Building on our previous blog, which explored antimicrobial resistance (AMR) in agri-food systems, this piece highlights new research from The James Hutton Institute on AMR across water environments.
Understanding AMR in Scotland’s Rivers: A Multi-Scale Approach
Rivers play a vital role in the movement of AMR across ecosystems. Human and agricultural activities, such as the discharge of treated and untreated sewage, application of livestock manure, slurry, anaerobic digestate, and faecal deposition on grazing land, introduce resistant bacteria and genes into watercourses. Once present, AMR can persist and spread within aquatic environments.
River water is routinely abstracted for crop irrigation, drinking water, and livestock hydration. This creates multiple pathways for resistant organisms to re-enter human and animal populations, either through direct contact during recreational activities or indirectly via the food and drink supply chain. This environmental circulation of AMR poses a growing public health and biosecurity challenge, highlighting the urgent need for integrated water management and targeted mitigation strategies.
Building the Evidence Base: From Catchment-Scale Monitoring to a National AMR River Survey
To inform effective policy and intervention, a baseline understanding of AMR in Scotland’s rivers is essential. Researchers at the Hutton have conducted monthly sampling over one year in two catchments—the River Dee and the River Ugie in Aberdeenshire. This included measuring the diversity and abundance of AMR genes, faecal indicator bacteria (e.g. E. coli, coliforms), antibiotic concentrations and water quality along each river. Statistical modelling of these data are currently underway to better understand AMR dynamics.
Building on the catchment-scale work, a national sampling campaign is now in progress. Quarterly samples are being collected from over 60 river sites across Scotland, spanning all seasons. The combined dataset will provide a Scotland-wide baseline of AMR in river systems. This will identify hot-spots of AMR and support the development of a national AMR map to guide future monitoring and mitigation efforts. By establishing a robust baseline which will underpin future surveillance, Scotland is taking proactive steps to address the environmental dimensions of AMR and safeguard public health.
Pharmaceutical pollution drives AMR
Pharmaceuticals (medicines) are key in improving human health and wellbeing. However, about 30-100% of an orally administered dose of a medicine leaves the body without being broken down and enters wastewater streams. Levels of pharmaceuticals in wastewater can also be exacerbated by improper disposal of unused medicines down toilets and sinks. Although wastewater treatment plants can reduce the load of some pharmaceuticals, some still enter rivers following treatment. A major concern of pharmaceutical pollution is its potential to increase AMR. Exposure to antibiotics can increase resistance in environmental bacteria, which can then be passed on to pathogens. However, it is not just antibiotics that can increase AMR levels; medicines such as paracetamol can increase the potential for AMR genes to be spread between bacteria. These drivers are important for understanding the levels of AMR that we see in the environment. Hutton Researchers have developed a model to simulate antibiotic and pharmaceutical pollution in the River Ugie and River Dee catchments (using detailed data and information on prescription rates, wastewater treatment plants, and physicochemical properties) to assess selective pressure risks.
Policy Implications
A multi-disciplinary approach is being used by researchers at the Hutton to understand AMR across environmental systems. Alongside the work highlighted in our previous AMR blog, this research across water and farm environments provides critical evidence to support risk assessment of AMR exposure via water and food systems, prioritisation of catchments for intervention, and design of integrated water and land-use policies. This work also aligns with One Health and environmental protection strategies as advocated in the 5-year national action plan for antimicrobial resistance.
Written by Dr Eulyn Pagaling, Dr Lisa Avery, & Dr Mads Troldborg
(Main image: Loch surrounded by rolling hills and trees. Photo credit: Tullia Dean.)