Le « Semestre Rebond » après la réorientation obligatoire en première année commune des études de santé (PACES) en France

International audienceL'échec en premier cycle universitaire s'est constitué en question politique et scientifique, avec une situation encore plus marquée pour les études de santé. Pourtant, peu de recherches encore sont consacrées à ces situations et aux dispositifs d'aide proposés. Objectifs?: Cette recherche vise à caractériser les profils des étudiants en situation d'échec, leurs stratégies de réorientation au nombre desquelles l'accès à un dispositif d'accompagnement proposé à l'université de Bourgogne, le semestre Rebond. Elle met en évidence les apports de ce dispositif perçus par les étudiants et ses effets sur les parcours de formation ultérieurs. Méthodes?: L'étude mobilise les données d'une enquête réalisée auprès des étudiants et les données administratives de l'établissement, auxquelles sont appliqués des traitements statistiques et des modélisations économétriques (régressions logistiques) permettant de dégager les facteurs explicatifs en appréciant de manière simultanée le poids respectif de chacun de ces facteurs, toutes choses égales par ailleurs. Résultats?: Les résultats montrent la variété des choix des étudiants à l'issue de l'échec, choisissant ou non d'intégrer le dispositif de soutien proposé, ces choix étant marqués par le poids de l'environnement social et le passé scolaire des étudiants. Conclusion?: Si des effets positifs du dispositif sont identifiés, ce sont pourtant les étudiants ayant le parcours scolaire le plus favorable qui, bien qu'utilisant moins fréquemment le dispositif d'aide, sont plus fréquemment encore inscrits à l'université deux ans après leur échec, relativement aux étudiants s'étant engagés dans le dispositif d'aide

Détection ampérométrique des <em>Escherichia coli</em> productrices de beta-lactamases à spectre étendu dans les effluents de station d’épuration

National audienceLes Escherichia coli productrices de β-lactamases à spectre étendu (E. coli BLSE) sont résistantes à la plupart des β-lactamines et deviennent un problème majeur de santé publique en médecine humaine. Leur présence dans le tube digestif des humains fait que grandes quantités d’E. coli BLSE sont présentes dans les eaux usées qui arrivent dans les stations d’épuration (STEP). Malgré les traitements réalisés dans les STEP, des quantités non négligeables d’E. coli BLSE sont encore présentes dans les effluents traités directement rejetés dans l’environnement. Ces rejets peuvent être à l’origine d’une contamination des eaux récréatives et constituer un risque sanitaire pour les populations exposées. La mise au point de tests rapides et pratiques est donc nécessaire pour détecter et quantifier ces E. coli BLSE dans les réseaux d’eaux usées et les environnements naturels. Cette étude à eu pour objectif de développer une méthode ampérométrique rapide pour quantifier les E. coli BLSE dans les effluents de STEP. La première étape consiste en une double filtration sur membranes d’un échantillon d’eau de STEP, suivie d’une analyse ampérométrique en deux étapes : (1) une mise en culture (4-5h) de chaque membrane dans un milieu liquide contenant du céfotaxime ± acide clavulanique (inhibiteur de BLSE) et (2) une incubation (15min) de chaque culture filtrée sur membrane en présence de Nitrocéfine, dont l’hydrolyse par les β-lactamases est suivie par ampérométrie. Deux intensités sont ainsi mesurées : iCef et iClav et la valeur i = iCef - iClav est utilisée pour quantifier les E. coli BLSE présentes dans l’échantillon en se basant sur des courbes de calibration. Une bonne corrélation de cette estimation ampérométrique (5-6h) avec un dénombrement classique sur milieu gélosé (24h) est obtenue après avoir analysé une quarantaine d’échantillons. Cette méthode est très prometteuse dans le domaine de l’analyse des eaux usées et des eaux récréatives

An electrochemical DNA biosensor for the detection of CTX-M extended-spectrum beta-lactamase-producing Escherichia coli in soil samples

International audienceAn electrochemical hybridization assay involving neutravidin-coated carbon screen-printed electrodes and an HRP-based detection have been shown to provide an effective tool for the genotypic analysis of extended-spectrum beta-lactamase-producing E. coli strains in complex samples such as soil. (c) 2012 Elsevier B.V. All rights reserved

An amperometric method for the rapid detection of extended-spectrum β-lactamase producing<em> Escherichia coli</em> in wastewater treatment plant effluents

National audienceContext: Extended-spectrum β-lactamase-producing Escherichia coli (ESBL E. coli) are resistant to most β-lactams and have become a major concern in human and veterinary medicine. As E. coli and antibiotic resistant strains are part of the intestinal flora of humans, large amounts of these bacteria are present in wastewaters. Though treatments are performed in wastewater treatment plants (WWTP), large quantities of bacteria are still present in the treated effluents rejected into the environment. These releases can cause contaminations of recreational waters and thus present a health risk to exposed populations. Therefore, rapid and convenient assays are highly desired for the quantification of ESBL E. coli in the wastewater network and in natural environments. Objective of the study: Development of a nitrocefin-based amperometric method for the rapid quantification of ESBL E. coli in WWTP effluents Methods: Raw and treated wastewaters were filtered in duplicate through 0.45 μm filters (HAWP, 47 mm, Millipore). The amperometric assay involved two main steps: (1) the subculturing of the filtered samples in the presence of cefotaxime supplemented or not with the potassium clavulanate (ESBL inhibitor) for a few hours (4-5h) followed by, (2) the incubation of each subculture filtrate (v = 10 mL; HVLP filter, 0.45 μm, 13 mm, Millipore) with the nitrocefin substrate which hydrolysis was monitored by amperometry. iCef and iClav correspond to the intensity of the anodic current measured (~ + 0.2 V vs. Ag/AgCl) for the sample incubated with the cefotaxime without and with potassium clavulanate, respectively. The value i = iCef – iClav was calculated and selected as the analytical response to assess the amount of EBSL E. coli producers. Results: The mean calibration plots for the raw and treated wastewaters (Figure 1) were obtained by analyzing CTX-M type ESBL E. coli strains found in wastewaters (blaCTX-M-1 and blaCTX-M-15 genes) and were used for the determination of ESBL E. coli in 20 raw wastewater and 20 treated wastewater samples. To check the reliability of the amperometric assay, the results were compared to a conventional counting on TBX agar plates supplemented with cefotaxime (Figure 2). Conclusion: An excellent correlation was obtained between the amperometric assay and the enumeration. This amperometric assay (5-6h) which is considerably less time-consuming than the culture-based method (24h) holds great promise for the rapid quantification of ESBL E. coli in the wastewater networks but also in other types of water samples (rivers, marine waters, etc.)

Amperometric detection of extended-spectrum β-lactamase activity : application to the characterization of resistant <em>E.coli</em> strains

EA MERS CT3International audienceThe amperometric detection of extended-spectrum β-lactamase (ESBL) with carbon screen-printed sensors was investigated in the presence of the Nitrocefin, a commercially-available β-lactamase chromogenic cephalosporin substrate. Using an ESBL isolated from a clinical sample, it was shown for the first time that the intensity of a specific anodic pic current (EP = [similar]+0.3 V vs. Ag/AgCl) resulting from the catalytic hydrolysis of the β-lactam ring was proportional to the amount of ESBL. The proof-of-principle of a novel susceptibility assay for the rapid and accurate identification of ESBL- producing bacteria was then demonstrated. The detection scheme relied on (i) the culture of the sample in a medium containing the cefotaxime supplemented or not with the clavulanic acid inhibitor to allow the specific determination of ESBL producers (ii) followed by the incubation of the bacteria with the Nitrocefin and (iii) the measurement of the enzyme product by cyclic voltammetry. The amperometric assay was further applied to the characterization of E. coli strains and to the quantification of the ESBL producers. A detection limit of 5 × 104 cfu mL−1 ESBL-producing E. coli was achieved after a 10 min incubation time. In contrast to the approved routine assays, the electrochemical approach, which did not require isolated colonies to be performed, provided quantified results regarding ESBL activity within a few hours. Finally, owing to its cost-effectiveness, portability and simplicity, this test holds great promise for clinical and environmental applications

Evaluation de la qualité microbiologique des eaux de baignade via la mesure ampérométrique d’activités enzymatiques

BIOMEEAUBEvaluation de la qualité microbiologique des eaux de baignade via la mesure ampérométrique d’activités enzymatiques. XV. Colloque du Groupe Français de Bioélectrochimi

A nitrocefin-based amperometric assay for the rapid quantification of extended-spectrum β-lactamase-producing Escherichia coli in wastewaters

International audienceA sensitive and inexpensive amperometric assay based on the electrochemical detection of the beta-lactamase activity using the nitrocefin as substrate was developed for the rapid and quantitative detection of extended spectrum beta-lactamase-producing Escherichia colt (ESBL-EC) in urban wastewaters. The specific detection of ESBL-EC was achieved by culturing the filtered sample in a medium containing the cefotaxime supplemented or not with the potassium clavulanate inhibitor. This step was followed by the incubation of each subculture filtrate with the nitrocefin substrate which hydrolysis was monitored by amperometry using disposable carbon screen-printed sensors. Current intensities i(Cef) and i(Clav) correspond to the intensity of the anodic current measured (similar to+ 0.2 V vs. Ag/AgCl) for the sample incubated with the cefotaxime without and with potassium clavulanate, respectively. The intensity value i = i(Cef) iClav was chosen as the analytical response. ESBL-EC calibration plots were established with artificially contaminated wastewater samples. This assay allowed the detection of ESBL-EC amounts as low as 10 cfu in treated effluents and 100 cfu in raw wastewaters with short time analysis of 5.5 h and 4.5 h, respectively. The amperometric method was applied to the analysis of 38 wastewater samples and the results were in good agreement with CFU counts on a selective chromogenic medium for 24 h. Owing to its rapidity, convenience, low-cost and portability, this assay is a promising tool to obtain quantitative data on antimicrobial-resistant E. coli in wastewater effluents. Furthermore, this assay might be used to improve wastewater treatment plant processes in order to minimize the release of antibiotic resistant bacteria into the aquatic environment

A voltammetric test for the rapid discrimination of β-lactamase-producing <em>Enterobacteriaceae</em> in blood cultures

International audienceThe accurate identification of β-lactamases produced by Enterobacteriaceae is a major challenge in clinical laboratories in order to optimize antimicrobial treatment and patient care. We describe here a rapid voltammetric-based method to detect and to discriminate β-lactamase activity in Enterobacteriaceae i.e., penicillinase, cephalosporinase (inducible or overproduced), extended-spectrum beta-lactamase and carbapenemase producers. After a 2-h growth step of the sample under three separate conditions: 1) LB (Luria-Bertani) medium, 2) LB supplemented with 4 μg/mL cefotaxime and 3) LB supplemented with 4 μg/mL cefotaxime and 100 μg/mL potassium clavulanate, the β-lactamase activity was measured by incubating a 0.5 mM nitrocefin solution for 15 min followed by the voltammetric detection of the hydrolyzed nitrocefin with disposable carbon screen printed sensors. The development and the calibration of the method were carried out by analyzing pure cultures of fifty-seven strains with well characterized β-lactam-resistance phenotypes. Thanks to the combination of the three currents (i(1), i(2), i(3)) recorded for each tested bacteria, the proposed procedure allowed to distinguish the different classes of β-lactamase producers. In the second part of the study, the method was applied to the analysis of one hundred and fifteen samples Enterobacteriaceae-positive blood culture samples of bacteraemic patients. Overall data showed that the voltammetric method offered a sensitivity of 100% and a specificity of 80%. Interestingly, all of sixteen samples infected by a third-generation cephalosporins-resistant bacteria (i.e. ESBL and overproduced cephalosporinase producers) were detected. This study clearly demonstrated that the voltammetric assay is an efficient alternative technique for the rapid discrimination of β-lactamases-producing Enterobacteriaceae in blood culture. In contrast to the approved routine assays, the electrochemical test did not require isolated colonies to be performed and was thus carried out in less than 3 h which could allow early administration of an appropriate antibiotic therapy

A thin layer-based amperometric enzyme immunoassay for the rapid and sensitive diagnosis of respiratory syncytial virus infections

EA MERS CTInternational audienceA simple electrochemical sandwich immunoassay involving a polystyrene microarray slide coated with monoclonal capture antibodies and carbon screen-printed sensors (SPS) was designed for the rapid diagnosis of respiratory syncytial virus (RSV). The detection of the antibody-antigen complex formation relied on the use of a horseradish peroxidase conjugate. Its chronoamperometric measurement detection was performed by confining a droplet of H2O2/3.3',5,5'-tetramethylbenzidine enzyme substrate/mediator solution within a thin layer between one spot of the microarray and the surface of one screen-printed electrochemical cell. The accumulation of the enzyme product in the thin film of liquid enhanced the electrochemical response which allowed the development of a rapid (25 min) and sensitive thin layer-based amperometric (TLA) enzyme immunoassay. The method was successfully compared to commercially-available immunofluorescent and real-time PCR assays for RSV testing in respiratory secretion clinical samples. This suggests that owing to its rapidity, convenience, low-cost, portability and ability to provide quantified results, the reported concept could be a promising point-of-care diagnostic tool to screen patients with suspected respiratory infection or other types of infectious diseases

Rapid amperometric detection of <em>Escherichia coli</em> in wastewater by measuring beta-D glucuronidase activity with disposable carbon sensors

International audienceAn assay on the indirect amperometric quantification of the beta-D-Glucuronidase (GLUase) activity was developed for the rapid and specific detection of Escherichia coli (E. coli) in complex environmental samples. The p-aminophenyl beta-D-glucopyranoside (PAPG) was selected as an electrochemical substrate for GLUase measurement and the p-aminophenol (PAP) released during the enzymatic hydrolysis was monitored by cyclic voltammetry with disposable carbon screen-printed sensors. The intensity of the measured anodic peak current was proportional to the amount of GLUase, and therefore to the number of E. coli in the tested sample. Once the substrate concentration and pH values optimized, a GLUase detection limit of 10 ng mL(-1) was achieved. Using a procedure involving a filtration step of the bacteria followed by their incubation with the substrate solution containing both the nonionic detergent Triton X-100 as permeabilization agent and the culture media Luria broth to monitor the growth, filtered bacterial cells ranging from 5 x 10(4) to 10(8) UFC/membrane were detected within 3 h. The amperometric assay was applied to the determination of fecal contamination in raw and treated wastewater samples and it was successfully compared with conventional bacterial plating methods and uidA gene quantitative PCR. Owing to its ability to perform measurements in turbid media, the GLUase amperometric method is a reliable tool for the rapid and decentralized quantification of viable but also nonculturable E. coli in complex environmental samples