| Yersinia enterocolitica is an important foodborne pathogen,which can cause Yersiniosis.Pigs are the main host of Yersinia enterocolitica.People usually suffer from Yersiniosis by eating pork contaminated with Yersinia enterocolitica,which has a case fatality rate of up to 50% for the elderly,young children and people with weak immunity.At present,there are few domestic reports on the contamination of Yersinia enterocolitica and the biological characteristics of Yersinia enterocolitica isolates in Hubei Province.In this study,samples were collected from three pig slaughterhouses in Hubei Province in 2021,and Yersinia enterocolitica was isolated and identified from the samples.The biological characteristics such as biotypes,virulence genes carried,antibiotic resistance,biofilm forming ability and disinfectant resistance of Yersinia enterocolitica isolates were determined and analyzed.Molecular typing of Yersinia enterocolitica isolates were also carried out based on enterobacterial repetitive intergenic consensus.Through the above research methods and results,the contamination of Yersinia enterocolitica in the three pig slaughterhouses,the biological characteristics of Yersinia enterocolitica isolates and the genetic diversity among Yersinia enterocolitica isolates were mastered,so as to provide data support for pig slaughterhouses to prevent and control Yersinia enterocolitica contamination and formulate safety strategies.All results are as follows:1.Contamination of Yersinia enterocolitica in pig slaughterhousesIn May 2021 and July 2021,1950 samples were collected from three pig slaughterhouses(A pig slaughterhouse,B pig slaughterhouse and C pig slaughterhouse)in Hubei Province,including 450 nasal swabs of pigs to be slaughtered,450 rectal swabs of pigs to be slaughtered,450 body surface swabs,480 pork samples and 120 environmental samples.Nine strains of Yersinia enterocolitica were isolated from these samples,and the total separation rate is 0.46%.Among the three slaughterhouses,the separation rate of Yersinia enterocolitica in C slaughterhouse is the highest,with the separation rate of 1.19%.There is no significant difference in the separation rate of Yersinia enterocolitica between May and July.Among the samples from different Slaughtering links,the separation rate of Yersinia enterocolitica in pork samples is the highest,with the separation rate of 1.67%.2.Biological characteristics of Yersinia enterocolitica isolates2.1.BiotypeThe results of aescin hydrolysis test showed that the biotypes of all Yersinia enterocolitica isolates were biotype 1A.2.2.Virulence genesThe results of PCR showed that the virulence gene with the highest detection rate is ymo A(100%),followed by yst B(88.89%),inv A(66.67%)and myf A(44.44%),none of the Yersinia enterocolitica isolates carry ail and yst A.2.3.Antibiotic resistanceThe results of antibiotics-sensitivity test showed that all Yersinia enterocolitica isolates are resistant to ampicillin,one strain of Yersinia enterocolitica isolates is resistant to tetracycline and all Yersinia enterocolitica isolates are sensitive to gentamicin,ciprofloxacin,aztreonam,polymyxin B,cefotaxime,meropenem,cefepime and florfenicol.2.4.Biofilm forming abilityThe results of crystal violet staining showed that all Yersinia enterocolitica isolates could form biofilm at 25℃,when cultured at 25℃ for 24 hours,two strains of Yersinia enterocolitica isolates showed medium and strong biofilm forming ability;when cultured at 25℃ for 48 h,five strains of Yersinia enterocolitica isolates showed medium and strong biofilm forming ability.2.5.Disinfectant resistanceIn this study,the suspension quantitative sterilization test was carried out with the minimum effective concentration of peracetic acid and benzalkonium bromide specified in the technical specification for disinfection of livestock and poultry slaughtering enterprise.The results showed that the sterilization rate of Yersinia enterocolitica was 100% when 60 mg/L peracetic acid was used for 5 minutes and 200mg/L benzalkonium bromide was used for 2 minutes,indicating that the Yersinia enterocolitica isolates are sensitive to peracetic acid and benzalkonium bromide.200 mg/L is the effective chlorine concentration specified in the specification.In this study,sodium hypochlorite with an effective chlorine concentration of 200 mg/L was used for 2 minutes,and the sterilization rate of Yersinia enterocolitica isolate was92.67%,indicating that the Yersinia enterocolitica isolate is resistant to sodium hypochlorite.3.ERIC-PCR typing of Yersinia enterocolitica isolatesThe ERIC of nine Yersinia enterocolitica isolates were determined by PCR.It was found that Yersinia enterocolitica isolates could be divided into 2 clusters and 3 types,and the similarity coefficient ranged from 0.15 to 1.00,reflecting the high genetic diversity among the Yersinia enterocolitica isolates. |
