Evaluation of Antibiotic Resistance in Escherichia coli Isolates Obtained from Broiler Chicken Flocks at Young Ages in Kermanshah Province

Introduction: The widespread use of antibiotics for growth promotion or therapeutic purposes in poultry farming has led to increased antibiotic resistance. Escherichia coli is one of the gastrointestinal bacteria capable of transferring resistance genes and causing antibiotic resistance in humans and poultry. Evaluating antibiotic resistance in poultry flocks can provide researchers with a clear picture of the health status of poultry flocks and the human community. Methods: This study was conducted on 60 broiler chicken flocks aged 1 to 28 days. These flocks had no history of antibiotic use. In the laboratory, after necropsy, sampling was carried out from five chicken pieces in each flock. After confirming the diagnosis and purification of E. coli using biochemical methods, antibiotic sensitivity testing against 19 antibiotics was performed using the disc diffusion method, following the CLSI guidelines. Results: Out of 300 samples collected, 270 (90%) isolates of E. coli were obtained. In this study, the sensitivity of antibiotics was as follows: fosfomycin (100%), lincomycin (94.81%), neomycin (48.52%), amoxicillin (48.15%), norfloxacin (41.48%), thiamphenicol (38.52%), enrofloxacin (38.52%), sulfamethoxazole (36.66%), florfenicol (31.85%), tilmycosin (31.85%), danofloxacin (30%), flumequine (25.19%), difloxacin (21.85%), chlortetracycline (16.66%), trimethoprim (16.66%), doxycycline (11.85%), erythromycin (10%), tylosin (1.48%), and colistin (0%). Additionally, resistance was observed only against tylosin (91.85%). No multiple resistance was observed among the isolated strains, and at least sensitivity to two antibiotics was detected in all samples. Conclusion: The findings of this research indicate that the level of antibiotic resistance in broiler chicken flocks at young ages in the Kermanshah region is low. However, the sensitivity rate to 17 antibiotics is less than 50%, demonstrating a relatively high level of sensitivity in poultry at these ages.