Candida auris clade I isolates from ear discharge in Japan demonstrated comparable virulence to invasive clade I isolates against Galleria mellonella.

INTRODUCTION

Candida auris is one of the most serious fungal pathogens in the world due to its characteristics of multidrug resistance and causing outbreaks in hospitals. Based on genetic analysis through whole-genome sequencing, C. auris has been classified into four major clades. In Japan, most strains were isolated from noninvasive ear discharge and classified into clade II, whereas clades I, III, and IV are typically detected in patients with invasive candidiasis worldwide. However, three strains, NIIDFCaurisB0004, LSEM 3732, and LSEM 4020, were isolated from ear discharge in Japan and classified into clade I, and their virulence remains unknown. Here, we demonstrate the virulence of these ear discharge-derived clade I strain using the Galleria mellonella infection model.

METHODS

Survival analysis, histopathological analysis, and colony count measurements of G. mellonella larvae infected with C. auris were conducted to compare the virulence of ear discharge-derived clade I strains, ear discharge-derived clade II strains, and non-ear discharge-derived clade I strains.

RESULTS

Ear discharge-derived clade I strains exhibited higher mortality rates than ear discharge-derived clade II strains, comparable to those of invasive clade I strains. Histopathological analysis and colony count measurements revealed that the ear discharge-derived clade I strain, NIIDFCaurisB0004, exhibited significantly more growth than clade II strains in G. mellonella.

CONCLUSION

Even if C. auris is isolated from ear discharge in Japan, there exists a possibility that it can be classified into clade I with high virulence. Therefore, detailed identification of the clade is essential.