Determination of minimum inhibitory concentrations of itraconazole, terbinafine and ketoconazole against dermatophyte species by broth microdilution method.
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Date
2015-10
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Abstract
Purpose: Various antifungal agents both topical and systemic have been introduced into clinical practice for effectively
treating dermatophytic conditions. Dermatophytosis is the infection of keratinised tissues caused by fungal species
of genera Trichophyton, Epidermophyton and Microsporum, commonly known as dermatophytes affecting 20–25%
of the world’s population. The present study aims at determining the susceptibility patterns of dermatophyte species
recovered from superficial mycoses of human patients in Himachal Pradesh to antifungal agents; itraconazole,
terbinafine and ketoconazole. The study also aims at determining the minimum inhibitory concentrations (MICs) of
these agents following the recommended protocol of Clinical and Laboratory Standards Institute (CLSI) (M38-A2).
Methodology: A total of 53 isolates of dermatophytes (T. mentagrophyte-34 in no., T. rubrum-18 and M. gypseum-1)
recovered from the superficial mycoses were examined. Broth microdilution method M38-A2 approved protocol
of CLSI (2008) for filamentous fungi was followed for determining the susceptibility of dermatophyte species.
Results: T. mentagrophyte isolates were found more susceptible to both itraconazole and ketoconazole as compared to
terbinafine (MIC50: 0.125 μg/ml for itraconazole, 0.0625 μg/ml for ketoconazole and 0.5 μg/ml for terbinafine). Three
isolates of T. mentagrophytes (VBS-5, VBSo-3 and VBSo-73) and one isolate of T. rubrum (VBPo-9) had higher MIC
values of itraconazole (1 μg/ml). Similarly, the higher MIC values of ketoconazole were observed in case of only three
isolates of T. mentagrophyte (VBSo-30 = 2 μg/ml; VBSo-44, VBM-2 = 1 μg/ml). The comparative analysis of the three
antifungal drugs based on t-test revealed that ‘itraconazole and terbinafine’ and ‘terbinafine and ketoconazole’ were
found independent based on the P < 0.005 in case of T. mentagrophyte isolates. In case of T. rubrum, the similarity
existed between MIC values of ‘itraconazole and ketoconazole’ and ‘terbinafine and ketoconazole’. Conclusion: The
MIC values observed in the present study based on standard protocol M38-A2 of CLSI 2008 might serve as reference
for further studies covering large number of isolates from different geographic regions of the state. Such studies might
reflect on the acquisition of drug resistance among isolates of dermatophyte species based on MIC values.
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Keywords
Dermatophytes, itraconazole, ketoconazole, minimum inhibitory concentration, terbinafine
Citation
Bhatia V K, Sharma P C. Determination of minimum inhibitory concentrations of itraconazole, terbinafine and ketoconazole against dermatophyte species by broth microdilution method. Indian Journal of Medical Microbiology. 2015 Oct-Dec; 33(4): 533-537.