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Comparative Evaluation of C. auris Molecular Assays and New Media
Background
Candidozyma auris (C. auris) is a multidrug-resistant fungal pathogen causing severe invasive infections with high transmission risk in healthcare settings. This study evaluates the performance of six commercial molecular assays (5 rtPCR, 1 LAMP), three solld media and compares two liquid media eSwab® and a novel selective broth, CABroth" for clinical laboratory use.
Method
60 clinical C. auris isolates, 27 non-auris CAH-clade isolates were used to evaluate all methodes of detection.
Results
(1) Validation of 60 clinical C. auris strains and 27 close relatives (CAH clade)
rtPCR assays (fig 1 ). Sensitivity: 100% for all assays ( 60/60 C. auris detected), Turnaround Time: 30 min - 6 h, Throughput: 1-90 samples per run, Mean CT Values (95%CI): Simplexa: 20,48 (20,00- 20. 95); AurislD: 23,83 (23,36-24,3), Vivalytic: 30,49 (29,72-31,27), Fungiplex: 28,88 (28,25-29,52), AltoStar: 26,53 (26,05-27,02)
LAMP assay (fig 2). Median TTP: 9.43 min (8.80-9.97); Quickest assay! 6 false positives among CAH-clade, Specificity: 77,7% Adjusted cut-off (15 min dotted line) improved specificity to 96.3% as 1x C. duobushaemuliremained positive.
(2) Dilution series of 5 C. auris strains (Clade 1-V) and LOD
Molecular assays (fig 3).
All rtPCR assays identify C. auris at low concentrations. AltoStar C. auris shows best performance. LAMP has the lowest sensitivity. Simplexa is inhibitory with CABroth™, otherwise media perform equally.
Selective media (fig 4).
Most tested selective media detect C. auris in low concentrations. However, HICrome showes a limited detection rate. CAbroth TM harbours the highest yield, even at very low concentrations, but also longest time of incubation.
(3) Performance of solid selective media vs. 60 clinical C. auris strains and 27 close relatives (CAH clade)
CHROMagar and Brilliance show equal sensitivity, while HiCrome seems to be to selective for a nonMOR setting (no growth of relevant clinical strains)
Conclusion
Rapid C. auris detection is elemental for outbreak and infection control. Overall the assays show medium to excellent performance. However, cultural methods harbour at least equal sensitivity compared to molecular tests. Patient samples are currently evaluated to further validate our findings.
