Diversity of cutaneous infections by non-dermatophytic moulds and the discovery of novel fungal species

Abstract

Fungal cutaneous infection is referred as infection of skin, hair or nails by fungus. Three groups of fungi can cause cutaneous infection: yeasts, dermatophytes and non-dermatophytic moulds. Dermatophytes are the most common causative agents, but the non-dermatophytic moulds have the highest diversity. Most of the clinical microbiology laboratories in Hong Kong identify these fungal pathogens based on phenotypic method, which is labor intensive, time consuming, difficult to distinguish within genera and may be inaccurate, especially for those uncommon pathogens. Comparative sequence analysis provides a rapid and accurate method to resolve these problems. In this study, 6 non-dermatophytic moulds isolated from clinical cutaneous specimen were identified using ITS region and 28S rDNA sequencing technique. Four strains were correctly identified to species level: Purpureocillium lilacinum, Chaetomium globosum, Exophiala oligosperma and Cephalotheca foveolata. For the remaining two strains which could not be identified by ITS region and 28S rDNA, further sequencing of 18S rDNA, Actingene, β-tubulin gene, EF1-αgene and Calmodulin gene were done. Results indicated that these two strains were not belonged to any existing fungal species, and was suggested to be a novel species of Ochroconis and Gliomastix respectively. Further phenotypic characterizations are required for these two strains for proposing as a novel species.