The discovery of antibiotic-resistant bacteria in river systems around Oxford has renewed calls for routine, year-round monitoring of waterways, as scientists warn that antimicrobial resistance (AMR) remains one of the world’s most pressing public health threats.
A recent study found widespread traces of drug-resistant bacteria in Oxford’s rivers, adding to earlier evidence from 2015 that detected similar contamination in the River Thames, particularly near sewage treatment outfalls. While researchers say the presence of such bacteria is not unexpected, the level of risk posed to people using rivers for recreation remains unclear a concern for anti-pollution campaigners.
Antimicrobial resistance occurs when bacteria, viruses, fungi and parasites evolve over time and no longer respond to medicines designed to treat them. According to the National Health Service, resistance is accelerated by inappropriate use of antimicrobial drugs, poor infection control, lack of new medicines and insufficient global surveillance.
A 2025 report by the National Audit Office estimated that AMR contributes to nearly five million deaths globally each year. In the UK alone, it is linked to more than 35,000 deaths annually and directly responsible for around 7,600 fatalities.
Antimicrobials including antibiotics, antivirals and antifungals are critical for treating illnesses such as tuberculosis, urinary tract infections, chest infections and food poisoning. They are also essential for preventing infections after routine procedures like hip and knee replacements. With few alternative treatments available, the rise of drug resistance presents a serious threat to modern medicine.
Why Study Sewage?
Scientists are increasingly examining sewage treatment works and their discharge points as key monitoring sites for AMR. These facilities collect wastewater containing traces of medicines excreted by humans, antibacterial household products, antifungal shampoos and other antimicrobial chemicals. The mixture creates concentrated reservoirs of resistant bacteria.
Dr Rob Morley, Director of Index Microbiology and lead researcher of the Oxford study, warned that sewage systems could amplify resistance. He said bacteria in such environments have the potential to transfer genetic material, effectively increasing the environmental reservoir of antimicrobial resistance.
Currently, there are no legal limits on drug-resistant bacteria levels in treated sewage effluent, and water companies are not required to remove bacteria before releasing water into rivers. Beyond sewage discharge, rivers are also affected by agricultural and urban run-off containing veterinary medicines, pesticides, herbicides and fungicides all of which can contribute to antimicrobial pressure.
Monitoring Gaps and Policy Response
The UK government has adopted a national action plan to tackle AMR, and the Environment Agency is working with the water industry on chemical investigation programmes. These efforts aim to determine what to monitor in the environment and what concentrations of antimicrobials may drive resistance.
Between 2020-21 and 2023-24, the government spent approximately £567 million on AMR programmes. Despite this investment, the National Audit Office reported no sustained reduction in drug-resistant infections. In fact, by 2023, infections in England were 13% higher than the 2018 baseline, missing a target set by the Department of Health and Social Care to reduce such infections by 10% by 2025.
Campaigners in Oxfordshire are now calling for nationwide, routine testing of rivers to complement existing scientific monitoring. They argue that environmental surveillance could provide an early warning system, helping policymakers respond before resistance spreads further.
As antimicrobial resistance continues to rise globally, researchers suggest that studying river sewage may offer critical insights into how resistance develops and spreads. Monitoring waterways could become an essential tool in safeguarding public health especially in a world where the effectiveness of life-saving medicines is increasingly under threat.