Molecular Characterization of a Voriconazole-Resistant, Posaconazole-Susceptible Aspergillus fumigatus Isolate in a Lung Transplant Recipient in the United States.

Molecular characterization of cyp51A from the azole-resistant Aspergillus fumigatus isolate 50593 from a lung transplant patient showed Y121F/T289A changes coupled with a 46-bp tandem repeat (TR46) on the promoter, whereas cyp51A from the pretherapy isolate, A. fumigatus 47381, showed no changes. This is the first reported case of A. fumigatus azole resistance due to Y121F/T289A/TR46 in the United States, suggesting that multiple mutational alterations of cyp51A resulting in high-level azole resistance could occur during prolonged antifungal therapy.