Taxonomy and phylogeny of clinically important mucoralean fungi

Identifier:  TDX:1015

Handle:  https://hdl.handle.net/20.500.11797/TDX1015

Authors:  Álvarez Duarte, Eduardo

Abstract:
Recently, several studies have reported the increasing incidence of mucormycosis in both immunocompromised and immunocompetent patients (Bitar et al., 2009; Roden et al., 2005; Saegeman et al., 2010). Some species belonging to the order Mucorales (subphylum Mucoromycotina) are considered opportunistic pathogens, causing infections with a high mortality rate. Interesting is the epidemiological change observed in both Apophysomyces elegans and Saksenaea vasiformis, two species considered emerging pathogens, with a high clinical relevance in recent years, due to the infection in immunocompetent people. Another relevant aspect is the fact that the Mucorales are resistant to most of the currently available antifungal drugs. Amphotericin B is the only antifungal drug to show potent in vitro activity and in vivo efficacy. Nevertheless, the clinical efficacy remains limited, with high mortality rate, especially when the infections are caused by either Saksenaea vasiformis or Apophysomyces elegans. In the present thesis, we analyzed a large panel of isolates from clinical samples, principally from of the United States of America. We have been able to demonstrate the useful of morphological tools in the identification of mucoralean fungi, obtaining a 92% of correlation with the molecular tools. Additionally, and based on a polyphasic taxonomy approach which included morphology, physiology and DNA sequence analyses, 7 new species of mucoralean fungi have been discovered and described: Apophysomyces ossiformis; Apophysomyces trapeziformis; Apophysomyces variabilis; Mucor ellipsoideus; Mucor velutinosus; Saksenaea erythrospora, and Saksenaea oblongispora.