The incidence of gastrointestinal infections is very high. In Western countries at least 30% of the population suffers from at least one food-borne infection per year. Mostly because of the problem of antibiotic resistance, more emphasis is put on prevention of infections. One of the possibilities is to strengthen human resistance to gut infections by consumption of probiotics. A specific blend of probiotic lactic acid bacteria (Lactobacillus helveticus Rosell-52, Lactobacillus rhamnosus Rosell-11, Bifidobacterium longum Rosell-175) and a probiotic yeast (Saccharomyces boulardii), improved stool consistency and shortened the duration of diarrhea in a rat model of E.coli-induced diarrhea. These probiotics showed synergistic effects compared with administration of solely S. boulardii or a mixture of L. helveticus Rosell-52, L. rhamnosus Rosell-11, B. longum Rosell-175. Consumption of S. boulardii and a combination of L. helveticus Rosell-52, L. rhamnosus Rosell-11 reduced diarrhea in humans.