Genetic Diversity and Dispersal of Aspergillus fumigatus in Arctic Soils.

Gregory A Korfanty,Haoran Jia,Jianping Xu,Heather Yoell,Mykaelah Dixon

doi:10.3390/genes13010019

Abstract

Aspergillus fumigatus is a saprophytic mold and an opportunistic pathogen with a broad geographic and ecological distribution. A. fumigatus is the most common etiological agent of aspergillosis, affecting over 8,000,000 individuals worldwide. Due to the rising number of infections and increasing reports of resistance to antifungal therapy, there is an urgent need to understand A. fumigatus populations from local to global levels. However, many geographic locations and ecological niches remain understudied, including soil environments from arctic regions. In this study, we isolated 32 and 52 A. fumigatus strains from soils in Iceland and the Northwest Territories of Canada (NWT), respectively. These isolates were genotyped at nine microsatellite loci and the genotypes were compared with each other and with those in other parts of the world. Though significantly differentiated from each other, our analyses revealed that A. fumigatus populations from Iceland and NWT contained evidence for both clonal and sexual reproductions, and shared many alleles with each other and with those collected from across Europe, Asia, and the Americas. Interestingly, we found one triazole-resistant strain containing the TR34 /L98H mutation in the cyp51A gene from NWT. This strain is closely related to a triazole-resistant genotype broadly distributed in India. Together, our results suggest that the northern soil populations of A. fumigatus are significantly influenced by those from other geographic regions.

Highlights

Aspergillus fumigatus is a thermotolerant ascomycete mould with a ubiquitous presence around the world
This study investigated the population structure of the opportunistic fungal pathogen A. fumigatus obtained from northern climates above 60◦ latitude
Our study revealed significant genetic diversity with evidence of both clonal and sexual reproduction within both regional populations

Summary

Introduction

Aspergillus fumigatus is a thermotolerant ascomycete mould with a ubiquitous presence around the world. Its primary ecological niche is within decaying plant matter and soil It is a common opportunistic fungal pathogen capable of infecting both immunocompetent and immunocompromised humans. Depending on the underlying conditions of patients and the effectiveness of antifungal management, the mortality of invasive aspergillosis ranges from 40% to 90%. For both treatment and prophylaxis, triazole antifungals such as itraconazole, voriconazole, posaconazole, and isavuconazole are often used for frontline therapy. Triazole antifungals target the enzyme lanosterol 14α-demethylase encoded by the gene cyp51A. This enzyme is required for the biosynthesis of ergosterol, an essential sterol in the cytoplasmic membrane of fungal cells. Aside from the triazoles, two other antifungal classes, the polyene amphotericin B and the echinocandins, are used for salvage therapy of aspergillosis, especially in the case of triazole-resistance [9]

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