Agricultural fungicides can promote antimicrobial resistance


New research from the University of Georgia has shown, for the first time, that compounds used to fight fungal plant diseases cause resistance to antifungal drugs used to treat people.

The study focused on Aspergillus fumigatus, the fungus that causes aspergillosis, a disease that causes life-threatening infections in 300,000 people worldwide each year. Posted in G3: Genes, Genomes, Geneticsthe study linked the agricultural use of azoles – compounds used to control fungal plant diseases – to the decreased effectiveness of clinical azoles used to treat fungal infections in patients.

“Our results show that resistance to compounds used to combat fungal infections in humans develops in agricultural environments,” said Marin T. Brewer, corresponding author of the study and associate professor of mycology in the College of Agricultural Sciences. and environmental. “The samples we collected from the agricultural setting were resistant to both the azoles used in the environment and the clinical azoles used to treat people.”

Treatment-resistant fungi are prevalent in the agricultural industry

Fungi can be a threat to humans and plants, causing over 1.5 million human deaths per year and crop losses of 20%.

It is not uncommon to find A. fumigatus in the environment. It’s aerial, and it’s everywhere. Most people inhale it with no problem, but it can cause serious infections in people with weakened immune systems.

When infected with a fungal strain resistant to agricultural azole fungicides, clinical azole drugs used in health care are also ineffective.

“Azole resistant A. fumigatus is prevalent in agricultural environments and especially in things like compost,” said Michelle Momany, corresponding author of the study and professor of fungal biology in the Department of Plant Biology at Franklin College of Arts and Sciences. “A person who is immunocompromised and at risk for fungal infections should be very careful in these settings.”

Treatment-resistant fungal strains on farms closely related to those in hospitals

Brewer and Momany, both members of UGA’s Interdisciplinary Fungal Biology Group (, led a team that collected samples of soil, plant material and of compost at 56 sites in Georgia and Florida. Most sites had recently been treated with a mixture of fungicides including azoles and other fungicides that are only used in agriculture, not in patients. But two of the sites were organic and hadn’t used fungicides in over a decade.

After collecting strains of A. fumigatus, the researchers found 12 that were highly resistant to azoles used in agriculture and medicine. All 12 strains also exhibited high levels of resistance to two non-azole fungicides that are not used to treat humans.

Researchers used whole genome sequencing to create a genetic family tree for A. fumigatus environmental and patient strains. They found that the azole resistance mechanisms they had identified in strains from agricultural settings matched what they had observed in patients. Azole-resistant strains from patients were also resistant to non-azole fungicides that are never used in humans, showing that these strains were in agricultural environments before patients became infected.

“Strains that come from the environment and from people are very closely related to each other,” Brewer said. “It’s not like different strains develop resistance in people and in the environment. It’s all the same. So people who have these resistant infections likely acquired them from the environment.

Desperate need for new environmentally friendly fungicides

Of the 25 multiazole-resistant strains included in the study, eight from agricultural backgrounds and 12 from patients were also resistant to non-azole agricultural fungicides. These multi-fungicide resistant strains originated from agricultural settings in the United States and India and from clinical settings in the United States, the Netherlands and India.

A. fumigatus that is resistant to multiple fungicides is all over the world, both in the environment and in the clinic,” Momany said.

“This emergence dramatically limits the usefulness of fungicides for managing plant pathogens while preserving the clinical utility of azoles,” Brewer said. “We urgently need effective agricultural fungicides that are not toxic to the environment and that do not lead to the rapid development of widespread resistance in the clinic.”

Reference: Kang SE, Sumabat LG, Melie T, Mangum B, Momany M, Brewer MT. Evidence for the agricultural origin of multi-antimicrobial resistance in Aspergillus fumigatus, a fungal pathogen of humans. G3: Genes Genome Genet. 2022;12(2):jkab427. doi:10.1093/g3journal/jkab427

This article was republished from the following materials. Note: Material may have been edited for length and content. For more information, please contact the quoted source.


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