DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 33
Blastomyces dermatitidis Gilchrist & Stokes
10 μm
Histopathology: Blastomyces dermatitidis tissue sections show large, broad-based,
unipolar budding yeast-like cells, which may vary in size from 8-15 µm, with some
larger forms up to 30 µm in diameter. Tissue sections need to be stained by Grocott’s
methenamine silver method to clearly see the yeast-like cells, which are often difficult
to observe in H&E preparations.
Molecular Diagnostics: A DNA probe assay (AccuProbe, Gen-Probe, Inc., San Diego,
CA) for identification of B. dermatitidis in clinical isolates is available (Scalarone et al.
1992 and Padhye et al. 1994b). However this has limited application as it can be used
only with pure cultures of B. dermatitidis (yeast or mould) (Sidamonidze et al. 2012).
Several conventional PCR assays have been developed for the identification of B.
dermatitidis from clinical specimens (Bialek et al. 2003) and soil (Burgess et al. 2006).
Sidamonidze et al. (2012) developed a real-time PCR targeting the BAD1 (formerly
known as WI-1) gene for the identification of B. dermatitidis in culture and tissue and
Morjaria et al. (2015) used rDNA sequencing for identification from paraffin embedded
tissue.
References: McGinnis (1980), Chandler et al. (1980), Kaufman and Standard (1987),
Rippon (1988), Brown et al. (2013).
Antifungal Susceptibility: B. dermatitidis limited data available (Sugar and Liu
1996, Espinel-Ingroff et al. 2001, Espinel-Ingroff 2003, Gonzales et al. 2005 and
Sabatelli et al. 2006). Antifungal susceptibility testing not recommended.
For treatment options see Clinical Practice Guidelines for the Management of
Blastomycosis (Chapman et al. 2008); MIC µg/mL.
Antifungal Range MIC 90
Antifungal Range MIC 90
FLU 0.125-64 4-16 AmB 0.03-1 0.5
ITRA 0.03->16 0.125-2 VORI 0.03-16 0.25
POSA 0.03-2 0.125 CAS 0.5-8 2