Infection by Different Clades of Candidozyma auris in a Galleria mellonella Model: Determining Virulence Levels

Candidozyma auris (formerly Candida auris) is an emerging yeast that causes bloodstream infections, especially in immunocompromised patients, and presents high resistance and virulence rates. To date, six clades have been established worldwide and the number of outbreaks caused by this microorganism has been increasing every year, causing concern in the medical community. Therefore, this study investigated the heterogeneity among clades of C. auris by evaluating the virulence profile and mechanism of infection using an in vivo model of Galleria mellonella.

G. mellonella was infected with different clades (I, II, III and IV) of C. auris, C. albicans ATCC 5341 and C. parapsilosis ATCC 22019 for virulence and histopathologic evaluation.

Aggregative strains of C. auris InP13 (I) and VEN C6 (IV) had a greater rate of melanization and larval mortality among the C. auris isolates, therefore, being the most aggressive strains. C. albicans caused the most melanization among all strains at the highest inoculum concentration (10⁶ cells/mL). Histopathologic examination showed a greater number of granulomas in the lower and upper extremities of G. mellonella. The granulomas ranged from 0.07-0.11 nm in diameter. All strains showed biofilms adhering to larval tissue, which was more evident for InP13, VEN C6 and C. albicans. Infiltration of tissues by yeasts, pseudohyphae and chlamydospores (a resistance structure formed by C. albicans in stress environments) morphotypes were observed.

The aggregative strains were more virulent and had a greater ability to form biofilms and granulomas, showing heterogeneity among the different C. auris clades.