The term opportunistic fungi is vague. Generally, any fungal species
is capable of causing infection under favorable conditions. Over one
million fungal species exist in nature. Only a few hundred of them have
been associated with human and animal infections. Opportunistic fungi
refers to those fungi that normally would not cause infections in otherwise
healthy people but are able to cause infection under certain circumstances
such as immunodefficiency, cancer, organ transplant, neutropenic patients,
diabetes, debilitated patients and patients on long term antibiotics.