Trinity research shows agricultural fungicides drive evolution of multidrug resistance in soil microbes

Posted on: 11 September 2026

Two newly published studies from Trinity College Dublin scientists raise significant concerns about the use of agricultural fungicides.

That is because they show fungicides can drive soil microbes to evolve multidrug resistance to clinically important drugs, in rapid time, and because warmer temperatures are combining with fungicide use to disrupt soil microbes in such a way that negatively impacts plant growth.

In one study, just published in the journal Evolutionary Applications, the scientists found that fungicides can drive the spread of multidrug resistance in soil bacteria. This refutes the common assumption that misuse and overuse of antibiotics is the near sole factor driving the antimicrobial resistance pandemic, and instead underlines that fungicides are probably very important too.

In controlled laboratory experiments the scientists exposed soil communities to Fubol Gold, a common fungicide formulation, under varying conditions for 16 weeks. Fubol Gold is now banned in Ireland (and the EU) but was previously common and is likely still present in soils here. They found that exposure rapidly selected for increased fungicide resistance, which was detectable after genome comparisons as early as the fourth week, Additionally, this exposure “co-selected” for resistance to chloramphenicol, sulphatriad and nalidixic acid (antibiotics), which are broad spectrum antibiotics commonly used to treat eye, urinary tract, and intestinal infections. 

An in the second study, just published in The ISME Journal, the scientists found that the combination of warmer temperatures and fungicide exposure causes a far greater disruption to the microscopic communities living in soil than either stressor causes on its own. The findings are significant because these microbial communities are essential to healthy soils, helping to recycle nutrients, support plant growth and maintain ecosystem functioning.

In controlled laboratory experiments, researchers exposed soil communities to warming, fungicide, or both for 16 weeks. While fungicide alone had relatively limited effects on some measures of soil functioning, the combination of warming and fungicide caused a major loss of microbial activity and reduced the community’s ability to process different sources of carbon. The combined stress also negatively affected the “biomass” of barley plants that were grown in the treated soils.

Dr Siobhán O’Brien, from Trinity’s School of Genetics and Microbiology, said the findings from the two papers highlight a significant blind spot in just how important fungicides are in negatively impacting ecosystems and, potentially, human health.

“We tend to automatically link the misuse and overuse of antibiotics to the growing antimicrobial resistance crisis, and while that’s not wrong, this work suggests our use of fungicides in agricultural settings is also very important in driving that resistance,” she said.

“Similarly, we tend to think of climate change and agricultural chemicals as presenting separate problems and then study these factors independently from each other. But in reality soils experience these pressures at the same time, and this new research shows that the combined effects can be much more damaging than we might expect.”

“The second study also found evidence that the effects of environmental stress could persist even after plants were returned to normal growing conditions, suggesting that soil microbial communities can retain a legacy of previous exposure. A whole soil microbial ecosystem suffered a relative collapse after being exposed to warming temperatures and fungicide, and the knock-on effect was poorer barley growth, underlining the obvious implications for agricultural practices as well as biodiversity and ecosystem functioning.”

What is the potential impact of this research?

The scientists say the findings underline the need to factor in how agricultural fungicides can drive multidrug resistance in bacteria that represent a genuine risk to human health, as well as considering how multiple environmental pressures interact when predicting the future health and resilience of soils under various climate change scenarios. 

The combined findings thus imply that agricultural practices may need to change if we are to better protect our soils, our ability to produce crops, and even our health.

This research was supported by funding from a BBSRC Discovery Fellowship and Community Foundation Ireland through a Research Ireland (then Irish Research Council) New Foundation Award. Additional support was provided by an NERC DTP Studentship and a Medical Research Council Career Development Award. 

The published research articles can be read at: 

• https://doi.org/10.1111/eva.70307
• https://doi.org/10.1093/ismejo/wrag196 

• Tags:
• Environment
• Health
• Research
• Science