infection control and hospital epidemiology april 2012, vol. 33, no. 4 original article Audit and Feedback to Reduce Broad-Spectrum Antibiotic Use among Intensive Care Unit Patients: A Controlled Interrupted Time Series Analysis Marion Elligsen, BScPhm; 1 Sandra A. N. Walker, Sc, BScPhm, Pharm D, FCSHP; 1,2,4 Ruxandra Pinto, PhD; 3 Andrew Simor, MD, FRCPC; 4,5 Samira Mubareka, MD, FRCPC; 3,4,5 Anita Rachlis, MD, FRCPC; 4,5 Vanessa Allen, MD, FRCPC; 4,5,6 Nick Daneman, MD, MSc, FRCPC 3,4,5,7 objective. We aimed to rigorously evaluate the impact of prospective audit and feedback on broad-spectrum antimicrobial use among critical care patients. design. Prospective, controlled interrupted time series. setting Single tertiary care center with 3 intensive care units. patients and interventions. A formal review of all critical care patients on their third or tenth day of broad-spectrum antibiotic therapy was conducted, and suggestions for antimicrobial optimization were communicated to the critical care team. outcomes. The primary outcome was broad-spectrum antibiotic use (days of therapy per 1000 patient-days; secondary outcomes included overall antibiotic use, gram-negative bacterial susceptibility, nosocomial Clostridium difficile infections, length of stay, and mortality. results. The mean monthly broad-spectrum antibiotic use decreased from 644 days of therapy per 1,000 patient-days in the preinter- vention period to 503 days of therapy per 1,000 patient-days in the postintervention period ( ); time series modeling confirmed P ! .0001 an immediate decrease ( standard error) of days of therapy per 1,000 patient-days ( ). In contrast, no changes were 119  37.9 P p .0054 identified in the use of broad-spectrum antibiotics in the control group (nonintervention medical and surgical wards) or in the use of control medications in critical care (stress ulcer prophylaxis). The incidence of nosocomial C. difficile infections decreased from 11 to 6 cases in the study intensive care units, whereas the incidence increased from 87 to 116 cases in the control wards ( ). Overall gram- P p .04 negative susceptibility to meropenem increased in the critical care units. Intensive care unit length of stay and mortality did not change. conclusions. Institution of a formal prospective audit and feedback program appears to be a safe and effective means to improve broad-spectrum antimicrobial use in critical care. Infect Control Hosp Epidemiol 2012;33(4):354-361 Affiliations: 1. Department of Pharmacy, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; 2. Leslie L. Dan Faculty of Pharmacy,University of Toronto, Toronto, Ontario, Canada; 3. Sunnybrook Research Institute, Toronto, Ontario, Canada; 4. Department of Microbiology and Division of Infectious Diseases, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; 5. Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada; 6. Public Health Ontario, Toronto, Ontario, Canada; 7. Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada. Received September 23, 2011; accepted December 22, 2011; electronically published March 15, 2012.  2012 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2012/3304-0007$15.00. DOI: 10.1086/664757 Inexorable increases in antibiotic use in hospitals over the past few decades have driven increases in rates of resistance among hospital-acquired pathogens. 1,2 However, up to half of antibiotic use in hospitals is unnecessary or inappropriate, suggesting that it still may be possible to reverse this trend through the promotion of more judicious antimicrobial use. 3,4 In response to this crisis of antibiotic overuse and increases in the prevalence of antibiotic resistance, North American and European infectious diseases societies have published guidelines for the introduction of multidisciplinary hospital antimicrobial stewardship programs. 4,5 An antimicrobial stewardship program aims to reduce inappropriate antimi- crobial use while optimizing antimicrobial drug selection, dosing, route, and duration of therapy to maximize clinical cure or prevention of infection and to limit antibiotic costs, adverse drug events, cases of Clostridium difficile infection, and selection of antibiotic-resistant organisms. 4 Although antibiotic stewardship programs should strive to improve rational antimicrobial use throughout a facility, the greatest potential impact may lie in the critical care unit, 6 because this is the location in which, in most hospitals, an- timicrobial use and antimicrobial resistance is the greatest. 7,8 However, the obstacles to antibiotic stewardship are signifi- cant in this vulnerable and complex patient population. 6