Protective effectiveness of feeding phage cocktails in controlling Vibrio harveyi infection of turbot Scophthalmus maximus

Abstract Vibrio harveyi can cause infections and diseases in a variety of marine vertebrates and invertebrates, which is very harmful to the aquaculture industry. In this study, two phages were isolated and named VB_VhaP_Vh-5 (referred to as PVHp5) and VB_VhaM_VH-8 (referred to as PVHp8). Morphological analysis showed that PVHp5 belonged to Autographiviridae phage, while PVHp8 belonged to Myoviridae family. The results of genome analysis showed that PVHp5 had a double stranded DNA genome with a length of 42,485 bp and a G + C content of 44.48%, including 49 ORFs. PVHp8 also had a double stranded DNA genome with a length of 87,255 bp and a G + C content of 36.08%. It contained 150 ORFs and encodes two tRNAs, one of which was tRNA (pseudotrna). No genes related to drug resistance and virulence were detected in the two phage genomes. In vitro experiment, compared with the control group, the phage treatment group significantly inhibited the growth of V. harveyi VH5 (P   0.05). Feeding phage cocktails may be another optimal therapeutic agent against V. harveyi infection in turbot culture.