Mycotic Agents of Human Disease
Traditional distinctions regarding inherent virulence and portal of infection provide a useful starting point for considering the pathogenic fungi. Discussion of fungal agents of human disease in this chapter is organism based rather than disease based. This discussion is not exhaustive for all documented fungal pathogens, but instead seeks to address those fungi that are seen with regularity in clinical and environmental mycology laboratories. The Public Health Security and Bioterrorism Preparedness and Response Act of 2002 required establishment of regulations regarding the possession, use, and transfer of select biological agents and toxins. Only one fungal genus, Coccidioides, contains species pathogenic for humans and other animals and is classified as requiring Biosafety level (BSL)-3 containment precautions. Coccidioides immitis recently was split into two species based on DNA analysis. The two species, C. immitis and Coccidioides posadasii, have identical potential for causing infection, disease, and death in humans and other animals. Containment and biosafety issues are more problematic for molds than for yeasts because molds have evolved the capacity to form airborne spores routinely as a dispersal mechanism. Dematiaceous fungi can cause infection when traumatically inoculated to skin and subcutaneous tissue, and disease from inhaled spores is possible as well. In contrast to fomite specimens, medical specimens pose little hazard of airborne fungal infection. Routine containment practices for specimen handling and processing provide sound protection for laboratory personnel as well as protection of specimens and cultures from extraneous contamination.
