Closing the Brief Case: “Great Pretender”—Disseminated Blastomycosis in Western North Carolina

Abstract

1. Which of the following stains are not used to visualize Blastomyces spp.? a. Gomori methenamine silver (GMS) stain b. Periodic acid-Schiff (PAS) stain c. Calcofluor white with potassium hydroxide d. Ziehl-Neelsen stainAnswer: d. Gomori methenamine silver and periodic acid-Schiff are used to visualize Blastomyces during histopathology. Calcofluor white with potassium hydroxide is used to stain direct specimens. Ziehl-Neelsen is used for the identification of mycobacteria and not used for the identification of endemic fungi. 2. How is Blastomyces species infection usually acquired? a. Through cutaneous direct inoculation b. Inhalation of conidia c. Bloodstream spread after trauma d. Animal biteAnswer: b. Although direct inoculation is possible, the most common way of acquiring blastomycosis is through inhalation of the conidia. Blastomycosis after an animal bite has been described but is not common. 3. Which culture medium is preferred for recovery of Blastomyces spp.? a. Buffered charcoal yeast extract (BCYE) b. Brain heart infusion with sheep’s blood and gentamicin (BHISG) c. MacConkey agar d. Chocolate agarAnswer: b. Blastomyces spp. grow on BHISG, BCYE, and chocolate agar. However, BHISG is preferred due to the enriched growth of Blastomyces spp. and the inhibition of bacterial growth, which is particularly important for nonsterile specimens. The BCYE plate is sometimes included with fungal cultures to allow for the isolation of Nocardia and other aerobic actinomycetes, but any bacterial growth outcompetes Blastomyces spp. on this medium. The MacConkey agar is used for the recovery of enteric Gram-negative bacteria in bacterial cultures and does not support the growth of Blastomyces spp.