Comparative Effectiveness of Linezolid and Vancomycin Among a National Veterans Affairs Cohort with Methicillin-Resistant Staphylococcus aureus Pneumonia

Study Objective: As variability in vancomycin dosing, susceptibility, and tolerability has driven the need to compare newer agents with vancomycin in real-world clinical settings, we sought to quantify the effectiveness of linezolid compared with vancomycin on clinical outcomes for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia. Design: Retrospective cohort study. Data Source: Veterans Health Administration national databases. Patients: Adults admitted to Veterans Affairs hospitals between January 2002 and September 2010 with diagnosis codes for MRSA and pneumonia, and who initiated and received at least 3 days of continuous intravenous vancomycin therapy (4943 patients) or intravenous or oral linezolid therapy (328 patients) while in the hospital. Measurements and Main Results: Propensity score–adjusted Cox proportional hazards regression models quantified the effect of linezolid compared with vancomycin on time to 30-day mortality (primary outcome), therapy change, hospital discharge, discharge from intensive care, intubation, 30-day readmission, and 30-day MRSA reinfection. In addition, a composite outcome of clinical success was defined as discharge from the hospital or intensive care unit by day 14 after treatment initiation, in the absence of death, therapy change, or intubation by day 14. Subgroup analyses were performed in a validated microbiology-confirmed MRSA subgroup and clinical subgroup meeting clinical criteria for infection. Although a number of baseline variables differed significantly between the vancomycin and linezolid treatment groups, balance was achieved within propensity score quintiles. A significantly lower rate of therapy change was observed in the linezolid group (adjusted hazard ratio [HR] 0.68, 95% confidence interval [CI] 0.48–0.96). The clinical success rate was significantly higher among patients treated with linezolid (adjusted HR 1.25, 95% CI 1.07–1.47). Comparable findings were observed in the subgroup analyses. Conclusion: Individual clinical outcomes were similar among patients treated for MRSA pneumonia with linezolid compared with vancomycin. A significantly higher rate of the composite outcome of clinical success was observed, however, among patients treated with linezolid compared with vancomycin

Predictors of Clinical Success Among a National Veterans Affairs Cohort With Methicillin-Resistant Staphylococcus aureus Pneumonia

Background: The treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is exceedingly complicated, which is concerning because of the high mortality rate associated with the infection. Identification of independent predictors of clinical success can optimize patient care by assisting clinicians in treatment decisions. Objectives: We sought to identify independent predictors of clinical success in a national Veterans Affairs (VA) cohort of MRSA pneumonia patients. Methods: A nested case-control study was conducted among a cohort of VA patients with MRSA pneumonia receiving linezolid or vancomycin between January 2002 and September 2010. Cases included those demonstrating clinical success, defined as discharge from the hospital or intensive care unit (ICU) by day 14 after treatment initiation, in the absence of death, therapy change, or intubation by day 14. Controls represented non-success, defined as therapy change, intubation, ICU admission, re-admission, or death between treatment initiation and day 14. The potential predictors assessed included treatment, patient demographics and admission characteristics, previous healthcare and medication exposures, comorbidities, and medical history. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated from logistic regression. Results: Our study included 2442 cases of clinical success and 1290 controls. Demographics varied between the clinical success and non-success groups, including age, race, and region of facility. A current diagnosis of chronic respiratory disease (46% vs 42%) and diagnosis of pneumonia in the year prior to the MRSA pneumonia admission (37% vs 32%) were both more common in the clinical success group. Despite these significant differences, only two predictors of clinical success were identified in our study: previous complication of an implant or graft, including mechanical complications and infections, in the year prior to the MRSA pneumonia admission (OR, 1.55; 95% CI, 1.17–2.06) and treatment with linezolid (1.53; 1.12–2.10). Predictors of non-success included concomitant urinary tract infection diagnosis (OR, 0.82; 95% CI, 0.70–0.96), intravenous line (0.76; 0.66–0.89), previous coagulopathy (0.74; 0.56–0.96), previous amputation procedure (0.72; 0.53–0.98), current coagulopathy diagnosis (0.71; 0.53–0.96), dialysis (0.54; 0.38–0.76), multiple inpatient procedures (0.53; 0.45–0.62), inpatient surgery (0.48; 0.41–0.57), and previous endocarditis (0.24; 0.07–0.81). Discussion: MRSA pneumonia tends to affect complex patients, and identification of the predictors of clinical success is useful when considering different therapeutic approaches. Conclusions: In a national cohort of VA patients with MRSA pneumonia, treatment was the only modifiable variable predicting clinical success

Magnetic torque study of the temperature dependent anisotropy parameter in overdoped superconducting single-crystal YBa_2Cu_3O_7

An overdoped YBa2Cu3O7 single crystal was studied by SQUID and torque magnetometry in order to investigate the temperature dependence of the anisotropy parameter close to the transition temperature T_c (0.87 T_c < T < T_c). Angle dependent torque measurements were performed and analyzed with the widely used Kogan model [Phys. Rev. B 38, 7049 (1988)] as well as with an extended model by Hao and Clem [Phys. Rev. Lett. 67, 2371 (1991)], taking into account the influence of the vortex cores on the magnetization. Both approaches yield similar results, with an out-of-plane anisotropy parameter around 6.5 which slightly increases with decreasing temperature, and a temperature independent in-plane anisotropy parameter gamma_ab}= 1.12(5).Comment: 7 pages, 6 figures, version2 - accepted for publication in PR

Magnetic structure and phase diagram of the Heisenberg-Ising spin chain antiferromagnetic PbCo2_{2}V2_{2}O8_{8}

The effective spin-1/2 antiferromagnetic Heisenberg-Ising chain materials, ACo$_2$V$_2$O$_8$, A = Sr, Ba, are a rich source of exotic fundamental phenomena and have been investigated for their model magnetic properties both in zero and non-zero magnetic fields. Here we investigate a new member of the family, namely PbCo$_2$V$_2$O$_8$. We synthesize powder and single crystal samples of PbCo$_2$V$_2$O$_8$ and determine its magnetic structure using neutron diffraction. Furthermore, the magnetic field/temperature phase diagrams for magnetic field applied along the c, a, and [110] crystallographic directions in the tetragonal unit cell are determined via magnetization and heat capacity measurements. A complex series of phases and quantum phase transitions are discovered that depend strongly on both the magnitude and direction of the field. Our results show that \pcvo is an effective spin-1/2 antiferromagnetic Heisenberg-Ising chain with properties that are in general comparable to those of SrCo$_2$V$_2$O$_8$ and BaCo$_2$V$_2$O$_8$. One interesting departure from the results of these related compounds, is however, the discovery of a new field-induced phase for the field direction $H\|$[110] which has not been previously observed

Magnetization Measurements on LHC Superconducting Strands

When using superconducting magnets in particle accelerators like the LHC, persistent currents in the superconductor often determine the field quality at injection, where the magnetic field is low. This paper describes magnetization measurements made on LHC cable strands at the Technical University of Vienna and the Institute of Physics of the Polish Academy of Sciences in collaboration with CERN. Measurements were performed at T=2K and T=4.2K on more than 50 strands of 7 different manufacturers with NbTi filament diameter between 5 and 7 micrometer. Two different measurement set-ups were used: vibrating sample magnetometer, with a sample length of about 8mm, and an integrating coil magnetometer, with sample length of about 1m. The two methods were compared by measuring the same sample. Low field evidence of proximity effect is discussed. Statistics like ratio of the width of the magnetization loop at 4.2K and 2K, and the initial slope dM/dB after cooldown are presented. Decrease of the magnetization with time, of the order of 2% per hour, was observed in some samples

{Rearrangement of the antiferromagnetic ordering at high magnetic fields in SmFeAsO and SmFeAsO0.9_{0.9}F0.1_{0.1} single crystals

The low-temperature antiferromagnetic state of the Sm-ions in both nonsuperconducting SmFeAsO and superconducting SmFeAsO$_{0.9}$F$_{0.1}$ single crystals was studied by magnetic torque, magnetization, and magnetoresistance measurements in magnetic fields up to 60~T and temperatures down to 0.6~K. We uncover in both compounds a distinct rearrangement of the antiferromagnetically ordered Sm-moments near $35-40$~T. This is seen in both, static and pulsed magnetic fields, as a sharp change in the sign of the magnetic torque, which is sensitive to the magnetic anisotropy and hence to the magnetic moment in the $ab$-plane, ({\it i.e.} the FeAs-layers), and as a jump in the magnetization for magnetic fields perpendicular to the conducting planes. This rearrangement of magnetic ordering in $35-40$~T is essentially temperature independent and points towards a canted or a partially polarized magnetic state in high magnetic fields. However, the observed value for the saturation moment above this rearrangement, suggests that the complete suppression of the antiferromagnetism related to the Sm-moments would require fields in excess of 60~T. Such a large field value is particularly remarkable when compared to the relatively small N\'{e}el temperature $T_{\rm N}\simeq5$~K, suggesting very anisotropic magnetic exchange couplings. At the transition, magnetoresistivity measurements show a crossover from positive to negative field-dependence, indicating that the charge carriers in the FeAs planes are sensitive to the magnetic configuration of the rare-earth elements. This is indicates a finite magnetic/electronic coupling between the SmO and the FeAs layers which are likely to mediate the exchange interactions leading to the long range antiferromagnetic order of the Sm ions.Comment: 10 pages, 7 figures, accepted in Phys. Rev.

The Comparative Effectiveness of Ceftolozane/Tazobactam versus Aminoglycoside- or Polymyxin-Based Regimens in Multi-Drug-Resistant Pseudomonas aeruginosa Infections

Pseudomonas aeruginosa infections are challenging to treat due to multi-drug resistance (MDR) and the complexity of the patients affected by these serious infections. As new antibiotic therapies come on the market, limited data exist about the effectiveness of such treatments in clinical practice. In this comparative effectiveness study of ceftolozane/tazobactam versus aminoglycoside- or polymyxin-based therapies among hospitalized patients with positive MDR P. aeruginosa cultures, we identified 57 patients treated with ceftolozane/tazobactam compared with 155 patients treated with aminoglycoside- or polymyxin-based regimens. Patients treated with ceftolozane/tazobactam were younger (mean age 67.5 vs. 71.1, p = 0.03) and had a higher comorbidity burden prior to hospitalization (median Charlson 5 vs. 3, p = 0.01) as well as higher rates of spinal cord injury (38.6% vs. 21.9%, p = 0.02) and P. aeruginosa-positive bone/joint cultures (12.3% vs. 0.7%, p \u3c 0.0001). Inpatient mortality was significantly lower in the ceftolozane/tazobactam group compared with aminoglycosides or polymyxins (15.8% vs. 27.7%, adjusted odds ratio 0.39, 95% confidence interval 0.16–0.93). There were no significant differences observed for the other outcomes assessed. In hospitalized patients with MDR P. aeruginosa, inpatient mortality was 61% lower among patients treated with ceftolozane/tazobactam compared to those treated with aminoglycoside- or polymyxin-based regimens

Single crystal of superconducting SmFeAsO1-xFy grown at high pressure

Single crystals of SmFeAsO1-xFy of a size up to 120 micrometers have been grown from NaCl/KCl flux at a pressure of 30 kbar and temperature of 1350-1450 C using the cubic anvil high-pressure technique. The superconducting transition temperature of the obtained single crystals varies between 45 and 53 K.Obtained crystals are characterized by a full diamagnetic response in low magnetic fields and by a high critical current density in high magnetic fields. Structural refinement has been performed on single crystal. Differential thermal analysis investigations at 1 bar Ar pressure show decomposition of SmFeAsO1-xFy at 1302 C.Comment: 12 pages, 3 tables, 6 figure

High magnetic field scales and critical currents in SmFeAs(O,F) crystals: promising for applications

Superconducting technology provides most sensitive field detectors, promising implementations of qubits and high field magnets for medical imaging and for most powerful particle accelerators. Thus, with the discovery of new superconducting materials, such as the iron pnictides, exploring their potential for applications is one of the foremost tasks. Even if the critical temperature Tc is high, intrinsic electronic properties might render applications rather difficult, particularly if extreme electronic anisotropy prevents effective pinning of vortices and thus severely limits the critical current density, a problem well known for cuprates. While many questions concerning microscopic electronic properties of the iron pnictides have been successfully addressed and estimates point to a very high upper critical field, their application potential is less clarified. Thus we focus here on the critical currents, their anisotropy and the onset of electrical dissipation in high magnetic fields up to 65 T. Our detailed study of the transport properties of optimally doped SmFeAs(O,F) single crystals reveals a promising combination of high (>2 x 10^6 A/cm^2) and nearly isotropic critical current densities along all crystal directions. This favorable intragrain current transport in SmFeAs(O,F), which shows the highest Tc of 54 K at ambient pressure, is a crucial requirement for possible applications. Essential in these experiments are 4-probe measurements on Focused Ion Beam (FIB) cut single crystals with sub-\mu\m^2 cross-section, with current along and perpendicular to the crystallographic c-axis and very good signal-to-noise ratio (SNR) in pulsed magnetic fields. The pinning forces have been characterized by scaling the magnetically measured "peak effect"

Características clínicas, microbiología y resultados de una cohorte de pacientes tratados con ceftolozane/tazobactam en centros de hospitalización de cuidados agudos, Houston, Texas, EE.UU

Antecedentes Ceftolozane/tazobactam es una combinación de β-lactámico/β-inhibidor de lactamasa con actividad contra una variedad de bacterias Gram-negativas, incluyendo Pseudomonas aeruginosa MDR. Este agente está aprobado para la neumonía bacteriana adquirida en el hospital y asociada a la ventilación mecánica. Sin embargo, la mayoría de los datos de resultados en el mundo real proceden de pequeñas cohortes observacionales. Por lo tanto, se trató de evaluar la utilización de ceftolozane/tazobactam en múltiples hospitales terciarios en Houston, TX, EE.UU.. Métodos Realizamos un estudio retrospectivo multicéntrico de pacientes que recibieron al menos 48 h de terapia con ceftolozano/tazobactam desde enero de 2016 hasta septiembre de 2019 en dos sistemas hospitalarios en Houston. Se recopilaron datos demográficos, clínicos y microbiológicos, incluido el aislado bacteriano infectante, cuando estaba disponible. El resultado primario fue el éxito clínico compuesto al alta hospitalaria. Los resultados secundarios incluyeron la mortalidad intrahospitalaria y la disposición clínica a los 14 y 30 días después del inicio de ceftolozane/tazobactam. Se utilizó un análisis de regresión logística multivariable para identificar los factores predictivos del resultado primario y la mortalidad. Los aislados recuperados se sometieron a pruebas de sensibilidad a ceftolozano/tazobactam y a WGS. Resultados Se incluyó a un total de 263 pacientes, y se alcanzó el éxito clínico compuesto en 185 pacientes (70,3%). La gravedad de la enfermedad fue el factor predictivo más consistente del éxito clínico. El tratamiento combinado con ceftolozane/tazobactam y otro agente Gram negativo activo se asoció a una reducción de las probabilidades de éxito clínico (OR 0,32; IC del 95%: 0,16-0,63). Se observó resistencia a ceftolozano/tazobactam en el 15,4% de los aislados disponibles para WGS; las mutaciones en ampC y ftsI fueron frecuentes pero no se agruparon con una ST concreta. Conclusiones La tasa de éxito clínico entre esta cohorte de pacientes tratados con ceftolozane/tazobactam fue similar en comparación con experiencias anteriores. Ceftolozane/tazobactam sigue siendo un agente alternativo para el tratamiento de aislados susceptibles de P. aeruginosaBackground Ceftolozane/tazobactam is a β-lactam/β-lactamase inhibitor combination with activity against a variety of Gram-negative bacteria, including MDR Pseudomonas aeruginosa. This agent is approved for hospital-acquired and ventilator-associated bacterial pneumonia. However, most real-world outcome data come from small observational cohorts. Thus, we sought to evaluate the utilization of ceftolozane/tazobactam at multiple tertiary hospitals in Houston, TX, USA. Methods We conducted a multicentre retrospective study of patients receiving at least 48 h of ceftolozane/tazobactam therapy from January 2016 through to September 2019 at two hospital systems in Houston. Demographic, clinical and microbiological data were collected, including the infecting bacterial isolate, when available. The primary outcome was composite clinical success at hospital discharge. Secondary outcomes included in-hospital mortality and clinical disposition at 14 and 30 days post ceftolozane/tazobactam initiation. Multivariable logistic regression analysis was used to identify predictors of the primary outcome and mortality. Recovered isolates were tested for susceptibility to ceftolozane/tazobactam and underwent WGS. Results A total of 263 patients were enrolled, and composite clinical success was achieved in 185 patients (70.3%). Severity of illness was the most consistent predictor of clinical success. Combination therapy with ceftolozane/tazobactam and another Gram-negative-active agent was associated with reduced odds of clinical success (OR 0.32, 95% CI 0.16–0.63). Resistance to ceftolozane/tazobactam was noted in 15.4% of isolates available for WGS; mutations in ampC and ftsI were common but did not cluster with a particular ST. Conclusions Clinical success rate among this patient cohort treated with ceftolozane/tazobactam was similar compared with previous experiences. Ceftolozane/tazobactam remains an alternative agent for treatment of susceptible isolates of P. aeruginosa