| Pathogenic Escherichia coli,Campylobacter jejuni,Listeria monocytogenes and Clostridium perfringens are important pathogens in veterinary clinics,which have an important influence on the occurrence of swine diseases and public health,holding great value for monitoring these pathogens.Antibacterial drugs have played an important role in the treatment of swine bacterial diseases.However,due to unreasonable use,the resistance of bacteria have been increasing.The scientific and rational use of antibiotics have became an important industrial demand.In order to understand the prevalence of important pathogens in large-scale breeding farms,493 anal swabs of diarrhea swines in Jiangsu Province were collected.The established PCR method was used to detect pathogenic Escherichia coli,Campylobacter jejuni,Listeria monocytogenes and Clostridium perfringens.The results showed that:the common pathogenic E.coli positive samples were 301(61%),Campylobacter jejuni positive samples were 3(0.6%),Listeria monocytogenes positive samples were 2(0.4%),the period of delivery There were 14 positive samples of Clostridium perfringens(2.8%).The result indicates that pathogenic E.coli is still the major pathogen of piglet diarrhea.Although Campylobacter jej uni,Listeria monocytogenes and Clostridium perfringens are low-frequency infections,they are worthy of attention in public health.Bacteriological separation of samples that tested positive for pathogenic E.coli resulted in 301 isolates of E.coli.Through the detection of common fimbriae,toxins,virulence islands and other genes,it was found that the isolates had 16 different virulence gene types,including F18+Stx2e+125(41.5%)and HPI+68(22.6%),Stx2e+30(10%),LT1+ST2+20(6.6%),F4+Stx2e+ 10(3.3%),LT1+ST1+10(3.3%),ST1+ST2+Stx2e+9(3%),F4+6(2%),F41+5(1.7%),ST2+4(1.3%),F5+3(1%),LEE+ 3(1%),LT1+3(1%),ST1+3(1%),F4+F5+ F41+1 isolate(0.3%)and ST1+ST2+LEE+Stx2e+ 1(0.3%).Further analysis showed that HPI+ E.coli and enterotoxigenic E.coli are the main pathogens of diarrhea in piglets from 1 to 15 days old,while Stx2e+ enterotoxigenic E.coli mainly comes from diarrhea piglets over 30 days.By using the O antigen single factor serum to identify the O antigen type of the isolate,the O antigen type of 151 isolates of E.coli was determined,which were O139(66.8%),O107(11.9%),O15(10.6%),and O45(2.6%).%),O101(2.6%),O54(1.3%),O21(0.7%),O138(0.7%),O78(0.7%),O141(0.7%),O159(0.7%),O111(0.7%).The O139 serotype is mainly found in F18+Stx2e+ isolates.In order to compare the virulence differences of variety virulence factor types of E.coli,three representative isolates(F4+,F41+Sxt2e+,ST 1+ST2+LEE+Stx2e+)were selected,and 4-week-old ICR mice were half lethal.The results showed that the LD50 of tested isolates were 3.5×109CFU/0.5ml,1.9×109CFU/0.5ml,1.2×109CFU/0.5ml,respectively,showing that the virulence of pathogenic Escherichia coli is obviously correlated with the virulence genes it carries.After pathological anatomy of the mice,it can be found that the small intestinal cells of the challenge group are not clear,cell necrosis,intestinal mucosa shedding,inflammatory cell infiltration and other obvious lesions,while no lesions are found in the control group.Antibiotic resistance of 150 isolates of pathogenic Escherichia coli was determined for veterinary clinical use.The results showed that most of the isolate(83.3%)were resistant to 6～8 antibiotics.Among them,the drug resistance rates of ciprofloxacin,amicacin,ampicillin,doxycycline,ceftriaxone,polymyxin,neomycin,canamycin,amoxicillin,tetracycline,genamicin,fosfomycin and cotrimoxazole were 90.7%,87.3%,80.7%,78%,67.3%,57.3%,56.7%,52.7%,51.3%,50%,43.3%,12.7%,10.7%.Further analysis showed that there were certain differences in bacterial drug resistance of piglets with different age and different regions,and the older the piglets were,the higher the bacterial resistance rate was.This should be related to the frequency of clinical drug use and the difference of drug use in different regions. |
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