Caractérisation hydrodynamique de la structure des écoulements dans les lignes de transformation des industries agroalimentaires et conséquences sur le nettoyage de souillures bactériennes (étude exploratoire sur l'intérêt des écoulements pulsés)

Les travaux présentés dans ce manuscrit traitent de l effet de la géométrie et de l écoulement sur le décrochement de spores de B. cereus de surfaces inertes au cours d une opération de nettoyage en place. Étant donnée leur forte adhésion à la paroi des équipements et leur aptitude à résister au nettoyage, ces spores présentent un risque sanitaire majeur pour l agro-industrie. Les objectifs visés consistent à étudier l effet de la géométrie sur la répartition des forces de cisaillement pariétal et à comprendre quelles sont les répercutions de la forme de l écoulement sur la contamination bactérienne avant et après nettoyage. Pour ce faire, la caractérisation de l écoulement dans plusieurs configurations composées de différentes géométries, couramment utilisées en industrie laitière, a été effectuée par des mesures de profils de vitesses (méthode de vélocimétrie ultrasonore pulsée) et des composantes moyenne et fluctuante du cisaillement pariétal (méthode polarographique). Par la suite, les niveaux de contamination bactérienne initiale et résiduelle, avant et après nettoyage, ont été déterminés au sein des différentes géométries testées. L effet des interactions entre les accidents hydrauliques sur l écoulement a permis d expliquer les différences de niveaux de contaminations initiale et résiduelle. Les analyses effectuées aux niveaux des soudures et des raccords ont montré que l adhésion et le décrochement des spores dans ces zones sont indépendants de la contrainte de cisaillement, ils sont plutôt liés à l état de surface du support d adhésion. Les interactions entre les tourbillons de différentes échelles et les spores en suspension ou adhérées à une surface ont été discutées. Les phénomènes de décrochement et de redéposition des spores ont été reliés à la taille et à l activité des structures tourbillonnaires en proche paroi.La seconde partie de ce travail concerne l application des écoulements pulsés aux procédures de nettoyage en place. Un nouveau système de génération de pulsations a été étudié. Les mesures réalisées par la méthode polarographique ont montré une nette augmentation de la contrainte moyenne de cisaillement pariétal, alors que l analyse spectrale a mis en exergue l effet des pulsations sur l énergie fluctuante du gradient pariétal de vitesse. La comparaison avec un écoulement stationnaire a montré la contribution de chacun des paramètres caractéristiques des pulsations dans le décrochement des spores de B. cereus. Enfin, une étude cinétique a révélé une augmentation de la vitesse de décrochement des spores en présence d un écoulement pulsé qui pourrait permettre de mieux gérer la durée de l opération de nettoyage.The present work deals with both effects of the geometry and the flow field on the removal of B. cereus spores from inert surfaces during a cleaning in place (CIP) procedure. Due to their strong ability to adhere to the equipment surfaces and their high resistance to cleaning process, these spores present a major sanitary hazard in the food industry. The objectives of this work were to study the effect of the geometry arrangements on the distribution of the local wall shear stress and to understand consequences of flow pattern on the bacterial soiling before and after a cleaning procedure. Flow characterisation of different loops containing several pieces of equipment used in dairy processing lines was carried out by means of instantaneous velocity profiles (Ultrasonic Doppler Velocimetry method) and wall shear stress components (electrochemical method). Initial and residual soiling levels, before and after cleaning, were determined for each geometry and explained by the effect of various interacting geometrical elements on the flow. Cleanability analysis at welding zones and gaskets has shown that the adhesion and the removal of spores in these zones are independent of the shear stress, they are rather related to the surface properties. Interaction between eddies of different sizes and suspended or adhered spores were studied. The removal and the deposition phenomena of spores were related to the size of the eddies and their activity near the wall. The second part of this work concerned pulsed flows application in CIP procedure. A new pulsations generator was used. Electrochemical measurements showed a significant increase in mean wall shear stress, whereas spectral analysis put forward pulsations effect on fluctuation energy of shear stress. Comparison with a steady flow showed the contribution of each pulsation parameter in the removal of adhered B. cereus spores. Lastly, the study of the cleaning kinetics has shown the increase of the removal constant rate of spores using pulsed flow, which allows controlling the cleaning duration.NANTES-BU Sciences (441092104) / SudocNANTES-Ecole Centrale (441092306) / SudocSudocFranceF

Influence des contraintes de cisaillement sur la nettoyabilité des équipements

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Hygienic design: effect of hydrodynamic on the cleanability of a food processing line

International audienceHydrodynamic effect on the numbers of adhering Bacillus cereus spores before and after cleaning in place of part of a dairy processing line was investigated using nonintrusive flow characterization (local wall shear stresses and velocity profiles measurements). Geometrical changes, like gradual asymmetric pipe contractions and pipe expansions and bends, induce nonhomogeneous distribution of the initial and the residual soiling levels. Moreover, the recirculation zone resulting from the flow detachment after the expansion, allowed to explain the high level of adhered spores downstream of this geometrical change due to the generated shear stresses. The resistance to cleaning processes in the same zones is mainly governed by the adhesion strength of spores induced by the applied flow rate it? the contamination step. Welding and gasket areas, located at different positions in the loop, constituted deposit spots for spores and remained difficult to clean despite high-shear stress forces involved. (C) 2008 American Institute of Chemical Engineers

Viability and surface properties of spores subjected to a cleaning-in-place procedure: consequences on their ability to contaminate surfaces of equipment

International audienceThis study was designed to evaluate how conditions encountered by spores during cleaning-in-place (CIP) procedures affected their surface properties, their viability and ability to contaminate materials. Spores from five Bacillus cereus strains were treated with NaOH at high temperature. Results revealed that high temperatures (exceeding 60 degrees C) and NaOH concentrations (over 0.5%) were required to significantly decrease spore viability (3-5 log decrease). In these conditions, modifications were also clearly observed by microscopy to various surface structures of spores (appendages, exosporium, and especially to the hair-like nap) but also to their coat. Therefore, the ability of culturable spores to adhere decreased for the majority of strains tested. We then demonstrated that spores in suspension in NaOH could adhere to surfaces of a CIP rig and that the contamination level was controlled by flow pattern. Consequently, re-adhesion along the processing line might occur during CIP procedures and this phenomenon must be taken into account when defining cleaning strategies

Marine sublittoral benthos fails to track temperature in response to climate change in a biogeographical transition zone

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Dystrophin threshold level necessary for normalisation of nNOS, iNOS and RyR1 nitrosylation in GRMD dystrophinopathy

International audienceCurrently, the clinically most advanced strategy to treat Duchenne muscular dystrophy (DMD) is the exon skipping strategy. Whereas antisense oligonucleotide-based clinical trials are underway for DMD, it is essential to determine a dystrophin restoration threshold needed to ensure improvement of muscle physiology at the molecular level. A preclinical trial was recently conducted in golden retriever muscular dystrophy (GRMD) dogs treated in a forelimb by locoregional delivery of rAAV8-U7snRNA to promote exon skipping on the canine dystrophin messenger. Here, we exploited the rAAV8-U7snRNA transduced GRMD muscle samples, well-characterized for their percentage of dystrophin-positive fibers, in the aim to define a threshold of dystrophin rescue necessary for normalization of the status of the neuronal nitric oxide synthase mu (nNOSµ), the inducible nitric oxide synthase (iNOS), and the ryanodine receptor-calcium release channel type 1 (RyR1), crucial actors for an efficient contractile function. Results showed that the restoration of dystrophin in 40% of muscle fibers is needed to decrease the abnormal cytosolic nNOSµ expression and to reduce the overexpression of iNOS, these two parameters leading to a reduction of the NO level into the muscle fiber. Furthermore, the same percentage of dystrophin-positive fibers of 40 % was associated with the normalization of the RyR1 nitrosylation status and to a stabilization of the RyR1/calstabin1 complex that is required to facilitate coupled gating. We concluded that a minimal threshold of 40% of dystrophin-positive fibers is necessary for the reinstatement of central proteins needed for a proper muscle contractile function, and thus identified a rate of dystrophin expression significantly improving, at the molecular level, the dystrophic muscle physiology

Long-Term Effectiveness, Safety and Tolerability of Fingolimod in Patients with Multiple Sclerosis in Real-World Treatment Settings in France: The VIRGILE Study

Online ahead of printInternational audienceIntroduction: It is important to confirm the effectiveness and tolerability of disease-modifying treatments for relapsing-remitting multiple sclerosis (RRMS) in real-world treatment settings. This prospective observational cohort study (VIRGILE) was performed at the request of the French health authorities. The primary objective was to evaluate the effectiveness of fingolimod 0.5 mg in reducing the annualised relapse rate (ARR) in patients with RRMS.Methods: Participating neurologists enrolled all adult patients with RRMS starting fingolimod treatment between 2014 and 2016, who were followed for 3 years. Follow-up consultations took place at the investigator's discretion. The primary outcome measure was the change in ARR at month 24 after fingolimod initiation. Relapses and adverse events were documented at each consultation; disability assessment (EDSS) and magnetic resonance imagery were performed at the investigator's discretion.Results: Of 1055 eligible patients, 633 patients were assessable at month 36; 405 (64.0%) were treated continuously with fingolimod for 3 years. The ARR decreased from 0.92 ± 0.92 at inclusion to 0.31 ± 0.51 at month 24, a significant reduction of 0.58 [95% CI - 0.51 to - 0.65] relapses/year (p < 0.001). Since starting fingolimod, 461 patients (60.9%) remained relapse-free at month 24 and 366 patients (55.5%) at month 36. In multivariate analysis, no previous disease-modifying treatment, number of relapses in the previous year and lower EDSS score at inclusion were associated with a greater on-treatment reduction in ARR. The mean EDSS score remained stable over the course of the study. Sixty-one out of 289 (21.1%) patients presented new radiological signs of disease activity. Treatment-related serious adverse events were lymphopenia (N = 21), bradycardia (N = 19), elevated transaminases (N = 9) and macular oedema (N = 9).Conclusions: The effectiveness and tolerability of fingolimod in everyday clinical practice are consistent with findings of previous phase III studies. Our study highlights the utility of fingolimod for the long-term management of patients with multiple sclerosis

Effect of general anaesthesia on functional outcome in patients with anterior circulation ischaemic stroke having endovascular thrombectomy versus standard care: a meta-analysis of individual patient data

Background: General anaesthesia (GA) during endovascular thrombectomy has been associated with worse patient outcomes in observational studies compared with patients treated without GA. We assessed functional outcome in ischaemic stroke patients with large vessel anterior circulation occlusion undergoing endovascular thrombectomy under GA, versus thrombectomy not under GA (with or without sedation) versus standard care (ie, no thrombectomy), stratified by the use of GA versus standard care. Methods: For this meta-analysis, patient-level data were pooled from all patients included in randomised trials in PuMed published between Jan 1, 2010, and May 31, 2017, that compared endovascular thrombectomy predominantly done with stent retrievers with standard care in anterior circulation ischaemic stroke patients (HERMES Collaboration). The primary outcome was functional outcome assessed by ordinal analysis of the modified Rankin scale (mRS) at 90 days in the GA and non-GA subgroups of patients treated with endovascular therapy versus those patients treated with standard care, adjusted for baseline prognostic variables. To account for between-trial variance we used mixed-effects modelling with a random effect for trials incorporated in all models. Bias was assessed using the Cochrane method. The meta-analysis was prospectively designed, but not registered. Findings: Seven trials were identified by our search; of 1764 patients included in these trials, 871 were allocated to endovascular thrombectomy and 893 were assigned standard care. After exclusion of 74 patients (72 did not undergo the procedure and two had missing data on anaesthetic strategy), 236 (30%) of 797 patients who had endovascular procedures were treated under GA. At baseline, patients receiving GA were younger and had a shorter delay between stroke onset and randomisation but they had similar pre-treatment clinical severity compared with patients who did not have GA. Endovascular thrombectomy improved functional outcome at 3 months both in patients who had GA (adjusted common odds ratio (cOR) 1·52, 95% CI 1·09–2·11, p=0·014) and in those who did not have GA (adjusted cOR 2·33, 95% CI 1·75–3·10, p&lt;0·0001) versus standard care. However, outcomes were significantly better for patients who did not receive GA versus those who received GA (covariate-adjusted cOR 1·53, 95% CI 1·14–2·04, p=0·0044). The risk of bias and variability between studies was assessed to be low. Interpretation: Worse outcomes after endovascular thrombectomy were associated with GA, after adjustment for baseline prognostic variables. These data support avoidance of GA whenever possible. The procedure did, however, remain effective versus standard care in patients treated under GA, indicating that treatment should not be withheld in those who require anaesthesia for medical reasons