Development of Echinocandin Resistance in Candida tropicalis following Short-Term Exposure to Caspofungin for Empiric Therapy

Isolation of two echinocandin-resistant Candida tropicalis strains from endotracheal secretions of a patient following short-term exposure to caspofungin is described. Both strains exhibited resistance to echinocandins by Etest and reference broth microdilution, showing a homozygous S645P mutation within the hot spot 1 (HS-1) region of FKS1 and belonging to a unique multilocus sequence type. Other C. tropicalis isolates collected from patients in the same intensive care unit within a 60-day period were susceptible to echinocandins and contained wild-type FKS1 sequences.