Disk diffusion susceptibility testing of dermatophytes with imidazoles

Area of Science:

• Mycology
• Medical Mycology
• Antimicrobial Susceptibility Testing

Background:

• Dermatophytes are fungi causing superficial infections.
• Antifungal resistance necessitates evaluating drug efficacy.
• Imidazoles and griseofulvin are common antifungal agents.

Purpose of the Study:

• To assess the in vitro susceptibility of dermatophyte isolates to econazole, ketoconazole, miconazole, and griseofulvin.
• To compare the effectiveness of agar dilution and disk diffusion methods for susceptibility testing.
• To evaluate the correlation between minimum inhibitory concentrations (MICs) and zones of inhibition.

Main Methods:

• In vitro susceptibility testing of 43 dermatophyte isolates.
• Agar dilution and disk diffusion methods were employed.
• Antifungal agents tested included econazole, ketoconazole, miconazole, and griseofulvin.

Main Results:

• Econazole was the most potent, inhibiting all isolates at 0.1 µg/mL.
• MIC50 and MIC90 values varied among the tested antifungals.
• A strong negative correlation was observed between MIC values and zones of inhibition for all drugs (p < 0.001).

Conclusions:

• Econazole exhibits significant in vitro activity against dermatophytes.
• Both agar dilution and disk diffusion are reliable methods for susceptibility testing.
• Regression analysis confirms a good correlation between MICs and zone sizes, supporting disk diffusion as a predictive tool.