China Animal Husbandry & Veterinary Medicine ›› 2025, Vol. 52 ›› Issue (6): 2884-2892.doi: 10.16431/j.cnki.1671-7236.2025.06.040

• Basic Veterinary Medicine • Previous Articles     Next Articles

Study on the Transmission Characteristics and Fitness Cost of blaCTX-M-123 Gene in Pathogenic Escherichia coli from Swine

LI Qiong1, HU Ziwei1, JIN Gangzhu1, CHEN Zheng1, LIU Weicheng1, HAN Shengyi2, XU Chunyan1   

  1. 1. Ministry of Agriculture and Rural Affairs Key Laboratory of Quality and Safety Control of Poultry Products, Ministry of Education Key Laboratory for Animal Pathogens and Biosafety, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, China;
    2. Academy of Animal Science and Veterinary, Qinghai University, Xining 810003, China
  • Received:2024-09-13 Published:2025-05-27

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Abstract: 【Objective】 The purpose of this experiment was to elucidate the location of blaCTX-M-123 gene in porcine Escherichia coli,and to explore the transmission capacity and fitness cost of the mobile genetic elements carried by blaCTX-M-123 gene.【Method】 The intraspecific transfer ability of blaCTX-M-123 gene was evaluated by chemical transformation test,the location of blaCTX-M-123 gene was determined by whole genome sequencing,and the genetic environment of blaCTX-M-123 gene in Escherichia coli was analyzed.The minimum inhibitory concentration (MIC) of Escherichia coli 911 strain,Escherichia coli DH5α competent cells and inverters was determined by broth microdilution method.In addition,competition experiments were conducted to assess the fitness cost of the plasmid carrying blaCTX-M-123 gene,and the Galleria mellonella infection model was used for pathogenicity evaluation. 【Result】 One transformant,DH5α-pL1,was obtained through the transformation experiment,and its MIC value against ceftiofur was 256 mg/mL.The growth rate of DH5α-pL1 was higher than that of the recipient Escherichia coli DH5α competent cells,but lower than that of the wild-type strain 911.After 7 days of culture,the plasmid retention rate of DH5α-pL1 gradually declined,and after 24 h,the plasmid retention rate showed a certain fitness cost,with the relative competition index less than 1.The results of pathogenicity test showed that the survival rate of larval of Galleria mellonella was 100% in control and Escherichia coli DH5α competent cells groups.After 120 h injection of strains 911 and DH5α-pL1,the survival rate was 50% and 70%,respectively.【Conclusion】 The plasmid carrying blaCTX-M-123gene could be transferred intra-specifically and mediate drug resistance of the transformer,and the plasmid had weak stability and a certain fitness cost.In addition,the plasmid carrying blaCTX-M-123 gene had the effect of enhancing the virulence of the recipient bacteria,increasing the probability of infection and the difficulty of treatment.The results provided a theoretical basis for the study of drug resistance mechanism and prevention and control of bacteria.

Key words: Escherichia coli; blaCTX-M-123 gene; transformation experiment; fitness cost; pathogenicity

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