Phenotypic Switching in Fungi.

Over the past three decades new fungal diseases have emerged that now constitute a major threat, especially for patients with chronic diseases and/or underlying immune defi ciencies. Despite the epidemiologic data, the emergence of stable drug-resistant or hyper-virulent fungal strains in human disease has not been demonstrated as seen in emerging viral and bacterial infections. Fungi are eukaryotic microbes that capitalize on a sophisticated built-in ability to generate phenotypic variability. This successful strategy allows them to undergo rapid adaptation in response to environmental challenges, such as individual body locations that may exhibit drastic differences in temperature and pH. Rapid microevolution can also confer drug resistance and protect them from the host's immune response. This review explores phenotypic switching in pathogenic fungi, including Candida spp and Cryptococcus spp, and how phenotypic switching contributes to the pathogenesis of fungal diseases.