Candida auris is an emerging pathogenic yeast of significant clinical concern because of its frequent intrinsic resistance to fluconazole and often other antifungal drugs and the high mortality rates associated with systemic infections. Furthermore, C. auris has a propensity for persistence and transmission in health care environments. The reasons for this efficient transmission are not well understood, and therefore we tested whether enhanced resistance to environmental stresses might contribute to the ability of C. auris to spread in health care environments. We compared C. auris to other pathogenic Candida species with respect to their resistance to individual stresses and combinations of stresses. Stress resistance was examined using in vitro assays on laboratory media and also on hospital linen. In general, the 17 C. auris isolates examined displayed similar degrees of resistance to oxidative, nitrosative, cationic and cell wall stresses as clinical isolates of C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. krusei, C. guilliermondii, C. lusitaniae and C. kefyr. All of the C. auris isolates examined were more sensitive to low pH (pH 2, but not pH 4) compared to C. albicans, but were more resistant to high pH (pH 13). C. auris was also sensitive to low pH, when tested on contaminated hospital linen. Most C. auris isolates were relatively thermotolerant, displaying significant growth at 47 °C. Furthermore, C. auris was relatively resistant to certain combinations of combinatorial stress (e.g. pH 13 plus 47°C). Significantly, C. auris was sensitive to the stress combinations imposed by hospital laundering protocol (pH >12 plus heat shock at >80 °C), suggesting that current laundering procedures are sufficient to limit the transmission of this fungal pathogen via hospital linen.
Bibliographical noteWe are grateful to Dr. David Stead, Evelyn Argo and Craig Pattison (Aberdeen Proteomics Core Facility) for their expert identification of Candida isolates by MALDI ToF MS, and to Dr Jill King and our colleagues in the Aberdeen Fungal Group for their helpful advice. AJPB and NARG were supported by a programme grant from the Medical Research Council [www.mrc.ac.uk] (grant number MR/M026663/1) and by the Medical Research Council Centre for Medical Mycology and the University of Aberdeen (grant number MR/N006364/1). AJPB was also supported by the UK Biotechnology and Biological Research Council [www.bbsrc.ac.uk] (grant numbers BB/F00513X/1, BB/P020119/1), and AWW by the Scottish Government’s Rural and Environment Science and Analytical Services (RESAS) division. NARG was also supported by grants from the Wellcome Trust [www.wellcome.ac.uk] (grant numbers 075470, 086827, 093378, 097377, 099197, 101873, 102705, 200208). DMM was supported by National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) [www.nc3rs.org.uk] (grant numbers NC/S001557/1 and NC/N002482/1) and the UK Biotechnology and Biological Research Council [www.bbsrc.ac.uk] (grant number BB/P02050X/1). HH was supported by the John Duthie Scholarship from the University of Aberdeen’s Development Trust. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
- Candida auris
- Candida pathogens
- stress resistance
- hospital laundry