A novel defensin‐like peptide C‐13326 possesses protective effect against multidrug‐resistant Aeromonas schubertii in hybrid snakehead (Channa maculate ♀ × Channa argus ♂)

Abstract The purpose of this study was to investigate whether a defensin‐like antimicrobial peptide (C‐13326 peptide) identified in Hermetia illucens could possess protective effect against multidrug‐resistant Aeromonas schubertii in hybrid snakehead ( Channa maculate ♀ × Channa argus ♂). The cDNA of C‐13326 peptide comprised 243 nucleotides encoding 80 amino acids, with six conserved cysteine residues and the classical CSαβ structure. The recombinant expression plasmid pPIC9K‐C‐13326 was constructed and transformed into GS115 Pichia pastoris , and the C‐13326 peptide was expressed by induction with 1% methanol. The crude extract of C‐13326 peptide was precipitated by ammonium sulfate, assayed by Braford method, detected by tricine‐SDS‐PAGE, evaluated by BandScan software and identified by liquid chromatography‐mass spectrometry. The C‐13326 peptide was shown to have inhibitory activity against the growth of multidrug‐resistant A. schubertii DM210910 by using the minimum growth inhibitory concentration and Oxford cup method. In addition, scanning electron microscopy analysis suggested that C‐13326 peptide inhibited the growth of A. schubertii DM210910 by damaging the bacterial cell membrane. To explore the role of peptide C‐13326 in vivo, hybrid snakehead was fed with peptide C‐13326 as feed additives for 7 days. The results revealed that C‐13326 peptide could significantly down‐regulate the expression levels of IL‐1β , IL‐8 , IL‐12 and TNF‐α ( p < .05), and significantly improved the survival rate of hybrid snakehead after challenging with A. schubertii DM210910. Therefore, the C‐13326 peptide is a promising antimicrobial agent for A. schubertii treatment in aquaculture.