Antimicrobial resistance and integron-gene cassette detection of Escherichia coli isolates from diarrhea dogs

Objective  To investigate the antimicrobial resistance of Escherichia coli from diarrhea dogs and the distribution of integron-gene cassettes in E. coli.

Method  The Kirby-Bauer disc diffusion method was used to test the susceptibility of 30 strains of E.coli against 19 antimicrobial agents. PCR was used to detect the integrase genes(class I, II, III) in E.coli isolates. We further detected if E.coli isolates carrying integrase genes also carried the sul1, qacEΔ1 genes and gene cassettes in variable regions.

Result  Thirty isolates showed different levels of resistance to 19 antimicrobial agents with 18 kinds of resistant spectrum. E.coli isolates had high resistance to amoxicillin, ampicillin, tetracycline and doxycycline with drug resistance rates of 90.00%, 83.33%, 66.67% and 63.33%, respectively, while had low resistance to the other antimicrobials with drug resistance rates below 14.00%. Eleven out of 30 isolates were found to carry class I integrase, sul1 and qacEΔ1 genes, and class II or class III integrase gene was not detected. Among the isolates carrying class I integrase gene, the dfrA12+orfF+aadA2 gene cassette of 1 879 bp length was successfully amplified from two isolates.

Conclusion  E.coli isolates from diarrhea dogs show different levels of resistance to antimicrobial agents. Antimicrobial resistance that mediated by gene cassettes is partially related to the resistant phenotype of E.coli. Class I integron shows a certain relationship with the antimicrobial resistance of E.coli.