Nonpathogenic Escherichia coli strain Nissle1917 prevents murine acute and chronic colitis

Background: Nonpathogenic Escherichia coli strain Nissle1917 has been used as a probiotics in human inflammatory bowel disease; however, there are few reports examining its therapeutic effect on animal colitis models, and its therapeutic mechanisms remain unknown. The aim of this study was to elucidate the therapeutic effect and mechanism of Nissle 1917 using murine acute and chronic colitis models. Methods: Two models were used. (1) Acute model: colitis was induced by administration of 1.3% dextran sodium sulfate for 7 days. Nissle 1917 or phosphate-buffered saline were orally administered for l 0 days. Mice were killed at day 10, and the colonic lesions were assessed macro- and microscopically. (2) Chronic model: IL-10(-/-) mice were treated with Nissle1917 or phosphate-buffered saline for 8 weeks. After 8 weeks of treatment, mice were killed to assess the colonic lesions macro- and microscopically In the acute dextran sodium sulfate colitis model, viable, heat-killed, or genomic DNA of Nissle 1917 was orally administered for 10 days, and the therapeutic effect was assessed. Results: In the acute model. Nissle1917 ameliorated body weight loss, disease activity index.. and macro- and microscopic damage. In the chronic model, it also suppressed the mucosal inflammatory findings and histologic damages. Moreover, heat-killed Nissle 1917 or its genomic DNA alone also ameliorated the acute DSS colitis and viable bacteria macro- and microscopically. Conclusions: Nonpathogenic E. coli strain Nissle1917 prevents both acute and chronic colitis, and its anti-inflammatory effect is exhibited not only by viable bacteria but also by heat-killed bacteria or its DNA.