Abstract
Species of the genus Scedosporium (family Microascaceae, phylum Ascomycota) are responsible for a wide range of opportunistic human infections, and have a low susceptibility to most antifungal drugs. It is well known that the pattern of Scedosporium species distribution varies according to geographic region. To assess the diversity of Scedosporium species in Argentina involved in human infections, we carried out a retrospective study reviewing 49 strains from clinical samples sent for diagnosis to the National Clinical Mycology Reference Laboratory between 1985 and 2019. Then, a phenotypic characterization, a phylogenetic study and and in vitro susceptibility test to antifungals were carried out. An analysis of combined nucleotide sequences dataset of the internal transcribed spacer of the ribosomal DNA (ITS) and of a fragment of the β-tubulin gene (BT2) demonstrated that 92% of the strains belonged to the species S. boydii, S. apiospermum and S. angustum, all them pertaining to S. apiospermum species complex. However, two strains (4%) were identified as S. aurantiacum, a species never reported in clinical settings in the Americas’. Surprisingly, one of them displayed a polycytella-like conidiogenesis, up to date only reported for S. apiospermum. In addition, the strain DMic 165285 was phylogenetically located far away from the rest of the species, so is proposed as the novel species Scedosporium americanum. On the other hand, from all seven antifungals tested, voriconazole and posaconazole were the most active drugs against Scedosporium spp.
Highlights
The Microascaceae is a monophyletic family of highly polymorphic fungi that includes the genera Acaulium, Cephalotrichum, Fairmania, Fuscoannellis, Gamsia, Kernia, Lomentospora, Lophotrichus, Microascus, Parascedosporium, Petriella, Petriellopsis, Pithoascus, Pseudoscopulariopsis, Scedosporium, Scopulariopsis, Wardomyces, Wardomycopsis and Yunnania [1,2,3]
A Basic Local Alignment Search Tool (BLAST) search using internal transcribed spacer (ITS) sequences identified most of our fungal strains as S. boydii (33/49 strains), followed by S. apiospermum (12/49), S. aurantiacum (2/49), and S. dehogii and S. ellipsoideum
Forty-five of the isolates (92%, 45/49) were placed into the S. apiospermum species complex clade A (1 posterior probability (PP)/97% bootstrap support (BS)), and distributed across several terminal clades: A terminal clade (1 PP/77% BS) containing the type strains of S. boydii and S. ellipsoideum, included 28 of our strains, displaying a relatively high intraspecific genetic variation; another twelve strains were placed into a terminal clade (1 PP/96% BS) containing the type strain of S. apiospermum, with a relatively high intraspecific genetic variation, and a third terminal clade (1 PP/94% BS) included the type strain of S. angustum and four of our strains
Summary
The Microascaceae is a monophyletic family of highly polymorphic fungi that includes the genera Acaulium, Cephalotrichum, Fairmania, Fuscoannellis, Gamsia, Kernia, Lomentospora, Lophotrichus, Microascus, Parascedosporium, Petriella, Petriellopsis, Pithoascus, Pseudoscopulariopsis, Scedosporium, Scopulariopsis, Wardomyces, Wardomycopsis and Yunnania [1,2,3]. Some of these genera are well-known human opportunistic human pathogens. Over the last two decades Scedosporium spp. have become increasing prevalent in immunocompromised patients, despite being better known for causing post-traumatic infections in healthy people [4]. Scedosporium spp. infections occur by traumatic implantation of contaminated materials (e.g., wood chips), or can be acquired by inhalation of contaminated aerosols [16,17]
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