Such a breach may be caused by endocrinopathies or immune disorders, or it may be induced iatrogenically. Effective management of the fungal infection requires a concerted effort to uncover and correct the underlying defects. The high degree of innate resistance of humans to fungal invasion is based primarily on the various protective mechanisms that prevent fungi from entering host tissues. Fungal growth is discouraged by the intact skin and factors such as naturally occurring long-chain unsaturated fatty acids, pH competition with the normal bacterial flora, epithelial turnover rate, and the desiccated nature of the stratum corneum. Only when these protective barriers are breached can fungi gain access to, colonize, and multiply in host tissues.
Fungi gain access to host tissues by traumatic implantation or inhalation.
The severity of disease caused by these organisms depends upon the size of the inoculum, magnitude of tissue destruction, the ability of the fungi to multiply in tissues, and the immunologic status of the host. Fungal Factors Most of the fungi that infect humans and cause disease are classified by tissue or organ levels that are primary sites of colonization. These are discussed below. Recently T beigelii and M furfur were implicated as opportunistic agents of disease, particularly in immunosuppressed or otherwise debilitated patients. Patients are accidentally infected with these common organisms via indwelling catheters or intravenous lines.