Emerging antimicrobial-resistant ringworm infections


Ringworm (also known as “tinea” and “dermatophytosis”) is a common infection of the skin, hair, or nails. Most cases of ringworm do not lead to severe illness. However, ringworm can cause stigma, intense physical discomfort, and decreased quality of life, particularly among people with weakened immune systems. Ringworm generally requires treatment with antifungal drugs to relieve symptoms and prevent spread to others.

Over the past decade, healthcare providers have reported increasing cases of antimicrobial-resistant ringworm.1 Antimicrobial resistance happens when germs like bacteria and fungi develop the ability to defeat the drugs designed to kill them. That means the germs are not killed and continue to grow.

The true number of antimicrobial-resistant ringworm cases is difficult to estimate because antifungal susceptibility testing is not widely available and reporting of antimicrobial-resistant ringworm cases is not required in the United States.

Antimicrobial-resistant Trichophyton indotineae

Trichophyton indotineae, sometimes referred to as Trichophyton mentagrophytes type VIII, is a dermatophyte mold. It often has genetic mutations that make it resistant to antifungal drugs. In India, cases of antimicrobial-resistant ringworm caused by T. indotineae have reached epidemic proportions. Ringworm cases caused by T. indotineae are often severe (covering large regions of the body) and difficult to treat. Although cases seem to be rare outside of India, researchers have reported cases in Europe and North America.2-4

Trichophyton rubrum resistant to terbinafine

Trichophyton rubrum, a dermatophyte mold, is the most common cause of fungal nail infections (onychomycosis) and ringworm worldwide. Oral terbinafine is considered the first-line treatment for most infections caused by this organism, but cases of terbinafine-resistant T. rubrum are increasingly being reported.5 Researchers have reported cases of difficult-to-treat terbinafine-resistant T. rubrum worldwide, including in the United States.6

What factors might be contributing to the emergence and spread of antimicrobial-resistant dermatophytes?

  • Overuse of over-the-counter topical antifungal creams
  • Inappropriate use of topical steroid creams
  • Inappropriate prescription of antifungal drugs
  • Inadequate adherence to prescribed courses of antifungal medication
  • Global travel and migration

What CDC is doing

CDC is working closely with partners from state and local health departments, academia, international organizations, and other federal agencies to address issues surrounding antimicrobial resistance.

CDC is leading and supporting several projects through its Antimicrobial Resistance Solutions Initiative, including:

  • Performing outreach to healthcare providers and professional societies to raise awareness of antimicrobial-resistant ringworm and improve adherence to guidelines for ringworm diagnosis and treatment
  • Supporting studies to better understand the burden of antimicrobial-resistant ringworm in the United States, with an emphasis on preventing further spread
  • Increasing capacity for antifungal susceptibility testing
  1. Hay RJ. The Spread of Resistant Tinea and the Ingredients of a Perfect Storm. Dermatology. 2022;238(1):80-81.
  2. Saunte D, Pereiro-Ferreirós M, Rodríguez-Cerdeira C, Sergeev A, Arabatzis M, Prohić A, et al. Emerging antifungal treatment failure of dermatophytosis in Europe: take care or it may become endemic. J Eur Acad Dermatol Venereol. 2021 March;35:1582-1586.
  3. Jabet A, Brun S, Normand A, Imbert S, Akhoundi M, Dannaoui E, et al. Extensive Dermatophytosis Caused by Terbinafine-Resistant Trichophyton indotineae. Emerg Infect Dis. 2022;28(1):229-233.
  4. Edriss MT, Parker JL, Pritchett, EN. Response to Gu et al’s “Treatment-resistant dermatophytosis: A representative case highlighting an emerging public health threat”. 2022 Jan.
  5. Hay RJ. 82- Superficial Mycoses. Hunter’s Trop Medi and Emerg Infect Dis. 2020 May; 10:648-652.
  6. Gu B, Hatch M, Ghannoum M, Elewski BE. Treatment-resistant dermatophytosis: A representative case highlighting an emerging public health threat. JAAD. 2020 Nov; 6(11):1153-1155.