Broad Antibacterial Activity and Mechanism of Garlic (Allium sativum L. cv. Uiseong) Extracts against Cell Wall of Aeromonas hydrophila

Aeromonas hydrophila is a pathogenic bacterium known for its resistance to antibiotics and its ability to cause infections in aquatic environments. This has made disease management more complex, making the development of alternative antimicrobial agents necessary. Uiseong garlic is a superior variety from Republic of Korea, renowned for its high level of beneficial compounds, making it a promising candidate for natural antimicrobial application. Therefore, this study aimed to investigate the antibacterial activity and mechanism of Uiseong garlic extracts against the cell wall of A. hydrophila. Uiseong garlic extracts were prepared using water and ethanol at 22^oC and 90^oC, respectively. The antibacterial activities of Uiseong garlic extracts were evaluated for their yield, antibacterial dynamics, leakage of bacterial intracellular proteins, and changes in morphological characteristics. Uiseong garlic extracts at 22^oC exhibited significant antibacterial activities against foodborne pathogens, particularly against 9 strains of A. hydrophila. In this study, the ethanol extract at 22^oC demonstrated significantly higher antibacterial activity compared to the water extract at 22^oC, with a similar pattern of antimicrobial dynamics with polymyxin B. The ethanol extract at 22^oC caused a higher concentration of leaked bacterial proteins (92.87 ± 0.46 μg/ml), indicating cell membrane disruption. Additionally, transmission electron microscopy analysis further confirmed that both extracts induced plasmolysis, leading to notable damage to the bacterial cell membrane. Therefore, ethanol extract of Uiseong garlic was demonstrated as a promising alternative to antibiotics for controlling A. hydrophila.