As infection control faces new challenges from emerging, multidrug resistant strains of the yeast Candida auris, this study was conducted in order to examine the efficacy of hospital surface disinfectants and a new water disinfectant against C. auris biofilm forms.

We tested four reference strains of C. auris (NCPF8971, NCPF8977, NCPF8984, DSM21092) and one C. albicans strain (ATCC10231) against disinfectants based on ethanol (ETH), quaternary ammonium (QAC), a combination of glutaraldehyde, quaternary ammonium and surfactant (ALD) and potassium peroxymonosulfate (PP) as well as 3.4% H₂O₂ and 4.25% H₂O₂ alone. In addition, a micellic-based formulation containing 17% v/v hydrogene peroxide disinfectant (mH₂O₂) was tested. The efficacy of the disinfectants was measured in a 96-well plate using tetrazolium salt reduction (XTT) and the log₁₀ reduction assay.

ETH and QAC displayed in clinically recommended concentrations more than 5log₁₀ reduction and more than 80% XTT activity reduction for all of the Candida biofilms and planktonic cells. Only biofilms of C. auris NCPF8984 were additionally sensitive to all remaining disinfectants. All tested C. auris biofilms were sensitive to PP disinfectant and showed more than 5log₁₀ reduction. However, the XTT assay showed a reduction of less than 80% for the PP disinfectant, indicating the presence of active but non-culturable cells. The 25% mH₂O₂ (corresponding to 4.25% H₂O₂) killed Candida biofilms after 1 minute.