| In recent years,antibiotics have been widely used in aquaculture,resulting in bacterial resistance and drug residues in fish and the environment,which is threatening human health.The harmful of drug-resistant bacteria is very serious.It not only directly affects the safety and hygiene of animal products,but also transfers drug-resistant bacteria to the human body through the food chain and then spreads the drug-resistant genes to the normal flora,resulting in the resistance of human pathogens to common antibacterial drugs.Drug resistance,so the problem of resistance to bacteria must be highly valued.Lactobacillus plantarum AJG 1-4 and Citrobacter freundii was used as the test bacteria and target bacteria,respectiviely.From the indicators of cell membrane permeability,ultraviolet absorbing substances,cell morphological characteristics and protein synthesis,initially explored the bacteriostatic mechanism of L.plantarum AJG1-4 on drug-resistant C.freundii and applied it to turbot meat The control of medium-resistant C.freundii provides a theoretical basis for controlling the problem of drug-resistant bacteria in aquatic products.The main findings were as follows:1.From the 80 strains of lactic acid bacteria(LAB)isolated from traditional fermented foods such as Jixi gaosun,pickled cucumber and pickled cabbage in Northeast China.Six strains of lactic acid bacteria with antibacterial activity against drug-resistant C.freundii were selected.According to scientific identification,strains AJG1-4,DLL-500,LJM1-4,and ZHG2-1 are L.plantarum,and strains DLH-12 and STM1-2 are Lactobacillus sake.2.Strain AJG1-4 with a strong inhibitory effect on drug-resistant C.freundii was re-screened from six strains LAB,and its inhibitory diameter reached 20.12 ± 0.75 mm.The cell-free supernatant was analyzed by p H,protease and heat treatment tests,and it was preliminarily determined that the antibacterial active substance in the crude extract of cell-free supernatant(CFS)AJG1-4 was bacteriocins.3.Antibacterial mechanism of strain AJG1-4 against drug-resistant C.freundii was preliminaryly analyzed in the study.The results showed that the cell membrane of drug-resistant C.freundii was changed by the CFS of strain AJG1-4.The permeability of the bacteria caused a significant increase in the conductivity of the bacterial solution,protein leakage and a large amount of nucleic acid substances;and the drug-resistant C.freundii treated with strain AJG1-4,the cell membrane of the bacterial cell was wrinkled and dissolved,The integrity of the cell is completely lost,and the overall structure of the cell collapses.4.A preliminary study on the inhibitory effect of strain AJG1-4 crude extract,strain AJG1-4 crude extract and ceftazidime on the drug-resistant C.freundii in turbot flesh was analyzed,and it was analyzed that the strain AJG1-4 crude extract The experimental group of turbot meat treated with crude extract,strain AJG1-4 crude extract and ceftazidime has a high sensory score,indicating that it can effectively control the growth and reproduction of bacteria and inhibit the drug-resistant Freund lemon in turbot meat.The increase in the number of Acidbacteria effectively delays the rise of p H and TVB-N in turbot meat,and the crude extract of strain AJG1-4 and ceftazidime have the best antibacterial effect on turbot fish meat.Various indicators show that the addition of strain AJG1-4 crude extract can effectively control the growth and reproduction of drug-resistant C.freundii in turbot,and the joint treatment of strain AJG1-4 and ceftazidime can effectively prolong the turbot Fish shelf life is at least 2d.It shows that the crude extract of strain AJG1-4 can increase the sensitivity of ceftazidime to drug-resistant C.freundii. |
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