Hospital Effluents: a Health Monitoring Tool in the Era of Multi-resistance

Bacterial antimicrobial resistance (AMR) is a major public health threat and surveillance is a key element in the fight against AMR. Of particular concern is the emergence and spread of multi- and highly antibiotic-resistant bacteria (MDROs), in particular extended-spectrum beta-lactamase (ESBL-E) and/or carbapenemase-producing Enterobacteriaceae (EPC). Indeed, the latter currently pose a major therapeutic challenge due to the ineffectiveness of almost all first-line antibiotics and the need, in the event of infection, to use second-line molecules. E-BLSE and EPC are Enterobacteriaceae that naturally colonize the gut microbiota of humans and animals, and whose abundance in the microbiota increases thanks to antibiotic treatments. These bacteria are released into wastewater via faecal excretions, contributing to their dissemination into the environment. It is now recognized that there are transfers of resistance between human and animal compartments and the environment, at the origin of the "One Health" concept.

To assess human colonization by MDRO, it is necessary to perform individual screenings either in the subjects' stool or by rectal swab. These samples are difficult to collect or may be perceived as uncomfortable by the subjects and raise ethical questions. In addition, their implementation is costly and time-consuming for both healthcare teams and laboratories, limiting their implementation to certain hospital units. Monitoring of MDROs in wastewater from various sources, such as homes or hospitals, has therefore been proposed as an intermediate (or proxy) marker of patient colonization that provides a simple-to-implement, ethically acceptable, and inexpensive alternative for monitoring these strains in a given environment. This method has been widely used during the COVID3 pandemic and is at the origin of national networks such as the Obépine network. However, current studies are mostly carried out at the scale of cities or entire hospitals and struggle to establish direct links between human colonization and environmental contamination. In addition, horizontal gene transfer, local bacterial multiplication and the presence of bacterial biofilms in pipes can modify the environmental composition of bacteria and resistance genes, and potentially create a bias in the estimation of human colonization. However, wastewater surveillance remains an interesting tool for monitoring the spread of bacterial resistance to antibiotics, helping to identify the emergence of new resistances and even evaluating the effectiveness of interventions by hospital hygiene teams.

The SMIT building has an independent wastewater network, inherited from the history of the Claude Bernard Hospital, which specialises in the management of infectious diseases. In addition, this department welcomes patients in whom the prevalence of MDRO carriage is much higher than the average of the general French population, thus reinforcing the epidemiological interest of this structure. This unique configuration provides an ideal framework to study the emergence and persistence of bacterial resistance, supported by the presence of antibiotics and biocides, which are widely used in this department. The analysis of the effluents from this building (environmental compartment) would not only make it possible to quantify and characterize the bacteria and their resistance genes released into the wastewater, but also to establish a direct link with the colonization of patients hospitalized in this pavilion.

The human population studied (human compartment) will be made up of adult patients hospitalized in the infectious and tropical diseases department (SMIT) of the Bichat - Claude-Bernard hospital at the time of a wastewater sampling campaign from the building.