Study On The Correlation Between The Drug-resistance Of Escherichia Coli And Drug Use In Pig Farms

Porcine Escherichia coli from scaled pig farms has been isolated to study the correlation between drug-susceptibility and-resistance of Escherichia coli and drug use in scaled pig farms, and to investigate the drug-resistant genes of bacteria.1. The test, which collects anal swab of sow from eight pig farms to isolate and identify Escherichia coli of330strains with MacConkey flat and PCR method, has employs the K-B method to check the sensitivity of porcine Escherichia coli to fifteen kinds of drug in five types of antibiotics(Tetracycline antibiotics,sulfa antibiotics、aminoglycosides、quinolones、cephalosporins), and also have made a detailed survey of drug use in eight pig farms. Drug susceptibility results and drug use are combined to make a comprehensive analysis and it shows that Escherichia coli in eight pig farms has strong resistance to streptomycin, cefalotin, tetracycline, ofloxacin and sinomin.Escherichia coli has also high resistance to low generation antibiotic, such as cephalothin in cephalosporin drugs and relative low resistance to cephalothin V and ceftazidime, and has developed some resistance to high generation drugs of cephalosporin, aminolycosides, quinolones, as well as part of Escherichia coli strains. As for tetracycline and sulfonamides, some productive species has basically lost its antibacterial effect towards Escherichia coli. There is no difference of drug sensitivity among various tire sows from the same pig farm. The result of survey indicates that the use of antibiotic in pig farms can not only kill lots of Escherichia coli that is sensitive to antibiotic to make strains of drug resistance grow rapidly, but can also accelerate the drug resistnace process of sensitive Escherichia coli strains, especially, fodders added antibiotic can easily speed up drug resistance of bacteria, which is the same for different tire sows in a pig farms. there is a certain correlation between Drug-resistant bacteria and drug use in different pig farms.2. This paper also has inspected the resistant genes of bacteria with the primer of relative resistant genes made up of three antibiotics of aminoglycoside with high resistance, tetracycline and sulfonamide on the basis of the phenotype of drug susceptibility. The result reveals that a drug resistant gene can be found in each strain of resistant bacteria. The detection rate of drug resistance genes in aminoglycosides is59.3%,94.1%in tetracylines, and74.9%in sulfonamides. Sometimes several drug resistance genes can be detected, and its rate with one strain is16.5%. A strain of drug resistance genes positive bacteria are selected from Escherichia coli in different pig farms, which are amplified with PCR to tet(A), ant(3")-1a and Sul2. The test has chose a positive strain of Sull, tet(A) and ant(3")-1a from each batch of bacteria to sequence and make a comparison of the same resistant gene sequences of the same resistant genes which are amplified by each batch of bacteria. It is discovered that the homology is more than98%between the same drug resistance genes from various Escherichia coli, that is to say, there is little variability in resistance-genes’sequences and close affinity between resistant genes.