No description available.

In immunodeficient patients, for example with cystic fibrosis (CF), the opportunistic pathogen Staphylococcus aureus causes chronic infections of respiratory tract that are treated with antibiotics (ATB) in the long term. However, exposure to antibiotics can lead to persistence, thereby result a recurrence of infection. The aim of this work was to examine in selected pairs of S. aureus chronological isolates from the respiratory tract of CF patients how their ability to form persisters is changing in time. I have found that the ability to persist within the clonal pair does not change significantly after two years of survival in the host, and that the ability to persist depends on the adaptative mutations of the isolates. Persister formation may depend on mutations in operon of the alternative sigma B factor (sigB) and the major virulence gene regulator (agr). By dual staining with DioC2(3) and To-pro-3, I was able to determine the changes in membrane potential and membrane permeability during the killing curve with ATBs. The distribution into subpopulations according to these parameters depends primarily on the antibiotic used. I conclude that various antibiotics can induce different mechanisms causing a persistent state. Futhermore, I have constructed plasmids with a labeled promoter to determine...

In immunodeficient patients, for example with cystic fibrosis (CF), the opportunistic pathogen Staphylococcus aureus causes chronic infections of respiratory tract that are treated with antibiotics (ATB) in the long term. However, exposure to antibiotics can lead to persistence, thereby result a recurrence of infection. The aim of this work was to examine in selected pairs of S. aureus chronological isolates from the respiratory tract of CF patients how their ability to form persisters is changing in time. I have found that the ability to persist within the clonal pair does not change significantly after two years of survival in the host, and that the ability to persist depends on the adaptative mutations of the isolates. Persister formation may depend on mutations in operon of the alternative sigma B factor (sigB) and the major virulence gene regulator (agr). By dual staining with DioC2(3) and To-pro-3, I was able to determine the changes in membrane potential and membrane permeability during the killing curve with ATBs. The distribution into subpopulations according to these parameters depends primarily on the antibiotic used. I conclude that various antibiotics can induce different mechanisms causing a persistent state. Futhermore, I have constructed plasmids with a labeled promoter to determine...

Staphylococcus aureus is human pathogen and is causative factor of many diseases with different character, from light infections of the skin to life-threatening sepsis. S. aureus often colonizes cystic fibrosis patient's lungs and causes long-standing pneumonia, which can cause death in these patients. Infection caused by S. aureus are, as most of the infections, treated with antibiotics. Failure in treatment is caused because of presence of resistant strains. It was shown, that treatment failure can be caused by different type of the antibiotic tolerance - by the persistence. Persisters are phenotypic variants of isogenic bacterial population, that is unaffected by antibiotic treatment even though they don't have genetics determinants of the resistance. The phenomenon of the persistence in bacteria is still relatively poorly understood. The aim of my thesis was to contribute to the characterization of the persistence in S. aureus. We have optimized a method for rapid identification of persisters' amount in the bacterial population after treatment with antibiotics using the method of measuring the killing curves. We have found out, that exposure to osmotic stress causes increase in number of persistence in the bacterial population by 1 - 2,5 order. Using quantitative PCR method we have analyzed the...

In clinical practice, infections caused by persistent bacteria have become a worldwide problem. We are talking about a subpopulation of cells that are able to withstand lethal doses of antibiotics and after their elimination are capable of resuscitation and re-induction of the disease. The opportunistic pathogen Staphylococcus aureus is one of this bacteria and causes various serious chronic infections. During the long-term persistence in patients, persistent bacteria acquire adaptive mutations. The aim of this diploma thesis was to monitor the degree of persistence in selected clinical isolates, and at the same time to demonstrate the effect of adaptive mutations on the degree of persistence as well as to molecularly characterize the persistent state by gene expression. I had chronological isolates of S. aureus at my disposal, the initial one being the primoisolate, an isolate taken at the diagnostics of cystic fibrosis before the start of antibiotic treatment. Another was taken at a distance of one year and the last with a half-year interval from the previous one. Following whole genome sequencing, genes in which adaptive mutations occurred were identified. The first method determines the degree of persistence by calculating CFU (Colony Forming Units) after antibiotic treatment. I found that this...

Le catalogue occupe une place privilégiée dans l'offre de service des bibliothèques universitaires, pivot de l'intermédiation. Depuis 10 ans, il traverse une crise grave, voyant les usagers le délaisser à la faveur des moteurs de recherche généralistes. Le web, plus qu'un sérieux concurrent, devance aujourd'hui les systèmes d'information documentaires, et devient le point d'entrée principal pour la recherche d'information. Les bibliothèques tentent de structurer un espace documentaire qui soit habité par les usagers, au sein duquel se développe l'offre de service, mais celle-ci se présente encore comme une série de silos inertes, sans grande possibilité de navigation, malgré de considérables efforts d'ingénierie et des pistes d'évolution vers les outils de découverte. La profession, consciente de cette crise profonde, après avoir accusé les remous occasionnés par la dimension disruptive du numérique, cherche des moyens pour adapter et diversifier son offre, fluidifier la diffusion de l'information, et se réinvente un rôle d'intermédiation en cherchant à tirer profit des nouvelles pratiques des usagers, de leurs nouvelles attentes, et de nouvelles perspectives. Les bibliothèques placent leur espoir dans de nouveaux modèles de données, tentent d'y ajouter un niveau d'abstraction favorisant les liaisons avec l'univers de la connaissance. L'évolution vers le web sémantique semble une opportunité à saisir pour valoriser les collections et les rendre exploitables dans un autre contexte, au prix d'importants efforts que cette analyse tente de mesurer. Une approche constructiviste fondée sur l'observation participante et le recueil de données offre une vision issue de l'intérieur de la communauté des bibliothèques sur l'évolution des catalogues et des outils d'intermédiation, et ouvre des perspectives sur leurs enjeux.

Le catalogue occupe une place privilégiée dans l’offre de service des bibliothèques universitaires, pivot de l’intermédiation. Depuis 10 ans, il traverse une crise grave, voyant les usagers le délaisser à la faveur des moteurs de recherche généralistes. Le web, plus qu’un sérieux concurrent, devance aujourd’hui les systèmes d’information documentaires, et devient le point d’entrée principal pour la recherche d’information. Les bibliothèques tentent de structurer un espace documentaire qui soit habité par les usagers, au sein duquel se développe l’offre de service, mais celle-ci se présente encore comme une série de silos inertes, sans grande possibilité de navigation, malgré de considérables efforts d’ingénierie et des pistes d’évolution vers les outils de découverte. La profession, consciente de cette crise profonde, après avoir accusé les remous occasionnés par la dimension disruptive du numérique, cherche des moyens pour adapter et diversifier son offre, fluidifier la diffusion de l’information, et se réinvente un rôle d’intermédiation en cherchant à tirer profit des nouvelles pratiques des usagers, de leurs nouvelles attentes, et de nouvelles perspectives. Les bibliothèques placent leur espoir dans de nouveaux modèles de données, tentent d’y ajouter un niveau d’abstraction favorisant les liaisons avec l’univers de la connaissance. L’évolution vers le web sémantique semble une opportunité à saisir pour valoriser les collections et les rendre exploitables dans un autre contexte, au prix d’importants efforts que cette analyse tente de mesurer. Une approche constructiviste fondée sur l’observation participante et le recueil de données offre une vision issue de l’intérieur de la communauté des bibliothèques sur l’évolution des catalogues et des outils d’intermédiation, et ouvre des perspectives sur leurs enjeux. / The catalog takes up a special position in the supply of services of academic libraries, as a pivot for the intermediary between users and information professionals who carry the responsibility for building up collections. For 10 years, through a serious crisis, they’ve been seeing their patrons preferring the general or commercial search engines. The Web is more than a serious competitor today, ahead of the document information systems, and became the main access point for information retrieval. Libraries are trying to structure an information space that is temporarily or permanently inhabited by users, in which the service offering is developed, but it is still presented as a series of silos, with few opportunities of navigation between them despite considerable engineering efforts and a perspective of evolution towards discovery tools. The profession, having become aware of this deep crisis after accusing eddies caused by the breakdown of the digital switch, looking for ways to adapt and diversify its offering, streamlines the dissemination of information, and reinvents its roles, trying to take advantage of new practices of users, new expectations and new prospects. Libraries put their hope in new data models, trying to add a level of abstraction promoting links with the world of knowledge. The evolution towards the Semantic Web seems to be a valuable opportunity to enhance the collections and make them usable in another context, at the expense of significant efforts sized up by this analysis. A constructivist approach based on participant observation and data collection offers a vision of the outcome within the library community on the development of catalogs and intermediation tools, and an outlook on their issues.