Susceptibility of dermatophyte isolates obtained from a large worldwide terbinafine tinea capitis clinical trial.

BACKGROUND: Our group, in collaboration with seven other laboratories, has recently developed a method to determine the susceptibility of dermatophytes.

OBJECTIVES: The objective of this study was to determine the terbinafine susceptibility profile of dermatophyte isolates obtained from patients with tinea capitis enrolled in two large worldwide clinical trials and to investigate whether these susceptibilities differ by geographical location. Methods Susceptibilities were determined according to the Clinical and Laboratory Standards Institute M38-A2 standard.

RESULTS: From a total of 978 baseline dermatophyte isolates, we selected 301 isolates at random. These included: Trichophyton tonsurans (n = 125), Microsporum canis (n = 94), T. violaceum (n = 63) and M. audouinii (n = 19). The terbinafine minimum inhibitory concentration (MIC) range was 0.001-0.25 microg mL(-1), while MIC(50) and MIC(90) ranged between 0.002 and 0.125 microg mL(-1) and 0.03 and 0.25 microg mL(-1), respectively, for all species tested. MIC(50) and MIC(90) varied by individual species; however, there was no difference in terbinafine MIC among the different species isolated from U.S. and non-U.S. sites.

CONCLUSION: Terbinafine demonstrates potent antifungal activity against dermatophyte isolates obtained from patients with tinea capitis worldwide.