Portable Differential Detection of CTX-M ESBL Gene Variants, blaCTX-M-1 and blaCTX-M-15, from Escherichia coli Isolates and Animal Fecal Samples Using Loop-Primer Endonuclease Cleavage Loop-Mediated Isothermal Amplification

Cefotaximase-Munich (CTX-M) extended-spectrum beta-lactamase (ESBL) enzymes produced by Enterobacteriaceae confer resistance to clinically relevant third-generation cephalosporins. CTX-M group 1 variants, CTX-M-1 and CTX-M-15, are the leading ESBL-producing Enterobacteriaceae associated with animal and human infection, respectively, and are an increasing antimicrobial resistance (AMR) global health concern. The blaCTX-M-1 and blaCTX-M-15 genes encoding these variants have an approximate nucleotide sequence similarity of 98.7%, making effective differential diagnostic monitoring difficult. Loop-primer endonuclease cleavage loop-mediated isothermal amplification (LEC-LAMP) enables rapid real-time multiplex pathogen detection with single-base specificity and portable on-site testing. We have developed an internally controlled multiplex CTX-M-1/15 LEC-LAMP assay for the differential detection of blaCTX-M-1 and blaCTX-M-15. Assay analytical specificity was established using a panel of human, animal, and environmental Escherichia coli isolates positive for blaCTX-M-1 (n = 18), blaCTX-M-15 (n = 35), and other closely related blaCTX-Ms (n = 38) from Ireland, Germany, and Portugal, with analytical sensitivity determined using probit regression analysis. Animal fecal sample testing using the CTX-M-1/15 LEC-LAMP assay in combination with a rapid DNA extraction protocol was carried out on porcine fecal samples previously confirmed to be PCR-positive for E. coli blaCTX-M. Portable instrumentation was used to further analyze each fecal sample and demonstrate the on-site testing capabilities of the LEC-LAMP assay with the rapid DNA extraction protocol. The CTX-M-1/15 LEC-LAMP assay demonstrated complete analytical specificity for the differential detection of both variants with sensitive low-level detection of 8.5 and 9.8 copies per reaction for blaCTX-M-1 and blaCTX-M-15, respectively, and E. coli blaCTX-M-1 was identified in all blaCTX-M positive porcine fecal samples tested.This research was funded by the European Union Horizon 2020 Research and Innovation Program under grant agreement No. 773830: One Health European Joint Program, JRP13-AMRSH5-WORLDCOM project.info:eu-repo/semantics/publishedVersio

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Development of a Chemical Kinetic Mechanism for Small Hydrocarbons

A detailed chemical kinetic mechanism has been developed to describe the oxidation of small hydrocarbon and oxygenated hydrocarbon species. In order to understand the oxidation of large hydrocarbon and oxygenated hydrocarbon fuels it is necessary to first generate a detailed understanding of the pyrolysis and oxidation kinetics of simple fuels such as hydrogen and carbon monoxide as well as hydrocarbon fuels such as methane, ethane, ethylene, acetylene, propane, propene, allene, and propyne. Contributions were made to the development a detailed chemical kinetic C1-C2 mechanism. The largest part of the contribution to the C1-C2 sub-mechanism made by the author of this study was in the development of the methanol, acetaldehyde, and ethanol sub-mechanisms. Rate constants and thermochemical data were included in the mechanism from the most recent experimental and theoretical studies where available and optimisation was avoided as much as possible. An updated method for estimating thermochemical group values for higher order hydrocarbons was developed in a hierarchal and iterative manner. A large database of thermochemical data available from the literature for C1-C4 alkane, alkene, alcohols, hydroperoxides and alcoholic hydroperoxides species was collated. Updates were made to the allene and propyne sub-mechanism, incorporated into the mechanism are recent high-level rate constant calculations. The allene and propyne sub-mechanism is validated against the available experimental data. New experimental data for propene oxidation was obtained in a jet-stirred reactor. This data contributed to the development of a new sub-mechanism for propene oxidation that is capable of predicting combustion characteristics for propene across a wide range of conditions (T, p, phi, dilution)

Development of a Chemical Kinetic Mechanism for Small Hydrocarbons

A detailed chemical kinetic mechanism has been developed to describe the oxidation of small hydrocarbon and oxygenated hydrocarbon species. In order to understand the oxidation of large hydrocarbon and oxygenated hydrocarbon fuels it is necessary to first generate a detailed understanding of the pyrolysis and oxidation kinetics of simple fuels such as hydrogen and carbon monoxide as well as hydrocarbon fuels such as methane, ethane, ethylene, acetylene, propane, propene, allene, and propyne. Contributions were made to the development a detailed chemical kinetic C1-C2 mechanism. The largest part of the contribution to the C1-C2 sub-mechanism made by the author of this study was in the development of the methanol, acetaldehyde, and ethanol sub-mechanisms. Rate constants and thermochemical data were included in the mechanism from the most recent experimental and theoretical studies where available and optimisation was avoided as much as possible. An updated method for estimating thermochemical group values for higher order hydrocarbons was developed in a hierarchal and iterative manner. A large database of thermochemical data available from the literature for C1-C4 alkane, alkene, alcohols, hydroperoxides and alcoholic hydroperoxides species was collated. Updates were made to the allene and propyne sub-mechanism, incorporated into the mechanism are recent high-level rate constant calculations. The allene and propyne sub-mechanism is validated against the available experimental data. New experimental data for propene oxidation was obtained in a jet-stirred reactor. This data contributed to the development of a new sub-mechanism for propene oxidation that is capable of predicting combustion characteristics for propene across a wide range of conditions (T, p, phi, dilution)

Autoignition of ethanol in a rapid compression machine

Ethanol is a renewable source of energy and significant attention has been directed to the development of a validated chemical kinetic mechanism for this fuel. The experimental data for the autoignition of ethanol in the low temperature range at elevated pressures are meager. In order to provide experimental data sets for mechanism validation at such conditions, the autoignition of homogeneous ethanol/oxidizer mixtures has been investigated in a rapid compression machine. Experiments cover a range of pressures (10-50 bar), temperatures (825-985 K) and equivalence ratios of 0.3-1.0. Ignition delay data are deduced from the experimental pressure traces. Under current experimental conditions of elevated pressures and low temperatures, chemistry pertaining to hydroperoxyl radicals assumes importance. A chemical kinetic mechanism that can accurately predict the autoignition characteristics of ethanol at low temperatures and elevated pressures has been developed and this mechanism is compared with other models available in the literature. (C) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved

Oxidation of ethylene-air mixtures at elevated pressures, part 2: chemical kinetics

Journal articleA chemical kinetics submechanism for small molecular weight hydrocarbons was modified by adjusting rate constants to produce better agreement with recent ethylene ignition delay time data compared with an earlier version of the mechanism, for temperatures from 1003 to 1401 K, at pressures between 1.1 and 24.9 atm, and for equivalence ratios from 0.3 to 2.0. The improved mechanism captures the pressure and equivalence ratio behavior seen in the data at these intermediate temperatures, such as the smaller-than-expected effect of equivalence ratio at the higher temperatures and an apparent lack of pressure dependence at fuel-lean conditions. By using detailed sensitivity analyses, the important reactions were identified, rectifying the model simulations in predicting the observed experimental behavior of the data in this study. In fact, when the model is used to extend the temperature range above 1400 K and below 1000 K, the same pressure dependence is actually seen for all equivalence ratios, just to a lesser extent at the test temperatures. Hence, the resulting hydrocarbon mechanism is much more robust as a result of this exercise. The initial deficiency and subsequent improvement of the model justify the new ignition delay time data from the companion paper to this study as well as the need for further study on ethylene kinetics.National Science Foundation, Grant Number CBET-0832561; Saudi Aramc

An experimental and modeling study of propene oxidation. Part 1: Speciation measurements in jet-stirred and flow reactors

Journal articlePropene is a significant component of Liquefied Petroleum Gas (LPG) and an intermediate in the combustion of higher order hydrocarbons. To better understand the combustion characteristics of propene, this study and its companion paper present new experimental data from jet-stirred (JSR) and flow reactors (Part I) and ignition delay time and flame speed experiments (Part II).Species profiles from JSR experiments are presented and were obtained at near-atmospheric pressure over a temperature range of 800-1100 K and for equivalence ratios from phi = 0.64 to 2.19. The new JSR data were obtained at lower dilution levels and temperatures than previously published. Also reported are species profiles from two high-pressure flow reactor facilities: the Princeton Variable Pressure Flow Reactor (VPFR) and the High Pressure Laminar Flow Reactor (HPLFR). The VPFR experiments were conducted at pressures of 6-12.5 atm, in the temperature range 843-1020 K and at equivalence ratios of 0.7-1.3. The HPLFR experiments were conducted at 15 atm, at a temperature of 800 K and at equivalence ratios of 0.35-1.25. The flow reactor data is at higher pressures and lower temperatures than existing data in the literature.A detailed chemical kinetic mechanism has been simultaneously developed to describe the combustion of propene under the experimental conditions described above. Important reactions highlighted via flux and sensitivity analyses include: hydrogen atom abstraction from propene by molecular oxygen, hydroxyl, and hydroperoxyl radicals; allyl-allyl radical recombination; the reaction between ally] and hydroperoxyl radicals; and the reactions of 1- and 2-propenyl radicals with molecular oxygen. The current mechanism accurately predicts the combustion characteristics of propene across the range of experimental conditions presented in this study, from jet-stirred and flow reactors and for ignition delay times and flame speed measurements presented in Part II. In comparison to a previous mechanism, AramcoMech 1.3, the current mechanism results in much improved performance, which highlights the importance of the new experimental data in constraining the important reactions. (c) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.Work at Princeton University was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, both as part of the Combustion Energy Frontier Research Center, an Energy Frontier Research Center funded under award number DE-SC0001198, as well as under award number DE-FG02-86ER13503 administered by the Chemical Sciences, Geosciences, and Biosciences Division

An experimental and modeling study of propene oxidation. Part 2: Ignition delay time and flame speed measurements

Journal articleExperimental data obtained in this study (Part II) complement the speciation data presented in Part I, but also offer a basis for extensive facility cross-comparisons for both experimental ignition delay time (IDT) and laminar flame speed (LFS) observables.To improve our understanding of the ignition characteristics of propene, a series of IDT experiments were performed in six different shock tubes and two rapid compression machines (RCMs) under conditions not previously studied. This work is the first of its kind to directly compare ignition in several different shock tubes over a wide range of conditions. For common nominal reaction conditions among these facilities, cross-comparison of shock tube IDTs suggests 20-30% reproducibility (2 sigma) for the IDT observable. The combination of shock tube and RCM data greatly expands the data available for validation of propene oxidation models to higher pressures (2-40 atm) and lower temperatures (750-1750 K).Propene flames were studied at pressures from 1 to 20 atm and unburned gas temperatures of 295-398 K for a range of equivalence ratios and dilutions in different facilities. The present propene-air LFS results at 1 atm were also compared to LFS measurements from the literature. With respect to initial reaction conditions, the present experimental LFS cross-comparison is not as comprehensive as the IDT comparison; however, it still suggests reproducibility limits for the LFS observable. For the LFS results, there was agreement between certain data sets and for certain equivalence ratios (mostly in the lean region), but the remaining discrepancies highlight the need to reduce uncertainties in laminar flame speed experiments amongst different groups and different methods. Moreover, this is the first study to investigate the burning rate characteristics of propene at elevated pressures (>5 atm).IDT and LFS measurements are compared to predictions of the chemical kinetic mechanism presented in Part I and good agreement is observed. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.The Rensselaer group was supported by the U.S. Air Force Office of Scientific Research (Grant No. FA9550-11-1-0261) with Dr. Chiping Li as technical monitor. Work at the University of Connecticut and at Princeton University was supported as part of the Combustion Energy Frontier Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, under Award Number DE-SC0001198. The work at Stanford University was supported by the Air Force Office of Scientific Research through AFOSR Grant No. FA9550-11-1-0217, under the AFRL Integrated Product Team, with Dr. Chiping Li as contract monitor. The work at NUI Galway was kindly supported by Saudi Aramco. The work of KAUST authors was supported by Saudi Aramco under the FUELCOM program.peer-reviewe