Yeasts in the Gut: From Commensals to Infectious Agents

Background: Controversy still surrounds the question whether yeasts found in the gut are causally related to disease, constitute a health hazard, or require treatment. Methods: The authors present the state of knowledge in this area on the basis of a selective review of articles retrieved by a PubMed search from 2005 onward. The therapeutic recommendations follow the current national and international guidelines. Results: Yeasts, mainly Candida species, are present in the gut of about 70% of healthy adults. Mucocutaneous Candida infections are due either to impaired host defenses or to altered gene expression in formerly commensal strains. The expression of virulence factors enables yeasts to form biofilms, destroy tissues, and escape the immunological attacks of the host. Yeast infections of the intestinal mucosa are of uncertain clinical significance, and their possible connection to irritable bowel syndrome, while plausible, remains unproved. Yeast colonization can trigger allergic reactions. Mucosal yeast infections are treated with topically active polyene antimycotic drugs. The adjuvant administration of probiotics is justified on the basis of positive results from controlled clinical trials. Conclusion: The eradication of intestinal yeasts is advised only for certain clearly defined indications.