Hyperbaric Oxygen Sensitizes Anoxic Pseudomonas aeruginosa Biofilm to Ciprofloxacin

Antimicrob Agents Chemother. 2017 Oct 24;61(11):e01024-17. doi: 10.1128/AAC.01024-17. Print 2017 Nov.

Abstract

Chronic Pseudomonas aeruginosa lung infection is characterized by the presence of endobronchial antibiotic-tolerant biofilm, which is subject to strong oxygen (O2) depletion due to the activity of surrounding polymorphonuclear leukocytes. The exact mechanisms affecting the antibiotic susceptibility of biofilms remain unclear, but accumulating evidence suggests that the efficacy of several bactericidal antibiotics is enhanced by stimulation of aerobic respiration of pathogens, while lack of O2 increases their tolerance. In fact, the bactericidal effect of several antibiotics depends on active aerobic metabolism activity and the endogenous formation of reactive O2 radicals (ROS). In this study, we aimed to apply hyperbaric oxygen treatment (HBOT) to sensitize anoxic P. aeruginosa agarose biofilms established to mimic situations with intense O2 consumption by the host response in the cystic fibrosis (CF) lung. Application of HBOT resulted in enhanced bactericidal activity of ciprofloxacin at clinically relevant durations and was accompanied by indications of restored aerobic respiration, involvement of endogenous lethal oxidative stress, and increased bacterial growth. The findings highlight that oxygenation by HBOT improves the bactericidal activity of ciprofloxacin on P. aeruginosa biofilm and suggest that bacterial biofilms are sensitized to antibiotics by supplying hyperbaric O2.

Keywords: Pseudomonas aeruginosa; biofilms; ciprofloxacin; hyperbaric oxygen; oxygen radicals.

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Biofilms / drug effects*
  • Ciprofloxacin / pharmacology*
  • Hyperbaric Oxygenation*
  • Oxygen / pharmacology
  • Pseudomonas aeruginosa / drug effects*
  • Pseudomonas aeruginosa / physiology

Substances

  • Anti-Bacterial Agents
  • Ciprofloxacin
  • Oxygen