Simplification d'images couleurs par analyse de contraste en multirésolution

Nous abordons dans ce papier le problème de la simplification extrême d'une image numérique couleur, suivant un principe de rehaussement du contraste multirésolution: la représentation simplifiée que nous obtenons (même grossière) peut alors s'avérer utile pour un transfert ou un traitement de l'image, du type de ce qui est nécessaire dans les applications d'indexation et de recherche dans les banques d'images

The Secretome of <em>Vibrio cholerae</em>

Vibrio cholerae is a facultative human pathogen responsible for the cholera disease which infects millions of people worldwide each year. V. cholerae is a natural inhabitant of aquatic environments and the infection usually occurs after ingestion of contaminated water or food. The virulence factors of V. cholerae have been extensively studied in the last decades and include the cholera toxin and the coregulated pilus. Most of the virulence factors of V. cholerae belong to the secretome, which corresponds to all the molecules secreted in the extracellular environment such as proteins, exopolysaccharides, extracellular DNA or membrane vesicles. In this chapter, we review the current knowledge of the secretome of V. cholerae and its role in virulence, colonization and resistance. In the first section, we focus on the proteins secreted through conventional secretion systems. The second and third sections emphasize on the membrane vesicles and on the secretome associated with biofilms

The emergence of Vibrio pathogens in Europe: ecology, evolution, and pathogenesis

Global change has caused a worldwide increase in reports of Vibrio-associated diseases with ecosystem-wide impacts on humans and marine animals. In Europe, higher prevalence of human infections followed regional climatic trends with outbreaks occurring during episodes of unusually warm weather. Similar patterns were also observed in Vibrio-associated diseases affecting marine organisms such as fish, bivalves and corals. Basic knowledge is still lacking on the ecology and evolutionary biology of these bacteria as well as on their virulence mechanisms. Current limitations in experimental systems to study infection and the lack of diagnostic tools still prevent a better understanding of Vibrio emergence. A major challenge is to foster cooperation between fundamental and applied research in order to investigate the consequences of pathogen emergence in natural Vibrio populations and answer federative questions that meet societal needs. Here we report the proceedings of the first European workshop dedicated to these specific goals of the Vibrio research community by connecting current knowledge to societal issues related to ocean health and food security

Whole Transcriptome Profiling of Successful Immune Response to Vibrio Infections in the Oyster Crassostrea gigas by Digital Gene Expression Analysis

The cultivated Pacific oyster Crassostrea gigas has suffered for decades large scale summer mortality phenomenon resulting from the interaction between the environment parameters, the oyster physiological and/or genetic status and the presence of pathogenic microorganisms including Vibrio species. To obtain a general picture of the molecular mechanisms implicated in C. gigas immune responsiveness to circumvent Vibrio infections, we have developed the first deep sequencing study of the transcriptome of hemocytes, the immunocompetent cells. Using Digital Gene Expression (DGE), we generated a transcript catalog of up-regulated genes from oysters surviving infection with virulent Vibrio strains (Vibrio splendidus LGP32 and V. aestuarianus LPi 02/41) compared to an avirulent one, V. tasmaniensis LMG 20012T. For that an original experimental infection protocol was developed in which only animals that were able to survive infections were considered for the DGE approach. We report the identification of cellular and immune functions that characterize the oyster capability to survive pathogenic Vibrio infections. Functional annotations highlight genes related to signal transduction of immune response, cell adhesion and communication as well as cellular processes and defence mechanisms of phagocytosis, actin cytosqueleton reorganization, cell trafficking and autophagy, but also antioxidant and anti-apoptotic reactions. In addition, quantitative PCR analysis reveals the first identification of pathogen-specific signatures in oyster gene regulation, which opens the way for in depth molecular studies of oyster-pathogen interaction and pathogenesis. This work is a prerequisite for the identification of those physiological traits controlling oyster capacity to survive a Vibrio infection and, subsequently, for a better understanding of the phenomenon of summer mortality

Trends of the Major Porin Gene (ompF) Evolution: Insight from the Genus Yersinia

OmpF is one of the major general porins of Enterobacteriaceae that belongs to the first line of bacterial defense and interactions with the biotic as well as abiotic environments. Porins are surface exposed and their structures strongly reflect the history of multiple interactions with the environmental challenges. Unfortunately, little is known on diversity of porin genes of Enterobacteriaceae and the genus Yersinia especially. We analyzed the sequences of the ompF gene from 73 Yersinia strains covering 14 known species. The phylogenetic analysis placed most of the Yersinia strains in the same line assigned by 16S rDNA-gyrB tree. Very high congruence in the tree topologies was observed for Y. enterocolitica, Y. kristensenii, Y. ruckeri, indicating that intragenic recombination in these species had no effect on the ompF gene. A significant level of intra- and interspecies recombination was found for Y. aleksiciae, Y. intermedia and Y. mollaretii. Our analysis shows that the ompF gene of Yersinia has evolved with nonrandom mutational rate under purifying selection. However, several surface loops in the OmpF porin contain positively selected sites, which very likely reflect adaptive diversification Yersinia to their ecological niches. To our knowledge, this is a first investigation of diversity of the porin gene covering the whole genus of the family Enterobacteriaceae. This study demonstrates that recombination and positive selection both contribute to evolution of ompF, but the relative contribution of these evolutionary forces are different among Yersinia species

Molecular effectors of the Crassostrea gigas / Vibrio splendidus interaction. Role of the OmpU porin in resistance and evasion to the immune response.

Vibrio splendidus LGP32 est une bactérie pathogène associée aux épisodes de mortalités estivales qui affectent la production d'huître Crassostrea gigas depuis des décennies. Nous avons montré ici que la porine OmpU était un effecteur majeur de l'interaction V. splendidus / C. gigas. Nous avons pour cela construit un mutant ΔompU de V. splendidus. Celui-ci nous a permis de mo ntrer l'implication de OmpU (i) dans la résistance de V. splendidus aux antimicrobiens, incluant ceux de l'huître, (ii) dans la « fitness » chez l'huître, et (iii) dans la virulence en infections expérimentales (mortalités de 56 % pour le sauvage versus pour le 11% mutant). En accord avec ces résultats, nous avons montré que la délétion de ompU modifiait la sécrétion de protéines dont l'expression est contrôlée par les voies de régulation de la virulence (ToxR) et de l'intégrité membranaire (SigmaE). Par ailleurs, nous avons montré que OmpU jouait un rôle essentiel dans la reconnaissance par les hémocytes. En effet, (i) in vivo, les gènes hémocytaires répondent différemment à l'infection par le Vibrio sauvage ou ΔompU, et (ii) in vitro, OmpU est nécessaire à l'invasion hémocytaire par V. splendidus. Cette invasion utilise la phagocytose dépendante de l'intégrine b et la SOD extracellulaire du plasma d'huître comme opsonine qui lie OmpU. Ainsi, OmpU est un facteur de virulence majeur qui permet l'infection des hémocytes dans lesquels il est capable de survivre en inhibant la formation de radicaux oxygénés et de vacuoles acides. La résistance du Vibrio aux antimicrobiens hémocytaires de l'huître, elle-même dépendante de OmpU, est probablement un élément supplémentaire favorable à la survie intra-cellulaire.Vibrio splendidus LGP32 is a bacterial pathogen associated to the summer mortality outbreaks that have affected the production of Crassostrea gigas oysters over the past decades. We showed here that the OmpU porin is a major effector of the V. splendidus / C. gigas interaction. For that, we have constructed a ΔompU mutant of V. splendidus, and shown that the OmpU porin is implicated (i) in the resistance of V. splendidus to antimicrobials, including those of oyster, (ii) in its in vivo fitness, and (iii) in its virulence in oyster experimental infections (mortalities have been reduced from 56 % to 11 % upon mutation). In agreement, we have shown that the ompU deletion modified the expression of secreted proteins controlled by the virulence (ToxR) and the membrane integrity (SigmaE) regulation pathways. Furthermore, we have shown that OmpU has a major role in the recognition of V. splendidus by oyster hemocytes. Indeed, (i) in vivo, hemocyt e genes displayed differential responses to an infection with the wild-type or the ΔompU mutant, and (ii) in vitro, OmpU was necessary for hemocyte invasion by V. splendidus. This invasion process required the hemocyte b-integrin and the oyster plasma extracellular SOD, which was found to act as an opsonin recognizing OmpU. Thus, OmpU is a major virulence factor that allows infection of hemocytes in which V. splendidus is able to survive by inhibiting the production of reactive oxygen species and the formation of acidic vacuoles. Resistance of V. splendidus to hemocyte antimicrobials, which is also OmpU-dependant, is probably an additional determinant of V. splendidus intracellular survival

Rôle de la conciliation des sphères de vie dans la prédiction de l’intention de départ chez les sapeurs-pompiers volontaires français

Alors que l’on constate ces dernières années un taux de départ en constante augmentation chez les sapeurs-pompiers volontaires, différentes études voient le jour concernant ses antécédents. Cependant, encore peu semblent s’intéresser à l’impact de la conciliation des sphères de vie chez les volontaires d’autant plus susceptibles d’être exposés à un déséquilibre. La présente étude avait pour but de proposer un modèle de prédiction de l’intention de départ des sapeurs-pompiers volontaires français, en articulant cette problématique avec celle de la conciliation des sphères de vie. Afin d’atteindre cet objectif, un recueil de données a été réalisé auprès de 183 sapeurs-pompiers volontaires d’un SDIS (Service départemental d’incendie et de secours) français. La modélisation en équations structurales en variables latentes a permis de confirmer que les déséquilibres des sphères de vie relatifs à la tension et au temps ont des effets sur l’intention de départ du volontaire. Cet effet doit être différencié pour les deux formes de déséquilibre : 1) l’effet du déséquilibre relatif à la tension sur l’intention de départ est médiatisé d’abord par l’épuisement et ensuite par la satisfaction à l’égard de l’activité de sapeur-pompier volontaire ; 2) l’effet du déséquilibre relatif au temps sur l’intention de départ est direct. Les résultats de l’étude, ainsi que les éventuelles pistes d’action sont discutés.The present study focuses on the determinants of withdrawal underlying the constant growth of the turnover rate among French volunteer firefighters. Only a few studies have examined work-life balance as a potential reason for withdrawal by volunteer firefighters who are all the more vulnerable to being exposed to an imbalance. The present study examines a model of withdrawal determinants in which work-life imbalance leads to exhaustion and lowers levels of satisfaction regarding firefighting, thus resulting in an increased intention to quit. The data were collected from 183 volunteer firefighters in a French fire department and were further processed via structural equation modelling of the relationship between latent variables. Our findings show that work-life imbalance (both strain- and time-based) predicts the French firefighters’ intention to leave their job, two forms of imbalance being predicted in different ways. The effect of strain-based imbalance on withdrawal intention is doubly mediated, first by exhaustion, and second by decreased satisfaction in the volunteering activity. The effect of time-based imbalance on the intention to quit is direct. The results as well as possible avenues for intervention are discussed.Given a constant growth of turnover rate in volunteer firefighters, current research focuses on withdrawal determinants. A few studies consider work-life balance as a potential reason for withdrawal in spite of the known risk of work-life imbalance in volunteer firefighter. The present study examines a model of withdrawal determinants, where work-life imbalance causes exhaustion and lowers levels of satisfaction in firefighting activity, thus resulting in higher levels of intention to quit. The data were collected from 183 volunteer firefighters of a French fire department and further processed via structural equation modelling in latent variables. Our findings show that work-life imbalance (both, strain and time-based) predict intention to leave in Frenh firefighters although in different ways for two forms of imbalance. The effect of strain-based imbalance onto turnover intention is double mediate, first by exhaustion, second, by satisfaction in volunteering activity. That of time-based imbalance onto turnover intention is direct. The results as well as further perspectives are discussed

Effecteurs moléculaires de lassociation Crassostrea gigas / Vibrio splendidus. Rôle de la porine OmpU dans les mécanismes de résistance et déchappement à la réponse immunitaire de lhôte.

Vibrio splendidus LGP32 est une bactérie pathogène associée aux épisodes de mortalités estivales qui affectent la production d'huître Crassostrea gigas depuis des décennies. Nous avons montré ici que la porine OmpU était un effecteur majeur de l'interaction V. splendidus / C. gigas. Nous avons pour cela construit un mutant ompU de V. splendidus. Celui-ci nous a permis de mo ntrer l'implication de OmpU (i) dans la résistance de V. splendidus aux antimicrobiens, incluant ceux de l'huître, (ii) dans la fitness chez l'huître, et (iii) dans la virulence en infections expérimentales (mortalités de 56 % pour le sauvage versus pour le 11% mutant). En accord avec ces résultats, nous avons montré que la délétion de ompU modifiait la sécrétion de protéines dont l'expression est contrôlée par les voies de régulation de la virulence (ToxR) et de l'intégrité membranaire (SigmaE). Par ailleurs, nous avons montré que OmpU jouait un rôle essentiel dans la reconnaissance par les hémocytes. En effet, (i) in vivo, les gènes hémocytaires répondent différemment à l'infection par le Vibrio sauvage ou ompU, et (ii) in vitro, OmpU est nécessaire à l'invasion hémocytaire par V. splendidus. Cette invasion utilise la phagocytose dépendante de l'intégrine b et la SOD extracellulaire du plasma d'huître comme opsonine qui lie OmpU. Ainsi, OmpU est un facteur de virulence majeur qui permet l'infection des hémocytes dans lesquels il est capable de survivre en inhibant la formation de radicaux oxygénés et de vacuoles acides. La résistance du Vibrio aux antimicrobiens hémocytaires de l'huître, elle-même dépendante de OmpU, est probablement un élément supplémentaire favorable à la survie intra-cellulaire.Vibrio splendidus LGP32 is a bacterial pathogen associated to the summer mortality outbreaks that have affected the production of Crassostrea gigas oysters over the past decades. We showed here that the OmpU porin is a major effector of the V. splendidus / C. gigas interaction. For that, we have constructed a ompU mutant of V. splendidus, and shown that the OmpU porin is implicated (i) in the resistance of V. splendidus to antimicrobials, including those of oyster, (ii) in its in vivo fitness, and (iii) in its virulence in oyster experimental infections (mortalities have been reduced from 56 % to 11 % upon mutation). In agreement, we have shown that the ompU deletion modified the expression of secreted proteins controlled by the virulence (ToxR) and the membrane integrity (SigmaE) regulation pathways. Furthermore, we have shown that OmpU has a major role in the recognition of V. splendidus by oyster hemocytes. Indeed, (i) in vivo, hemocyt e genes displayed differential responses to an infection with the wild-type or the ompU mutant, and (ii) in vitro, OmpU was necessary for hemocyte invasion by V. splendidus. This invasion process required the hemocyte b-integrin and the oyster plasma extracellular SOD, which was found to act as an opsonin recognizing OmpU. Thus, OmpU is a major virulence factor that allows infection of hemocytes in which V. splendidus is able to survive by inhibiting the production of reactive oxygen species and the formation of acidic vacuoles. Resistance of V. splendidus to hemocyte antimicrobials, which is also OmpU-dependant, is probably an additional determinant of V. splendidus intracellular survival.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Sub-Optimal Treatment of Bacterial Biofilms

Bacterial biofilm is an emerging clinical problem recognized in the treatment of infectious diseases within the last two decades. The appearance of microbial biofilm in clinical settings is steadily increasing due to several reasons including the increased use of quality of life-improving artificial devices. In contrast to infections caused by planktonic bacteria that respond relatively well to standard antibiotic therapy, biofilm-forming bacteria tend to cause chronic infections whereby infections persist despite seemingly adequate antibiotic therapy. This review briefly describes the responses of biofilm matrix components and biofilm-associated bacteria towards sub-lethal concentrations of antimicrobial agents, which may include the generation of genetic and phenotypic variabilities. Clinical implications of bacterial biofilms in relation to antibiotic treatments are also discussed

Rôle de la conciliation des sphères de vie dans la prédiction de l’intention de départ chez les sapeurs-pompiers volontaires français

International audienceAlors que l’on constate ces dernières années un taux de départ en constante augmentation chez les sapeurs-pompiers volontaires, différentes études voient le jour concernant ses antécédents. Cependant, encore peu semblent s’intéresser à l’impact de la conciliation des sphères de vie chez les volontaires d’autant plus susceptibles d’être exposés à un déséquilibre. La présente étude avait pour but de proposer un modèle de prédiction de l’intention de départ des sapeurs-pompiers-volontaires français, en articulant cette problématique avec celle de la conciliation des sphères de vie. Afin d’atteindre cet objectif, un recueil de données a été réalisé auprès de 183 sapeurs-pompiers volontaires d’un SDIS (Service départemental d’incendie et de secours) français. La modélisation en équations structurales en variables latentes a permis de confirmer que les déséquilibres des sphères de vie relatifs à la tension et au temps ont des effets surl’intention de départ du volontaire. Cet effet doit être différencié pour les deux formes de déséquilibre : 1) l’effet du déséquilibre relatif à la tension sur l’intention de départ est médiatisé d’abord par l’épuisement et ensuite par la satisfaction à l’égard de l’activité de sapeur-pompier volontaire ; 2) l’effet du déséquilibre relatif au temps sur l’intention de départ est direct. Les résultats de l’étude, ainsi que les éventuelles pistes d’action sont discutés