Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 1999
Publication Date: N/A
Interpretive Summary: Filamentous fungi that produce nonmotile spores within an enclosed spore case are classified as Zygomycota. These fungi include many economically important species used in the fermentation of a wide range of organic compounds and in the food industry. Because some Zygomycota are pathogens of humans and other animals that can result in fatal infections, there is an urgent need to develop molecular tools to distinguish between beneficial and harmful strains rapidly and accurately. In this study we have taken advantage of recent advances in automated DNA sequencing technologies to develop an electronically portable DNA sequence database for all medically important Zygomycota. The DNA sequence data was used to design species-specific molecular tools that can be used to fingerprint those taxa most commonly isolated from fungal infections of humans and other animals. These molecular tools have the potential to be used in an assay for the rapid and accurate identification of these fungi from clinical samples. Results of this study illustrate the power of DNA sequence data in developing molecular diagnostic tools for the rapid detection and accurate identification of medically important fungi.
Technical Abstract: A molecular database for all clinically-important Zygomycota was constructed from nucleotide sequences from the nuclear small subunit (18S) ribosomal DNA and domains D1/D2 of the nuclear large subunit (28S) ribosomal DNA. Parsimony analysis of the 42 aligned 18S and 28S DNA sequences was used to investigate phylogenetic relationships among Zygomycota reported to cause infections in humans and other animals and related species most commonly cultured as contaminants with emphasis on members of the Mucorales. The molecular phylogeny provided strong support for the monophyly of the Mucorales, exclusive of Echinosporangium transverale and Mortierella spp. which are currently misclassified within the Mucorales. Micromucor ramannianus, traditionally classified within Mortierella, and Syncephalastrum racemosum represent the basal most divergences within the Mucorales. Based on the 18S gene tree topology, two mycotic taxa, Absidia corymbifera and Rhizomucor variabilis, appear to be misplaced taxonomically. Absidia corymbifera is strongly supported as a sister group of a Rhizomucor miehei-R. pusillus clade while R. variabilis is nested within Mucor. The aligned 28S sequences were used to design 13 taxon-specific PCR primer pairs for those taxa most commonly implicated in mycotic infections. All of the primers specifically amplified DNA of the size predicted based on the DNA sequence data from the target taxa; however, they did not cross-react with phylogenetically related species. These primers have the potential to be used in a PCR assay for the rapid and accurate identification of the etiological agents of Mucormycoses and Entomophthoromycoses.