Candida auris PCR for high-throughput infection control screening

Abstract

Candida auris has significant implications for infection control due to its multidrug resistance and spread in healthcare settings. Current culture-based screening methods are laborious and risk muco-cutaneous colonisation of laboratory staff. We describe the adaptation of a published real-time PCR for the identification of C. auris in skin swabs for high-throughput infection control screening. Two published primer and probe sets were analysed utilising serial 10-fold dilutions of 15 C. auris strains to assess the PCR limit of detection. One primer and probe set was compatible with our laboratory workflow and was selected for further development yielding a limit of detection of 1 colony forming unit per reaction. Non-C. auris isolates as well as routine skin swabs (n = 100) were tested by culture and PCR to assess specificity, where no cross-reactivity was detected. Skin swabs from a proven C. auris case (n = 6) were all both culture positive and PCR positive, while surveillance swabs from close contacts (n = 46) were all both culture negative and PCR negative. Finally, the use of a lysis buffer comprising 4 m guanidinium thiocyanate rendered swab-equivalent quantities of C. auris non-viable, providing assurance of the safety benefit of PCR over culture. The development of a PCR assay for high-throughput infection control screening is a promising method for rapid detection of C. auris with utility in an outbreak setting.

Lay summary: Candida auris, a difficult to treat yeast-like fungus, has spread through healthcare facilities globally, posing a serious threat to the health of patients. We evaluated a PCR-based method suitable for screening large numbers of patient samples to rapidly and accurately detect C. auris.

Keywords: Candida auris; infection control; laboratory safety; real-time PCR.