Isolation And Identification Of Chicken Salmonella And Study On The Therapeutic Effect Of Phage

Salmonella is one of the main pathogens causing morbidity in modern large-scale chicken farms.Salmonella can be spread vertically through eggs,and is prevalent on farms of different scales around the world,causing great distress to the healthy development of the farming industry and animal-derived food hygiene and safety.The current treatment drugs for chicken salmonellosis are mainly antibiotics,and the long-term,massive and unscientific use of antibacterial drugs brings a series of problems.Therefore,there is an urgent need to find highly effective,safe and residue-free bactericidal agents.Phage is a virus that infects bacteria,fungi and other microorganisms.As a natural antimicrobial agent,phage has a long history of being used for clinical treatment with good results,and the use of phage for salmonellosis is a good alternative to antibiotic treatment.In this study,Salmonella was isolated from breeding farms,screened for virulence genes and drug resistance,and screened out the strong phage system to study their biological characteristics,and initially applied the phage to Salmonella infection in chicks,and provide theoretical basis and technical support for the clinical application of phage.1.Isolation and identification of chicken-derived SalmonellaSamples of sick chickens were collected from the farm,and 80 strains were isolated by isolation and culture,morphological observation,biochemical tests,including 30 strains of Salmonella enterica,29 strains of Salmonella enterica and 21 strains of Salmonella typhimurium.The results showed that Salmonella enterica,Salmonella dysenteriae and Salmonella typhimurium were mainly isolated from chickens,and Salmonella avian typhoid was not acquired by isolation.2.Detection of drug resistance and virulence gene screening of Salmonella spp.The results of drug resistance and virulence gene screening of 80 isolated strains of chicken-derived Salmonella showed that chicken-derived Salmonella was resistant to multiple antibiotics,among which five drugs,clindamycin,lincomycin,azithromycin,amoxicillin and doxycycline,showed high resistance,and the percentage of multi-drug resistant strains was83.75%;the isolated strains generally carried drug resistance genes.14 out of 16 drug resistance genes were detected to varying degrees.The correlation analysis of drug resistance phenotype and drug resistance gene detection showed that the detection of drug resistance phenotypes,except that the detection of beta-lactam bla TEM genes and SHV genes and antibiotic resistance was 100%.The results of virulence gene screening showed that the isolated chicken-derived Salmonella mostly carried virulence genes: 16 virulence genes were detected in different proportions in 80 isolates,among which 12 virulence genes were detected at a rate of more than 80%.3.Isolation and biological characterization of Salmonella phagesA whole of 36 Salmonella phages have been remoted with the aid of the bilayer plate method.All 36 phages ought to cleave Salmonella with two or greater serotypes,with phage vB＿SalP＿LDW16 having a large host spectrum and splitting 81.3% of Salmonella lines maintained in the laboratory.Biological learn about of phage vB＿SalP＿LDW16 indicates that vB＿SalP＿LDW16 is a tail phage with lengthy tail phage;best contamination is 0.01;excessive temperature resistance,50 ℃ bathtub 1 h;acid-base temperature and p H=6～12;incubation length is 10 min,outbreak duration 60 min,outbreak quantity is 110 CFU/cell.Phage vB＿SalP＿LDW16 confirmed low healing in intestinal and gastric contents and maintained inside 6%,steady with phage acid intolerance properties.4.Therapeutic effect of Salmonella phageThe therapeutic impact of phage vB＿SalP＿LDW16 on chick contamination with Salmonella enteritis used to be measured by way of an animal contamination test.Salmonella contamination mannequin the use of phage vB＿SalP＿LDW16,amoxicillin,flufenicol,and neomycin,the survival fee used to be 100%,and the bacterial content material in the blood steadily decreased,and no giant pathological modifications have been found,the remedy impact used to be notably higher than amoxicillin and neomycin cure group,and the impact of flufenicol cure group,however the phage remedy team chicks weight used to be extensively greater than the flufenicol therapy group,no longer considerably distinct from the blank control group.In conclusion,the bacteriophage vB＿SalP＿LDW16 is nice in treating chick contamination precipitated by means of Salmonella enteritidis QD200601.