Multicenter performance evaluation of the Simplexa C. auris Direct assay for the detection of Candida auris colonization in bilateral axilla/groin swabs

Candida auris is a multidrug-resistant fungal pathogen associated with healthcare outbreaks and high mortality. Its accurate and timely identification is critical for infection prevention, yet conventional culture-based methods are limited by slow growth, morphological ambiguity, and potential misidentification. This multicenter study evaluated the performance of the Simplexa C. auris Direct assay using 2,020 axilla/groin swab specimens collected from six clinical sites compared to culture followed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Specimens were tested prospectively ( n = 1,930) and retrospectively ( n = 90), with demographic data spanning inpatient, intensive care unit, emergency department, and long-term acute care hospital settings. Discordant results were resolved by bi-directional sequencing, targeting the internal transcribed spacer and D1/D2 regions of the 28S ribosomal DNA gene. Compared to culture followed by MALDI-TOF MS identification, the Simplexa assay demonstrated an overall sensitivity of 94.8% and specificity of 98.7%, with a Cohen’s kappa of 0.80, indicating strong agreement. Discordance rates were low (1.4%), and diagnostic accuracy was high (98.6%). The limit of detection was 127 CFU/mL for Clade I and 260 CFU/mL for Clade IV. Mean cycle threshold values were significantly lower in culture-positive specimens (25.1, 95% CI, 23.6–26.7) compared to culture-negative ones (33.6, 95% CI, 32.1–35.0; P < 0.0001). Comparative analysis with four lab-developed molecular tests (LDTs) showed low rates of discordance: 0.9% for LDT 1 and 2, 1.5% for LDT 3, and 0% for LDT 4, indicating a high level of agreement between the molecular methods. The Simplexa C. auris Direct assay provides a rapid and reliable alternative to traditional methods, providing results in under 2 h, supporting early detection and containment of C. auris in healthcare settings.

IMPORTANCE

Rapid and accurate detection of Candida auris colonization is essential for preventing healthcare-associated outbreaks and reducing mortality. This multicenter evaluation demonstrates that the Simplexa C. auris Direct assay offers a sensitive, specific, and practical alternative to culture-based methods, enabling earlier identification and containment of C. auris . These findings provide strong evidence to support its implementation in routine infection prevention strategies across diverse healthcare settings.