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• W2797782951 abstract "ResumeLe staphylocoque dore est un pathogene responsable d'une grande variete de maladies chez l'etre humain. Il est extremement bien equipe de facteurs de virulence, dont les adhesines. Jusqu'a present, 21 proteines liant des composants de tissus de l'hote (microbial surface components reacting with adherence matrix molecules, MSCRAMM) ont ete identifiees, par exemple le A (CIfA) ou la A (FnBPA). Neanmoins, pour la plupart de ces proteines, leur role dans la pathogenie des infections a staphylocoque dore reste a etre elucide. Le but de cette these est de contribuer a ce processus.Premierement, les MSCRAMM CIfA, CIfB, FnBPA, FnBPB, Cna, SpA, Pls, SdrC, SdrD, SdrE, SasD, SasE, SasF, SasG, Sasl, SasJ et SasK ont ete exprimes dans une bacterie substitut, Lactococcus lactis, et testes pour leurs proprietes adhesives et leur pathogenicite dans un modele d'endocardite experimentale (voir chapitre 1). Cette technique a prealablement ete utilisee avec succes et a l'avantage d'eviter le contexte complexe des redondances et systemes de regulations propres au staphylocoque dore. Les resultats montrent que, de tous les facteurs de virulence testes, seuls CIfA et FnBPA sont d'importance primordiale dans le developpement d'endocardite experimentale. En ce qui concerne l'internalisation dans les cellules endotheliales, seulement FnPBA et FnBPB en sont capables. En outre, l'adherence a chacun des ligands testes (fibrinogene, fibronectine, keratine, elastine, collagene, et les caillots de fibrine et plaquettes) est tres specifique et est mediee par une ou plusieures adhesines provenant du staphylocoque dore. Par consequence, ces proteines pourraient representer des cibles potentielles pour de futures therapies anti-adhesives contre le staphylocoque dore.Deuxiemement, l'expression des facteurs de virulence decrits dans le chapitre 1 par les souches recombinantes de lactocoques a ete verifiee par une nouvelle methode utilisant la spectrometrie de masse (voir chapitre 2). L'expression de toutes ces proteines par les souches recombinantes a pu etre confirmee. Cette methode pourrait etre de grande valeur dans la verification de la presence de proteines quelconques dans toutes sortes d'applications.Troisiemement, deux facteurs de virulence du staphylocoque, CIfA et une forme tronquee de FnBPA, ont ete exprimes de facon simultanee dans une souche recombinante de lactocoque (voir chapitre 3}. Contrairement a une souche exprimant la FnBPA entiere, une souche exprimant la forme tronquee de FnPBA, qui ne contient plus le domaine capable de lier le fibrinogene, perd completement sa capacite d'infecter dans le modele d'endocardite experimentale. Par contre, il est montre que, en cas de complementation de la forme tronquee de FnPBA avec le domaine de liaison au fibrinogene de CIfA dans la souche double recombinante, le phenotype integral de FnBPA est recupere. En consequence, les facteurs de virulence sont capables de cooperer dans le but de la pathogenie des infections a staphylocoque dore.SummaryStaphylococcus aureus is a human pathogen causing a wide variety of disease. It is extremely well equipped with both secreted and surface-attached virulence factors, which can act as adhesins to host tissues. In total, twenty-one microbial surface components reacting with adherence matrix molecules (MSCRAMMs) have been identified, so far. These include well-characterized adhesins such as clumping factor A (CIfA) or fibronectin-binding protein A (FnBPA). However, for most of them their potential role in the pathogenesis of staphylococcal infections remains to be elucidated. This has been attempted in this thesis work.Firstly, the staphylococcal MSCRAMMs CIfA, CIfB, FnBPA, FnBPB, Cna, SpA, Pls, SdrC, SdrD, SdrE, SasD, SasE, SasF, SasG, Sasl, SasJ, and SasK have been expressed in a surrogate bacterium, Lactococcus lactis, and tested for their in vitro adherence properties and their pathogenicity in the rat model of experimental endocarditis (see chapter 1). This model has successfully been used previously, and has the advantage of bypassing the complex S. aureus background of redundancies and differential regulation. Here, it is shown that of the seventeen tested potential virulence factors, only CIfA and FnBPA are critical for the pathogenesis of experimental endocarditis in rats, while internalization into bovine endothelial cells is mediated exclusively by FnBPA and FnBPB. In addition, the adherence to specific host ligands (fibrinogen, fibronectin, keratin, elastin, collagen, and fibrin-platelet clots) is highly specific and mediated by one or few staphylococcal adhesins, respectively. Thus, these surface proteins may represent potential targets for an anti-adhesive strategy against S. aureus infections.Secondly, the expression of the staphylococcal proteins by L. lactis recombinants described in chapter 1 was tested by a novel method using mass spectrometry (see chapter 2). The expression of all the staphylococcal proteins by the respective recombinant lactococcal strain could be confirmed. This method may prove to be of great value in the confirmation of the presence of any given protein in various experimental settings.Thirdly, two staphylococcal virulence factors, CIfA and a truncated form of FnBPA, were expressed simultaneously in one recombinant lactococcal strain (see chapter 3). In contrast to a recombinant strain expressing full-length FnPBA, a recombinant strain expressing a truncated FnPBA, lacking the domain capable of binding fibrinogen, completely lost infectivity in experimental endocarditis. However, it is shown that the complementation of the truncated form of FnBPA with the fibrinogenbinding domain of CIfA in a double recombinant strain results in the recovery of the complete phenotype of full-length FnBPA. Thus, virulence factors can cooperate in the pathogenesis of staphylococcal infections." @default.
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• W2797782951 date "2006-01-01" @default.
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• W2797782951 title "Role of Staphylococcus aureus surface proteins in experimental endocarditis" @default.
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