Combination of a novel bacteriophage and d-serine effectively controls Vibrio parahaemolyticus growth in seafood

Abstract

Seafood is an important high-protein and low-fat food source prone to spoilage and may harbor food poisoning bacteria. Vibrio parahaemolyticus is a gram-negative halophilic bacterium that causes food poisoning. It is heat labile and can be eliminated through heating; however, V. parahaemolyticus may be present in seafood for raw consumption, such as sashimi. Recently, the use of bacteriophages or phages has been proposed as a non-thermal inactivation method for microbial control. Here, we characterized VF16, a novel phage that infects V. parahaemolyticus, and evaluated the effectiveness of the combination of VF16 with the antimicrobial amino acid d‑serine in controlling V. parahaemolyticus through antimicrobial testing in broth cultures and raw scallops. The morphology of VF16 was examined using transmission electron microscopy, which demonstrated that it had a long, flexible tail characteristic of a siphovirus. Genome sequencing revealed that VF16 is a novel phage belonging to the family Demerecviridae, subfamily Ermolyevavirinae, and genus Vipunavirus. Analysis of adsorption and one-step growth curve in a liquid medium indicated that Ca2+ and Mg2+ are necessary for one or more subsequent replication processes of VF16 but are not essential for its adsorption. The combination of VF16 and d‑serine completely inhibited the regrowth of V. parahaemolyticus in the liquid medium and effectively suppressed its growth in the scallop samples. No VF16-resistant mutants were isolated from the scallop samples treated with VF16 alone or in combination with d‑serine. The combination of phages and d-amino acids is an effective non-thermal inactivation method for controlling foodborne pathogens.

Keywords

• Bacteriophage
• Vibrio parahaemolyticus
• D-amino acid
• Demerecviridae
• Antimicrobial combination
• Seafood