الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
E.coli is one of the normal microflora of the intestinal tract of poultry, but certain strains possess specific virulence factors and are able to cause avian colibacillosis which is the most frequently reported poultry disease responsible for significant economic losses in poultry industry in many parts of the world. The goal of the current study was the detection of the most important virulence genes among EHEC isolates from broiler chickens. One hundred samples of broiler chickens (diseased birds) suffered from pericarditis, perihepatitis, and airsacculitis (liver and heart blood from each sample) were collected in Sharkia province. Bacteriological examination revealed that the prevalence of E.coli was (60%) from the collected samples. Out of 100 samples of examined fresh heart blood 39 were E.coli positive with an incidence 39%. Regarding examined liver samples, 100 samples were tested and E.coli were positive in 38 with a percentage of 38%. All samples were submitted for isolation and biochemical identification for E.coli. Hemolytic activity: No apparent hemolytic activity or discoloration is produced (gamma hemolysis).Serological identification of E.coli isolates revealed that E.coli strains were belong to 11 different serotypes which were identified as follows, untypeable predominant with 40% of the total isolates , Summary followed by O78 with 11.66%, O111: H4 with 8.33%, O26 : H11 with 6.67%, O1 : H7, O55 : H7, O127 : H6, O128 : H2 with 5% each, while all of the rest 4 identified serotypes had the same isolation rate
3.33% which were O2 : H6, O44 : H18, O119 : H4, O125 : H21. In the PCR screening of 15 E.coli strains for the presence of the stx gene, all strains was positive for stx1by percentage 100% and only 7 strains were positive for stx2 by percentage 46.7%, while the eaeA gene, only 5 strains were positive by percentage 33.3% and the hly gene, only 3 strains were positive by percentage 20%. The present study provides the information about the involvement of STEC in poultry. E.coli strains originating from birds are carrying a low percentage eaeA or hlyA genes.