الفهرس 
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Abstract
Salmonella enterica is a prominent cause of salmonellosis throughout the world, that can infect chicken causing serious illness in human through consumption of contaminated food products as there are more than 2800 serotypes that can infect chicken. In the present study of salmonella infection at Damietta Governate was screened on 180 chicken samples at January 2016 and the results were summarized as the follows:)1(-Seventeeth (9.4%) out of 180 samples from ill-chicken were positive for Salmonella enterica. 2(-S. Typhimurium and S. Kentucky were the most common serotypes (4, 23.52% each), followed by S. Enteritidis (3, 17.6%), S. Labadi (2, 11.8%), S. Larochelle, S. Tamale, S. Takoradi and S. Papuana (1, 5.9% each)3(- Concerning the occurrence of Salmonella enterica in ill-chicken viscera, it was clear that liver (41.2%) was the most site of isolation followed by yolk sac (23.5%) then, spleen and heart (17.6% each). 4(-The antimicrobial resistance testing showed higher resistance rates to tetracycline (94.11%), penicillin (94.11%), erythromycin (94.11%), doxycycline (88.23%), streptomycin (88.23%) and nalidixic acid (82.35%). On the contrary, lower rates of resistance were observed for ceftriaxone, ciprofloxacin, cephalothin (5.88%, each), norfloxacin, amoxicillin-clavulonic acid (11.76%), cefotaxime (17.64%) and gentamicin (23.52%).)5(- A number of antimicrobial resistance genes including [ blaTEM , blaCTX ,tetA(A) and ere(A)] in the most common Salmonella enterica serovars (S. Typhimurium,S. Enteritidis and S. Kentucky) were determined on plasmids and chromosomal DNA of five isolates using PCR. The blaTEM genes, that responsible for the extended spectrum β-lactamase phenotype, were present on plasmids and bacterial chromosome of all examined isolates of S.enterica. Moreover, one isolate harboring the blaTEM gene also contained blaCTX on plasmid only. Also, tet(A) and ere(A) genes were identified in all tested Salmonella isolates on plasmids and bacterial chromosome. This investigation indicated the importance of plasmid in spreading of antimicrobial resistance.