Effect of test medium on in vitro susceptibility testing results for Aspergillus fumigatus.

We examined the effect of peptone yeast extract glucose broth (PYG), RPMI 1640 and Antibiotic Medium 3 (M3) on the in vitro susceptibility of clinical isolates (n = 200) of Aspergillus fumigatusto amphotericin B (AMB), itraconazole (ITZ) and voriconazole (VCZ). The MICs (mug/mL) of various antifungal agents (geometric mean plus/minus standard deviation) obtained in PYG, RPMI 1640 and M3, respectively, were as follows; AMB: 1.64 plus/minus 0.92, 0.42 plus/minus 0.21, 0.33 plus/minus 0.16; ITZ: 0.44 plus/minus 0.54, 0.40 plus/minus 0.65, 0.17 plus or minus 0.32; VCZ: 0.70 plus/minus 0.58, 0.29 plus/minus 0.22, 0.36 plus/minus 0.21. Pairwise comparisons of the MICs of AMB, ITZ and VCZ obtained in PYG, RPMI 1640 and M3 showed no significant differences except for AMB in PYG broth compared to those obtained in RPMI 1640 and M3 (p</=0.05). These results suggest that the susceptibility of A. fumigatus to AMB, ITZ and VCZ is similar in growth media currently used for susceptibility testing.