Contribution of the internal transcribed spacer regions to the detection and identification of human fungal pathogens

Abstract

Fungi are morphologically and phylogenetically diverse. There identification is largely based on phenotypic methods. Thus, related species, phenotypic variants and rare species may be unidentified. So, molecular methods have been introduced for identification of pathogenic molds to overcome these problems. In this study, we report the contribution of molecular tools (PCR sequencing) to identify fungal pathogens in both clinical and environmental samples. A total of 82 mold isolates were used (50 clinical samples and 32 environmental samples). PCR and direct sequencing, targeting the internal transcribed spacer (ITS) regions, were performed. We employed comparative sequence analysis to identify molds by using the GenBank database. 89% of isolates were identified by phenotypic methods. PCR- sequencing allowed the fungal identification in all cases. The concordance between molecular and morphological identification was obtained for 33 cases (40.2%). In 36 cases (43.9%), the molecular study gave the exact species identification. PCR sequencing allowed as revising mycological identification for 13 fungi strains (15.9%). The concordance of identification at species level by phenotypic method and by sequence analysis was obtained for 28% of clinical samples and for 59% of environmental samples. The phylogenetic tree for the ITS sequences showed six different clusters that are composed of isolates belonging to the same genus or species. PCR sequencing has been shown to be useful for the detection of the presence of fungal DNA in both environmental and clinical samples. It is rapid and more sensitive for the identification of medically important fungi.

Keywords: Identification; Molds; PCR; Sequence analysis.