Does repeated exposure to hydrogen peroxide induce Candida auris resistance?

To minimize environmental colonization by microorganisms that may persist and thrive in healthcare settings, thus reducing healthcare-associated infections (HAIs), new insights over already known biocides are certainly of relevance. Although the efficacy of hydrogen peroxide (H₂O₂) against the emergent yeast Candida auris is moderately documented, concerns over the potential induction of resistance after repeated exposure do persist. The main objective of the present study was to evaluate the hypothetical induction of Candida auris resistance following 30 days of consecutive exposure to lethal and sublethal concentrations of H₂O₂. Furthermore, the authors aimed to elucidate about the rank of efficacy of H₂O₂ against C. auris comparing to other Candida species and whether different strains of C. auris may display different susceptibilities to H₂O₂.

During the induction of resistance assays, both type strains and clinical isolates of Candida auris, Candida albicans and Candida parapsilosis were exposed repeatedly to defined concentrations of H₂O₂, for 30 days.

After that period, no significant differences were found when comparing the minimal inhibitory concentration values of H₂O₂ in case of the induced strains versus each respective positive control. Moreover, H₂O₂ displayed similar effectiveness against all the tested Candida species and no differences were demonstrated among the distinct strains of C. auris.

The adoption of H₂O₂ solutions in routine protocols in order to promote disinfection standards against Candida auris, improving patient safety and reducing healthcare costs, is certainly welcomed.