A Study On Stibility And Genetype Of Common Dermatophytes

Among the Trichophyton, T. Mentagrophyes and T. rubrum are the commoest pathogen of dermatomycosis. They cause not only a variety of superficial mycosis, including onychomycosis, tinea cruis and tinea pedis, but also deep infections, such as kerion, abscess and granuloma. It is estimated that the easy recurrence of Trichophyton onychomycosis following an appropriate course of treatment is due primarily to reinfection with a new strain. Objective and Significance:Due to susceptible variation of dermatophytes colonial morphology, pigmentation, physiological and biochemical characteristics, we explore the stability of phenotype and genotype of Trichophyton rubrum during conservation or subculture, analysing the effect on variations which subculture brought and whether the variations are reversible. On the premise of that genotype of T. rubrum is stable, southern blotting analysis of ribosomal-DNA intergenic spacer regions and PCR technique were adopted to study the DNA typing of T. rubrum and T. Mentagrophyes, analysing the relation between genotype and phenotype, clinical manifestations, and different geographical areas. Methods and Results:207 T. rubrum strains were conserved for one year in our mycology laboratory. 10 strains isolated from clinical samples recently and one standard isolate conserved in American Types Culture Collection were subcultured three or twenty times at an interval of two or four weeks on Sabouraud agar slopes. The phenotyping of all the strains was based on colonial morphology and pigment of medium. After these strains were conserved for one year,fifty-four strains showed mophological variations.Eleven strains showed various variations in colonial morphology or pigment during subculture.We made a conclusion that the phenotype of T.rubrum was instable during conservation and subculture.An attempt was made to explore the DNA typing of 11 strains and corresponding second to forth subcultured strains by RAPD and tDNA RFLP-Southem blotting methods. PCR and hybridization patterns were stable when the strains were subcultured. PCR technique was performed to amplify ribosomal conserved regions(partial 5.8S,ITS-2) ,TRS-1 and TRS-2 repeat units respsctively from template DNA of the 6 strains end the twentith subcultured strains by using three primer pairs, then depurating , reclaiming, and gene sequence analyses. Specific amplifiation of TRS-1 and TRS-2 produced strain-characteristic band and no differences appeared between 6 original T. rubrum strains and the corresponding twentith subcultured...