The demonstration that immune and epithelial cells can discriminate between different microbial species has extended our understanding of the actions of probiotics beyond simple antimicrobial concepts. Several probiotic mechanisms of action, relative to inflammatory bowel disease, have been elucidated: (1) competitive exclusion, whereby probiotics compete with microbial pathogens; (2) immunomodulation and/or stimulation of an immune response; (3) antimicrobial activity and suppression of pathogen growth; (4) enhancement of barrier activity; and (5) induction of T cell apoptosis. The unraveling of these mechanisms of action has led to new support for the use of probiotics in the management of clinical inflammatory bowel disease. While level 1 evidence now supports the therapeutic use of some probiotics in the maintenance treatment of pouchitis, only level 2 and 3 evidence are currently available in support of the use of probiotics in the treatment of ulcerative colitis and Crohn's disease. Nevertheless, one significant and consistent finding has emerged over the course of research in the past year: not all probiotic bacteria have similar therapeutic effects. Rigorously designed, controlled clinical trials, to investigate the unresolved issues related to efficacy, dose, duration of use, single or multistrain formulation, and the concomitant use of prebiotics, synbiotics or antibiotics, are vital.
Division of Gastroenterology, Department of Medicine, University of Alberta, Edmonton, Al, Canada
Reprints: Dr Richard N. Fedorak, Division of Gastroenterology, Zeidler Family Gastrointestinal Health and Research Centre, Zeidler Ledcor Buidling, 130 University Campus, Edmonton, Canada Al T6G 2C8 (e-mail: firstname.lastname@example.org)
Dr Rioux's research is supported by Canadian Association of Gastroenterology, Canadian Institutes for Health Research, Crohn's and Colitis Foundation of Canada, Alberta Heritage Foundation for Medical Research. Dr Fedorak's research is supported by Canadian Institutes for Health Research, Crohn's and Colitis Foundation of Canada.
Received for publication September 7, 2005; accepted November 16, 2005