Study On Isolated Ide Ntification And Pathogenicity Of Escherichia Coli Of Pigs And Environme Nt In Slaughterhouse

Swine pathogen Escherichia coli is an important zoonotic pathogen that can cause animal and human diarrhea,sepsis,endocarditis,pneumonia,urinary tract infections,young animals or infant encephalitis,peritonitis and so on.In order to understand the prevalence of Swine pathogen Escherichia coli and the pathogenicity of the strains,we collected 480liver samples,152 aerosol samples,90 sewage samples,and 93 swab samples in the slaughterhouse testing from 32 neighborhoods of Dongguan city.6 strains of pathogen Escherichia coli were selected as pathogenicity experiment of mice by bacterial isolation and culture,Gram stain,biochemical identification,serotype identification.Escherichia coli O₁₅₇:H₇ was also detected by fluorescence PCR and enzyme-linked immunofluorescence assay,and compared with the results of isolation and identification.The results of the tests are as follows:A total of 161 pathogenic Escherichia coli strains were isolated from 815 samples with a positive rate of 19.75%which contained 119 strains from pork liver with a positive rate of24.79%and 42 strains from environmental samples with a positive rate of 12.54%.The positive rate of environmental samples from high to low were:16.67%of the sewage,15.05%of the equipment,8.55%of the air.Among the 161 pathogenic Escherichia coli strains,88 strains of enterohemorrhagic Escherichia coli,22 strains of enterotoxigenic Escherichia coli,43 strains of intestinal pathogenic Escherichia coli and 8 strains of Enteric Escherichia coli were positive for 10.81%,2.70%,5.27%,0.98%,respectively.The results showed 12 types of O antigen serotype from pathogenic Escherichia coli strains which contained O₁₅₇,O₁₃₈,O₉,O₈ of the main epidemic serotypes with accounting for 54.66%,8.07%,11.80%,5.59%of the identified strains.6 strains of pathogen Escherichia coli were selected as pathogenicity experiment of mice from 161 pathogenic Escherichia coli strains.The concentration of 3×10⁸ CFU/ml was injected in o mouse peritoneal.After 8 hours,The mice had a significant abnormal reaction.Within 7 days,No.2 and 5 strains caused more than 2 deaths of the mice,and were considered as highly pathogenic Escherichia coli;Within 3 days,No.1,4 and 6 strains caused 1/6-2/6 deaths of the mice,and were considered as medially pathogenic Escherichia coli;No.3 strains with a significant reaction,but no death for the mice was considered as lowly pathogenic Escherichia coli.The mice in the control group did not respond abnormally.Escherichia coli O₁₅₇:H₇ was detected by fluorescence PCR which contained 126positive strains with a rate of 24.79%.Among them,102 positive strains were detected from pork liver with a rate of 21.25%,24 positive strains from environment samples with a rate of 7.16%.The detection rates of positive of the pig or in the abattoir were higher than segregation and identification of bacterium.Escherichia coli O₁₅₇:H₇ was detected by enzyme-linked immunofluorescence assay which contained 118 positive strains with a rate of 14.48%.Among them,97 positive strains were detected from pork liver with a rate of 20.21%,21 positive strains from environment samples with a rate of 6.27%.The detection rates of positive were higher than segregation and identification of bacterium,but lower than the results of fluorescence PCR.The results demonstrated that there existed the infection and contamination of swine pathogen Escherichia coli to varying degrees from Slaughtering utensils,air,sewage.6isolates were pathogenic and different in pathogenicity.Our results were in line with the previous results that Escherichia coli O₁₅₇:H₇ has a strong pathogenicity and should the focus of prevention and treatment.The sensitivity for the detection of Escherichia coli O₁₅₇:H₇ ranked from high to low as follows:fluorescence PCR,enzyme-linked immunofluorescence assay and general isolation and identification.Control of Escherichia coli in the pigs need to do scientific management,regular monitoring,strengthen the slaughter and quarantine,personal protection.