Species distinction in the Trichophyton rubrum complex
【摘要】：Background: The Trichophyton rubrum species complex comprises commonly encountered dermatophytic fungi with worldwide distribution. The members of the complex usually have distinct phenotypes in culture and cause different clinical symptoms despite high genome similarity. Objective: In order to better delimit species within the complex, molecular, phenotypic and physiological characters were combined to re-establish a natural species concept. Results: Three groups T. rubrum, T. soudanense, and T. violaceum could be distinguished based on the sequence of the rDNA ITS barcode gene. On average, strains within each group were similar in colony appearance, microscopy and physiology, but showed significant differences between groups. T.rubrum strains had higher keratinase activity, whereas T. violaceum strains tended to be more lipophilic; however,none of the phenotypic features were diagnostic. The results of matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF) and amplified fragment length polymorphism(AFLP) were partially consistent with the ITS data, but failed to distinguish species unambiguously. Conclusion: Despite their close similarity, T. violaceum, T. soudanense and T. rubrum can be regarded as independent species with distinct geographical distribution and clinical predilection. Trichophyton soudanense is intermediate between T. rubrum and T. violaceum in both genetics and phenotypes. For routine diagnostics, ITS sequencing is recommended.