Drug-resistant Trichophyton fungus represents emerging threat in US


Photo courtesy of CDC/ Dr. Lucille K. Georg

In a new JAMA Dermatology report, researchers describe 11 Trichophyton indotinea infections in New York City from May 2022 to May 2023. The fungus represents a new emerging public health threat that causes extensive tinea infections often unresponsive to terbinafine, a first-line oral antifungal.

T indotineae causes an extensive rash composed of plaques, found on the trunk, extremities, and groin. In recent years, several outbreaks in South Asia have been documented, with the rash unresponsive to standard antifungal treatments, both oral and topical. 

Cases have been found all over the world, however, including in the United States. The country confirmed the first two cases of the infection in May 2023, but retrospective reviews suggest the earliest confirmed US isolate was from 2017. 

"Despite increased US spread, cases are likely underrecognized due to lack of awareness," the authors wrote. 

Despite increased US spread, cases are likely underrecognized due to lack of awareness.

9 of 11 patients had traveled to Bangladesh 

In the study, the authors describe infections in 6 men and 5 women with a median age of 39. Two were pregnant, and 1 patient had undiagnosed lymphoma. In the 2 years prior to the development of rash and itching, 9 of the 11 reported travel to Bangladesh.

Three case-patients likely contracted the fungus via household transmission, and one had no travel history or known contact with an infected person. 

All patients experienced significant delays in diagnosis, ranging from 3 to 42 months, with a median diagnosis time of 10 months. 

Eight patients received steroid prescriptions before tinea diagnosis, and all patients received at least one topical antifungal medication, none of which was effective as monotherapy.

"Patients experienced extensive, prolonged pruritic lesions that generally failed monotherapy with topical antifungals and showed inadequate response to typical doses and durations of oral antifungal medications, including prolonged terbinafine therapy at standard doses, consistent with findings from international reports," the authors said. 

Itraconazole therapy for suspected cases 

The dermatologists were often unaware of T indotineae diagnosis at the time of treatment, leading to ineffective and suboptimal antifungal treatments. Only itraconazole therapy did not fail, but prolonged treatment durations were required to achieve a cure, the authors said. 

In an editorial on the case series, Toan S. Bui and Kenneth A. Katz, MD, MSCE, said dermatologists should be suspicious of  T indotineae when lesions do not respond to typical first-line topical antifungals, especially in patients with recent travel history to South Asia.

"Clinicians caring for patients with confirmed dermatophytosis resistant to typical first-line treatments should consider empirical treatment with itraconazole while awaiting test results, bearing in mind its important interactions with other medications and the possibility of itraconazole resistance, which has been reported," they wrote.

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