Model-informed dose optimisation of polymyxin-rifampicin combination therapy against multidrug-resistant Acinetobacter baumannii

•Polymyxin B and rifampicin can synergistically kill Acinetobacter baumannii.•The semi-mechanistic pharmacokinetic/pharmacodynamic model aids dose optimisation.•Simulations with clinically utilised regimens confirmed its therapeutic potential. Antimicrobial resistance is a major global threat. Becau...

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Bibliographic Details
Published in:International journal of antimicrobial agents 2023-09, Vol.62 (3), p.106902-106902, Article 106902
Main Authors: Zhao, Jinxin, Zhu, Yan, Han, Mei-Ling, Lu, Jing, Yu, Heidi H., Wickremasinghe, Hasini, Zhou, Qi Tony, Bergen, Phillip, Rao, Gauri, Velkov, Tony, Lin, Yu-Wei, Li, Jian
Format: Article
Language:English
Subjects:
Model-informed dose optimisation
Multidrug-resistant Acinetobacter baumannii
Pharmacokinetics/pharmacodynamics
Polymyxin
Rifampicin
Semi-mechanistic PK/PD model
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Summary:•Polymyxin B and rifampicin can synergistically kill Acinetobacter baumannii.•The semi-mechanistic pharmacokinetic/pharmacodynamic model aids dose optimisation.•Simulations with clinically utilised regimens confirmed its therapeutic potential. Antimicrobial resistance is a major global threat. Because of the stagnant antibiotic pipeline, synergistic antibiotic combination therapy has been proposed to treat rapidly emerging multidrug-resistant (MDR) pathogens. We investigated antimicrobial synergy of polymyxin/rifampicin combination against MDR Acinetobacter baumannii. In vitro static time-kill studies were performed over 48 h at an initial inoculum of ∼107 CFU/mL against three polymyxin-susceptible but MDR A. baumannii isolates. Membrane integrity was examined at 1 and 4 h post-treatment to elucidate the mechanism of synergy. Finally, a semi-mechanistic PK/PD model was developed to simultaneously describe the time course of bacterial killing and prevention of regrowth by mono- and combination therapies. Polymyxin B and rifampicin alone produced initial killing against MDR A. baumannii but were associated with extensive regrowth. Notably, the combination showed synergistic killing across all three A. baumannii isolates with bacterial loads below the limit of quantification for up to 48 h. Membrane integrity assays confirmed the role of polymyxin-driven outer membrane remodelling in the observed synergy. Subsequently, the mechanism of synergy was incorporated into a PK/PD model to describe the enhanced uptake of rifampicin due to polymyxin-induced membrane permeabilisation. Simulations with clinically utilised dosing regimens confirmed the therapeutic potential of this combination, particularly in the prevention of bacterial regrowth. Finally, results from a neutropenic mouse thigh infection model confirmed the in vivo synergistic killing of the combination against A. baumannii AB5075. Our results showed that polymyxin B combined with rifampicin is a promising option to treat bloodstream and tissue infection caused by MDR A. baumannii and warrants clinical evaluations.
ISSN:0924-8579
1872-7913
DOI:10.1016/j.ijantimicag.2023.106902