| Owing to antimicrobial drugs were widely used in clinical medicine and aquaculture, drug resistance about bacterias were increased and multi drug resistance problem became more and more serious. This was a wake-up call, drug resiatance caused widespread concern around the world. Escherichia coli(E. coli) as an important dwelling bacteria in the intestinal beared constantly the selection pressure of various drugs, and became to be reservoir and important exchange places of drug resistant gene.588 strains of E. coli separated from different areas of food animals (pigs, catties, chickens), pet dogs, giant panda feces and environmental samples were identificated in this experiment. According to the method and judgment standard recommended by CLSI, disk diffusion method was used to test usceptibility of 588 E.coli isolates to 13 antimicrobial agents. The results showed that 588 E. coli isolates had different levels of resistance to 13 agents(resistance rate in 7.48% to 80.44%), which had high level resistance to ampicillin, tetracycline, florfenicol, and trimethoprim sulfamethoxazole(resistance rate of more 70%). To the levofloxacin, amikacin and cefotaxime were sensitive(resistant rate under 14%). 93.5% of the E. coli strains were multi drug resistance, multi drug resistant strains were mainly in 5-11 resistance. Comparison to the drug resistance of different strains found that drug resistance rate of E. coli isolates from pet dogs to ampicillin cefotaxime amikacin and ciprofloxacin was much higher than E. coli isolated from other sources, and compared with other strains showed very significant difference (P＜0.01). Resistance rate of florfenicol, streptomycin, norfloxacin, tetracycline, ceftriaxone and aztreonam in the E. coli stains from food animal was higher than that of other strains, especially to florfenicol, ceftriaxone, aztreonam and cotrimoxazole showed significant difference compared with other strains in the drug resistance rate(P<0.01). The strains of giant panda feces and environment were low level resistance to most drugs(resistance rate less than 20.7%).320 E. coli strains were randomly selected from 588 E. coli strains identificated in this study, and they were amplified the integration of enzyme gene of type 1, type 2 and type 3 by PCR. The results showed that class 1 integron had the highest detection rate was 69.70%(138/198) in the food animals, wherein, swine, chicken and cattle were 76.92%, 71.79% and 58.18%. The detection rate of class 1 integron in the E. coli strains from pet dogs, giant panda and environmental were 64.10%,50.75%and 31.25% respectively.2 strains from swine and 2 strains from chicken were detected simultaneously class 1 and 2 integron. Class 3 integron didn’t detect in this study.145 E. coli strains of class 1 integron positive were randomly selected to amplified the resistance gene cassettes of variable regions in the class 1 integron by PCR. Gene cassette detection rates of E. coli strains from animal food, pet dogs, giant panda feces and environmental were 91.36%,88.0%,58.82% and 80.0% respectively.7 kinds gene cassette of dfrA27, dfrA17, aadA2, dfrAl-orfC, dfrA27-aadA2, aacA4-aadAl-catB2 and dfrA12-orfF-aadA2 were detected in this study. To detect 4 strains of class 2 integron positive founded that 2 types of gene cassettes dfrA1-sat2 (3 strains) and dfrAl-sat2-aadA1 (1 strains) were checked out respectively.To study the drug resistance and integron-gene cassettes of E. coli isolated from different sources found that all strains showed different level of drug resistance to 13 kinds of antimicrobial drugs, drug resistance related to strains, the most serious of drug resistance were strains isolated from canine, followed by food animals, giant panda and and living environment, drug-resistant strains were multidrug resistant. Moreover, resistance strains carried prevalent class 1 integron, aadA and dfrA mediated aminoglycosides and sulfanilamide-trimethoprim resistant were primary molecular characteristic of integron gene cassette. There is a certain correlation between phenotype of drug resistant strains and gene cassettes. |
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