Study On The Prevalence And Transmission Characteristics Of Listeria Monocytogenes In Cattle And Sheep Breeding And Food Chain

Listeria monocytogenes is an important food-borne pathogen with the highest mortality rate,which is widely distributed in the natural environment and can cause infection in immunocompromised populations,causing clinical and pathological changes such as meningitis,septicemia,abortion and central nervous system symptoms.Cattle and sheep,as natural hosts,can transmit Listeria monocytogenes to related meat and dairy products.At present,the epidemic background and transmission characteristics in cattle and sheep breeding and food chain in China are not clear.Therefore,it is very important to investigate the prevalence of Listeria monocytogenes in cattle and sheep breeding and food chain in the main producing areas of cattle and sheep in China,and to clarify the transmission characteristics of Listeria monocytogenes in them for food safety prevention and control.1.A large number of samples were collected from farms,slaughterhouses and retail markets in the main producing areas of cattle and sheep in China for routine bacterial isolation and identification.According to the isolation rate of Listeria in various samples and geographical environment factors,combined with SPSS statistical analysis,the preliminary epidemiological analysis was carried out.It was found that the environment and the dryness of forage grass might be related to the low isolation rate of Listeria monocytogenes in some areas of the breeding link,and the slaughter link and market circulation link were the key links to control the epidemic and transmission risk of Listeria monocytogenes in cattle and sheep breeding and food chain.2.The phenotypic and genotypic characteristics of the isolated strains were analyzed,and the results showed that the Listeria monocytogenes isolated from cattle and sheep breeding and slaughtering included 1/2a and 1/2c serotypes,and the Listeria monocytogenes isolated from market circulation included 1/2a and 1/2c serotypes.The isolated strains included 1/2a,1/2b,1/2c,4b,7 serotypes;Listeria monocytogenes serotypes ST7,ST9,ST91 and ST155 found in cattle and sheep breeding and slaughtering,and serotypes ST2,ST9,ST87,ST101,ST121,ST155,ST307 and ST619 found in market circulation were associated with the incidence of human listeriosis in China.In addition,Listeria monocytogenes in cattle and sheep farming and the food chain have highly pathogenic virulence markers that are closely related to the pathogenesis of human listeriosis(LIPI-3,LIPI-4 and ECIII)and multiple drug resistance;In this study,Listeria incocua showed an absolute epidemic advantage,some strains of Listeria innocua were found to have virulence genes on the virulence islands3 and 4,and the mouse virulence test showed lethality,all of which indicated potential public health risks and had certain public health significance.3.Pulsed-field gel electrophoresis(PFGE)was used to study some representative isolates,and it was found that the same strains could be found in different types of samples,which provided a strong molecular basis and theoretical data for exploring the transmission route and law of Listeria monocytogenes.The results showed that Listeria monocytogenes could spread to the final meat products from the breeding link to the slaughter link along the slaughter chain,especially the quantitative analysis results of cattle slaughterhouse samples showed that the degree of contamination increased step by step.Contamination and epidemics run through the entire food chain.4.The multi-locus sequence typing and single nucleotide polymorphism evolutionary analysis based on the core genome after the whole genome sequencing also proved the above pollution path,the strain could enter the slaughter link from the breeding link,and the strain might spread across regions through cattle transfer/forage transfer/ bird migration/meat product cross-regional circulation.This study explained the epidemic and transmission law of Listeria monocytogenes in cattle and sheep breeding and food chain in the main producing areas of cattle and sheep in China,involving a wide geographical area,a large number of samples and isolated strains,good representativeness,systematic analysis and research,objective data,filling in the epidemiological background of Listeria monocytogenes in cattle and sheep breeding and food chain in China.It provides a scientific basis for the prevention and control of listeriosis in humans and animals,the formulation of national food safety standards and related scientific research.