Antifungal Susceptibility Testing of Five Antifungal Agents against Clinically Isolated Dermatophytes Species from a Tertiary Care Hospital in Northern India

Introduction: Dermatophytosis form approximately 15-75% of all the mycological infections. Dermatophytes are closely related keratinolytic fungi with ability to degrade keratin and invade the skin, hair and nails causing dermatophytosis.

Aim: To evaluate the Minimum Inhibitory Concentration (MIC) of antifungal drug against the isolated dermatophytes by broth microdilution method.

Materials and Methods: The present cross-sectional study was conducted in the Department of Microbiology, Muzaffarnagar Medical College, Muzaffarnagar, Uttar Pradesh, India. The duration of the study was August 2018-August 2020 and included 245 patients of which 165 samples were culture positive. A 10-20% Potassium Hydroxide (KOH) mount was prepared from the skin scrapings, nail clippings, and hair bits to look for fungal elements. The specimens were also inoculated on Mycosel media and Sabouraud Dextrose Agar (SDA) with chloramphenicol. The dermatophytes were identified on the basis of colony characteristics, Lacto Phenol Cotton Blue (LPCB) mount, nutritional requirement, temperature tolerance, urease production, and in-vitro hair perforation test. Antifungal susceptibility testing was done for all fungal isolates and performed by broth microdilution method. The descriptive statistics were reported as means with their Standard Deviation (SD). Data were statistically evaluated with International Business Machines (IBM) Statistical Package for the Social Sciences (SPSS) Statistics for Mac, Version 25.0., IBM Corp., Chicago IL.

Results: In this study, the MIC range for all the 165 isolates for dermatophytes tested for antifungal susceptibility showed that itraconazole, terbinafine and voriconazole showed the lowest MIC range of 0.0019-0.5 μg/mL followed by griseofulvin and fluconazole at MIC range of 0.125-32 μg/mL. The MIC50 of itraconazole and terbinafine was seen lowest at 0.0313 μg/mL followed by voriconazole at 0.0625 μg/mL, griseofulvin at 0.25 μg/mL for all isolated dermatophytes. Highest MIC50 with 4 μg/mL was found for fluconazole against T. mentagrophytes and T. violaceum. MIC90 of terbinafine, itraconazole and voriconazole was seen lowest at 0.25 μg/mL followed by griseofulvin at 1 μg/mL for all isolated dermatophytes. Highest MIC90 of fluconazole was recorded at 16 μg/mL for all isolated dermatophytes.

Conclusion: Highest MIC50 with 8 μg/mL was found for fluconazole against all isolated dermatophytes. MIC90 of terbinafine, itraconazole and voriconazole was seen lowest at 0.25 μg/mL followed by griseofulvin at 1 μg/mL for all isolated dermatophytes. Highest MIC90 of fluconazole was recorded at 16 μg/mL for all isolated dermatophytes.