Baicalin Against Aeromonas Hydrophila in Vitro and its Bacteriostatic Protection Effects for Yellow Catfish Infection

Abstract

ABSRTACTThe study aimed to reveal the inhibitory effects of baicalin on Aeromonas hydrophila infection. In vitro, the minimum inhibitory concentration of baicalin against A. hydrophila was determined. Based on the determination of MIC, growth curve, alkaline phosphatase (AKP) content in the cell wall, biofilm formation, and protein levels were evaluated using turbidimetry, colorimetry, crystal violet, and Bradford assays, respectively. Additionally, morphological changes in A. hydrophila were examined using transmission electron microscopy. In vivo, 270 yellow catfish were randomly labeled into six groups: except for the control group, fish in the other groups were infected with A. hydrophila introduced 4 h after intraperitoneal administration of baicalein.Subsequent to daily monitoring of mortality rates, liver, spleen, and intestinal tissues were harvested after a 3-day period for the assessment of organ indices, analysis of antioxidative and immune parameters, and examination of gut microbial composition. The results showed that baicalin treatment, the cell wall of A. hydrophila was compromised, leading to the disappearance of its normal structure. Baicalin exhibited a remarkable ability to inhibit the formation of biofilm by A. hydrophila, and enhance the release of intracellular proteins (P<0.05). In an in vivo setting, baicalin showed promise in improving the survival rate of catfish infected with A. hydrophila. Furthermore, the elevated liver index and reduced spleen and intestinal indexes observed in infected catfish were restored with the administration of baicalin (P<0.05). Meanwhile, appropriate doses of baicalin had better antioxidation and immunoenhancement effects (P<0.05). The intestinal microbiome analysis showed that baicalin significantly increase the number of OTUs infected with A. hydrophila, and restored the abundance of Barnesiellaceae, Enterobacteriaceae, Plesimonnas and UBA1819 (P<0.05). In conclusion, baicalin has the potential to improve the survival rate, antioxidant and immune levels, reduce inflammation, and regulate intestinal microbial diversity of yellow catfish against A. hydrophila infection.

Keywords: Baicalin, Aeromonas hydrophila, Antioxidation, Immunoenhancement, Gut microbiota