Purpose. Class 1 integrons are among the main vehicles that facilitate the spread of antibiotic-resistance genes, with serious public health consequences. The aim of this cross-sectional study was to investigate the presence of class 1 integrons and to characterize their variable regions, as well as the antimicrobial resistance profiles and phylogenetic groups of a collection of Escherichia coli isolates recovered from healthy subjects (n=42) and those with urinary infection (n=40).Methodology. The methods used included PCR, sequencing and antimicrobial susceptibility testing.Results. PCR screening for the integrase gene (intI1) revealed a higher incidence of class 1 integrons in uropathogenic E. coli (65 %, UPEC) than in commensal isolates (11.9 %). Eight of 31 intI1-positive isolates, all of them UPEC, harboured empty integrons. The variable regions of the other 23 contained gene cassettes encoding resistance to b-lactams (blaOXA-1), aminoglycosides (aadA1 and aadA5), trimethoprim (dfrA1 and dfrA17) and an ORF. To our knowledge this is the first report of an ORF identified as a putative phage tail protein associated with a class 1 integron. The aadA1 and dfrA17-addA5 arrays prevailed in commensal E. coli and UPEC, respectively. UPEC isolates were highly resistant to the antimicrobials tested, in contrast to commensal isolates. The E. coli isolates carrying gene cassettes associated with class 1 integrons were found to be unrelated to any phylogroup or multiresistance.Conclusion. Co-resistance to clinically relevant fluoroquinolone and trimethoprim-sulfamethazole in all UPEC isolates is a cause for concern. These results expand the current knowledge of gene cassettes in both commensal and pathogenic E. coli.
The integron-gene cassette system has typically been associated with antibiotic-resistant pathogens. However, the diversity of gene cassettes and the abundance of class 1 integrons outside of the clinical context are not fully explored. Primers targeting the conserved segments of attC recombination sites were used to amplify gene cassettes from the sediment of the Mina stream, which exhibited a higher degree of stress to metal pollution in the dry season than the rainy season. Of the 143 total analyzed sequences, 101 had no matches to proteins in the database, where cassette open reading frames could be identified by homology with database entries. There was a predominance of sequences encoding essential cellular functions. Each season that was sampled yielded a specific pool of gene cassettes. Real-time PCR revealed that 8.5 and 41.6 % of bacterial cells potentially harbored a class 1 integron in the rainy and dry seasons, respectively. In summary, our findings demonstrate that most of the gene cassettes have no ascribable function and, apparently, historically metal-contaminated sediment favors the maintenance of bacteria containing the intI1 gene. Thus, the diversity of gene cassettes is far from being fully explored deserving further attention.
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