Species Distribution, Species Characterization, and Antifungal Susceptibility of Clinical Dermatophyte Isolates

Abstract

The global epidemiology of dermatophytosis is rapidly changing due to the emergence of antifungal-resistant dermatophytes. Epidemiological surveillance has highlighted the need for accurate species-level identification and interaction between clinical microbiology laboratories and clinicians for treatment decisions and early detection of resistant strains. This study evaluated the epidemiological characteristics, anatomical distribution, and antifungal susceptibility profiles of dermatophyte infections encountered in routine clinical practice, and also aimed to investigate the complementary roles of MALDI-TOF MS and traditional mycological methods in routine clinical practice. In the Medical Microbiology and Mycology Laboratory of Istanbul University-Cerrahpaşa Faculty of Medicine Hospital, 126 dermatophyte isolates obtained from clinical samples of superficial mycoses between 2017-2018 were analyzed using conventional and MALDI-TOF methods. Patients with recurrent infections underwent antifungal susceptibility testing. Tinea corporis was the predominant clinical presentation, accounting for 41.3% of cases, followed by tinea unguium (30.2%) and tinea pedis (11.9%). MALDI-TOF MS provided reliable species-level identification for 71 (56.3%) of 126 isolates, while the remaining 55 isolates (43.7%) were characterized using conventional mycological methods. Conventional methods identified 39 isolates as Trichophyton mentagrophytes, four as Microsporum canis, three as Trichophyton rubrum, two as Trichophyton tonsurans, one as Microsporum audouinii, and one as Trichophyton violaceum, while five isolates were reported as other dermatophyte species. Overall, T. rubrum was the most frequently isolated species (48.4%), followed by T. mentagrophytes (31.7%). Antifungal susceptibility testing showed variable susceptibility profiles among isolates from persistent or recurrent cases. MALDI-TOF MS and conventional phenotypic methods should be considered complementary approaches for dermatophyte identification. The significant contribution of conventional methods to species identification underscores their continued importance in routine clinical mycology laboratories, particularly in situations where commercial MALDI-TOF MS databases are incomplete. Integrating identification and susceptibility testing improves the management and monitoring of resistant dermatophytosis.