Synergistic Effects of Tetrandrine with Posaconazole Against Aspergillus fumigatus

In our earlier in vitro and in vivo studies, synergistic effects were observed when itraconazole or voriconazole were combined with tetrandrine (TET) against Aspergillus fumigatus, and the synergistic mechanism was related to inhibition of the drug efflux pump. Posaconazole (PCZ) is a broad-spectrum triazole antifungal agent used for the treatment of diverse fungal infections, including aspergillosis and candidiasis. Herein, the antifungal effects of TET are further investigated in vitro and in vivo alone or combined with PCZ against 20 clinical isolates of A. fumigatus. We found that the minimal inhibitory concentrations (MICs) of PCZ were decreased one- to twofold and three- to fivefold across a series of concentration gradients in vitro in presence of TET. Time-killing curves revealed that the synergy was dependent on TET and PCZ concentrations as well as incubation time. The combination could further downregulate the expression of MDR2, MDR3, MDR4, and ATRF in PCZ-resistant strain, however, it has subtle effects on TET-synergized mechanism. In addition, TET in combination with PCZ significantly prolonged mice survival time and reduced kidney and brain tissue burdens in vivo. Our data in vitro and in vivo demonstrate that TET is an effective synergist with azoles against A. fumigates.