Research and analysis

Determining concentrations of substances that influence development of antimicrobial resistance in the natural environment: summary

Published 24 October 2024

Applies to England

1. Chief Scientist’s Group report summary

This project reviewed the available data on concentrations at which selection for antimicrobial resistance (AMR) has been reported for different antimicrobials and the approaches used to determine these concentrations. The findings will help to inform the Environment Agency and others as to the availability of such information including the range of substances studied to date and the limitations and challenges associated with the methods used to generate such data at the current time.

1.1 Background

Antimicrobial substances in the environment may drive selection for resistant microorganisms in the environment. Understanding the concentrations at which this occurs is important for assessing the potential impact of environmental concentrations of antimicrobials on the development of AMR. Determining these concentrations is an area of developing science and several different approaches have been developed and used to date.

1.2 Approach

A literature search was carried out and studies that have determined concentrations that can drive selection for resistance were reviewed. The project looked at the types of antimicrobials which have been studied, the range of methods used and whether the method used influences the value derived.

1.3 Results

Most studies have considered antibiotics with very few studies on other antimicrobials such as antifungals. The approaches used fall into two main groups: those that use existing Minimum Inhibitory Concentration (MIC) data to predict concentrations at which selection for resistance may occur; and those that determine the concentrations directly through experiment-based approaches. Insufficient data is available to make firm conclusions based on comparison of the different approaches used, but the analysis of the methods used highlights that the approach can influence the concentration determined.

1.4 Conclusions

To date, work to derive selective concentrations for antimicrobials has focused mainly on antibiotics (antibacterials) with very little information on selective concentrations for other antimicrobials. Moreover, the different approaches used can influence the values derived but there is currently insufficient data to draw firm conclusions around which approach(es) produce the most accurate or informative estimates.

This information, along with the discussion of the respective advantages and disadvantages of the two main types of approach used (i.e. MIC based methods or experimental methods), will enable the Environment Agency and others to be better informed about the basis and limitations of the current published values. This is important when considering the use of the published concentrations to help interpret the significance of environmental concentrations of antimicrobials on the development of AMR in the environment.

2. Publication details

This summary relates to information from project SC220007/R, reported in detail in the following output:

• Title: Determining concentrations of substances that influence development of antimicrobial resistance in the natural environment
• Project manager: Helen Wilkinson, Chief Scientist’s Group
• Research contractor: Aimee K. Murray, University of Exeter

This work was carried out as part of the Environment Agency Chief Scientist’s Group research into AMR in the environment and has been funded by the PATH-SAFE programme which has been funded by HM Treasury through the Shared Outcomes Fund.

Enquiries: research@environment-agency.gov.uk.

© Environment Agency