The role and mechanism of icmF in Aeromonas hydrophila survival in fish macrophages.

Survival in host macrophages is an effective strategy for pathogenic bacteria to spread. Aeromonas hydrophila has been found to survive in fish macrophages, but the mechanisms remain unknown. In this paper, the roles and possible mechanisms of IcmF in bacterial survival in fish macrophages were investigated. First, a stable silencing strain icmF-RNAi was constructed by shRNA and RT-qPCR confirmed the expression of icmF was down-regulated by 94.42%. The expression of Hcp, DotU and VgrG was also decreased in icmF-RNAi. The intracellular survival rate of the wild-type strain was 92.3%, while the survival rate of icmF-RNAi was only 20.58%. The escape rate of the wild-type strain was 20%, while that of the icmF-RNAi was only 7.5%. Further studies indicated that the expression of icmF can significantly affect the adhesion, biofilm formation, motility and acid resistance of A. hydrophila, but has no significant effect on the growth of A. hydrophila even under the stress of H2O2. The results indicated that IcmF of A. hydrophila not only acts as a structural protein which participates in virulence-related characteristics such as bacterial motility, adhesion and biofilm formation, but also acts as a key functional protein which participates in the interaction between bacteria and host macrophages.