Rezafungin Activity against Contemporary Nordic Clinical Isolates and Determined by the EUCAST Reference Method.

Rezafungin (formerly CD101) is a novel echinocandin in clinical development. EUCAST epidemiological cutoff values (ECOFFs) have not yet been established. We determined the activity of rezafungin and comparators against 1,293 Nordic yeast isolates and 122 Indian isolates and established single-center wild-type upper limits (WT-UL). The isolates (19 spp. and 13 other yeast species) were identified using Chromagar; matrix-assisted laser desorption ionization-time of flight (MALDI-TOF); and, when needed, internal transcribed spacer sequencing. EUCAST E.Def 7.3.1 susceptibility testing included rezafungin, anidulafungin, micafungin, amphotericin B, and fluconazole. WT-UL were established following EUCAST principles for visual and statistical ECOFF setting. target genes were sequenced for rezafungin non-wild-type isolates. EUCAST clinical breakpoints for fungi version 9.0 were adopted for susceptibility classification. Rezafungin had species-specific activity similar to that of anidulafungin and micafungin. On a milligram-per-liter basis, rezafungin was overall less active than anidulafungin and micafungin but equally or more active than fluconazole and amphotericin B against the most common species, except We identified 37 (3.1%) rezafungin non-wild-type isolates of (1.9%), (3.0%), (2.7%), (2.9%), (1.2%), and (14.8%). Alterations in Fks hot spots were found in 26/26 Nordic and 8/18 non-wild-type isolates. Rezafungin displayed broad activity against spp., including Adopting WT-UL established here, few Nordic strains, but a significant proportion of isolates, had elevated MICs with mutations in target genes that conferred echinocandin cross-resistance. mutations raised rezafungin MICs notably less than anidulafungin and micafungin MICs in .