Differences in interactions between azole drugs related to modifications in the 14-alpha sterol demethylase gene (cyp51A) of Aspergillus fumigatus.

The combined activity of different azole drugs was investigated. Thirty-one Aspergillus fumigatus strains were tested, including two cyp51A(-) and one cyp51B(-) gene-knockout strain and azole-susceptible and -resistant strains with different resistance mechanisms. The combination of itraconazole and voriconazole was synergistic for all strains except for those with gene knockouts.