Keep the hospital clean: diagnostic performance of ten different molecular and culture-based methods to detect Candidozyma auris
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Rationale
Candidozyma auris (formerly Candida auris ) is a globally emerging potentially multi-drug resistant human pathogenic yeast. To detect C. auris we aimed to compare different culture-, and molecular-based methods.
Methods
Rectal swabs routinely collected in clinical care were spiked with different concentrations of C. auris . Co-infection/colonization was mimicked by spiking part of these samples with other pathogenic Candida species. Spiked materials were cultured at 37°C or 42°C using CHROMagar Candida and CHROMagar CandidaPlus plates. In parallel, samples were incubated in a dulcitol salt enrichment broth. Additionally, we compared seven in-house and commercial molecular tests on the direct material and from the broth one day after inoculation.
Results
Culture-based methods showed sensitivities up to 100% within 48 hours of incubation, although sensitivity decreased as low as 44% at lower concentrations (≤50 CFU per inoculum), in the presence of an abundance of other species and at higher temperature (42°C). Incubation at 42°C made visual identification possible since other species with similar colony morphologies did not grow at this temperature. No added value of using the dulcitol salt enrichment broth was found. qPCR on direct materials was highly sensitive and specific (both up to 100%) but major differences between various molecular tests were observed.
Conclusion
We showed that both culture-based and molecular methods are sensitive for diagnosing C. auris . The clinical setting (routine screening versus an outbreak), local prevalence and the load in those that carry or are infected by C. auris are important factors to consider when determining which diagnostic tests should be employed.
