[Adherent-invasive Escherichia coli isolated from a Crohn's disease patient exhibits colonization capacity and pro-inflammatory effects in the murine intestine].

UNLABELLED: The role of gut microbiota composition in the initiation and/or perpetuation of intestinal inflammation in inflammatory bowel disease (IBD), particularly in Crohn's disease (CD) patients, is currently under active investigation. This study aimed to establish optimal conditions for modeling gut inflammation induced by an adherent-invasive Escherichia coli (E. coli) (AIEC) strain isolated from a CD patient in an in vivo experiment.

MATERIAL AND

METHODS

The study was conducted using three groups of male C57Black/6 mice (6 mice per group). Group 1: water-control, group 2 - propionate-control, group 3 - BL2K2-propionate. After an 8-day quarantine, mice in groups 2 and 3 received 20 mM sodium propionate solution instead of drinking water. On the 4th day, 24 h prior to bacterial inoculation, all mice were orally gavaged with 20 mg streptomycin in 100 μL phosphate buffer. The following day, experimental mice (group 3) were inoculated with the AIEC strain E. coli BL2K2 (isolated from a CD patient) in 100 μL phosphate buffer, while control mice (groups 1 and 2) received phosphate buffer alone. Tissue samples (blood, small intestine, cecum, and colon) were collected at 21, 28, and 35 days post-inoculation. Lysates were obtained from intestinal compartments, some of which were used for plating on selective E. coli media, obtaining individual colonies, and then performing whole-genome sequencing to confirm BL2K2 colonization of different intestinal compartments. The remaining lysates were used for cytokine content determination by ELISA and proteomic analysis.

RESULTS

The CD-associated AIEC strain successfully colonized the murine gut under these conditions, with colonization persisting for 35 days and inducing significant histopathological changes in the colon, small intestine, and cecum. Elevated levels of TNF-α and IL-6 were detected in colon lysates. Comparative proteomic analysis of colon tissue revealed activation of bacterial infection response pathways with increased levels of immunoglobulins, T-cell response activators, FimH (type I pili receptor), secreted lectins, TLR-mediated regulators, and bactericidal proteins, as well as activation of processes associated with the accumulation of extracellular matrix (ECM) with upregulation of collagens, collagen fibril assembly regulators, and integrins, alongside downregulation of ECM degradation proteins, suggesting fibrotic changes which is one of the signs of an inflammatory process. The CD-associated AIEC strain colonization lead to disrupted lipid metabolism and reduced energy metabolism in colon tissue.

CONCLUSION

We developed a ready-made system to study AIEC involvement in the initiation and maintenance of intestinal inflammation, providing a platform for further investigation of AIEC's role in this process.