Dynamics of antimicrobial resistance in drinking water: a territorial study

By 2050, bacterial infections could become the leading cause of death due to the emergence and spread of antimicrobial resistant-bacteria (ARB) and -genes (ARG). Faced to this global problem, an integrative approach (human animal environment) is encouraged by the WHO. However, environmental antimicrobial resistance (AMR) remains insufficiently investigated, with a focus on wastewater and a disregard to current or emerging clinical concerns.

ARB and ARGs could be found in water intended for human consumption. Like many Mediterranean cities, Montpellier and surroundings (southeastern France) are predominantly supplied by water from karst aquifers that are vulnerable to contaminations above all in climatic changes context. In France, although the microbiological quality of drinking water is strictly monitored, AMR is not. This study is conducted at a local scale to i) test the concept of the use of the regulatory surveillance of drinking water to monitor AMR in a French area and ii) evaluate the dynamics of AMR in drinking water in relation with climatic events.

From 2024 samples (sanitary surveillance Aude and Hérault) conducted from January to April 2021, 85 Escherichia coli were isolated according to the regulatory protocol and studied for their antimicrobial resistance profile. bla_TEM, bla_SHV, bla_CTX-Mthat are the most frequent beta-lactamases-encoding ARG in human infections were researched in 37 cultivable Gram-negative community. Water was also sampled at the entering of drinking water treatment plant (Montpellier), under contrasted hydroclimatic conditions.

bla_TEM was found in 14% of E. coli while no E. coli carried bla_SHV or bla_CTX-M. bla_TEM, bla_SHV, bla_CTX-M were encountered in 43%, 3% and 0% of cultivable Gram-negative community respectively. The E. coli strains carrying the bla_TEM gene and the communities positive for bla_SHVcame mainly from karst aquifers.

Antibiotic resistance in drinking water in France had never been explored on this large scale. We showed the wide diffusion of TEM producing E. coli in drinking water as described in human samples. With this preliminary study we prove that the existing nation-wide regulatory surveillance network could be used with slight modifications to monitor AMR in an environmental compartment that directly expose human populations.