Effects on the intestinal morphology, inflammatory response and microflora in piglets challenged with enterotoxigenic Escherichia coli K88

Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrhea in piglets, which leads to great economic losses. In this study, the ternary crossbred weaned piglets were orally administered with 1.5 × 1011 CFU ETEC K88 for three days. The results showed the ratio of villus length to crypt depth decreased in the duodenum and ileum after ETEC K88 infection. The expression of tight junction proteins ZO-1 in the jejunum and ileum, occludin in the jejunum and colon, and claudin-1 in the colon were down-regulated. The expression of IL-8 in the duodenum and jejunum, IL-13 in the colon, and TNF-α in the jejunum and colon were up-regulated. The expression of pBD1 in the colon, pBD2 in the jejunum, and pBD3 in the duodenum increased after infection. Meanwhile, the expression of TLR4, p38 MAPK and NF-κB p65 increased in all intestinal segments. Moreover, the expression of IL-8 in superficial cervical lymph nodes (SCLN), TNF-α in mesenteric lymph nodes (MLN), and IL-13 in inguinal lymph nodes (ILN) and MLN were up-regulated. The expression of pBD1 and pBD2 in SCLN and MLN, and pBD3 in SCLN were up-regulated. Acidobacteria and Proteobacteria were the most abundant phyla in both groups by analysis of intestinal microflora using 16 s rRNA sequencing, and the relative abundances of bacteria were found to be changed by Metastats software and LEfSe analysis. Our results indicated that cytokines and pBDs had different roles in different intestinal segments or different lymph nodes against ETEC K88, and gut microbiota was influenced after infection.