Repositori URV

Identifier: TDX:511

Handle: https://hdl.handle.net/20.500.11797/TDX511

Authors:
Gilgado Barbadilla, Felix

Abstract:
Pseudallescheria boydii is a ubiquitous ascomycetous fungus that causes a wide array of human infections that can affect practically all the organs of the body. These infections have been known for a long time, but in recent years, a marked increase in severe invasive infections has been noticed, mainly in immunocompromised hosts. They present a high mortality rate and are difficult to treat. One of the most typical features of this species, which is very rare in other pathogenic fungi, is its ability to develop sexual structures on routine culture media. Until the present thesis Scedosporium apiospermum was considered the anamorph of P. boydii. Recently, it had been demonstrated that high genetic variation exists within P. boydii and other authors had reported considerable differences with respect to growth and sporulation. All these data seemed to suggest that P. boydii was probably a species complex. For this reason we performed a morphological and molecular study involving numerous strains of clinical and environmental origins and from different countries. The analysis of partial sequences of the β-tubulin (two loci) and calmodulin genes and the internal transcribed spacer region of the rDNA gene demonstrated that P. boydii is a species complex. A combined analysis of the sequences of the four loci of 60 strains from different origins showed 8 phylogenetic species within this species, grouped in 5 different clades. The clades 1 and 2 were described as the new species Scedosporium aurantiacum and Pseudallescheria minutispora, respectively. Clade 5 consisted of four subgroups incorporating the ex-type strains of P. boydii, Pseudallescheria angusta, Pseudallescheria ellipsoidea and Pseudallescheria fusoidea, respectively, and clades 3 and 4 remained unnamed. Lat