Recent research out of India raises concerns over the transmission risks of a harmful and hard-to-kill fungal infection. The study found drug-resistant strains of Candida auris on apples that had been treated with fungicides. The findings suggest that apples and other fruits dosed with these chemicals can inadvertently fuel the emergence and spread of this germ, which is known to cause deadly outbreaks in hospitals.
C. auris is an emerging pathogen and yeast (microscopic fungus) that was first discovered in 2009. Though most people exposed to it don’t become sick, it can cause a severe infection in some, particularly people who are already sick or immunocompromised. That’s made the fungus a serious threat in hospitals and other health care environments. It’s also often resistant to the few antifungals usable against it. While C. auris outbreaks have been rare, doctors have already come across cases that were resistant to all available drugs, including in the U.S.
Despite its recent emergence in humans, the fungus is thought to have existed in nature for quite some time. Last year, researchers in Canada and India were the first to document it in the wild, living in the warm island regions off India. That same team is behind this latest research, published in mBio in March.
In 2020 and 2021, they collected and sampled the surfaces of 84 fruits that had been grown or sold in India, mostly apples, looking for disease-causing yeasts like C. auris. On eight of these apples (13%), they found a diverse variety of drug-resistant strains of the fungus. None of the apples freshly picked from an orchard had traces of C. auris, however; the apples stored and sold at stores often had other related species of Candida on them as well.
These findings indicate, the study authors say, that the process of treating apples and other fruits with fungicides—often done to keep them from spoiling—is helping foster the growth of these superbugs. A similar phenomenon can be seen in antibiotic-treated livestock or in people who are given antibiotics that don’t clear their entire infection, which then allow drug-resistant strains of bacteria to emerge.
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“Our findings suggest that C. auris in the natural ecosystem may come in contact with agriculture fungicides and that stored fruits could be a significant niche for the selection of azole resistance in C. auris and other human fungal pathogens,” the scientists wrote.
While the team’s research has focused on finding C. auris in India, they warn that it’s not merely a local problem. Indeed, in recent years, outbreaks have been spotted in previously undocumented areas of the world, including Brazil and in new areas of the U.S.
More research is needed to understand the exact risk that fruits and vegetables may play in spreading C. auris and its other routes of exposure. But one thing is certain: It’s increasingly harder to avoid coming across this and other superbugs.
“When we look at human pathogens, we tend to look at what’s immediate to us,” study author Jianping Xu, a microbiologist at McMaster University in Canada, told Indian newspaper The Tribune. “But we have to look at it more broadly. Everything is connected, the whole system. Fruit is just one example.”