EXPERIMENTAL APPROACH
The chicken colibacillosis model was established by intratracheal instillation of APEC. The gut microbiota-depleted chicken model was established with broad-spectrum antibiotics. Viscera index measurement and Haematoxylin and eosin stain were applied to assess histological changes of tissues. ELISA were used to measure the cytokines and Quantitative-PCR were used to evaluate the gene expression. The gut microbiota and its metabolite were detected by 16srDNA and ultrahigh-performance liquid chromatography (LC-MS).