Comparative evaluation of Sensititre YeastOne and CLSI M38-Ed3 reference method for determining echinocandin minimum effective concentrations against Aspergillus isolates

Abstract

ABSTRACT The minimum inhibitory concentration (MIC) of echinocandins against Aspergillus spp. does not represent the actual inhibition threshold of echinocandins. Therefore, the recommended method to evaluate their activity is determining the minimum effective concentration (MEC) in broth microdilution, a method that is less common in clinical settings. This study aimed to assess a user-friendly commercial method, Sensititre YeastOne (SYO), to determine the effectiveness of echinocandins (caspofungin, anidulafungin and micafungin) against Aspergillus spp. Echinocandins MEC was determined against 23 isolates of Aspergillus spp. using SYO and the reference Clinical and Laboratory Standards Institute (CLSI) method. MECs were read with an inverted microscope and a reading mirror. Essential agreement (EA) between the tested methods was defined as a ±twofold dilution difference. There was a high EA (91%–100%) between the reference method and SYO in determining echinocandins MEC against Aspergillus isolates using inverted microscopy. A high EA was also observed between SYO MEC determined by inverted microscopy and a reading mirror, but different incubation times were required. SYO is a reliable, simple method for determining the MEC of echinocandins against Aspergillus isolates, preferably with an inverted microscope, and can be easily used in clinical laboratories when echinocandin susceptibility testing is required. IMPORTANCE Using a commercial method such as Sensititre YeastOne (SYO) to determine the minimum effective concentration (MEC) of echinocandins against Aspergillus spp. has been shown to be a reliable alternative to the Clinical and Laboratory Standards Institute (CLSI) reference method. This makes it more suitable for high-volume clinical laboratories. SYO provides accurate results comparable to the standard method and could potentially improve patient care by guiding more optimal antifungal treatment choices for patients with Aspergillus infections.