Clonal groups and the spread of resistance to trimethoprim-sulfamethoxazole in uropathogenic Escherichia coli.
BACKGROUND
Antibiotic resistance is increasingly complicating the management of urinary tract infection. We investigated the extent to which a group of Escherichia coli called clonal group A (CGA), which is associated with resistance to trimethoprim-sulfamethoxazole (TMP-SMZ), accounted for TMP-SMZ resistance among a prospectively collected set of uropathogenic and rectal E. coli isolates from a university population in Michigan.


METHODS
Resistant and susceptible uropathogenic E. coli isolates (45 each) and 79 randomly selected rectal E. coli isolates were evaluated for CGA status by use of 2 definitions of this group-- the enterobacterial repetitive intergenic consensus sequence 2 (ERIC2)-polymerase chain reaction (PCR) pattern A fingerprint and the C288T single nucleotide polymorphism (SNP) in the fumC gene. We compared virulence gene profiles and molecular mechanisms of resistance to TMP-SMZ between isolates classified as CGA by both approaches to better characterize the relationship between isolates.


RESULTS
Of the 45 isolates that exhibited ERIC2-PCR pattern A, one-half (23 of 45) were resistant to TMP-SMZ, and 16 contained the C288T SNP. The pattern A isolates were diverse, exhibiting multiple mechanisms of resistance to TMP-SMZ and various combinations of virulence factors. C288T SNP isolates showed less variation, with 15 of 16 resistant to TMP-SMZ and a 1.8-kb class I integron bearing the dfrA17 gene present in 14 of 15 resistant isolates. Twelve of 16 exhibited the same combination of virulence genes. Pulsed-field gel electrophoresis patterns for these 12 isolates were unique.


CONCLUSIONS
CGA, as defined by the fumC C288T SNP, appears to be distantly clonal but is not an outbreak-related group. The widespread group has likely evolved through lateral transfer of genes conferring virulence and antibiotic resistance.
France
Anne Marie
AM
Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI 48109, USA.
Kugeler
Kiersten M
KM
Freeman
Alison
A
Zalewski
Christy Ann
CA
Blahna
Matthew
M
Zhang
Lixin
L
Marrs
Carl F
CF
Foxman
Betsy
B
D000293:Adolescent; D000328:Adult; D016172:DNA Fingerprinting; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000145:classification* / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity; D005260:Female; D006801:Humans; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology*; D014552:Urinary Tract Infections / Q000188:drug therapy / Q000382:microbiology*; D014774:Virulence
D015662:Trimethoprim, Sulfamethoxazole Drug Combination