Polymyxin triple combinations against polymyxin-resistant, multidrug-resistant, KPC-producing klebsiella pneumoniae

Su Mon Aye, Irene Galani, Heidi Yu, Jiping Wang, Ke Chen, Hasini Wickremasinghe, Ilias Karaiskos, Phillip J. Berge, Jinxin Zhao, Tony Velkov, Helen Giamarellou, Yu-Wei Lin, Brian T. Tsuj, Jian Li

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13 Citations (Scopus)


Resistance to polymyxin antibiotics is increasing. Without new antibiotic classes, combination therapy is often required. We systematically investigated bacterial killing with polymyxin-based combinations against multidrug-resistant (including polymyxin-resistant), carbapenemase-producing Klebsiella pneumoniae. Monotherapies and double- and triple-combination therapies were compared to identify the most efficacious treatment using static time-kill studies (24 h, six isolates), an in vitro pharmacokinetic/pharmacodynamic model (IVM; 48 h, two isolates), and the mouse thigh infection model (24 h, six isolates). In static time-kill studies, all monotherapies (polymyxin B, rifampin, amikacin, meropenem, or minocycline) were ineffective. Initial bacterial killing was enhanced with various polymyxin B-containing double combinations; however, substantial regrowth occurred in most cases by 24 h. Most polymyxin B-containing triple combinations provided greater and more sustained killing than double combinations. Standard dosage regimens of polymyxin B (2.5 mg/kg of body weight/day), rifampin (600 mg every 12 h), and amikacin (7.5 mg/kg every 12 h) were simulated in the IVM. Against isolate ATH 16, no viable bacteria were detected across 5 to 25 h with triple therapy, with regrowth to ~2-log10 CFU/ml occurring at 48 h. Against isolate BD 32, rapid initial killing of ~3.5-log10 CFU/ml at 5 h was followed by a slow decline to ~2-log10 CFU/ml at 48 h. In infected mice, polymyxin B monotherapy (60 mg/kg/day) generally was ineffective. With triple therapy (polymyxin B at 60 mg/kg/day, rifampin at 120 mg/kg/day, and amikacin at 300 mg/kg/day), at 24 h there was an ~1.7-log10 CFU/thigh reduction compared to the starting inoculum for all six isolates. Our results demonstrate that the polymyxin B-rifampin-amikacin combination significantly enhanced in vitro and in vivo bacterial killing, providing important information for the optimization of polymyxin-based combinations in patients.

Original languageEnglish
Article numbere00246-20
Number of pages12
JournalAntimicrobial Agents and Chemotherapy
Issue number8
Publication statusPublished - Jul 2020


  • Amikacin
  • Combination
  • Klebsiella pneumoniae
  • Polymyxin resistance
  • Rifampin

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