Study On Salmonella Contamination In Raw Meat Products And Drug Resistance Of Representative Strains In Some Areas Of Yunnan Province

Foodborne pathogens are important factors that cause food safety accidents.In this study,fresh meat products(mainly fresh pork and fresh chicken)from Yunnan were selected as the research object,and 164 samples were collected from Kunming,Qujing,Dali and Dehong of Yunnan to analyze their contamination conditions and explore the resistance mechanism of representative strain SM-112 to sulfonamides antibiotics.In this study,the following research methods were used: National standard method of bacterial isolation combined with stroma-assisted laser analytic time-of-flight mass spectrometry(MALDI-TOF MS)was used to isolate and identify Salmonella.Molecular typing of Salmonella was performed by pulsed field gel electrophoresis(PFGE),and the contamination source of salmonella was traced by clustering analysis of its gene map.The microbroth dilution method was used to analyze the sensitivity of 14 antibiotics.The suicide plasmid p CVD442 Gm mediated homologous recombinant gene editing technology was used to knock out the sul2 gene,and the influence of sul2 gene on the drug resistance of salmonella was explored and verified by the methods of drug sensitivity verification and cell verification.This study provides a theoretical basis for the risk assessment of foodborne pathogens in fresh meat products in Yunnan Province,and also provides a data reference for the clinical treatment of salmonella disease research progress.The main research results are as follows:(1)Salmonella contamination: A total of 19 strains of Salmonella were detected in 12 samples of 164 samples,the total detection rate was 7.32%(12/164),the detection rate of Salmonella in fresh pork samples was 7.27%(4/55),and the detection rate of Salmonella in fresh chicken samples was 14.29%(7/49).The detection rate of Salmonella in slaughter line samples was 1.67%(1/60).(2)PFGE classification and cluster analysis of Salmonella: Salmonella in raw meat had regional aggregation,but no regional cross contamination.(3)Drug susceptibility test of Salmonella: The drug resistance rate of Salmonella isolated from raw meat reached 89.47%,and all were multi-drug resistant,among which SM-112 was resistant to 12 kinds of antibiotics,SM-148 and SM-013 were resistant to 10 kinds of antibiotics respectively,and the drug resistance situation was relatively serious.(4)sul2 gene knockout: Precise 816 bp deletion of SM/ Δ sul2 was successfully obtained by homologous recombinant gene knockout technique mediated by suicide plasmid p CVD442 Gm,and the knockout rate was 100%,which made sul2 gene function ineffective.(5)Verification: Through the K-B disk drug sensitivity method,the drug inhibition zone size was expanded from 23.33 mm to 35.33 mm,and the drug resistance of the gene deletion strain SM/Δsul2 to SXT was significantly reduced.Through the cell verification experiment,the apoptosis rate of the gene deletion strain SM/ Δ sul2 on the cells was significantly decreased under the premise of the intervention of SXT,and the sulfonamine-resistant salmonella was successfully reversed into the sulfonamine-sensitive Salmonella.In conclusion,Salmonella is one of the main contaminating foodborne pathogens in raw meat products,and its drug resistance is multi-drug resistance,and the resistance is serious.At the same time,the sensitivity of the strain to sulfanilamide antibiotics increased significantly after the knockout of sul2 gene verification.After the addition of SXT,sul2-gene deletion strains significantly decreased the apoptosis rate of cells,indicating that sul2 gene plays a certain role in the mechanism of bacterial resistance to sulfonamides.In this study,a systematic investigation of salmonella contamination in fresh meat products in Yunnan region was obtained,which provided a certain scientific basis for understanding the contamination of meat products in Yunnan province and the traceability,prevention and control of food-borne diseases,and had practical guiding significance for the risk assessment of foodborne pathogens in meat products in Yunnan province.The study verified the influence of sul2 gene on bacterial drug resistance,which provided an effective reference value for further research on the mechanism of bacterial drug resistance to sulfonamides antibiotics,and provided a reference basis for clinical treatment to better solve the problem of drug resistance.