Guidance for substantiating the evidence for beneficial effects of probiotics: prevention and management of infections by probiotics.

The rationale for the use of probiotics in the management of infectious diseases is supported by their potential to influence and stabilize the composition of gut microbiota, enhance colonization resistance, and modulate immune function parameters. A literature review was conducted to determine the efficacy of using probiotics in selected infections: 1) infectious diarrhea in infants and children, 2) traveler's diarrhea, 3) necrotizing enterocolitis in infants, 4) Helicobacter pylori infection, 5) respiratory tract infections in adults and children, 6) ear, nose, and throat infections, and 7) infectious complications in surgical and critically ill patients. The different types of infections that have been subject to clinical studies with different probiotics obviously prevent any generic conclusions. Furthermore, the lack of consistency among studies focusing on 1 specific infection, in study design, applied probiotic strains, outcome parameters, and study population, along with the still limited number of studies, preclude clear and definite conclusions on the efficacy of probiotics and illustrate the need for better-aligned study designs and methodology. Exceptions were the management of infectious diarrhea in infants and traveler's diarrhea, antibiotic-associated diarrhea, and necrotizing enterocolitis. Sufficient consistent data exist for these applications to conclude that certain probiotics, under certain conditions, and in certain target populations, are beneficial in reducing the risk of infection. In addition, some evidence exists, although conclusions are premature, for the management of Helicobacter pylori infection and possible reduction of treatment side effects. Certain probiotics may also reduce the risk of various symptoms of respiratory tract infections in adults and children, including ear, nose, and throat infections, although data are currently far too limited to distill any clinical recommendations in this area. Positive but also negative results have been obtained in prevention of infectious complications in surgical and critically ill patients. For future studies it is recommended that researchers provide adequate power, identify pathogens, and report both clinical outcomes and immune biomarkers relating to putative underlying mechanisms.