In vitro evaluation of antifungal susceptibility and keratinase, elastase, lipase and DNase activities of different dermatophyte species isolated from clinical specimens in Iran

Summary The aims of this study were to evaluate the enzymatic activity of various dermatophyte species and their antifungal susceptibility profiles. A total of 60 dermatophyte isolates, including Trichophyton mentagrophytes , Trichophyton rubrum , Microsporum canis and Microsporum gypseum , were examined. Fungal isolates were analysed for the production of keratinase, lipase, elastase and deoxyribonuclease ( DN ase). A broth microdilution method was performed on the basis of M38‐A2 Clinical and Laboratory Standards Institute ( CLSI ) guidelines. T. mentagrophytes , M. canis and M. gypseum isolates were capable of producing keratinase, lipase, elastase and DN ase, while T. rubrum isolates were elastase negative. The highest mean diameter of the clear zone around the colonies ( PZ ) was associated with keratinase ( PZ : 4.56 ± 1.29 mm), followed by lipase ( PZ : 1.53 ± 0.90 mm), DN ase ( PZ : 0.65 ± 0.54 mm) and elastase ( PZ : 0.22 ± 0.27 mm) ( P < 0.05). The mean minimum inhibitory concentration 90 ( MIC 90 ) of all strains were as follows: itraconazole ( MIC 90 : 0.28 ± 0.31 μg ml −1 ), ketoconazole ( MIC 90 : 0.48 ± 0.51 μg ml −1 ), griseofulvin ( MIC 90 : 0.86 ± 1.00 μg ml −1 ) and fluconazole ( MIC 90 : 18.57 ± 20.10 μg ml −1 ). Dermatophyte isolates had higher keratinolytic activity than other enzymes. Itraconazole was the most effective antifungal drug and fluconazole had the poorest activity.