Direct species identification of common pathogenic dermatophyte fungi in clinical specimens by semi-nested PCR and restriction fragment length polymorphism.

OBJECTIVE: To seek a rapid and reliable molecular biology method to identify the common pathogenic dermatophyte fungi from clinical samples.
METHOD: The genome DNA was extracted from cultured strains of seven common dermatophyte fungi species and part of each positive clinical specimen by microscopy. Intergenic spacer regions of ribosomal DNA (ITS) were amplified by semi-nested PCR (snPCR) with three universal primers (NS5, ITS1, and ITS4) for fungi. The amplified products were digested with two restriction endonucleases (BciT130 I, Dde I), the Restriction Fragment Length Polymorphism(RFLP). The rest of each clinical specimen was cultured in Sabouraud's Agar medium. Then the results of RFLP were compared with the traditional culture results.
RESULTS: The digestion of seven common dermatophyte fungi produced seven different restriction profiles. Restriction profiles of 17 clinical specimens matched, respectively, to that of the cultured strains, and 14 profiles of the 17 ones matched the culture result completely. The coincidence was 100.0%.
CONCLUSIONS: snPCR-RFLP analysis of intergenic spacer regions of ribosomal DNA is a valuable method of exactness and clarity for species identification of common dermatophyte fungi from clinical specimens.