摘要Background:Compared with oral antibiotics (primarily disrupt foregut microbiota),the present study used antibiotics with ileum terminal infusion to disrupt the hindgut microbiota,and investigated the changes in specific bacterial composition and immune indexes in the jejunum and colon,and serum of growing pigs.Twelve barrows (45 d of age,12.08 ± 0.28 kg) fitted with a T-cannula at the terminal ileum,were randomly assigned to two groups and infused either saline without antibiotics (Control) or with antibiotics (Antibiotic) at the terminal ileum.After 25 d experiment,all pigs were euthanized for analyzing bacterial composition and immune status.Results:Ileum terminal antibiotic infusion (ITAI) altered dominant bacteria counts,with a decrease in Bifidobacterium,Clostridium cluster Ⅳ and Clostridium cluster Ⅳ in the colon (P ＜ 0.05),and an increase in Escherichia coli in the jejunum (P ＜ 0.05).ITAI decreased (P ＜ 0.05) short-chain fatty acids concentrations in the colon.ITAI decreased interleukin-8 (IL-8),IL-10 and secretory immunoglobulin A (slgA) concentrations,and down-regulated IL-10,Mucin-1 (MUC1),Mucin-2 (MUC2) and zonula occludens-1 (ZO-1) mRNA expression in the colonic mucosa (P ＜ 0.05).In the jejunal mucosa,ITAI decreased interferon-y (IFN-y),tumor necrosis factor-α (TNF-α),slgA and IgG levels together with down-regulation of IFN-y,TNF-α,MUC2 and ZO-1 mRNA expression (P ＜ 0.05).Furthermore,ITAI decreased IL-10,INF-y,TNF-α,IgA and IgG concentrations in serum (P ＜ 0.05).Correlation analysis revealed that the change in intestinal microbiota was correlated with alterations of Ig and cytokines.Conclusions:ITAI affected jejunal and colonic specific bacteria counts,and altered some immune markers levels in the jejunal and colonic mucosa and serum.These findings implicate the potential contribution of hindgut bacteria to immune response in the intestinal mucosa and serum of growing pigs.