phylogenetic group determination of escherichia coli isolated from broilers and layers with colibacillosis

colibacillosis is of the most common infectious bacterial diseases of poultry.a total of 170 escherichia coli isolates obtained from broiler and layer flocks implicated with colibacillosis between 2011 and 2014 were subjected to phylogenetic analysis. among 150 e. coli isolates from typical lesions of local and systemic colibacillosis, 54 (31.8%), 37 (21.7%), 36 (21.2%) and 43 (25.3%) isolates determined as belonged to groups a, b1, b2 and d, respectively. the distribution of phylogenetic types for 20 isolates, obtained from apparently healthy birds as controls, were 9 (45%), 5 (25%), 1 (5%) and 5 (25%) for a, b1, b2 and d, respectively. overall, the phylogenetic determination revealed the b2 groups as predominant isolates in diseased birds, whereas the a group was apparently predominant in healthy birds. results of this study represent genotypic diversity among different manifestations of avian colibacillosis.