- Filamentous fungus form
- Moderately slow growth, usually maturing in about 2 weeks but suspect cultures should be held for 8 weeks prior to discarding as negative.
- Exhibits a cottony or downy texture.
- Colonies produce white areal hyphae on the surface which may turn a yellowish to tan colour as the colony ages. The reverse is typically a light tan to brown.
- Yeast form
- Slow to moderate growth
- Best chance for conversion is to mimic human conditions. Fungus on enriched media (Blood Agar or Brain-Heart Infusion (BHI)) incubated in about 6% CO2.
- Yeast form has been described as creamy, heaped or wrinkled, granular to verrucose (with projections). The yeast form is cream to tan in colour.
- The yeast form of Blastomyces dermatitidis is inhibited by cycloheximide.
- Blastomyces dermatitidis produces septate hyphae
- Unbranched conidiophores of rather short, yet varying length extend from the hyphae
- Conidia are hyaline (clear) and are produced singly at the apex of the conidiophore or can develop directly on the hyphae.
- Conidia are unicellular, round to pyriform (tear-drop) in shape (~2 to 10 µm dia.) Conidia at the terminal end of the conidiophore resemble a ‘lollipop’ in structure.
- Yeast-like cells (~8 to 15 µm dia.) exhibit a broad budding base (4 to 5 µm dia.)
- The budding cell usually remains attached to the parent cell, separating only when reaching the same size as the parent.
- Yeast cells have rather thick, refractile walls.
- Older cultures may produce thick-walled chlamydoconidia (7 to 18 µm dia.)
New Content (August 20th, 2014)
Added here are a few more photos taken from a new case. The photos below are from a fine needle aspirate (FNA) specimen taken from the lungs. Material shown is stained using the Periodic Acid Schiff (PAS) stain as well as the Gomori Methenamine Silver Stain (GMS).