Innate Effector Systems in Primary Human Macrophages Sensitize Multidrug-Resistant Klebsiella pneumoniae to Antibiotics

Infect Immun. 2020 Jul 21;88(8):e00186-20. doi: 10.1128/IAI.00186-20. Print 2020 Jul 21.


Infections caused by multidrug-resistant (MDR) Klebsiella pneumoniae are difficult to treat with conventional antibiotics. Thus, alternative strategies to control the growth of MDR Klebsiella are warranted. We hypothesized that activation of innate effector systems could sensitize MDR K. pneumoniae to conventional antibiotics. Thus, human primary macrophages were stimulated with compounds known to activate innate immunity (vitamin D3, phenylbutyrate [PBA], and the aroylated phenylenediamine HO53) and then infected with MDR Klebsiella in the presence or absence of antibiotics. Antibiotics alone were ineffective against MDR Klebsiella in the cellular model, whereas vitamin D3, PBA, and HO53 reduced intracellular growth by up to 70%. The effect was further improved when the innate activators were combined with antibiotics. Vitamin D3- and PBA-induced bacterial killing was dependent on CAMP gene expression, whereas HO53 needed the production of reactive oxygen species (ROS), as shown in cells where the CYBB gene was silenced and in cells from a patient with reduced ROS production due to a deletion in the CYBB gene and skewed lyonization. The combination of innate effector activation by vitamin D3, PBA, and HO53 was effective in sensitizing MDR Klebsiella to conventional antibiotics in a primary human macrophage model. This study provides new evidence for future treatment options for K. pneumoniae.

Keywords: Klebsiella; antimicrobial peptides; autophagy; innate immunity; reactive oxygen species.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Antimicrobial Cationic Peptides / deficiency
  • Antimicrobial Cationic Peptides / genetics
  • Antimicrobial Cationic Peptides / immunology
  • Cholecalciferol / pharmacology*
  • Drug Resistance, Multiple, Bacterial / drug effects*
  • Drug Synergism
  • Gene Expression Regulation
  • Host-Pathogen Interactions
  • Humans
  • Immunity, Innate
  • Klebsiella pneumoniae / drug effects*
  • Klebsiella pneumoniae / growth & development
  • Klebsiella pneumoniae / immunology
  • Macrophage Activation / drug effects
  • Macrophages / drug effects*
  • Macrophages / immunology
  • Macrophages / microbiology
  • Microbial Sensitivity Tests
  • NADPH Oxidase 2 / deficiency
  • NADPH Oxidase 2 / genetics
  • NADPH Oxidase 2 / immunology
  • Phagocytosis / drug effects
  • Phenylbutyrates / pharmacology*
  • Phenylenediamines / pharmacology*
  • Primary Cell Culture
  • Reactive Oxygen Species / agonists
  • Reactive Oxygen Species / metabolism


  • Anti-Bacterial Agents
  • Antimicrobial Cationic Peptides
  • Phenylbutyrates
  • Phenylenediamines
  • Reactive Oxygen Species
  • Cholecalciferol
  • ropocamptide
  • CYBB protein, human
  • NADPH Oxidase 2