Candida auris and some Candida parapsilosis strains exhibit similar characteristics on CHROMagarTMCandida Plus.

ABSTRACT

Candida auris is considered a public health problem due to its resistance and its tendency to cause nosocomial outbreaks. CHROMagarTMCandida Plus has recently been marketed as capable of presumptively identifying C. auris. The objective of this work was to analyze the ability of this new chromogenic medium to differentiate C. auris from other members of the C. haemulonii complex and from other yeasts commonly isolated in clinical practice. A collection of 220 strains including species of the C. haemulonii (n = 83) and C. parapsilosis (n = 80) complexes was studied. The strains were identified by molecular methods and cultured as individual or as mixed aqueous inoculum on CHROMagarTMCandida Plus plates. Colony morphotypes were evaluated at 5 time points. CHROMagarTMCandida Plus was a helpful tool for presumptive identification for C. auris. Better reading results were obtained after 48 hours of incubation at 35°C. It is able to easily differentiate C. auris from other closely related species of the C. haemulonii complex and other yeasts. This chromogenic medium would be also useful as screening and surveillance tool for C. auris colonization. However, we demonstrated that it would be a possible misidentification of C. parapsilosis as C. auris (44.3% showed similar morphotypes). To reduce false positives when it is used in a context of a C. auris outbreak, we propose to supplement the chromogenic medium with 8 µg/ml fluconazole. This modified medium was tested and it clearly differentiate C. parapsilosis from C. auris.

CHROMagarTMCandida Plus is able to differentiate C. auris from other Candida spp., including other species of the C. haemulonii complex. However, 44.3% of the tested C. parapsilosis strains would be misidentified as C. auris. We propose the addition of 8 µg/ml fluconazole to solve this issue.