ribbed wall channels, the best heat transfer performance for a constant pumping power, in the explored range of Reynolds number, was generally achieved by the larger rib pitch-to-height ratio (=13.33).
Unsteady Simulation of an Axial Compressor Stage With Casing and Blade Passive Treatments
Authors: Gourdain Nicolas , Leboeuf Francis
Published: February 2009

This paper deals with the numerical simulation of technologies to increase the compressor performances. The objective is to extend the stable operating range of an axial compressor stage using passive control devices located in the tip region. First, the behavior of the tip leakage flow is investigated in the compressor without control. The simulation shows an increase in the interaction between the tip leakage flow and the main flow when the mass flow is reduced, a phenomenon responsible for the development of a large flow blockage region at the rotor leading edge. A separation of the rotor suction side boundary layer is also observed at near stall conditions. Then, two approaches are tested in order to control these flows in the tip region. The first one is a casing treatment with nonaxisymmetric slots. The method showed a good ability to control the tip leakage flow but failed to reduce the boundary layer separation on the suction side. However, an increase in the operability was observed but with a penalty for the efficiency. The second approach is a blade treatment that consists of a longitudinal groove built in the tip of each rotor blade. The simulation pointed out that the device is able to control partially all the critical flows with no penalty for the efficiency. Finally, some recommendations for the design of passive treatments are presented.
Pharmacokinetics of Hydroxychloroquine and Its Clinical Implications in Chemoprophylaxis against Malaria Caused byPlasmodium vivax
Authors: Lim Hyeong-Seok , Im Jeong-Soo , Cho Joo-Youn , Bae Kyun-Seop , Klein Terry A. , Yeom Joon-Sup , Kim Tae-Seon , Choi Jae-Seon , Jang In-Jin , Park Jae-Won
Published: February 2009

Hydroxychloroquine (HCQ) is an antimalarial drug used as chemoprophylaxis against malaria caused byPlasmodium vivaxin the Republic of Korea Army (ROKA). In this study, we evaluated the pharmacokinetics (PK) of HCQ and its metabolites and the relationship between the PK of HCQ and the effect of treatment of HCQ on vivax malaria in South Koreans. Three PK studies of HCQ were conducted with 91 healthy subjects and patients with vivax malaria. Plasma concentrations were analyzed by noncompartmental and mixed-effect modeling approaches. A two-compartment model with first-order absorption best described the data. The clearance and the central and peripheral volumes of distribution were 15.5 liters/h, 733 liters, and 1,630 liters, respectively. We measured the plasma concentrations of HCQ in patients with prophylactic failure of HCQ and compared them with the prediction intervals of the simulated concentrations for HCQ from the final PK model built in this study. In 71% of the patients with prophylactic failure, the plasma concentrations of HCQ were below the lower bounds of the 95% prediction interval, while only 8% of them showed higher levels than the upper bounds of the 95% prediction interval. We report that a significant cause of prophylactic failure among the individuals in ROKA was ascribed to plasma concentrations of HCQ lower than those predicted by the PK model. However, prophylactic failure despite sufficient plasma concentrations of HCQ was confirmed in several individuals, warranting continued surveillance to monitor changes in the HCQ susceptibility ofPlasmodium vivaxin the Republic of Korea.
Contribution of the Autolysin AtlA to the Bactericidal Activity of Amoxicillin against
Enterococcus faecalis
JH2-2
Authors: Bravetti Anne-Lise , Mesnage Stéphane , Lefort Agnès , Chau Françoise , Eckert Catherine , Garry Louis , Arthur Michel , Fantin Bruno
Published: February 2009

The bactericidal activity of amoxicillin was investigated against
Enterococcus faecalis
JH2-2 and against an isogenic mutant deficient in the production of the
N
-acetylglucosaminidase AtlA. Comparison of the two strains indicated that this autolysin contributes to killing by amoxicillin both in vitro and in a rabbit model of experimental endocarditis.
In Vitro Activities of Fluconazole and Voriconazole against Clinical Isolates of
Candida
spp. Determined by Disk Diffusion Testing in Turin, Italy
Authors: Mandras Narcisa , Tullio Vivian , Allizond Valeria , Scalas Daniela , Banche Giuliana , Roana Janira , Robbiano Francesca , Fucale Giacomo , Malabaila Aurelio , Cuffini Anna Maria , Carlone Nicola
Published: February 2009

The in vitro activities of fluconazole and voriconazole against 1,024 clinical isolates of
Candida
spp. were determined by the agar disk diffusion test using the Clinical and Laboratory Standards Institute (CLSI) M44-A guidelines. The results of this investigation demonstrated the broad-spectrum in vitro activity of voriconazole, relative to that of fluconazole, against yeasts tested, in particular fluconazole-resistant isolates, such as
Candida krusei
that showed high susceptibility to voriconazole. The situation in Turin, Italy, is quite similar to that of the rest of Italy, reflecting the worldwide trend.
Steady-State Pharmacokinetics of Abacavir in Plasma and Intracellular Carbovir Triphosphate following Administration of Abacavir at 600 Milligrams Once Daily and 300 Milligrams Twice Daily in Human Immunodeficiency Virus-Infected Subjects
Authors: Moyle Graeme , Boffito Marta , Fletcher Carl , Higgs Chris , Hay Phillip E. , Song Ivy H. , Lou Yu , Yuen Geoffrey J. , Min Sherene S. , Guerini Elena M.
Published: February 2009

Abacavir (ABC) is administered either at 600 mg once daily (ABC 600 mg QD) or 300 mg twice daily (ABC 300 mg BID) in anti-human immunodeficiency virus (anti-HIV) combination therapy. Although ABC plasma pharmacokinetics following each regimen has been well defined, no study has directly compared the regimens with respect to pharmacokinetics of ABC's active intracellular anabolite, carbovir-triphosphate (CBV-TP). In an open-label, two-period, crossover study, 34 HIV-infected male and female subjects stabilized on antiretroviral regimens containing either ABC 600 mg QD or ABC 300 mg BID received their usual doses on days −1 and 1 and then switched regimens for days 2 to 11. Serial blood samples collected on days 1 and 11 were assayed for plasma ABC and intracellular CBV-TP concentrations using validated high-performance liquid chromatography-tandem mass spectrometry methods. Pharmacokinetic parameters were calculated using noncompartmental methods. Analysis of variance with a mixed-effect model was performed for treatment and gender comparisons. In 27 evaluable subjects, the regimens provided bioequivalent ABC daily areas under the concentration-time curve from 0 to 24 h (AUC
0-24
) and comparable CBV-TP concentrations at the end of the dosing interval (
C
τ
). As expected, ABC QD resulted in 109% higher ABC maximum concentrations of drug in plasma (
C
max
) than did ABC BID. ABC QD also resulted in 32% higher CBV-TP AUC
0-24
and 99% higher CBV-TP
C
max
than did ABC BID. Females had a 38% higher weight-adjusted ABC AUC
0-24
and 81% higher weight-adjusted CBV-TP AUC
0-24
than did males. Virologic suppression was maintained during regimen switch, and no tolerability differences between regimens were observed. In conclusion, this study showed that ABC 600 mg QD and ABC 300 mg BID regimens led to similar intracellular CBV-TP
C
τ
values, thus providing pharmacokinetic support for the interchangeability of these two regimens. Women had higher intracellular CBV-TP exposure than did men.
Urinary Bactericidal Activity of Doripenem versus That of Levofloxacin in Patients with Complicated Urinary Tract Infections or Pyelonephritis
Authors: Wagenlehner Florian M. E. , Wagenlehner Christine , Redman Rebecca , Weidner Wolfgang , Naber Kurt G.
Published: February 2009

The aim of this study was to investigate the urinary bactericidal titers (UBTs) and 24-h area under the UBT-versus-time curve (AUBT) of intravenous doripenem (500 mg every 8 h [q8h]), a new carbapenem, versus those of intravenous levofloxacin (250 mg q24h) in patients with complicated urinary tract infections (cUTIs) or pyelonephritis. UBTs and AUBTs are pharmacokinetic/pharmacodynamic parameters able to reflect the activity of an antimicrobial substance in the urine. Doripenem and levofloxacin show comparable urinary excretion of approximately 80% and are therefore registered for the treatment of UTIs. In order to assess and compare the urinary antimicrobial activities of the two substances, UBTs were investigated for 24 patients (10 treated with doripenem and 14 with levofloxacin) for 31 uropathogens and one control strain. Eight strains were tested for all patients and 27 only in the urine of the corresponding patient. Median UBTs (AUBTs) of doripenem for the uropathogens tested ranged between 1.5 and 65,536 (224 and 909,312) and were significantly higher than median UBTs (AUBTs) of levofloxacin, ranging between 0 and 128 (0 and 2,208). Eight microbiological failures were observed, three after doripenem treatment and five after levofloxacin treatment. For levofloxacin, microbiological failures correlated well with low UBTs and AUBTs, whereas for doripenem there was no correlation. From this study, a calculated target attainment rate for levofloxacin predicting therapeutic success in patients with UTIs approximated mean UBTs of 100 over 24 h or AUBTs of 2,240. Doripenem demonstrated excellent urinary bactericidal activity with the dose administered and appears to be a good alternative in the empirical treatment of cUTI.
Population Pharmacokinetics of High-Dose, Prolonged-Infusion Cefepime in Adult Critically Ill Patients with Ventilator-Associated Pneumonia
Authors: Nicasio Anthony M. , Ariano Robert E. , Zelenitsky Sheryl A. , Kim Aryun , Crandon Jared L. , Kuti Joseph L. , Nicolau David P.
Published: February 2009

A population pharmacokinetic model of cefepime was constructed from data from adult critical care patients with ventilator-associated pneumonia (VAP). A total of 32 patients treated with high-dose cefepime, 2 g every 8 h (3-h infusion) or a renal function-adjusted equivalent dose, were randomized into two groups—26 for the initial model and 6 for model validation. Serum samples of cefepime were collected at steady state. Nonparametric adaptive grid population modeling was employed using a two-compartment
K
slope
pharmacokinetic model relating the elimination rate constant (
K
10
) to renal function, as defined by creatinine clearance (CL
CR
), and central distribution volume (
V
1
) to total body weight (TBW). The final model was described by the following equations:
K
10
= 0.0027 × CL
CR
+ 0.071 h
−1
and
V
1
= TBW × 0.21 liter/kg. The median intercompartmental transfer constants
K
12
and
K
21
were 0.780 h
−1
and 0.472 h
−1
, respectively. Using these median parameter estimates, the bias, precision, and coefficient of determination for the initial model were 11.3 μg/ml, 24.0 μg/ml, and 26%, respectively. The independent validation group displayed a bias, precision, and coefficient of determination of −1.64 μg/ml, 17.1 μg/ml, and 62%, respectively. Time-concentration profiles were assessed for various dosing regimens, using 5,000-patient Monte Carlo simulations. Among the regimens, the likelihoods of 2 g every 8 h (3-h infusion) achieving free drug concentrations above the MIC for 50% of the dosing interval were 91.8%, 78.1%, and 50.3% for MICs of 8, 16, and 32 μg/ml, respectively. This study provides a pharmacokinetic model capable of predicting cefepime concentrations in critically ill patients with VAP.
Intracellular Activity of Antibiotics in a Model of Human THP-1 Macrophages Infected by a
Staphylococcus aureus
Small-Colony Variant Strain Isolated from a Cystic Fibrosis Patient: Pharmacodynamic Evaluation and Comparison with Isogenic Normal-Phenotype and Revertant Strains
Authors: Nguyen Hoang Anh , Denis Olivier , Vergison Anne , Theunis Anne , Tulkens Paul M. , Struelens Marc J. , Van Bambeke Françoise
Published: February 2009

Small-colony variant (SCV) strains of
Staphylococcus aureus
show reduced antibiotic susceptibility and intracellular persistence, potentially explaining therapeutic failures. The activities of oxacillin, fusidic acid, clindamycin, gentamicin, rifampin, vancomycin, linezolid, quinupristin-dalfopristin, daptomycin, tigecycline, moxifloxacin, telavancin, and oritavancin have been examined in THP-1 macrophages infected by a stable thymidine-dependent SCV strain in comparison with normal-phenotype and revertant isogenic strains isolated from the same cystic fibrosis patient. The SCV strain grew slowly extracellularly and intracellularly (1- and 0.2-log CFU increase in 24 h, respectively). In confocal and electron microscopy, SCV and the normal-phenotype bacteria remain confined in acid vacuoles. All antibiotics tested, except tigecycline, caused a net reduction in bacterial counts that was both time and concentration dependent. At an extracellular concentration corresponding to the maximum concentration in human serum (total drug), oritavancin caused a 2-log CFU reduction at 24 h; rifampin, moxifloxacin, and quinupristin-dalfopristin caused a similar reduction at 72 h; and all other antibiotics had only a static effect at 24 h and a 1-log CFU reduction at 72 h. In concentration dependence experiments, response to oritavancin was bimodal (two successive plateaus of −0.4 and −3.1 log CFU); tigecycline, moxifloxacin, and rifampin showed maximal effects of −1.1 to −1.7 log CFU; and the other antibiotics produced results of −0.6 log CFU or less. Addition of thymidine restored intracellular growth of the SCV strain but did not modify the activity of antibiotics (except quinupristin-dalfopristin). All drugs (except tigecycline and oritavancin) showed higher intracellular activity against normal or revertant phenotypes than against SCV strains. The data may help rationalizing the design of further studies with intracellular SCV strains.
Intracellular Activity of Antibiotics in a Model of Human THP-1 Macrophages Infected by a
Staphylococcus aureus
Small-Colony Variant Strain Isolated from a Cystic Fibrosis Patient: Study of Antibiotic Combinations
Authors: Nguyen Hoang Anh , Denis Olivier , Vergison Anne , Tulkens Paul M. , Struelens Marc J. , Van Bambeke Françoise
Published: February 2009

In a companion paper (H. A. Nguyen et al., Antimicrob. Agents Chemother. 53:1434-1442, 2009), we showed that vancomycin, oxacillin, fusidic acid, clindamycin, linezolid, and daptomycin are poorly active against the intracellular form of a thymidine-dependent small-colony variant (SCV) strain isolated from a cystic fibrosis patient and that the activity of quinupristin-dalfopristin, moxifloxacin, rifampin, and oritavancin remains limited (2- to 3-log CFU reduction) compared to their extracellular activity. Antibiotic combination is a well-known strategy to improve antibacterial activity, which was examined here against an intracellular SCV strain using combinations with either rifampin or oritavancin. Time-kill curve analysis using either concentrations that caused a static effect for each antibiotic individually or concentrations corresponding to the maximum concentration in human serum showed largely divergent effects that were favorable when antibiotics were combined with rifampin at low concentrations only and with oritavancin at both low and high concentrations. The nature of the interaction between rifampin, oritavancin, and moxifloxacin was further examined using the fractional maximal effect method, which allows categorization of the effects of combinations when dose-effect relationships are not linear. Rifampin and oritavancin were synergistic at all concentration ratios investigated. Oritavancin and moxifloxacin were also synergistic but at high oritavancin concentrations only. Rifampin and moxifloxacin were additive. This approach may help in better assessing and improving the activity of antibiotics against intracellular SCV strains.
Chlamydia trachomatis
Laboratory Strains versus Recent Clinical Isolates: Implications for Routine Microbicide Testing
Authors: Skinner M. C. , Stamm W. E. , Lampe M. L.
Published: February 2009

A topical microbicide that women can use to prevent sexually transmitted diseases (STDs) is essential, and many microbicide candidates are being tested for activity against human immunodeficiency virus and other STDs, including
Chlamydia trachomatis
. Screening assays for assessing the activity of microbicides against
C. trachomatis
are typically done with laboratory-adapted strains, but it is possible that recent clinical isolates may have different susceptibilities to microbicides, as has been seen with
Neisseria gonorrhoeae
and
Lactobacillus
spp. (B. J. Moncla and S. L. Hillier, Sex. Transm. Dis. 32:491-494, 2005). We utilized three types of microbicides to help define this aspect of our assay to test microbicides against
C. trachomatis
in vitro. To simulate conditions of transmission, we used an assay that we previously developed in which we exposed chlamydial elementary bodies to microbicides prior to contact with epithelial cells. We first determined the toxicity of microbicides to the cells used to culture
Chlamydia trachomatis
in the assay and, if necessary, modified the assay to eliminate toxicity at the concentrations tested. We compared the sensitivities of recent clinical isolates of
Chlamydia trachomatis
versus laboratory strains of the same serovar and found major differences in sensitivity to nonoxynol-9 (non-9), but only minor differences were seen with the other microbicides. We thus conclude that when assessing activity of potential topical microbicides versus the obligate intracellular bacteria
C. trachomatis
, the use of recent clinical isolates may not be necessary to draw a conclusion about a microbicide's effectiveness. However, it is important to keep in mind that differences (like those seen with non-9) are possible and that clinical isolates could be included in later stages of testing.
Azithromycin in
Pseudomonas aeruginosa
Biofilms: Bactericidal Activity and Selection of
nfxB
Mutants
Authors: Mulet Xavier , Maciá María D. , Mena Ana , Juan Carlos , Pérez José L. , Oliver Antonio
Published: February 2009

Azithromycin (AZM) has shown promising results in the treatment of
Pseudomonas aeruginosa
chronic lung infections such as those occurring in cystic fibrosis (CF) patients. We evaluated the effect of hypermutation and alginate hyperproduction on the bactericidal activity and resistance development to AZM in
P. aeruginosa
biofilms. Strains PAO1, its
mucA
mutant (PAOMA), and their respective
mutS
-deficient hypermutable derivatives (PAOMS and PAOMSA) were used. Biofilms were incubated with several AZM concentrations for 1, 2, 4, or 7 days, and the numbers of viable cells were determined. During the first 2 days, AZM showed bactericidal activity for all the strains, but in extended AZM incubation for strain PAOMS and especially strain PAOMSA, a marked increased in the number of viable cells was observed, particularly at 4 μg/ml. Biofilms formed by the lineages recovered from the 7-day experiments showed enhanced AZM resistance. Furthermore, most of the independent lineages studied, including those obtained from biofilms treated with AZM concentrations as low as 0.5 μg/ml, showed MexCD-OprJ hyperexpression and mutations in
nfxB
. The role of
nfxB
mutation in AZM resistance was further confirmed through the characterization of
nfxB
and
mexD
knockout mutants. Results from this work show that, although AZM exhibits bactericidal activity against
P. aeruginosa
biofilms, resistant mutants are readily selected and that, furthermore, they frequently show cross-resistance to other unrelated antipseudomonal agents such as ciprofloxacin or cefepime but hypersusceptibility to others such as imipenem or tobramycin. Therefore, these results should help guide the selection of appropriate antipseudomonal therapies in CF patients under AZM maintenance treatment.
Antistaphylococcal Activity of Dihydrophthalazine Antifolates, a Family of Novel Antibacterial Drugs
Authors: Clark Catherine , Ednie Lois M. , Lin Gengrong , Smith Kathy , Kosowska-Shick Klaudia , McGhee Pamela , Dewasse Bonifacio , Beachel Linda , Caspers Patrick , Gaucher Bérangère , Mert Gürkan , Shapiro Stuart , Appelbaum Peter C.
Published: February 2009

For a panel of 153
Staphylococcus aureus
clinical isolates (including 13 vancomycin-intermediate or heterogeneous vancomycin-intermediate and 4 vancomycin-resistant strains), MIC
50
s and MIC
90
s of three novel dihydrophthalazine antifolates, BAL0030543, BAL0030544, and BAL0030545, were 0.03 and 0.25 μg/ml, respectively, for methicillin-susceptible strains and 0.03 and ≤0.25 μg/ml, respectively, for methicillin-resistant strains. For a panel of 160 coagulase-negative staphylococci (including 5 vancomycin-intermediate and heterogeneous vancomycin-intermediate strains and 7 linezolid-nonsusceptible strains), MIC
50
s and MIC
90
s were ≤0.03 and ≤0.06 μg/ml, respectively, for methicillin-susceptible strains and 0.06 and 0.5 μg/ml, respectively, for methicillin-resistant strains. Vancomycin was active against 93.0% of 313 staphylococci examined; linezolid was active against all
S. aureus
strains and 95.6% of coagulase-negative staphylococcus strains, whereas elevated MICs of clindamycin, minocycline, trimethoprim, and rifampin for some strains were observed. At 4× MIC, the dihydrophthalazines were bactericidal against 11 of 12 staphylococcal strains surveyed. The prolonged serial passage of some staphylococcal strains in the presence of subinhibitory concentrations of BAL0030543, BAL0030544, and BAL0030545 produced clones for which dihydrophthalazines showed high MICs (>128 μg/ml), although rates of endogenous resistance development were much lower for the dihydrophthalazines than for trimethoprim. Single-step platings of naïve staphylococci onto media containing dihydrophthalazine antifolates indicated considerable variability among strains with respect to preexistent subpopulations nonsusceptible to dihydrophthalazine antifolates.
Low Plasma Membrane Expression of the Miltefosine Transport Complex Renders
Leishmania braziliensis
Refractory to the Drug
Authors: Sánchez-Cañete María P. , Carvalho Luís , Pérez-Victoria F. Javier , Gamarro Francisco , Castanys Santiago
Published: February 2009

Miltefosine (hexadecylphosphocholine, MLF) is the first oral drug with recognized efficacy against both visceral and cutaneous leishmaniasis. However, some clinical studies have suggested that MLF shows significantly less efficiency against the cutaneous leishmaniasis caused by
Leishmania braziliensis
. In this work, we have determined the cellular and molecular basis for the natural MLF resistance observed in
L
.
braziliensis
. Four independent
L
.
braziliensis
clinical isolates showed a marked decrease in MLF sensitivity that was due to their inability to internalize the drug. MLF internalization in the highly sensitive
L
.
donovani
species requires at least two proteins in the plasma membrane, LdMT, a P-type ATPase involved in phospholipid translocation, and its β subunit, LdRos3. Strikingly,
L
.
braziliensis
parasites showed highly reduced levels of this MLF translocation machinery at the plasma membrane, mainly because of the low expression levels of the β subunit, LbRos3. Overexpression of LbRos3 induces increased MLF sensitivity not only in
L
.
braziliensis
promastigotes but also in intracellular amastigotes. These results further highlight the importance of the MLF translocation machinery in determining MLF potency and point toward the development of protocols to routinely monitor MLF susceptibility in geographic areas where
L
.
braziliensis
might be prevalent.
Interconnections between Sigma B,
agr
, and Proteolytic Activity in
Staphylococcus aureus
Biofilm Maturation
Authors: Lauderdale Katherine J. , Boles Blaise R. , Cheung Ambrose L. , Horswill Alexander R.
Published: February 2009

Staphylococcus aureus
is a proficient biofilm former on host tissues and medical implants. We mutagenized
S. aureus
strain SH1000 to identify loci essential for
ica
-independent mechanisms of biofilm maturation and identified multiple insertions in the
rsbUVW-sigB
operon. Following construction and characterization of a
sigB
deletion, we determined that the biofilm phenotype was due to a lack of sigma factor B (SigB) activity. The phenotype was conserved in a
sigB
mutant of USA300 strain LAC, a well-studied community-associated methicillin-resistant
S. aureus
isolate. We determined that
agr
RNAIII levels were elevated in the
sigB
mutants, and high levels of RNAIII expression are known to have antibiofilm effects. By introducing an
agr
mutation into the SH1000 or LAC
sigB
deletion strain,
S. aureus
regained biofilm capacity, indicating that the biofilm phenotype was
agr
dependent. Protease activity is linked to
agr
activity and
ica
-independent biofilm formation, and we observed that the protease inhibitors phenylmethylsulfonyl fluoride and α-macroglobulin could reverse the
sigB
biofilm defect. Similarly, inactivating genes encoding both the aureolysin and Spl extracellular proteases in the
sigB
mutant restored biofilm capacity. Due to the growing link between murein hydrolase activity and biofilm maturation, autolysin zymography was performed, which revealed an altered profile in the
sigB
mutant; again, the phenotype could be repaired through protease inactivation. These findings indicate that the lack of SigB activity results in increased RNAIII expression, thus elevating extracellular protease levels and altering the murein hydrolase activity profile. Altogether, our observations demonstrate that SigB is an essential regulator of
S. aureus
biofilm maturation.
Generation of Antibody Responses to Pneumococcal Capsular Polysaccharides Is Independent of CD1 Expression in Mice
Authors: Moens Leen , Jeurissen Axel , Nierkens Stefan , Boon Louis , Van Kaer Luc , Kasran Ahmad , Wuyts Greet , Ceuppens Jan L. , Bossuyt Xavier
Published: February 2009

Streptococcus pneumoniaeis a bacterial microorganism that frequently causes serious infection, particularly in children and the elderly. Protection against infection withS. pneumoniaeis based mainly on the generation of antibodies to the pneumococcal capsular polysaccharides (caps-PS), but the mechanisms responsible for the generation of anticapsular antibodies remain incompletely understood. The aim of the present study was to evaluate the role of CD1-restricted T cells in the antibody response to caps-PS. When immunized with Pneumo23, wild-type mice and CD1 knockout mice on BALB/c and C57BL/6 backgrounds generated immunoglobulin M (IgM) and IgG antibody responses to soluble caps-PS that were comparable. Similar results were obtained after immunization with heat-inactivatedS. pneumoniae. The IgM and IgG antibody response of wild-type mice to Pneumo23 was not affected by an antagonizing monoclonal anti-CD1 antibody treatment. In summary, our data provide evidence that the antibody response to caps-PS is generated independently of CD1 expression.
Modelling of Infection by EnteropathogenicEscherichia coliStrains in Lineages 2 and 4 Ex Vivo and In Vivo by UsingCitrobacter rodentiumExpressing TccP
Authors: Girard Francis , Crepin Valérie F. , Frankel Gad
Published: February 2009

EnteropathogenicEscherichia coli(EPEC) strains colonize the human gut mucosa via attaching-and-effacing (A/E) lesion formation, while in vitro they employ diverse strategies to trigger actin polymerization. Strains belonging to the EPEC-1 lineage trigger strong actin polymerization via tyrosine phosphorylation of the type III secretion system (T3SS) effector Tir, recruitment of Nck, and activation of N-WASP. Strains belonging to EPEC-2 and EPEC-4 can trigger strong actin polymerization by dual mechanisms, since while employing the Tir-Nck pathway they can additionally activate N-WASP via the T3SS effectors TccP2 and TccP, respectively. It is currently not known if the ability to trigger actin polymerization by twin mechanisms increases in vivo virulence or fitness. Since mice are resistant to EPEC infection, in vivo studies are frequently done using the murine model pathogenCitrobacter rodentium, which shares with EPEC-1 strains the ability to induce A/E lesions and trigger strong actin polymerization via the Tir:Nck pathway. In order to model infections with EPEC-2 and EPEC-4, we constructedC. rodentiumstrains expressing TccP. Using a mouse intestinal in vitro organ culture model and oral gavage into C57BL/6 mice, we have shown that TccP can cooperate with Tir ofC. rodentium. The recombinant strains induced typical A/E lesions ex vivo and in vivo. Expression of TccP did not alterC. rodentiumcolonization dynamics or pathology. In competition with the wild-type strain, expression of TccP inC. rodentiumdid not confer a competitive advantage.
Modulation of Cell Wall Structure and Antimicrobial Susceptibility by a
Staphylococcus aureus
Eukaryote-Like Serine/Threonine Kinase and Phosphatase
Authors: Beltramini Amanda M. , Mukhopadhyay Chitrangada D. , Pancholi Vijay
Published: February 2009

It is well established that prokaryotes and eukaryotes alike utilize phosphotransfer to regulate cellular functions. One method by which this occurs is via eukaryote-like serine/threonine kinase (ESTK)- and phosphatase (ESTP)-regulated pathways. The role of these enzymes in
Staphylococcus aureus
has not yet been examined. This resilient organism is a common cause of hospital-acquired and community-associated infections, infecting immunocompromised and immunocompetent hosts alike. In this study, we have characterized a major functional ESTK (STK) and ESTP (STP) in
S. aureus
and found them to be critical modulators of cell wall structure and susceptibility to cell wall-acting β-lactam antibiotics. By utilizing gene knockout strategies, we created
S. aureus
N315 mutants lacking STP and/or STK. The strain lacking both STP and STK displayed notable cell division defects, including multiple and incomplete septa, bulging, and irregular cell size, as observed by transmission electron microscopy. Mutants lacking STP alone displayed thickened cell walls and increased resistance to the peptidoglycan-targeting glycylglycine endopeptidase lysostaphin, compared to the wild type. Additionally, mutant strains lacking STK or both STK and STP displayed increased sensitivity to cell wall-acting cephalosporin and carbapenem antibiotics. Together, these results indicate that
S. aureus
STK- and STP-mediated reversible phosphorylation reactions play a critical role in proper cell wall architecture, and thus the modulation of antimicrobial resistance, in
S. aureus
.