The Relationship Between Salmonella Drug Resistance And Metabolic Characteristics In Meat Foods

Salmonella is a typical food-borne pathogen,and its pollution poses a serious threat to human health.With the widespread use of antibiotics,the resistance of Salmonella is becoming more and more serious.It may exist in every link of the food production chain and cause serious harm to human health through food.The distribution and transmission mechanism of drugresistant Salmonella in the food chain has become a current research hotspot,and there is an urgent need to carry out studies on drug resistance of Salmonella in different food chain links.In this paper,181 strains of Salmonella were taken in the three food chains of meat production,aquaculture,slaughter and retail as the research object.We studied the spatial distribution of food-borne Salmonella drug resistance,and analyzed the relationship between drug resistance and metabolomics.The relationship between them provides new ideas and methods for drug resistance mechanism research and prevention and control.The main contents are as follows:1.Study the spatial distribution characteristics of Salmonella resistance in meat products.Through the collection of samples from all links of the food chain,it was found that Salmonella contamination was the most serious(74.18%)in the aquaculture,and the serotype was relatively single.The pollution rate in the retail link is 16.68%,but the serotype is abundant.The pollution in the slaughter link is relatively lower(7.14%).All Salmonella showed resistance to ciprofloxacin,levofloxacin and trimethoprim / sulfamethoxazole.Salmonella resistant to 10-15 antibiotics accounted for 56.72% in the aquaculture,and Salmonella resistant to more than 15 antibiotics accounted for 20.90%;Salmonella resistant to 5-10 antibiotics accounted for the largest proportion in the retail sector.Salmonella from different sources have different levels of resistance.The overall resistance of Salmonella in pigs were significantly higher than those of Salmonella in chicken,and the multi-drug resistance was also more serious.The strains resistant to 10 to 15 antibiotics accounted for 57.28%,and those resistant to more than 15 antibiotics reached 25.24%.2.To study the correlation between the drug resistance and the metabolic of Salmonella from different serotypes and sources.First,a metabolomic pretreatment method based on gas chromatography-time of flight mass spectrometry(GC-TOFMS)was established for drugresistant Salmonella.Compared with conventional methods,the number of metabolites can be increased 30%~40%,and the abundance of drug-resistant metabolites increased by 25%.Metabolomics results show that there are large differences in the metabolic characteristics of different serotypes and different sources of Salmonella.The metabolic characteristics of Salmonella to nitrofurantoin,cefepime,and ceftriaxone differed significantly,while the metabolic characteristics of strains resistant to and sensitive to amikacin and meropenem were relatively small.In addition,it was found that with the increase in the degree of drug resistance,the change in its metabolic characteristics is also more obvious.3.The relationship between the Salmonella metabolic pathway and cephalosporin antibiotic resistance was studied.According to the cephalosporin antibiotics commonly used in clinical practice,the same source(pig origin)and the same serotype(Derby)were selected for metabolomic and transcriptome analysis.The results showed that the resistance of Salmonella cephalosporin antibiotics and the characteristics of bacterial metabolism certain relevance.According to statistical analysis,30 metabolic substances with significant differences were identified,including 6-phosphogluconate,glutathione,citric acid and so on.The enrichment of metabolic pathways revealed that the resistance characteristics of cephalosporin antibiotics were related to five metabolic pathways,including lysine metabolism,sulfur metabolism,glutathione metabolism,cysteine and methionine metabolism,and pentose phosphate metabolism.Enrichment of differentially expressed genes by transcriptomics verified the results of metabolomics and found that the pentose phosphate pathway and sulfur metabolic pathway are related to the cephalosporin antibiotic resistance phenotype.Glutathione synthesis and energy metabolism maybe the main reason to drug resistance.