Survival of Candida auris on environmental surface materials and low-level resistance to disinfectant

Background: Candida auris persists in the environment despite disinfection. Its survival on various environmental surfaces and the effect of sublethal concentrations of disinfectants on C. auris has not been studied. Aim: To investigate the survival of C. auris on environmental surfaces, and the effect of sublethal concentrations of disinfectants. Methods: Surface material blocks were fabricated and artificially contaminated with C. auris. Viable counts were assessed for 3 weeks. In addition, C. auris cells were pulsed daily with disinfectants for 15 days, and minimum inhibitory concentrations (MICs) were determined. Ergosterol quantities and efflux pump assays were performed on disinfectant-exposed strains using standard methods. Results: C. auris survived on all the surfaces for >3 weeks, with the lowest count of 2.3 log colony-forming units, regardless of wet or dry conditions. Wet wood supported the growth of C. auris (a 1 log increase), whereas dry wood inhibited this organism (both P<0.01). In the biofilm form, C. auris flourished on all surfaces. Although the MICs increased in C. auris cells pulsed with sodium dichloroisocyanurate and benzalkonium chloride, only C. auris exposed to benzalkonium chloride showed decreased ergosterol content and an activated efflux pump. Conclusions: Although C. auris survived on all tested surfaces, survival on wet wood was remarkable. C. auris pulsed with benzalkonium chloride developed some degree of tolerance to disinfectant and showed efflux pump activation, suggesting the development of low-level resistance.