Widespread Distribution of Urinary Tract Infections Caused by a Multidrug-ResistantEscherichia coliClonal Group

Abstract
The management of urinary tract infections is complicated by the increasing prevalence of antibiotic-resistant strains of Escherichia coli. We studied the clonal composition of E. coli isolates that were resistant to trimethoprim–sulfamethoxazole from women with community-acquired urinary tract infections. Prospectively collected E. coli isolates from women with urinary tract infections in a university community in California were evaluated for antibiotic susceptibility, O:H serotype, DNA fingerprinting, pulsed-field gel electrophoretic pattern, and virulence factors. The prevalence and characteristics of an antibiotic-resistant clone were evaluated in this group of isolates and in those from comparison cohorts in Michigan and Minnesota. Fifty-five of the 255 E. coli isolates (22 percent) from the California cohort were resistant to trimethoprim–sulfamethoxazole as well as other antibiotics. There was a common pattern of DNA fingerprinting, suggesting that the isolates belonged to the same clonal group (clonal group A), in 28 of 55 isolates with trimethoprim–sulfamethoxazole resistance (51 percent) and in 2 of 50 randomly selected isolates that were susceptible to trimethoprim–sulfamethoxazole (4 percent, P E. coli strains with resistance to trimethoprim–sulfamethoxazole. The widespread distribution and high prevalence of E. coli clonal group A have major public health implications.