الفهرس 
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Abstract
A survey of Salmonella infection was carried out on broiler chickens at Dakahlia Governorate. Isolated serovars were studied for their pathogenicity in 7day old chicks and for their sensitivity to different chemotherapeutic agents. A comparison was carried out between conventional technique and PCR for detection of salmonellae. Results indicated that incidence of salmonellosis was 12% with the highest rate during summer season (36%) and at third and fourth week of age (34.04% and 15% respectively). The highest Salmonella recovery was from small intestine, gall bladder and spleen (6% each) while no recovery from kidney. The isolated serovars were S. Enteritidis (25%), S. Arizonae (20.83%), S. Bristol, S. Boecker and S. lomita (12.5% each) and S. Typhimurium and S. Rubislaw (8.33% each). The Pathogenicity of the isolated serovars in chicks revealed that mortality and recovery rates were higher in chicks infected with S. Enteritidis than other serovars. The highest recovery rate was from lungs (16%) followed by caecum, small intestine, liver and spleen (8% each), but it was only 2% from kidneys. PCR detected salmonellae in 73.33% of the experimentally infected chicks, in which S. Enteritidis represented 66.67%. Furthermore PCR detected salmonellae in spleen, caecum and liver of infected chicks at rate of 73%, 20% and 6.67% respectively. Results showed that PCR was more rapid and sensitive than conventional technique, but it failed to detect salmonellae in some samples that were detected by conventional technique. Sensitivity of salmonellae was recorded to some chemotherapeutic agents such as colistin sulphate, cephradine and chloramphenicol but it showed resistance to others as ampicillin and amoxycillin.