Molecular differentiation of dermatophyte fungi

Our previous studies of the ribosomal DNA variation in dermatophytes have s hown that these fungi are monophyletic in origin. However, this approach di d not allow; us to differentiate all the species defined by classical means . Therefore, we studied the internal transcribed spacer 1 (ITS 1) region of 17 species of tbp fungal order Onygenales, comprising the pathogenic kerat inophilic fungi. Interspecific nucleotide composition and sequence length V ariation of the ITS 1 region was high, mean identities were as low as 40% a nd sequence lengths varied from 169 to 293 basepairs. Each established derm atophyte species could be identified. In contrast, the flanking sequences a t the 3' end of 18S and the 5.8S rDNA were conserved. Although the value of the ITS 1 region as a phylogenetic tool may be limited because of its high variability, it provides the information necessary to design species-speci fic probes, or polymerase chain reaction restriction fragment polymorphism systems useful for taxonomic or rapid diagnostic tests.