PCR Fingerprinting for Identification of Common Species of Dermatophytes

Classical identification of dermatophytes relies on morpho-logical and physiological characteristics. The search for these characteristics often makes their identification long and labo-rious. In addition, phenotypic features can frequently vary from strain to strain or the organism can become devoid of distinguishing features. In the last few years, genotypic approaches to identification have proven to be useful in solving taxonomic problems re-garding dermatophytes. In fact, genotypic differences are con-sidered more stable and more precise than phenotypic char-acteristics (2, 3). In one of our preceding studies (1), we demonstrated the possibility of identifying various species of common dermato-phytes and related fungi by PCR fingerprinting utilizing the simple repetitive oligonucleotide (GACA)4 as a single primer (4). This primer appeared able to amplify all the strains that we tested and produced species-specific profiles for Microsporum canis, Microsporum gypseum, Trichophyton rubrum, Trichophy-ton ajelloi, and Epidermophyton floccosum, while intraspecific variability was not observed for these species. Three different profiles were observed in the Trichophyton mentagrophytes group (1). We felt that the capacity of this primer to produce species-specific profiles together with the simplicity of the method and the reproducibility of the results (when one strictly maintains experimental conditions) could be exploited for identifying colonies that do not present species-specific morphological characteristics and are not identifiable with the classical meth-ods (1). In particular, PCR fingerprinting could be useful for identifying the following: (i) very young colonies, (ii) colonies which have lost the morphological characteristics typical of the species, and (iii) dead strains. To verify the first hypothesis, 12 strains from the Institut Pasteur collection (M. canis IP 2289-94 and IP 2145-93, T