DESCRIPTIONS OF MEDICAL FUNGI

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Descriptions of Medical Fungi
Paracoccidioides brasiliensis/lutzii Complex
WARNING: RG-3 organism. Cultures of Paracoccidioides brasiliensis/lutzii represent
a biohazard to laboratory personnel and should be handled with extreme caution in a
Class II Biological Safety Cabinet (BSCII).
Recently P. brasiliensis has been recognised as two species: P. brasiliensis and P.
lutzii (Teixeira et al. 2014, Theodoro et al. 2012). P. brasiliensis/lutzii is geographically
restricted to areas of South and Central America. The two species are morphologically
very similar; conidia of P. lutzii are elongated whereas those from P. brasiliensis are
pyriform. Molecular confirmation is recommended.
Molecular Identification: ITS sequencing is recommended (Imai et al. 2000)
Morphological Description: Colonies grown at 25 O C are slow growing and variable
in morphology. Colonies may be flat, wrinkled and folded, glabrous, suede-like or
downy in texture, white to brownish with a tan or brown reverse. Microscopically, a
variety of conidia may be seen, including pyriform microconidia, chlamydospores and
arthroconidia. However, none of these are characteristic of the species, and most
strains may grow for long periods of time without the production of conidia.
On blood agar at 37 O C, the mycelium converts to the yeast phase and colonies are white
to tan, moist and glabrous and become wrinkled, folded and heaped. Microscopically,
numerous large, 20-60 μm, round, narrow base budding yeast cells are present. Single
and multiple budding occurs, the latter are thick-walled cells that form the classical
“steering wheel” or “mickey mouse” structures that are diagnostic for this fungus,
especially in methenamine silver stained tissue sections.
Key Features: Clinical history, tissue pathology, culture identification with conversion
to yeast phase at 37 O C, however molecular identification is now recommended.
References: McGinnis (1980), Chandler et al. (1980), Rippon (1988), de Hoog et al.
(2000, 2015).
20 µm
20 µm
Paracoccidioides brasiliensis/lutzii showing multiple,
narrow base budding yeast cells “steering wheels”.
Antifungal Susceptibility: P. brasiliensis very limited data (McGinnis et al. 1997).
Antifungal MIC Range µg/mL Antifungal MIC Range µg/mL
AmB 0.03-4 ITRA