Vibrio parahaemolyticus is a halophilic, Gram-negative bacterium widely distributed in coastal and estuarine areas (Lovell, 2017; Su and Liu, 2007). Pathogenic V. parahaemolyticus typically has heat-unstable and heat-stable direct hemolysins, as well as heat-associated hemolysins. These are encoded by the tlh, tdh, and trh genes. Eating contaminated raw or undercooked seafood is the most prevalent method of acquiring V. parahaemolyticus. The symptoms of V. parahaemolyticus infection include nausea, vomiting, fever, diarrhea, and even sepsis in some severe cases. The annual report from the United States indicated that V. parahaemolyticus contamination resulted in about 45,000 illnesses (Ashrafudoulla et al., 2020). From 2010 to 2020, 1722 foodborne disease outbreaks due to V. parahaemolyticus were reported in China, resulting in 27,212 illnesses, 5944 hospitalizations, and 2 deaths (Chen et al., 2023). Food poisoning caused by V. parahaemolyticus has become the most prevalent of all microbial food poisoning, especially in coastal areas (Zhong et al., 2022). As a result, the risk of V. parahaemolyticus infection is increasing rapidly, and strict action is needed to keep seafood safe.

Currently, the overuse of antibiotics has significantly decreased the effectiveness of controlling V. parahaemolyticus, resulting in widespread antibiotic-resistant bacteria (Mok et al., 2019). In general, these antimicrobial resistance (AMR) foodborne pathogens may pose the greatest risks to public health because of their wide transmission through the food chain (Samtiya et al., 2022). Moreover, V. parahaemolyticus can also form biofilms on the surface of seafood products and processing equipment during aquaculture, storage and processing (Han et al., 2016). Biofilms were considered to be a relatively common form of development in which microorganisms exist by attaching to living or abiotic surfaces, embedded in self-generated extracellular polymer materials (EPS) (Hall and Mah, 2017). V. parahaemolyticus cells nestled within the biofilm structures exhibit exceptional resistance to a wide range of antibiotics, as well as to normal food industry conditions of desiccation, heat, and cold. Antibiotics are particularly ineffective because they cannot get inside the biofilm to kill bacteria. Thus, it has become imperative to develop biocontrol agents that can effectively replace antibiotics to control V. parahaemolyticus infections.

Bacteriophages are viruses that use the lysis cycle to infect and then lyse host bacteria. In the two decades following the discovery of phages, several commercial phage products appeared. But since the discovery of penicillin in 1928, the use of phages as antibacterial agents has declined in most parts of the world (O'Sullivan et al., 2019). Notably, the emergence of multi-drug resistant bacteria has prompted renewed interest in the use of phages as therapeutic antimicrobials. Phages can only lyse their host bacteria. Nontarget bacteria are not affected by phages and they do not persist for a long time without a host in the environment, unlike antibiotics and biocides, which can persist in soil, leading to a risk of antibiotic resistance (Jones et al., 2012). Phages also can penetrate bacterial biofilms and lyse the cells within them, unlike many antibiotics that are most effective against planktonic cells (Montso et al., 2021).

Phages, with their host specificity and lytic activity, are currently regarded as the most promising alternative to bactericides. At present, many phages for the treatment of bacterial infections have been developed (Gambino et al., 2020; Yuan et al., 2019). They have the ability to successfully prevent the growth of foodborne pathogens, reduce food industry contamination losses, and the use of phages does not change the colour, taste, texture or nutritional properties of food (Wang et al., 2023). The application of V. parahaemolyticus phage VPT02 on ready-to-eat raw fish slices resulted in a bacterial reduction of 3.9 log10 CFU/g and remained active at low temperature (5 °C) (You et al., 2021). Treating artificially contaminated oysters with phage OMN can significantly reduce the number of V. parahaemolyticus on the surface of oysters (Zhang et al., 2018). The novel V. parahaemolyticus phage vB_VpaP_SJSY21 treatment significantly improved the survival rate of Litopenaeus vannamei and reduced the load of V. parahaemolyticus in the intestinal tract (Xu et al., 2023). Although these studies have demonstrated the potential of V. parahaemolyticus phages as antibacterial agents, their narrow host range and the rapid emergence of bacterial resistance still present persistent challenges for phage therapy. Therefore, to ensure long-term control of V. parahaemolyticus and ensure the sustainability of phage therapy, it is essential to continuously isolate novel phages with broader host range and enhanced stability.

In this study, phages were firstly isolated from oysters collected from Shanghai seafood markets. Secondly, the general characteristics of the phages were characterized and the genome sequences were analyzed to evaluate the feasibility of their future applications. Finally, we investigated the inhibition of V. parahaemolyticus by single phage and phage cocktails in vitro and their efficacy in the clearance of V. parahaemolyticus in seafood.