Clinical and environmental Aspergillus: morphological and molecular characterization, phylogeny, and antifungal susceptibility profile

Identifier:  TDX:2631

Handle: https://hdl.handle.net/20.500.11797/TDX2631

Authors:  Zen Siqueira, Joao Paulo

Abstract:
Aspergillus is one of the most common and ubiquitous genus of Ascomycetes, inhabiting a great diversity of environmental substrates. The main objective of this thesis was to contribute to the better knowledge of this genus, exploring the species diversity in clinic and environmental substrates. A total of 433 isolates were studied in this thesis, which were obtained from different sources (clinical samples, soil, dung, plant debris). The identification of the isolates was carried out by multilocus phylogenetic analyses including sequences of four markers (ITS, β-tubulin, calmodulin, and RPBII) and phenotypic characterization. When relevant, clinical isolates were submitted to antifungal susceptibility testing against the main drugs available. In summary, 98 species of Aspergillus were identified, 49 from clinical samples (248 isolates), 48 from soil (92 isolates), 48 from herbivore dung (82 isolates), and 10 from plant debris (10 isolates). Considering the poorly studied sections of Aspergillus in the clinical setting, the most frequent sections were Nidulantes (including the former Versicolores section), 84 isolates and 14 species; Circumdati, 35 isolates and seven species; Aspergillus, 25 isolates and five species; and Usti, 19 isolates and two species. Eight species were isolated from clinical samples for the first time and three were proposed as new. The antifungal drugs, in general, showed good activity against the isolates tested, with exception of the reduced activity of amphotericin B against members of section Circumdati. Regarding the environmental isolates, 14 new species were proposed based on phenotypic and molecular data; five belonging to the section Terrei (three from herbivore dung and two from soil); four to the section Candidi (all from dung); two to the section Nidulantes (both from soil); and one in each of the sections Flavipedes, Cremei, and Usti (all from dung).