Effect of antimicrobial peptide EC-hepcidin1 on inhibition of Streptococcus iniae in primary cell culture of (Oncorhynchus mykiss)

Streptococcosis is the most destructive disease in world aquaculture, and many efforts have been made to curb this bacteria. In this study, the ability of artificial polypeptide hepcidin (EC-hepcidin1) was evaluated to control infection caused by Streptococcus iniae in primary cell culture of rainbow trout (Oncorhynchus mykiss). Antibacterial effects of this polypeptide were examined by disk diffusion and minimum inhibitory concentration (MIC) and minimum bactericidal concentration of EC-hepcidin1 were measured against Streptococcus iniae. The primary cells were produced from fish fin, and the toxicity range of the peptide was determined for the cells. The primary cells of the rainbow trout were infected with Streptococcus iniae and antimicrobial activity of EC-hepcidin1, as well as viability of the cells, were evaluated. Results showed the MIC and MBC were 75 and 150 μg/mL, respectively. The level of peptide toxicity on fish cells show that EC-hepcidin1 had low toxicity after 48h in the range of 25 to 400 μg/mL, and the cells had a viability of 60% to 80%. The viability of the cells was 55% after induction of the bacteria (10: MOI), and the survival rate of cells was increased up to 90% after induction of bacteria (10: MOI) with 150 μg/mL peptide. In conclusion, the EC-hepcidin1 has shown an antibacterial effect on Streptococcus iniae (in vitro) and the peptide has low toxicity to fish cells. It has increased the vitality of cells infected with Streptococcus iniae. Therefore, complementary clinical research on larval stage, as well as broodstock of rainbow trout, could be suggested in the future. In conclusion, the EC-hepcidin1 has been shown an antibacterial effect on Streptococcus and low toxicity to fish cells. It has increased the vitality of cells infected with Streptococcus. Therefore, complementary clinical research on larval stage and broodstock of fish could be suggested.