The current work aimed to study four different prepared Ps. fluorescensantigens (formalin killed bacterin, extracellular product (ECP) suspension, sonicated cells (SC) suspension and mixture of ECP and SC suspension) to develop the best adequate strategy to control such infection in cultured Nile tilapia.
The nitroblue tetrazoilum (NBT), neutrophil adherence and lysozyme activity of vaccinated fish showed significant increases in all immunized groups in comparison with control at  2 and 4 weeks post vaccination. Serum bactericidal activity and antibody titer were significantly increased in all immunized groups at all periods of the experiment. The mixture of ECP and SC antigen showed the best serum bactericidal activity and antibody titer against Ps. fluorescens. 
The relative percent of survival (RPS) after challenge with Ps. fluorescens at 4, 6 and 8 weeks post vaccination was significantly increased in all immunized groups in comparison with control. There were significant increases in RPS among a group immunized with a mixture of  ECP and SC antigen than other three immunized groups at 4 weeks only. The higher values of the relative percent of survival were seen in the mixture of  ECP and SC antigen followed by formalin killed antigen, sonicated cell antigen then the extracellular product antigen.
It could be concluded that all prepared vaccines are efficient against Ps. fluorescens infection, howevera mixture of sonicated and extracellular product antigen seemed superior to other vaccines especially in bactericidal activity, antibody titer and RPS against Ps. fluorescens