Preparation of Reference Strain for β-Lactam Antibiotic Resistance Mechanism Detection
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(1.College of Food Science and Engineering, Northwest A & F University, Yangling 712100, Shaanxi;2.Market Supervision and Administration Bureau of Hantai District of Hanzhong, Hanzhong 723000, Shaanxi;3.Chinese Academy of Inspection and Quarantine, Beijing 100176;4.Hebei Food Inspection and Research Institute, Hebei Food Safety Key Laboratory, Shijiazhuang 050000;5.National Institutes for Food and Drug Control, Beijing 100050)

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    Abstract:

    Objective: In order to quickly detect the mechanism of β-lactam antibiotic resistance carried by food-borne pathogens in a series of foods, the qualitative standard samples of Salmonella reference strain carrying β-lactam antibiotic resistance coding genes were developed. It will provide the technical support of strong traceability, high evaluation accuracy and be conductive to widely carry out the detection of drug-resistant microorganisms among various testing institutions. Methods: Salmonella isolated previously and stored at -80 ℃ were subcultured on LB agar plate. 3 Salmonella representatives were selected and the encoding genes of β-lactam antibiotic resistance carried by the 3 strains were verified via PCR amplification, DNA sequencing and BLAST. The genetic stability of the target genes was simultaneously identified. The standard samples of the reference strain with live bacteria amount of 106~107 CFU/vial were prepared by vacuum freeze-drying technique. On the basis of GB/T 15000.3-2008, the three reference strains were tested for homogeneity, the results were statistically analyzed via F test to evaluate their uniformity. The prepared reference strains were stored at 37 ℃, 4 ℃ and -80 ℃ simulated, respectively, to test their transport stability and storage stability. Seven laboratories with checkout qualifications were commissioned to jointly evaluate the reference strains' characteristic values. Results: The β-lactam antibiotic resistance mechanism associated encoding genes of blaCTX-M-55/ blaTEM-1 in one Salmonella, of blaTEM-1/blaOXA-1/blaCTX-M-l5 in one Salmonella, and of blaCTX-M-3 in one Salmonella can stably inherit in 15 generations. The homogeneity of the prepared reference strains meets the necessary requirements. When stored at 37 ℃ for 13 d, 4 ℃ for 90 d and -80 for 360 d, the viable bacteria amount was basically stable and above ×104 CFU/ vial. The characteristic values of the reference strains were consistent with 7 laboratories' and indicated that the prepared strains could be used as the standard samples. Conclusions: In accordance with the standard sample preparation standards and specifications, three reference strains carrying β-lactam antibiotic resistance encoding genes were developed. They meet the requirements of standard samples and can be used for rapid detection of β-lactam antibiotic resistance mechanism of food-borne bacterial.

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  • Received:December 19,2021
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  • Online: January 09,2023
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