Characterization of the variable region in the class 1 integron of antimicrobial-resistant Escherichia coli isolated from surface water

Abstract

Fecal bacteria are considered to be a potential reservoir of antimicrobial resistance genesin the aquatic environment and could horizontally transfer these genes to autochthonousbacteria when carried on transferable and/or mobile genetic elements. Such circulation ofresistance genes constitutes a latent public health hazard. The aim of this study was to char-acterize the variable region of the class 1 integron and relate its genetic content to resistancepatterns observed in antimicrobial-resistant Escherichia coli isolated from the surface watersof Patos Lagoon, Southern Brazil. Genetic diversity of the isolates and presence of the qacE 1gene, which confers resistance to quaternary ammonium compounds, were also investi-gated. A total of 27 isolates were analyzed. The variable region harbored dfrA17, dfrA1 anddfrA12 genes, which confer resistance to trimethoprim, and aadA1, aadA5 and aadA22 genesthat encode resistance to streptomycin/spectinomycin. Most of the isolates were consideredresistant to quaternary ammonium compounds and all of them carried the qacE 1 gene atthe 3 conserved segment of the integron. ERIC-PCR analyses of E. coli isolates that presentedthe integrons showed great genetic diversity, indicating diverse sources of contamination inthis environment. These results suggest that fecal bacteria with class 1 integrons in aquaticenvironments are potentially important reservoirs of antibiotic-resistance genes and maytransfer these elements to other bacteria that are capable of infecting humans.