| Escherichia coli is one of the most common conditional pathogens in animal clinic.It has been widely studied because Escherichia coli often cause a variety of diseases in animals.Pigs are one of the animals most affected by Escherichia coli,which often bring huge economic losses to large-scale pig farms.All kinds of antibiotics are widely used in veterinary clinic because of their preventive and therapeutic effect on Escherichia coli,but with the increase of frequency,the resistance rate of Escherichia coli to antibiotics commonly used in veterinary clinic is getting higher and higher,it not only makes it more difficult to treat Escherichia coli diseases,but also may spread drug resistance to humans through contaminated meat products.I t is of great economic and public health safety significance to carry out the research on drug resistance and drug resistance genes of Escherichia coli isolated from pigs.In this study,112 strains of Escherichia coli were isolated from the feces of suckling piglets,weaning piglets,pregnant sows and reserve sows from large-scale pig farms in Harbin.In order to study the resistance of Escherichia coli to common veterinary antimicrobial agents and the carrying of drug-resistant genes mediated by Escherichia coli,and to understand the drug resistance mechanism of porcine Escherichia coli in Harbin area,and to provide theoretical guidance for clinical veterinary drug use.In this study,the drug sensitivity test of 112 strains of Escherichia coli was carried out by Kmurb drug sensitivity disk method.The results showed that the resistance rates of isolated strains to β-lactam antibiotics were amoxicillin(76.79%),ampicillin(83.04%),Cefalexin(37.50%),cefotaxime(14.29%),ceftriaxone(23.21%)and cefoxitin(0%).The resistance rates of aminoglycoside antibiotics were streptomycin(56.25%),kanamycin(26.79%),amikacin(25.00%)and gentamicin(39.29%).The resistance rate to enrofloxacin was 12.50%.The resistance rates to florfenicol and chloramphenicol were the same,both 33.04%.The resistance rates to tetracyclines(83.93%)and doxycycline(37.50%)were respectively tetracycline(83.93%)and doxycycline(37.50%),but the intermediary rate of isolated bacteria to doxycycline was the highest in this experiment,reaching 39.29%.The resistance rate to sulfonamides compound sulfamethoxazole was the highest in this experiment,reaching 84.82%.PCR was used to detect 30 resistant genes mediating the resistance of Escherichia coli to five commonly used antibiotics.The results showed that the detection rates of β-lactam resistant genes were TEM(93.75%),CTX-M(83.33%)and OXA(22.32%),respectively.The detection rates of aminoglycoside resistance genes were ant(3”)-Ia(100%),aac(6’)-Ib(73.21%),aph(3’)-Ⅱa(35.71%)and rmt B(71.25%),respectively.The detection rates of fluoroquinolone resistance genes were qnr S(75%),aac(6’)-Ib-cr(62.50%),oqx A(50%),oqx B(89.29%)and qep A(93.75%).The detection rate of flo R gene was 83.93%.The detection rates of tetracycline resistant genes tet A,tet B and tet M were 96.43%,73.21% and 82.14%.To sum up,Escherichia coli isolates from large-scale pig farms in Harbin produced a certain degree of resistance to commonly used antibiotics,and related drug resistance genes were detected.According to the test results,we can understand the resistance of porcine Escherichia coli to common veterinary drugs and the carrying status of related drug-resistant genes in Harbin area,which provides feasible guidance for the clinical use of veterinary drugs in this area. |
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