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Mycoses

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	Dimorphic Systemic

		Blastomycosis

		Coccidioidomycosis

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		Paracoccidioidomycosis

	Opportunistic

Fungal Descriptions

Laboratory Methods

Dimorphic

School of Molecular & Biomedical Science
THE UNIVERSITY OF ADELAIDE
AUSTRALIA 5005

Contact:
Dr David Ellis

Email

Telephone:
+61 8 8161 6459
Facsimile:
+61 8 8161 7589

Dimorphic Systemic Mycoses

These are fungal infections of the body caused by fungal pathogens which can overcome the physiological and cellular defences of the normal human host by changing their morphological form. They are geographically restricted and the primary site of infection is usually pulmonary, following the inhalation of conidia.

Disease	Causative organisms	Incidence
Histoplasmosis	Histoplasma capsulatum Histoplasma dubosii	Rare*
Coccidioidomycosis	*Coccidioides immitis*	Rare*
Blastomycosis	*Blastomyces dermatitidis*	Rare*
Paracoccidioidomycosis	*Paracoccidioides brasiliensis*	Rare*
Sporotrichosis	*Sporothrix schenkii*	Rare
Penicilliosis marnefffei	*Penicillium marneffei*	Rare*

*more common in endemic areas.

Histopathology is especially useful and is one of the most important ways of alerting the laboratory that they may be dealing with a potential pathogen.

Tissue morphology of dimorphic pathogens:

Mycosis	Tisue morphology
Blastomycosis	Large broad base unipolar budding yeast cells (8-10um).
Coccidioidomycosis	Spherules (10-80um) with endospores (2-5um).
Histoplasmosis	Small narrow base budding yeast cells (1-5um; 5-2um in var. duboisii)
Paracoccidioidomycosis	Large narrow base, multi-budding yeast cells (20-60um).
Sporotrichosis	Small narrow base budding yeast cells (2-5um).

WARNING: Cultures of Blastomyces dermatitidis, Coccidioides immitis and Histoplasma capsulatum represent a severe biohazard to laboratory personnel and must be handled with extreme caution in an appropriate pathogen handling cabinet.

In the past microscopic morphology, conversion from the mould form to the yeast or spherule form, and animal pathogenicity have all been used; however exoantigen tests are now the method of choice, at least for Blastomyces dermatitidis, Coccidioides immitis and Histoplasma capsulatum.

Australian Guidelines for use of antifungal agents in treatment of invasive fungal infection (July 2003).