P060 A preliminary in vitro and in vivo evaluation of the effect and action mechanism of 17-AAG combined with azoles against azole-resistant Candida spp.

POSTER SESSION 1, SEPTEMBER 21, 2022, 12:30 PM - 1:30 PM: Invasive candidiasis is the primary reason for the increasing cases of mortality in a medical environment. The resistance spectra of Candida species to antifungal drugs, among which Candida auris is the most prominent, have gradually expanded. OBJECTIVES: Hsp90 plays a protective role in the stress response of fungi and facilitates their virulence. In contrast, Hsp90 inhibitors can improve the resistance of fungi to antifungal drugs by regulating the heat resistance of Hsp90 and thereby destroying the integrity of the fungal cell walls. Therefore, we used Hsp90 inhibitor in combination with different antifungal drugs to explore its antifungal effect and mechanism. METHODS: The drugs tested for the resistance included itraconazole, voriconazole, posaconazole, fluconazole, and 17-AAG. A total of 20 clinical strains of Candida were investigated. The broth microdilution checkerboard technique, as adapted from the CLSI M27-A4 method, was applied in this study. At the same time, the effect of 17-AAG combined with antifungal drugs on the formation of Candida biofilm was observed, and the animal experiment of C. mellonella was carried out in vivo. Moreover, we determined that with the use of rhodamine 6 G to detect drug efflux and that of dihydrorhodamine-123 to detect intracellular reactive oxygen species (ROS). RESULTS: We found that 17-AAG alone exerted limited antifungal activity against all tested strains. The MIC range of 17-AAG was 8 to >32 μg/ml. The synergy among 17-AAG and itraconazole, voriconazole, and posaconazole was observed against 10 (50%), 7 (35%), and 13 (65%) of all isolates, respectively. Moreover, the synergy between 17-AAG and fluconazole was observed against 5 (50%) stains of azole-resistant Candida. However, no antagonism was recorded. In vivo test, the combination group also significantly prolonged the infection event and improved the survival of larvae. Treatment with 17-AAG combined with azole drugs inhibited the efflux pump of fungi and promoted the accumulation of ROS in the fungal cells. CONCLUSION: Our result adequately verifies the influence of 17-AAG on the formation of Candida spp. biofilm. The mechanism of 17-AAG combined with azoles could kill fungi by inhibiting drug efflux and increasing intracellular reactive oxygen species. These results thereby provide a new idea to further explore drugs against drug-resistant Candida spp.