Researchers from Imperial College London report this week that elevated levels of azole resistant Aspergillus fumigatus isolates are present in urban environments, particularly in flower beds close to hospitals.
Aspergillus fumigatus is an opportunistic fungal pathogen which thrives in decaying vegetation and soil. It can cause a number of conditions ranging from fungal asthma to invasive aspergillosis associated with a mortality rate of 40-90%.
Resistance to antifungal drugs, specifically azoles, is an increasing problem and it has been suggested that the broad application of azoles to agricultural crops is the primary contributing factor. Few studies have sought to investigate resistance in the UK across a diverse range of substrates.
The team from Imperial sampled soil from several environments, from remote forests to hospital flower beds, in order to determine the prevalence of azole resistant isolates in the south of the UK.
Resistance was detected in 6.7% of the soil samples, with urban areas showing a higher prevalence (13.8%) than rural sites (1.1%). This contradicts the hypothesis that resistance is driven by the environmental application of azoles in arable agriculture. In fact in this study, of the 53 samples collected directly on or surrounding agricultural land, zero azole-tolerant isolates were identified.
Rather, the team found that the prevalence of resistance was higher in urban city centres, specifically flower beds and gardens, a finding that lends itself more readily to the hypothesis that the expanding range of azole resistant A. fumigatus stems more from the distribution and cultivation of horticultural crops, such as flowers, ornamentals and vegetables. A particularly concerning discovery was the repeat isolation of resistant isolates from flower beds surrounding city centre hospitals. Concerns over the use of azole treated flower bulbs has been raised before.
This is of particular concern because of the ability of A. fumigatus to cause serious, life threatening infections in immunocompromised patients. The authors suggest that the use of azole-treated plant bulbs in the environment around hospitals should be reconsidered and wider global monitoring of resistance is warranted due to the threat that this pathogen poses to diverse groups of susceptible patients.
The team are currently processing soil samples that have been collected from across the whole of the UK by the public as part of a citizen science experiment. The results of this project will add further data and information to this concerning topic.