Baicalin enhances antioxidant, inflammatory defense, and microbial diversity of yellow catfish () infected with .

Introduction: The aim of this research was to clarify the mechanism through which baicalin exerts its inhibitory effects on infection.

Methods: The antibacterial efficacy of baicalin was assessed by determining its minimum inhibitory concentration (MIC) against . Various parameters, including the growth curve, cell wall integrity, biofilm formation, AKP content, and morphological alterations of , were analyzed. In vivo experiments involved the administration of 4 h postintraperitoneal injection of varying doses of baicalin to induce infection, with subsequent monitoring of mortality rates. After a 3 d period, liver, spleen, and intestinal tissues were harvested to evaluate organ indices, antioxidant and immune parameters, as well as intestinal microbial composition.

Results: The findings indicated that baicalin treatment resulted in the disruption of the cell wall of , leading to the loss of its normal structural integrity. Furthermore, baicalin significantly inhibited biofilm formation and facilitated the release of intracellular proteins ( < 0.05). In vivo, baicalin enhanced the survival rates of yellow catfish infected with . Compared to the control group, the liver index of yellow catfish was elevated, while the spleen and intestinal indices were reduced in the baicalin-treated group ( < 0.05). Additionally, baicalin at an appropriate dosage was found to increase levels of SOD, GSH, CAT, ACP, and AKP in yellow catfish ( < 0.05), while simultaneously decreasing MDA accumulation and the mRNA expression of inflammatory markers such as Keap1, IL1, IFN-γ, and TNF-α, ( < 0.05). Moreover, baicalin significantly enhanced the operational taxonomic unit (OTU) count in -infected yellow catfish ( < 0.05), restoring the abundance of Barnesiellaceae, Enterobacteriaceae, Plesiomonas, and ( < 0.05).

Discussion: In summary, baicalin demonstrates the potential to improve the survival rate of yellow catfish subjected to infection, augment antioxidant and immune responses, mitigate inflammation, and enhance intestinal microbial diversity.