Probiotics for preventing relapse or recurrence in Crohn's disease involving the ileum: Are there reasons for failure?

In contrast to ulcerative colitis and pouchitis, benefits of probiotic therapy in preventing recurrence/relapse in Crohn's disease (mostly involving the ileum) are far from being proven. The lack of response in this setting does not seem attributable to a lower relevance of dysbiosis in ileal Crohn's disease, since this - or at least the presence of increased mucosal amounts of potentially pathogen bacteria - has been proven to occur in the ileum of Crohn's disease patients. Available data indicate that whereas in ulcerative colitis (and to a lesser extent in colonic Crohn's disease) the innate immune response is enhanced, it is constitutively depressed in ileal Crohn's disease. Therefore, attempts to modify the composition of intestinal microflora in colonic IBD or pouchitis by means of probiotics do make sense. In contrast, supplying additional bacteria (even being probiotics) to an ileum with decreased antibacterial defence does not seem reasonable. In fact, the presence of intestinal contents has been reported to be related to postoperative recurrence in ileo-caecal Crohn's disease, and antibiotic treatment in effective to prevent its development.