Whole Genome Sequencing Analysis Of Salmonella From Cattle And Sheep Sources In Some Areas Of Xinjiang And Its Related Pathogenicity

Salmonella is a common foodborne pathogen in nature,and eating animal-derived foods contaminated by it can cause serious diseases.Salmonella has many pathogenic serotypes,encoding different enterotoxins and virulence factors,resulting in diseases with different degrees of harm to the body.At present,the resistance of Salmonella has restricted the use of many antibacterial drugs,especially the emergence of multi-drug-resistant Salmonella,which has greatly increased the difficulty of prevention and treatment of Salmonella.With the rapid development of whole genome sequencing technology,with the reduction of cost and the improvement of bioinformatics analysis capabilities,it has facilitated the study of Salmonella drug resistance and pathogenicity.Therefore,in this study,the whole genome of Salmonella isolated and identified in the xinjiang cattle and sheep industry chain was analyzed,and representative strains of infected Kunming mice were selected for pathogenicity study.The specific studies are as follows:(1)Through the whole genome sequencing analysis of 100 strains of Salmonella,the results showed that the 100 strains of Salmonella had 6 serotypes(Salmonella Agona,Salmonella Cerro,Salmonella typhimurium,Salmonella enteritidis,Salmonella Indiana,Salmonella Mbandaka),6 MLST types(ST13,ST367,ST34,ST11,ST17,ST413)and 4 O antigen types(O: 4(B),O: 18(K),O: 9(D1),O :7(C1)).The number of virulence genes carried by 100 Salmonella strains was found to be 112 by virulence factor database prediction;37 drug resistance genes in 9 categories were predicted by drug resistance gene database analysis,and all of them carried aminoglycoside-resistant aac(6’)-Iaa genes;100 Salmonella strains carried 18 plasmids by plasmid database prediction.The plasmid database predicted that 100 Salmonella strains carried 18 plasmids,of which Col(MGD2)＿1(29%)was the dominant plasmid.(2)Resistance of 100 strains of Salmonella in 100 strains was investigated by agar dilution method on the resistance of 10 classes of 14 antibacterial drugs,and the results were,from high to low: cefotafurofuran(69%),sulfamethazine(68%),tetracycline(63%),polymyxin E(62%),ceftriaxone(54%),cefoxitin(53%),kanamycin(50%),enrofloxacin(49%),ampicillin(49%),amoxicillin clavulanate potassium(48%),azithromycin(33%),Chloramphenicol(33%)and ciprofloxacin(15%).96% of the 100 strains of Salmonella are multi-resistant.(3)The pathogenicity of the six serotypes of Salmonella infected Kunming mice by gastric infection,the survival rate,weight change,colonization bacterial load in the organs and the concentration changes of cytokines such as IL-2,IL-4,TNF-α,INF-γ in the serum were analyzed,and it was found that the lethality rate of Salmonella Agona to Kunming mice was 50%,and the fatality rate of Salmonella Indiana was 0%.The largest colonization of the six serotypes of salmonella in the mesenteric lymph nodes,liver,spleen and cecum were Salmonella Agona,salmonella Cerro,Salmonella enteritidis and Salmonella Agona.The six serotypes of salmonella can cause extremely significant changes in the concentration of IL-2,IL-4,TNF-α,INF-γ after 1 day of gastric infection in Kunming mice(P < 0.0001).Salmonella Agona and Salmonella Cerro had a higher effect on the concentrations of four cytokines after gastric infection for 1,4,and 7 days than the other four serotypes.In summary,this study understands the serotype and multi-bit sequence typing,resistance genes,virulence genes,plasmids and drug resistance of Salmonella in the cattle and sheep industry chain in some areas of Xinjiang through whole genome sequencing combined with drug resistance investigation,provides data support for the whole genome detection platform of Salmonella in Xinjiang Industrial Chain,compares the pathogenicity of six serotypes of Salmonella to Kunming mice,and provides a scientific basis for the pathogenicity of different serotypes of Salmonella.