Contribution of flagellar cap gene in virulence and pathogenicity of Aeromonas veronii

Aeromonas veronii is an important zoonotic and aquatic pathogen that causes a number of illnesses in both humans and animals. It is related to gastroenteritis, skin and soft tissue infections and bacteremia in humans, as well as causing significant economic losses in aquaculture owing to fish sepsis. Here, we constructed the flagellar cap gene (fliD) mutant strain of A. veronii by suicide plasmid-mediated homologous recombination system and analysed its characteristics. It was found that the deletion of fliD had no effect on growth and biochemical properties and could be inherited stably. However, the motility of A. veronii Delta fliD was significantly reduced, the flagellum was defective and the biofilm formation was attenuated compared with that of A. veronii wild-type strain. In vivo experiments revealed that the colonization capacity of Delta fliD was significantly lower than that of the wild-type strain in the period of first 24 h, and the median lethal dose (LD50) was 56 times higher than that of the wild-type strain. The Cyprinus carpio infected with the wild-type strain indicated faster death speed and more severe clinical signs compared to Delta fliD strain. These results suggest that fliD is closely related to the virulence of A. veronii and plays an important role in pathogenicity, providing the foundation for pathogenic mechanism studies of A. veronii.

Automated summary

Aeromonas veronii is an important zoonotic and aquatic pathogen. This study found that the mutation of its flagellar cap gene (fliD) led to reduced motility, defective flagellum, and attenuated biofilm formation. In vivo experiments showed that the mutant strain had lower colonization capacity and higher median lethal dose compared to the wild-type strain.