Purpose

Acanthamoeba spp. are free-living amoebas with worldwide distribution and play an important role as disease-causing agents in humans. Drug inability to completely eradicate these parasites along with their toxic effects suggest urgent need for new antimicrobials. Nisin is a natural antimicrobial peptide produced by Lactococcus lactis. Nisin is also the only bacteriocin approved for use in food preservation. In this work, we analyzed the effect of nisin on the growth of Acanthamoeba castellanii trophozoites.

Methods

A total of 8 × 10⁴ trophozoites were exposed to increasing concentrations of nisin to determine its activity. Changes in cell membrane and cellular cycle of trophozoites were investigated by flow cytometry, and nisin cytotoxicity in mammalian cells was evaluated in L929 cells by MTT method.

Results

After 24 h exposure to increasing nisin concentrations, an IC₅₀ of 4493.2 IU mL⁻¹ was obtained for A. castellanii trophozoites. However, after 72 h a recovery in amoebic growth was observed, and it was no longer possible to determine IC₅₀. Flow cytometry analysis showed that nisin has no effect on the membrane integrity. Treatment with nisin induced cell-cycle arrest during G1 and S phases in A. castellanii trophozoites, which recovered their growth after 72 h.

Conclusion

This is one of the first studies showing the effect of internationally approved nisin against A. castellanii trophozoites. Nisin caused cell-cycle arrest in trophozoites, momentarily interfering with the DNA replication process. The data highlight the amoebostatic activity of nisin, and suggest its use as an adjuvant for the treatment of infections caused by Acanthamoeba spp.

中文翻译：

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Nisin 诱导自由生活的 Amoebae Acanthamoeba castellanii 的细胞周期停滞

目的

棘阿米巴属 是自由生活的变形虫，分布于世界各地，在人类中作为致病因子发挥着重要作用。药物无法完全根除这些寄生虫及其毒性作用表明迫切需要新的抗菌剂。Nisin 是一种由乳酸乳球菌产生的天然抗菌肽。Nisin 也是唯一获准用于食品保鲜的细菌素。在这项工作中，我们分析了乳酸链球菌肽对卡氏棘阿米巴滋养体生长的影响。

方法

将总共​​ 8 × 10 ^{4 个}滋养体暴露于浓度不断增加的乳酸链球菌肽以确定其活性。采用流式细胞仪研究细胞膜和滋养体细胞周期的变化，采用MTT法在L929细胞中评价乳链菌肽对哺乳动物细胞的细胞毒性。

结果

在暴露于增加的乳链菌肽浓度 24 小时后，获得了A. castellanii滋养体的 IC ₅₀为 4493.2 IU mL ^{-1 。}然而，在 72 公顷后观察到阿米巴生长恢复，不再可能确定 IC ₅₀。流式细胞仪分析表明乳酸链球菌肽对膜完整性没有影响。在A. castellanii滋养体中，乳酸链球菌肽在 G1 和 S 期诱导细胞周期停滞，其在 72 小时后恢复生长。

结论

这是显示国际认可的乳酸链球菌肽对A. castellanii滋养体影响的首批研究之一。Nisin 在滋养体中引起细胞周期停滞，暂时干扰 DNA 复制过程。数据突出了乳酸链球菌肽的变形活性，并建议将其用作治疗由棘阿米巴属引起的感染的佐剂。