| Salmonella spp.is an important zoonotic and foodborne pathogen.Pigs are usually asymptomatic carriers and Salmonella from pigs can be colonized in pig herds on farms and spread widely in all stages of the pork production chain.People eat the pork food contaminated by Salmonella can cause fever,vomiting,diarrhea and even death in humans.In recent years,the extensive use of antibiotics in farms has led to the production of a large number of multi-drug resistant Salmonella bacteria,which has created obstacles to humans in clinical therapeutics.In this study,the prevalence and antimicrobial resistance Salmonella were analyzed on pig farms and slaughterhouses in Hubei Province,combined with the previous laboratory research to analyze the pollution and spread of Salmonella in representative farms and slaughterhouses.And to establish the key risk points in the breeding and slaughter process,provided data support for carrying out Salmonella risk assessment and formulating source prevention and control strategies.The main results are as follows:.1.Study on the prevalence and antimicrobial resistance of Salmonella in pig farms in Hubei ProvinceA total of 1143 pig samples and environmental samples were collected from 26 pig farms in Hubei Province in 2019,of which 168 were detected with Salmonella,with a detection rate of 14.70%.155 Salmonella strains were isolated from 885 rectal swab samples from 22 fattening farms,with an isolation rate of 17.51%.A total of 150 rectal swab samples were collected from 4 breeding farms,and 10 strains of Salmonella were detected in sows and suckling piglets.The isolation rate of Salmonella in different fattening farms ranges from 0.00% to 70.00%.The results of antimicrobial susceptibility experiments indicated that the multi-drug resistance rate of Salmonella isolates in the fattening farm was 95.33%.Salmonella isolates have the highest resistance to CHL(100.00%),SXT(100.00%),followed by TET(93.46%),AMP(80.37%),AMC(62.62%),CTX(37.38%),GEN(34.58%),the resistance rate to CIP is the lowest(24.30%).The study also found that the antimicrobial resistance spectrum of the feed was similar to that of the sow and the fattening pig isolates in the same farm,but Salmonella was not isolated from water samples,suggesting feed was the HACCP of Salmonella prevention and control in farms.Therefore,it is necessary to strictly control the pollution of feed and the use of drugs in the farm.2.Study on the prevalence and antimicrobial resistance of Salmonella in pig slaughterhouses in Hubei ProvinceA total of 2,805 pig body samples and environmental samples from different slaughter stages were collected in 4 large pig slaughterhouses in Hubei Province in 2019,and 456 Salmonella strains were detected,with a total detection rate of 16.26%.Slaughterhouses A,B,C,and D detected 131,192,84,and 49 Salmonella strains,respectively,and the site-positive rates were 15.11%,17.42%,14.19%,and 20.08%.Slaughterhouse D had the highest positive rate,and significantly higher than the positive rate of C(p<0.05).In terms of different slaughter stages,the isolation rate of Salmonella in the depilation stage is lower,while the isolation rate of the electric hemp and the splitting stage is higher.Among the environmental samples,Salmonella was detected in the shower water of slaughterhouse A,the knife swabs,cold storage floor swabs,electro-anaesthetic bloodletting of slaughterhouse B,air samples from the splitting stage and the cold storage stage of slaughterhouse C.The results of antimicrobial susceptibility experiments revealed that the resistance rates of the isolates to SXT(100.00%),TET(98.03%),AMC(94.93%),AMP(91.27%)and CHL(89.01%)were all >80.00%,while the resistance rate to CTX(57.18%),GEN(61.69%)and CIP(53.08%)was relatively low.The air and knives may be the main cause of cross-contamination of Salmonella in the slaughter process.3.Whole genome sequencing analysis of Salmonella in Hubei ProvincePreliminary analysis of the sequencing data of 117 Salmonella strains showed that the main ST types of Salmonella isolates from pig farms and slaughterhouses in Hubei Province were ST34,ST40 and ST469.Different 69 antimicrobial resistance genes,106 virulence genes and 14 virulence islands were identified.The MLST type of strains isolated from slaughterhouses was more than that of Salmonella isolated from slaughterhouses.Most of the antimicrobial resistance genes carried by Salmonella are related to antimicrobial efflux,and the antimicrobial resistance phenotype is basically consistent with the genotype.ST34 carried more virulence islands and virulence genes than other ST types.To sum up,Salmonella contamination is common in pig breeding and slaughtering stages in Hubei Province,and severe multi-drug resistance was found in these isolates.Farms should pay attention to the monitoring of Salmonella in feed and the correct and the the correct use of drugs.In addition to the transmission of Salmonella in pig carcasses along the slaughtering chain,there are Salmonella contaminated meat from environmental sources in slaughterhouses,so the disinfection of environment and utensils should be strengthened. |
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