Majocchi'S Granuloma: Autoinoculation And Adaption Of Trichophyton Rubrum With Molecular Evidence

Background Trichophyton rubrum, an important aetiological agent of superficial dermatophytosis, occasionally penetrates into deeper tissues, causing inflammation and a granulomatous response. Only few case reports of T. rubrum granuloma with molecular evidence for autoinoculation have been published. Objectives To find the genetic basis of adaptation to a different microhabitat following autoinoculation of Trichophyton rubrum. Methods A case of Majocchi's granuloma is reported, with isolation of T. rubrum strains from foot and chin, respectively. Whole-genome sequencing of the two strains has been performed. Phylogenetic reconstruction and SIFT analysis were conducted. Results A phenotypic difference has been observed between the two isolates. 20 and 19 indels, 8 and 15 SNVs were found in foot and chin strains, respectively. Foot and chin strains formed a monophyletic group. Two non-synonymous mutations of chin strains were observed in the TERG_06754 gene encoding cytochrome c peroxidase (CCP). The G293C amino acid change in TERG_03373 was predicted to affect protein function significantly. The mutated amino acid (cysteine) was only found in the chin strain in all dermatophyte non-redundant sequences. Conclusions Non-synonymous mutations located in TERG_06754 and TERG_03373 were predicted to affect protein functions, which may facilitate the adaption for invasion of the superficial cutaneous strain. As the different living environments of these two strains (oxygenous, lower-temperature for the pedal strain; hypoxia, higher-temperature for the chin strain), a stratum corneum-to-dermal adaption hypothesis of T. rubrum was proposed.