Are Epidemiologic Cut-off Values Predictors of the in Vivo Efficacy of Azoles in Experimental Aspergillosis?

We tried to correlate the in vitro activity and the in vivo efficacy of voriconazole (VRC) and posaconazole (POS) against Aspergillus flavus and Aspergillus niger. The in vitro susceptibility of a large set of isolates was determined by broth microdilution and disk diffusion methods, while the in vivo efficacy was assessed in a murine model of disseminated infection. For A. flavus, VRC showed efficacy even for strains with MICs above the epidemiologic cutoff value (ECV) (1 μg/mL). For A. niger, VRC was ineffective against those strains for which the MIC was 1 dilution below the corresponding ECV (2 μg/mL). POS showed efficacy against all the strains of both species included in the study, although isolates with MICs > ECV were not tested.