Extensive Dermatophytosis Caused by Terbinafine-Resistant Trichophyton indotineae, France

Abstract

Extensive dermatophytosis caused by terbinafine-resistant Trichophyton indotineae harboring Phe397Leu and Leu393Ser substitutions in the squalene epoxidase enzyme was diagnosed in France. Analysis of internal transcribed spacer sequences revealed the wide spread of this species in Asia and Europe. Detection of T. indotineae in animals suggests their possible role as reservoirs.

Keywords: France; Trichophyton indotineae; antimicrobial resistance; dermatophytosis; fungi; genotype VIII; ringworm; skin conditions; squalene epoxidase; terbinafine; zoonoses.

Figure 1

Analysis of dynamic and geographic distribution of Trichophyton indotineae reported sequences from France (this study) and reference sequences from GenBank for 2004–2021 A) Cumulative curves of 486 published sequences; B) geographic distribution of 537 published sequences. Red, countries with reported endemic cases; purple, countries with imported cases (but rare cases of endemic transmission cannot be ruled out); green, probable country sources of imported cases; yellow, countries with reported sporadic human cases without additional available information (also identified in Poland); blue, countries with T. indotineae sequences reported in animal infections (also reported in India). World map was created using JMP Pro 15.2.0 (https://www.jmp.com). For internal transcribed spacer sequence-based screening, we retrieved ITS1-5.8S-ITS2 sequences T. interdigitale, T. mentagrophytes, T. indotineae and also Anthroderma benhamiae, A. simii, A. vanbreuseghemii, T. benhamiae, T. bullosum, T. concentricum, T. equinum, T. erinacei, T. quinckeanum, T. simii, T. schoenleinii, T. tonsurans, and T. verrucosum. For sequences matching T. indotineae (internal transcribed spacer reference sequence JN133999), we searched associated literature on PubMed Central (https://www.ncbi.nlm.nih.gov/pmc).

Figure 2

Trichophyton indotineae susceptibility to terbinafine reported from 4 countries. A) Relationships between terbinafine MIC and codon changes reported in isolates from different countries. Grey line shows terbinafine susceptibility threshold of 0.2 μg/mL. Available MICs were determined using the Clinical Laboratory and Standards Institute (https://clsi.org) or EUCAST (https://eucast.org) methods. Data show mean values. B) Prevalence of substitution points in the gene encoding SQLE. Sources shown in the Appendix. SQLE, squalene epoxidase enzyme.