Revealing virulence potential of clinical and environmental Aspergillus fumigatus isolates using Whole-genome sequencing

Abstract

Aspergillus fumigatus is an opportunistic airborne pathogen and one of the most common causative agents of human fungal infections. A restricted number of virulence factors have been described but none of them lead to a differentiation of the virulence level among different strains. In this study, we analyzed the whole-genome sequence of a set of A. fumigatus isolates from clinical and environmental origin to compare their genomes and to determine their virulence profiles. For this purpose, a database containing 244 genes known to be associated with virulence was built. The genes were classified according to their biological function into factors involved in thermotolerance, resistance to immune responses, cell wall structure, toxins and secondary metabolites, allergens, nutrient uptake and signaling and regulation. No difference in virulence profiles was found between clinical isolates causing an infection and a colonizing clinical isolate, nor between isolates from clinical and environmental origin. We observed the presence of genetic repetitive elements located next to virulence related gene groups, which could potentially influence their regulation. In conclusion, our genomic analysis reveals that A. fumigatus, independently of their source of isolation, are potentially pathogenic at the genomic level, which may lead to fatal infections in vulnerable patients. However, other determinants such as genetic variations in virulence related genes and host-pathogen interactions most likely influence A. fumigatus pathogenicity and further studies should be performed.\n\nImportanceAspergillus spp. infections are among the most clinically relevant fungal infections also presenting treatment difficulties due to increasing antifungal resistance. The lack of key virulence factors and a broad genomic diversity complicates the development of targeted diagnosis and novel treatment strategies. A widely spread variability in virulence has been reported for experimental, clinical and environmental isolates. Here we provide supporting evidence that members of this species are fully capable of establishing an infection in immunosuppressed hosts according to their virulence content at the genomic level. Due to the possible clinical complications, studies are urgently required linking strains virulent phenotype with the genotype to better understand the virulence activation of this important fungal pathogen.