Microbes could represent the future of medicine

Not all bacteria are bad. In fact, beneficial microbes could represent the future of medicine, with the potential to treat a variety of diseases in humans and animals from diarrhea and eczema to gum disease and autoimmune disorders, according to a report released by the American Academy of Microbiology, Probiotic Microbes: The Scientific Basis.

"Theoretically, beneficial microorganisms could be used to treat a range of clinical conditions that have been linked to pathogens, including gastrointestinal problems like irritable bowel syndrome and inflammatory bowel disease, oral diseases like tooth decay and periodontal disease, and various other infections, including vaginal infections and possibly skin infections. Probiotics could also conceivably be put to use in preventing disease or thwarting autoimmune disorders. A number of these possibilities are being explored in research labs and hospitals around the world," says Richard Walker of the Food and Drug Administration, a co-chair of the steering committee that produced the report.

Probiotics can help prevent and treat disease through a number of mechanisms. One way is by interacting directly with the disease-causing microbes, making it harder for them to cause disease. An example of this is the ingestion of probiotic bacteria to prevent or treat diarrhea. The organisms help reinforce the natural bacterial barrier that exists on the lining of the digestive tract providing additional protection against pathogenic organisms that can cause diarrhea.

"Several probiotics have been shown to shorten the duration of acute watery diarrhea caused by rotavirus in children. Other causes of diarrhea may also be addressed through probiotics," says Carol Wells of the University of Minnesota, a member of the steering committee.

Another example of microbe-microbe interaction in probiotics is a phenomenon known as "competitive exclusion" in which beneficial microbes directly compete with disease-causing microbes for food and other resources, eventually crowding them out. One potential application of competitive exclusion would be colonizing the mouth with beneficial bacteria to prevent the growth of bacteria that cause cavities and gum disease.

Probiotics also help prevent disease by interacting with and strengthening the immune system.

"Exposure to commensal organisms is necessary for the appropriate development of both the innate and acquired immune systems. Once established, probiotic organisms interact with these immune defenses, possibly changing the nature of the immune response to other antigens, including commensal and pathogenic organisms," says Walker.

The report is the outcome of a colloquium convened by the American Academy of Microbiology in November 2005 to discuss the current state of knowledge regarding probiotics. Participants with expertise in microbiology, medicine, periodontics, animal science, immunology, nutrition and other fields met to discuss a variety of issues associated with the field of probiotics. In addition to providing an overview of the current state of and potential for probiotic research, the report also offers specific recommendations to help advance the field.

In addition to those listed above, some other potential future applications of probiotics identified in the report include treating antibiotic-resistant infections, encouraging weight gain in newborns and children with AIDS, reducing the incidence of kidney stones, and reducing the recurrence of bladder tumors.