Species identification of dermatophytes isolated from human superficial fungal infections by conventional and molecular methods

Abstract

Dermatophyte identification is based on the detection of fungal elements by direct microscopy of clinical specimens combined with culture-based full identification. Phenotypic identification includes macromorphological, micromorphological, and physiological characteristics of the colonies. In the last few years, molecular approaches have been proven to be useful for identification of dermatophyte species. To investigate the conventional and molecular methods used for identification of dermatophytes. Fifty-five specimens collected from human dermatophytosis cases were subjected to mycological examination. Isolated dermatophytes were identified by phenotypic methods. Molecular identification was done using PCR amplification of internal transcribed spacer (ITS1 and ITS4), followed by restriction fragment length polymorphism using the restriction endonuclease enzyme MvaI, application of PCR using single repetitive oligonucleotide [(GACA)4], and DNA sequencing. The obtained dermatophyte isolates (n=48) identified by phenotypic methods were as follows: 15 Microsporum canis, 12 Trichophyton violaceum, 12 Trichophyton rubrum, 5 Epidermophyton floccosum, and 4 Trichophyton mentagrophytes. However, restriction fragment length polymorphism using MvaI and repetitive (GACA)4 molecular methods identified 19 dermatophyte isolates identical to those classified by phenotypic methods. DNA sequencing reidentified one isolate formerly determined to be T. rubrum into Trichophyton raubitschekii. Although the molecular method is rapid and represents technological advancement in the identification of dermatophytes, it is too expensive to be used as a routine method and needs more effort. We recommend its use in the absence of skilled mycologists or in atypical and variants of dermatophytes.