Synergistic in vitro activity of sodium houttuyfonate with fluconazole against clinical Candida albicans strains under planktonic growing conditions

AbstractContext: Fluconazole resistance is an intractable problem of treating Candida albicans, calling for more antifungal agents to enhance the activity of fluconazole.Objective: This work investigates the anti-C. albicans activities of sodium houttuyfonate (SH) and/or fluconazole and the associated mechanism.Materials and methods: The minimum inhibitory concentrations (MICs) of SH and fluconazole both ranging from 0.5 to 1024 μg/mL were determined by broth microdilution method in 19 C. albicans isolates, and their fractional inhibitory concentration index (FICI) was evaluated by checkerboard assay. After MICSH and/or MICfluconazole treatments, the expressions of IFD6, PHR1, ZAP1, ADH5, BGL2, XOG1 and FKS1 were analyzed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) in C. albicans 1601.Results and conclusion: The MICs of SH alone ranged from 32 to 256 μg/mL and decreased 2–16-fold in combination. SH showed strong synergism with fluconazole with FICI <0.13–0.5. In C. albicans 1...