الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
E. coli infection is one of the most serious problems that affect poultry industry causing high economical losses not only due to high mortality in young birds but also for the debilitating effect which predisposes for many other diseases. E. coli infections in birds cause many clinical manifestations which characterized by a respiratory disease which is frequently followed by a generalized infection which ended by death. So for solving this problem, this study was planned for bacteriological characterization of chicken E. coli isolates.
Regarding the bacteriological isolation and identification of E. coli, the colonial characteristics revealed that, Only 11 out of 17 apparently healthy samples, 17 out of 24 diseased samples and 14 out of 19 freshly dead samples were showed the typical characteristics of E. coli which were on Nutrient agar medium showed Rounded, non-pigmented colonies, while on MacConkey agar and salmonella Shigella agar media showed rounded, non mucoid pink colonies (lactose fermenter) and on Eosin Methylene blue (EMB) agar showed a distinctive yellow green metallic sheen.
The morphological characteristics revealed that 11 out of 17 apparently healthy samples, 17 out of 24 diseased samples and 14 out of 19 freshly dead samples were Gram negative, motile, non- sporulated, medium sized bacilli.
Depending on API 20E system for biochemical identification of E. coli the suspected E. coli isolates were 8 out of 11 apparently healthy samples, 14 out of 17 diseased samples and 11 out of 14 freshly dead samples representing recovery rates 73%, 82% and 79% respectively.
By using 4 polyvalent and 24 monovalent antisera, only a restricted number of serogroups O1, O2, O6, O78, and O126 have been recovered where 4 out of 8 apparently healthy isolates, 3 out of 14 diseased isolates and 2 out of 11 freshly dead isolates were identified as O1 representing a recovery rate of 27% while 2 out of 14 diseased isolates and 1 out of 11 freshly dead isolates were identified as O2 representing a recovery rate of 9%. On the other hand 2 out of 8 apparently healthy, 3 out of 14 diseased and 2 out of 11 freshly dead isolates were identified as O6 representing a recovery rate of 21%, while 2 out of 8 apparently healthy, 4 out of 14 diseased and 3 out of 11 freshly dead isolates were identified as O78 representing a recovery rate of 27%, finally 2 out of 14 diseased and 3 out of 11 freshly dead isolates were identified as O126 representing a recovery rate of 15%.The results of bacteriological isolation and identification E. coli were isolated in 33isolates out of 60 samples with recovery rate 55%.
Concerning the extracted genomic DNA of different isolated serogroups, the estimated size was more than 23Kb while the estimated size of extracted plasmids varied from 2-12 Kb.
Regarding to the PCR amplification of 4 different used genes, the 16s rRNA gene amplification using its specific primers, the PCR product of 204bp was obtained in all 5 serogroups.
As regards to stx gene amplification using its specific primers, the PCR product of 323bp was obtained only in O1, O2 and O78 serogroups which were enterohaemorrhagic E. coli.
As regards to STh gene amplification using its specific primers, the PCR product of 171bp was obtained only in O6 serogroup which was enterotoxigenic E. coli.
As regards to eaeA gene amplification using its specific primers, the PCR product of 200bp was obtained only in O126 serogroup which was enteroathogenic E. coli.
Concerning the SDS- PAGE protein patterns of different isolated serogroups, there are major protein clusters shared in all isolates and appeared at the molecular weights of 21 KDa, 30KDa, 56KDa and 74KDa and represented a high percent of total protein patterns of each serogroup. Also other common patterns present in most of the isolates obtained at the molecular weights of 26, 27, 32 and 85KDa. In addition there are minor proteins which related to each serogroup like that obtained at 24, 40, 60, 64, 67, 69, 78, 95 and 100 KD and represented a low percent of total protein patterns of each serogroup.