Candida auris: Clinical profile, diagnostic challenge and susceptibility pattern: Experience from a tertiary-care centre in South India.

Objectives: Candida auris is an emerging, multidrug-resistant yeast transmitted in healthcare settings. Conventional methods of speciation are unable to identify C. auris to species level. Three methods, namely VITEK® MS v.3.0, VITEK®2 and target sequencing of the internal transcribed spacer (ITS) region and 28S rRNA gene, were evaluated. Antifungal susceptibility testing (AFST) was also performed, and risk factors for acquisition of C. auris candidaemia were studied.

Methods: Between November 2016 and November 2017, 203 Candida spp. were isolated from blood cultures, of which 11 isolates that were unidentifiable by conventional methods were further tested by VITEK® MS v.3.0 and VITEK®2 and were confirmed by sequencing. AFST was carried out on all 11 isolates by broth microdilution according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Clinical and epidemiological data of all patients retrieved from electronic patient records were reviewed.

Results: Of the 11 isolates identified as C. auris both by ITS and 28S rRNA sequencing, VITEK®2 identified only 5 as C. auris and VITEK® MS v.3.0 was not able to identify any of them as C. auris. Ten isolates (91%) were resistant to fluconazole, whereas all isolates were susceptible to amphotericin B and caspofungin.

Conclusion: Candida auris can be misidentified in routine microbiology laboratories. Sequencing remains the gold standard if commercial identification systems are not updated.