CDC Reports First Cases of Highly Contagious, Drug-Resistant Ringworm in the United States
The Centers for Disease Control and Prevention (CDC) has reported two cases of a highly contagious, drug-resistant form of ringworm in New York City, marking the first such cases in the United States. Ringworm is a common, superficial infection of the skin, hair or nails caused by fungi that spreads through skin-to-skin contact. Typically, it is treated with antifungal medications, but over the past decade, a treatment-resistant strain has emerged in South Asia, referred to as Tinea indotineae infections. The CDC has referred to the increase in these cases as “an epidemic,” which has now spread to countries in Europe as well.
The two reported cases in New York City highlight the potential local transmission of T. indotineae in the United States, as the first patient had no recent international travel history. When patients with widespread tinea do not respond to first-line topical antifungal agents or oral terbinafine, health care providers should take into account the possibility of T. indotineae infection. Culture-based identification techniques used by most clinical laboratories typically misidentify T. indotineae as T. mentographytes or T. interdigitale, requiring correct identification through genomic sequencing. Health care providers who suspect T. indotineae infection should contact their state or local public health department for assistance with testing, available at certain public health laboratories and specialized academic and commercial laboratories.
Both patients were successfully treated with oral antifungal medications, but doctors are looking into other treatment options as ringworm infections can return. Documentation exists of the efficacy of oral itraconazole, a triazole antifungal, in successful treatment. However, providers should be aware of challenges with itraconazole absorption, which can lead to variable serum drug concentrations; itraconazole’s interactions with other drugs; the need for up to 12 weeks of therapy; and the documented emergence of triazole resistance. To prevent the misuse and overuse of antifungal drugs and corticosteroids, it is crucial to implement antimicrobial stewardship measures.
According to case reports published in MMWR, health officials have discovered the initial instances of severe tinea, also known as ringworm, caused by Trichophyton indotineae in the United States. In their writing, the authors emphasized a few crucial points. Firstly, the absence of travel history in the initial patient suggests the possibility of T. indotineae being locally transmitted in the United States. Secondly, the utilization of culture-based identification techniques by most clinical laboratories could lead to misidentification of T. indotineae, as the skin cultures from each patient were previously recognized as T. mentagrophytes. Lastly, documented evidence shows that oral itraconazole treatment can be effective.
The CDC reports that health care providers should consider T. indotineae infection in patients with widespread tinea, particularly when eruptions do not improve with first-line topical antifungal agents or oral terbinafine. Culture-based identification techniques used by most clinical laboratories typically misidentify T. indotineae as T. mentographytes or T. interdigitale, requiring correct identification through genomic sequencing. Successful treatment using oral itraconazole, a triazole antifungal, has been documented, but providers should be aware of challenges with itraconazole absorption, its interactions with other drugs, the need for up to 12 weeks of therapy, and the documented emergence of triazole resistance.
In addition to treatment, health care providers can educate patients about strategies to prevent the spread of the dermatophytes that cause tinea. Public health surveillance efforts and increased testing could help detect and monitor the spread of T. indotineae. Antimicrobial stewardship efforts are also essential to minimize the misuse and overuse of prescribed and over-the-counter antifungal drugs and corticosteroids.
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