Fourteen percent of Aspergillus fumigatus isolates cultured from garden soils were resistant to an agricultural triazole antifungal drug, tebuconazole. Tebuconazole resistance confers resistance to medical triazoles that are used to treat aspergillosis, a lung infection that can be serious, which results from inhalation of A. fumigatus spores. The research is published in Applied and Environmental Microbiology, a journal of the American Society for Microbiology.
In the study, which was lead author Jennifer Shelton’s Ph.D. thesis, she and her collaborators found that compost and compost-enriched soils contain high concentrations of A. fumigatus spores.
” The research indicates that compost handling poses a health risk to individuals when they are exposed to large quantities of aerosolizedspores. It raises questions about whether compost bags should have additional warnings, whether compost should not be shipped unsterilized, and whether people should wear masks when handling compost,” stated Shelton.
A novel aspect of this study is that the soil samples–509 of them–were collected from their gardens by 249 citizen scientists whom Shelton enlisted in this effort via social media and through the Aspergillosis Trust, a charity raising awareness of the problem. The samples were all collected on the same day, June 21, 2019. From these, the investigators cultured 5,174 isolates of A. fumigatus. Many of these A. fumigatus isolates contained polymorphisms in the cyp51A gene, which is frequently associated with triazole-resistance. Soil samples containing compost were significantly more likely to grow tebuconazole-resistant A. fumigatus strains than those that did not, and compost samples grew significantly higher numbers of A. fumigatus than other soil samples.
The study was motivated by a growing number of cases caused by triazole resistant A. fumigatus spores in the UK, said Shelton, who conducted the research at Imperial College London and UK Centre for Ecology and Hydrology. “An estimated 185,000-plus people in the UK live with aspergillosis, with conditions ranging from severe hypersensitization, “fungal asthma,” and chronic colonization or invasion of the lungs that can disseminate to other organs including the brain,” said Shelton. “Chronic forms of aspergillosis are life-limiting and difficult to treat, and invasive infections have mortality rates of between 40 and 70 percent, and higher if infected with triazole resistant A. fumigatus.”
People normally inhale spores from the environment, including those of A. fumigatus. Those with weak immunity, due to immune-suppressing drugs, conditions such as diabetes or rheumatoid arthritis, or lung damage from infection by tuberculosis, COVID-19, severe influenza or smoking, are especially vulnerable, but even those without predisposing conditions can deve