Abstract: Objective To investigate the genotype of Trichophyton rubrum isolated from children and adults with dermatophytosis, and to explore the relationship between the genotype and location of lesions as well as drug susceptability of T. rubrum. Methods Dermatophytes were isolated from 67 children and 88 adults who had been diagnosed with dermatophytosis by microscopy and fungal culture. DNA was extracted from the clinical isolates of T. rubrum and random amplification of polymorphic DNA （RAPD） assay was performed with two random primers, i.e., OPA11 5′ACCCGACCTC3′ and OPD18 5′GAGAGCC AAC3′, respectively. PCR products were subjected to electrophoresis to identify the genotypes of clinical isolates. Broth microdilution method was applied to assess the in vitro susceptibility of T. rubrum isolates to eight antifungal agents: fluconazole, itraconazole, terbinafine, ketoconazole, liranaftate, butenafine, econazole and bifonazole. Results T. rubrum was isolated from 47 children and 62 adults with dermatophytosis. RAPD assay yielded clear and stable DNA band profile. With primer OPA 11, these T. rubrum isolates were classified into 4 genotypes, i.e.,Ⅰa, Ⅱa, Ⅲa and Ⅳa. Both type Ⅰa and Ⅲa represented 41.94% of the T. rubrum isolates from adults, while type Ⅰa 65.96% of those from children; there was a significant difference in the genotype distribution between the two groups （P < 0.05）. Also, the genotype distribution was statistically different for tinea corporis and tinea pedis （P < 0.01, < 0.05 respectively） between adults and children, however, no significant difference was observed for onychomycosis and tinea cruris （both P > 0.05）. In vitro susceptibility test showed that all antifungal agents were effective against these T. rubrum isolates. Among these antifungals, terbinafine had the highest efficacy, and fluconazole exhibited the lowest effect against these isolates. Moreover, a higher efficacy was observed for ketoconazole and fluconazole against T. rubrum of typeⅠa than against other types of T. rubrum, and for bifonazole against T. rubrum isolates of typeⅡa than against other types, while the efficacy of itraconazole was lower against T. rubrum isolates of type Ⅲa than against other types. Conclusions T. rubrum is the main pathogenic microorganism in adults and children with dermatophytosis. In adults, Ⅰa and Ⅲa are the predominate types of T. rubrum associated with dermatophytosis, while Ⅰa is the common type in children. All the 8 antifungals tested have a good efficacy for various genotypes of T. rubrum, whereas the efficacy of fluconazole, itraconazole, ketoconazole, terbinafine and bifonazole varies with the genotypes of T. rubrum.

Key words: RAPD drug susceptability, Susceptibility test