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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Circulation des Chlamydiaceae en filières avicoles, exposition des professionnels et étude de la survie de Chlamydia psittaci / Circulation of Chlamydiaceae in poultry industries, worker exposure and study of the survival of Chlamydia psittaci

Hulin, Virginie 05 April 2016 (has links)
La chlamydiose aviaire, causée par la bactérie Chlamydia psittaci, représente un risque zoonotique important. L’infection chez l’animal est principalement asymptomatique, mais chez l’Homme elle peut entrainer des pneumopathies atypiques sévères et causer la mort dans les cas les plus graves. Les personnes infectées sont principalement celles exposées régulièrement à des oiseaux, particulièrement dans le cadre professionnel. En France, de nombreux cas humains sont liés à une exposition à des canards Mulard, espèce utilisée pour la production du foie gras. Afin d’évaluer la prévalence des Chlamydiaceae chez les volailles et de caractériser les souches circulantes, des suivis ont été réalisés à différents stades de l’élevage (couvoir, pré-gavage et gavage pour la filière canard, et abattoirs impliqués dans l’abattage de différentes espèces aviaires). Des prélèvements d’air et de poussières ainsi que des suivis sérologiques et biologiques de personnels volontaires ont été effectués en parallèle afin d’évaluer l’exposition des professionnels travaillant au contact des volailles. Des prélèvements environnementaux ainsi que des essais in vitro visant à étudier la survie de C. psittaci ont été réalisés afin de tenter de mieux caractériser les voies de contamination des oiseaux, ce qui pourrait, à terme, permettre de maitriser le risque de contamination par C. psittaci chez l’animal et donc de réduire l’exposition des professionnels. Les résultats ont démontré une prévalence importance de C. psittaci chez le canard Mulard, au contraire des autres volailles qui hébergent très majoritairement C. gallinacea. L’exposition des professionnels aux Chlamydia est réelle, tout au long du processus d’élevage des volailles, mais plus particulièrement en élevages de canards Mulard et à l’abattoir, aussi il convient pour les professionnels de se protéger à chaque contact avec les animaux. L’hypothèse d’une contamination environnementale des animaux se fait de plus en plus claire, avec notamment la mise en évidence d’un lien existant entre les procédures de nettoyage et désinfection et l’excrétion des canards, la description de la survie de C. psittaci en dehors de tout hôte vivant, ou encore la mise en évidence d’une possible survie de C. psittaci au sein d’A. castellanii. La mise au point de moyens de lutte efficaces permettant de réduire voire de supprimer l’excrétion chez les volailles est également nécessaire, dans le but de diminuer l’exposition des professionnels / Avian chlamydiosis is a factor of economic loss to the poultry industry as well as a risk for zoonotic transmission to human. Chlamydia psittaci is the primary avian chlamydial pathogen with zoonotic potential. Although being mainly asymptomatic in birds, it can cause a disease called “psittacosis” in humans, with severe atypical pneumonia that leads to death in the most severe cases. Persons affected are mainly those whose occupations put them at risk of exposure, and a number of recent reports in France have confirmed that most of the human cases seemed to be linked to poultry, especially mule ducks. Currently there is evidence suggesting that avian chlamydiosis in poultry involves a new chlamydial agent, namely C. gallinacea. In order to evaluate the presence of Chlamydiaceae in poultry and the exposure of workers, we conducted four studies in the poultry industries, in duck hatchery, breeding farms and slauhgterhouse, as well as a studie in two poultry slaughterhouses including samples from voluntary workers. Results showed an important asymptomatic carriage of C. psittaci by mule ducks and a real, invisible and unpredictable exposure of workers. The species C. gallinacea was really prevalent in poultry othe than ducks and we still ignore its impact on human. Contamination of animals on farm seems to be mainly made via the environment. In vitro studies have been done to examine the survival of C. psittaci as a function of temperature in a non-nutritiv middle and showed that viable bacteria were still detectable after two months. Finally, the possible interactions between C. psittaci and an amoeba, Acanthamoeba castellanii, were studied and seem to show that the bacteria was able to enter the amoeba but we still ignore if it can survive or not
2

<em>Chlamydia pneumoniae</em> infection, inflammation and heat shock protein 60 immunity in asthma and coronary heart disease

Sävykoski née Huittinen, T. (Tiina) 26 April 2003 (has links)
Abstract Chlamydia pneumoniae is a common respiratory pathogen worldwide. It does not only cause acute respiratory infections, but is also associated with chronic inflammatory diseases, such as asthma and coronary heart disease (CHD). Chlamydial heat shock protein 60 (Hsp60) is associated with the development of immunopathological damage following C. trachomatis infections, but the role of Hsp60 in C. pneumoniae infections is unclear. A slightly elevated level of C-reactive protein (CRP), as a marker of systemic inflammation, predicts cardiovascular events, but its role in asthma has not been studied. The aim of this study was to develop an EIA method for the measurement of Hsp60 antibodies and for studying the host immune responses to C. pneumoniae and chlamydial and human Hsp60 proteins, CRP levels and their interactions in asthma and CHD. Elevated levels of serum IgA antibodies to the Hsp60 protein of C. pneumoniae were associated with asthma and decreased pulmonary function. CRP levels were also higher in the asthma patients than in the controls. The patients with moderate asthma had higher CRP levels than those with mild asthma. The patients with a CRP level over 2 mg/l had higher levels of serum IgA antibodies to C. pneumoniae and chlamydial Hsp60 than the patients with lower CRP levels. A prospective nested case-control study was carried out, to study the role of Hsp60 antibodies as coronary risk predictors, and their association with C. pneumoniae infection and inflammation. The participants were obtained from the Helsinki Heart Study: 241 myocardial infarctions or coronary deaths occurred during the 8.5-year period among dyslipidemic middle-aged men. An elevated level of human Hsp60 IgA antibodies in baseline serum predicted the occurrence of a coronary event several years later, especially when present simultaneously with a high C. pneumoniae IgA antibody level and an elevated CRP level. Further studies showed that only persistently, not transiently, elevated levels predicted coronary events. The risk associated with elevated antibody levels increased markedly in the presence of an elevated CRP level, and vice versa. In conclusion, these results suggest that chlamydial Hsp60 is involved in the association between C. pneumoniae infection and asthma, while autoimmunity to human Hsp60 is implicated in the association between C. pneumoniae infection and CHD. Inflammation evidently plays an important role in these associations. It can also be concluded that IgA antibodies, compared to IgG antibodies, against C. pneumoniae and Hsp60 are better markers of chronicity, especially when they are persistently elevated.
3

Chlamydia Persistence - a Tool to Dissect Chlamydia-Host Interactions

Schoborg, R. V. 01 January 2011 (has links)
Under stress, chlamydiae can enter a non-infectious but viable state termed persistence. In the absence of a tractable genetic system, persistence induction provides an important experimental tool with which to study these fascinating organisms. This review will discuss examples of: i) persistence studies that have illuminated critical chlamydiae/host interactions; and ii) novel persistence models that will do so in the future.
4

Nouvelles stratégies d'isolement et de caractérisation des microorganismes intracellulaires associés aux amibes / New strategies for the isolation and characterization of amoeba associated microorganisms

Bou Khalil, Yaacoub Jacques 16 June 2016 (has links)
La co-culture d’amibes est utilisée afin d’isoler des microorganismes. Ainsi le premier virus géant,fut découvert. Cependant, les méthodes de culture sur protozoaires sont délicates et fastidieuses. De ce fait, le développement de ces cultures représente une difficulté pour les microbiologistes, limitant ainsi l’analyse d’un nombre important d’échantillons et la caractérisation de nouveaux virus. De nouvelles stratégies et des améliorations des modèles actuels sont donc nécessaires. Notre travail a été de développer de nouvelles stratégies permettant l’isolement de microorganismes associés aux amibes. Dans la 1ere partie nos travaux ont permis une amélioration des cultures avec le développement de nouveaux milieux de culture et l’utilisation ciblée d’antimicrobiens.La clé de ces stratégies est l’association des techniques rapides aux étapes améliorées de culture et leur application à un large panel de protozoaires pouvant abriter des microorganismes. Les résultats ont permis le développement d’un système d’isolement à haut débit très efficace. Nous avons notamment mis au point des techniques de tri de virus géants par cytométrie.Dans la seconde partie, nos travaux ont porté sur la description et la caractérisation des nouveaux isolats.Les résultats obtenus démontrent l’importance de poursuivre l’isolement et la caractérisation de ces microorganismes afin de mieux appréhender l’évolution de ces microorganismes, leur biotope et leur pathogénicité.De nouveaux outils sont nécessaires,notre manque d’imagination et l’absence de systèmes automatisés seront les limites aux nouvelles stratégies dans le monde de la microbiologie. / Amoebae are predators without distinction and they can also act as hosts to several different microorganisms that may coexist simultaneously. Some protozoa are sources of human pathogens where they act as reservoir of any human pathogens like Legionellae, Chlamydiaceae and others. In addition, the first giant virus, Acanthamoeba Polyphaga imivirus, was discovered using Amoeba as cell host. Since then, many other giant viruses have been isolated. For decades, amoebae were used as cell hosts in the culture- based process to isolate microorganisms, and allowed to recover new giant viruses and bacterial species from human and environmental samples. In contrast the co-culture system with protozoa is tedious and fastidious. Microbiologists are limited to routine culture methods, limiting by this the speed of screening potential samples and the efficiency of yielding new isolates. Much effort and improvement were needed. Our work consisted in the development of new strategies and techniques for the isolation of new microorganisms associated to protozoa. In the first part of this work, we described, all the improvements we brought to the protists culture system for the isolation of intracellular microorganisms especially giant viruses and Chlamydiaceae. Major improvements were based on modified culture enrichment steps, adapted culture media, and targeted use of specific drugs. The key of this new strategy was the implementation of high-throughput technologies to the ameliorated culture based systems, and the application of this later to a wide panel of protozoa used as potential host cells. These presented advances and strategies demonstrated significant time saving, and higher sensitivity than older techniques, they considerably increased the potential of collecting new environmental or clinical isolates and also new undiscovered microorganisms especially new giant virus familiesand particular Chlamydiaceae associated to amoebae. We continued to ameliorate the efficiency of the flow cytometric technology by reviewing its contributions to the virology field, then by applying it to the isolation system by sorting the new isolates as a new strategy for better genomic and proteomic analysis. In the second part of this work, we focused on the characterization of new isolates at the level of developmental cycle and genomic description. We used electron microscopy, and genome sequencing as main tools to describe our newly isolated giant viruses but also report new species of Chlamydiaceae and managed to decipher Chlamydiaceae species with a host dependent replication cycle, an issue that has not, thus far, been observed in protozoa-associated Chlamydiaceae. The strategies and results described herein show the importance of pursuing the isolation of new associatedamoebal microorganisms in order to give rise to new insights into the evolution of these microorganisms, their respective biotopes, and their potential or hidden pathogenicity. The more we need to search the more tools are needed, only our lack of imagination and appropriate automated systems will put limits on any needed strategy in the field of microbiology.

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