Background: The relationship of diffusely adherent Escherichia coli (DAEC) with pediatric inflammatory bowel disease (IBD) has not been previously studied. Diffusely adherent E. coli are a common cause of long-lasting childhood diarrhea and we postulated that they may induce inflammation of the intestinal mucosa, contributing to the development of IBD in susceptible children.
Objectives: The aim of the study was to investigate the relationship between DAEC and pediatric IBD, including Crohn's disease (CD) and ulcerative colitis (UC). Diffusely adherent E. coli isolates were also assessed regarding their pathogenicity.
Material and methods: Diffusely adherent E. coli were screened among 130 E. coli strains isolated from intestinal biopsy specimens from 26 children with IBD using polymerase chain reaction (PCR) with primers specific to the pathotype and adherence assays to HEp-2 cells. Diffusely adherent E. coli were further analyzed for their ability to adhere to and invade polarized Caco-2 cells. The immunomodulatory effect of DAEC on the secretion of tumor necrosis factor α (TNF-α) by human monocyte-derived macrophages (MDM) was assessed using an immunoenzymatic assay.
Results: Diffusely adherent E. coli were recovered from 18 (69.2%) of the 26 intestinal biopsy specimens from both CD and UC patients. Most DAEC isolates carried AfaE3 adhesin, adhered to and were internalized by Caco-2 cells, and induced secretion of elevated levels of TNF-α.
Conclusions: The study demonstrated the internalization of DAEC by intestinal epithelial cells and their ability to induce secretion of increased level of TNF-α in a Caco-2/macrophage compartmentalized culture. This indicated that the pathovar should be considered a pathobiont inducing inflammation of the intestinal mucosa in pediatric patients with IBD.
Keywords: AfaE3 adhesin; childhood inflammatory bowel disease; diffusely adherent E. coli.