Yoshikazu Horie

Taxonomic novelties in Aspergillus section Fumigati : A. tasmanicus sp. nov., induction of sexual state in A. turcosus and overview of related species

The phylogenetic position of two Aspergillus strains isolated from Australian soil and phenotypically resembling A. unilateralis was investigated by using multigene phylogeny based on β-tubulin (benA), calmodulin (CaM), actin (act), and RNA polymerase II second largest subunit (RPB2) genes. The analysis supported their placement into a separate lineage within a well-supported clade containing 10 other members of section Fumigati (“A. unilateralis clade”). Comparisons of extrolite profiles, taxonomically informative morphological and physiological characters were made, and it was discovered that the two strains can be differentiated from all relatives by their low maximum growth temperature, short stipes, and ornamentation of conidia. The data justified the proposal of a new species, A. tasmanius sp. nov. Amplification of mating-type genes showed that the A. unilateralis clade contains five heterothallic species. Only the MAT1-1-1 idiomorph was detected among isolates of A. unilateralis, A. tasmanicus, and A. marvanovae, while isolates having both opposite mating types were detected in A. turcosus and A. nishimurae. The sexual state of A. turcosus was induced by mating experiments and is described in this study. Ascospores of this species were unique by their smooth to finely verrucose convex surface and two well-visible equatorial crests. Some exometabolites detected in A. marvanovae and A. tasmanicus are also indicative of a perfect state, thus supporting the hypothesis that these species have cryptic sexual cycles. The epitype and ex-epitype culture is designated for A. nishimurae to facilitate further taxonomic work with this species.

Severe Chromoblastomycosis-Like Cutaneous Infection Caused by Chrysosporium keratinophilum

Chrysosporium species are saprophytic filamentous fungi commonly found in the soil, dung, and animal fur. Subcutaneous infection caused by this organism is rare in humans. We report a case of subcutaneous fungal infection caused by Chrysosporium keratinophilum in a 38-year-old woman. The patient presented with severe chromoblastomycosis-like lesions on the left side of the jaw and neck for 6 years. She also got tinea corporis on her trunk since she was 10 years old. Chrysosporium keratinophilum was isolated from the tissue on the neck and scales on the trunk, respectively. The patient showed satisfactory response to itraconazole therapy, although she discontinued the follow-up.

Unravelling species boundaries in the Aspergillus viridinutans complex (section Fumigati): opportunistic human and animal pathogens capable of interspecific hybridization

Although Aspergillus fumigatus is the major agent of invasive aspergillosis, an increasing number of infections are caused by its cryptic species, especially A. lentulus and the A. viridinutans species complex (AVSC). Their identification is clinically relevant because of antifungal drug resistance and refractory infections. Species boundaries in the AVSC are unresolved since most species have uniform morphology and produce interspecific hybrids in vitro. Clinical and environmental strains from six continents (n = 110) were characterized by DNA sequencing of four to six loci. Biological compatibilities were tested within and between major phylogenetic clades, and ascospore morphology was characterised. Species delimitation methods based on the multispecies coalescent model (MSC) supported recognition of ten species including one new species. Four species are confirmed opportunistic pathogens; A. udagawae followed by A. felis and A. pseudoviridinutans are known from opportunistic human infections, while A. felis followed by A. udagawae and A. wyomingensis are agents of feline sino-orbital aspergillosis. Recently described human-pathogenic species A. parafelis and A. pseudofelis are synonymized with A. felis and an epitype is designated for A. udagawae. Intraspecific mating assay showed that only a few of the heterothallic species can readily generate sexual morphs in vitro. Interspecific mating assays revealed that five different species combinations were biologically compatible. Hybrid ascospores had atypical surface ornamentation and significantly different dimensions compared to parental species. This suggests that species limits in the AVSC are maintained by both pre- and post-zygotic barriers and these species display a great potential for rapid adaptation and modulation of virulence. This study highlights that a sufficient number of strains representing genetic diversity within a species is essential for meaningful species boundaries delimitation in cryptic species complexes. MSC-based delimitation methods are robust and suitable tools for evaluation of boundaries between these species.