Longitudinal wastewater-based surveillance of vancomycin-resistant Enterococci in tertiary-care hospitals

Vancomycin-resistant Enterococcus (VRE) is an important cause of healthcare-associated infections. We adapted wastewater-based surveillance as a tool to longitudinally monitor VRE in hospitals through the detection of vancomycin resistance genes vanA and vanB.

Wastewater from four tertiary-care hospitals (three adult and one pediatric, totaling >2300 inpatient beds) and all three municipal wastewater treatment plants (WWTP) in Calgary, Canada (∼1.8 million) was sampled weekly (March to September 2022) and every other week (September 2022 to March 2023). Wastewater pellets were collected, DNA extracted, and vanA and vanB quantified by qPCR. vanA and vanB gene copies were assessed as raw (copies/mL) and normalized with three different fecal biomarkers - total bacterial 16S-rRNA, Bacteroides HF183 16S-rRNA, and human 18S-rRNA. Raw and normalized vanA and vanB abundance from each site was compared with clinically identified infections, vancomycin prescribing and hemodialysis services.

The abundance of vanA was up to 1085-fold higher (p < 0.0001, Mann-Whitney) and vanB up to 32-fold higher (p < 0.01, Mann-Whitney) in adult hospitals compared to an aggregate municipal signal and exhibited significantly greater variation. Strong correlations between each method of fecal normalization and raw-measured vanA and vanB were observed, and no normalization method proved superior (Spearman's r = 0.50-0.96, p < 0.0001). vanA abundance was strongly correlated with hemodialysis provision (Spearman's r = 0.8357, p < 0.0001) but not vancomycin prescribing.

Wastewater-based surveillance is a comprehensive tool capable of longitudinal real-time hospital surveillance for VRE with the potential to transform the ability of infection control and antimicrobial stewardship programs to dynamically track, understand, and mitigate nosocomial antimicrobial-resistant pathogens.