Colibacillosis is a septicemic illness that affects poultry economically and usually results in numerous lesions in broiler chicken flocks. Previously published studies revealed increased E. coli resistance against a wide range of clinically used antimicrobials. This study was carried out to isolate and identify E. coli isolated from diseased broiler chicken farms and markets in Ismailia governorate, detect that E. coli isolates susceptibility to commonly utilized antibiotics, such as tetracycline, , ampicillin, amoxicillin, gentamicin, streptomycin, colistin,  and co-trimoxazole, etc. as well as detect the aminoglycosides resistant genes aacC (Aminoglycoside acetyltransferase)  and Aada2  (Aminoglycoside adenyltransferases)  by PCR in E. coli-resistant isolates.
From 70 diseased broilers chicken farms (5-7 birds/farm) aged (4-38 days) were received at the Reference Laboratory for Veterinary Quality Control on Poultry Production (RLQP) - Ismailia branch during the period from September 2019 to October 2022  and 70 chicken meat samples collected from Ismailia markets. The collected samples subjected to various examinations including isolation, phenotypic identification, antimicrobial drugs susceptibility and resistance assessments, and the aminoglycosides resistant genes aacC and Aada2 identification by PCR.
Results: Showed that E. coli was isolated and phenotypically recognized from 12 out of 70 diseased broiler chicken farms with a per cent ratio of 17.14 % and from 8 out of 70 chicken breast meat samples collected from markets in Ismailia with a per cent ratio of 11.43 %. All of the isolates showed multidrug resistance and antimicrobial resistance genes aacC and Aada2 genes were recorded in 13 out of 15 and 14 out of 15 of isolated phenotypically recognized E. coli isolates with a per cent ratio of 93.33% and 87.67%, respectively. Both aacC and Aada2 genes were Aminoglycoside resistance genes against gentamicin and streptomycin, respectively.
Conclusion: Broiler chicken may constitute an important source of multi antimicrobial drugs resistant E. coli, which can be considered a potential threat to public health through the transmission of resistant bacteria via the food chain.