International Workshop on Water Reuse in Agriculture and the Risk of Antimicrobial Resistance

On October 22-24, 2024, the French National Research Institute for Agriculture, Food and the Environment [INRAE] is hosting an international workshop entitled Water reuse in agriculture and the risk for development and transmission of antimicrobial resistance. This workshop is sponsored by the Organisation for Economic Co-operation and Development (OECD) Co-operative Research Programme: Sustainable Agricultural and Food Systems , and by the AgroEcoSystem division of INRAE, the Agroécologie Laboratory, the regional council of Bourgogne Franche-Comté, and Dijon Metropole.  The workshop organizers are Ed Topp [INRAE], Dominique Patureau [INRAE], Erica Donner [University of South Australia] and Eddie Cytryn [Volcani Institute]. An interdisciplinary group of 40 colleagues from Europe, Asia and North America representing the research, industry, policy and regulatory communities will meet in Dijon.

In many arid parts of the world (e.g., around the Mediterranean basin, SW United States, Australia) intensifying deficits in precipitation are threatening food security. In response to this, agriculture is increasingly turning to the use of effluent from municipal wastewater treatment plants for irrigation of crops. For example, in Israel close to 90% of effluent is used to irrigate crops, representing about 50% of all the water used for irrigation.

Antimicrobial resistance (AMR) is a seminally important global public health challenge. It is estimated that in 2019 antibiotic-resistant infections contributed to the death of 5 million people. If the current rate of resistance development is left unchecked, by 2050 mortality due to resistant infections will outstrip those due to all cancers combined. Mitigating the pace of AMR development will require action across the One Health continuum, in the human, agricultural and environmental realms.

Wastewater effluent used for irrigation can contain residues of antibiotics and other kinds of chemicals such as biocides that can co-select for antibiotic resistance. Likewise, antibiotic-resistant bacteria and the genes that they carry which confer antibiotic resistance are excreted by people in the sewershed, and may survive the sewage treatment process. The degree of contamination of the wastewater will vary according to the rigor of sewage and effluent treatment. In high-income countries, quaternary treatment may be employed in order to reduce the burden of contamination prior to release of the effluent into the environment. On the other hand, in many lower income settings untreated or poorly treated effluent may be used for irrigation.

The concern therefore is that irrigation with reused wastewater may increase the reservoir of AMR in crop production systems, and increase the likelihood of transmission to humans via contaminated foodstuffs, in particular vegetables or fruits that are eaten raw. Within this context, there is a need to review the current state of knowledge and identify gaps regarding risks related to the reservoir of AMR in plant-based food production systems, what impact wastewater reuse might be having on that reservoir, and the risks of AMR transmission to humans through consumption of vegetables or fruits produced in these systems. Outputs from the workshop will include a report, and a co-authored manuscript reviewing the current state of knowledge, regulatory context, and a proposed research agenda to understand and help mitigate any risk of wastewater reuse on the development and transmission of AMR from the environment to foodstuffs and then people.