Apples can help store and transmit drug-resistant pathogens

When they are prepared for transport, apples and other fruits are often treated with fungicides that protects them against spoilage and extends their shelf life. While this practice is useful for preserving the fruits’ freshness, it nevertheless may help select and boost the transmission of multi-drug resistant pathogenic yeasts, according to a team of researchers led by the University of Delhi in India and McMaster University in Canada.

The scientists examined the surface of 84 fruits representing nine different tree fruit types that were collected between 2020 and 2021 from regions in northern India. These fruits included 62 apples – 20 freshly picked from orchards and 42 purchased from a market in Delhi. 

The researchers found that 13 percent of the apples contained traces of Candida auris, a multi-drug resistant pathogenic yeast that currently poses an urgent threat to public health worldwide, according to the Centers for Disease Control and Prevention (CDC). All of the apples on which the pathogen was found had been stored before purchase, and most probably treated with fungicides to remain fresh.

C.auris was first discovered in Japan in 2009, and has subsequently spread to all inhabited continents, causing significant outbreaks in hospitals and other healthcare facilities. Since some strains are resistant to all available classes of antifungal drugs, this pathogen is highly difficult to treat and may soon become a global menace. 

While the forces that drive the simultaneous emergence of multiple distinct clusters of C.auris all over the world are not yet fully understood, this new study suggests that apples could be a selective force for the pathogen, helping it spread and become more resistant to medicines. 

“When we look at human pathogens, we tend to look at what’s immediate to us,” said study co-lead author Jianping Xu, a professor of Biology at the McMaster University. “But we have to look at it more broadly. Everything is connected, the whole system. Fruit is just one example.” 

Further research is needed to clarify what types of fruits are helping spread the pathogen, what is the role of fungicides in making it resistant to multiple drugs, and which are the current pathways of global transmission. 

The study is published in the journal mBio.

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By Andrei Ionescu, Earth.com Staff Writer