Candida species were once largely regarded merely as causes of aggravating, but rarely life-threatening mucocutaneous infections such as thrush, vulvovaginitis, and intertrigo. Now, however, Candida species have assumed the role of major nosocomial pathogens. This change has paralleled the advent of aggressive cancer chemotherapy, the widespread use of parenteral nutrition, and the practice of advanced surgical techniques including cardiovascular procedures.
Candida is a heterogeneous genus presently grouped with the Fungi Imperfecti (Deuteromycetes). There are over 80 species of Candida; only seven, however, have been recovered from humans: Candida albicans, Candida tropicalis, Candida pseudotropicalis, Candida guilliermondi, Candida krusei, Candida parapsilosis, and Candida stellatoidea. Approximately 90% the systemic Candida infections are due to C. albicans; most of the remaining infections are due to C. tropicalis. Candida species are normal commensals of humans. They are commonly found on the skin, in the gastrointestinal tract, sputum, the female genital tract, and urine from catheterized bladders. C. albicans is found only in human beings and in animal reservoirs. In other sites, such as hospital environments, Candida probably represents contamination by human excreta. Other Candida species may be cultured from soil and other environmental locations. Unlike Aspergillus species, Candida species are uncommon laboratory contaminants.