Abstract
Aeromonas hydrophila is a significant pathogen to freshwater farmed animals, and antibiotics are usually used to control the bacterial septicemia caused by A. hydrophila. Due to the severe situation of development and spread of antibiotic resistance, there are stricter restrictions on antibiotics used in aquaculture. To evaluate the feasibility of glycyrrhetinic acid β (GA) as an alternative therapy against bacterial infection, in this study, an A. hydrophila isolated from diseased fish is used to test the antibacterial, anti-virulence activity and therapeutic effect of GA in vitro and in vivo, respectively. Results showed that GA did not affect the growth of A. hydrophila in vitro, while it could down-regulate (p < 0.05) the mRNA expression of the hemolysis-related genes hly and aerA, and significantly inhibited (p < 0.05) hemolytic activity of A. hydrophila. In addition, in vivo test showed that oral administration of GA was ineffective in controlling acute infections caused by A. hydrophila. In conclusion, these findings suggested that GA was a potential anti-virulence candidate against A. hydrophila, but the application of GA for the prevention and treatment of A. hydrophila-related diseases was still a long way.