Abstract：Objective To investigate the synergistic effect of tetrandrine(TET) on fluconazole(FLC) to Candida albicans biofilms. Methods The biofilms of C. albicans was built, and the minimum inhibitory concentration(MIC) of FLC alone and in combination with TET on each stage of biofilms forming were determined by the CLSI proposed M27-A microdilution method. The MIC of FLC alone and in combination with TET on re-suspended C. albicans biofilms were tested. Results In initial stage (0h), the MIC50 of FLC alone and combined with TET to the C. albicans biofilms were 0.25~64 μg/mL and 0.125~16 μg/mL respectively（P = 0.002）. In early stage (4th h) , the MIC50 were 8~256 μg/mL and 1~64 μg/mL（P = 0.000）. In middle stage (24th h) and advanced stage (48th h), both the MIC50 were ＞1024 μg/mL. The MIC of FLC alone to the re-suspended C. albicans biofilm(1×103 CFU/mL) were 0.25~64 μg/mL and 0.125~16 μg/mL when combined with TET. Both the MIC of FLC alone and in combination with TET were ＞64 μg/mL in the cells counts of 1×106 CFU/mL. Conclusions In vitro, TET acts synergistically with fluconazole in the activity against the C. albicans biofilms in initial stage (0h) and early stage (4th h), without synergistic effect in middle stage (24th h) and advanced stage (48th h); there is synergistic effect of tetrandrine to fluconazole against the re-suspended thalli of C. albicans biofilm(1×103 CFU/mL)，no synergy against the thalli(1×106 CFU/mL).
