Tesi sul tema "Interactions hôte-Microbiote"
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Dumas, Alexia. "Rôle du microbiote dans les interactions hôte-pathogène dans la tuberculose". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30338.
Testo completoThe microbiota refers to all microorganisms (bacteria, viruses, fungi) living in a specific environment, especially in a host (human, animal or plant). The symbiotic relationship existing between the microbiota and its host has been demonstrated in many contexts. In particular, it is now well-established that the microbiota plays a protective role during different human pathologies, including bacterial infections. The microbiota colonizes all the mucosal membranes of the body; particularly the intestine where it is more abundant. While role of the gut microbiota has already been widely studied, the existence of bacteria in the lungs has been described more recently. Even if at first controversial, the existence of a pulmonary microbiota, whose composition is distinct from that of the intestine, and which can be altered in pathological conditions, is now well established. It is also well-established that the microbiota of an organ can act on the physiology of other organs; for instance, a "gut-lungs" axis is used to designate the action of soluble compounds produced by the intestinal microbiota, as well as immunes cells or cytokines from the gut, carried by the blood or the lymph, on the physiology of the lung. The lungs are one of the major colonization site for different pathogens. Tuberculosis (TB), a chronic pulmonary inflammation caused by the bacteria Mycobacterium tuberculosis, is still today the most lethal respiratory disease due to a single etiological agent. To date, the complexity of the mechanisms explaining the difference in susceptibility to TB between individuals has not been fully understood yet. It has been suggested that the balance between virulence of the strain of M. [...]
Oyanedel, Trigo Daniel. "Bases moléculaires et cellulaires des interactions Vibrios Crassostrea gigas en contexte sain et pathologique". Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTG032.
Testo completoBacteria of the genus Vibrio are ubiquitous in aquatic environments. They adopt free and associated lifestyles. They establish mutualistic, commensal and parasitic symbioses with numerous metazoa. In the healthy Crassostrea gigas oyster, an abundant and diverse microbiota that includes many Vibrio is maintained under immune homeostasis. However, under the influence of biotic or abiotic stressors a dysbiosis is created favoring the proliferation of opportunistic Vibrio species, which can induce the death of oysters. This occurs during the Pacific Oyster Mortality Syndrome (POMS), which is caused by an immunosuppressive virus, OsHV-1 µvar. We have here characterized the Vibrio / C. gigas interactions in health and disease. We show that in populations of V. splendidus associated with healthy oysters, virulence and colonization capacity can be constrained by the selection of O-antigen structures that are more easily recognized by the host immune system but which confer resistance to grazing by marine amoebae. This trade-off between the ability to colonize its host and environmental persistence is likely the cause of the great structural diversity observed for the O-antigen in this species. In a pathological context, we have shown that the species associated with the oyster are for the most part cytotoxic for the immune cells of their host, regardless of the environment considered (Atlantic, Mediterranean). This cytotoxicity is a key determinant of the escape from the oyster's powerful cellular defenses and determines the infectious success. We observed that the molecular bases of cytotoxicity are specific to each Vibrio species studied. Finally, beyond opportunistic pathogens that use cytotoxicity (V. tasmaniensis, V. crassostreae, V. splendidus, V. harveyi), we have identified simple opportunists, such as V. rotiferianus, which not only benefit from the immunosuppressive activity of other pathogens but also adopt strategies of non-cooperative acquisition of public goods, such as siderophores produced by the microbial community hosted by their host
Loison, Lea. "Rôle des interactiοns hôte-micrοbiοte dans la physiοlοgie intestinale et dans les Τrοubles du Cοmpοrtement Alimentaire". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMR049.
Testo completoThe gut microbiota constantly interacts with the host. It communicates directly with neighboring intestinal cells as well as with distant organs, including the brain. As a result, the microbiota regulates numerous biological processes and is involved in the pathophysiology of many diseases.We first investigated whether commensal bacteria from the gut microbiota modulate an essential post-translational modification in intestinal physiology, i.e. SUMOylation. It has been demonstrated that gut commensal bacteria can promote SUMOylation through the production of short- and branched-chain fatty acids (SCFA/BCFA). In the present study, we demonstrated that the commensal bacterium Staphylococcus warneri secretes a protein, named Warnericin RK, which targets key components of the SUMOylation machinery, leading to a decrease in intestinal cell’s SUMOylation. This decrease in SUMOylation promotes gut inflammation, and more particularly TNF-dependent inflammatory responses. Collectively, these findings highlight the versatility of mechanisms used by non-pathogenic bacteria in the gut microbiota to regulate host SUMOylation. Additionally, they show that changes in the composition of the gut microbiota may have an impact on gut inflammation by modulating the equilibrium between bacterial effectors enhancing or suppressing SUMOylation.Secondly, we investigated the role of the gut microbiota in the pathophysiology of Binge-Eating Disorder. Indeed, the microbiota is involved in the regulation of eating behaviors through communication along the gut-brain axis. Consequently, it has been hypothesized that the microbiota may be a contributing factor to binge-eating disorder. To investigate the potential causal role of the gut microbiota in this disease, we have transplanted fecal microbiota from patients to recipient mice. Our experimental model did not allow us to demonstrate a role for the microbiota in changes in eating behavior, or in the gastrointestinal and anxiety-depressive disorders associated with binge-eating disorder
Bredon, Marius. "Caractérisation de l'holobionte des isopodes par des approches omiques : exemple du processus de dégradation de la lignocellulose". Thesis, Poitiers, 2019. http://www.theses.fr/2019POIT2318.
Testo completoIsopods are good models to study interactions within the holobiont because they host a rich and diversified microbiota, whose composition is highly variable, depending on the environment and the host's life history traits. Some of their endosymbionts such as the feminizing bacteria Wolbachia, and their consequences on the evolutionary trajectory of hosts have been well characterised. A more global perspective of interactions within the holobiont and their impacts on the host’s fitness has been little considered. In this context, we used a combination of metagenomics, transcriptomics and gene expression analysis approaches to better understand the mechanisms and consequences of these interactions on the host's fitness. First, this thesis explores host-microbial interactions through the lignocellulose degradation process, which is essential for isopods’ nutrition. The host and microbiota’s enzymatic repertoires related to the degradation of lignocellulose have been identified in the woodlouse Armadillidium vulgare. The comparison of these two enzyme repertoires revealed their complementarity, suggesting a close collaboration between the host and its microbiota for lignocellulose degradation. The contribution of the host and its microbiota to this process was then quantified according to several diets with gene expression of CAZymes (enzymes specialized in lignocellulose degradation) and metabarcoding approaches. Secondly, the identification of the CAZymes repertoire in 64 transcriptomes of aquatic and terrestrial isopods provided new information on the evolutionary processes that have favoured the conquest of lands by isopods. This work was further developed by obtaining metagenomes of five isopod species to characterise lignocellulose deconstruction strategies in the holobiont. The reconstruction of bacterial genomes from metagenomes enabled us to identify other symbionts in isopods. We also have characterised a first virome of isopods, which shows that phages constitute an important part of the microbiota. They could play a crucial role as regulators of bacterial communities within the holobiont. All these studies illustrate the richness of interactions between the microbiota and the host in isopods for lignocellulose degradation, and open the way to new implications of the microbiota within the isopods’ holobiont
Partula, Valentin. "A nutritional epidemiology study of human gut microbiota - Associations with the systemic metabolism and usual diet of the host and relationships between dietary fibers and the host’s health". Thesis, Université de Paris (2019-....), 2019. http://www.theses.fr/2019UNIP7119.
Testo completoIt is now admitted that the gut microbiota plays a key role in the health status of its human host. It is indeed fully recognized as an endocrine organ producing biologically active molecules which are integrated within human metabolism. However, comprehensive studies characterizing host-gut microbial metabolic relationships remain scarce. Numerous factors have been shown to exert a modulatory impact on the gut microbiota. Notably, diet is supposed to be a major driver, but the relationships between usual diet and the gut microbiota are not fully elucidated yet. Furthermore, many studies have suggested the implication of the gut microbiota in a wide range of disease states, such as gastrointestinal, cardio-metabolic, neuropsychiatric, etc. disorders. Thus, understanding the factors influencing the gut microbiota constitutes an active area of research. In this context, we adopted an epidemiological approach to investigate one of the largest population-based samples so far (Milieu Intérieur population, N=1,000). We notably assessed the associations between gut microbiota composition on one hand and the systemic metabolism and the usual diet of the host on the other. Finally, in the NutriNet-Santé cohort (N≈160,000), we investigated the associations between the intake of dietary fibers and the risk of a variety of chronic diseases, and described how dietary fibers are associated with the gut microbiota.Overall, our results suggest that gut bacterial features are specifically associated with certain components of the systemic metabolism of the host, and we hypothesize a substantial role of the gut-kidney axis. Besides, negative associations between food items for which a limited consumption is generally recommended (i.e. processed foods) and gut microbial features were detected. Additionally, we confirm robust inverse associations between the consumption of dietary fibers and several major chronic diseases. Mounting evidence suggests that such effects could be mediated by the gut microbiota
Bernard, Lucie. "Utilisation de bactéries du microbiote pulmonaire pour moduler le système immunitaire local à l’état basal et pendant l’infection par Mycobacterium tuberculosis chez la souris". Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30027.
Testo completoHuman mucosal sites (such as the gut) are colonized from birth by trillions of microorganisms that form the microbiota (or commensal flora), living in symbiosis with our organism. Survival of the host and of its microbiota is dependent on the activation status of our immune system. While poor immune activation results in sensitivity to infections, its uncontrolled activation or inflammation compromises host tissue integrity. Bacteria from the gut microbiota naturally interact with cells of our immune system to preserve an equilibrium. Administration of such commensals as probiotics improve many disease outcomes and is currently studied to improve respiratory infection treatment. The primary infectious cause of death, tuberculosis, a respiratory disease caused by Mycobacterium tuberculosis, involves an over-activation of the immune system causing lung damages. In this thesis project, I investigated whether bacterial strains from the microbiota influence the immune response in tuberculosis to assess the potential of probiotics to improve tuberculosis treatment. In particular, we hypothesized that pulmonary commensal bacteria modify the local immune response to tuberculosis, as recently demonstrated in an asthma murine model. Through intranasal administration in mice, I first identified different lung commensal bacterial strains with a strong ability to modulate the lung CD4+ T cell compartment at steady state. Indeed, these strains induced T-helper (Th) cells involved in pro-inflammatory immunity, such as Th1 and Th17, and regulatory T cells (Treg) involved in anti-inflammatory responses. In particular, they increase proliferation of a specific Treg subtype, expressing RORt (a transcription factor characteristic of Th17). These RORt+ Treg were recently described in the gut, where they are induced by the microbiota and are able to decrease inflammation occurring in the mouse model of colitis. We show for the first time that these cells are induced in the lungs of mice treated with pulmonary bacterial strains from the Lactobacillus, Staphylococcus and Neisseria genera, and characterize their phenotype. As in the gut, these cells seem to have a strong anti-inflammatory profile, supported by their high expression of the inhibitory molecules CTLA-4 and PD-1, activation marker ICOS, and suppressive cytokine TGF- associated to a poor production of pro-inflammatory cytokines such as TNF-. Interestingly, I demonstrate that pulmonary Lactobacillus strains induced the same lung leukocyte populations in the mouse model of M. tuberculosis infection as in naïve mice, including RORt+ Treg. While none of the tested strains reduced M. tuberculosis burden in lung or spleen, the Lactobacillus murinus (CNCM I-5314) strain, which induce a high number of Th17 and RORt+ Treg accompanied by a reduced leukocyte infiltration in the lung, suggesting a capacity to reduce lung inflammation associated with M. tuberculosis infection. The role of Th17 and RORt+ Treg in this phenotype remains to be elucidated. Nevertheless, our results clearly indicate that the administration of pulmonary commensal bacteria strongly modulate the local immunity, even during chronic infections such as tuberculosis. Therefore, a better characterization of the lung microbiota components and of the mechanisms by which they interact with our immune system to maintain health in the respiratory system, might lead to the emergence of a new generation of probiotics, of lung origin, to better prevent and treat pulmonary diseases
Lopez, Valérie. "Impact du microbiote chez un insecte phytophage : interactions entre Delia radicum et ses symbiotes intra et extracellulaires". Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1B044/document.
Testo completoMicrobial symbionts can deeply influence their animal hosts in various ways. Here, we studied the community of microbes of the cabbage root fly (Delia radicum) and more precisely the role of its gut microbiota and of Wolbachia, an intracellular bacterium. The vertical maternal transmission of Wolbachia was perfect, and we found no evidence of manipulation of reproduction such as cytoplasmic incompatibility, thelytokous parthenogenesis, feminization nor male killing. Wolbachia infection had significant but moderate and mutually compensating effects on D. radicum (reduced hatch rate, improved larvo-nymphal viability, longer development time and increased female mortality in stress conditions), suggesting that infection might be nearly neutral in this strain, although we observed an increase in infection frequency in ideal rearing conditions. The influence of the gut microbiota was studied using an antibiotic, tetracycline, with a protocol spanning three generations, which allowed to discriminate the possible direct (toxic) effect of tetracycline from its indirect effects (due to the loss of gut symbionts). Antibiotic treatment of adults led to multiple and mostly negative effects on life history traits of their offspring and grandchildren. Data suggested a larger role of gut microbiota perturbation than of a toxic effect, that the microbiota was partially inherited maternally, and that the “wild-type” gut microbiota was beneficial in this species. Finally, we investigated whether Wolbachia could modify the insect-plant dialogue between D. radicum larvae feeding on roots of oilseed rape (Brassica napus). The presence of the symbiont decreased glucosinolate concentrations in the leaves, suggesting that Wolbachia could increase the fitness of its host by decreasing plant cues used by D. radicum conspecifics and/or natural enemies. This study showed the potential of an intracellular bacteria to influence plant-insect relationships, and allowed to discuss the tri-trophic interactions between symbionts, their insect hosts and a third trophic level: the plant. This thesis demonstrates the necessity to consider intracellular and extracellular symbionts in further studies, in order to unravel all the possible relationships between different partners, as well as their ecological or evolutionary implications
Haghebaert, Marie. "Outils et méthodes pour la modélisation de la dynamique des écosystèmes microbiens complexes à partir d'observations expérimentales temporelles : application à la dynamique du microbiote intestinal". Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASM036.
Testo completoThis thesis stems from the European project Homo.symbiosus, which investigates the equilibrium transitions of interactions between the host and its intestinal microbiota. To study these transitions, we pursue two directions: the mechanistic modeling of host-microbiota interactions and the analysis of temporal microbial count data.We enriched and simulated a deterministic model of the intestinal crypt using the EDK numerical scheme, particularly studying the impact of different parameters using the Morris Elementary Effects method. This model proved capable of simulating, on one hand, symbiotic and dysbiotic interaction states and, on the other hand, transition scenarios between states of dysbiosis and symbiosis.In parallel, a compartmental ODE model of the colon, inspired by existing studies, was developed and coupled with the crypt model. The thesis contributed to the enhancement of bacterial metabolism modeling and the modeling of innate immunity at the scale of the intestinal mucosa. A numerical exploration allowed us to assess the influence of diet on the steady state of the model and to study the effect of a pathological scenario by mimicking a breach in the epithelial barrier.Furthermore, we developed an approach to analyze microbial data aimed at assessing the deviation of microbial ecosystems undergoing significant environmental disturbances compared to a reference state. This method, based on DMM classification, enables the study of ecosystem equilibrium transitions in cases with few individuals and few time points. Moreover, a curve classification method using the SBM model was applied to investigate the effects of various disturbances on the microbial ecosystem; the results from this study were used to enrich the host-microbiota interaction model
Groh, Chloé. "Deciphering the interactions between plants and bacteria in the context of isoprenoid biosynthesis in Arabidopsis thaliana". Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAJ079.
Testo completoIsoprenoids are a large class of molecules found in all living organisms that are implicated in diverse biological processes. The aim of my thesis was to decipher if they could be involved in the interactions between plants and bacteria. Therefore, I worked on Arabidopsis thaliana wild-type and mutants, altered in the two isoprenoid biosynthesis pathways occurring in higher plants. An inventory of the communities interacting with wild-type and mutants highlighted some differentially abundant bacteria, despite the existence of a core microbiota. In addition, plants affected in the plastidial biosynthesis pathway, referred as the methylerythritol phosphate (MEP) pathway, have been shown to be more affected than wild-type by Pseudomonas syringae, a well-known phytopathogen. Together, these results suggest that isoprenoids may play a role in the interactions between plants and bacteria. In addition, 230 strains were isolated from A. thaliana in the laboratory, among which some of them were tested for their impact on the plant fitness and resistance to P. syringae, and for the impact on isoprenoids on these strains
Mansos, Lourenço Marta. "Deciphering in vivo efficacy of virulent phages in the mammalian gut". Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS260.pdf.
Testo completoThe mammalian gut is a heterogeneous environment inhabited by a large and diverse microbial community, including bacteria and their viral predators, bacteriophages (phages). Dynamic interactions between virulent phages and bacteria in the gut are still poorly understood, which is also an obstacle for the design of successful therapeutic interventions based on phages. Independent experiments have shown that virulent phages were found to have no major effects on their targeted bacteria in the gut, in spite of sustainable phage amplification. This suggests that there are unknown factors in the gut environment that modulate these interactions. Using comparative transcriptomics analysis of E. coli grown in vitro and in vivo (within the mammalian gut) we found that in the gut, bacteria downregulate the expression of genes related to phage receptors, which provides an explanation for the lack of selection of phage-resistant bacteria during in vivo experiments. We also found that the acquisition of a pathogenicity island commonly found in human E. coli isolates affects phage susceptibility possibility by downregulating a defense mechanism against invading DNA. Finally, we examined the repartition of phages and bacteria through mucosal and luminal gut sections and observed a heterogeneous spatial distribution of these two antagonist populations, supporting the hypothesis of source-sink dynamics. Altogether our data demonstrates that multiple factors encompassing, spatial distribution, bacterial physiology and defenses against foreign DNA modulate the interactions between bacteria and phages within the gut
Graziani, Fabien. "Communication moléculaire microbiote - hôte : impact de Ruminococcus gnavus E1 sur la glycosylation des cellules épithéliales intestinales". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4312.
Testo completoThe aim of IM3I group is study molecular mechanisms involved in the symbiotic relationship between the host and the intestinal microbiota, accounting for both partners, in order to propose solutions to human health problems, especially in the context of nutrition and food safety. We have chosen a Gram positive bacteria, Ruminococcus gnavus E1, as a model. This bacterium, in strict anaerobia, is isolated from the dominant microbiota of healthy human for which the genome is currently being sequenced. In vivo, using animals that are mono-associates with R. gnavus E1, our RT-qPCR studies clearly show an up regulation of the expression of genes coding for intestinal fucosyltranferases and sialyltransferases, in the colon. This is also confirmed by confocal microscopy using lectins. Thus, R. gnavus E1 is able to reestablish the glycosylation profile. In vitro, we have studied the impact of soluble factors from the R. gnavus E1 supernatant. We found that the soluble supernatant fraction of R. gnavus E1 cultures differentially modulates the intestinal glycosylation process in HT29-MTX, Caco-2, independently or coculture 75% Caco-2 and 25% HT29-MTX cell lines. Preliminary characterization of this soluble fraction indicates that it is heat resistant, is not affected by elimination of lipids, and has a low molecular weight form (< 3 kDa). We conclude that the variation of expression of mRNAs coding for different glycosyltransferases in goblet cells and enterocytes proves the re-initiating program of glycoproteins and mucus protection layer by the dominant bacteria R. gnavus E1 and opens the prospect to a new host-indigenous bacteria molecular crosstalk in the intestine
Huot, Camille. "Caractérisation et rôle dans l'interaction tripartite du microbiote d'hôtes intermédiaires Planorbidae des parasites trématodes Schistosoma spp. agent responsable de la bilharziose". Thesis, Perpignan, 2019. https://theses-public.univ-perp.fr/2019PERP0041.pdf.
Testo completoEvery living organism is faced, eventually, to microorganisms, whether they are bacteria, viruses, fungi or protists. Microbiota largo sensu represent all these microorganisms, living in a host a T time. It is considered, since years, as an integral compartment of its host. It can affect several host functions, like nutrition, development or immunity. Thus, it can play a key role in interactions between organisms, notably hosts/parasites and hosts/pathogens interactions, improving the immune system of its host or directly affecting the invader. The case of Biomphalaria glabrata and other Planorbidae, intermediate hosts of Schistosoma sp. parasites, responsible agent for bilharzia, is a perfect model to study the role of microbiota in host/parasite interactions. Indeed, understanding the interaction between the worm and its intermediate host could open the way for new measure to fight it, as blocking its lifecycle. The characterization of mollusks' microbiota and its role in the interaction is, thus, an interesting way to explore. During my PhD, I (i) characterized the bacterial and protist microbiota of several Planorbidae species in order to compare it according to host phylogeny; (ii) studied the dynamic of microbiota bacterial communities during an infection kinetic in different B. glabrata strains and; (iii) disturbed the bacterial microbiota and observed the consequences on the mollusks resistance to parasite, in order to highlight a potential role of these bacteria in their host immunity. One of the main results of this work is the high specificity of bacterial communities to their host phylogeny, displaying a phylosymbiosis pattern. Moreover, a variation in infection intensity or prevalence has been highlighted, depending on host/parasite combination, after a microbiota disturbance, suggesting a link between the latter and the antiparasitic immunity of mollusks. Thus, this PhD work is a first step in the understanding of the tripartite interaction between a parasite, its intermediate host and the microbiota of the latter, that could, in time, open new perspectives in the fight against the responsible agent of bilharzia
Tandina, Fatalmoudou. "Mise au point et application de technologies innovantes pour l'étude des moustiques, de leur préférence trophique et de leur microbiote". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0277/document.
Testo completoMosquitoes are the main vectors involved in the transmission of pathogens to humans. Accurate identification of mosquito species is crucial to distinguish between vector and non-vector species. The mosquito blood meal determination is fundamental in understanding the behavior of vector species. Thus, we have listed 106 mosquito species currently recorded in Mali, including 28 Anophelinae and 78 Culicinae. Then, we evaluated the effectiveness of MALDI-TOF MS for identified mosquitoes collected in Mali and to determine their blood meal source. The results obtained show the ability of MALDI-TOF MS to identify mosquitoes collected in Mali and their source of blood meal. Subsequently, we were able to confirm the robustness of MALDI-TOF MS to identify other animal blood samples. We artificially engorged Anopheles gambiae and Anopheles coluzzii on eight animal bloods samples. We obtained 100% correct identification of the blood source for samples taken 1 to 24 hours after feeding. Then, we experimentally engorged An. gambiae, An. coluzzii and Ae. albopictus on successive and mixed blood meals using MALDI-TOF MS. The results revealed that MALDI-TOF MS is able to identify mixed blood meals. In addition we used MALDI-TOF and culturomics for the microbiota study of the mosquito collected in the field, notably in Marseille and Mali. The culturomics approach revealed a great diversity of the digestive microbiota of the An. gambiae, Ae. albopictus and Cx. quinquefasciatus mosquitoes
Tamarelle, Jeanne. "Composition et dynamique du microbiote vaginal : facteurs associés et rôle dans l’infection par Chlamydia trachomatis The vaginal microbiota and its association with human papillomavirus, Chlamydia trachomatis, Neisseria gonorrhoeae and Mycoplasma genitalium infections: a systematic review and meta-analysis Vaginal microbiota composition and association with prevalent Chlamydia trachomatis infection: a cross- sectional study of young women attending a STI clinic in France Nonoptimal Vaginal Microbiota After Azithromycin Treatment for Chlamydia trachomatis Infection". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV097.
Testo completoChlamydia trachomatis (CT) is a sexually transmitted bacteria responsible for cervicitis, urethritis, and pelvic inflammatory diseases leading to subsequent tubal infertility and ectopic pregnancies. It is the most frequent sexually transmitted infection worldwide, including in France. Epidemiological data indicate that the incidence rate is increasing despite the implementation of control measures, which motivates the revision of current screening strategies. The vaginal microbiota could play a major role in preventing sexually transmitted infections through ecological competition and metabolites, such as lactic acid production. The vaginal microbiota corresponds to a fine-tuned equilibrium likely to be modified by exposures such as sexual practices, hygiene practices, antibiotics but also presence of pathogens. The overall objective of this thesis is to study the association in this triangle composed of external exposures, vaginal microbiota and CT infection, through the study of the vaginal microbiota composition and dynamics. We aimed at answering these questions: are there biomarkers of CT infection in the vaginal microbiota? Are the vaginal microbiota composition and structure modified by CT infection and antibiotic consumption? What are the exposures associated with perturbations of the vaginal microbiota? To answer these questions, the first step consisted of a state of the art to estimate the association between vaginal microbiota and CT infection in the literature, as well as three other clinically relevant sexually transmitted infections, and to evaluate the role of several factors in the observed heterogeneity between studies. In a second step, we estimated this association using molecular characterization of the vaginal microbiota in two studies in France and in the United States. We showed that Lactobacillus iners-dominated communities (CST III) and Lactobacillus-deprived communities (CST IV) were over-represented among CT-positive women. By studying the vaginal microbiota after azithromycin treatment and CT clearance in the American study, we showed that the vaginal microbiota did not evolve towards an optimal state, suggesting that women may stay at risk of CT reinfections. Finally, in two longitudinal studies using frequent sampling in the United States, we studied exposures associated with incidence and clearance of a CST IV. We showed that when the vaginal microbiota was not dominated by L. iners, menses was the main factor associated with incidence and clearance of a CST IV, while for women whose vaginal microbiota is dominated by L. iners, menses but also lubricant use, douching, ethnic origins, age and condomless vaginal sex were associated with CST IV incidence and/or clearance. Therefore, this thesis allowed on the one hand to confirm the association between Lactobacillus-deprived vaginal microbiota and CT infection using genome sequencing, and on the other hand to single out L. iners from other Lactobacillus spp. and to evaluated the risk associated with CST III. By enabling a better understanding of the natural history of CT and of the vaginal microbiota dynamics, we hope to contribute to improving strategies for the control of CT infection and other STIs. The innovative potential of the project lies in the use of molecular methods, which allows refining of our approach of health management by integrating individual predisposition to sexually transmitted infections, thus paving the way for personalized medicine
Portet, Anaïs. "Décryptage du Polymorphisme de Compatibilité dans l’interaction entre Biomphalaria glabrata et Schistosoma mansoni : une approche intégrative". Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0035/document.
Testo completoBiomphalaria glabrata is tropical fresh water snail, living in Latin America. This planorbe is the intermediary host of Schistosoma mansoni, a trematode responsible for the intestinal Schistosomiasis, second worldwide human vector-borne disease after the malaria. In this context, a better comprehension of the parasite/snail interaction is necessary and appearsa promising research field. The understanding of immunological interaction between the host and the parasite and the molecular mechanisms used by the two partners appears like essential for the discovery of new targets and new strategies in order to develop means of struggle against the pathogen. The aim of this thesis is to better understand the immunological interactions between the B. glabrata snail and S. mansoni trematode. Different aspects of the interaction between the snail and the parasite have been explored, from molecular and cellular bases to the tripartite interaction between the snail immunity, its microbiota and the pathogen. In a first step we have been able to demonstrate a gradient of parasite infectivities and snail susceptibilities from different geographical origins. Moreover, the immunological interaction between B. glabrata and S. mansoni is supported by local adaptation, at the molecular level. We were also able to show than an opsonin, the BgTEP, plays a key role in the interaction between B. glabrata and its various pathogens. Finally, the existence of a true tripartite interaction between the snail immune response, its microbiota and its parasite could was demonstrated
Michaud, Caroline. "Dynamique des symbioses mutualistes hôtes-microbiotes : mode et efficacité de transmission des symbiotes dans les populations du termite xylophage Reticulitermes grassei". Thesis, Tours, 2019. http://www.theses.fr/2019TOUR4027.
Testo completoMany animals including humans live in symbiotic interaction with gut microorganisms contributing to essential functions (nutrition, immunity). The ‘vertical’ way of transmission of symbionts (i.e., from parents to offspring) must stabilise these symbioses, notably by strengthening partner fidelity. However, the efficiency of vertical transmission has rarely been studied, especially in the case where hosts harbour a complex microbial community (or ‘microbiota’) composed by many microbial taxa interacting between them and with the host.The objective of this work was to study the mode and efficiency of transmission of gut microorganisms (protists and bacteria) helping the wood-feeding termite Reticulitermes grassei to digest ingested wood (lignocellulose fibres). Our results revealed contrasted situations between microorganisms. While protists are efficiently vertically transmitted, the majority of bacterial taxa is not only vertically transmitted but seems to be acquired by the environment