戊糖片球菌对ETEC感染断奶仔猪肠道微生物区系及NF-κB炎症信号通路的影响

断奶仔猪ETEC腹泻是当前集约化养殖条件下导致仔猪生长受阻和死亡率高的主要原因。微生物饲料添加剂具有恢复肠道菌群平衡和提高肠道免疫功能的作用，作为饲用抗生素替代品具有广阔的应用前景。申请者前期研究发现，自主分离的戊糖片球菌L1具有耐受胃肠道环境、有效黏附肠上皮细胞等益生特性，并抑制了猪肠上皮细胞中炎症基因表达和NF-κB信号通路活化；给断奶仔猪预先灌服L1菌液，ETEC腹泻率显著降低，表明戊糖片球菌L1具有作为微生物饲料添加剂的发展潜力。因此，本项目拟研究戊糖片球菌L1对ETEC感染断奶仔猪肠道微生物区系，肠黏膜组织炎症反应，肠黏膜组织NF-κB信号通路关键基因表达、核内信号活化、抑制蛋白降解和上游激酶活化的影响，阐明戊糖片球菌促进ETEC感染断奶仔猪肠道健康的作用机制，研究成果对深入阐明微生物制剂预防断奶仔猪腹泻的作用机理，降低抗生素依赖，提高动物食品安全，具有重要的理论和现实意义。

Enterotoxigenic Escherichia coli (ETEC) is a major cause of intestinal infection in piglets inducing diarrhea, reduced growth rate and mortality leading to economic loss. Microbial feed additives are promising alternative to antibiotics due to their attributed benefits on promoting the homeostasis of gut microbiota and modulating intestinal immune functions. In our previous study, Pediococcus pentosaceus L1 we isolated showed resistance to piglet gastrointestinal conditions, effective adhesion to intestinal epithelial cells, and antimicrobial activity on ETEC. Pediococcus pentosaceus L1 also down-regulated expression of proinflammatory genes as well genes associated with NF-κB pathway. Administration of Pediococcus pentosaceus L1 before ETEC challenge reduced the diarrhea incidence. These results have shown the potential of Pediococcus pentosaceus L1 as a microbial feed additive. The over-arching objective of this proposal is to investigate the mechanism involved in prophylactic effect of Pediococcus pentosaceus L1 on weaned piglets challenged with ETEC. To meet this challenge, objectives to be met include (a) Investigation of effects of administration of Pediococcus pentosaceus L1 before ETEC challenge on intestinal microbiota community in weaned piglets and (b) investigation of effects of Pediococcus pentosaceus L1 before ETEC challenge on intestinal inflammation in weaned piglet and (c) investigation of effects Pediococcus pentosaceus L1 before ETEC challenge on expression of genes associated with NF-κB pathway, nuclear NF-κB activity, degradation of nuclear factor kappa B inhibitor protein-α, and activation of critical upstream kinases of NF-κB signaling in weaned piglets. This research will elucidate the modes of Pediococcus pentosaceus improving intestinal health in weaned piglet challenged with ETEC and provide insight into the mechanisms underlying the preventive effect of microbial feed additives on ETEC-induced piglet diarrhea. This research will also emphasize the possibility of microbial feed additives for safe animal food production.