Usefulness of Chromogenic Media with Fluconazole Supplementation for Presumptive Identification of Candida auris

Introduction:Candida auris is a major threat to public health. Rapid detection is essential for early treatment and transmission control. The use of chromogenic media allows the presumptive identification of this new species. The aim of this study is to describe the morphological characteristics of C. auris colonies on three commercial chromogenic media. Methods: Nineteen C. auris isolates from different countries/clades and 18 isolates of other species were cultivated in CHROMagar (TM) Candida Plus, HiCrome (TM) Candida, CHROMagar-Candida, and fluconazole-supplemented (32 mg/L) CHROMagar-Candida media. Results: On CHROMagar (TM) Candida Plus and HiCrome (TM) Candida, C. auris isolates from Colombia, Venezuela, India, Korea, and Japan displayed blue-shaded colonies, while isolates from Spain and Germany exhibited light pink shades with a bluish halo. All isolates showed white to pink colonies on CHROMagar-Candida. On CHROMagar Candida supplemented with fluconazole, whilst C. auris, C. glabrata, or C. krusei showed a similar pink color at 48 h incubation, phenotypic differentiation was possible by the rough, paraffin-like texture or the intense purple color acquired by C. krusei and C. glabrata, respectively. Moreover, in this medium, the presence of C. auris in combination with other species of similar color was not limiting for its early identification, due to this medium selecting only strains resistant to this antifungal. Conclusions: The use of chromogenic media such as CHROMagar (TM) Candida Plus facilitates a presumptive identification of C. auris. However, this identification can be difficult in the presence of mixed cultures. In these cases, the use of CHROMagar (TM) Candida medium with 32 mg/L fluconazole offers better performance for the identification of C. auris by inhibiting fluconazole-susceptible strains and selecting rare or high fluconazole MIC (> 32 mg/L) isolates.

Automated summary

This study describes the morphological characteristics of C. auris colonies on three commercial chromogenic media. CHROMagar (TM) Candida Plus and HiCrome (TM) Candida can provide presumptive identification of C. auris, but identification may be difficult in the presence of mixed cultures. The use of CHROMagar (TM) Candida medium with 32 mg/L fluconazole offers better performance for the identification of C. auris by inhibiting fluconazole-susceptible strains and selecting rare or high fluconazole MIC (>32 mg/L) isolates.