Antimicrobial resistance in complex microbial communities

This is a 4-year PhD project co-funded by BBSRC and AstraZeneca Global Environment.

The project aims to develop and validate approaches to investigate the selective potential of environmentally relevant concentrations of antibiotics in complex microbial communities.

Due to regulatory interest under the Water Framework Directive – where Environmental Quality Standards are being considered for some antibiotics – macrolides will be used as a case study within this project.

Until recently, the environment was not considered as an area where selection for antibiotic resistance would occur, with concentrations of antibiotics in these environments well below minimum inhibitory concentration (MIC) – the level at which growth is prevented in susceptible bacteria.

Recent work by Gullberg et al has shown that the concentration needed for selection of resistance is much lower than MIC and may be as low as the concentrations found in aquatic environments.

Macrolide antibiotics such as erythromycin and azithromycin have recently (2015) been put on the Water Framework Directive’s priority watchlist as they have been reported at relatively high concentrations in the environment. There have also been many reports of resistance elements to these drugs being found in environmental settings.

These are important antibiotics as they are used in the clinic for the treatment of a variety of infections such as shigella, chlamydia and salmonella and were the 3rd most prescribed class of antibiotics in the UK in 2014.

Because of the nature of this class of antibiotics, the study aims to investigate whether selection for and horizontal gene transfer of macrolide resistance gene elements occurs at the concentrations found in aquatic environments.

The study will involve both in situ and in vitro experiments to investigate evolution of AMR within complex microbial communities.

It is hoped that this study will inform future policy and regulation of environmental pharmaceutical residues.

Image courtesy of Shutterstock