Diversity of coelomycetous fungi in human infections: a 10-year experience of two European reference centres

Abstract

25The coelomycetous fungi are difficult to properly identify from their phenotypic 26 characterization and their role as etiologic agents of human infections is not clear. We 27 studied the species distribution of these fungi among clinical isolates that had been 28 collected and stored over a ten-year period in two European reference laboratories 29 (France and Spain). We identified phenotypically and molecularly 97 isolates by 30 sequencing the D1-D2 fragment of the 28S nrRNA (LSU) gene. Species of the orders 31 Pleosporales and Glomerellales were present in both collections, and Botryosphaeriales 32 and Diaporthales only in the French one. The most prevalent species were Medicopsis 33 romeroi, Neocucurbitaria keratinophila, Neocucurbitaria unguis-hominis and 34 Paraconiothyrium cyclothyrioides, which had been recovered primarily from superficial 35 tissues. The Didymellaceae was the most common family represented, with 27 isolates 36 distributed into five genera. 37 38 40 41 Human infections by coelomycetous fungi are rare and poorly characterized due 42 to the difficulty in identifying these fungi using only phenotypic tools. The 43 coelomycetous fungi are characterized by the production of conidia into fruiting bodies 44 (= conidiomata), and were originally included in the orders Sphaeropsidales and 45 Melanconiales of the class Coelomycetes, taxa which today lack scientific validity due 46 to the demonstrated polyphyletic character of this sort of fungus (1-3). They cause 47 superficial or subcutaneous infections, mostly following a traumatic inoculation of 48 contaminated plant material or soil particles during agricultural work in tropical and 49 subtropical areas (4-6). The most common coelomycetous fungi involved in these 50 infections are the etiologic agents of black-grain eumycetoma, such as Biatriospora 51 mackinnonii; Falciformispora spp., Medicopsis romeroi, and 52 Pseudochaetosphaeronema larense. Other common coelomycetous fungi include 53 Lasiodiplodia theobromae and Neoscytalidium dimidiatum (synanamorph of 54 Hendersonula toruloidea) (7-11), which typically cause onychomycosis, subcutaneous 55 phaeohyphomycosis (12-15), and eumycetoma (16). In addition, many species of 56 Phoma and Pyrenochaeta have been reported as occasional agents of localized and 57 systemic infections in humans (9, 17-20). The taxonomy of several coelomycetous 58 genera mentioned before have been revised recently but they still constitute a group of 59 highly polyphyletic taxa that are usually difficult to identify phenotypically (2, 21-24). 60 In a recent study conducted in the USA, Valenzuela-Lopez et al. (6) identified 61 230 fungal strains by sequencing the D1-D2 domains of the 28S rRNA gene (LSU), 62 from which 152 (66.1%) strains belonged to the order Pleosporales, the rest being 63 distributed in several orders of the phylum Ascomycota. Most of these strains were 64 recovered from superficial tissue. Neoscytalidium dimidiatum, Paraconiothyrium 65 cyclothyrioides and members of the family Didymellaceae were the most...