In this section
By Dr Riina Richardson
Clinical Head of Service and Consultant Medical Mycologist
and Dr Caroline Moore
Principal Clinical Scientist
September 2025
Trichophyton indotineae
Over the period 2017–2024, the United Kingdom has seen a marked rise in infections due to Trichophyton indotineae, an antifungal‑resistant dermatophyte initially reported in South Asia around 2014. It was originally identified as a variant of T. mentagrophytes, but it is now recognised as a distinct species within the T. mentagrophytes species complex, which includes:
- mentagrophytes (various genotypes, including genotype VII)
- interdigitale
- indotineae
Of the 157 confirmed cases of Trichophyton indotineae infection reported in the UK by July 2024, patients most often presented with lesions in the groin, buttocks, and thighs (43%) and adjacent trunk regions (12%). Some 85% of cases had links to endemic areas, such as South Asia by ethnicity or travel, although 74% had no recent travel history, suggesting local transmission. Many isolates were resistant to terbinafine, while most remained susceptible to alternatives such as itraconazole. Standard treatment duration using microbiologically effective treatment is two to four weeks, but for example scalp infections may require up to three months of treatment.
Trichophyton mentagrophytes genotype VII (TMVII)
Separately but concurrently, the Trichophyton mentagrophytes genotype VII (TMVII) strain has emerged as an increasingly recognised sexually transmissible dermatophyte, particularly among men who have sex with men, as flagged up by UKHSA recently. TMVII infections often present as inflamed, itchy lesions in the genitals, buttocks, or face. Cases have been documented across Europe (including France and Spain) with evidence of local transmission. Though typically responsive to terbinafine, successful treatment often requires longer courses (months) of systemic antifungals from the outset, even in cases with localised disease, as initial topical treatment has been associated with worsening of the lesions.
Diagnosis
T. indotineae and T. mentagrophytes (including TMVII) are diagnosed using a combination of patient history, clinical evaluation, microscopy, and culture of skin scrapings (not swabs) from affected areas. Due to genetic similarity, molecular techniques are required to distinguish between the different species. As such techniques are not part of routine dermatophyte laboratory diagnostics, it is essential that the request includes relevant travel, contact and sexual, as well as antifungal history. Dermatophyte antifungal susceptibility testing is not routinely done and will only be done when requested and required.
In summary, the UK faces a dual fungal threat: the emergence of drug‑resistant T. indotineae infections increasingly detected locally, and the rise of sexually transmitted T. mentagrophytes TMVII infections. Both pose diagnostic and treatment challenges, underscoring the need for clinical vigilance, advanced laboratory identification, and appropriate antifungal strategies. Timely communication with the Mycology Reference Centre laboratory is essential in getting it right the first time, and thus avoiding delays and allowing further spread of infection.
These outbreaks will, unfortunately, impact the Mycology Reference Centre Laboratory workload and turn-around times for less critical tests such as nail microscopy and culture. We recommend all users consider carefully what guidelines recommend regarding treatment duration and re-testing, and if repeat nail microscopy and culture is needed.
Mycology Reference Centre Manchester contact details:
Telephone: 0161 291 2124
Email: mft.mrcm@nhs.net
Website: www.mrcm.org.uk