2436. Use of Piperacillin/Tazobactam vs. Cefepime or Carbapenem for Infections Due to Serratia, Citrobacter, or Enterobacter

BACKGROUND: AmpC β-lactamases are an inducible type of resistance not readily detected by rapid diagnostics. Carbapenems and cefepime are considered the standard of care antibiotics for organisms likely to harbor the AmpC gene. However, data on the efficacy of piperacillin–tazobactam are lacking. The objective of this study was to compare clinical outcomes between piperacillin–tazobactam (PTZ) vs. cefepime (FEP) or a carbapenem (CAR) for pneumonia or bacteremia caused by Serratia, Citrobacter, or Enterobacter species. METHODS: This single-center retrospective cohort study evaluated adult patients admitted between January 2007 to October 2017 with either a blood culture or bronchoalveolar lavage (BAL) positive for either S. marcescens, C. freundii, E. cloacae, or E. aerogenes. Data came from the University of Kentucky Microbiological Laboratory and Center for Clinical and Translational Science (CCTS) Data Bank. Patients included must have received PTZ, FEP, or CAR for at least 72 hours. Patients were excluded if they received other antibiotics as definitive therapy (defined as antibiotic used for majority of treatment), Gram-negative combination therapy for more than 72 hours, had isolates resistant to definitive antibiotic therapy, or expired within 48 hours of admission. RESULTS: A total of 321 patients were identified (154 PTZ and 167 FEP/CAR). Demographics were similar between the two groups, although patients treated with PTZ tended to be slightly older and admitted to the ICU. More patients in the PTZ group (56.5%) had positive BAL cultures compared with the FEP/CAR group (40.7%) (P = 0.0047). The most common pathogen isolated among both PTZ and FEP/CAR patients was Enterobacter spp. (60.4% and 56.3%, respectively) (P = 0.5040). Overall, 11% of PTZ patients died in-hospital compared with 12.6% of FEP/CAR patients (P = 0.6704). In terms of 30-day readmission rate, 2.6% of PTZ patients and 2.4% of FEP/CAR patients were readmitted within 30 days of discharge (P = 0.9076). CONCLUSION: Compared with FEP/CAR, patients with Serratia, Citrobacter, or Enterobacter bacteremia or pneumonia treated with PTZ did not show a significant difference in terms of in-hospital mortality and 30-day readmission rate. DISCLOSURES: All authors: No reported disclosures.