Study On Tetrandrine As A Synergist To Azoles In Candida Albicans

Objective:To investigate the synergistic effect of tetrandrine to the anti- C. albicans activity of fluconazole in vivo and the anti-C, albicans activity of ketoconazole in the yeast form of C. albicans in vitroMaterials and Methods:Animal model of vaginal candidiasis was established in mice by intravaginal inoculation of C. albicans. The infected mice were separated into 10 groups randomly. The mice of the groups given drugs were treated with fluconazole and tetrandrine alone or simultaneously at different doses once daily for 7 consecutive days, started at day 3 after inoculation. The control groups were not given any drugs. Both of tetrandrine and fluconazole were administered intravaginally at 26 mg/(kg·d) as high dose or 13 mg/(kg·d) as low dose. The synergistic efficacy of tetrandrine was assessed by colony forming units (CFU) counts, microscopic examination of the vaginal lavage fluid and the histopathologic examination of the vagina at day 2, 6, 11 after inoculation.The highest non-cytotoxic dose of tetrandrine in the yeast form of 16 C. albicans was determined by the microdilution test. The minimal inhibitory concentrations (MICs) of ketoconazole alone and combined with tetrandrine were determined in 16 C. albicans strains by CLSI M27-A microdilution method. The synergistic effect of tetrandrine on ketoconazole was further confirmed by time-kill curves method.Results:On the day 11 after inoculation, compared with the mice given fluconazole at 26 mg/kg alone, in the group treated with tetrandrine and fluconazole at 26 mg/kg simultaneously (FLC₂₆+ TET₂₆ group), the number of the CFU decreased significantly (2.11±0.36×10⁴ vs 0.19±0.04×10⁴ CFU/mL, P=0.039). Compared with the other 9 groups, the microscopic examination of the vaginal lavage fluid indicated none oflhe pseudohyphae was shown in the FLC₂₆+TET₂₆ group, the difference of the pseudohypha grades in the 10 groups had statistic significance(x²=33.084, P=0.000). The histopathologic findings illustrated vaginal mucosal edema was slighter, the infiltrated inflammatory cells were less and none of pseudohyphae was seen in vaginal canal and vaginal mucosa in this group. However, in the other nine groups, the microscopic examination showed some pseudohyphae or pseudohypha clumps, the histopathologic findings indicated vaginal mucosal edema was severe, abundant inflammatory cells infiltrated into vaginal mucosa and submucosa, a number of pseudohypha exsited in vaginal canal and vaginal mucosa.The highest non-cytotoxic dose of tetrandrine to the yeast form of 16 C. albicans was 30μg/mL. The MICs of ketoconazole alone or combined with tetrandrine (30μg/mL) to the yeast form of C. albicans were 1-32μg/mL or 0.0038-0.25μg/mL, they had statistic difference(t=24.624, P=0.000). Meanwhile, the so-called trailing disappeared. The time-kill curve indicated that at 48 h of exposure to tetrandrine and ketoconazole, the CFU of every strain of C. albicans exposed to tetrandrine and ketoconazole decreased＞2 log₁₀ CFU/mL compared with that of the strains exposed to ketoconazole alone, they had statistic difference (P=0.000).Conclusion:Tetrandrine at 26 mg/(kg·d) can improve the topical anti-C, albicans activity of fluconazole in vivo. Tetrandrine can enhance the anti-C, albicans activity of ketoconazole in vitro.