First case report of tinea corporis caused by Trichophyton indotineae in Latin America

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.

Trichophyton indotineae, an Emerging Drug-Resistant Dermatophyte: A Review of the Treatment Options

Background: Dermatophytosis is a prevalent superficial infection caused by filamentous fungi, primarily affecting the skin and/or its appendages. In recent years, there has been a notable increase in mycotic strains resistant to standard antifungal therapies, including Trichophyton indotineae, a dermatophyte of the Trichophyton mentagrophytes complex. This review aims to provide a comprehensive overview of the treatment options for T. indotineae, elucidating their effectiveness in managing this challenging mycotic infection. Methods: For this review, a search was conducted in the PubMed, Scopus, Web of Science, Embase, and Google Scholar databases, encompassing all published data until March 2024. English-language articles detailing therapy outcomes for patients confirmed to be affected by T. indotineae, identified through molecular analysis, were included. Results: Itraconazole was shown to be a good therapeutic choice, particularly when administered at a dosage of 200 mg/day for 1-12 weeks. Voriconazole was also demonstrated to be effective, while terbinafine exhibited a reduced response rate. Griseofulvin and fluconazole, on the other hand, were found to be ineffective. Although topical treatments were mostly ineffective when used alone, they showed promising results when used in combination with systemic therapy. Mutational status was associated with different profiles of treatment response, suggesting the need for a more tailored approach. Conclusions: When managing T. indotineae infections, it is necessary to optimize therapy to mitigate resistances and relapse. Combining in vitro antifungal susceptibility testing with mutational analysis could be a promising strategy in refining treatment selection.

Terbinafine-resistant Trichophyton indotineae causing extensive dermatophytosis in a returning traveller, London, UK

Severe and antifungal-resistant dermatophyte infections are a growing global public health concern. Trichophyton indotineae, a novel dermatophyte species, has caused an epidemic of severe, difficult-to-treat and recalcitrant dermatophytoses in India and South Asia, where it is now common. We present a case of terbinafine-resistant T. indotineae in London, UK, causing extensive dermatophytosis associated with recent travel to Latin America, outside the previously reported risk area.

Mapping the Global Spread of T. indotineae: An Update on Antifungal Resistance, Mutations, and Strategies for Effective Management

INTRODUCTION

The global spread of Trichophyton indotineae presents a pressing challenge in dermatophytosis management. This systematic review explores the current landscape of T. indotineae infections, emphasizing resistance patterns, susceptibility testing, mutational analysis, and management strategies.

METHODS

A literature search was conducted in November 2023 using Embase, PubMed, Scopus, and Web of Science databases. Inclusion criteria covered clinical trials, observational studies, case series, or case reports with T. indotineae diagnosis through molecular methods. Reports on resistance mechanisms, antifungal susceptibility testing, and management were used for data extraction.

RESULTS AND DISCUSSION

A total of 1148 articles were identified through the systematic search process, with 45 meeting the inclusion criteria. The global spread of T. indotineae is evident, with cases reported in numerous new countries in 2023. Tentative epidemiological cut-off values (ECOFFs) suggested by several groups provide insights into the likelihood of clinical resistance. The presence of specific mutations, particularly Phe397Leu, correlate with higher minimum inhibitory concentrations (MICs), indicating potential clinical resistance. Azole resistance has also been reported and investigated in T. indotineae, and is a growing concern. Nevertheless, itraconazole continues to be an alternative therapy. Recommendations for management include oral or combination therapies and individualized approaches based on mutational analysis and susceptibility testing.

CONCLUSION

Trichophyton indotineae poses a complex clinical scenario, necessitating enhanced surveillance, improved diagnostics, and cautious antifungal use. The absence of established clinical breakpoints for dermatophytes underscores the need for further research in this challenging field.

Recalcitrant dermatophyte infections: identification and risk factors

INTRODUCTION

Recalcitrant dermatophytosis is an emerging phenomenon that occurs worldwide, and Trichophyton indotineae is currently the prominent cause.

MATERIALS AND METHODS

Skin specimens from patients with tinea infection were obtained by scrubbing and then sectioned into three fragments. Two fragments were subjected to direct microscopic examination and culture, while the third portion was utilized in the PCR method.

RESULTS

Isolates were morphologically identified as Trichophyton mentagrophytes/interdigitale complex (n = 60 [83.33%]), Microsporum canis (n = 8 [11.11%]), Trichophyton rubrum (n = 3 [4.16%]), and Epidermophyton floccosum (n = 1 [1.38%]). Among 60 T. mentagrophytes complex isolates, 53 (88.33%) were classified as T. indotineae and seven as T. interdigitale genotype II. The disease duration was longer in the T. indotineae group (P = 0.035). Both Gradient PCR and skin-sampling methods yield similar results in terms of positive and negative cases (P = 1.0000). The time patients stopped their medication did not impact the positive case numbers (P = 0.803). Gender had no effects on the frequency (P = 0.699). Familial contamination, dermatologic disorder, and other underlying conditions did not differ in the two group infections (P > 0.05). Steroid usage is strongly associated with the emergence of tinea infection (P < 0.04). The duration of antifungal administration had a substantial effect on the emergence of resistant organisms (P = 0.05).

CONCLUSIONS

Steroid usage, T. indotineae involvement, and prolonged exposure to antifungals were the solid and influential factors in recalcitrant involvement. Regarding quick and suitable diagnosis and treatment, which is essential in preventing recalcitrant cases, we suggest that direct skin sample PCR can meet the demands.

Effectiveness and safety of oral terbinafine for dermatophyte distal subungual onychomycosis

INTRODUCTION

Terbinafine has been a cornerstone in dermatophyte infection treatment. Despite its global efficacy, the emergence of terbinafine resistance raises concerns, requiring ongoing vigilance.

AREAS COVERED

This paper focuses on evaluating the efficacy and safety of terbinafine in treating dermatophyte toenail infections. Continuous and pulse therapies, with a 24-week continuous regimen and a higher dosage of 500 mg/day have demonstrated superior efficacy to the FDA approved regimen of 250 mg/day x 12 weeks. Pulse therapies, though showing comparable effectiveness, present debates with regards to their efficacy as conflicting findings have been reported. Safety concerns encompass hepatotoxicity, gastrointestinal, cutaneous, neurologic, hematologic and immune adverse-effects, and possible drug interactions, suggesting the need for ongoing monitoring.

EXPERT OPINION

Terbinafine efficacy depends on dosage, duration, and resistance patterns. Continuous therapy for 24 weeks and a dosage of 500 mg/day may enhance outcomes, but safety considerations and resistance necessitate individualized approaches. Alternatives, including topical agents and alternative antifungals, are to be considered for resistant cases. Understanding the interplay between treatment parameters, adverse effects, and resistance mechanisms is critical for optimizing therapeutic efficacy while mitigating resistance risks. Patient education and adherence are vital for early detection and management of adverse effects and resistance, contributing to tailored and effective treatments.