| With the mass use of antibacterials in animal husbandry industry, drug resistance occurs in bacterium and the phenomenon of multidrug resistance has been increasing, which arouses wide attention of the whole world. Escherichia coli, as the main parasitic bacterium of intestinal tracts in livestock and poultry, bears selection pressure from various kinds of drugs and becomes storage cavern of multidrug resistant gene. So the detection of drug resistance can understand prevalence regularity, predict development trend of drug resistance, evaluate the risk of antibacterials and provide scientific basis for the rational use of antibacterials in clinic.914 strains of E. coli were isolated and identified from anus swab samples of health livestock and poultry from different nurseries and food retail stores in Sichuan. According to the recommendation method and judge standards of CLSI,25 antibacterials were used for the analysis of the drug resistance of the 914 srains of E. coli by micro broth dilution method. The result of drug resistance detection showed the drug resistance of the 914 strains of E. coli to the 25 antibacterials was very severe (the rate of drug resistance was 2%-98%). Among them, the resistance rate to Rifampin, Trimethoprim and Trimethoprim-sulfamethoxazole was above 98%, the resistance rate to Ampicillin, Amoxicillin+Clavulanic Acid, Streptomycin,Tetracyline,Doxycyclinec. Florfenicol and Nalidixic acid exceeded 70%, and the rate to Ceftriaxone,Ceftiofur and Amikacin was less than 30%, showing that the 914 srains of E. coli were sensitive to these antibacterials. 99.8%of the strains were multidrug resistant and the range of the resistence was 12-25. Comparison of the drug resistance of the strains from different animals demonstrated resistence rate of strains from ducks were higner to Cephazolin,Ceftiofur,Amoxicillin +Clavulanic Acid,Florfenicol,Rifampin, Trimetho-prim,Trimethoprim-sulfamethoxazole, the lower were srains from chicken and the strains from pigs were the lowest. Besides the highest rate of the strains from chicken to Danofloxacin, the rate of strains from pigs were highest to the remaining 17 antibacterials and the rates were close between strains from chicken and duck.455 strains of E coli were randomly picked from the 914 strains for tha amplification of the integrase genesⅠ,Ⅱ,Ⅲby multiple PCR. The results of multiple PCR showed the carrier rate of integrase gene I in pig origin strains was 92.95%, the rate in chicken origin was 86.55%and the rate in duck origin was 85.55%. The detection of integron II discovered integron I and integron II were both detected in 4 pig origin strains and 5 chicken origin strains. Integron III was not detected out in this study.204 of strains positive in integron I were randomly picked, variable region of the drug resistance gene was amplified by PCR, the results showed the detection rates of the box gene from pig, chicken and duck origins were 88.73%,83.95%and 82.69%respectively.8 different kinds of box genes were detected out using the methods of DNA sequence and RFLP. The most frequent amplification fragment was 1572bp, the characteristic of the box gene was dfrAl-aadA, the range of the amplification fragment from the remaining box genes whch were dfrA27, dfrA17, aadA22, dfrA1-orfC, dfrA17-aadA5, dfrA12-orfF-aadA2 and aacA4-catB3-dfrAl were 751-2731bp. The detection of the integron II discovered 3 kinds of box genes were detected out which were dfrAl-sat2, dfrAl-sat2-aadAl and estX-sat2-aadAl and the fragments were between 1276-2509bp.The detection of drug resistance and integron-box gene of livestock and poultry intestinal tract-origin E. coli in Sichuan Province showed the drug resistance to 25 antibacterials were very severe in different livestock and poultry and multidrug resistant strains were prevalent. Drug resistant strain generally carried integron I and the molecule characteristic was mainly dfrAl-aadAl. The phenotype of drug resistant strain was corelated with integron that it carried. |
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