Molecular dynamics of resistance and persistence of Aspergillus fumigatus

Aspergillus fumigatus is an environmental fungus that causes a spectrum of diseases that are very difficult to manage because, despite the available treatments, eradication of the fungus is rarely achieved. We hypothesize that A. fumigatus is adapts to its (micro)environment thus allowing its persistence in the host. One indicator of adaptation is the development of resistance of A. fumigatus to the azole compounds used in antifungal therapy. The acquisition of resistance may come with a fitness cost to the fungus as it adapts to grow only in the presence of the azole. Discontinuation of azole therapy may therefore be an unrecognized, but important, stress factor to the fungus, which causes compensatory mutations to occur to compensate for loss of fitness. These isolates may regain their virulence yet retain the azole-resistant phenotype.

We aim to investigate the dynamics of new and known mutations in A. fumigatus in order to:
1. Uncover the factors that facilitate the early development of adaptation and resistance to azoles.
2. Uncover other stress factors that promote persistence of the fungus.

The project will involve whole genome sequencing and analysis of 13 unique isolates of A. fumigatus collected from a single individual over a 2 year period that exhibit differing azole-susceptibility, colony morphology and growth characteristics. To correlate mutations to specific phenotypes a unique and effective approach of classical genetic tools (sexual crossing and segregation analyses) will be used. Candidate azole-resistance mechanisms will thus be identified and validated using recombination experiments. Mutations associated with phenotypic fitness changes will be correlated to specific pathways and/or phenotypes. In this way we will identify new leads as to the cause of resistance and the mutations that compensate for fitness costs and underpin the development of the azole-resistant phenotype.

Our research will provide important new mechanistic insights that will help us understand azole-resistance and inform novel strategies to prevent and overcome fungal persistence and adaptation. These insights will extend beyond the human setting as Aspergillus diseases affects both plants (crops) and animals and environmental resistance selection is a main concern in agriculture at the moment.