Probiotics in inflammatory bowel disease--therapeutic rationale and role.

The intestinal flora has a conditioning effect on intestinal homeostasis, delivering regulatory signals to the epithelium, the mucosal immune system and to the neuromuscular activity of the gut. Beneficial metabolic activities of the enteric flora include nutrient production, metabolism of dietary carcinogens, conversion of prodrugs to active drugs. However, increasing evidence suggests that some components of the enteric flora are essential ingredients in the pathogenesis of inflammatory bowel disease (IBD); this has prompted interest in therapeutic manipulation of the flora with probiotics. Probiotics are biologic control agents-described as live microbial food supplements which confer a health benefit beyond inherent basic nutrition. Multiple potential beneficial effects have been attributed to the probiotic use of lactic acid bacteria, bifidobacteria and other non-pathogenic commensals. At present, much of the promise of probiotics remains outside the realm of evidence-based medicine and awaits the results of prospective trials, now underway. No reliable in vitro predictors of in vivo efficacy of putative probiotics have been identified. Rigorous comparisons of probiotic performance have not been performed and the suitability of a given probiotic for different individuals is largely unexplored. Notwithstanding, an improved understanding of the normal commensal flora and host-flora interactions has the potential to open up new therapeutic strategies for inflammatory disorders of the gut.