Candida albicans Commensalism and Human Diseases

Abstract

Candida albicans is by far the most prevalent commensal yeast and frequently causes opportunistic infections in humans. This polymorphic fungus resides as a lifelong, harmless commensal on mucosal surfaces of the oropharynx, gastrointestinal, and genitourinary tracts in healthy individuals, but causes a frequently fatal disseminated infection responsible for multiple forms of disease in immunocompromised patients, including oral, vaginal, dermal, and disseminated candidiasis. Although C. albicans colonization can be detected in humans as early as a few weeks after birth, our understanding of its commensal adaptation has arisen only recently from the most basic level. C. albicans commensalism requires a homeostatic interplay among fungus, resident microbiota, and host immunity, and disturbance of the balance can lead to pathogenicity of the yeast. This chapter describes a number of important factors contributing to the maintenance of this interaction and summarizes recent progresses regarding mechanisms underlying the regulation of C. albicans colonization in various host niches.