Manual of Clinical Microbiology


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

Last Updated:2023

The dimorphic fungi causing systemic disease belong to the class Eurotiomycetes, order Onygenales (1). The Onygenales share several general characteristics: their sexual stages (teleomorphs) form rudimentary asci surrounded…

Description of the Agents

H. capsulatum is a thermally dimorphic fungus, displaying a filamentous mold form in the environment and in culture at temperatures below 35°C and a yeast phase in tissue and at…

Epidemiology and Transmission

Inhalation of microconidia is the usual mode of H. capsulatum infection in humans. The incubation period is 1 to 3 weeks. In cases of reinfection, the incubation period appears to…

Clinical Significance

There is a wide spectrum of clinical manifestations of histoplasmosis, ranging from a transient pulmonary infection that subsides without treatment to chronic pulmonary infection or to more widespread disseminated disease…

Collection, Transport, and Storage of Specimens

Methods of collection, transport, and storage of specimens are detailed in chapter 118. Tissue samples should be obtained when appropriate and should be divided and submitted for microbiological and histopathological…

Direct Examination

Direct microscopic examination of clinical materials may provide a rapid presumptive diagnosis of a systemic fungal infection. However, it is important to appreciate that tissue‐form cells of Histoplasma and Blastomyces

Isolation Procedures

The mere lifting of a culture plate lid is often sufficient to cause the release of large numbers of conidia into the air, and screw‐cap tubes or sealed plates should…


In general, these organisms may be identified by their characteristic morphologic features, including conversion to the yeast phase, although this is infrequently done in clinical laboratories, and identification is more…

Typing Systems

In general, typing systems have been used to show geographic differences among isolates and cryptic species. In some genera, diversity can be shown among isolates collected from a single geographic…

Serologic Tests

Serologic tests for endemic mycoses are available as kits for in‐house testing or as laboratory‐derived tests at specialized testing centers…

Antimicrobial Susceptibilities

Established treatment options for Histoplasma, Blastomyces, Emergomyces, Coccidioides, and Paracoccidioides species include amphotericin B and the triazoles voriconazole, posaconazole, itraconazole, and fluconazole. Isavuconazole, a new triazole, has ...

Evaluation, Interpretation, and Reporting of Results

The definitive diagnosis of histoplasmosis can be accomplished by direct microscopic detection of H. capsulatum yeast cells in clinical specimens or its isolation in culture. However, isolation and identification may…

Section Editor: Sean Zhang

Volume Editor: Bobbi S. Pritt

Editors in Chief: Karen C. Carroll and Michael A. Pfaller

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