Biological Control of A eromonas salmonicida subsp. salmonicida Infection in Rainbow Trout ( O ncorhynchus mykiss ) Using A eromonas Phage PAS ‐1

Summary The potential control efficacy of A eromonas phage PAS ‐1 was evaluated against A eromonas salmonicida subsp. salmonicida infection in rainbow trout ( O ncorhynchus mykiss ) model in this study. The phage was co‐cultured with the virulent A . salmonicida subsp. salmonicida strain AS 05 that possesses the type III secretion system ( TTSS ) ascV gene, and efficient bacteriolytic activity was observed against the bacteria. The administration of PAS ‐1 in rainbow trout demonstrated that the phage was cleared from the fish within 200 h post‐administration, and a temporal neutralizing activity against the phage was detected in the sera of phage‐administrated fish. The administration of PAS ‐1 (multiplicity of infection: 10 000) in A . salmonicida subsp. salmonicida infected rainbow trout model showed notable protective effects, with increased survival rates and mean times to death. These results demonstrated that A eromonas phage PAS ‐1 could be considered as an alternative biological control agent against A . salmonicida subsp. salmonicida infections in rainbow trout culture.