title: 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. Fifteen strains (7.7%) co-harboring CTX-M-1 group and CTX-M-9 group genes were detected in 195 ESBL-producing strains. Pulsed-field gel electrophoresis of 45 strains showed that these CTX-M-producing isolates belonged to 34 different types. To our knowledge, this is the first study to report the blaSHV-5 gene in E. coli isolated from chickens in China. Conjugation experiments demonstrated that the blaCTX-M and blaTEM genes could be transferred to E. coli strain J53, while conjugative transfer of the blaSHV-5 gene from two isolates was not detectable. blaCTX-M genes are carried by many kinds of transferable and untypable plasmids. Our findings demonstrate that the CTX-M enzymes are predominant in both type and quantity.
authors.affiliation: 1 College of Veterinary Medicine, Jilin University , Changchun, China .
authors.forename: Panpan
authors.initials: P
authors.lastname: Tong
authors.forename: Yang
authors.initials: Y
authors.lastname: Sun
authors.forename: Xue
authors.initials: X
authors.lastname: Ji
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Du
authors.forename: Xuejun
authors.initials: X
authors.lastname: Guo
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Lingwei
authors.initials: L
authors.lastname: Zhu
authors.forename: Bo
authors.initials: B
authors.lastname: Zhou
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
authors.forename: Guo
authors.initials: G
authors.lastname: Liu
authors.forename: Shuzhang
authors.initials: S
authors.lastname: Feng
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002645:Chickens / Q000382:microbiology*; D002681:China; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000662:veterinary*; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001618:beta-Lactamases