Diseases Caused by Fungi

In a eukaryotic kingdom of their own, fungi have interactions with humans ranging from colonization of skin by dermatophytes to local invasion of mucous membranes and deeper invasion with hematogenous dissemination. Various fungi are normal flora (e.g., Candida), opportunists that infect only persons with compromised host defenses (e.g., Aspergillus), and dimorphic organisms that are spore-forming molds in nature and convert into yeasts after entry as often occurs by inhalation (e.g., Histoplasma). Dimorphic fungi are capable of causing infections even in immunocompetent persons. The most frequently detected fungal structures in infected hosts are hyphae and budding yeast. Although detection of fungi invading tissue contributes to diagnosis, culture and mycologic identification provide a definitive answer.