06
Apr
Conventional Apples Found to Be Coated in Fungicides and Drug-Resistant Fungi
(Beyond Pesticides, April 6, 2022) Conventional apples sold at market and sprayed with synthetic fungicides may not only contain drug-resistant fungi, but function as a transmission reservoir and route to spread these dangerous pathogens, finds research published in mBio late last month by a team of researchers from India and Canada. As reports of fungal resistance rise, particularly in hospitals and among the immunocompromised, 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 coauthor Jianping Xu, PhD. “But we have to look at it more broadly. Everything is connected, the whole system. Fruit is just 1 example.”
Researchers set out their research with the suspicion that stored fruits sprayed with synthetic fungicides were acting as a source and route of transmission for the deadly fungi Candida auris. This yeast is considered an “emerging fungal pathogen” by the U.S. Centers for Disease Control and Prevention (CDC), and has increased its rate of infection significantly since its initial identification in the mid 1990s. The fungi has been found in every continent save Antarctica. It has proven to be particularly dangerous to the elderly and those with pre-existing conditions, and can spread rapidly through hospital settings, nursing homes, and long-term care facilities.
To test their suspicions, researchers purchased 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. Overall, eight (13%) of apples had the presence of C. auris on its surface. All of the isolates were found in stored fruits purchased at market, while those purchased directly from the orchards contained no pathogenic fungi.
Fungicides were found to be present on every apple that also contained C. auris, and included a range of different classes with varying modes of action. This included triazole fungicides (such as tebuconazole, difenoconazole, sulfentrazone, and flusilazole), methyl benzimidazole carbamates (such as carbendazim and thiabendazole), phthalimides like captan, pyridinecarboxamides like boscalid, aromatic amines like diphenylamine, the phenolpyrrole fludoxonil, and quinone outside inhibitors (like kresoxim-methyl and pyraclostrobin). (See Beyond Pesticides Pesticide Gateway for more information about each active ingredient). However, the presence of fungicides was generally evenly distributed between those found with and without drug-resistant pathogenic C. auris. Fresh fruit from neither conventional nor organic orchards contained C. auris, but only organic apples were free of any fungicide residue, while conventional apples were contaminated with two or three fungicides on each fruit. Further isolation and culture of C. auris apples found them to have reduced sensitivity to commonly found triazole fungicides.
“Fungicides used in agriculture may inadvertently select the drug-resistant fungi,” said study author Anuradha Chowdhary. Based on their results, the scientists conclude that stored apples sprayed with fungicides are acting as a reservoir and source of transfer for C. auris. Because the fungi was only found on stored apples, it is likely that there are multiple routes for C. auris contamination, including the potential that pickers or packers within the supply chain handling the fruits transfer the fungus from their hands to the fruit. As the study also notes, “It is plausible that multiple practices, like cryopreservation and wax coating with additional fungicides during the storage of apples, may alter the myco-flora of apples’ surfaces.”
The rise of drug resistant human pathogenic fungus presents a serious threat to human health on a global scale. However, a Freedom of Information Act request shows officials at the U.S. Department of Agriculture working to downplay the role of synthetic fungicide use in chemical agriculture as a factor in the rise of drug-resistant fungal infections worldwide. Not only did USDA work to deny the truth on the ground, but efforts were also made to halt protective actions. Emails showed top level officials at industry trade group CropLife America urging USDA officials to “make certain” that the United Nation’s (UN) Codex Alimentarius, a set of international guidelines and standards established to protect consumer health, made no mention of how fungicides contribute to antibiotic resistance.
As the New York Times reported in 2019, “…the very existence of resistant infections is often cloaked in secrecy. With bacter[ial] and fung[al infections] alike, hospitals and local governments are reluctant to disclose outbreaks for fear of being seen as infection hubs. Even the CDC, under its agreement with states, is not allowed to make public the location or name of hospitals involved in outbreaks. State governments have in many cases declined to publicly share information beyond acknowledging that they have had cases.” In the context of the present study, the source of a pathogen resistant fungal outbreak in a hospital could conceivably be caused by the fruit served in the hospital cafeteria sourced through a global supply chain. Yet as the specter of a massive health threat looms large, officials in the U.S. appear to be working to keep residents in the dark.
Most disturbingly, it is not unheard of for pathogenic fungi to reach epidemic levels in mammals. Over the last ten years 90% of northern long-eared, little brown and tri-colored bat populations have been killed due to White Nose syndrome, caused by exposure to a pathogenic fungi known as Pseudogymnoascus destructans.
As prior research on the development of resistance in agriculture has discovered, the most straightforward solution is the most effective; the only true way to eliminate resistance is to stop using the material causing resistance to occur in the first place. Organically produced apples, purchased directly from the orchard, the study confirms, were the only fruit not to pose a risk from either pesticide exposure or pathogenic fungi. Whenever possible, shop with an eye toward the gold standard for food purchases–local and organic. By buying organic whenever possible, you’ll help support the agricultural system we must continue to adopt for the future of our health and the planet.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: American Society for Microbiology press release, mBio
