Scedosporium apiospermum/boydii is more of a moderately rapid growing dematiaceous mold whose conidia lack septae. Its hyphae are nonpigmented but its microconidia (seen only in culture) are melanized. The mold has a light gray or brown surface in either state. S. boydii is intrinsically resistant to amphotericin B but is usually susceptible to broad-spectrum triazoles such as voriconazole and posaconazole.
Lomentospora prolificans has a gray or black surface and reverse. Its growth is inhibited by cycloheximide and it has no sexual state. The microconidia are oval and truncated, forming clusters at the end of annelids (conidiogenous cells). The annelids have swollen bases and thin necks. L. prolificans is intrinsically resistant to amphotericin B as well as the azoles and echinocandins, which makes antifungal therapy ineffective.
The image to the right shows an S. boydii lactophenol cotton blue preparation demonstrating smooth-walled, unicellular conidia that were branching singly from the conidiophore.
Image courtesy of the CDC.
