Candida auris: a fungus with identity crisis

Abstract

Candida auris is a new fungal species that has puzzlingly and simultaneously emerged on five continents. Since its identification in 2009, the scientific community has witnessed an exponential emergence of infection episodes and outbreaks in healthcare facilities world-wide. Candida auris exhibits several concerning features compared to other related Candida species, including persistent colonization of skin and nosocomial surfaces, ability to resist common disinfectants and to spread rapidly among patients. Resistance to multiple drug classes and misidentification by available laboratory identification systems has complicated clinical management, and outcomes of infection have generally been poor with mortality rates approaching 68%. Currently, the origins of C. auris are unclear, and therefore, it is impossible to determine whether environmental and climactic changes were contributing factors in its recent emergence as a pathogen. Nevertheless, a robust response involving rapid diagnostics, prompt interventions and implementation of precautions, are paramount in curtailing the spread of infections by this fungal species. Importantly, there is a pressing need for the development of new antifungal drugs. In this article, we present a brief overview highlighting some of the important aspects of C. auris epidemiology, pathogenesis and its puzzling global emergence.

Keywords: Candida auris; drug resistance; fungal pathogen; global emergence; high mortality; hospital outbreaks.

Figure 1.

Geographical and clade distribution of C. auris cases and outbreaks world-wide. Red circles denote reported outbreaks; concentric circles indicate more than one outbreak, and red star (Japan) indicates location where first identified C. auris isolate was recovered in 2009.

Figure 2.

Candida auris morphology and biofilm formation. (A) 3D reconstructed confocal laser scanning microscopy image of C. auris yeast cells. Cell wall chitin stained with calcofluor white (blue); cell wall polysaccharides stained with concanavalin-A (fuchsia); white arrows: budding scars with higher polysaccharide content. Objective magnification: 63x; cropped representative area. (B) Representative scanning electron microscopy (SEM) image of an in vivo-grown C. auris biofilm. Infected fragments of intravascular catheters were implanted subcutaneously in dorsum of mice and biofilms were allowed to form for 72 h. SEM analysis demonstrated the formation of a mature C. auris biofilm within the lumen of the catheter consisting of yeast cells and extracellular polysaccharide matrix (red arrow). Bar = 10 µm.