Validation and implementation of a commercial real-time PCR assay for direct detection of Candida auris from surveillance samples.

Abstract

Rapid and reliable laboratory methods are required for detecting the nosocomial yeast Candida auris. AurisID® (Olm Diagnostics) is a real-time PCR assay approved for detecting C. auris in fungal cultures and directly from blood samples, involving a nucleic acid extraction as a prior step. The purpose of this study is to validate the AurisID® kit for direct detection of C. auris from surveillance samples without prior DNA extraction and to analyse the results of implementing this methodology to our daily laboratory routine protocol for C. auris surveillance studies. Our PCR method using the AurisID® kit was compared with our routine protocol, consisting of culture in CHROMagar® Candida and identification by mass spectrometry. A total of 113 swabs were used for validation and 136 pair of surveillance samples were tested. Limit of detection (LOD) was determined by using swabs in Amies transport medium, which were spiked in a series of dilutions of a C. auris standardised suspension (0.5 McFarland). The PCR method showed high sensitivity, specificity, predictive positive value and predictive negative value (96.6%, 100%, 100% and 98.2%, respectively) when compared with the routine protocol. LOD was 500CFU/ml, which corresponds to approximately 1CFU/PCR. Our PCR method using the AurisID® kit allows a reduction in the turnaround time for surveillance of C. auris compared with other methods. These results are expected to contribute to control C. auris outbreaks, allowing isolation of patients and cleaning of environmental surfaces in advance.