Les systèmes pathogènes complexes. modélisation et simulation

Dans la lignée des travaux des géographes sur les complexes pathogènes (M. Sorre, 1933) et les systèmes pathogènes (H. Picheral, 1983), nous présentons ici quelques exemples destinés à promouvoir le concept de système pathogène complexe. En effet, dans le vocabulaire des sciences de la complexité, les risques pour la santé résultent moins d’une succession d’évènements que d’une articulation complexe de facteurs (Daudé, Vaguet & Paul, 2015). Prenons l’épidémie de grippe de 2017..

Lactonase-mediated inhibition of quorum sensing largely alters phenotypes, proteome, and antimicrobial activities in Burkholderia thailandensis E264

IntroductionBurkholderia thailandensis is a study model for Burkholderia pseudomallei, a highly virulent pathogen, known to be the causative agent of melioidosis and a potential bioterrorism agent. These two bacteria use an (acyl-homoserine lactone) AHL-mediated quorum sensing (QS) system to regulate different behaviors including biofilm formation, secondary metabolite productions, and motility.MethodsUsing an enzyme-based quorum quenching (QQ) strategy, with the lactonase SsoPox having the best activity on B. thailandensis AHLs, we evaluated the importance of QS in B. thailandensis by combining proteomic and phenotypic analyses.ResultsWe demonstrated that QS disruption largely affects overall bacterial behavior including motility, proteolytic activity, and antimicrobial molecule production. We further showed that QQ treatment drastically decreases B. thailandensis bactericidal activity against two bacteria (Chromobacterium violaceum and Staphylococcus aureus), while a spectacular increase in antifungal activity was observed against fungi and yeast (Aspergillus niger, Fusarium graminearum and Saccharomyces cerevisiae).DiscussionThis study provides evidence that QS is of prime interest when it comes to understanding the virulence of Burkholderia species and developing alternative treatments

Widespread fear of dengue transmission but poor practices of dengue prevention : A study in the slums of Delhi, India

Background This study has been conducted to throw light on the knowledge and practices related to dengue fever among the poor population living in Delhi's slums. Materials A household survey was conducted in 2013 among 3,350 households. The households were stratified by a number of variables related to socio-economic status and health events such as hospitalisation. The data collection was completed through face-to-face interviews conducted with the help of 25 field investigators. Results About 8% of the households had at least one diagnosed dengue case. In comparison to the population surveyed, teenagers (15-19 years) and adults (30-34 years) were more affected whereas children under four years of age were underrepresented. Housewives are more affected by dengue (24%) compared to their share of the population surveyed (17%). Despite the fact that 77% of the respondents are worried about mosquitoes, only 43% of them monitor environment to avoid the presence of breeding sites. Conclusion One cannot exclude the possibility that though young children under the age of four years are exposed to the virus, either their cases were asymptomatic or family members infected during this period had potentially more serious symptoms leading to hospitalisation. This result could thus be explained by budget-related health choices made by this population which do not favour small children. Educational programs should target housewives to improve their impact, as they are the ones mostly responsible for water storage and cleanliness of the house and its neighbourhood. Even with a dengue experience and potentially an acute perception of the risk and its factors, a proper management of environmental conditions is lacking. This along with the fact that word-of-mouth is the main source of information quoted should be a message for municipality health workers to give door-to-door information on how to prevent breeding sites and dengue infection

Les systèmes pathogènes complexes. Modélisation et simulation

National audienceThe diversity of relations among factors that may trigger epidemics reveals the existence of complex pathogenic systems. As the search for mono-causality or linear causality became unproductive, deciphering this complexity is a major issue. To explore these old issues with a new point of view, we introduced the main concepts issued from complexity and agent-based models. We then illustrated this reflection about complex pathogenic system with dengue fever modelling

Multi-Agent Systems for Simulation in Geography: Moving Towards an Artificial Geography

International audienceRegularity and persistence expressed beyond contingency are the primary concern of a modeler. The geographer, particularly those specializing in spatial analysis and quantitative geography, might be familiar with this point of view: more than the specificity of individual behaviors, it is the general tendencies beyond the "noise" of this diversity which interests the modeler. These models often sum up and describe observations established by a given scale fairly well. They are nevertheless limited in their capacity to express the conditions for such phenomena appearing. Linking with local dynamics, complexity offers concepts and resources to link global descriptions and spatial analysis. Thinking in terms of complexity implies, among other things, conceiving observed phenomena at the level of numerous interactions which occur between elements operating at one or more lower levels. This position is not recent; it is formulated through systems theory [BER 68], which conceives systems as a collection of objects, of subsystems in interaction. However, system theory, at least in its non-adaptive and applicative form [FOR 80], is more concerned with the modalities of a system function and its behavior than with emergence conditions and their possible evolutions. Chapter written by Eric DAUDE

Les systèmes pathogènes complexes. Modélisation et simulation

National audienceThe diversity of relations among factors that may trigger epidemics reveals the existence of complex pathogenic systems. As the search for mono-causality or linear causality became unproductive, deciphering this complexity is a major issue. To explore these old issues with a new point of view, we introduced the main concepts issued from complexity and agent-based models. We then illustrated this reflection about complex pathogenic system with dengue fever modelling

Confiner la population en cas d’accident industriel avec effet toxique : de la doctrine à son application en zone urbaine

International audienc

ESCAPE-SG : Un simulateur d’évacuation massive de population pour la formation des acteurs à la gestion de crise

International audienc

Génération d'environnements artificiels pour la simulation spatiale d'arboviroses en milieu urbain : application à la dengue et au virus Zika

International audienceAedes aegypti is the main vector of dengue and Zika virus. Along with vaccine research, vector control is a major lever for fighting these diseases. Studying dynamical and non-linear relationships between the environment and vectors provides guidance for monitoring and control strategies. MODE's (Model of Dynamical Environement) objective is to identify environmental dynamics that contribute to the spatiotemporal distribution of Aedes aegypti in urban areas. This paper presents (1) the resource-based habitat concept and its application to Aedes aegypti, (2) the generic methods for estimating the environmental factor of this habitat and (3) the factors dynamics. These concepts and methods are illustrated in (4) with an application on Bangkok, Thailand. We conclude with a discussion on the contribution of environmental dynamics modelling for the study of arboviruses. MOTS-CLES : maladies à transmission vectorielle, resource-based habitat concept, biogéographie, simulation spatiale, SIG, télédétection, simulation à base d'agentsAedes aegypti est le principal vecteur de la dengue et du virus Zika. Avec la recherche vaccinale, le contrôle vectoriel est un levier important de lutte contre ces maladies. Étudier les relations dynamiques et non-linéaires entre l'environnement et le vecteur permet de guider les stratégies de surveillance et de contrôle. L'objectif de MODE (Model of Dynamical Environment) est d'identifier, par la simulation, les contextes environnementaux qui influencent la distribution spatiotemporelle d'Aedes aegypti en milieu urbain. Cet article présente (1) le concept d'un « habitat basé sur les ressources » et son adaptation à Aedes aegypti, (2) les méthodes génériques d'estimation des facteurs environnementaux de cet habitat et (3) les dynamiques de ces facteurs. Ces concepts et méthodes sont illustrés en (4) par une application sur Bangkok (Thaïlande). Nous concluons par une discussion sur l'apport d'une modélisation d'environnements dynamiques pour l'étude des arboviroses