Candida auris phenotypic heterogeneity determines pathogenicity in vitro

Abstract

Candida auris is an enigmatic yeast that provides substantial global risk in healthcare facilities and intensive care units. A unique phenotype exhibited by certain isolates of C. auris is their ability to form small clusters of cells known as aggregates, which have been to a limited extent described in the context of pathogenic traits. In this study, we screened several non-aggregative and aggregative C. auris isolates for biofilm formation, where we observed a level of heterogeneity amongst the different phenotypes. Next, we utilised an RNA-sequencing approach to investigate the transcriptional responses during biofilm formation of a non-aggregative and aggregative isolate of the initial pool. Observations from these analyses indicate unique transcriptional profiles in the two isolates, with several genes identified relating to proteins involved in adhesion and invasion of the host in other fungal species. From these findings we investigated for the first time the fungal recognition and inflammatory responses of a three-dimensional skin epithelial model to these isolates. In these models, a wound was induced to mimic a portal of entry for C. auris. We show both phenotypes elicited minimal response in the model minus induction of the wound, yet in the wounded tissue both phenotypes induced a greater response, with the aggregative isolate more pro-inflammatory. This capacity of aggregative C. auris biofilms to generate such responses in the wounded skin highlights how this opportunistic yeast is a high risk within the intensive care environment where susceptible patients have multiple indwelling lines. ImportanceCandida auris has recently emerged as an important cause of concern within healthcare environments due to its ability to persist and tolerate commonly used antiseptics and disinfectants, particularly when surface attached (biofilms). This yeast is able to colonise and subsequently infect patients, particularly those that are critically ill or immunosuppressed, which may result in death. We have undertaken analysis on two different types of this yeast, using molecular and immunological tools to determine whether either of these has a greater ability to cause serious infections. We describe that both isolates exhibit largely different transcriptional profiles during biofilm development. Finally, we show that the inability to form small aggregates (or clusters) of cells has an adverse effect on the organisms immuno-stimulatory properties, suggestive the non-aggregative phenotype may exhibit a certain level of immune evasion.