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