Drug-resistance and its mechanism of Escherichia coli isolates from environment of scaled pig farms

To investigate drug-resistance and its mechanism of Escherichia coli isolated from environment of scaled pig farms,31 strains of E.coli were randomly selected from the bacteria from six scaled pig farms and used for analysis of drug-resistance by susceptibility disk diffusion method and detection of qnrA and aac(6')-Ib gene by PCR,and one strain was picked for elimination test of resistance plasmid by high temperature-SDS method.The results showed that the isolated 31 strains appeared varying degrees of resistance to penicillin,tetracycline,lincomycin,erythromycin,roxithromycin and other antibiotics.And the drug-resistance gene of qnrA was not detected in all the strains,while the aac(6')-Ib gene existed in eight isolates.The strain could possess the susceptibility to aminoglycosides and quinolones by eliminating the plasmid with aac(6')-Ib gene.The results suggested that the clinical isolates of E.coli produced a wide range of resistance to the common antibiotics,and the plasmid with aac(6')-Ib gene in E.coli mediated the resistance to quinolones and aminoglycosides.