Breakthrough Disseminated Aspergillus ustus Infection in Allogeneic Hematopoietic Stem Cell Transplant Recipients Receiving Voriconazole or Caspofungin Prophylaxis

Aspergillus ustus is an uncommon clinical species which is poorly susceptible to antifungals. We report two cases of A. ustus infections that occurred in allogeneic stem cell transplant recipients while they were receiving either voriconazole or caspofungin. Prolonged use of these new antifungal agents may increase the risk of the emergence of resistant organisms.