الفهرس 
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Abstract
6. Avian Pathogenic Escherichia coli (APEC) is the cause of Poultry colibacillosis which responsible for several extra-intestinal pathological conditions, leading to serious economic damage in poultry production . colibacillosis characterized by the presence of E. coli in the blood and colonizationof the E. coli organism in organs including the heart, liver and spleen. In this work:-
A total of E. coli recovered from examined cases (297 broiler chickens of 3-5weeks ages) was 98 with an incidence of 33%. E. coli was isolated mainly from liver (31), kidney (18), air sacs (20) and pericardial sac (29) with an incidence of 31.6%, 18.4%, 20.4% and 29.6%, respectively.
All the tested isolates of E.coli showed multi drug resistance (MDR) pattern. The tested isolates of E.coli were tested against 12 of antibiotic disk.
By using PCR 100% of the studied isolates of E. coli were found positive for ampC gene, 93.3% for TetA(A) gene , 93.3% for blaSHV gene and100% for blaCTX gene.
To detect the proteolytic action of E. coli Out of 43 E. coli isolates (43.9%) were able to digest casein and 16 E. coli isolates were positive for Gelatin liquefaction test (16.3%).
using PCR to determine the prevalence of pic , vat and tsh genes encoding serine protease autotransporter toxins (SPATEs) in a collection of E. coli isolates, 15 isolates were positive for pic and vat genes (100%) and 12 isolates (80%) harbored tsh gene.
The prevalence of viral pathogens with special focus on AIV and IBV was investigated in broiler chickens suffering coliseptesemia. Viruses prevalence was determined using RT-PCR the prevalence of IBV is 80% but not present any infection with AIV.