Relationship between classIintegrons and gene cassettes and multiple drug resistance of Escherichia coli isolates in chickens
A total of 184 isolates of Escherichia coli were identified from four chicken farms in Hefei district of Anhui Province. Prevalence of classⅠ integrons and gene cassettes was detected using PCR. Susceptibilities of the E. coli isolates to 16 antimicrobials were determined using broth micro-dilution method. The PCR results showed that 91 of 184(49.45%) isolates harbored class Ⅰ integrons in which 70 contained gene cassettes(45dfrA1-tnpAIS26-aadA1, 16 dfrA2-aadA, and 9 dfrA1-aadA1). Twenty one isolates did not carry gene cassettes.Susceptibility test showed that drug resistance rates of 184 E. coli isolates to 16 antimicrobials ranged from 2.17%to 97.83%. The rate of drug resistance to three and more antimicrobials was 97.8%. There was a significant difference in drug resistance between isolates with and without integrons, indicating that multiple drug resistance of E. coli is correlated with the presence of integrons.