Early Release – Recognition of Antifungal Resistant Dermatophytoses by Infectious Disease Specialists, United States – Volume 30, Issue 9 – September 2024 – Journal of Emerging Infectious Diseases

Dermatophytosis (tinea pedis) is a common superficial fungal infection caused by dermatophyte fungi (1In the past decade, the spread of antifungal-resistant dermatophytosis in South Asia has led to Trichophyton indochinea The fungus causes widespread pruritic patches on the trunk, extremities, groin, and face in immunocompetent people (2–4Unlike typical dermatophyte infections, T. Indochinaceae Fungi are often not cured with over-the-counter topical antifungal medications or oral terbinafine (first-line systemic therapy) (2,3).

T. Indochinaceae The fungus has been detected in at least 11 U.S. states, and refractory dermatophytosis caused by antifungal drug-resistant strains has been reported. T. Rubrum Fungi have also been reported (2,5,6Affected patients experience delayed diagnosis and receive inappropriate treatment, including topical corticosteroids, which may worsen the dermatophytosis (2Cases of antifungal-resistant dermatophytosis in the United States are probably underrecognized because they are not reported to public health authorities in any state (https://www.cdc.gov/fungal/php/case-reporting) and most superficial fungal infections are not identified by diagnostic tests (7Furthermore, given the difficulty in definitively identifying certain species, e.g., fungi, laboratory capacity to identify dermatophyte species and perform antifungal susceptibility testing (AFST) may be limited. T. Indochineaceae, Advanced molecular techniques (e.g., use of internal transcribed spacer region sequence analysis) are required, and most clinical laboratories do not perform mold AFST (2,8).

Cases of antifungal-resistant dermatophytoses may require consultation with an infectious diseases (ID) clinician to manage antifungal drug use and because of the potential impact these infections have on highly immunocompromised patients. Understanding ID clinicians' level of awareness of and access to laboratory testing for antifungal-resistant dermatophytoses can improve strategies to increase disease recognition and facilitate early and appropriate treatment. Therefore, we are collaborating with the Emerging Infectious Diseases Network (EIN) (Learn more), a monitoring network of ID physicians and other ID professionals.

EIN distributed survey links to approximately 3,000 registered members in three waves spaced approximately one week apart in December 2023. The EIN query has been designated as non-human subjects research by the University of Iowa Institutional Review Board.

We received a total of 158 responses (table). The most common practice setting was an academic hospital (47%), followed by community hospitals (16%) and non-academic teaching hospitals (12%). Most respondents were adult ID physicians (80%), followed by pediatric ID physicians (12%), pharmacists (4%), nurse practitioners, physician assistants or physician associates (1%), and other (3%). Overall, 103 (65%) respondents had heard of antifungal resistant dermatophytosis before taking the survey, most of whom (58%) had heard about it through a previous EIN listserv email. Seventeen percent of respondents reported seeing or consulting with a patient with dermatophytosis that was resistant to treatment or where there was concern about resistance within the past year.

Nearly half of respondents (47%) said that if they saw a patient with a potentially resistant dermatophytosis, they would not be able to obtain testing to identify the species (16%) or were unsure whether such testing would be available (31%).tableSimilarly, the majority of respondents (61%) said they could not obtain testing to determine whether their dermatophytes were resistant to antifungal drugs (16%) or were unsure whether such testing was available (45%).

In summary, our survey found that about one-third (35%) of ID clinicians had never heard of antifungal resistant dermatophytosis. Only 53% of respondents said they knew how to obtain a dermatophyte species typing test, and even fewer (39%) said they knew how to obtain a test for dermatophyte resistance (tableThese results are due to the relatively recent recognition of these infections in the United States and the availability of tests to identify them. T. indochineae Testing for resistant dermatophyte species is limited to certain mycology reference centers and public health laboratories in the United States (2,8).

Dermatophyte species identification and AFST are important to guide antifungal treatment decisions for patients with potentially resistant dermatophytosis and to monitor population-level trends in resistance profiles to inform treatment guidelines (8Although there are no national guidelines for the treatment of antifungal-resistant dermatophytosis, the azole antifungal itraconazole has been used effectively in patients with fungal-resistant dermatophytosis. T. indochineae Terbinafine resistance T. Rubrum Fungi (2,9However, clinicians must be aware of the variability in itraconazole pharmacokinetics (e.g., absorption), insurance coverage, drug-drug interactions, and the need for long-term treatment (e.g., >6 weeks), and reports of emergence of itraconazole resistance T. indochineae and T. Rubrum Fungi (2,6,9,10).

One limitation of this survey is the low response rate and its non-representative nature. Furthermore, if clinicians knowledgeable on the topic were more likely to respond, the survey may overestimate clinician awareness of antifungal-resistant dermatophytosis and access to laboratory testing. Despite these limitations, this survey highlights the need to increase awareness of antifungal-resistant dermatophytosis and laboratory capacity to identify dermatophytes and perform susceptibility testing to address this emerging public health concern.

Healthcare professionals can find information about recognizing, diagnosing, treating, and reporting emerging dermatophyte infections online athttps://www.aad.org/member/clinical-quality/clinical-care/emerging-diseases/dermatophytes), information on laboratories that can perform the tests (https://www.aad.org/member/clinical-quality/clinical-care/emerging-diseases/dermatophytes/recognizing-trichophyton-indotineae#testingThese websites were developed in collaboration with the U.S. Centers for Disease Control and Prevention and the American Academy of Dermatology Emerging Diseases Task Force.

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