[Relationship between antibiotic resistance and integrons of Escherichia coli isolated from food]

To investigate the relationship between antibiotic resistance of Escherichia coli strains isolated from food and the integrons they harbored.

PCRs amplifying intI gene and the variable region between the conserved segments (CS-PCR) were performed for class1, class2, and class 3 integron. And the integron content of every isolate was characterized by RFLP analysis and sequencing.

19 of 50 isolates were identified as being positive for integrase 1 gene in the genomic DNA, of which 13 had detectable amplification products for CS-PCR. Two E. coli isolates had class 2 integron. All the integron-positive strains were resistance to at least 4 antibiotics. Most of the gene cassettes integrated in the integrons conferred resistance against trimethoprim and streptomycin-spectinomycin, and the integrons with the dfr17-aadA5 gene cassettes combination were predominant. Some strains with different antibiotic resistance profile or plasmid profile were found to have the same integron.

There was a good correlation between Integron-carrying and the antibiotic resistance of Escherichia coli strains isolated from food, but in terms of an individual strain, its antibiotic profile was not consistent with the gene cassettes of the integron it harbored.