Molecular Identification of Zygomycetes from Culture and Experimentally Infected Tissues

Abstract

Mucormycosis is an emerging infection associated with a high mortality rate. Identification of the causative agents remains difficult and time-consuming by standard mycological procedures. In this study, internal transcribed spacer (ITS) sequencing was validated as a reliable technique for identification of Zygomycetes to the species level. Furthermore, species identification directly from infected tissues was evaluated in experimentally infected mice. Fifty-four Zygomycetes strains belonging to 16 species, including the most common pathogenic species of Rhizopus spp., Absidia spp., Mucor spp., and Rhizomucor spp., were used to assess intra- and interspecies variability. Ribosomal DNA including the complete ITS1-5.8S-ITS2 region was amplified with fungal universal primers, sequenced, and compared. Overall, for a given species, sequence similarities between isolates were >98%. In contrast, ITS sequences were very different between species, allowing an accurate identification of Zygomycetes to the species level in most cases. Six species ( Rhizopus oryzae , Rhizopus microsporus , Rhizomucor pusillus , Mucor circinelloides , and Mucor indicus ) were also used to induce disseminated mucormycosis in mice and to demonstrate that DNA extraction, amplification of fungal DNA, sequencing, and molecular identification were possible directly from frozen tissues.