Characterization of antimicrobial resistance and extended-spectrum β-lactamase genes in Escherichia coli isolated from chickens

Foodborne Pathog Dis. 2015 Apr;12(4):345-52. doi: 10.1089/fpd.2014.1857. Epub 2015 Mar 18.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • Chickens / microbiology*
  • China
  • Drug Resistance, Bacterial*
  • Electrophoresis, Gel, Pulsed-Field
  • Escherichia coli / drug effects
  • Escherichia coli / genetics
  • Escherichia coli / isolation & purification*
  • Escherichia coli Infections / veterinary*
  • Gene Transfer, Horizontal
  • Genes, Bacterial
  • Microbial Sensitivity Tests
  • Plasmids
  • beta-Lactamases / classification
  • beta-Lactamases / genetics*

Substances

  • Anti-Bacterial Agents
  • beta-Lactamases