Potential therapeutic use of dermaseptin S₄ from the frog Phyllomedusa sauvagii and its derivatives against bacterial pathogens in fish.

This article focuses on the antimicrobial properties and mechanisms of dermaseptin S4 (DS4) peptides and their derivatives, which are antimicrobial peptides (AMPs) derived from the skin of the frog *Phyllomedusa sauvagii*. The study evaluated the native DS4 (1–28) peptide and two modified forms, DS4 (1–28)a and DS4 (1–26)a, against two marine pathogenic bacteria, *Vibrio harveyi* and *Vibrio anguillarum*, common causes of fish diseases in aquaculture. Results showed that the truncated and amidated peptide DS4 (1–26)a exhibited the highest antibacterial activity with minimal hemolytic effects on fish erythrocytes, acting primarily by disrupting bacterial membranes and cell walls, as confirmed by electron microscopy and membrane integrity assays. The peptides' antimicrobial efficacy was reduced in the presence of physiological cations, and their stability in fish serum was limited, indicating the need for further in vivo studies and optimization for practical aquaculture applications.