Candida spp. are usually present as part of normal flora onhealthy mucosal surface of the oral cavity, gastrointestinal tract, and vagina. Candida shows colonization at these sites in more than 80% of healthy people. The organism, however, is rarely present on the surface of normal human skin, except occasionally from certain intertriginous area, such as the groin.
Under certain conditions, Candida gains access to systemic circulation from the oropharynx of the gastrointestinal tract. Colonization of the mucocutaneous surface is the first stage in the pathogenesis of Candidal infection. The fungus causes invasion in human tissue through different routes. Disruption of the skin or mucosa allows the organism access to the blood stream. Massive colonization with large numbers of Candida also permits the organism to pass directly into the blood stream, causing the infection.
In immunocompromised hosts, Candida may disseminate to many organs, such as lung, spleen, liver, heart, and brain. Candida may induce inflammation of the eye, causing endophthalmitis and also may involve skin in 10–30% of patients with dissemi- nated infection. Deficiency in host defence mechanisms plays a significant role in development of Candida infection.
Both cell-mediated and humoral antibodies confer protection against Candida in healthy adults. Cell-mediated immunity (CMI) is, however, most important. Alteration in CMI may cause extensive superficial candidiasis, despite having normal or elevated humoral antibodies. The humoral antibodies appear to play minimal role in protection against the disease. Humoral antibodies confer protection against Candida in healthy adults.