Clade-dependent resilience of Candidozyma auris challenges surrogate-based disinfectant testing: implications for efficacy testing of oxidative disinfectants

Abstract

Background Candidozyma auris has emerged as a globally relevant healthcare-associated pathogen characterized by environmental persistence, outbreak potential, and multi-drug resistance. Current yeasticidal disinfectant efficacy testing relies on Candida albicans as the standard surrogate organism. However, emerging evidence suggests that susceptibility may vary by clade, active substance, and formulation, questioning the universal adequacy of surrogate-based testing. Aim The aim of this study was to determine whether C. albicans adequately serves as a surrogate organism for yeasticidal disinfectant efficacy testing against C. auris, with particular focus on oxidative disinfectants, especially peracetic acid–based formulations. Methods A stepwise comparative design was applied. Standardized quantitative suspension testing assessed intrinsic susceptibility differences between C. albicans and C. auris using defined active substances. Subsequently, commercially available oxidative disinfectant products were evaluated under standardized application-relevant conditions. C. auris isolates representing different phylogenetic clades were included to assess clade-dependent susceptibility differences. Findings C. auris showed susceptibility comparable to or greater than that of C. albicans for alcohols, aldehydes, and quaternary ammonium compounds. In contrast, marked differences emerged for peracetic acid–based disinfectants. Several oxidative products demonstrated robust yeasticidal efficacy against all tested organisms, whereas selected peracetic acid–based products showed reduced efficacy against C. auris. The most pronounced differences were observed for clade I isolates. Conclusion Surrogate-based yeasticidal efficacy testing using C. albicans remains appropriate for most disinfectant product groups. However, for selected peracetic acid–based formulations, this approach may not universally provide a reliable assessment. Targeted inclusion of C. auris may therefore refine efficacy testing in selected scenarios.