Perfil de susceptibilidade a antifúngicos de dermatófitos isolados de pacientes atendidos no Hospital Universitário Onofre Lopes (HUOL) em Natal/RN

Abstract

Dermatophytosis is one of the most prevalent fungal infections in humans, caused by keratinophilic fungi of the genera Trichophyton, Microsporum, and Epidermophyton, which affect keratin-rich tissues such as skin, nails, and scalp. In recent decades, a concerning increase in dermatophyte resistance to first-line antifungals, such as terbinafine, has been observed, highlighting the need to monitor the susceptibility of these strains. This study aimed to test the susceptibility of clinical dermatophyte isolates from the dermatology outpatient clinic of Hospital Universitário Onofre Lopes (HUOL). The samples were subjected to direct examination with 20% potassium hydroxide (KOH), isolation on Sabouraud Dextrose Agar (SDA) with chloramphenicol and Mycosel agar, phenotypic identification by microculture on Potato Dextrose Agar (PDA), and identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF). Subsequently, broth microdilution testing was performed in 96-well plates, according to the Clinical and Laboratory Standards Institute (CLSI) protocol, to determine the Minimum Inhibitory Concentration (MIC) against ten antifungals: ketoconazole, sertaconazole, clotrimazole, voriconazole, itraconazole, fluconazole, griseofulvin, amorolfine, terbinafine, and amphotericin B. The results show that among the 10 isolated samples, phenotypic identification revealed 50% T. rubrum, 30% T. mentagrophytes, and 20% T. tonsurans. After confirmation by MALDI-TOF, five results were corrected, showing a prevalence of T. rubrum (80%), T. mentagrophytes (20%), and absence of T. tonsurans. For the susceptibility tests, terbinafine showed the best results, with 90% of isolates sensitive to the lowest concentration tested (0.03 μg/mL), except for VIGD-23 (4 μg/mL). Fluconazole was the least effective, with 90% of samples presenting MICs ≥ 64 μg/mL. Strain VIGD09 (T. rubrum) showed multiple resistance, with MICs above the highest concentrations tested for five antifungals, associated with prior antifungal use and a chronic infection. In contrast, VIGD11 stood out for its higher sensitivity, with MICs between minimum and low values for all drugs, showing a classic profile of a new infection (< 1 month), in a patient with no history of prior antifungal use. The data reinforce the importance of laboratory surveillance of dermatophyte susceptibility, especially in clinical contexts of difficult therapeutic management and in a scenario of increasing resistance to first-line antifungals, such as terbinafine.