244. Impact of Antibiotic Susceptibility Reporting on Broad-Spectrum Antibiotic Use in Serratia and Morganella Bacteremia

Abstract

BackgroundThe increase in antibiotic resistance highlights the necessity of antimicrobial stewardship strategies to guide antibiotic de-escalation. Retrospective data suggest noninferior outcomes with carbapenem-sparing regimens in AmpC-β-lactamase producing Serratia marcescens and Morganella morganii bacteremia. To minimize broad-spectrum (BS) antibiotic use, our microbiology laboratory recently changed the antibiotic susceptibility reporting for these organisms in blood cultures to include narrow spectrum third-generation cephalosporins. We sought to assess the impact of this change on BS antibiotic use and clinical outcomes. We also sought to compare outcomes between BS and narrow spectrum antibiotics in bacteremia caused by these organisms.MethodsWe retrospectively reviewed all adult patients with Serratia marcescens or Morganella morganii in blood culture 2 years pre- and post-change of susceptibility reporting from February 13–February 17. Exclusion criteria included: (1) >1 pathogen found in blood culture, (2) no antibiotic treatment given, (3) death within 48 hours of positive blood culture. The rates of broad-spectrum antibiotic use between the two periods were compared. Secondary outcomes evaluated included in-hospital mortality, clinical response, and microbiologic success.ResultsA total of 112 patients were screened. There were 30 patients prechange and 46 patients postchange of reporting included after exclusions. Patients in both groups had similar baseline characteristics. There was a decrease in BS antibiotic use postchange (70% to 54.3%) although this was not statistically significant (P = 0.172). Specifically, cefepime use had decreased significantly from 46.7% to 6.5% (P < 0.001). No significant differences were observed in secondary outcomes between patients pre- and postchange. The use of BS antibiotics was significantly associated with higher in-hospital mortality (100% vs. 55.2%, P = 0.010). No mortality was observed in patients on narrow spectrum antibiotics.ConclusionBS antibiotic use, specifically cefepime, was reduced after susceptibility reporting changes without affecting outcomes in Serratia marcescens and Morganella morganii bacteremia. This demonstrates the potential role of selective susceptibility reporting in antimicrobial stewardship.Disclosures All authors: No reported disclosures.