OCLN and inflammatory bowel disease: For example, a large number of studies have shown that ETEC infection induced IBD in the host, which is accompanied by intestinal mucosal damage, DAO and DLA increases in serum [53,54,55,56], production of a large number of inflammatory factors and aggravation of intestinal epithelial barrier dysfunction, including decrease of Zonula occludes, claudins and occludin [43,44,45].