Influence of hydrological conditions on the Escherichia coli population structure in the water of a creek on a rural watershed.

International audienceBACKGROUND: Escherichia coli is a commensal bacterium of the gastro-intestinal tract of human and vertebrate animals, although the aquatic environment could be a secondary habitat. The aim of this study was to investigate the effect of hydrological conditions on the structure of the E. coli population in the water of a creek on a small rural watershed in France composed of pasture and with human occupation. RESULTS: It became apparent, after studying the distribution in the four main E. coli phylo-groups (A, B1, B2, D), the presence of the hly (hemolysin) gene and the antibiotic resistance pattern, that the E. coli population structure was modified not only by the hydrological conditions (dry versus wet periods, rainfall events), but also by how the watershed was used (presence or absence of cattle). Isolates of the B1 phylo-group devoid of hly and sensitive to antibiotics were particularly abundant during the dry period. During the wet period and the rainfall events, contamination from human sources was predominantly characterized by strains of the A phylo-group, whereas contamination by cattle mainly involved B1 phylo-group strains resistant to antibiotics and exhibiting hly. As E. coli B1 was the main phylo-group isolated in water, the diversity of 112 E. coli B1 isolates was further investigated by studying uidA alleles (beta-D-glucuronidase), the presence of hly, the O-type, and antibiotic resistance. Among the forty epidemiolgical types (ETs) identified, five E. coli B1 ETs were more abundant in slightly contaminated water. CONCLUSIONS: The structure of an E. coli population in water is not stable, but depends on the hydrological conditions and on current use of the land on the watershed. In our study it was the ratio of A to B1 phylo-groups that changed. However, a set of B1 phylo-group isolates seems to be persistent in water, strengthening the hypothesis that they may correspond to specifically adapted strains

Exposure to vancomycin causes a shift in the microbial community structure without affecting nitrate reduction rates in river sediments

International audienceAntibiotics and antibiotic resistance genes have shown to be omnipresent in the environment. In this study, we investigated the effect of vancomycin (VA) on denitrifying bacteria in river sediments of a Waste Water Treatment Plant, receiving both domestic and hospital waste. We exposed these sediments continuously in flow-through reactors to different VA concentrations under denitrifying conditions (nitrate addition and anoxia) in order to determine potential nitrate reduction rates and changes in sedimentary microbial community structures. The presence of VA had no effect on sedimentary nitrate reduction rates at environmental concentrations, whereas a change in bacterial (16S rDNA) and denitrifying (nosZ) community structures was observed (determined by polymerase chain reaction-denaturing gradient gel electrophoresis). The bacterial and denitrifying community structure within the sediment changed upon VA exposure indicating a selection of a non-susceptible VA population

European Journal of Mechanics - A/Solids

A method coupling experiments and simulations, is developed to characterize the yield stress and strain hardening of several metals loaded at 106 s−1 and < 25 ns, typically involved during Laser Shock Peening. It was applied to four materials: pure aluminum, 2024-T3 and 7175-T7351 aluminum alloys and Ti6Al4V-ELI titanium alloy. Thin foils have been irradiated with high-power laser to induce high-pressure shock wave. Plastic deformation is activated through the thickness up to the rear free-surface of the foils. These experiments have been simulated using three material constitutive equations: Elastic–Perfectly Plastic model considering static yield stress, Johnson–Cook model without strain hardening and Johnson–Cook model with strain hardening. The material parameters of Johnson–Cook law were identified by comparison of the experimental and calculated velocity profiles of the rear-free surface. Results are shown and discussed

Impact of species and antibiotic therapy of enterococcal peritonitis on 30-day mortality in critical care - An analysis of the OUTCOMEREA database

Introduction: Enterococcus species are associated with an increased morbidity in intraabdominal infections (IAI). However, their impact on mortality remains uncertain. Moreover, the influence on outcome of the appropriate or inappropriate status of initial antimicrobial therapy (IAT) is subjected to debate, except in septic shock. The aim of our study was to evaluate whether an IAT that did not cover Enterococcus spp. was associated with 30-day mortality in ICU patients presenting with IAI growing with Enterococcus spp. Material and methods: Retrospective analysis of French database OutcomeRea from 1997 to 2016. We included all patients with IAI with a peritoneal sample growing with Enterococcus. Primary endpoint was 30-day mortality. Results: Of the 1017 patients with IAI, 76 (8%) patients were included. Thirty-day mortality in patients with inadequate IAT against Enterococcus was higher (7/18 (39%) vs 10/58 (17%), p = 0.05); however, the incidence of postoperative complications was similar. Presence of Enterococcus spp. other than E. faecalis alone was associated with a significantly higher mortality, even greater when IAT was inadequate. Main risk factors for having an Enterococcus other than E. faecalis alone were as follows: SAPS score on day 0, ICU-acquired IAI, and antimicrobial therapy within 3 months prior to IAI especially with third-generation cephalosporins. Univariate analysis found a higher hazard ratio of death with an Enterococcus other than E. faecalis alone that had an inadequate IAT (HR = 4.4 [1.3-15.3], p = 0.019) versus an adequate IAT (HR = 3.1 [1.0-10.0], p = 0.053). However, after adjusting for confounders (i.e., SAPS II and septic shock at IAI diagnosis, ICU-acquired peritonitis, and adequacy of IAT for other germs), the impact of the adequacy of IAT was no longer significant in multivariate analysis. Septic shock at diagnosis and ICU-acquired IAI were prognostic factors. Conclusion: An IAT which does not cover Enterococcus is associated with an increased 30-day mortality in ICU patients presenting with an IAI growing with Enterococcus, especially when it is not an E. faecalis alone. It seems reasonable to use an IAT active against Enterococcus in severe postoperative ICU-acquired IAI, especially when a third-generation cephalosporin has been used within 3 months. © 2019 The Author(s)

Euclid Near Infrared Spectrometer and Photometer instrument concept and first test results obtained for different breadboards models at the end of phase C

The Euclid mission objective is to understand why the expansion of the Universe is accelerating through by mapping the geometry of the dark Universe by investigating the distance-redshift relationship and tracing the evolution of cosmic structures. The Euclid project is part of ESA's Cosmic Vision program with its launch planned for 2020 (ref [1]). The NISP (Near Infrared Spectrometer and Photometer) is one of the two Euclid instruments and is operating in the near-IR spectral region (900- 2000nm) as a photometer and spectrometer. The instrument is composed of: - a cold (135K) optomechanical subsystem consisting of a Silicon carbide structure, an optical assembly (corrector and camera lens), a filter wheel mechanism, a grism wheel mechanism, a calibration unit and a thermal control system - a detection subsystem based on a mosaic of 16 HAWAII2RG cooled to 95K with their front-end readout electronic cooled to 140K, integrated on a mechanical focal plane structure made with molybdenum and aluminum. The detection subsystem is mounted on the optomechanical subsystem structure - a warm electronic subsystem (280K) composed of a data processing / detector control unit and of an instrument control unit that interfaces with the spacecraft via a 1553 bus for command and control and via Spacewire links for science data This presentation describes the architecture of the instrument at the end of the phase C (Detailed Design Review), the expected performance, the technological key challenges and preliminary test results obtained for different NISP subsystem breadboards and for the NISP Structural and Thermal model (STM)

VIH, VHB, VHC (évaluation des connaissances du "grand public" à l'aube du 3ème millénaire)

NANCY1-SCD Medecine (545472101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Analysis of laser shock waves and resulting surface deformations in an Al-Cu-Li aluminium alloy

Version éditeur : http://iopscience.iop.org/0022-3727/45/33/335304Laser shock processing (LSP) is now a recognized surface treatment for improving fatigue or corrosion behaviour of metallic materials through the generation of a compressive stress field. In turn, the analysis of shock wave propagation is of primary importance to predict numerically morphological and mechanical surface modifications. Considering experimental and numerical analysis of shock wave propagation, and surface deformations induced by single impacts, a 2050 aluminium alloy having different microstructural was investigated under laser-shock loading. In a first step, the evolution of shock wave attenuation and elastic precursor amplitude was correctly reproduced by finite element simulations, and in a second step, surface deformations induced by 1 to 6 local impacts were also compared satisfactorily with experiments. This allowed us to validate mechanical loading and materials’ constitutive law, but did not allow determining accurately residual stress fields on a single impact

Comparative effects of mercury contamination and wastewater effluent input on Gram-negative merA gene abundance in mudflats of an anthropized estuary (Seine, France): a microcosm approach

International audienceThe macrotidal Seine estuary (France) is one of the most man-altered and mercury-contaminated European estuaries. Molecular quantification by competitive PCR has shown that the highest quantities of Gram-negative merA genes in intertidal freshwater mudflat sediments are located in recent sediment deposits independently of mercury concentrations, suggesting that particle-attached allochtonous mercury-resistant merA bacteria are deposited on mudflat surfaces. To investigate this hypothesis, a microcosm experiment was carried out to evaluate the respective contributions of (i) the input of allochtonous merA bacteria supplied by WWTP-treated effluents and (ii) merA gene abundance corresponding to a response of the sediment's autochthonous bacterial community to mercury contamination. Gram-negative merA gene quantification and T-RFLP analysis of both 16S rDNA and merA genes demonstrated that deposited allochtonous bacteria did not develop in estuarine sediments, whereas mercury contamination (10 μg g−1 wet sediment) selected an autochthonous mercury-resistant merA bacterial community. Thus, in mudflats of highly anthropized macrotidal estuaries, i.e. those subjected to intense hydrosedimentary processes and continuously contaminated by mercury and fecal bacteria, inputs of allochtonous merA bacteria are largely responsible for the high quantities of merA genes on the surface of mudflat sediments