Genetic variation of Aspergillus fumigatus from Auckland, New Zealand

Abstract

Aspergillus fumigatus is a globally present opportunistic fungal pathogen that plays a key role in degrading organic matter. A. fumigatus can cause a vast array of diseases, collectively known as aspergilloses. The most serious of these is invasive aspergillosis, that has a mortality rate of 30 to 95% with treatment. Recent studies have indicated that the global A. fumigatus population consists of multiple divergent genetic clusters that are broadly distributed geographically. However, most of the previously analyzed samples have come from continental Eurasia and the Americas where the effects of historical or contemporary gene flow is difficult to distinguish. My thesis project, therefore, focused on analyzing the genetic diversity of the Auckland, New Zealand A. fumigatus population, as it is geographic distant from all previously analyzed populations. Here, we obtained 104 A. fumigatus isolates from Auckland and compared the genotypes of these isolates to population data obtained from nine other countries from Europe, Africa, North America, and Asia. The goal was to analyze the potential effects of historical differentiation and gene flow within this population. We determined that the Auckland population had a low, non-significant level of differentiation compared to most previously surveyed global populations. However, the Auckland population also contained unique genetic elements not present within populations from other geographic regions. Though the hypothesis of random recombination was rejected, we found abundant evidence for phylogenetic incompatibility and recombination within the Auckland A. fumigatus population. Lastly, we identified two triazole resistant strains within the Auckland population, with one carrying the common TR34/L98H cyp51A mutation. Our results suggest that contemporary gene flow, likely due to anthropogenic factors, is a major force shaping the New Zealand A. fumigatus population. These results contribute to our understanding of the high levels of gene flow observed within and among many geographic populations of A. fumigatus.