Microbial forensics: Do Aspergillus fumigatus strains present local or regional differentiation?

Abstract

Microbial community profiling is an important issue for microbial forensics. Some works support a large-scale dispersion of microbes and weak or absent biogeography, while others report the existence of endemic strains. Fungi have recently been used for soil discriminatory and definition of specific ecosystems. The advent of large-scale genotyping studies on fungal populations may provide a unique opportunity to compare genetic diversity within and among populations. In this work, we studied the pathogenic mould Aspergillus fumigatus that is frequently associated to several human disorders. A set of clinical and environmental isolates of A. fumigatus from Hospital S. João (Porto, Portugal) was tested, in addition to another group from other Portuguese and American Hospitals. A. fumigatus isolates were genotyped using a microsatellite-based single-multiplex PCR with eight short tandem repeat markers and a single nucleotide polymorphism (SNP). This SNP could split A. fumigatus population in two groups: 357 isolates with an additional nucleotide A and 55 isolates without this base insertion. The smallest group, comprising 27 genotypes, contained exclusively strains from Hospital S. João. The occurrence of microvariation events (strains differing in a single marker) was very common among environmental isolates. A larger study including more strains from diverse locations may improve the categorisation of local/regional strains. Additionally, the inclusion of more SNPs for A. fumigatus genotyping will improve the characterisation of A. fumigatus population.