Do Inpatient Antimicrobial Stewardship Programs Help Us in the Battle Against Antimicrobial Resistance?

Background. Antibiotic stewardship programs (ASPs) have demonstrated success at reducing costs, yet there is limited quality evidence of their effectiveness in reducing infections of high-profile drug-resistant organisms. Methods. This retrospective, cohort study included all Kaiser Permanente Southern California (KPSC) members aged >= 18 years hospitalized in 9 KPSC hospitals from 1 January 2008 to 31 December 2016. We measured the impact of staggered ASP implementation on consumption of 18 ASP-targeted antibiotics using generalized linear mixed-effects models. We used multivariable generalized linear mixed-effects models to estimate the adjusted effect of an ASP on rates of infection with drug-resistant organisms. Analyses were adjusted for confounding by time, cluster effects, and patient- and hospital-level characteristics. Results. We included 765 111 hospitalizations (288 257 pre-ASP, 476 854 post-ASP). By defined daily dose, we found a 6.1% (-7.5% to -4.7%) overall decrease antibiotic use post-ASP; by days of therapy, we detected a 4.3% (-5.4% to -3.1%) decrease in overall use of antibiotics. The number of prescriptions increased post-ASP (1.04 [1.03-1.05]). In adjusted analyses, we detected an overall increase in vancomycin-resistant enterococci infections post-ASP (1.37 [1.10-1.69]). We did not detect a change in the rates of extended-spectrum beta-lactamase, carbapenem-resistant Enterobacteriaceae, and multidrug-resistant Pseudomonas aeruginosa infections post-ASP. Conclusions. ASPs with successful reductions in consumption of targeted antibiotics may not see changes in infection rates with antibiotic-resistant organisms in the 2 to 6 years post-implementation. There are likely differing timescales for reversion to susceptibility across organisms and antibiotics, and unintended consequences from compensatory prescribing may occur.