Control of Edwardsiella tarda infection in turbot Scophthalmus maximus (L.) using phage vB_EtaM_ET-ABTNL-9

In recent years, turbot (Scophthalmus maximus L.) ascites caused by Edwardsiella tarda has occurred frequently in China, causing serious economic losses. In this study, with E. tarda ET9 as the host bacteria, a lytic phage was isolated and named vB_EtaM_ET-ABTNL-9 (referred to as PETp9). The effect of using phage to prevent and control E. tarda infection in turbot was discussed. The results showed that the best preventive effect was achieved after 7 days of feeding phage with multiplicity of infection (MOI) = 10 in the phage-feeding experiment; in the phage-injection therapy, treatment was most effective when the phage with MOI = 10 was injected intraperitoneally immediately after the challenge; in the phage-immersion therapy, the best therapeutic effect was obtained when the infected turbot were immersed in phage-seawater mixture (MOI = 10) for 3 h. During the experimental period, the activities of non-specific immune-related enzymes in the blood of turbot were significantly increased in the untreated group, while that of the phage treated group showed a downward trend and gradually reached normal levels. It was also observed that a certain concentration of phages was present in both turbot cultured water and the intestinal tract during the experiment. Therefore, phage may be another effective control agent against E. tarda infection in turbot culture.

Automated summary

This study discovered a lytic phage named PETp9 which can effectively prevent and control Edwardsiella tarda infection in turbot. The best preventive effect was achieved after 7 days of feeding phage with MOI = 10, and the most effective treatment in the phage-injection therapy was when the phage with MOI = 10 was injected intraperitoneally immediately after the challenge. In phage-immersion therapy, the best therapeutic effect was obtained when the infected turbot were immersed in phage-seawater mixture (MOI = 10) for 3 hours. Furthermore, the activities of non-specific immune-related enzymes in the blood of turbot treated with phage gradually reached normal levels.