Antifungal resistance: From “Big Chicken” to Big Tulip

The Genes to Genomes blog reports on recent research by UGA fungal biologists Michelle Momany and Marin Brewer, who reported in their findings that Aspergillus fumigatus isolated from clinical settings is resistant to agricultural fungicides.

Infections have long been a deadly problem for hospital patients. Though modern medicine has an impressive array of antimicrobial drugs at its disposal, pathogens continue to evolve resistance, creating ever more dangerous infections as the microbial “arms race” escalates.

Overprescribing of antibiotics is one source of resistance, but there could be another culprit further afield. In a new publication in G3: Genes|Genomes|Genetics, fungal biologists Michelle Momany and Marin Brewer report their finding that some strains of a pathogenic fungus apparently acquired antifungal resistance in an agricultural setting rather than a clinical one. Genetic analysis revealed that strains of the fungus Aspergillus fumigatus that were resistant to antifungals used in people had also developed resistance to fungicides used only on plants.

Fungal infections endanger both plants and people

Momany and Brewer are part of the Fungal Biology Group at the University of Georgia, one of the largest fungal biology research groups in the world. Fungal diseases are a major problem both clinically and in agriculture, but doctors generally use different compounds to treat people than farmers use to treat crops. A class of antifungals known as azoles, however, is used in both people and plants. Many different azoles are currently available[MTB1] , and though they are considered “moderate” in terms of the risk of fungi developing resistance, azole-resistant strains of the fungus Aspergillus fumigatus have begun turning up more frequently in hospitals.

Unlike drug-resistant bacteria, which can spread from person to person, A. fumigatus is always picked up environmentally. There’s no documented case of anyone getting sick by breathing in Aspergillus exhaled by an infected patient, says Momany. Because of this, fungal researchers suspected A. fumigatus was evolving azole resistance in the field, rather than in patients. Still, there was no way to know for sure that it wasn’t caused by hospital drugs.

From “Big Chicken” to Big Tulip

“The idea came to me when I was reading the book Big Chicken by Maryn McKenna,” says Brewer. In the book, scientists showed that antibiotic-resistant bacteria had moved from chickens to humans – not the other way around – by showing that bacteria isolated from people contained genetic evidence of resistance to compounds used only in chickens. Brewer decided to apply that same logic to Aspergillus. “I thought it would be interesting to look for the signatures for resistance to fungicides only used in agricultural environments,” she says.

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Image: Photo of Tulips near the Spoorpad, Warmond, the Netherlands, by Flickr user Reinoud Kaasschieter.