Establishment and evaluation of recombinase polymerase amplification assay for identification of Candida auris

  Objectives   Candida auris (C. auris) is an emerging multidrug-resistant yeast associated with high mortality. We developed a rapid assay for the specific identification of C. auris based on recombinase polymerase amplification (recombinase polymerase amplification, RPA).

  Methods  The fragment of 5.8S, all of ITS2 rRNA genes of Candida species were used as the target sequence to design C. auris specific primers and for Candida universal primer. The detection limit of RPS was tested and 61 yeast isolates and 4 bacterial strains were used to evaluate the specificity of RPA, and the detection power of RPA for C. auris under non-culture condition was evaluated. Five common Candida species and C. auris were used to evaluate the universal RPA assay.

  Results  The RPA assay could identify C. auris strains with a specificity of 100.00% at 37 ℃ in 20 minutes and the limit of detection was 10³ copies/reaction to polymerase chain reaction(polymerase chain reaction, PCR) assay. The assay could detect C. auris in blood within 2.5 hours with the detection limit of 1.02×10³ colony forming units (CFU)/mL same to PCR assay. The Candida universal RPA assay could realize the preliminary differential diagnose of infections of five common clinical Candida species and C. auris, by amplifying the products with different sizes. In the mixed pathogen experiment, two kinds of easily distinguishable bands can be produced in the case of the ratio of C. albicans to C. aurisat 5∶1, 1∶1 and 1∶5.

  Conclusion   A simple, rapid and cost effective RPA assay has been established, which can be used for the preliminary differential diagnose of infections of five common clinical Candida species and C. auris, with high specifity and sensitivity.