Impact of antibiotics treatments on piglet gut microbiota : In vivo study and development of an in vitro fermentation system ; Impact de traitements antibiotiques sur la flore digestive du porcelet : Etude in vivo et développement d'une approche en système de fermentation in vitro

In the context of antibiotic resistance, the aim of the current PhD work is to assess the impact of antibiotics on intestinal microbiota of piglets. Two antibiotics i.e. colistin and ceftiofur, for which the main resistances include respectively chromosomal mutations and plasmid genes have been used. Colistin significantly reduced the population of Enterobacteriaceae, but there was no selection of resistant E. coli. The administration of ceftiofur had a limited impact on the bacterial populations that make up the digestive ecosystem but it led to strong selection and dissemination of a plasmid gene encoding an extended-spectrum beta-lactamase. Then, in the framework of regulations to reduce animal testing, an in vitro model of colonic pig named PigutIVM was developed in order to simulate the digestive environment of the piglet and then check the effect of colistin on the microbiota simulated in PigutIVM in vitro. Therefore both the approaches i.e. in vivo and in vitro were compared in order to check the effect of colistin on intestinal microbiota of piglets. This tool was then used to evaluate the impact of a probiotic i.e. Saccharomyces cerevisiae, as alternative to antibiotics. Therefore we assume that this PigutIVM model should be positioned as a relevant predictive tool in the fields of nutritional and pharmacological investigations. ; Dans le contexte de l'antibiorésistance, l'objet de ce doctorat vise à évaluer l'impact d'antibiotiques sur le microbiote intestinal de porcelets. La colistine et le ceftiofur, pour lesquels les résistances incluent essentiellement et respectivement mutations chromosomiques et gènes plasmidiques, ont été utilisés. La colistine a significativement réduit la population des entérobactéries, mais aucun E. coli résistant n'a été détecté. L'administration de ceftiofur a eu un impact limité sur les populations bactériennes composant l'écosystème digestif mais a conduit à une forte sélection et à la diffusion d'un gène plasmidique codant pour une bêta-lactamase à spectre étendu. Puis, ...