Clinicomycological study on identification and antifungal susceptibility testing of dermatophytes at a tertiary care hospital in Tamil Nadu

• Author Details:   
• Sumayya Fathima H ^*
• Sumetha Suga D
• Kalpana Devi V
• Ananthi B
• Subha S

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Background and Aim: The most prevalent cutaneous fungal infection is dermatophytosis, which is caused by a class of keratinophilic filamentous fungus known as dermatophytes. There is dramatic rise in recalcitrant and extensive dermatophytosis associated with antifungal resistance. So early and accurate diagnosis is essential for timely administration of anti-fungal agents in dermatophytosis. The present study aimed to isolate and identify dermatophytes and to study the antifungal susceptibility pattern.
Materials and Methods: Prospective Cross sectional study conducted for 18 months (Nov 2022 - April 2024). 250 clinical isolates from patients with clinical diagnosis of Superficial Mycoses attending OPD Dermatology were collected, initial KOH mount was done. The identification was carried out using both traditional methods and Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF MS).  The isolates were tested for their antifungal susceptibility using the micro broth dilution technique according to the Clinical and Laboratory Standards Institute (CLSI) M38 - A2(2008).
Results: Among 250 clinical specimens, all 103 dermatophyte isolated in conventional culture methods, Genus was Trichophyton, of which Trichophyton mentagrophytes was 88.3% as the predominant isolate, followed by Trichophyton rubrum with 11.7% isolates. In MALDITOF-MS identification, out of 50 isolates, 66% correlated at Genus level and 62% correlated at species level. Out of 45 Trichophyton mentagrophyte isolates tested for Antifungal susceptibility testing (AFST), 97.80% showed resistance to Fluconazole and 31.10% to Itraconazole. 5 isolates of Trichophyton rubrum showed resistance to 80% of Fluconazole and 40% of Itraconazole.
Conclusion: To improve patient outcomes in the future, it is important to diagnose dermatophytosis early and accurately, utilize newer antifungal medicines with caution, and practice antifungal stewardship.

Keywords: Tinea, Cutaneous mycoses, Dermatophytes, Trichophyton, Antifungal susceptibility, Dermatophytosis