1509. Efficacy of Lefamulin Against Staphylococcus aureus - Induced Bacteremia in a Neutropenic and Immunocompetent Murine Model
Session: Poster Abstract Session: Preclinical Study with New Antibiotics and Antifungals
Friday, October 6, 2017
Room: Poster Hall CD
  • Poster_ID Week 2017_Vivo Bacteremia_Final.pdf (300.9 kB)
  • Background:

    S. aureus (SA) is a major human pathogen that causes invasive, clinical infections including bacteremia.  Lefamulin (LEF) is the first semi-synthetic, pleuromutilin antibiotic for IV and oral use in humans. LEF is currently in Phase 3 trials for the treatment of community-acquired bacterial pneumonia (CABP).  LEF specifically inhibits bacterial protein synthesis by binding to the peptidyl transferase center (PTC) via four H-bonds and other interactions at the A- and P-site resulting in an “induced fit.”  LEF has been shown to be highly active against bacterial pathogens causing bacteremia, including SA.  This study investigated the efficacy of LEF and comparators against SA in a neutropenic and immunocompetent murine bacteremia model.  


    Experimentally induced MSSA bacteremia (inoculum ~2x107 CFU/mouse) was established in immunocompromised and immunocompetent mice. Infected mice received a single subcutaneous dose of either LEF or comparator (Table 1) 1 h post-inoculation, mimicking human therapeutic exposures. A control group of infected mice were sacrificed directly before treatment to establish a baseline CFU count and comparison with the bacterial load of treated animals 24 h post drug administration.


    Irrespective of the immune status, LEF showed superior efficacy to linezolid (LZD) and tigecycline (TGC) against MSSA, reducing the bacterial burden more than 4 log10 CFU/ml within 24 h (Table 1).  A comparable reduction of bacterial burden was observed between LEF and daptomycin (DAP) or vancomycin (VAN) treatment.


    LEF showed comparable therapeutic outcome to DAP or VAN in this acute experimental infection model, while showing superior killing as compared to LZD or TGC. The efficacy of LEF was maintained under neutropenic conditions with >4log10 ΔCFU/ml at clinically relevant exposures. This study supports continued evaluation of LEF for as a potential treatment of staphylococcal bacteremia. 

    Evelin Fischer, MSc, Barbara C. Kappes, Ing and Wolfgang W. Wicha, MS, Nabriva Therapeutics AG, Vienna, Austria


    E. Fischer, Nabriva Therapeutics AG: Employee and Shareholder , Salary

    B. C. Kappes, Nabriva Therapeutics AG: Employee and Shareholder , Salary

    W. W. Wicha, Nabriva Therapeutics AG: Employee and Shareholder , Salary

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 4th with the exception of research findings presented at the IDWeek press conferences.