Identification of pathogenic fungal isolates by ITS sequencing

Abstract

In clinical microbiology laboratories, the conventional method for identification of pathogenic fungi is based on fungal culture and observation of fungal phenotypic characters. However, it is time-consuming, subjective and unreliable due to the long incubation period and variations in fungal colony morphology. Thus, there is a need for a rapid, objective and accurate identification of pathogenic fungal isolates. ITS regions are most commonly used targets for molecular identification of fungal pathogens because of the optimal inter- and intra-species variations and large copies in fungal genome. In this study, twenty-two clinical fungal isolates were identified using the phenotypic method and ITS sequencing. The results showed that there were only thirteen isolates identified to species level by phenotypic method, while others were only differentiated in genus level. Due to the poor differentiation based on the conventional phenotypic approach, misidentification of fungal pathogens occasionally occurred. However, ITS sequencing successfully achieved accurate species-level identification of all fungal isolates. The results were demonstrated in phylogenetic trees with high bootstrap support. In conclusion, ITS sequencing is a rapid and reliable for the identification of pathogenic fungal isolates.