Validation of molecular detection of Candida auris from wastewater

The high rates of multi-drug resistance and increasing transmission rates in healthcare environments reported for Candida auris (C. auris ) led to its categorization as an urgent threat in the latest Centers for Disease Control and Prevention (CDC)’s Antibiotic Resistance Threats Report released in 2019. C. auris skin colonization and shedding contribute to its high transmissibility and allow for its recovery from wastewater. The incorporation of C. auris into wastewater surveillance workflows could aid in early detection of healthcare facilities with C. auris emergence and could lead to better understanding of pathogen prevalence and trends in a healthcare system. The goal of this study was to validate a wastewater testing workflow for the detection of C. auris using a quantitative polymerase chain reaction (qPCR) protocol originally developed for C. auris colonization screening. Using a wastewater matrix, the assay showed 96.8% PCR amplification efficiency with a slope of −3.4 and high sensitivity with a limit of detection of 1.8 colony-forming units/milliliters. The assay also showed high reproducibility. These results suggest that the qPCR assay used for the detection of C. auris from clinical specimens can also be adapted for accurate detection of this pathogen from wastewater samples.

IMPORTANCE

Candida auris is an emerging, often multidrug-resistant, pathogen with the ability to cause severe infections. Due to its persistence on surfaces and fomites, it spreads efficiently in healthcare settings. Controlling transmission can be challenging because it can colonize skin, from which it is shed, further contaminating the healthcare environment. Patient screening is both time and cost-consuming, and limited proactive screening by healthcare facilities has resulted in insufficient monitoring. Wastewater surveillance offers an opportunity to better understand the prevalence of this pathogen within healthcare environments. Here, we validated a C. auris colonization qPCR assay for use in detecting C. auris in wastewater samples, a more cost-effective way to screen an entire healthcare system. Our results show that this assay can reliably detect C. auris in wastewater, supporting its integration into existing wastewater surveillance workflows and allowing detection in areas where direct patient screening is not yet available.