Candidiasis is an infection that is caused by members of the fungal genus Candida.

The two most common species associated with Candidiasis are Candida albicans and Candida glabrata. Less commonly, but still able to cause the infection, are Candida tropicalis, Candida parapsilosis, Candida guilliermondi, and Candida krusei.

The fungus is a normal resident of the body, typically in the mouth and the gastrointestinal tract. In these habitats, the microorganism normally colonizes the cell surface. In healthy people in the United States, Candida species colonize more than half of these individuals. The presence of the fungus is beneficial. Invading bacteria are recognized by the Candida cells and are destroyed. Thus, the fungi complement the