The spiked (echinulate) macroconidia seen in Image A is characteristic of the mold form of Histoplasma capsulatum.
The mold form of Coccidioides immitis (Image B) is characterized by the production of arthroconidia that appear alternate staining because each cell is separated by an empty space. When mature, each arthroconidium is swollen centrally, giving a barrel appearance.
Blastomyces dermatitidis produces spherical or oval conidia, each supported by an individual conidiophore ("lollipop" as seen in Image C).
The mold form of
Sporothrix schenckii is recognized by the production of tiny microconidia that are arranged around the tip of a delicate conidiophore as petals on a daisy flower (Image D). Note the delicate nature of the background hyphae in the image, a characteristic common to all the dimorphic fungi.
