Probiotics and prebiotics in clinical practice.

Probiotics are living organisms that have a beneficial therapeutic effect on the host when ingested. The bacteria Lactobacillus GG and the yeast Saccharomyces boulardii have been shown in controlled trials to prevent antibiotic-associated diarrhea. Prebiotics are non-living, indigestible polysaccharides metabolized in the intestine that induce physical and bacteriologic musocal modifications. Rather than introducing exogenous bacteria into the intestinal millieu, prebiotics stimulate certain indigenous bacteria already resident in the gut.