Has clinical resistance to fungicides been proven?

10 February 2022 | Muriel Cozier

‘This emergence severely limits the usefulness of fungicides to manage plant pathogens while still preserving the clinical usefulness of azoles.’

Researchers from the University of Georgia, US, say that they have, ‘for the first time,’ shown that compounds used to fight fungal diseases in plants are causing resistance to antifungal medications used to treat people. Publishing their work in the journal G3: Genes, Genomes, Genetics, the research focused on Aspergilus fumigatus, the fungus that causes aspergillosis, which leads to life threatening infections impacting 300 000 people around the world each year. The study linked the agricultural use of azoles – used to fight fungal disease in plants – to the reduced effectiveness of clinical azoles used to treat fungal infections in patients.

The research team collected samples of soil, plant material and compost from 56 sites in Georgia and Florida. Most of the sites had recently been treated with a mix of fungicides including azoles and other fungicides only used in agriculture. The samples included two organic sites, where fungicides had not been used in more than a decade.

Using whole genome sequencing, a genetic family tree for A. fumigates strains from the environment and from people was created. The researchers found that the mechanisms of azole resistance indentified in the strains from agricultural environments, matched what they saw in patients. The azole-resistant strains from patients were also resistant to non-azole fungicides that are never used on people this, said the researchers, indicates that these strains had been in the agricultural environments before patients were infected.

The researchers noted that it is not unusual to find A. fumigates in the environment, it is airborne and everywhere. While most people breathe it in without a problem, it can cause serious infections in people who have weakened immune systems.

Marin T Brewer a corresponding author of the study and an associate professor of mycology in the College of Agricultural and Environmental Sciences said; ‘The strains that are from the environment and from people are very closely related to each other…So people who have these infections that are resistant have likely acquired them from the environment.’ Brewer added ‘This emergence severely limits the usefulness of fungicides to manage plant pathogens while still preserving the clinical usefulness of azoles. We urgently need effective agricultural fungicides that aren’t toxic to the environment that do not lead to the rapid development of widespread resistance in the clinic.’

During 2017, Derek Holloman, a member of SCI’s Agrisciences Committee, released a report detailing the emergence azole resistance.

DOI: 10.1093/g3journal/jkab427

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