Shallow groundwater exposure to antibiotic resistant Escherichia coli: hydrochemical approach to identify sources and transfer pathways

Antimicrobial resistance is a growing public health concern in European hospitals and communities. Escherichia coli is one of the most common agents of bacterial infection which causes urinary tract infections as well as more serious infections (septicemia). The aim of the project is to investigate the prevalence of extended-spectrum beta-lactamase (ESBL) producing E. coli that are resistant to third generation cephalosporins, in waste water treatment plants in the Burgundy region and to monitor the impact of treated effluents on water quality in the Ouche watershed. CTX-M is a recently occurring ESBL, encoded by the blaCTX-M genes, which causes resistance to 3rd generation cephalosporins (3GC). A regional strategy for sampling surface and ground waters had be carried out in relation to existing data, in order to evaluate the capacity of CTX-M producing E. coli to spread and survive in water resources. To characterize the dissemination of ESBL producing E. coli in the aquatic system, we selected several sampling points according to hydrogeological contexts, land use and waste water plants with a particular interest for karst aquifers that are predominant in the studied area. For each sampling point, we combined microbial and chemical approaches. Inorganic elements (including trace elements) were analyses completed by REE (ie Gadolinium anomaly) and pharmaceutical products (caffeine, carbamazepine, ibuprofen and acetaminophen). From the presence or absence of ESBL producing E. coli, we attempt to identify the sources and vectors of water contamination. The first results show the contamination of surface water with ESBL producing E. coli. This dissemination is associated with the discharge of treated sewage into the environment. Nevertheless, in alluvial aquifer transfers of E. coli is low to zero and ESBL producing E. coli is zero. In this context, surface water is filtrated by the river banks which prevent the E. coli migrationtoward ground water. On the opposite, in karstic area, we note the presence at low level of ESBL producing E. coli in ground water and springs. Unlike the waters of the alluvial aquifer, karstic waters are highly vulnerable.