Novel Antiamoebic Tyrocidine-Derived Peptide against Brain-Eating Amoebae.

() can cause keratitis, a sight-threatening infection, as well as a fatal brain infection termed granulomatous amoebic encephalitis, mostly in immunocompromised individuals. In contrast, () causes a deadly infection involving the central nervous system, recognized as primary amoebic encephalitis, mainly in individuals partaking in recreational water activities or those with nasal exposure to contaminated water. Worryingly, mortality rates due to these infections are more than 90%, suggesting the need to find alternative therapies. In this study, antiamoebic activity of a peptide based on the structure of the antibiotic tyrocidine was evaluated against and . The tyrocidine-derived peptide displayed significant amoebicidal efficacy against and . At 250 μg/mL, the peptide drastically reduced amoebae viability up to 13% and 21% after 2 h of incubation against and , whereas, after 24 h of incubation, the peptide showed 86% and 94% amoebicidal activity against and . Furthermore, amoebae pretreated with 100 μg/mL peptide inhibited 35% and 53% and , while, at 250 μg/mL, 84% and 94% and failed to adhere to human cells. Amoeba-mediated cell cytopathogenicity assays revealed 31% and 42% inhibition at 100 μg/mL, while at 250 μg/mL 75% and 86% and were inhibited. Assays revealed inhibition of encystation in both (58% and 93%) and (73% and 97%) at concentrations of 100 and 250 μg/mL respectively. Importantly, tyrocidine-derived peptide depicted minimal cytotoxicity to human cells and, thus, may be a potential candidate in the rational development of a treatment regimen against free-living amoebae infections. Future studies are necessary to elucidate the in vivo effects of tyrocidine-derived peptide against these and other pathogenic amoebae of importance.