Intestinal effect of the probiotic Escherichia coli strain Nissle 1917 and its OMV Original paper

What was reviewed?

The intestinal effect of Escherichia coli Nissle 1917 is the core focus of this narrative review, which examines how this probiotic strain and its outer membrane vesicles act on the gut barrier, the intestinal microbiome, and host immunity in states of health and disease. The authors describe the shift from a diverse microbiome rich in Firmicutes and Bacteroidetes to a dysbiotic pattern that shows loss of beneficial commensals and increased Gammaproteobacteria in inflammatory bowel disease and other intestinal disorders. They then position Escherichia coli Nissle 1917 as a non-pathogenic Gammaproteobacterium with probiotic potential, and they explore how its secreted factors and vesicles interact with epithelial and immune cells. The review integrates molecular work, animal models, and clinical data to link these microbial actions to outcomes such as maintenance of remission in ulcerative colitis, support of colonic health in Crohn’s disease, and reduction of acute diarrhoea in children.

Who was reviewed?

The review brings together evidence from three main groups, which are cell-based systems, animal models, and human participants. In vitro work involves human intestinal epithelial cell lines such as T84 and HT 29, where exposure to Escherichia coli Nissle 1917 or its isolated vesicles alters tight junction protein expression and induces antimicrobial peptides. Animal studies mainly use mouse models of experimental colitis, for example, dextran sodium sulfate colitis, in which oral or rectal administration of live bacteria or purified vesicles reduces clinical scores, dampens mucosal cytokine release, and improves barrier structure. Human data come from clinical trials and observational studies in infants with acute diarrhoea, in adults with ulcerative colitis, in patients with colonic Crohn disease, and in individuals with diverticular disease, where Escherichia coli Nissle 1917 appears as a therapeutic or preventive option and where associated microbiome changes and clinical endpoints are recorded.

Most important findings

The review shows that dysbiosis in inflammatory bowel disease usually includes loss of key commensal groups, especially selected Firmicutes and Bacteroidetes, together with expansion of Gammaproteobacteria, yet Escherichia coli Nissle 1917 stands out as a beneficial member of this expanded group. In epithelial models, the strain enhances barrier integrity by increasing expression and correct localisation of tight junction proteins such as zonula occludens 1, zonula occludens 2, and specific claudins, while it reduces activity of some protein kinase C isoforms that disrupt junctions, and these actions limit paracellular leak in the presence of injurious stimuli. Escherichia coli Nissle 1917 also induces human beta defensin 2 through nuclear factor kappa B and activator protein 1 signalling and engages toll like receptors via flagellin, which leads to increased antimicrobial peptide production and a controlled pro inflammatory response that helps to restrain pathogens without excess tissue damage.

The authors identify outer membrane vesicles from Escherichia coli Nissle 1917 as a central mediator of these effects because the vesicles carry lipopolysaccharide, peptidoglycan, lipoproteins, DNA, RNA, and small regulatory RNAs, and they can cross the mucus layer and enter epithelial cells through clathrin-dependent uptake. In mouse colitis models, oral vesicles reproduce much of the anti-inflammatory and barrier protective activity of the live strain, and they reduce histologic injury, cytokine levels, and disease scores. The review compares these data to work on vesicles from Akkermansia muciniphila and Bacteroides fragilis. It suggests a shared postbiotic signature in which vesicle-producing commensals promote barrier repair, downregulate mucosal inflammatory mediators, and influence epithelial gene expression, possibly through transfer of small RNAs. At the same time, the authors also note the presence of the colibactin gene cluster in Escherichia coli Nissle 1917 and call for continued safety monitoring despite the favourable clinical record.

Key implications

For clinical practice, the review supports Escherichia coli Nissle 1917 as a microbiome-directed option that strengthens the intestinal barrier and modulates immune responses in inflammatory bowel disease and related gut disorders. Trials indicate that the strain can maintain remission in ulcerative colitis with comparable efficacy to mesalazine, can aid relapse prevention in colonic Crohn disease, and can shorten the course of acute infectious diarrhoea in children, which places it as a practical adjunct in selected patients. The emphasis on outer membrane vesicles suggests a future shift toward postbiotic strategies that use defined vesicle preparations or engineered vesicles to deliver beneficial bacterial signals without live organisms, which may improve safety in vulnerable hosts.