Passive sampling of hospital wastewater as a promising warning signal for Candidozyma auris in a low-prevalence setting: a proof-of-concept study

Candidozyma ( Candida ) auris is an opportunistic fungal pathogen with increasing worldwide prevalence. As it can spread quickly in healthcare settings, monitoring C. auris is essential for effective infection control. Current hospital surveillance of C. auris often focuses on screening high-risk patients, as prevalence in the Netherlands is low. Wastewater-based surveillance may provide a complementary approach by capturing signals from all hospital inpatients, but this commonly relies on expensive automated water samplers. This study examined the feasibility of using lower-cost, easily deployable passive samplers to detect C. auris in hospital wastewater of a low-prevalence setting. Ten passive samplers containing one cotton bud, one piece of medical gauze, and two electronegative membrane filters were deployed for 24 h during a 16-week period in whole-hospital wastewater. Samplers were installed before, during, and after admission of a patient colonized with C. auris . DNA was extracted using a combination of phenol-chloroform and bead-beating, and C. auris presence was assessed by real-time polymerase chain reaction (RT-PCR). One patient was sampled during two separate admission periods and was identified as C. auris -colonized based on the detection of C. auris DNA in multiple specimens at both time points. The load of the clinical specimens decreased from a cycle threshold (Ct) value of 27.9 to 34.4 at second sampling. Hospital wastewater was C. auris negative before patient admission, low positive throughout patient stay, with average Ct-values of passive materials ranging from 33.2 to 38.0, and returned to negative after patient discharge. Our findings highlight the possibility to detect C. auris in a passive sampler wastewater-based RT-PCR screening in a low-prevalence country during admission of a C. auris -positive patient. Although further studies are required, this proof-of-concept study identified passive wastewater sampling as potential C. auris -surveillance tool. This low-cost method may eventually complement existing risk-based strategies and provide warning signals to prevent C. auris transmission within the hospital.