Caspofungin-Resistant Candida tropicalis Strains Causing Breakthrough Fungemia in Patients at High Risk for Hematologic Malignancies

We identified three cases of C. tropicalis strains causing breakthrough fungemia in allogeneic stem cell recipients receiving caspofungin prophylaxis and treatment. Three genetically unrelated isolates with high echinocandin MICs were identified. Each strain carried a characteristic mutation conferring an amino acid substitution within Fks1p hot spot 1.