Candida auris real-time PCR for surveillance of patients and environment

Abstract

Background– Candida aurisis an emerging fungus which has caused nosocomial outbreaks worldwide. Screening for surveillance is challenging as it’s a slow grower, samples may have multiple candida spp and many commercial assays have limited accuracy. Following an outbreak in 2016, a real-time PCR was developed for rapid patient and environmental screening. Laboratory parameters, results and pitfalls from Jan 2018 to March 2019 are described. Methods– Evaluation was performed using EQA panels and validated on clinical swabs and urine samples. Patient screening was performed in high risk clinical areas from nose, throat, axilla and groin swabs and catheter urine. Environmental screening was done in areas where transmission was detected. Positive or indeterminate samples were cultured and colonies identified on the Vitek 2 and confirmed by PHE reference laboratory. Results–The Limit of detection was 100 organisms/ml. Sensitivity, specificity, PPV and NPV were 100.00%, 99.35%, 85.71%, and 100.00%. 4,792 urines and 10,819pooled swabs were tested. 21 colonised patients were identified in two outbreaks and two isolated transmission events. Median turn-around time for positive results was 24h30min (range 04:22-96:46h) and 143h14min (range 75-406h) for PCR and culture respectively. Urine samples did not add to the overall sensitivity of screening.C. aurisDNA was detected in 30/84 (35%) environmental swabs but C. auris isolated in only 2/84. Drawbacks of the PCR include reagent contamination seen on two occasions. Conclusion – C. auris screening by PCR is a rapid means of detection in both patients and environment but prudent use of culture is required to help determine infectivity.