Colibacillosis is one of the most important diseases of the poultry industry around the world. It causes considerable economic damage every year. Salmonella
Enteritidis and Salmonella
Typhimurium are important cause of food-borne illness. Vaccination plays an important role in the overall bio-security system. This study aimed to the use of enumeration of viable bacterial count as an alternative method to challenge test to quantify the colony-forming units (CFU) of specified live bacterial poultry vaccines.
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 4th 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.