Antibiotics and antibiotic resistance in our waters

Current environmental risk assessment guidelines and environmental regulations do not consider antibiotic resistance. However, mounting evidence that antibiotics in the environment increase levels of resistance is creating pressure for change. One specific debate is around what antibiotic concentration ‘threshold’ we should use for regulation.

Our recent research suggests that we may need to consider not just the antibiotic concentration that increases resistance, but also the antibiotic concentration that allows resistant bacteria to simply persist in the environment. If resistant bacteria persist rather than dying off over time, this increases the risks associated with human exposure and also increases the potential for resistance to continue to evolve and spread in the environment.

Currently, we are still missing two vital pieces of the puzzle needed to properly risk assess antibiotics in the environment and their subsequent regulation. First, concentrations of antibiotics in the environment need to be regularly monitored. There are currently four antibiotics on the European Commission’s Water Framework Directive’s ‘Watch List’ 2020 – meaning these antibiotics should to be monitored in European waters so it can be determined if they pose an environmental risk. This is not necessarily the same as an antibiotic resistance risk, though this is starting to be considered.

The second problem is that there are still very few data specifying the concentrations of antibiotics that enrich antibiotic resistant bacteria. This is because there is no standardised experimental method that can generate this data on a large scale. Our current work details a new, low cost and rapid method that can be used to fill this data gap. This method could also be repurposed in future for environmental surveillance, to identify environmental hotspots where resistance may more readily evolve, allowing us to target mitigation efforts where they are needed most.

Antibiotic resistant bacteria and antibiotics are in our waters – so what can we do? We need regular monitoring of antibiotics and data on the lowest concentrations that increase resistance, so we can regulate their release into the environment. We need to continue working with policy makers and other stakeholders to generate, share and discuss data that address their needs. We also need greater public awareness of the issue, to drive change. These are just the first steps towards tackling this complex issue that has far reaching implications for human health, the global economy and the health of our environment.

Dr Aimee Murray is an independent NERC Industrial Innovation Fellow at the University of Exeter.

Prof William Gaze is Professor of Microbiology at the University of Exeter.

Dr Isobel Stanton is a post-doctoral researcher at the University of Exeter.

Dr Anne Leonard is an independent NERC Industrial Innovation Fellow at the University of Exeter.

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