LAUSR

Abstract Background Rezafungin is a novel echinocandin with excellent activity against common Candida species; however, limited data are available regarding rare Candida species. Methods We determined the in vitro susceptibility of 689 clinical isolates of 5 common and 19 rare Candida species, as well as Saccharomyces cerevisiae. The activity of rezafungin was compared with that of anidulafungin, caspofungin, micafungin, amphotericin B and fluconazole, using CLSI broth microdilution methodology (Fourth Edition: M27). Results Rezafungin MIC90 values were 0.06 mg/L for Candida albicans (n=125), Candida tropicalis (n=51), Candida dubliniensis (n=22), Candida inconspicua (n=41), Candida sojae (n=10), Candida lipolytica (n=10) and Candida pulcherrima (n=10), 0.12 mg/L for Candida glabrata (n=81), Candida krusei (n=53), Candida kefyr (n=52) and Candida fabianii (n=15), 0.25 mg/L for Candida lusitaniae (n=46) and Candida auris (n=19), 0.5 mg/L for Candida metapsilosis (n=15) and S. cerevisiae (n=21), 1 mg/L for Candida orthopsilosis (n=15) and Candida guilliermondii (n=27) and 2 mg/L for Candida parapsilosis sensu stricto (n=59). Caspofungin MIC90 values were 0.25–2 mg/L for all species, while micafungin and anidulafungin MIC90 values were similar to those of rezafungin. Fluconazole resistance was found in C. albicans (5.6%) and C. glabrata (4.9%); rezafungin was effective against these isolates as well. Amphotericin B MIC values did not exceed 2 mg/L. Conclusions Rezafungin showed excellent in vitro activity against both WT and azole-resistant Candida species, as well as against S. cerevisiae. Rezafungin had similar activity to other echinocandins (excluding caspofungin) against common Candida species and, notably, against clinically relevant uncommon Candida species.