Molecular Identification of the Dermatophytes Causing Tinea Diseases Using ITS Sequencing Analysis

Abstract

Background: Tinea is a group of keratinophilic fungal infections caused by dermatophytes that invade
the skin, hair, and nails. As the conventional methods for dermatophytes detection are time-consuming or
lack enough specificity, accurate diagnostic methods such as molecular techniques are required for precise
identification and differentiate between two closely related species of dermatophytes.
Objective: To disclose the useful role of DNA sequencing in the recognition of dermatophytes using the ITS
region and comparing the current local isolates with those provided by the NCBI.
Method: Thirty clinical tinea specimens were collected from the patients between December 2016 and
June 2017. All specimens were examined microscopically then cultured on DTM. Positive dermatophytes’
cultures were confirmed by PCR using ITS1 and ITS4 primers. The PCR products were sequenced for
species-specific dermatophyte identification.
Result: Culture results of 30 specimens revealed predominant positive dermatophytes (23, 77%) comparing
the rest of no growth. The PCR amplification of the 23 dermatophytes for species identification showed
distinct fragment lengths for different species; 550bp for T. tonsurans and T. equinum, 650bp for T.
verrcossum, T. bullosum and M. appendiculatum, 690bp for T. rubrum and T. mentagrophytes, 700bp for
T. interdigitale, and 740bp for M. canis and E. floccosum. Sequencing analysis exhibited a novel local T.
rubrum strain that recorded in the NCBI with accession number (MG786552.1). The genetic compatibility
between the reference strain of T. rubrum in India and the local strain was 99%.
Conclusion: Dermatophytes identification by sequencing analysis of the ITS region is a faster, precise, and
more dependable diagnosis at species and subspecies levels than the conventional laboratory methods.