ITS sequencing for identification of pathogenic fungi and discovery ofa novel fungal species

Abstract

Eleven fungal strains were received from the clinical microbiology laboratory collection of Queen Mary Hospital and Pamela Youde Nethersole Eastern Hospital in Hong Kong from 2010-2011. The collection comprised of ten ascomycetes and one zygomycete. They were identified down to the genus level based on the morphological criteria. Internal transcribed spacer (ITS), beta-tubulin, actin and 28S gene sequencing were used for genotypic characterization. The ITS sequences of four of the strains demonstrate <3%-base difference to a single fungal species. They were species of the genus, Acremonium, Aspergillus, Cladophialophora and Ochroconis respectively. Five strains belonging to the genus, Trichophyton, Monascus, Mucor, Arthrinium and Acremonium could not be identified to the species level due to low interspecies heterogeneity. The tubulin gene was used for two of the strains. The tubulin sequence of a strain of Phaeoacremonium was identified to the species level with 0%-base difference. The ITS, partial beta-actin and 28S rDNA genes were sequenced for a strain of Exophiala. They showed a distinct cluster, mostly closely related to, but distinct from, Exophiala xenobiotica, Exophiala jeanselmei and Exophiala oligosperma. The genotypic characteristics suggest the strain to be a novel species of Exophiala. More genotypic and phenotypic characterization are required to described this strain of Exophiala.