Abstract: Objective To compare the cariability of the Trichophyton rubrum strains isolated from different members by PCR in the same family and to determine the dermatophytosis were transmitted within the family or infected from outside.Methods Scales scraped from patients with dermatophytosis in the same family were inoculated on SDA.T.rubrum was identified by physiological and morphological characteristics.If strains from different patients were found to belong to the same species, RAPD and specific amplification of tandem repeat sub-elements (TRSS) in strain typing were performed and the products were compared.Methods All the strains isolated from 16 patients in 8 families (2 patients per family) were identified as T.rubrum by morphological methods. In 4 families, distinction was identified by RAPD with 4 arbitrary primers. In 5 families the isolates from each family were found to be different in the types of fingerprints produced by amplifying the TRS-1 region specifically. Fingerprints of TRS-2 amplified from isolates differred in 2 families. In all differences were found in strains from 6 families.Conclusions Dermatophytosis in one family is more frequently infected from outside than inside. Fingerprints produced by specifically amplifying TRS-1 are more effective in distinguishing strains of T.rubrum spp than RAPD, and TRS-1 is more suitable for strain typing in T.rubrum.RAPD combimed with TRSS may distinguish T.rubrum strains to maximum.

Key words: Trichophyton rubrum, molecular typing, family