Could the load of carbapenemase genes in hospital wastewater be a proxy for emerging resistance to carbapenems in humans?

Antimicrobial resistance (AMR) poses a growing threat to global public health and is a key concern for infection control teams in hospitals. However, AMR surveillance is time-consuming and limited in most countries, resulting in incomplete findings. In high-income countries, infection control teams ensure the contact tracing of every patient carrying an emerging extensively drug-resistant bacterium which is very time-consuming. Wastewater surveillance (WWS) has been proposed as an alternative approach for the surveillance of infectious diseases. This study aims to test the feasibility of AMR WWS under real-world conditions in hospital. It investigates the dynamics of endemic ( bla CTX-M ) and emerging AMR genes ( bla OXA-48 , bla NDM , bla KPC and vanA ) in wastewater from two hospital buildings where patients with contrasting risk for carrying resistant bacteria were cared for and compares results with clinical data. The sampling programmes were adapted according to the sampling sites and patient flow for each hospital building. Genes were quantified in the effluent using qPCR and dPCR. Cultivable carbapenemase-producing Gram-negative bacteria were characterised using MALDI-TOF MS and PCR. The feasibility of AMR monitoring in wastewater in real hospital conditions was demonstrated by dPCR and qPCR, which produced correlated results. The presence of peaks and the low load of the vanA and bla NDM genes in wastewater (compared to bla CTX-M ) were consistent with their known emerging status, as indicated by national and local clinical data. However, the high concentration of bla OXA-48 and bla KPC in wastewater was unexpected because it did not reflect the known clinical involvement of these emerging resistances, particularly in the case of bla KPC . Bacterial culture also revealed discrepancies between the species isolated in wastewater and those isolated in patients in the hospital, with a majority of Citrobacter spp. carrying bla KPC and bla OXA-48 in wastewater, whereas Escherichia coli and bla OXA-48 dominated in patients. Quantifying carbapenemase genes in wastewater was able to differentiate between buildings housing patients contrasting risks of emerging AMR. This study shows the WWS feasibility in real hospital conditions and preliminary findings regarding patient populations but identified obstacles that need to be overcome prior to use WWS for routine surveillance in an infection control hospital context.