Wednesday 19 January 2022

Exploring the link between compost and pathogen Aspergilli


Fourteen percent of Aspergillus fumigatus isolates cultured from garden soils were found to be 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.


In the study, researchers found that compost and compost-enriched soils contain high concentrations of A. fumigatus spores.



A novel aspect of this study is that the soil samples -- 509 -- were collected from gardens by 249 citizen scientists. 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. While many 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,.


The data suggests that handling compost and compost-enriched soils exposes individuals to large numbers of spores and that behavioral changes on their part, and action taken by the composting industry could reduce these exposures.


Journal Reference:


Jennifer M. G. Shelton, Roseanna Collins, Christopher B. Uzzell, Asmaa Alghamdi, Paul S. Dyer, Andrew C. Singer, Matthew C. Fisher. Citizen-science surveillance of triazole-resistant Aspergillus fumigatus in UK residential garden soils. Applied and Environmental Microbiology, 2022; DOI: 10.1128/AEM.02061-21


Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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