猪源致病性大肠杆菌blaCTX-M-123基因的传播特性和适应性代价研究

doi:10.16431/j.cnki.1671-7236.2025.06.040

摘要/Abstract

摘要： 【目的】阐明猪源大肠杆菌中bla_CTX-M-123基因的位置，同时探究其携带的移动遗传元件的传播能力与适应性代价。【方法】通过化学转化试验评估bla_CTX-M-123基因的种内转移能力，并利用全基因组测序确定bla_CTX-M-123基因的位置，分析大肠杆菌中bla_CTX-M-123基因的遗传环境；使用微量肉汤稀释法测定大肠杆菌911菌株、大肠杆菌DH5α感受态细胞及转化子的最小抑菌浓度(minimum inhibitory concentration，MIC)。此外，通过竞争试验评估携带bla_CTX-M-123基因质粒的适应性代价，并使用大蜡螟感染模型进行致病性评价。【结果】通过转化试验得到了1株转化子DH5α-pL1，其对头孢噻呋的MIC值为256 μg/mL，生长速率高于受体菌大肠杆菌DH5α感受态细胞，但低于野生型菌株911。DH5α-pL1在培养7 d后，质粒留存率逐渐下降，培养24 h后表现出一定的适应性代价，相对竞争指数＜1。致病性试验结果显示，对照组及大肠杆菌DH5α感受态细胞组大蜡螟幼虫存活率为100%；注射菌株911和DH5α-pL1 120 h后，幼虫存活率分别为50%和70%。【结论】携带bla_CTX-M-123基因的质粒可在种内转移并介导转化子耐药，且该质粒的稳定性弱，具有一定的适应性代价。此外，携带bla_CTX-M-123基因的质粒具有增强受体菌致病力的作用，增加了感染的几率和治疗难度。研究结果为细菌的耐药机制研究和防控提供理论依据。

关键词: 大肠杆菌; bla_CTX-M-123基因; 转化试验; 适应性代价; 致病性

Abstract: 【Objective】 The purpose of this experiment was to elucidate the location of bla_CTX-M-123 gene in porcine Escherichia coli,and to explore the transmission capacity and fitness cost of the mobile genetic elements carried by bla_CTX-M-123 gene.【Method】 The intraspecific transfer ability of bla_CTX-M-123 gene was evaluated by chemical transformation test,the location of bla_CTX-M-123 gene was determined by whole genome sequencing,and the genetic environment of bla_CTX-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 bla_CTX-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 bla_CTX-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 bla_CTX-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; bla_CTX-M-123 gene; transformation experiment; fitness cost; pathogenicity

中图分类号:

S852.61

李琼, 胡紫微, 金钢铸, 陈峥, 刘伟成, 韩生义, 许春燕. 猪源致病性大肠杆菌bla_CTX-M-123基因的传播特性和适应性代价研究[J]. 中国畜牧兽医, 2025, 52(6): 2884-2892.

LI Qiong, HU Ziwei, JIN Gangzhu, CHEN Zheng, LIU Weicheng, HAN Shengyi, XU Chunyan. Study on the Transmission Characteristics and Fitness Cost of bla_CTX-M-123 Gene in Pathogenic Escherichia coli from Swine[J]. China Animal Husbandry & Veterinary Medicine, 2025, 52(6): 2884-2892.

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