Detection of Candidozyma (formerly Candida) auris from ward wastewater during an outbreak using culture and molecular...

Candidozyma (Candida) auris is a multi-drug-resistant fungal pathogen associated with protracted, costly hospital outbreaks. Conventional patient-level screening is resource-intensive and may not be cost effective. Wastewater surveillance may offer a pragmatic, ward-level approach to early detection.

To determine whether C. auris can be reliably detected in ward wastewater during an ongoing hospital outbreak; to compare the performance of culture- and PCR-based wastewater methods with patient-level colonization screening.

Between August and September 2024, during an ongoing C. auris UK hospital outbreak, a point-prevalence survey was conducted alongside sampling of 12 corresponding ward sluices. Wastewater grab samples and environmental swabs from sluice sinks, macerators and handwash sinks were investigated by direct culture and enrichment broth, as well as AurisID® real-time PCR assay on the centrifuged pellet. Whole-genome sequencing was performed on matched patient and wastewater isolates to assess genetic relatedness.

Using the detection of ≥1 C. auris patient on a ward as the standard, sensitivity of culture was 75% (95% confidence interval (CI) 35-97%) and specificity 100% (95% CI 40-100%); AurisID® PCR sensitivity was 100% (95% CI 63-100%) and specificity 75% (95% CI 19-99%). Whole-genome sequencing analysis demonstrated clustering and clonality of wastewater and patient isolates (<10 single-nucleotide polymorphisms difference).

We report the first detection of C. auris from hospital ward wastewater using culture and PCR. Screening ward wastewater may offer a sensitive, cost-effective alternative to individual patient screening in low-prevalence settings, supporting earlier ward-level detection: prospective, longitudinal studies are needed.