Investigating pleuromutilin-producing Clitopilus species and related basidiomycetes

Pleuromutilin is a broad-spectrum antibiotic that has been used in veterinary medicine for over 20 years, but is now gaining interest as a human therapeutic. The compound is a fungal secondary metabolite, but there is some degree of confusion within the literature concerning which species may produce pleuromutilin, with several differently named fungi reported to make the compound. Here, we describe a taxonomic survey of publicly available cultures known to produce pleuromutilin, and other similar species. The pleuromutilin production of these strains was assessed and a phylogenetic assessment was carried out based on the sequence of the nuclear rRNA internal transcribed spacer region. Eleven strains were confirmed as being pleuromutilin producers and all of these isolates appear to fall within a discrete clade of the genus Clitopilus. The phylogenetic analysis also highlights the need for a revision of the taxonomic status of these fungi.