GROWTH-MEDIUM EFFECT ON THE ANTIFUNGAL ACTIVITY OF LY-303366

The impact of growth medium selection on antifungal susceptibility tes ting has been well documented. Previously we described the antifungal characteristics of LY 303366 via time-kill curve methods using RPMI 16 40 buffered with 0.165 M morpholinepropane-sulfonic acid as growth med ium. The purpose of the current study was to compare the previously re ported kill curve results with results obtained using antibiotic mediu m number three (AM #3) as growth medium. Antifungal activity was asses sed via susceptibility testing and time-kill studies in both media. Tw o isolates each of Candida albicans, C. glabrata, and C. tropicalis we re studied. MICs for fire six isolates were found to be 10 to 100 time s lower in AM #3. Time-kill studies were conducted with multiples of t he MIC ranging from 0.125 x MIC to 16 x MIC. LY 303366 exhibited fungi cidal (greater than or equal to 3 log(10) reduction in CFU) activity a gainst all isolates in AM #3; however, fungicidal activity was noted o nly for three of the six isolates when tested in RPMI. Furthermore, th e rate of fungicidal activity was more rapid when AM #3 was utilized. Not only were the rate and extent of activity influenced by choice of media, but the relationships between LY 303366 concentrations and acti vity were also found to be media dependent. The findings from this stu dy serve to highlight further the importance of media selection for in vitro evaluation of antifungal activity. In vivo studies need to be c onducted with LY 303366 to determine which media provides the best cor relation between in vitro and in vivo findings. (C) 1997 Elsevier Scie nce Inc.