If you follow our PhD student Jenny on Twitter you may have noticed she recently launched her second citizen science mycology project #SummerSoilstice, to take place on Summer Solstice day 2019 (Friday 21st June). This project is asking volunteers to send in soil samples from their garden so Jenny can culture spores from Aspergillus fumigatus – a fungal species commonly found in soil due to its important role as a decomposer – and determine their resistance to azole fungicide drugs. It is a follow-on from Jenny’s 2018-19 project #ScienceSolstice, which looked for azole-resistant A. fumigatus in samples of air collected from the homes and workplaces of citizen scientists on solstice and equinox days throughout the year.
A fumigatus spores pose no risk to most people as they are cleared by our bodies’ immune system, but some individuals suffer debilitating allergic responses caused by hypersensitisation to the inhaled spores. If spores are not cleared they can germinate in the lung where the growing fungus secretes toxins and triggers an immune response, leading to symptoms such as weight loss, chronic cough and breathlessness, and resulting in a diagnosis of aspergillosis. In individuals with a compromised immune response- such as those with HIV/AIDS or cystic fibrosis or undergoing organ transplant or chemotherapy- spores may enter the bloodstream via the lungs and disseminate through the body, resulting in a life-threatening illness called invasive aspergillosis (IA).
Aspergillosis and IA are treated with drugs containing azole compounds but infections are much harder to treat if caused by azole-resistant Aspergillus fumigatus spores. As the structure of the azole compounds used in medical drugs are similar to azoles used in fungicide sprays in agriculture and horticulture, it is possible that spores are acquiring resistance in the environment prior to being inhaled as well as in the lung as a result of long-term treatment.
The idea behind these projects is to determine the background levels of azole-resistant A. fumigatus spores in air and soil across the U.K. and therefore get an idea of the exposure of citizens to these spores as they go about their daily routines. Knowing the location and timing of each sample will allow Jenny to look for clusters of resistance and any associations with land use, soil type, urban versus rural location and seasonality, which could identify areas to avoid for individuals at high risk of developing aspergillosis.
It is currently known that industrial composters constitute a “hotspot” for A. fumigatus growth because of the heat generated in the centre of the waste piles during the composting process, which kills most bacteria and fungi but allows the thermophilic A. fumigatus to thrive. These facilities accept organic waste from households, restaurants and shops and also from plant nurseries, landscaping companies and farms, from which the plant matter may have been exposed to azole-containing fungicides during its lifetime. An important early stage of the composting process is digestion of the organic matter by microbes that require oxygen so the waste piles are rotated to allow for the circulation of air, thereby mixing the contents and exposing more to azole residues from the commercial and agricultural waste. This practice makes it more likely that A. fumigatus proliferating in the centre of the piles is exposed to azoles during its growth, which may cause it to develop resistance.
It is possible that the compost heaps we keep in our gardens act in a similar manner but on a smaller scale, and that the azole residues that drive resistance are coming from the plants and bulbs we have planted in our garden that have been sprayed with or dipped in azoles at some point during their lifetime. Many industrial composters supply compost to farms and garden centres so it is also possible that the bags of compost we use in our gardens already contain azole-resistant A. fumigatus spores as a result of the composting process.
Whilst Jenny would like as many citizen scientists as possible to take part in this project, it is important to recognize that compost and compost heaps potentially contain high numbers of A. fumigatus that may be aerosolized as a result of disturbing the bag or heap. Due to this, please do not participate in sample collection from these locations if you suffer from aspergillosis, or have a lung condition (chronic or acute, such as ‘flu) or are immunosuppressed, all of which places you at greater risk of contracting aspergillosis from inhaling a large number of spores.
Thank you to the 380 volunteers who have signed up! The pack will contain two clear plastic sachets, a wooden spatula, a poster, simple instructions and a questionnaire and will arrive in the fortnight prior to Friday 21st June (summer solstice 2019). All you need to do is collect two soil samples from your garden – either from a compost heap, bag of compost or manure, pot, planter or border – and return them in the freepost envelope along with a completed questionnaire.
Jenny will process the soil samples in the lab and culture from them any A. fumigatus spores present, which she will then test for resistance to tebuconazole (the third most-sprayed azole in agricultural fungicides here in the UK). If you have indicated on the questionnaire that you are happy to receive updates she will send you an email once all the samples have been processed with a link to a Google map showing anonymized locations of the samples and how many spores were present in each.
Thanks for your interest!