Effect of reduced use of quinolones on the observed resistance rates in E.coli

Abstract number: O464

Willemsen I., Cooper B., van Buitenen C., Winter M., Kluytmans J.

Objectives: To determine the effects of multiple interventions that reduced the use of Quinolones, on the observed resistance of E. coli in a teaching hospital.

Methods: During a prospective study, from 2005 through 2007, 4 interventions to improve the use of quinolones (QUIN) were executed. First, a switch from intravenous- to oral medication (01–2006); second, education programs for interns/residents and physicians and the release of a new antimicrobial formulary (05–2006); third, a restriction note was printed on all laboratory rapports (10–2006) and fourth, active monitoring and giving feedback on prescriptions (01–2007). Susceptibility patterns for E. coli including ciprofloxacin, cefuroxim, ceftazidim, co-trimoxazole and tobramycin from hospitalised patients were analyzed starting in 2004. Statistical analyses were performed using segmented Poisson regression models to look at effect of interventions on resistance (both sudden stepwise changes and changes in trends). Bayesian model averaging was used to account for model uncertainty.

Results: Before the start of the interventions the resistance rate was increasing by an average of 2.6% per year. The interventions resulted in a significant reduction of QUIN use from on average 550 Prescribed Daily Doses to 350 PDD per month. In the best fitting Poisson model for the resistance data, a significant stepwise decrease was found to be associated with interventions 2 and 4. However, there was substantial uncertainty in the model choice, and after accounting for this there was no conclusive evidence in support of any particular intervention, although there was evidence that at least one of the interventions was associated with the observed reduction in resistance. There were no stepwise decreases or decreasing trends in resistance rates to other antimicrobials during the study period.

Conclusions: This study found that targeted interventions that reduce the use of QUIN were associated with a decrease of the QUIN resistance rate in E. coli.