Discovery of the Diploid Form of the Emerging Fungal Pathogen Candida auris

The new multidrug-resistant
pathogen Candida auris was first described
in 2009 in Japan and has emerged in many countries
worldwide. This human fungal pathogen has long been considered a haploid
fungus. Here, we report the discovery of the diploid form and spontaneous
ploidy shifts in clinical isolates of C. auris. Haploid and diploid cells of C. auris differ in several aspects including growth rates, virulence, and
global gene expression profiles. For example, diploid cells exhibit
a slower growth rate than haploid cells in in vitro culture media; however, they are more virulent than haploid cells
in a mouse systemic infection model. Global transcriptional expression
analysis demonstrates that both haploid and diploid cells express
a set of ploidy-enriched genes, which are involved in the regulation
of metabolism, cell wall maintenance, translation and DNA replication,
and other important biological processes. Antifungal susceptibility
testing shows that haploid and diploid cells exhibit similar responses
when treated with a number of antifungals. Taken together, haploid
and diploid cells may have different fitness responses to diverse
niches, and ploidy changes could be an adaptive strategy of C. auris to environmental changes. Our findings shed
new light on the biology and pathogenesis of this emerging fungal
pathogen.