Impact of a Stewardship‐Initiated Restriction on Empirical Use of Ciprofloxacin on Nonsusceptibility of Escherichia coli Urinary Isolates to Ciprofloxacin

STUDY OBJECTIVE: To evaluate the impact of a stewardship-initiated restriction on empirical use of ciprofloxacin on the nonsusceptibility of Escherichia coli urinary isolates to ciprofloxacin over time while controlling for the use of other key antibiotics with gram-negative activity. DESIGN: Retrospective single-center study. SETTING: Large tertiary and quaternary care academic medical center. ISOLATES: Of 3714 E. coli urinary isolates. MEASUREMENTS AND MAIN RESULTS: The susceptibilities of the E. coli urinary isolates to ciprofloxacin, ceftriaxone, cefepime, piperacillin-tazobactam, meropenem, trimethoprim-sulfamethoxazole, and nitrofurantoin obtained over a 7-year period (January 1, 2006-December 31, 2012) from adult inpatients were evaluated for potential relationships with antibiotic use over time by using multiple variable regression analysis. After introduction of the restriction on empirical use of ciprofloxacin in the first quarter of 2011, ciprofloxacin use declined from 141.1-39.8 defined daily doses/1000 patient-days, and the percentage of E. coli isolates that were not susceptible to ciprofloxacin decreased from 41.5-32.8%. With all antibiotics evaluated included in the model, no apparent relationships were found between the percentage of E. coli isolates nonsusceptible to ciprofloxacin and antibiotic use. However, when nonsignificant variables were eliminated (p>0.20), ciprofloxacin use was found to be positively associated with the percentage of E. coli isolates nonsusceptible to ciprofloxacin (p=0.037), whereas ceftriaxone use was negatively associated (p=0.045). CONCLUSION: The restriction and subsequent reduction of ciprofloxacin use was found to have a positive effect on the susceptibility of E. coli urinary isolates to ciprofloxacin.