The role of horizontal gene transfer in the spread of trimethoprim-sulfamethoxazole resistance among uropathogenic Escherichia coli in Europe and Canada.
OBJECTIVE
To describe the distribution of trimethoprim-sulfamethoxazole resistance genes and the role of horizontal gene transfer and clonal expansion in recent increases of antibiotic resistance rates among uropathogenic Escherichia coli in Europe and Canada.


METHODS
We identified antibiotic resistance alleles sul1, sul2, sul3 and dfr along with type 1 and type 2 integrons among 350 uropathogenic E. coli isolates from a cross-sectional study of acute, uncomplicated, community-acquired urinary tract infections in 16 western European countries and Canada (ECOSENS).


RESULTS
Trimethoprim resistance gene distributions showed no regional dependency (P = 0.84). The most common trimethoprim resistance gene was dfrA1, which occurred in 37.9% of dfr containing isolates. Similarly, the sulfamethoxazole resistance gene distributions did not vary significantly by region (P = 0.20). sul2, the most common sulfamethoxazole resistance gene, was found in 77.9% of sulfamethoxazole-resistant isolates. The distribution of type 1 and type 2 integrons varied slightly by region (P = 0.04) with type 1 integrons being the more common (85.9%). We observed 34 combinations of the sul genes, dfr genes and integron types; the most common combinations were broadly disseminated across every region examined.


CONCLUSIONS
Horizontal gene transfer plays a larger role than clonal expansion in the increase of trimethoprim-sulfamethoxazole resistance levels in Europe and Canada.
Blahna
Matthew T
MT
Department of Epidemiology, University of Michigan, School of Public Health, Ann Arbor, 48109, USA.
Zalewski
Christy Ann
CA
Reuer
Jennifer
J
Kahlmeter
Gunnar
G
Foxman
Betsy
B
Marrs
Carl F
CF
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002170:Canada / Q000453:epidemiology; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology; D005060:Europe / Q000453:epidemiology; D022761:Gene Transfer, Horizontal; D006801:Humans; D032023:Integrons; D008826:Microbial Sensitivity Tests; D013420:Sulfamethoxazole / Q000494:pharmacology*; D014296:Trimethoprim Resistance; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology*; D014552:Urinary Tract Infections / Q000453:epidemiology / Q000382:microbiology
D000900:Anti-Bacterial Agents; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D013420:Sulfamethoxazole