LAUSR

Abstract Aeromonas veronii is one of the main pathogens that cause sepsis and ulcer syndrome in freshwater fish. Analysis of the results of recent epidemiological investigations revealed that the virulence of A. veronii and its tolerance to drugs have been increasing annually. To date, most of the research on A. veronii has focused on separation, and identification and drug susceptibility tests; research on its virulence factors and pathogenic mechanism has been relatively rare. In this study, the highly expressed protein of the A. veronii virulent strain TH0426, the cadaverine reverse transporter (CadA), was screened and obtained. We used the efficient suicide plasmid-mediated homologous recombination method to delete the cadA gene of A. veronii TH0426, and constructed a cadA gene deletion mutant. We found that, compared to wild-type strains, the pathogenicity to zebrafish and the cytotoxicity to EPC of △cadA deletion strain had decreased 33.1-fold and 4.1-fold, respectively, while the biofilm formation ability increased 1.6-fold. In addition, motility detection results indicated that ΔcadA reduced swimming ability. The results of flagellar staining and TEM demonstrated that the flagella of ΔcadA had been shed. In summary, the virulence and adhesion of A. veronii TH0426 significantly decreased after the deletion of cadA, providing some theoretical basis for the study of A. veronii virulence factors.