Vol. 5, Issue 1, Part A (2020)

Material and methods: Two different live vaccinal mutant (aroA gene deleted E. coli O78 and aroA gene deleted S. Typhimurium STM-1 vaccines) were used in this study. The bacterial count was applied in each vaccine and different doses for each vaccine above and below the vaccinal dose were calculated and adjusted then inoculated in different groups of one day old SPF chicks and observed for 3 weeks for safety and shedding of the vaccinal organisms then challenged with the virulent strains of E. coli O78 and S. Typhimurium at 4^th week post vaccination.

Result: Protection percent of E. coli vaccine ranged from 62% to 88% in groups inoculated with different doses while it was 16% in the unvaccinated chicken control group. While it was 66% to 84% in S. Typhimurium vaccine in different vaccinated groups while it was 12% in the unvaccinated chicken control group.

Conclusion: Results of this study stated that the maximum release titer for aroA gene deleted E. coli vaccine was 5x10⁸ CFU/dose while it was 1x10⁹ for aroA gene deleted S. Typhimurium vaccine. On the other hand, the minimum release titer was 5x10⁶ for aroA gene deleted E. coli vaccine while it was 1x10⁶ for aroA gene deleted S. Typhimurium vaccine.