Journal of Global Antimicrobial Resistance (Dec 2023)

Characterization of quinolone resistance in Salmonella enterica serovar Typhimurium and its monophasic variants from food and patients in China

  • Xiaojuan Yang,
  • Shiyuan Yang,
  • Shengrong Liu,
  • Shuxiang Liu,
  • Jumei Zhang,
  • Weipeng Guo,
  • Juan Wang,
  • Zhongjian Song,
  • Liang Xue,
  • Moutong Chen,
  • Shi Wu,
  • Xianhu Wei,
  • Qingping Wu

Journal volume & issue
Vol. 35
pp. 216 – 222

Abstract

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ABSTRACT: Objectives: The study aimed to characterize the quinolone resistance of Salmonella enterica serovar Typhimurium and its monophasic variant (Salmonella enterica serovar 1,4,[5],12:i:-) isolated from food and patients in China. Methods: All of the isolates were assessed for quinolone susceptibility via the broth microdilution method. Then, the isolates were checked for mutations within quinolone resistance-determining regions of gyrA, gyrB, parC, and parE and were examined for plasmid-mediated quinolone resistance genes. Results: High rates of resistance to nalidixic acid in the S. Typhimurium (70.7%) and S. 1,4,[5],12:i:- (41.9%) isolates were observed, and a considerable proportion of isolates with reduced susceptibility to ciprofloxacin and levofloxacin were also detected. The high frequency of mutations in GyrA (60.8%) and a variety of genes (aac[6′]-Ib-cr [23.2%], oqxAB [19.2%], qnrS [13.6%], and qnrA [3.2%]) conferring quinolone resistance in these Salmonella isolates were noteworthy. Lastly, the isolates carrying qnrS for transferability and transmission of the quinolone resistance were analysed by conjugation. Multiple locus variable-number tandem repeat analysis profiles indicated that some qnrS-positive isolates were clonally related, whilst the other isolates were genetically divergent. This suggested that both clonal spread of resistant strains and horizontal transmission of the plasmid-mediated resistance genes contributed to the dissemination of qnrS-positive Salmonella isolates. Conclusion: This study highlights the prevalence of quinolone-resistant S. Typhimurium and S. 1,4,[5],12:i:- in China, posing a threat to public health.

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