Prevalence of azole-resistant Aspergillus fumigatus isolates in southern England

Yuyi Zhang - As part of my MSc Epidemiology course at Imperial College London, I undertook a research project involving fieldwork, lab work and DNA sequencing analysis, with Prof. Mat Fisher as my primary supervisor and Dr. Thomas Sewell as my co-supervisor. The primary aim of my project was to determine the prevalence of azole-resistant Aspergillus fumigatus isolates in southern England. We also characterised the susceptibility profiles of the environmental isolates towards medical azoles, along with the underlying resistance mechanisms, and investigated the genetic relationships between isolates.

Environmental sampling locations

A. fumigatus is an opportunistic human pathogen which is ubiquitous in nature. It is the most common species responsible for aspergillosis, a group of diseases caused by Aspergillus infection. in recent years, azole antifungal drug resistance in A. fumigatus has emerged, often conferred by the presence of environmentally linked resistance mechanisms. These resistant isolates have been recovered from both clinical and environmental samples, suggesting an environmental acquisition of azole resistance in A. fumigatus isolates infecting patients.

An azole resistant A. fumigatus colony isolated from a soil sample

During May to July 2018, Thomas and I collected soil samples from 16 sites across southern England, including soil and compost samples obtained from public gardens, parks, cemeteries, and flowerbeds outside hospitals in central London and Bath, as well as flowerbeds around Stonehenge, remote forested regions in the New Forest National Park, a lavender farm in Surrey, a wheat farm, and open space surrounded by farmland in Cambridgeshire.

We observed that the environmental azole-resistant A. fumigatus prevalence in South England is at the lower end of the range found in other European countries. However, high prevalence of azole-resistant A. fumigatus was observed in the urban areas of London and Bath, with clusters of resistant strains surrounding the hospitals. This finding has strong clinical implications, suggesting that changes in clinical primary therapy for aspergillosis treatment may be required. The isolates recovered for this project will be subjected to further studies with the aim of establishing the genetic relatedness and links between environmental and clinical strains in the UK.

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