Doxofylline Protects Gram-Negative Pathogens against Antibiotic-Mediated Killing

Area of Science:

• Microbiology
• Pharmacology
• Infectious Diseases

Background:

• Gram-negative bacterial infections are increasing, necessitating effective antibiotic use.
• Doxofylline, a bronchodilator and anti-inflammatory agent, has an unknown impact on antibiotic efficacy.
• Understanding drug interactions is crucial for optimizing respiratory disease treatment.

Purpose of the Study:

• To investigate the effect of doxofylline on antibiotic activity against Gram-negative bacteria.
• To elucidate the mechanism behind doxofylline's influence on antibiotic efficacy.
• To assess the clinical implications of using doxofylline with antibiotics.

Main Methods:

• Minimum inhibitory concentration (MIC) assays for various antibiotics.
• In vitro and in vivo studies using Gram-negative pathogens and murine lung infection models.
• Efflux pump inhibition tests, gene expression analysis, and knockout strain studies (ΔtolC).
• Reactive oxygen species (ROS) production measurements.

Main Results:

• Doxofylline significantly increased antibiotic MICs against Gram-negative bacteria.
• Doxofylline inhibited antibiotic-mediated bacterial killing in vitro and in vivo.
• Doxofylline upregulated the AcrAB-TolC efflux pump in a TolC-dependent manner.
• Doxofylline-induced protection correlated with reduced ROS production.

Conclusions:

• Doxofylline confers resistance to antibiotics in Gram-negative bacteria via the AcrAB-TolC efflux pump.
• Doxofylline suppresses antibiotic-induced ROS accumulation, contributing to bacterial survival.
• Clinical use of doxofylline with antibiotics requires caution due to potential antagonism.