Studies of clinical and environmental isolates of Aspergillus fumigatus
thesisposted on 27.03.2017, 09:41 by Joseph Peter Morley
Aspergillus fumigatus is a fungus of great environmental importance as well as being the most common filamentous fungal respiratory pathogen. Airborne A. fumigatus spores can reach potentially dangerous concentrations, particularly in the air around industrial composting sites. Drug resistant A. fumigatus infections are an increasingly common problem and the limited range of drugs available for the treatment of Aspergillus infections means that any resistance developing is a major cause for concern. Mycoviruses may offer an alternative approach to conventional treatment and exist in many fungal populations, including A. fumigatus, but there is little understanding of their importance or the influence they may have on their hosts. Different air samplers used in bioaerosol studies were evaluated. An enrichment protocol for the isolation of mycoviruses from environmental samples was assessed as well as further characterisation and genome sequencing of a mycovirus of the A. fumigatus type strain NCPF7367. For clinical and environmental A. fumigatus collections drug susceptibility was assessed using the EUCAST protocol, virulence compared using a Galleria model and the mating type of the fungi determined by PCR. Significant differences in sampler efficacy were observed. Putative mycoviruses were obtained from environmental samples and sequencing of the NCPF7367 virus genome suggests that this is a capsid-less virus. Increased azole resistance and virulence was found amongst compost-derived A. fumigatus relative to clinical isolates. This study highlights the importance of sampler selection in bioaerosol studies. A novel enrichment procedure for mycovirus isolation from environmental samples appears promising and the genome sequencing sheds new light on the lifecycle of an A. fumigatus mycovirus. The study also suggests that compost-derived A. fumigatus may be less susceptible to azole drugs and more virulent than clinical populations. Drug resistance may be more geographically variable than previously thought and intermediate-level resistance appears not to be mediated by cyp51-A mechanisms.