Fowl cholera is a septicemic respiratory complex caused by Pasteurella multocida, widely distributed in poultry and other avian species and of major economic importance. A total of 37 different inactivated Pasteurella multocida vaccines from different sources either locally prepared or imported from different sources were comparatively tested for relative potency following both single dose and booster dose vaccination assays. The study objective was to minimize the time factor exhausted in the evaluation processes of the inactivated fowl cholera vaccines. So it is planned to compare between single and booster dose vaccinations and their related potency. Correlation between protection associated with the single dose and booster dose vaccination were evaluated and average requirement for protection was 43.7% in single dose vaccination assay compared to 76.2 % associated with booster dose vaccination assay. In the same concern, the correlation between both assays for the seroconversion was estimated using ELISA and the minimum requirement was 1.8× cut off value in the single dose vaccination assay compared to 2.25× cut off value in the booster dose vaccination assay. In conclusion, single dose vaccination assay could be valuable in the evaluation of inactivated fowl cholera vaccines through determination of protection indices and/or estimation of humoral immune response if the above mentioned data is considered.
Background: E. coli infection is considered as an important bacterial problem associated with significant economic losses and usually associated with a variety of disease conditions, including acute septicaemia, haemorrhagic enteritis, pericariditis, salpingitis and complicated air saculitis. These considerations suggest that control of E. coli by vaccination could be of great value especially live vaccine that based on defined mutations that impair and non-revering virulence. Material and Methods: Wild type O78 strain, Live O78 aroA gene deleted vaccine and Live O78 crp gene deleted vaccine were used to accomplish this study. Phenotypic characterization was adopted by studying the cultural, biochemical and serological properties. Also genotypic characterization was studied for 16S rRNA, aroA and crp genes. Results: Growth pattern on different media differed among the used strains as the wild type and Δ aroA mutant were nearly similar while the Δ crp mutant strain was greatly differed. Biochemically the difference between the wild-type and Δ aroA mutant was inability of mutant strain to produce arginine dihydrase (ADH) and fermentation of saccharose. On the other hand the Δ crp mutant failed to produce ADH and to ferment any of the carbohydrates except glucose. A successful amplification of the 16S rRNA gene at 585 bp was detected with the all tested strains while was 1206 bp with only wild type and Δ crp mutant strain when aroA gene primers were used. Regarding crp genes, the amplified products was at 1029 bp with the wild and Δ aroA mutant but not with Δ crp mutant strains.
Conclusion:Findings of this study prove the use of methods based on molecular techniques like PCR to differentiate between different types of E. coli either wild or vaccinal mutant type strains. Also it may help in exclusion or proving the return back to virulence of the mutant vaccinal strains.
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