Research and analysis

Scoping review into environmental selection for antifungal resistance and testing methodology: summary

Published 22 July 2022

Applies to England

1. Chief Scientist’s Group report summary

When natural microbial communities are exposed to antimicrobial substances any strain that can resist the harmful effects can come to dominate the population by simply growing faster than its neighbours. Hence exposure to antimicrobials in the environment can result in selection for resistance in the microbial community.

The concentration of a substance at which selection for resistance may occur has been studied in antibiotics but there is limited work on antifungals. This project reviews the current understanding of the mechanism for selection for antifungal resistance in fungal species following exposure to antifungals and considers potential methods to determine the lowest concentration of an antifungal that can lead to a selective advantage for resistant organisms.

This work will help raise awareness of the need for methods for the identification of concentrations at which selection for resistance to antifungals may occur and forms the basis for further method development.

1.1 Background

Antifungals are used widely including as medicines, personal care products such as antidandruff shampoo, and as pesticides in agriculture. As a result, there are numerous pathways by which antifungals can reach the environment. An understanding of the concentrations that may influence development of resistance is therefore important. It is useful to identify whether the work undertaken for bacteria and antibiotics can help determine concentrations for antifungals and fungi.

1.2 Approach

The report reviews the range of antifungals used, their mode of action and the various mechanisms by which selection for resistance occurs in fungal species. The potential to modify methods used for antibiotics and bacteria are considered along with approaches that could be used to determine selection concentrations based on knowledge of the specific mechanisms for resistance development for fungi. The potential advantages and disadvantages of the different methods identified are outlined in the report, including the practicalities and potential costs associated with the different approaches.

1.3 Findings

The mechanisms by which resistance may develop in fungi have been identified including details of the key differences in the characteristics and physiology of fungi and bacteria. Based on this information approaches for modifying methods developed to study bacteria and antibiotics are identified, for example, modification of the nutrient medium used. In addition, approaches that study effects on specific resistance mechanisms identified in fungi are identified. Due to the wide range of fungal species present in the environment, the report proposes that further work on method development could focus on Candida species (yeasts) and Aspergillus species (moulds) as these are found in the environment and are also of clinical importance. In addition, azole fungicides were focussed upon as they are used in both human/veterinary medicine and agriculture.

1.4 Conclusions

Potential methods to help us understand when the presence of antifungals will drive resistance are identified.

The findings of this work will help develop approaches for the generation of antifungal resistance selection concentrations, which will help the Environment Agency to understand the risk associated with antifungal use in the environment.

1.5 Project details

This summary relates to information from project SC200011, reported in detail in the following output:

• Report: SC200011

• Title: Scoping review into environmental selection for antifungal resistance and testing methodology

• Project manager: Helen Wilkinson, Chief Scientist’s Group

This project was funded by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools, and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk

© Environment Agency