AN EVALUATION OF 7 METHODS OF TESTING IN-VITRO SUSCEPTIBILITY OF CLINICAL YEAST ISOLATES TO FLUCONAZOLE

Four commercially available in vitro test systems (Candifast(R), E-tes t, Mycototal(R) and spiral-gradient end point method), agar diffusion with 25-mu g fluconazole paper test discs and 15-mu g test tablets and agar dilution were compared with the microbroth dilution method for f luconazole susceptibility testing of 145 clinical isolates. In additio n, the culture media provided or recommended by the manufacturers of t he test systems were compared with high-resolution (HR) antifungal tes t medium. With all currently available culture media, growth problems (inhibition or delayed growth of the clinical isolates) occurred with solid or semisolid media. With minor improvements, HR medium demonstra ted the most reproducible and comparable results (supplementation with asparagine and deletion of sodium hydrogen carbonate). The best corre lation with microdilution was obtained by the agar dilution method(> 9 5% concordance) followed by the spiral-gradient end point method (85%) , Candifast(R) (83%), Mycototal(R) (81%) and the E-test (78%). Regress ion analysis demonstrated good correlation between agar diffusion and micro-/agar dilution (r>0.9).