Auswahl der wissenschaftlichen Literatur zum Thema „Streptocoques – Génétique“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Inhaltsverzeichnis
Machen Sie sich mit den Listen der aktuellen Artikel, Bücher, Dissertationen, Berichten und anderer wissenschaftlichen Quellen zum Thema "Streptocoques – Génétique" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Dissertationen zum Thema "Streptocoques – Génétique"
Garnier, Fabien. „Identification au niveau de l'espèce de streptocoques du groupe viridans par PCR“. Paris 5, 1996. http://www.theses.fr/1996PA05P164.
Der volle Inhalt der QuelleMartins, Mariana. „Interaction of Streptococcus gallolyticus with human colonic cells“. Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC134.
Der volle Inhalt der QuelleThe Gram-positive bacterium Streptococcus gallolyticus is an emerging cause of bacteremia and infective endocarditis in the elderly. Several epidemiological studies point to a high incidence of gastrointestinal pathologies in patients infected with S. Gallolyticus. Thus, the presence of this bacterium is strongly associated with colorectal cancer (CRC). However, it remains unknown whether S. Gallolyticus infection is a cause or consequence of CRC development. The main goal of this PhD project was to explore the interactions of S. Gallolyticus with human colonic cells, in order to get molecular insights explaining the association of this bacterium with CRC. In the first part of this work, we have characterized the role of S. Gallolyticus Pil3 pilus in binding to intestinal mucins MUCSAC and MUC2, adhesion to human colonic cells producing mucus HT29-MTX and colonization of the murine colon. In the second part, we took advantage of permeable support systems (transwell), which mimic a polarized epithelial barrier, to demonstrate the capacity of S. Gallolyticus UCN34 to actively translocate across colonic barriers, a critical trait for the establishment of invasive infection. Interestingly, we found that the PiI3 pilus, in particular the Pil3A adhesin, expressed heterogeneously at the single tell level (90% of Pil3low and 10% of Pil3high) in S. Gallolyticus UCN34 was crucial for bacterial translocation across the epithelium. Pil3high bacteria probably interact with an unknown host receptor, allowing the transient opening of the tight junctions and the passage of Pil3low bacteria. Indeed, PiI3 overexpressing bacteria or Δpil3 bacteria were unable to translocate intestinal monolayers in vitro. Altogether, our work provided novel insights on the key role of the S. Gallolyticus PiI3 pilus in host colon colonization via interaction with mucins. In addition, the heterogeneous expression of PiI3 was shown to be crucial for the paracellular passage of S. Gallolyticus between adjaçent cells
Achard, Adeline. „Bases biochimiques et génétiques de la résistance aux macrolides et antibiotiques apparentés chez Streptococcus agalactiae et Streptococcus uberis“. Caen, 2007. http://www.theses.fr/2007CAEN2007.
Der volle Inhalt der QuelleThe therapeutic use of macrolides and related antibiotics (MLS ) has led to the emergence of resistant bacteria. Resistance of streptococci to these antibiotics is alarming, because of their wide use in human and veterinary environments. In this study, we report the emergence of MLS resistance by inactivation in two species of Streptococcus: Streptococcus agalactiae and Streptococcus uberis. A human isolate of S. Agalactiae was shown to inactivate lincosamide whereas an animal isolate of S. Uberis, inactivated spiramycin (a 16- membered ring macrolide). The lincosamide resistance was due to a nucleotidyltransferase encoded by a new lnu(C) gene. The gene was localized on a mobilizable transposon, MTnLnu in S. Agalactiae UCN36, and on a transferable plasmid in the veterinary strain S. Uberis 88. MTnLnu is the first mobilizable transposon reported in streptococci and could be mobilized by the conjugative transposon Tn916. The spiramycin resistance of the veterinary strain S. Uberis 74 was related to the presence of a rdmC-like and the mph(B) genes. These genes encoded an enzyme belonging to the alpha/beta hydrolases family and a phosphotransferase known to inactivate 14, 15 and 16-membered macrolides in E. Coli, respectively. Preliminary results suggested a combined action of these two enzymes on spiramycin
Weyder, Mathias. „Evolution et modélisation de processus biologiques : application à la régulation de la compétence naturelle pour la transformation génétique bactérienne chez les streptocoques“. Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30021/document.
Der volle Inhalt der QuelleBacteria have evolved many types of genetically induced mechanisms to face different types of stresses and to adapt to new environments. Competence for natural transformation is one such process that promotes horizontal gene transfer. If phylogenetically distant species share conserved uptake and processing apparatus, competence regulatory circuits are not universal but adapted to every species' lifestyle. In Gram-positive bacteria, Streptococcus pneumoniae and Bacillus subtilis regulatory cascades are the best documented. If many mathematical models have been established to study different aspects of competence regulation in B. subtilis, only one population-scaled model has been developed for S. pneumoniae, a decade ago, based on hypotheses that are challenged by new experimental data. We develop, in S. pneumoniae, a knowledge-based model of the competence regulation at cell level that integrates the enriched biological knowledge acquired to date. The structural consistency of the network topology is confirmed using Petri net formalism. The network is further turned into a set of ordinary differential equations to study its dynamics behavior. Protein kinetics are estimated using time-series luminescence data and other parameter estimations are constrained according to available knowledge. We point out some gap in competence shut-off knowledge, and, after testing alternative models, we predict the requirement of a yet unknown late com gene product inhibiting the action of ComW, the ?x factor activator. We also bring new insights into this regulatory cascade by predicting the system components that might be involved in specific experimental behavior. Our model consolidates the experimental knowledge acquired on competence regulation in S. pneumoniae. Moreover, it can be applied to the other streptococci species belonging to the mitis and anginosus groups since they shared the same regulatory circuit. In the population, the competence shift happens first in a subpopulation of cells and spreads into the whole population through cell to cell contact. Allowing simulation of individual cell behavior, our model will provide a brick for the design of a population-scale model composed of heterogeneous cells
Coluzzi, Charles. „L'exploration des génomes par l'outil ICEFinder révèle la forte prévalence et l'extrême diversité des ICE et des IME de streptocoques“. Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0352/document.
Der volle Inhalt der QuelleMobile genetic elements largely contribute to the evolution and diversity of bacterial genomes through horizontal gene transfer. Among them, the integrative and conjugative elements (ICEs) encode their own excision, conjugative transfer and integration. On the other hand, integrative mobilizable elements (IMEs) are autonomous for excision and integration but encode only some of the proteins needed for their conjugative transfer. IMEs therefore need a “helper” conjugative element to transfer. Despite their impact on gene flow and genome dynamics, the prevalence of ICEs remains largely underscored and very few IMEs were identified at the beginning of this study. Furthermore, although several in silico methods exist to detect genomic islands, none are dedicated to ICEs or IMEs, thus complicating exhaustive examination of these mobile elements. The Streptococcus genus belongs to the firmicutes’ phylum. Almost all streptococci are commensal bacteria or pathogenes to men and animals. Two species of Streptococcus are also used in the dairy industry as lactic ferments in order to produce fermented milk and different types of cheese. Studying the gene flux of the Steptococci genus and the impact it can have on the lifestyle of these organisms is essential, as it has a lot of interest for human health and activities. In this work, we searched for ICEs and IMEs in 124 strains of streptococci belonging to 27 species using a reference database of ICE and IME signature proteins (from their conjugation, mobilization and integration/excision modules). This exhaustive analysis led to the identification and delimitation of 131 ICEs or slightly decayed ICEs and 144 IMEs. All these elements were delimited, which allowed us to identify their integration specificities in the genomes. In total, 17 ICE integration specificities were identified. Among them, 8 had never been described before (ftsK, guaA, lysS, mutT, rpmG, rpsI, traG and ybaB/EbfC). 18 specificities were also identified for IMEs, among which only 5 were known for the firmicutes. ICEs encode high or low-specificity tyrosine integrases (13 different specificities), single serine intégrases (1 specificity), triplet of serine integrases (3 different specificities), or DDE transposases while IMEs encode either tyrosine integrases (10 different specificities) or single serine integrases (8 different specificities). ICE were grouped in 7 distinct families according to the proteins encoded by their conjugation module whereas the mobilization modules of IMEs were highly diverse, preventing them from grouping into families according to their mobilization modules. The phylogenetic analysis of the signature proteins encoded by all ICEs and IMEs showed integration module exchanges between ICEs and IMEs and several mobilization module exchanges between IMEs. The overall results reveal a strong prevalence and extreme diversity of these elements among Streptococci genomes. Better understanding and knowledge of ICEs and IMEs prompted us to build a semi-automated command-line tool to identify streptococcal ICEs and IMEs as well as to determine their insertion site
Dechêne-Tempier, Manon. „Mobilisation de gènes d'antibiorésistance chez Streptococcus suis par conjugaison“. Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0234.
Der volle Inhalt der QuelleThe increase in bacterial resistance to antibiotics is a major public health issue. This phenomenon is part of the "One Health" approach, which interconnects human, animal and environmental health. In this context, the study of Streptococcus suis, an animal pathogenic and zoonotic bacterium with a high rate of resistance to certain antibiotics, is particularly relevant. Indeed, certain serotypes are regularly responsible for fatal epidemics in Asia. In Europe, S. suis causes major economic losses on pig farms and sporadic human infections. Analysis of North American and Asian strains has revealed that the genes involved in antibiotic resistance are located on mobile genetic elements (MGEs), particularly on ICEs and IMEs, which are integrated into the host bacterial genome but, after excision, can be transferred via a conjugation pore. ICEs are autonomous and can act as "helper" elements by transferring non-autonomous elements: IME. The presence of antibiotic resistance genes on such elements represents a major risk of propagation, but these EGMs are still under-researched due to their complex identification. In France, antibiotic resistance in bacteria isolated from sick animals (including S. suis in pigs) is monitored by the Résapath network. To complement these data, the aim of my thesis was to determine the level of antibiotic resistance within a more diversified collection of S. suis strains, to study the genomic location of the genes responsible for this resistance and thus assess the risk of dissemination. Our approach was to: (1) compile a collection of 200 strains representative of those present in mainland France, according to their : serotypes, sites of isolation, enabling us to define three pathotypes (pathogenic, non-clinical and respiratory), period of isolation (before or after the EcoAntibio plan), host (pigs, humans, wild boar) and geographical regions of isolation (half in Brittany, a region with a high density of livestock); (2) perform antibiograms of strains against 22 antibiotics used in veterinary and/or human medicine; (3) sequence 102 selected strains according to their resistance profiles; (4) assemble and annotate genomes, then locate antibiotic resistance, virulence and competence genes, as well as ICEs and IMEs. Our analyses showed that 86% of strains were resistant to at least one antibiotic, with a low rate of resistance to fluoroquinolones, penicillins, pleuromutilin and diaminopyrimidine-sulfonamides, and a very high rate for macrolides-lincosamides and tetracycline. Multidrug resistance profiles were observed in 138 strains, in line with European data. The search for antibiotic resistance genes in S. suis genomes revealed a decrease in their frequency in strains isolated after the EcoAntibio Plan, and a statistically higher number of antibiotic resistance genes in non-clinical strains. What's more, most of these genes (n=217) are located on ICE/IMEs. More than half the strains carry an EMI containing tetracycline and macrolide-lincosamide resistance genes, inserted in a Tn5252 ICE family. Thus, S. suis probably has a high potential for spreading antibiotic resistance genes. Penicillin resistance accounted for 5% of the collection analyzed. Any spread of this resistance would be a cause for concern, given the importance of β-lactamines in the treatment of S. suis infections in both veterinary and human medicine. Our results are complementary to those of the Résapath network, and demonstrate the value of studying strains of serotypes less frequently implicated in pathological cases or carriage strains, in order to improve monitoring of antibiotic resistance in France
Szili, Noémi Réka. „Biosynthesis, role(s) and regulation of the PI-2b pilus in the hypervirulent ST-17 clone of Streptococcus agalactiae“. Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC062/document.
Der volle Inhalt der QuelleStreptococcus agalactiae (also known as Group B Streptococcus, GBS) is an opportunistic Gram-positive pathogen responsible for severe invasive infections, especially in neonates. GBS strains belonging to the ST-17 sequence type are responsible for 80% of late-onset neonatal meningitis. Genomic comparison of ST-17 strains to non-ST-17 GBS isolates revealed a few surface proteins that are characteristic of ST-17 clone, such as HvgA and Srr2, which contribute to colonization and dissemination. Similarly, the PI-2b type pilus is conserved in ST-17 strains and the main goal of this PhD project was to decipher the role of this pilus in the physiopathology of ST-17 strains. In the first part of this work, we compared the expression of the PI-2b pilus in our ST-17 representative strain BM110, and a non-ST-17 human clinical isolate, A909. We showed that PI-2b expression, although variable, was lower in ST-17 isolates as compared to non ST17 isolates. In the representative strain BM110, we demonstrated that the lower expression was be due to the presence of a 43-base pair (bp) hairpin-like structure in the upstream region of PI-2b, preventing read-through transcription from upstream antigen B (AgB) operon. Furthermore, gene reporter assays to characterize the Ppi-2b promoter region revealed the requirement of an extended 5’ region and of GBS-specific regulatory factors to drive PI-2b transcription. PI-2b transcription was shown to be maximal at 37 °C. Collectively our results suggest a complex regulation of PI-2b expression in ST-17 clinical isolates, that may confer a selective advantage in the human host either by reducing host immune responses and/or increasing their dissemination potential.In the second part of this work, we sought to investigate the role of the putative adhesin AP1-2b, and the two accessory genes lep and orf in the biosynthesis of PI-2b pilus. We showed that both orf and lep are important for PI-2b expression. Our results suggest that Lep is a functional signal peptidase involved in the optimal processing of the major PI-2b pilin. The role of orf remains to be uncovered
Bentorcha, Faïrouze. „Identification de gènes de résistance et d'éléments génétiques mobiles chez les entérocoques“. Université de Paris-Sud. Faculté de pharmacie (Châtenay-Malabry, Hauts-de-Seine), 1993. http://www.theses.fr/1993PA114802.
Der volle Inhalt der QuelleFleuchot, Betty. „Les régulateurs transcriptionnels Rgg. Confirmation de leur implication dans des phénomènes de quorum-sensing et identification de leurs cibles“. Phd thesis, AgroParisTech, 2011. http://pastel.archives-ouvertes.fr/pastel-00782705.
Der volle Inhalt der QuelleBeauruelle, Clémence. „Locus CRISPR de Streptococcus agalactiae : marqueur génétique de la phylogénie de l'espèce et de l'évolution récente des isolats“. Electronic Thesis or Diss., Tours, 2019. http://www.theses.fr/2019TOUR3806.
Der volle Inhalt der QuelleWe studied the relevance of the CRISPR1 array (associated to a CRISPR-Cas II-A type) as an epidemiological marker for genotyping and phylogenetic analyses of Streptococcus agalactiae (or Group B Streptococcus (GBS)) isolates. We demonstrate that i) spacer acquisition events occurred in vivo which strongly suggest that the CRISPR1-Cas system is functionally active for adaptation ii) ancestral markers (TDR and ancestral spacers) are highly conserved and reflect the phylogenetic structure of the GBS population (in congruence with MLST) iii) CRISPR1 array shared a high degree of polymorphism (especially for leader end spacers) offering a highly discriminatory typing method (allow to separate isolates within a same ST defined by MLST). Leader end analysis also provides specific evidence on isolates recent evolution, especially encounters with MGEs. CRISPR1 array appears as a useful genetic feature to follow vaginal carriage of GBS in women and for evaluate the diversity of GBS vaginal carriage population. On the basis of these data, we assume that this method could pretend to be a reference method for phylogenetic GBS typing