J.M. FAIRBROTHER, Université de Montréal S. BEKAL-SI ALI, Biotechnology Research Institute F. SANSCHAGRIN, Université Laval R.C. LEVESQUE, Université Laval R. BROUSSEAU, Biotechnology Research Institute L. MASSON, Biotechnology Research Institute S. LARIVIÈRE, Université de Montréal J. HAREL, Université de Montréal
Title
Patterns of Antimicrobial Resistance Genes and Integron Carriage among Enterotoxigenic Escherichia coli O149: K91 Isolated from Postweaning Pigs over the Last Two Decades
Abstract Text
With the worldwide progressive increase in antimicrobial resistance of enterotoxigenic Escherichia coli (ETEC) strains, treatment of postweaning diarrhea has become difficult. The objective was to analyze the distribution of antimicrobial resistance genes within ETEC isolated from pigs between 1978 and 2000. One hundred eighteen ETEC strains collected in Québec from pigs with postweaning diarrhea were tested for antimicrobial susceptibility by disc diffusion. Polymerase chain reaction was performed using primers corresponding to 29 genes found in antimicrobial resistance families and two primer sets used to detect the 3'-conserved segment of the class 1 integron and the length of the variable region (VR). Using amplicons as probes, colony hybridization was performed. Comparisons of association between resistance genes were tested by using the Pearson chi-square's exact test. Most ETEC strains were resistant to sulfonamides and tetracycline whereas resistance to cephalosporines was absent throughout this study. An increase in the number of chloramphenicol resistant strains and multiresistant strains was observed over time. Phenotypic resistance was associated with many different genes. In the studied period, some genes or associations of genes appeared whereas other genes were less frequently observed. Resistance genes different from those found in less recent isolates appeared in more recent isolates. The association of tem with shv as well as tet(A) with tet(C) and dhfrI with dhfrXV genes was demonstrated. Sixty-three percent of the strains possessed a class 1 integron. Four different VR were amplified corresponding to aminoglycoside and trimethoprim resistance genes. A new distribution of resistance genes was observed over time with an increase in multigene resistance correlating with the observed phenotypic multiresistance among ETEC O149: K91.
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