Zoonotic and Anthropophilic Trichophyton mentagrophytes Complex Infection in Human: An Update and Narrative Review

Abstract

Background: Trichophyton mentagrophytes species complex comprises dermatophytes responsible for common superficial fungal infections affecting keratinised tissues. Recent shifts in taxonomy and increasing antifungal resistance-necessitate an updated understanding of this fungal complex.

Objective: This narrative review provides a comprehensive update on the taxonomy, host immune response and clinical genotyping of the T. mentagrophytes complex, with a focus on zoonotic and anthropophilic infections in humans.

Methods: A comprehensive literature search was conducted across PubMed and Scopus using MeSH terms and relevant keywords related to T. mentagrophytes, T. interdigitale, and T. indotineae. Eligible English-language publications up to March 2025-including original research, case reports, reviews and guidelines-were included.

Results: The T. mentagrophytes complex includes several genotypes with distinct transmission profiles. Genotypes III/III* are primarily zoonotic; genotype VII is sexually transmitted, especially in MSM populations; genotype VIII (T. indotineae) is anthropophilic and associated with terbinafine resistance. Infection involves keratinocyte adhesion, enzymatic skin barrier degradation and activation of pro-inflammatory cytokines and antimicrobial peptides. Both innate and adaptive immunity, particularly Th1 and Th17 responses, are critical for fungal clearance, whereas chronic infections are associated with impaired T-cell function and skewed Th2 responses.

Conclusion: Emerging genotypes and drug resistance within the T. mentagrophytes complex pose increasing clinical challenges. Awareness of transmission patterns, immune evasion mechanisms and resistance profiles is essential for accurate diagnosis and effective management of dermatophytosis.

Keywords: T. mentagrophytes; Trichophyton indotineae; Trichophyton interdigitale; antifungal resistance; polymerase chain reaction.

FIGURE 1

Colony morphology of Trichophyton mentagrophytes on Sabouraud dextrose agar, showing rapidly growing, powdery to granular, white colonies with a slightly raised, concentric surface and a cream to yellowish reverse. The colony appearance is characteristic of the T. mentagrophytes complex.

FIGURE 2

Lactophenol cotton blue preparation at 40× magnification showing microscopic features of Trichophyton mentagrophytes complex. (A) Septate hyphae with numerous spherical microconidia arranged in grape‐like clusters and spiral hyphae. (B) Similar findings with the presence of a characteristic cigar‐shaped, multicellular macroconidium.

FIGURE 3

Genotypic diversity in the Trichophyton mentagrophytes complex. Each species within the complex is colour‐coded. Red and pink highlight anthropophilic genotypes within the predominantly zoonotic T. mentagrophytes. Purple indicates a mixed T. mentagrophytes/T. interdigitale genotype.

FIGURE 4

Stages of Trichophyton mentagrophytes complex infection in human skin. The diagram illustrates the fungal lifecycle from initial skin inoculation, germ tube formation and stratum corneum invasion to completion of the life cycle with spore production.

FIGURE 5

Inflammatory tinea manuum caused by Trichophyton mentagrophytes complex, presenting as well‐demarcated erythematous plaques with vesiculopustular lesions and scaling on the palmar surface.