چكيده لاتين
Vibrio parahaemolyticus, a member of the Vibrionaceae family, is a curved, rod-shaped, Gram-negative bacterial species that was first identified in the 1950s by a Japanese researcher, Tsuneyo Fujino, in Osaka. This bacterium is recognized as a key agent of gastroenteritis caused by the consumption of raw or undercooked seafood. The halophilic nature of V. parahaemolyticus and its widespread presence in marine environments, particularly in tropical and subtropical regions, have established it as a predominant pathogen in fish, crustaceans, and mollusks. Generally, V. parahaemolyticus poses a significant threat to aquaculture systems of fish and shellfish. Diseases such as Acute Hepatopancreatic Necrosis Disease (AHPND), superficial ulcers, skin lesions, systemic infections, and septicemia in fish and other aquatic species are caused by this bacterium. In addition to aquatic organisms, V. parahaemolyticus can act as a human pathogen. The bacterial toxins damage intestinal cells, increasing fluid secretion and causing symptoms such as diarrhea, abdominal pain, nausea, vomiting, and mild fever.
The primary treatment for infections caused by V. parahaemolyticus includes fluid and electrolyte replacement and the use of antibiotics. However, due to the economic challenges of using antibiotics in aquaculture and the rising issue of antibiotic resistance, there is a need for safe and cost-effective alternatives. One promising alternative is the use of bacteriophages.
In this study, compost and wastewater samples, including urban and hospital effluents, were collected to isolate a lytic bacteriophage against V. parahaemolyticus. The isolated phage was characterized for its morphology, host range, stability under various conditions (temperature, salinity, UV radiation, and pH), adsorption rate and time, one-step growth, and its effects on biofilm control. Additionally, the antibacterial effects of the phage were evaluated using the Galleria mellonella larvae as in-vivo model.
The isolated lytic phage showed stability within a temperature range of -20 °C to 60 °C, a pH range of 3 to 11, and sodium chloride concentrations of 1% to 30%. Furthermore, it remained stable under UV radiation (254 nm) for up to 20 minutes. The latent period of the phage was 40 minutes, and it produced 106 phage particles per bacterial cell. After 10 minutes, 40% of the phages attached to the bacterial cells in the presence of calcium ions, while 70% attached in the presence of magnesium ions, highlighting the significant role of these ions in the early stages of phage adsorption. The highest adsorption rate (97.5%) occurred after 35 minutes in the presence of calcium ions, compared to 70% in the presence of magnesium ions or the control group.
The phage exhibited strong antibacterial activity at an MOI of 0.1. evaluation of its antibacterial effects in the G. mellonella larvae model revealed a positive impact on larval survival in pre-treatment, post-treatment, and simultaneous treatment groups.
Based on the findings of this study, the isolated bacteriophage shows high potential for use in phage therapy applications.
