Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study

Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe

Formation de biofilms par Escherichia coli K-12 (rôle des systèmes à deux composants dans la synthèse des curli)

Dans les écosystèmes naturels, les bactéries vivent généralement au sein de communautés bactériennes adhérentes aux surfaces appelés biofilms. Afin de lutter efficacement contre la colonisation des surfaces, il est nécessaire d'identifier les mécanismes bactériens impliqués dans la formation de biofilms. Ce travail a eu pour objectifs l'identification et la hiérarchisation des mécanismes de régulation contrôlant la synthèse d'une structure d'adhérence, les curli, en fonction de l'osmolarité du milieu environnant et de l'intégrité membranaire des bactéries. Nous avons découvert que les systèmes à deux composants EnvZ/OmpR, CpxA/CpxR et RcsC/RcsB jouent un rôle clef dans le contrôle transcriptionnel des gènes de curli via des équilibres complexes entre activateurs et répresseurs. L'analyse de l'expression spatio-temporelle des gènes de curli au sein du biofilm a également permis de démontrer le rôle capital des curli dans les différentes étapes du processus de développement d'un biofilm.In natural ecosystems, bacteria have a remarkable tendency to adhere to surfaces within microbial consortia called biofilms. In order to prevent colonization of surfaces, it is necessary to know bacterial mechanisms involved in biofilm formation. The aims of this work were to identify and to classify regulatory mechanisms that control synthesis of curli, a structure of attachment, according to medium osmolarity and integrity of bacterial membrane. We discovered that the two-component systems EnvZ/OmpR, CpxA/CpxR and RcsC/RcsB play a fundamental role in the transcriptional control of curli genes with complexes balances between activators and repressors. Analysis of the expression, both in time and space, of the curli genes in biofilm also shows that curli are essential in each different stage of biofilm development process.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF

Rôle d'Escherichia coli curli en relation avec les composantes intestinales - mucine, Klebsiella pneumoniae et Enterococcus faecalis

Les bactéries dans la nature existent principalement en biofilm, qui est une communauté structurée et adhérente de microbes enveloppés dans des matrices polymériques. Dans le corps humain, la plupart de biofilms sont composés de microorganismes commensaux et le tractus gastro-intestinal est le site le plus fortement colonisé. L attachement bactérien à la couche de gel de mucus couvrant l épithélium intestinal est fondamental à l établissement d une microflore commensale stable. Cependant, les interactions entre les bactéries et le gel de mucus restent mal décrites. En plus, la complexité et la diversité du microbiote intestinal lui-même est un obstacle pour les analyses de son fonctionnement biologique. Les fonctions du microbiote sont le produit de communautés bactériennes complexes, et des interactions entres les différentes espèces qui les composent. De nouvelles approches sont nécessaires pour étudier la génétique de l espèce la plus étudiée du microbiote de l intestin humain, Escherichia coli. Cette thèse est consacrée à l exploration de la réponse transcriptionnelle d E. coli à différents facteurs présents dans l intestin humain à travers la réalisation de 3 objectifs principaux. La première partie de mon travail concerne la conception et l optimisation d outils génétiques permettant de détecter E. coli au sein de biofilms multi-espèces tout en mesurant simultanément l activité d un gène d intérêt. L utilisation du gène codant la protéine fluorescente verte (GFP) et de ses dérivés a permis d importantes avancées sur le marquage des cellules entières ainsi que le suivi d activité transcriptionnelle. Par contre, l utilisation de marqueurs fluorescents rouges s est révélée décevante. Dans un deuxième temps, grâce aux outils mis au point dans la première partie de mon travail, l influence de la mucine sur la capacité d E. coli à former des biofilm a pu être étudiée. J ai montré que la mucine augmente la formation du biofilm d E. coli par modulation transcriptionnelle de structures d adhérences telles que les curli et les pili de type 1. Enfin, l influence de la culture en biofilms multi-espèces constitués d E. coli et de bactéries commensales (K. pneumoniae and E. faecalis) sur la croissance de chacun des partenaires a été analysée, en focalisant notre attention sur l influence possible de structures d adhérence telles que les curli. Les résultats indiquent que la production de curli en biofilm augmente le développement d E. coli en co-culture avec K. pneumoniae alors qu elle favorise l interaction synergique entre E. coli et E. faecalis. Les implications basées sur ces données ont été examinées. Ce travail contribue à l amélioration des connaissances sur la réponse d E. coli à l environnement intestinal et apporte les fondations pour construire des outils plus puissants pour la poursuite des investigations sur les biofilms multi-espèces.Bacteria in nature mostly exist in biofilms, which are structured adherent communities encased in polymeric matrices. In the human body, most biofilms are composed of commensal microorganisms with the gastrointestinal tract being the most heavily colonized site. Bacterial attachment to the overlying mucus gel layer of the intestinal epithelium is fundamental to the establishment of a stable commensal microflora. However the interaction of bacteria with the complex mucus gel is poorly described. Moreover, the complexity and diversity of the gut microbiota is itself an obstacle to studying its biology. Microbiota functions are the product of communities of bacteria and interactions between multiple species. New approaches are needed to study this aspect of even the most well-studied member of the human gut microbiota, Escherichia coli. This thesis was devoted to the exploration of the transcriptional response of E. coli facing different elements of human gut following 3 main objectives. First, the initial part of my work was related to the conception and optimization of appropriate genetic tools to both track E. coli within the multispecies context that constitute human gut commensals, and survey the expression of genes of interest. Use of the Green Fluorescent Protein (GFP) genes allowing enhanced fluorescence and shortened half-life has permitted significant progress both in whole cell tagging as well as transcriptional reporting, while the red fluorescent counterparts were disappointing. Second, using the subset of tools that has been validated to be reliable, influence of mucin on the biofilm formation ability of E. coli has subsequently been studied. I have shown that mucin promotes E. coli biofilm formation through transcriptional modulation of surface adhesion structures such as curli and type 1 pili. Third, concurrently, E. coli s population relationship to commensal bacteria (K. pneumoniae and E. faecalis) was investigated and demonstrated, with the possible influence of surface adhesion structures such as curli as the biological focus. The results suggest that curli production in biofilm increases the fitness of E. coli when co-cultured with K. pneumoniae while promoting synergistic interaction between E. coli and E. faecalis. The implication based on the data is discussed. This work improves the understanding of E. coli response to the gut environment, and provides foundations to build more powerful tools for further investigations.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocVILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF

iGEM Europe 2013: Des gènes et des machines

International audienc

Gene Expression Regulation by the Curli Activator CsgD Protein: Modulation of Cellulose Biosynthesis and Control of Negative Determinants for Microbial Adhesion

Curli fibers, encoded by the csgBAC genes, promote biofilm formation in Escherichia coli and other enterobacteria. Curli production is dependent on the CsgD transcription activator, which also promotes cellulose biosynthesis. In this study, we investigated the effects of CsgD expression from a weak constitutive promoter in the biofilm formation-deficient PHL565 strain of E. coli. We found that despite its function as a transcription activator, the CsgD protein is localized in the cytoplasmic membrane. Constitutive CsgD expression promotes biofilm formation by PHL565 and activates transcription from the csgBAC promoter; however, csgBAC expression remains dependent on temperature and the growth medium. Constitutive expression of the CsgD protein results in altered transcription patterns for at least 24 novel genes, in addition to the previously identified CsgD-dependent genes. The cspA and fecR genes, encoding regulatory proteins responding to cold shock and to iron, respectively, and yoaD, encoding a putative negative regulator of cellulose biosynthesis, were found to be some of the novel CsgD-regulated genes. Consistent with the predicted functional role, increased expression of the yoaD gene negatively affects cell aggregation, while yoaD inactivation results in stimulation of cell aggregation and leads to increased cellulose production. Inactivation of fecR results in significant increases in both cell aggregation and biofilm formation, while the effects of cspA are not as strong in the conditions tested. Our results indicate that CsgD can modulate cellulose biosynthesis through activation of the yoaD gene. In addition, the positive effect of CsgD on biofilm formation might be enhanced by repression of the fecR gene