Isolation and characterization of the novel phage BP14 for lysing<i> Vibrio</i><i> parahaemolyticus</i> and reducing virulence proteins

Abstract

Accumulating evidence has indicated that Vibrio parahaemolyticus stains resistant to multiple drugs may pose a serious threat to public health and could lead to global economic. Phage therapy is an alternative and ecofriendly biocontrol strategy for the prevention and control of diseases in the aquatic systems. Therefore, this study was oriented to isolate and characterize the applicability of phages for V. parahaemolyticus (VP) lysis in aquaculture. Here, twenty-two lytic bacteriophages (BP1-22) were isolated from sewage collected in a local shrimp farming area and from the tissue of AHPND-infected shrimp and oysters collected in Taiwan. Among these, phage BP14 could effectively lyse V. parahaemolyticus, this bacterium causes acute hepatopancreatic necrosis disease (AHPND), resulting in severe mortality in Litopenaeus vannamei and Penaeus monodon, two marine shrimp species that are commonly grown in aquaculture farms. Characterization of the morphology of the virion particle via electron microscopy revealed that the virus belonged to the family Inoviridae, as suggested by its filamentous shape. The genome of phage BP14 was composed of 9071 bp with a 43.85% GC content and was inserted into a chromosome depending on the occurrence of Xer site-specific recombination. Furthermore, phage BP14 established a chronic productive infection, thus continuously releasing virions from infected cells. A viral load of approximately 12 plaque-forming units (PFUs) per cell was determined for phage BP14 under laboratory growth conditions. Western blotting and ELISA analyses revealed that phage BP14 decreased the levels of toxinPirB and PirA protein by approximately 40%-60% compared to the wild-type VP. Collectively, our findings demonstrated the potential applicability of phage BP14 for the biological control of VPAHPND.