Isolation, identification of an Aeromonas veronii strain, and the immune response of hybrid sturgeon (Acipenser baerii ♀ x Acipenser schrenckii.) to the bacteria

Hybrid sturgeon (Acipenser baerii female x Acipenser schrenckii.) holds significant importance in the aquaculture industry in China. However, the recurring disease outbreaks caused by Aeromonas veronii have led to substantial economic losses in hybrid sturgeon culture. Further, the immune response of hybrid sturgeon to A. veronii infection remains poorly understood. Therefore, this study isolated and characterized a bacterial strain from affected fish, which was subsequently identified as A. veronii based on various characteristics. Moreover, severe histopathological changes, including degeneration and necrosis of the gill cells and intestinal villi, were observed in the diseased fish. Transcriptome data analysis using GO and KEGG enrichment revealed dynamic changes and enrichment of classical immune-and hematopoietic-related pathways following A. veronii infection. Additionally, significant changes were observed in the proportion of blood lymphocytes and antioxidative enzyme levels during A. veronii infection. Further investigations showed that the infected fish serum inhibited A. veronii replication. These findings provide valuable insights into the immune response of hybrid sturgeon against A. veronii infection.