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Abstract
A monitoring study was carried out on one hundred and two broiler flocks located in nine Egyptian governorates during the period of 2012 - 2014 in a trial for isolation of responsible aerobic bacterial agents causing high chicks mortality in such flocks. The highest mortality percent was recorded in Cobb breed on the 12th day of age in Beni-Suef while the lowest mortality percent recorded in Sasso breed on the 25th day of age in Sharkia. Bacteriological investigation revealed that the Escherichia coli isolates were the predominant organism (42.9%) followed by Salmonella (21.7%) Klebsiella pneumonia(10.1%), Proteus mirabilis(6.2%) and Pseudomonas aeruginosa (4.5%). Serological identification of E. coli isolates revealed that both O158 and O78 serogroups were the most predominant isolates (18.6%) each, followed by serogroups O27(10.8%), O26 (6.8%), O18 and O55(3.9%), each, O6, O111 and O159 (2.9%), each, finally serogroup O1, O8, O15, O44, O114, O119, O142, O153, O166 and O169 (1.5%), each while un-typable strains were (13.7%). Salmonella serological identification revealed that Salmonella Infantis (SI) was the most predominant isolates (27.2%) followed by Salmonella Virchow (SV) (23.4%), Salmonella Enteritidis (SE)( 20.8%), Salmonella Gallinarum (SG) (14.3%), Salmonella Kentucky (SK) (10.4%) and Salmonella Typhimurium (ST) (3.9%). In vitro testing of the phenotypic properties of the 204 E. coli isolates, it was found that all tested isolates were Congo red positive. Conventional and a real-time PCR assay were used for the detection of rfbS, flijB, fliC, stmm and sefA genes of SG, SI, SK, ST and SE respectively where they sequenced and submitted on gene bank with accession numbers KP730600, KP760484, KP760485, KP763723 and KP793717