Correlation between Antimicrobial Resistance and Integrons of Escherichia coli Strains Isolated from Bovine Mastitis Milk Samples

This study investigated the correlation between antimicrobial resistance of Escherichia coli strains isolated from bovine mastitis milk samples and the integrons.After acquirement of the antimicrobial resistance patterns,integrase gene was amplified by PCR using degenerate primers.The integrons were confirmed by restriction fragment length polymorphism(RFLP) analysis of positive PCR products,then integrated gene cassettes were examined.The incidence of class Ⅰ integron in the 80 strains of E.coli was 46.25%(37/80).All integrons were revealed as class Ⅰ integron.Neither class Ⅱ nor class Ⅲ integron was detected.Thirty-one strains carried the integrated gene cassttes were detected in thirty-seven integron-positive srtains.The class Ⅰ integron was prevalent in strains which were resistant to more than seven antimicrobials.ClassⅠintegrons harbored dfr and aadA gene cassettes confered resistance to trimethoprim and streptomycin,respectively.The order of main inserted gene cassettes was dfrA17-aadA5.There was a good correlation between integron carried and the multi-resistance,but the antimicrobial resistance patterns did not consist with the gene cassettes.