Candidozyma auris is a multidrug resistant fungal pathogen classified by the World Health Organization (WHO) as a critical priority species. Broth microdilution (BMD) is the recommended reference method for antifungal susceptibility testing (AFST), with interpretation based on tentative breakpoints proposed by the Centers for Disease Control and Prevention (CDC) and, more recently, EUCAST clinical breakpoints published in 2025. However, automated systems such as VITEK 2 currently lack validated susceptibility interpretations for C. auris . This study aimed to evaluate the performance of the VITEK 2 system for AFST of C. auris isolates by comparison with the BMD method and to assess the impact of applying CDC and EUCAST breakpoints on susceptibility interpretation. Antibiotic susceptibility testing (AFST) was performed simultaneously on 88 C. auris isolates using the VITEK 2 system and the BMD method. Susceptibility results were interpreted according to both CDC and EUCAST clinical breakpoints. The clade distribution of the isolates was determined by multiplex PCR. All isolates were identified as clade I. Categorical agreement (CA) between VITEK 2 and BMD was 31.8% for amphotericin B, 76.1% for fluconazole, and 92.0% for both caspofungin and micafungin. Based on CDC breakpoints, no very major errors (VME) were observed for amphotericin B, caspofungin, or micafungin using VITEK 2, whereas a VME rate of 15.0% was detected for fluconazole. Major error (ME) rates for VITEK 2 were 93.7% for amphotericin B, 68.7% for fluconazole, and 7.9% for caspofungin and micafungin, all exceeding the acceptable performance threshold (ME ≤ 3%). Concordance between CDC- and EUCAST-based interpretations was high for micafungin (VITEK 2: 93.1%; BMD: 96.5%) but markedly lower for amphotericin B (VITEK 2: 59.0%; BMD: 27.2%). In conclusion, VITEK 2 showed a high level of agreement with the BMD method in the echinocandin susceptibility test of C. auris , while very high ME and VME ratios were observed for amphotericin B and fluconazole. These findings indicate that VITEK 2 amphotericin B and fluconazole AFST results should be interpreted carefully and validated using reference methods. Furthermore, the differences between CDC and EUCAST breakpoint interpretations, particularly for amphotericin B, highlight the significant impact of breakpoint selection on antifungal susceptibility categorization in C. auris .
Aydemir et al. (Tue,) studied this question.