To investigate the effect of CDR1/CDR2 or MDR1 genes overexpression on oxidative stress in Candida albicans,we evaluated the effect of H2O2 on cell viability in C.albicans overexpressing genes CDR1 /CDR2 or MDR1 and their parent strains.After establishing an oxidative stress model with H2O2,we detected reactive oxygen species (ROS),mitochondrial membrane potential (Δψm) and the expression of oxidative stress response-related genes (CAP1 and GRP2) and ROS clearance related-genes (SOD2 and SOD5).The results showed that C.albicans growth were inhibited by 100％ after the treatment of 5 mmol/L H2O2.HeO2 caused more ROS accumulation and Δψm reduction in parent strains than in CDR1/CDR2 or MDR1 genes overexpressed strains (P＜0.05).Compared to parent strains,the up-regulated expression of CAP1 and GRP2 were relatively less in CDR1/CDR2 or MDR1 genes overexpressed strains,moreover,the down-regulated expression of SOD2 and SOD5 were also relatively less in CDR1/CDR2 or MDR1 genes overexpressed strains (P＜0.05).In conclusion,the overexpression of CDR1/CDR2 and MDR1 genes could reduce the oxidative stress response and enhance the adaptability of C.albicans to oxidative stress.

Objective To evaluate the in vitro synergistic effect of tetrandrine on ketoconazole against Candida parapsilosis complex.Methods According to the Clinical and Laboratory Standards Institute (CLSI) M27-A3 guidelines,the microdilution checkerboard method was used to evaluate in vitro antifungal activities of ketoconazole alone and in combination with tetrandrine against 21 clinical isolates of Candida parapsilosis complex based on the fractional inhibitory concentration index (FICI).Antifungal effects of the above drugs at different time points were evaluated by the XTT assay,and then time-killing curves were drawn and assessed to investigate the in vitro dynamic antifungal activity.Results The minimum inhibitory concentrations (MICs) of tetrandrine and ketoconazole alone against 21 clinical isolates of Candida parapsilosis complex were 32-64 mg/L and 0.031 25-2 mg/L,respectively.When ketoconazole was combined with tetrandrine,MICs of tetrandrine and ketoconazole were reduced to 2-8 mg/L and 0.008-0.25 mg/L respectively,and the FICI ranged from 0.09 to 0.5.The time-killing curves revealed that the fungal growth was delayed obviously in the combination group compared with the ketoconazole alone group and tetrandrine alone group.Conclusion Tetrandrine has obvious synergistic effects on ketoconazole against Candida parapsilosis complex in vitro.