Rare malbranchea-like fungal isolates from clinical specimens in United States of America.

The fungi of the order Onygenales can cause important human infections; however, their taxonomy and worldwide occurrence is still little known. We have studied and identified a representative number of clinical fungi belonging to that order from a reference laboratory in the USA. A total of twenty-two strains isolated from respiratory tract (40 %) and human skin and nails (27.2 %) showed a malbranchea-like morphology. Six genera were phenotypically and molecularly identified, i.e. Auxarthron/Malbranchea (68.2 %), Arachnomyces (9.1 %), Spiromastigoides (9.1 %), and Currahmyces (4.5 %), and two newly proposed genera (4.5 % each). Based on the results of the phylogenetic study, we synonymysed Auxarthron to Malbranchea, and erected two new genera: Pseudoarthropsis and Pseudomalbranchea. New species are proposed: Arachnomyces bostrychodes, A. graciliformis, Currahmyces sparsispora, Malbranchea gymnoascoidea, M. multiseptata, M. stricta, Pseudoarthropsis crassispora, Pseudomalbranchea gemmata and Spiromastigoides geomyces, along with a new combination for Malbranchea gypsea. The echinocandins showed the highest in vitro antifungal activity against the studied isolates, followed by terbinafine and posaconazole; in contrast, amphotericin B, fluconazole, itraconazole and 5-fluorocytosine were less active or lacked in vitro activity against these fungi.