Other emerging severe and resistant dermatophytes of concern

Trichophyton mentagrophytes type VII (TMVII)

• Trichophyton mentagrophytes type VII (TMVII) is a recently emerged dermatophyte that is closely related to T. indotineae (note: T. indotineae was previously called T. mentagrophytes type VIII).^1-3

• TMVII spreads between people and may be transmitted via sexual contact, including in specific patient populations such as men who have sex with men or persons who travelled to Southeast Asia for sex tourism.^1-4

• Data indicate that TMVII infections has been circulating locally in Europe for at least several years.¹

• In 2024, a TMVII case was reported in the United States.⁴ It is unknown whether this infection was acquired in Europe or in the United States.

• TMVII infection can affect multiple body sites, including the pubogenital area, buttocks, extremities, trunk, and face.

• Routine culture may identify either T. mentagrophytes or T. interdigitale. Identification of TMVII requires specialized testing (e.g., ITS genome sequencing) available only at select laboratories.

• Limited data suggest that TMVII responds to oral terbinafine, though longer than typical treatment courses may be required.

• Rarely, clinical failure with terbinafine requiring itraconazole has been reported.

• Currently, antifungal susceptibility data are lacking.

• Bacterial superinfection and scarring have rarely been reported.

• Clinicians are encouraged to monitor patients throughout treatment for disease resolution.

Clinical appearance of Trichophyton mentagrophytes genotype VII infections in men in France, 2022.⁵

A) Swollen lesions above the upper lip and B) on the beard (kerion). C) Papular and nodular inguinal lesions. D) Peri-anal mpox lesions with associated papules and pustules with central umbilication and a large lesion with a central necrotic crust, surrounded by extensive erythemato-squamous circinate lesions caused by TMVII infection. (Source: https://wwwnc.cdc.gov/eid/article/29/7/23-0025-f1)

Patient counseling regarding TMVII

Physicians can council patients on several points:

• Transmission to others may be possible if lesions are present.

• Patients should be screened for other sexually transmitted infections, and partner notification and screening should be discussed.

• The need for prolonged therapy.

• The importance of adherence to the medication and follow-up.

• The need to avoid sharing personal items and clothing.

• Clothing, towels, bedding, and similar shared items should be laundered on high heat.

• The possibility of relapse or recurrence.

• Potential side effects from antifungals.

• Dermatophyte spores can be killed with common disinfectants like diluted chlorine bleach (1/4 cup per gallon water), benzalkonium chloride, or strong detergents.

• If pets are present in the home and also develop skin lesions, the pet should be evaluated by a veterinarian.

Trichophyton rubrum resistant to terbinafine

• T. rubrum, a dermatophyte fungus, is the most common cause of dermatophytosis worldwide.⁶

• Oral terbinafine is considered a first-line treatment for most infections caused by this fungus, but cases of terbinafine-resistant T. rubrum are increasingly being reported worldwide and in the United States, including terbinafine-resistant onychomycosis.^7-9

• Researchers have reported cases of difficult-to-treat terbinafine-resistant T. rubrum worldwide, including in the United States.^7,8,10,11

• Testing for antimicrobial-resistant T. rubrum is available at select U.S. laboratories.

• Patients with terbinafine-resistant Trichophyton rubrum may require treatment with itraconazole or other drugs usually used for treating invasive fungal infections.^7,8

Additional resources