Purpose of review
The author presents evidence published during the past year regarding treatment of clinical and experimental intestinal inflammation and infections by probiotic agents.
Normal commensal bacteria are implicated in the pathogenesis of chronic, immune-mediated intestinal inflammation, particularly Crohn disease and pouchitis, whereas viral, bacterial, fungal, and protozoan infections are increasingly important with widespread use of immunosuppressive agents and broad-spectrum antibiotics. Combinations of Lactobacilli, Bifidobacteria, and Streptococcus salivarius prevent relapse of recurrent pouchitis and perhaps decrease the initial onset of pouch inflammation, whereas Escherichia coli Nissle 1917 maintains remission in ulcerative colitis. Several agents offer promise as primary therapy of ulcerative colitis. Use of probiotics in Crohn disease remains unsubstantiated. Animal models demonstrate marked differences in responses among various probiotic bacterial species and that nonviable organisms can have therapeutic efficacy. Probiotics have multiple mechanisms of action, including prevention of pathogenic bacterial growth, binding to or penetration of pathogens to mucosal surfaces, stimulation of mucosal barrier function, or altering immunoregulation (decreasing proinflammatory and promoting protective molecules). Although multiple probiotic species block epithelial adhesion and invasion by microbial pathogens in vitro, their proven utility in clinical infections is limited to accelerating recovery from acute infectious diarrhea and preventing antibiotic-associated diarrhea.
Probiotics offer promise for physiologic, nontoxic treatment of pouchitis, ulcerative colitis, and acute infectious diarrhea, but larger, controlled clinical studies must be performed to clarify optimal agents; doses; combinations of various probiotics, prebiotics, and antibiotics; and therapeutic conditions.