This is one of the first states of knowledge on this issue. For this, the Agency relied on the scientific literature and on the results of research carried out in France on the contamination of environments, in particular those financed by ANSES within the framework of the National Environment-Health-Work Research Programme.
Contamination of environments by antibiotics is linked to human activities
Whatever the environment, the concentrations of antibiotics are low in France. The antibiotics most frequently found in the environment are those that degrade the least, and not necessarily the most consumed. The main sources of contamination of the environment by antibiotics are linked to human activities: discharges of treated wastewater and spreading of sludge from treatment plants and livestock effluents. Thus, the antibiotics found in the water are in higher concentration downstream of wastewater treatment plant discharges than upstream. With regard to soil contamination, the data are less numerous and relate only to spreading areas. The antibiotics and the concentrations found depend on the type of spreading.
Main routes of soil and water contamination by antibiotics, antibiotic resistant bacteria and resistance genes.
Resistant bacteria that disappear faster than genes
Antibiotics, resistant bacteria and resistance genes have the same sources of contamination. Concentrations of resistant bacteria and resistance genes decrease with distance from the source of contamination, whether it is a discharge of treated wastewater or a spreading site. Although the treatment of wastewater and spreading products makes it possible to reduce the quantities of resistant bacteria and resistance genes released into the environment, they are not designed to allow their complete elimination.
The antibiotic-resistant bacteria studied are mainly of faecal origin. They have difficulty surviving in the environment and are mainly found in sites heavily contaminated by human activities. Resistance genes can persist longer, either outside the cells or hosted by other bacteria, not taken into account in the studies.
Study of the mechanisms that can promote the survival of resistant bacteria
ANSES’s work also looked at the environmental factors that might favor the selection of bacteria resistant to antibiotics and the transmission of resistance genes. Few data are available on this subject. In general, it seems that the quantities of antibiotics found in the environment in France are too low to promote the survival of resistant bacteria and the persistence of resistance genes. In addition, the presence of metallic trace elements or biocides, the diversity of bacterial communities and the heterogeneity of environments might influence their fate in the environment.
Improve monitoring of environmental contamination and continue to acquire knowledge
The results obtained are likely to evolve with climate change and the evolution of practices related to the circular water economy, such as the reuse of treated wastewater or the artificial recharging of groundwater tables. These phenomena might in fact modify the routes of introduction and dissemination of antibiotics and resistant bacteria in the environment and have an impact on the ability of the environment to dissipate this anthropogenic contamination.
In order to improve the comparison of data, ANSES recommends monitoring in all studies on antibiotic resistance in the environment a set of indicators including antibiotics, a resistant bacterium and a resistance gene. The Agency recommends that the studies that will be undertaken take into account the future in time and space of this contamination. Finally, ANSES issues recommendations to consolidate and deepen current knowledge, whether on environmental contamination by antibiotics and resistance bacteria and genes, on the factors favoring their dissemination or on the assessment of ecosystems to dissipate contamination.