Emergence of fluoroquinolone resistance in outpatient urinary Escherichia coli isolates.

Background: Because of high rates of trimethoprim-sulfamethoxazole resistance in Escherichia coli, Denver Health switched to levofloxacin as the initial therapy for urinary tract infections (UTIs) in 1999. We evaluated the effects of that switch 6 years later.

Methods: Levofloxacin prescriptions per 1000 outpatient visits and levofloxacin resistance in outpatient E.