Results
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