الفهرس 
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Abstract
E. coli and Salmonella infections are responsible for great economic losses in the poultry industry worldwide, bringing serious threat to the poultry industry and considered to be two of the most important poultry diseases.
The present investigation aimed to prepare a potent vaccine from E. coli serogroups (O1, O2, O78) and Salmonella (S. Enteritidis , S. Typhphimurium) to control colibacillosis and Salmonellosis in chickens.
Firstly a total of E.coli and Salmonella isolates were collected from diseased chickens. All isolates were confirmed to be E.coli using API system, conventional method of identification and Serotyping of the isolates.
The extracted DNA from the E.coli strains were tested with PCR using primer pairs for stx1, stx2, eaeA, sth and hylA. Stx1 gene revealed negative reaction of 614 bp, stx2 revealed positive amplification 779 bp , Hlya and tsh gene revealed negative amplification of 620 bp, 165 bp, respectively and eaeA gene revealed positive amplification of 890 bp for O78 and negative amplification for O1 and O2
The extracted DNA from the Salmonella strains were tested with PCR using primer pairs for stn, pef, bcfc, sopB, invA and flic gene revealed positive amplification of 617 bp, 700 bp, 467 bp, 715 bp, 284 and 467 bp respectively except flic was negative for SE.
In the E.coli vaccine the Geometric mean titer (GMT) of micro-agglutination test against O1, O2 and O78 in vaccinated chicken reached to (49), (43) and (140) after the 3rd week from primary vaccination, respectively, and to (320), (211) and (184) after 3rd week from boostring dose, respectively. While in combined E. coli Salmonella vaccine, the GMT of micro-agglutination test against O1, O2 and O78 in vaccinated chicken reached to (70), (98) and (113) after 3rd week from primary vaccination, respectively, and to (299), (211) and (184) after 3rd week from boostring dose, respectively.
In the Salmonella vaccine the Geometric mean titer (GMT) of micro-agglutination test against S. Enteritidis and S. Typhimurium in vaccinated chicken reached to (49) and (106) after the 3rd week from primary vaccination, respectively, and to (149) and (211) after 3rd week from boostring dose, respectively. While in combined E. coli Salmonella vaccine, the GMT of micro-agglutination test against S. enteritidis and S. typhimurium in vaccinated chicken reached to (40) and (98) after the 3rd week from primary vaccination, respectively, and to (139) and (226) after 3rd week from boostring dose, respectively.
In the E.coli vaccine the ELISA antibodies titers against O1, O2 and O78 reached to (1380), (752) and (2689) after the 3rd week from primary vaccination, respectively, and to (4936), (1417) and (6620) after 3rd week from boostring dose, respectively. While in combined E. coli Salmonella vaccine, the ELISA antibodies titers against O1, O2 and O78 were reached to (1905), (1471) and (1193) after 3rd week from primary vaccination, respectively, and to (3851), (1843) and (6255) after 3rd week from boostring dose, respectively.
In the Salmonella vaccine the ELISA antibodies titers against S. Enteritidis and S. Typhimurium in vaccinated chicken were reached to (1642) and (3995) after the 3rd week from primary vaccination, respectively, and to (4695) and (5307) after 3rd week from boostring dose, respectively. While in combined E. coli Salmonella vaccine, the ELISA antibodies titers against S. Enteritidis and S. Typhimurium reached in vaccinated chicken to (1120) and (3072) after the 3rd week from primary vaccination, respectively, and to (3497) and (6255) after 3rd week from boostring dose, respectively.
The protective value against virulent E. coli and Salmonella strains were reached to (83.75%), (88.75) and (86.25%) in E. coli vaccine, Salmonella vaccine and combined E.coli Salmonella vaccine , respectively, compared with the control was reached to (48.75) post oral and intramuscular challenge.
Reisolation of E.coli O1, O2 and O78 organisms in challenged chickens vaccinated by E.coli vaccine and combined E.coli Salmonella vaccine were reached to (14%), (13%), (16%), (23%), (12.5%) and (13.4%) while in the control were reached to (62.5%), (80.5%) and (75%).
Reisolation of S. Enteritidis and S. Typhimurium organisms in challenged chickens vaccinated by Salmonella vaccine and combined E.coli Salmonella vaccine were reached to (16.2%), (8.8%), (6.7%) and (10.7%) while in the control were reached to (68.75%) and (64.3%).