This CLSI rationale document is based on the need for guidance on the interpretation of antifungal agents for invasive infections caused by Candida spp.

Candida spp. are common causes of invasive disease in both immunocompromised and immunocompetent hosts. Rezafungin is the most recent echinocandin developed that demonstrates in vitro activity against Candida spp. in patients with invasive infections caused by these fungi. However, mutations in FKS1 and FKS2 genes are known to have higher minimal inhibitory concentrations (MICs) to the echinocandins, including rezafungin, and contribute to clinical failure. Therefore, antifungal susceptibility guidance is needed to alert clinicians to the likelihood of resistance, so that alternate therapeutic strategies can be considered.