Susceptibility and Diversity in the Therapy-Refractory Genus Scedosporium

Abstract

Scedosporium species show decreased susceptibility to the majority of systemic antifungal drugs. Acquired resistance is likely to disseminate differentially with the mode of exchange of genetic material between lineages. Inter-and intraspecific diversities of Scedosporium species were analyzed for three partitions (rDNA internal transcribed spacer gene [ITS], partial ␤-tubulin gene, and amplified fragment length polymorphism profiles), with the aim to establish distribution of resistance between species, populations, and strains. Heterogeneity of and recombination between lineages were determined, and distances between clusters were calculated using a centroid approach. Clinical, geographic, and antifungal data were plotted on diversity networks. Scedosporium minutisporum, Scedosporium desertorum, and Scedosporium aurantiacum were distinguished unambiguously in all partitions and had differential antifungal susceptibility profiles (ASP). Pseudallescheria fusoidea and Pseudallescheria ellipsoidea were indistinguishable from Scedosporium boydii. Pseudallescheria angusta took an intermediate position between Scedosporium apiospermum and S. boydii. Scedosporium boydii and S. apiospermum had identical ASP. Differences in (multi)resistance were linked to individual strains. S. apiospermum and S. boydii showed limited interbreeding and were recognized as valid, sympatric species. The S. apiospermum/S. boydii group, comprising the main clinically relevant Scedosporium species, consists of separate lineages and is interpreted as a complex undergoing sympatric evolution with incomplete lineage sorting. In routine diagnostics, the lineages in S. apiospermum/S. boydii are indicated with the umbrella descriptor "S. apiospermum complex"; individual species can be identified with rDNA ITS with 96.3% confidence. Voriconazole is recommended as the first-line treatment; resistance against this compound is rare.

Scedosporium apiospermum Otitis Complicated by a Temporomandibular Arthritis: A Case Report and Mini-Review

“…Since 1899 and the first reported case of human scedosporiosis, which was strikingly an ear infection [1,2], only about 20 cases have been reported. We have reviewed 15 literature cases of S. apiospermum or S. boydii otitis [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In cases that occurred before the molecular biology period, identification was only based on colony features and microscopic morphology.…”

“…Recently, MALDI-TOF mass spectrometry has been proposed as a fast and accurate method for species identification within the S. apiospermum complex [24]. It is particularly important to discriminate S. apiospermum from L. prolificans, due to L. prolificans resistance to voriconazole [13][14][15][16].…”

Discriminative potential of some PCR-based and biochemical methods at Scedosporium strains

“…Pseudallescheria ellipsoidea CBS 301.79 e (see f-ITS profile) e belonged to the group of S. boydii e actually, copies more-less the findings by Lackner et al (2014a) that P. ellipsoidea forms the subgroup in the one of S. boydii. The f-CBH and PCR DGGE located P. ellipsoidea together with the species "Pseudallescheria" angusta.…”

“…The f-CBH and PCR DGGE located P. ellipsoidea together with the species "Pseudallescheria" angusta. Based on the data by Lackner et al (2014a) when P. angusta is supposed to be the intermediate between Scedosporium apiospermum and S. boydii, these two PCR approaches seemed to be not sensitive enough to distinguish all forementioned molecular nuances. Or, said another way: precious taxonomic position of the items still called "Pseudallescheria" needs the deepest insight by reliable combination of up-to-date techniques to be refined finally.…”

“…The position of P. angusta group was then verified with a centroid approach based on ITS versus BT2. Finally, it was concluded P. angusta represented an intermediate between S. boydii and S. apiospermum (Lackner et al 2014a). The ITS marker showed its versatility also in an automatized approach for clustering other fungal pathogens and food-related yeasts (Chen et al 2000;Krakov a et al 2012a).…”