Abstract
This work was designed to investigate incidence of P. aeruginosa in dead in shell chicken embryos and molecular detection of virulence genes and study their pathogenicity effect on embryonated chicken eggs and chicks. Out of 100 pooled samples were collected from liver, heart and yolk sac of dead in shell chicken embryos, a total of 24 (24%) P. aeruginosa isolates were isolated.On carrying PCR test for 24 P. aeruginosa isolates there were high distribution of (opr L) and ( lasI ) genes with 100% while distribution of other virulence genes was as follows: toxA (83.3%), lasR (75%), Rhl1 (70.8%). Pathogenicity of P. aeruginosa on embryonated chicken eggs was studied either by inoculation of P. aeruginosa strain via yolk sac route in a dose of 0.1 ml suspension 14x10⁷. Which gave 100% embryonic mortalities after 3 days or by dipping group of 17 days –old embryonated chicken eggs in a dose of 6.1X 109 /ml which gave 90% embryonic mortality. Experimentaly infected chicks showed 70% mortality. Histopathological changes in dead embryos from infected embryonated eggs and sacrificed, dead infected chicks revealed lymphocytic hepatitis with presence of gram negative bacteria. Lymphocytic nephritis with hemosiderosis found in renal parenchyma. Heart showed lymphocytic myocarditis. Lung showed alveolar emphysema, interstitial pneumonia and perivascular fibrosis. P. aeruginosa was re-isolated from internal organs of sacrificed hatched chicks and from liver and yolk sac of dead embryos.

Key words: P. aeruginosa, Chicken embryo, PCR, virulence genes, Histopathology