LAUSR

Abstract Background Optimal antimicrobial therapy for Enterococcus faecium (EFM) bacteremia in the solid-organ transplant (SOT) population is not well defined. Antimicrobial resistance, immunosuppression, and high mortality associated with EFM infections all pose serious threats. The purpose of this study was to describe the pharmacotherapy and outcomes of EFM bacteremia in SOT patients. Methods This was a single-center retrospective cohort of SOT patients with EFM bloodstream infection from 2013 to 2018. Susceptibility of ampicillin (AMP), vancomycin (VAN), linezolid (LZD), and daptomycin (DAP) against EFM were reported as MIC90 when available. The primary outcome, 30-day all-cause mortality, was assessed in bivariate analysis to identify potential risk factors. Secondary outcomes included inpatient mortality and development of DAP nonsusceptibility (DNS). Results Forty-four unique cases representing 40 patients were included in the analysis. The median age was 62.5 years and liver (65.9%), intestine (20.5%), and kidney (11.4%) were the most common organs transplanted. The MIC90 of VAN, DAP, and LZD of initial isolates collected were >32 mg/L, 4 mg/L, and 2 mg/L, respectively; all were AMP resistant. The median durations of hospitalization and intensive care stay were 29 days and 17.5 days, respectively. Most patients had indwelling central lines (81.8%) at the time of bacteremia; intra-abdominal abscesses/fluid collections were present in 45.5% of patients and 9.1% had endocarditis. The most common definitive antimicrobial regimens were DAP plus β-lactam (45.5%), DAP monotherapy (18.2%), and LZD 600 mg Q12H (25.0%). The mean initial and definitive DAP doses were 8.1 ± 1.6 and 8.9 ± 1.7 mg/kg actual body weight, respectively. Among subjects that received DAP, 21.9% developed DNS. Inpatient mortality was 39.5% and 30-day mortality was 27.3%. Mortality at 30-days was greater in patients with high-grade bacteremia (40.7 vs. 5.9%, P = 0.01) and receipt of DAP <10 mg/kg as the first active antibiotic (42.9 vs. 13.0%, P = 0.03). Conclusion Inadequate DAP dosing for EFM bacteremia may be associated with mortality in the SOT population. Larger, matched analyses are necessary to determine the impact of optimized pharmacodynamics. Disclosures S. L. Davis, Achaogen: Scientific Advisor, Consulting fee. Allergan: Scientific Advisor, Consulting fee. Melinta: Scientific Advisor, Consulting fee. Nabriva: Scientific Advisor, Consulting fee. Zavante: Scientific Advisor, Consulting fee.