Biological control evaluation of bacteriophage freeze-dried powder against Aeromonas hydrophila infection, based on whey protein/trehalose.

Aeromonas hydrophila, as an important zoonotic conditional pathogen, can cause various diseases such as bacterial septicemia in fish, as well as acute gastroenteritis in humans. Bacteriophages, due to their significant advantage in combating antibiotic-resistant bacteria, have become a research hotspot for novel biological control tools. This study focused on A. hydrophila phage 003s1, which maintained high activity under a wide range of conditions from pH 3 to 11 and at temperatures from 30 to 60°C. After 60 min of ultraviolet irradiation, 63.97% of the original activity remained. To develop a novel antimicrobial agent against A. hydrophila, the phage 003s1 was loaded into different protective agents and subjected to freeze-drying. It was found that using 1% whey protein (WPI) as the protective agent resulted in the optimal viability of the phage after freeze-drying. When stored at 4°C for 6 months, the titer decreased by only 0.86 log10 PFU/mL. In the zebrafish embryo infection model, after treatment with phage powder at a MOI of 0.1, the survival rate of embryos infected with the minimum lethal dose of A. hydrophila significantly increased to 56.67%. In summary, the phage powder developed in this study not only exhibits excellent storage stability but also demonstrates significant protective effects in the zebrafish infection model, providing an innovative antimicrobial agent for the biological control of A. hydrophila.