In the present study, the prevalence of antimicrobial-resistant chicken Escherichia coli strains and the resistance genes in E. coli was investigated. For this purpose, 1002 chicken E. coli strains isolated from layer and broiler flocks in Shaanxi, Henan and Gansu provinces in China during 2007-2012 were examined. Antimicrobial susceptibility of these E. coli strains against 18 antimicrobials was determined by the Kirby-Bauer disk diffusion method. Eight out of the twenty antimicrobial resistance genes were detected by polymerase chain reaction (PCR). The sequences of the resistance genes in chicken E. coli strains were compared with the previously published sequences. Our results revealed that the antimicrobial resistance prevalence of E. coli strains in western China to ampicillin, doxycycline, tetracycline and nalidixic acid were consistently kept at 62-100%. The E. coli resistance to nalidixic acid and ciprofloxacin had an increasing trend, as high as 100% for nalidixic acid while the resistance prevalence to gentamicin had a decreasing trend. The detection rates of the genes for tetA, tetB, blaTEM, and aac(3)-II in chicken E. coli strains were positively correlated with their antimicrobial resistance (P
