In this study, to know about the phylogeny of Escherichia coli isolated from broilers with collibacillosis in
Tabriz, 70 E. coli isolates recovered from broilers with collibacillosis were characterized for phylogenetic
group (A, B1, B2, D) by multiplex PCR. Of the all 70 samples, 35 (50%) isolates were classified as type A,
32 (45%) as type D, 2 (2.8%) as type B1 and 1 (2.8%) as type B2. This study demonstrates the high
prevalence of E. coli types A and D in infected broilers. This shows that the collibacilosis-causing E. coli
bacteria are typical commensals, type A alongside pathogenic type, D in Iran. It is possible that this type of
E. coli could acquire virulence genes from pathogenic types. Of course, such a claim needs further study.