Increasing prevalence of extended-spectrum cephalosporin-resistant Escherichia coli in food animals and the diversity of CTX-M genotypes during 2003-2012

Lili Rao, Luchao Lv, Zhenling Zeng, Sheng Chen, Dandan He, Xiaojie Chen, Congming Wu, Yang Wang, Tong Yang, Peng Wu, Yahong Liu, Jian Hua Liu

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78 Citations (Scopus)


The aim of this study was to investigate the trends and the diversity of CTX-M types of extended-spectrum β-lactamase (ESBL) in Escherichia coli isolated from food animals in China over a ten-year period. From 2003 to 2012, 2815 E. coli isolates collected from diseased animals (chickens, pigs, and waterfowl) were screened for the prevalence of CTX-M genes. CTX-M-positive isolates were tested for their susceptibilities to 10 antimicrobial agents and the clonal relationship of CTX-M-producing E. coli isolates was also assessed. Overall, 677 (20.1%) of the 2815 E. coli isolates carried CTX-M genes. Eighteen different types of CTX-M ESBLs were identified, with CTX-M-14, CTX-M-55, and CTX-M-65 being the most dominant genotypes. The occurrence of CTX-M-producing E. coli increased significantly from 5.7% in 2003-2005 to 35.3% in 2009-2012 (p< 0.0001). High genetic heterogeneities were observed in the CTX-M-producing E. coli isolates. Most CTX-M-producing strains were also resistant to other classes of antimicrobials. Compared to isolates carrying CTX-M-9 subgroup of ESBLs, isolates carrying CTX-M-1 subgroup ESBLs showed significantly higher resistance rates to ceftazidime, amikacin, and fosfomycin (p< 0.01). The study reported the dramatic increase of CTX-M ESBLs in E. coli isolated from animals overtime in China. The increasing incidence of CTX-M-55 with high hydrolytic activity against ceftazidime and the widely spread co-resistance in CTX-M-producing isolates alarm the serious antimicrobial resistance situation in China and highlight the need for urgent control strategies to limit the dissemination of those resistant genes in China.
Original languageEnglish
Pages (from-to)534-541
Number of pages8
JournalVeterinary Microbiology
Issue number3-4
Publication statusPublished - 27 Aug 2014


  • Animal reservoirs
  • CTX-M
  • Escherichia coli
  • Food animals
  • Fosfomycin

ASJC Scopus subject areas

  • Microbiology
  • veterinary(all)

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