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Friday 01 July 2005

[In vitro activity of ketoconazole, itraconazole and terbinafine against Malassezia strains isolated from neonates]

By: Sancak B, Ayhan M, Karaduman A, Arikan S.

Mikrobiyol Bul 2005 Jul;39(3):301-8

Malassezia, a yeast-like fungus found in normal skin flora is known to be associated with various skin diseases and systemic infections. There is yet no standardized in vitro susceptibility testing method and minimum inhibitory concentration (MIC) breakpoints for Malassezia species. In this study, we investigated the in vitro activity of ketoconazole, itraconazole and terbinafine against 30 Malassezia strains (22 Malassezia furfur/dermatis, 8 M. japonica) isolated from cheek and/or scalp swabs and/or cephalic pustules of 21 neonates. The isolates were identified to species level on the basis of growth on Sabouraud dextrose agar, assimilation of Tween compounds and catalase reaction. The antifungal susceptibility tests were performed by agar dilution method using modified Dixon agar (MDA) and the agar dilution plates were incubated at 32 degrees C. For the isolates which exhibited sufficient growth, MICs were read at 48 hours, for the remaining slow-growing isolates, MIC readings were done on 7th day. For all drugs tested, the lowest concentration that provided complete inhibition of growth visually was interpreted as the MIC (microg/ml) value. Itraconazole was the most active drug in vitro against Malassezia species, followed by ketoconazole and terbinafine in rank order. In vitro activity of terbinafine was poor for half of the Malassezia strains tested. Variations in activity against individual Malassezia strains were detected for ketoconazole and terbinafine, while in vitro activity of itraconazole was similar for all strains tested. In order to validate the clinical significance of these results, further in vitro and in vivo correlation studies are needed.

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