Impact of antimicrobial stewardship interventions on Clostridium difficile infection and clinical outcomes: segmented regression analyses.

Background: Antimicrobial exposure is associated with increased risk of Clostridium difficile infection (CDI), but the impact of prescribing interventions on CDI and other outcomes is less clear.

Objectives: To evaluate the effect of an antimicrobial stewardship intervention targeting high-risk antimicrobials (HRA), implemented in October 2008, and to compare the findings with similar studies from a systematic review.

Methods: All patients admitted to Medicine and Surgery in Ninewells Hospital from October 2006 to September 2010 were included. Intervention effects on HRA use (dispensed DDD), CDI cases and mortality rates, per 1000 admissions per month, were analysed separately in Medicine and Surgery using segmented regression of interrupted time series (ITS) data. Data from comparable published studies were reanalysed using the same method.

Results: Six months post-intervention, there were relative reductions in HRA use of 33% (95% CI 11-56) in Medicine and 32% (95% CI 19-46) in Surgery. At 12 months, there was an estimated reduction in CDI of 7.0 cases/1000 admissions [relative change -24% (95% CI - 55 to 6)] in Medicine, but no change in Surgery {estimated 0.1 fewer cases/1000 admissions [-2% (95% CI - 116 to 112)]}. Mortality reduced throughout the study period, unaffected by the intervention. In all six comparable studies, HRA use reduced significantly, but reductions in CDI rates were only statistically significant in two and none measured mortality. Pre-intervention CDI rates and trends influenced the intervention effect.

Conclusions: Despite large reductions in HRA prescribing and reductions in CDI, demonstrating real-world impact of stewardship interventions remains challenging.