Anti-Acanthamoeba Potential of Valproate Sodium; an In Vitro Study

Background and Objective: Conventional treatment of Acanthamoeba typically involves a combination drug strategy, but its efficacy in clinical settings remains incomplete. Evaluating the therapeutic potential of existing drugs is a way used to introduce effective treatments for infectious agents. This study aimed to assess the in vitro anti-Acanthamoeba effect of valproate (VPA). Materials and Methods: An experimental study was conducted using Acanthamoeba cysts belonging to the T۴ and T۵ genotypes. Cysts collected from the culture medium were exposed to gentamicin, polymyxin, and three different concentrations of VPA for varying durations (۱, ۴, ۶, and ۲۴ hours). The treated cysts were stained with trypan blue, and the percentage of growth inhibition was calculated. Additionally, the viability of treated cysts was assessed by culturing them on non-nutrient agar plates for one month. Results: The Acanthamoeba cysts of T۴ and T۵ genotypes showed susceptibility to VPA. The minimal cysticidal concentration (MCC) of VPA for maximum growth inhibition in both single and combination drug assays were ۱۰۰ and ۳ mg/ml, for durations of ۲۴ and ۴ hours, respectively. The growth inhibition observed in the groups exposed to gentamicin and polymyxin differed significantly from the growth inhibition in the group treated with ≥۱۰۰ mg/ml VPA (P< ۰.۰۵). Conclusion: VPA enhances the effects of gentamicin and polymyxin on Acanthamoeba. Combining a low concentration of VPA (≥۳ mg/ml) with gentamicin and polymyxin increases the potency and speed of action of these antibiotics.