Characterization of Antimicrobial Resistance and Extended-Spectrum β-Lactamase Genes in Escherichia coli Isolated from Chickens

Abstract Extended-spectrum β-lactamase (ESBL)–producing Escherichia coli have been frequently isolated from food-producing animals and pose a serious threat to human health. This study collected 195 ESBL-producing E. coli isolates from 20 chicken farms and 3 live-bird markets located in Northeast China (Heilongjiang, Liaoning, Jilin) and Jiangsu province from February 2011 to October 2013. ESBL genes, including blaCTX-M, blaTEM, and blaSHV, were detected and characterized, and the susceptibilities of these strains to various antimicrobial agents were determined. One hundred ninety-one of these isolates carried 1 or more bla genes. blaCTX-M, blaTEM-1, and blaSHV-5 were identified in 183, 121, and 2 isolates, respectively. The most common blaCTX-M genes were blaCTX-M-15 (68 strains), blaCTX-M-65 (41 strains), blaCTX-M-55 (35 strains), blaCTX-M-14 (32 strains), followed by blaCTX-M-3, blaCTX-M-13, blaCTX-M-79, and blaCTX-M-101, as well as the chimeric genes blaCTX-M-64, blaCTX-M-123, and blaCTX-M-132. Fiftee...