الفهرس 
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Abstract
6. >Avian pathogenic E. coli infection is one of the bacterial diseases that cause economic losses in broilers, and continues to be one of the most important economic and systemic respiratory diseases in the economy, leading to higher morbidity and mortality.
Colibacillosis is characterized by the presence of E. coli and their toxins in the blood and colonized in organs including liver, spleen and heart.
The total number of E. coli recovered from the examined cases (250 broilers of 3-5 weeks old) was 98, and the incidence rate was 39.2%. Escherichia coli were mainly isolated from the intestine (32), heart (28), and air sac (20) and the incidence of liver (18) was 32.6%, 28.6%, 20.4%, and 18.4%, respectively.
In-vitro sensitivity tests on E. coli isolates were applied against 12 chemotherapeutic agents and the results showed that most E. coli isolates resistant to gentamicin (96.4%) and ampicillin (94.9%), followed by doxycycline (92.1%), ciprofloxacin (89.9%), amoxicillin + clavulanic acid (85.7%), cefotaxime (80%), lincomycin (79.6 %), amoxicillin (74.4%), streptomycin (69.3%) and tobramycin were resistant (60.9%). At the same time, they are sensitive to sulfamethoxazole + trimethoprim (68%), norfloxacin (72.4%).
Twenty-two strains (14 APEC, 8 AFEC) were examined for the presence of the 5 virulence genes; iutA, pic, KpsMTII, int1 and vat.
Using PCR to detect the int1, iutA,vat, KpsMTII and pic genes of fecal E. coli isolates showed that all the isolates detected were positive for int1, iutA and pic, seven isolates(87.5%) carried the vat gene and on the other hand were negative for the KpsMTII gene, while PCR testing of non-fecal E.coli isolates showed that all (14) isolates examined were positive for int1, iutA and pic (100%), 9 isolates (64.3%) carried the vat gene, and 14 Isolates (100%) KpsMTII gene negative.