Therapeutic Updates on the Management of Tinea Corporis or Cruris in the Era of Trichophyton Indotineae: Separating Evidence from Hype-A Narrative Review

First Report of Trichophyton indotineae Infection in Hungary

Trichophyton indotineae is associated with difficult-to-treat, often extensive dermatophytosis and resistance to the commonly used antifungal agents. Successful therapy often necessitates higher than usual doses of systemic therapy for prolonged periods. The spread of this species has gained much attention lately, as several European and other Western hemisphere countries have recently reported their first respective cases or increasing numbers of them. Until recently, this species was not described in Hungary. Here, we report a case caused by this species in a patient with a travel history to an endemic region. The isolate was identified preliminarily by MALDI-TOF mass spectrometry and confirmed by DNA sequencing; furthermore, it was subject to phenotypic antifungal susceptibility testing by broth microdilution to fluconazole, voriconazole, posaconazole, itraconazole, and terbinafine. According to the susceptibility results, the isolate was wild type to all tested agents, including terbinafine which was in line with the sequencing data, and with the uncommon excellent therapeutic response to topical allylamine treatment. This case also further confirms the applicability of the MSI-2 database for the rapid identification of T. indotineae in routine clinical microbiology laboratories as a cost-effective and simple method.

The world crisis of terbinafine-resistant Trichophyton indotineae until 2024: do we have enough knowledge?

Dermatophytoses is a well-known name among dermatologists due to its high prevalence among various ages of humans. It is mainly caused by skin-infecting fungi called dermatophytes. From these dermatophytes, Trichophyton indotineae is a newly virulent species with high prevalence and multidrug properties. It was first described in the Indian subcontinent as a closely genetically related strain to Trichophyton interdigitale and Trichophyton mentagrophytes, and spread quickly worldwide. Terbinafine has been utilized for the treatment of dermatophytosis caused by T. indotineae owing to the development of resistance to azole in many of its strains. Wide use of terbinafine has also induced later the development of terbinafine-resistant strains of T. indotineae. Point mutations in the squalene epoxidase (SQLE) gene, which lead to single or multiple substitutions in amino acid positions in the encoded protein (SQLE), are the main reason for antifungal resistance in T. indotineae. This review aims to determine the background of terbinafine-resistant strains of T. indotineae and where they are currently located.

Antifungal resistance in dermatophytes - review of the epidemiology, diagnostic challenges and treatment strategies for managing Trichophyton indotineae infections

INTRODUCTION

There is an increasing number of reports of Trichophyton indotineae infections. This species is usually poorly responsive to terbinafine.

AREAS COVERED

A literature search was conducted in May 2024. T.indotineae infections detected outside the Indian subcontinent are generally associated with international travel. Reports of local spread are mounting.As a newly identified dermatophyte species closely related to the T. mentagrophytes complex with limited genetic and phenotypic differences, there is an unmet need to develop molecular diagnosis for T. indotineae. Terbinafine has become less effective as a first-line agent attributed to mutations in the squalene epoxidase gene (Leu393Phe, Phe397Leu). Alternative therapies include itraconazole for a longer time-period or a higher dose (200 mg/day or higher). Generally, fluconazole and griseofulvin are not effective. In some cases, especially when the area of involvement is relatively small, topical non-allylamine antifungals may be an option either as monotherapy or in combination with oral therapy. In instances when the patient relapses after apparent clinical cure then itraconazole may be considered. Good antifungal stewardship should be considered at all times.

EXPERT OPINION

When both terbinafine and itraconazole are ineffective, options include off-label triazoles (voriconazole and posaconazole). We present four patients responding to these newer triazoles.

An update on antifungal resistance in dermatophytosis

INTRODUCTION

The reports of resistance to antifungal agents used for treating onychomycosis and other superficial fungal infections are increasing. This rise in antifungal resistance poses a public health challenge that requires attention.

AREAS COVERED

This review explores the prevalence of dermatophytes and the current relationship between dermatophyte species, their minimum inhibitory concentrations (MICs) for terbinafine (an allylamine) and itraconazole (an azole), and various mutations prevalent in these species. The most frequently isolated dermatophyte associated with resistance in patients with onychomycosis and dermatophytosis was T. mentagrophytes. However, T. indotineae emerged as the most prevalent isolate with mutations in the SQLE gene, exhibiting the highest MIC of 8 µg/ml for terbinafine and MICs of 8 µg/ml and ≥ 32 µg/ml for itraconazole.Overall, the most prevalent SQLE mutations were Phe397Leu, Leu393Phe, Ala448Thr, Phe397Leu/Ala448Thr, and Lys276Asn/Leu415Phe (relatively recent).

EXPERT OPINION

Managing dermatophyte infections requires a personalized approach. A detailed history should be obtained including details of travel, home and occupational exposure, and clinical examination of the skin, nails and other body systems. Relevant testing includes mycological examination (traditional and molecular). Additional testing, where available, includes MIC evaluation and detection of SQLE mutations. In case of suspected terbinafine resistance, itraconazole or voriconazole (less commonly) should be considered.