RESUMEN
Antimicrobial resistance is a growing concern especially in many remote northern communities of Canada where antimicrobials are liberally used. In this study, 1418 Escherichia coli urinary tract infection (UTI) isolates, obtained over a 2.5-year period (October 2005-March 2008), from 3 remote northern sites in Saskatchewan, Canada, were identified. Antimicrobial susceptibility testing of the first 544 clinically significant isolates revealed high prevalence of resistance to trimethoprim-sulfamethoxazole (TMP-SXT) (30.7%). Pulsed-field gel electrophoresis (PFGE) of 165 TMP-SXT-resistant isolates revealed a heterogeneous population. Multilocus sequence typing identified 7 STs from 9 identified PFGE clusters, which included separate PFGE clusters of fluoroquinolone-resistant and -susceptible ST131 isolates. The majority of TMP-SXT-resistant isolates (85.5%) were found to carry class 1 integrons, and plasmids from 62 (81%) of 77 representative isolates were successfully transformed into E. coli DH10B. Overall, ampicillin was the most common plasmid-encoded resistance phenotype transferred with TMP-SXT at 60% (37/62). Further characterization of 52 plasmids by restriction fragment length polymorphism and replicon typing revealed the presence of many plasmid lineages, suggesting that the elevated rates of TMP-SXT resistance in these communities are most likely attributed to the horizontal transfer of class 1 integrons. Results from this study emphasize the importance of continued surveillance of remote northern communities in order to optimize the efficacy of empiric UTI treatment.