Objectives:Colibacilosis is one of the most important diseases in poultry from the economic point of view, and it is also dangerous in terms of public health. Antibiotic treatment is the most important matter in dealing with the treatment and control of this disease. Checking the antibiotic resistance status both in genotype and phenotype before choosing an antibiotic drug in the region is essential. This study conducted to evaluate tetracycline resistance phenotype and genotype of E.coli isolates. Material and methods:In this study 44 strains of Escherichia coli were isolated from broiler chickens of Urmia city and their sensitivity to five antibiotics disk, including Enrofloxacin, Sulfadiazine, Florfenicol, Neomycin, Oxytetracycline were assessed. Polymerase chain reactions were used to identify tetA genes.Results and conclusion:Antibiogram test results showed that 35 isolates were resistant to Oxytetracycline as Tetracycline antibiotics. The Resistance rate for each antibiotic was for Sulfadiazine 45.5%, Enrofloxacin 6.8%, Oxytetracycline 79.5%, Florfenicol 13.7% and Neomycin 0%. In this study tetA gene were detected in 21 isolates from total 44 isolates of Escherichia coli. The results showed that 14 isolates were shown resistance in antibiogram test but didn’t have tetAgene. This result could indicate the potential effect of other Tetracycline resistance genes that caused resistance and showed in antibiogram test.The results showed that the resistance rate of isolates to Tetracycline was high. Tetracycline resistance gene (tetA) is widely distributed in E.coli isolates of the region and is the main resistance mechanism to tetracycline.

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