Multiple transmissible genes encoding fluoroquinolone and third-generation cephalosporin resistance co-located in non-typhoidal Salmonella isolated from food-producing animals in China

Hong Xia Jiang, Li Song, Ji Liu, Xiao Hua Zhang, Yan Na Ren, Wen Hui Zhang, Jing Yuan Zhang, Ya Hong Liu, Mark A. Webber, David O. Ogbolu, Zhen Ling Zeng, Laura J.V. Piddock

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The aim of this study was to identify genes conferring resistance to fluoroquinolones and extended-spectrum β-lactams in non-typhoidal Salmonella (NTS) from food-producing animals in China. In total, 31 non-duplicate NTS were obtained from food-producing animals that were sick. Isolates were identified and serotyped and the genetic relatedness of the isolates was determined by pulsed-field gel electrophoresis of XbaI-digested chromosomal DNA. Antimicrobial susceptibility was determined using Clinical and Laboratory Standards Institute methodology. The presence of extended-spectrum β-lactamase (ESBL) and fluoroquinolone resistance genes was established by PCR and sequencing. Genes encoded on transmissible elements were identified by conjugation and transformation. Plasmids were typed by PCR-based replicon typing. The occurrence and diversity of numerous different transmissible genes conferring fluoroquinolone resistance [qnrA, qnrD, oqxA and aac(6′)-Ib-cr] and ESBLs (CTX-M-27 and CTX-M-14), and which co-resided in different isolates and serovars of Salmonella, were much higher than in European countries. Furthermore, different plasmids encoded fluoroquinolone resistance (ca. 6 kb) and β-lactam resistance (ca. 63 kb) and these co-resided in isolates with mutations in topoisomerase genes (gyrA and parC) giving very resistant Salmonella. The presence of multidrug-resistant bacteria in food-producing animals in countries that export foodstuffs suggests that global transfer of antibiotic resistances from country to country on food is possible.

Original languageEnglish
Pages (from-to)242-247
Number of pages6
JournalInternational Journal of Antimicrobial Agents
Issue number3
Early online date17 Dec 2013
Publication statusPublished - 1 Mar 2014
Externally publishedYes


  • ESBL
  • Fluoroquinolone
  • Plasmid
  • Salmonella

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