The deficiency of virulence factor AerA in Aeromonas veronii alleviates intestinal injury and microbiota disorders in largemouth bass (Micropterus salmoides).

Aeromonas veronii is a zoonotic pathogen that causes considerable mortality in aquaculture, with typical manifestations of intestinal injury. Aerolysin (AerA) is a pivotal virulence factor that influences Aeromonas pathogenicity. This study aimed to investigate the functional mechanism of AerA in A. veronii-induced intestinal injury in largemouth bass (Micropterus salmoides). The results revealed that wild-type (WT) A. veronii infection provoked a noteworthy augmentation of abundance of A. veronii in the intestine, accompanied by inflammation, partial repression of immune response, intestinal injury and high mortality. Compared to WT A. veronii infection, significantly reduced levels of A. veronii in the intestine, inflammation, intestinal injury and mortality, as well as enhanced immune response were observed in AerA mutant (ΔAerA) A. veronii infection. In addition, an increase in abundance of A. veroniii in the intestine, inflammation, and higher mortality were once again perceived subsequent to the use of recombinant AerA protein to compensate for AerA depletion. These results demonstrated that AerA deficiency reduce the increased abundance of A. veronii in the intestine, inflammation and intestinal injury caused by A. veronii infection, thereby reducing the virulence of A. veronii. Our findings enhance the understanding of attributes and functional role of AerA in A. veronii infection, and provide guidance for the development of disease control strategies.