The Effect of Incubation Temperature on Susceptibility Test of Dermatophytes to Oral Antifungal Agents

Kwak, Tae Hun; Choi, Jong Soo; Kim, Ki Hong

Abstract

BACKGROUND: thermotherapy has been shown to be effective in the treatment of some fungal infections. Dermatophyte are well grown at 25degrees C rather than 37degrees C or high temperature.
OBJECTIVE
An vitro test was done to assess the complemental effect and optimal conditions of local heating on the susceptability of t. rubrum to systemic antifungal agents.
METHODS
Microdilution susceptability test to ketoconazole and itraconazole was done using 96 well microplate. Eight strains of T. rubrum were isolated from patients withtinea pedis and were cultured at 25degrees C, 37degrees C and 42degrees C for 1, 8 or 24 hours per day. MIC were checked at 4th, 7th, 9th day after inoculution.
RESULTS
The growth without antifungal agents at 37degrees C and 42degrees C were decreased by 805 and 50% of the growth at 25degrees C respectively. Seven day after inoculation was the proper time to check the MIC. MIC50 of ketoconazole was the lowest at 42degrees C for 24hours per day in value of 0.006microgram/ml, and 0.09microgram/ml at 37degrees C for 24hours per day, 0.37microgram/mlat 42degrees C, for 8hours per day and 37degrees C for 8hours per day. MIC at 42degrees C for 1 hours er day, 37degrees C for 1 hyours and 25degrees C for 24hours per ady MIC were the same in value of 0.05microgram/ml. MIC50 of itraconazole was the lowest at 42degrees C for 24hours per day in value of 0.006microgram/ml, 0.01microgram/ml at 37degrees C for 24hours per day, 0.02microgram/ml at 37degrees C for 8hours per day. MIC at 42degrees C for 8hours per day, 42degrees C for 1hours per day, 37degrees C for 24hours per day MIC were the same in value of 0.05microgram/ml.
CONCLUSION
Incubation at 37degrees C for 24 hours per day or 42degrees C for 24 hours per day increased the susceptability of T. rubrum to ketoconazole and itraconazole.