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Three nanocomposite materials with the same nominal stoichiometric thermite composition of 2Al-3CuO were prepared by three different methods: ultrasonic mixing (USM) of constituent nanopowders, electrospraying (ES), and arrested reactive milling (ARM). Prepared powders were placed in a 6.7-mm diameter, 0.5-mm-deep cavity in a brass substrate and ignited by electro-static discharge. The experiments were performed in air, argon, and helium. The mass of powder removed from the sample holder after ignition was measured in each test. Using a multi-anode photo-multiplier tube coupled with a spectrometer, time-resolved light emission traces produced by the ignited samples were recorded in the range of wavelengths of 373–641 nm. Time-resolved temperatures were then determined by fitting the recorded spectra assuming Planck’s black body emission. Temporal pressure generated by ignition events in the enclosed chamber showed that the powder’s combustion properties were tied to both their preparation technique as well as the environment they were ignited in. We found that agglomeration of nanoparticles hindered combustion of USM powders; while it was not observed for the ES powders. In oxygen-free gas environments, lower temperatures and pressures were observed for USM and ES powders prepared using starting nano-particles. For the ES powders, the effect of gas environment was less significant, which was interpreted considering that ES materials included gasifying nitrocellulose binder, enhancing heat, and mass transfer between individual Al and CuO particles. Higher pressures and temperatures were observed in inert environments for the ARM-prepared powder. [ABSTRACT FROM AUTHOR]

Nanocomposite powders with aluminum as a fuel and oxides of molybdenum, copper, bismuth, and iron as oxidizers were prepared by arrested reactive milling. The powders were placed in 0.5-mm-thick layers and ignited by electrostatic discharge (ESD) in air. In different tests, time-resolved light emission was recorded at 568 nm or in the range of 373–641 nm. The amount of material consumed was recorded as well. Time-resolved temperatures were determined. Two distinct ignition regimes were observed. Prompt ignition occurred within 10 µs of the electric discharge, comparable to what had previously been observed for corresponding powder monolayers. This ignition mode was observed for composites with Bi2O3and Fe2O3ignited with a 12-kV discharge, whereas it only occurred at higher spark voltage (20 kV) and energy for CuO and MoO3composites. Delayed ignition, occurring after 0.1–1 ms following the discharge, was observed for all composites with consistently stronger light emission. Analysis of quenched, partially burned particles showed that the original nanostructure was preserved after prompt ignition but not after delayed ignition. It is proposed that prompt ignition represents direct ESD initiation of composite particles rapidly and adiabatically preheated to high temperatures while keeping the nanostructure intact, resulting in a heterogeneous reaction consuming most of the aluminum. Delayed ignition occurs when particles preheated to lower temperatures start oxidizing at much lower rates, leading to cloud combustion, in which thermal interaction between individual aerosolized burning particles is substantial. During this process, the nanostructure may be lost. Temperature measurements show that nanocomposites with CuO and MoO3burned superadiabatically with flame temperatures exceeding thermodynamic predictions. [ABSTRACT FROM PUBLISHER]

Even in the setting of optimal resuscitation in high-income countries severe sepsis and septic shock have a mortality of 20-40%, with antibiotic resistance dramatically increasing this mortality risk. To develop a reference dataset enabling the identification of common bacterial targets for therapeutic intervention, we applied a standardized genomic, transcriptomic, proteomic and metabolomic technological framework to multiple clinical isolates of four sepsis-causing pathogens: Escherichia coli, Klebsiella pneumoniae species complex, Staphylococcus aureus and Streptococcus pyogenes. Exposure to human serum generated a sepsis molecular signature containing global increases in fatty acid and lipid biosynthesis and metabolism, consistent with cell envelope remodelling and nutrient adaptation for osmoprotection. In addition, acquisition of cholesterol was identified across the bacterial species. This detailed reference dataset has been established as an open resource to support discovery and translational research., (© 2023. The Author(s).)

Bacterial histidine kinases are promising targets for new antimicrobial agents. In antibacterial therapy, such agents could inhibit bacterial growth by targeting essential two-component regulatory systems or resensitize bacteria to known antibiotics by blocking stress responses upon cell wall or cell membrane damage. However, (i) activity assays using truncated kinase proteins, that is, the cytoplasmic domains containing the conserved histidine residue for phosphorylation, have been shown to produce artifacts, and (ii) the purification of the full-length histidine kinases is complicated. Here, we describe a standard protocol for the recombinant expression and purification of functional full-length histidine kinases and other membrane proteins from Gram-positive bacteria that do not harbor more than two trans-membrane domains in an Escherichia coli host. This guide also presents in vitro and in vivo phosphorylation assays to screen for new antimicrobial compounds that target bacterial histidine kinases, either using a traditional radioactively labeled ATP assay to quantify histidine kinase phosphorylation or Phos-tag acrylamide gel electrophoresis to examine histidine kinase phosphorylation through mobility shift in the polyacrylamide gel. In addition, we describe the use of Phos-tag combined with a western blot approach to visualize the phosphorylation of a response regulator in vivo., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Mutation acquisition is a major mechanism of bacterial antibiotic resistance that remains insufficiently characterised. Here we present RM-seq, a new amplicon-based deep sequencing workflow based on a molecular barcoding technique adapted from Low Error Amplicon sequencing (LEA-seq). RM-seq allows detection and functional assessment of mutational resistance at high throughput from mixed bacterial populations. The sensitive detection of very low-frequency resistant sub-populations permits characterisation of antibiotic-linked mutational repertoires in vitro and detection of rare resistant populations during infections. Accurate quantification of resistance mutations enables phenotypic screening of mutations conferring pleiotropic phenotypes such as in vivo persistence, collateral sensitivity or cross-resistance. RM-seq will facilitate comprehensive detection, characterisation and surveillance of resistant bacterial populations ( https://github.com/rguerillot/RM-seq ).

Mutations in the beta-subunit of bacterial RNA polymerase (RpoB) cause resistance to rifampin (Rif r ), a critical antibiotic for treatment of multidrug-resistant Staphylococcus aureus . In vitro studies have shown that RpoB mutations confer decreased susceptibility to other antibiotics, but the clinical relevance is unknown. Here, by analyzing 7,099 S. aureus genomes, we demonstrate that the most prevalent RpoB mutations promote clinically relevant phenotypic plasticity resulting in the emergence of stable S. aureus lineages, associated with increased risk of therapeutic failure through generation of small-colony variants (SCVs) and coresistance to last-line antimicrobial agents. We found eight RpoB mutations that accounted for 93% (469/505) of the total number of Rif r mutations. The most frequently selected amino acid substitutions affecting residue 481 (H481N/Y) were associated with worldwide expansions of Rif r clones spanning decades. Recreating the H481N/Y mutations confirmed no impact on S. aureus growth, but the H481N mutation promoted the emergence of a subpopulation of stable Rif r SCVs with reduced susceptibility to vancomycin and daptomycin. Recreating the other frequent RpoB mutations showed similar impacts on resistance to these last-line agents. We found that 86% of all Rif r isolates in our global sample carried the mutations promoting cross-resistance to vancomycin and 52% to both vancomycin and daptomycin. As four of the most frequent RpoB mutations confer only low-level Rif r , equal to or below some international breakpoints, we recommend decreasing these breakpoints and reconsidering the appropriate use of rifampin to reduce the fixation and spread of these clinically deleterious mutations. IMPORTANCE Increasing antibiotic resistance in the major human pathogen Staphylococcus aureus is threatening the ability to treat patients with these infections. Recent laboratory studies suggest that mutations in the gene commonly associated with rifampin resistance may also impact susceptibility to other last-line antibiotics in S. aureus ; however, the overall frequency and clinical impact of these mutations are unknown. By mining a global collection of clinical S. aureus genomes and by mutagenesis experiments, this work reveals that common rifampin-induced rpoB mutations promote phenotypic plasticity that has led to the global emergence of stable, multidrug-resistant S. aureus lineages that are associated with increased risk of therapeutic failure through coresistance to other last-line antimicrobials. We recommend decreasing susceptibility breakpoints for rifampin to allow phenotypic detection of critical rpoB mutations conferring low resistance to rifampin and reconsidering the appropriate use of rifampin to reduce the fixation and spread of these deleterious mutations globally.

Objectives: Vancomycin-intermediate Staphylococcus aureus (VISA) is associated with genetic changes that may also impact upon pathogenicity. In the current study, we compared the virulence of clinical VISA strains with their isogenic vancomycin-susceptible progenitors (VSSA)., Methods: Production of the critical virulence protein, α toxin, was assessed using Western blot analysis and was correlated to agr activity using a bioluminescent agr-reporter. Cytotoxicity and intracellular persistence were compared ex vivo for VSSA and VISA within non-professional phagocytes (NPP). Virulence and host immune responses were further explored in vivo using a murine model of bacteraemia., Results: VISA isolates produced up to 20-fold less α toxin compared with VSSA, and this was corroborated by either loss of agr activity due to agr mutation, or altered agr activity in the absence of mutation. VISA were less cytotoxic towards NPP and were associated with enhanced intracellular persistence, suggesting that NPP may act as a reservoir for VISA. Infection with VSSA strains produced higher mortality in a murine bacteraemia model (≥90% 7-day mortality) compared with infection with VISA isolates (20% to 50%, p <0.001). Mice infected with VISA produced a dampened immune response (4.6-fold reduction in interleukin-6, p <0.001) and persistent organ bacterial growth was observed for VISA strains out to 7 days., Conclusions: These findings highlight the remarkable adaptability of S. aureus, whereby, in addition to having reduced antibiotic susceptibility, VISA alter the expression of pathogenic factors to circumvent the host immune response to favour persistent infection over acute virulence., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective Although thyroglossal duct cysts (TGDCs) are relatively common, malignancies within these lesions are infrequent. As a result, there are no large-scale series describing clinical characteristics. Our objectives were to perform a systematic review of the literature evaluating patient demographics, pathology, management, and prognosis of these patients. Data Sources PubMed, Embase, Cochrane reviews, and Google Scholar were searched for relevant articles. Articles meeting inclusion criteria were reviewed for data detailing epidemiology, treatment, and outcomes. Review Methods Inclusion criteria included English-language articles with original reports on human subjects. Two investigators independently reviewed all articles for the data collected, including epidemiology, treatment, and outcomes. Results Ninety-eight articles comprising 164 patients were included in the final analysis. The mean age at presentation was 39.5 years (9-83 years); 68.3% of patients were female. In total, 73.3% of cases were found on final pathologic analysis. The most common pathology was papillary cancer (92.1%). Of the patients, 98.9% underwent a Sistrunk procedure and 61.0% underwent total thyroidectomy. There was a 4.3% recurrence rate with a mean time to recurrence of 42.1 months from initial treatment. One patient died of TGDC carcinoma, while all other patients were disease free at the time of last follow-up (mean follow-up was 46.1 months). Conclusion TGDC carcinoma is typically diagnosed on final pathology. While management encompasses a Sistrunk procedure, further consideration should be given to thyroidectomy among patients ≥45 years of age and individuals with aggressive disease. TGDC carcinoma harbors an exceedingly low rate of mortality.