Application of PCR-RFLP to Rapid Identification of the Main Pathogenic Dermatophytes from Clinical Specimens

Abstract

Background: In the present study, a PCR-RFLP based molecular technique was designed to rapid identification of der­matophytes in clinical specimens. Skin scrapings obtained from human cases suspected to dermatophytosis were studied in or­der to identify involved etiological fungi.
Methods: In this experimental study, the specimens (skin scrapings) of patients referred to Mycology Department of Pas­teur Institute of Iran were inoculated on Petri dishes contained selective agar for pathogenic fungi (SAPF) and incubated at 25º C until visible growth of fungal colonies. The colonies were examined for standard morphological characteristics after visi­ble growth on the agar medium. A small portion of each fungal colony was further studied by restrictionfragment length poly­morphism (RFLP) analysis of the PCR-amplifiedinternal transcribed spacer (ITS) region of ribosomal DNA (rDNA). PCR amplicons were electrophoresed on 2% agarose gel after digesting by different restriction enzymes including MvaI, HinfI and HaeIII.
Results: Among 160 clinical samples examined, 6 dermatophyte species including  Trichophyton mentagrophytes, T. ru­brum, T. verrucosum, T. tonsurans, Microsporum canis and Epidermophyton floccosum were finally identified based on the col­ony morphology and microscopic criteria. Specific PCR products and RFLP patterns for MvaI, HinfI and HaeIII en­zymes allowed the rapid identification and reliable differentiation of isolated dermatophytes at the genus or species level for 5-10 day-old colonies.
Conclusions: The results showed that PCR-RFLP analysis of the ITS region of rDNA is a rapid and reliable tool which al­lows identification of major pathogenic dermatophytes isolated in this study at species level in young 5-10 day-old colonies.