Histoplasma,Blastomyces,Coccidioides, and Other Dimorphic Fungi Causing Systemic Mycoses

Several of the clinically important thermal dimorphic fungi are closely related and belong to the order Onygenales, which includes the causal agents of histoplasmosis, blastomycosis, coccidioidomycosis, paracoccidioidomycosis, and adiaspiromycosis. This chapter provides a review, with updates on recent developments, of our understanding of the pathogenic fungi responsible for these diseases. Aspects relevant to their detection and characterization are emphasized, including taxonomy and genome sequencing updates, morphology of the pathogens at room temperature and at 37°C, epidemiology and transmission, clinical manifestations of the diseases, and diagnostic methods. Diagnostic topics covered include microscopy identification; special stains; immunological tests for detecting antibodies, antigen(s), and metabolites; nucleic acid detection using molecular methods; identification or typing via examination and phenotypic properties; and interpretation of reports. The chapter also describes isolation of the pathogens, including biosafety and biosecurity recommendations; briefly mentions the antifungal agents available for treatment; and reviews the pathogens' in vitro antifungal susceptibilities.