Study On Identification And Drug-resistance Of Escherichia Coli Isolates From Swine In Hebei Province

For a long time,antibacterial drugs have been the best choice for the prevention and treatment of Escherichia coli(E.coli)infection,and can also promote the growth of animals and improve feed utilization.However,the unscientific application of antibiotics in animal production has highly attracted people’s attention.And the continuous evolution and spread of multi-drug resistant bacterium have posed a great threat to the diagnosis and treatment.These bacterium not only affected the development of the pig industry,but also could be transmitted to humans through the use of genetic material,food sources and other medium,to harm our bodies.Therefore,it is of great significance to understand the status quo of the drug resistance of pig-origin E.coli and its carrying drug-resistant genes.In this study,the samples collected form pigs of Hebei Province were detected for the isolation and identification of pig-origin E.coli,and System analysis of drug susceptibility and drug-resistance genes of pig-origin E.coli was carried out.The results showed that the E.coli of pig origin had a relatively high drug resistance and carried multiple resistance genes.This will help guide the pig farms to scientifically regulate the use of antibiotics and reduce the spread of drug-resistant bacterium,thus providing healthy and safe animal products.The main research works were as following: 1.672 pig-origin samples(540 intestinal swabs and 132 pork)from Hebei Province in 2017 were cultured,detected and identified by Makanke Medium and Eosin Methylene Blue Ager Medium.580 pig-origin E.coli strains were isolated at last withthe positive rate of 86.31%(580/672),including 480 samples of pig intestinal swabs with the positive rate of 88.89%(480/540)and 100 samples of pork with the positive rate of 75.76%(100/132).2.The MICs of 13 kinds of antibiotics were detected by broth microdilution method to resist 580 E.coli strains.The results show that the drug-resistant rates of these pig-origin E.coli resisting ampicillin,spectinomycin,doxycycline,enrofloxacin,florfenicol,Polymyxin B and Sulfamonomethoxine were 98.97%,96.55%,96.55%,96.89%,95.17%,98.97% and 100%,respectively.And the drug-resistant rates resisting Amocicillin/Clavulanic acid,Ceftiofur,Amikacin,Levofloxacin and Maquindox were between 68.62% and 89.67%.While the drug-resistant rate resisting Meropenem was only 13.45%.All of these E.coli strains were multi-drug resistant bacterium.So suitable drugs should be selected for clinical treatment.3.The drug-resistant genes of 290 multi-drug resistant E.coli strains were detected using PCR method.The results showed that the prevalence genes rates the β-lactamases(ESBLs)and cephalosporinase(AmpC)of TEM,CTX-M,CTX-M-1,CTX-M-9,and CMY were 69.66%,44.17%,26.55%,34.38%,and 27.94%,respectively.And the prevalence genes rates of the quinolone-resistant gene oqxA,oqxB,qnrS,parC and gyrA were between 20.35% and 74.83%.While the detection rate the metallo-β-lactamase and mobile colistin resistance of NDM-1 and mcr-1 genes were 43.59%(34/78)and 26.55%(77/290),respectively.The pig-origin E.coli carrying NDM-1 and mcr-1 genes were multi-drug resistant bacterium.