TITLE:
Antifungal Susceptibility Testing of Dermatophytes by ABDD and E-Test, a Comparative Study
AUTHORS:
Matheus Heita Namidi, Tejashree Ananthnaraja, Badveti Satyasai
KEYWORDS:
Dermatophytosis, Dermatophyte Test Medium, Disc Diffusion and E-Strips, Antifungal Agents
JOURNAL NAME:
Open Journal of Medical Microbiology,
Vol.11 No.3,
August
6,
2021
ABSTRACT: Aim: The objective of this study was to isolate, identify, and explore the in-vitro antifungal susceptibility pattern of dermatophytes isolated from clinically suspected cases of dermatophytosis (tinea
infections) attending the Dermatology Department at J.S.S Hospital. Methods: This study was conducted at JSS Medical College and Hospital from December
2016 to December 2017. Clinical samples (e.g., skin scrapings and hair stumps)
were collected under aseptic precautions.
The identification of dermatophytes was performed through microscopic examination using 10%, 20% & 40% potassium hydroxide
(KOH) and culture on Sabouraud dextrose agar (SDA), SDAac, PDA and Dermatophyte
test medium (DTM). All dermatophytes isolates were subjected to antifungal
susceptibility testing using the agar-based disk diffusion (ABDD) and
E-test method against Terbinafine, Itraconazole, Fluconazole, and Griseofulvin.
Data were analyzed by using Chi square test. Results: A 100 samples were
studied, 46% tinea corporis, 2%tinea cruris, 9% tinea pedis, 5% tinea faciei. The dermatophytes isolated were Trichophyton rubrum 11 (35%), Trichophyton mentagrophyte 8 (25%), Trichophyton tonsurans 5 (16%), Microsporum
gypseum 3 (10%), Trichophyton verrucosum 2 (6%), Trichophyton violaceum 1 (3%) and Microsporum audouinii 1 (3%). Out of 31
dermatophytes 17 were sensitive to all four antifungal agents within the range
of FLC (2 - 6 mcg/ml), ITR (0.125 - 2), TER
(0.125 - 2), and GRI (0.125 - 2), 5 isolates were resistant in which 2 were
resistant to FLC (64.256 mcg/ml), 2 isolates were resistant to TER 2 (32.38
mcg/ml), 1 isolate was resistant to both GRI and TER (16.32 mcg/ml) and 9
isolates were within the intermediate range. Conclusion: Every patient
with a tinea infection should be properly studied for a mycological examination
and should be treated accordingly. Dermatophyte test medium is more useful as
an identification medium in the isolation of dermatophytes. The ABDD method
appears to be a simple, cost-effective, and promising method for the evaluation
of antifungal susceptibility of dermatophytes. E-test method is the most sensitive
method due to the fact that quantitative MICs can be obtained directly from the
E-strip. However, the E-test method is expensive and difficult in defining the
precise borders of the inhibition zones in dermatophytes.