(Beyond Pesticides, April 5, 2022) Conventional apples sold in the market and sprayed with synthetic fungicides can not only harbor drug-resistant fungi, but also act as a transmission reservoir and route for the spread of these dangerous pathogens, according to a study published late last month by was published in mBio by a team of researchers from India and Canada. As reports of fungal resistance increase, particularly in hospitals and among immunocompromised individuals, there is an urgent need to understand and address the root causes of these emerging disease threats. “When we look at human pathogens, we tend to look at what’s immediate to us,” said study co-author Jianping Xu, PhD. “But we have to look at it more broadly. Everything is connected, the whole system. Fruit is just one example.”
The researchers began their research with the suspicion that stored crops sprayed with synthetic fungicides acted as the source and transmission route for the deadly fungi Candida Auris. This yeast is classified as an “emerging fungal pathogen” by the US Centers for Disease Control and Prevention (CDC) and has significantly increased its rate of infection since it was first identified in the mid-1990s. The fungus has been found on every continent except Antarctica. It has proven to be particularly dangerous for the elderly and those with pre-existing conditions, and can spread quickly in hospitals, nursing homes and long-term care facilities.
To test their suspicions, the researchers bought 62 apples — 10 from an orchard using conventional practices, 10 from an organic orchard, and the rest from a market. Only Red Delicious or Royal Gala apples were purchased for the study. A total of eight (13%) of the apples had the presence of C. auris on its surface. All isolates were found in stored fruit bought from the market, while those bought directly from the orchards contained no pathogenic fungi.
Fungicides were found on every apple that was also included C. auris, and comprised a number of different classes with different modes of action. These included triazole fungicides (such as tebuconazole, difenoconazole, sulfentrazone, and flusilazole), methylbenzimidazole carbamates (such as carbendazim and thiabendazole), phthalimides such as captan, pyridinecarboxamides such as boscalid, aromatic amines such as diphenylamine, the phenolpyrrole fludoxonil, and quinone-external inhibitors (such as kresoxim-methyl and pyraclostrobin). (See Beyond Pesticides Pesticide Gateway for more information on each active ingredient). However, the presence of fungicides was generally evenly distributed between those with and without drug-resistant pathogens C. auris. Contains fresh fruit neither from conventional nor from organic cultivation C. auris, but only organic apples were free of fungicide residues, while conventional apples were loaded with two or three fungicides on each fruit. Further isolation and culture of C. auris Apples were found to have reduced susceptibility to common triazole fungicides.
“Fungicides used in agriculture can inadvertently select the drug-resistant fungi,” said study author Anuradha Chowdhary. From their results, the scientists conclude that storage apples sprayed with fungicides act as a reservoir and source of transmission C. auris. Since the fungus has only been found on stored apples, there are likely multiple routes for it C. auris Contamination, including the possibility of pickers or packers within the supply chain handling the fruit transferring the fungus from their hands to the fruit. As the study also notes, “It is plausible that multiple practices, such as cryopreservation and wax coating with additional fungicides during storage of apples, may alter the mycoflora of apple surfaces.”
The rise of drug-resistant human pathogen fungi poses a serious threat to human health worldwide. However, a Freedom of Information Act request shows that US Department of Agriculture officials are working to understand the role of synthetic fungicide use in chemical agriculture as a factor in the to downplay the global rise in drug-resistant fungal infections. Not only has the USDA worked to deny the truth on the ground, but efforts have also been made to stop protective measures. Emails showed senior officials at industry trade group CropLife America urging USDA officials to “ensure” the United Nations (UN) Codex Alimentarius, a set of international guidelines and standards designed to protect consumer health, made no mention of how fungicides contribute antibiotic resistance.
As the New York Times reported in 2019, “…the mere existence of resistant infections is often cloaked in secrecy. With bacteria[ial] and mushroom[al infections] similarly, hospitals and local governments are reluctant to disclose outbreaks for fear of being seen as sources of infection. Even the CDC, as part of its agreement with states, is not allowed to release the location or names of hospitals involved in outbreaks. State governments have in many cases declined to publicly share information other than acknowledging that they had cases.” In the context of the present study, the source of a pathogen-resistant fungal infection in a hospital could possibly be caused by the fruit that served in the hospital cafeteria and sourced through a global supply chain. But as the specter of a massive health threat looms, officials across the US appear to be working to keep residents in the dark.
Most worryingly, pathogenic fungi are reaching epidemic proportions in mammals. In the past decade, 90% of the populations of northern long-eared, little brown, and tricolored bats have been killed due to white-nose syndrome caused by exposure to a pathogenic fungus known as Pseudogymnoascus destructans.
As previous research into resistance development in agriculture has shown, the simplest solution is the most effective; The only true way to eliminate drag is to stop using the material that caused the drag in the first place. The study confirms that organically produced apples purchased directly from the orchard were the only fruit that posed no risk from pesticide exposure or pathogenic fungi. Whenever possible, shop with an eye on the gold standard of buying groceries – local and organic. By buying organic whenever possible, you are helping to support the farming system we must continue to embrace for the future of our health and the planet.
All unattributed positions and opinions in this article are those of Beyond Pesticides.
Source: American Society for Microbiology press release, mBio