Ferulic acid potentiates the antibacterial activity of quinolone-based antibiotics against Acinetobacter baumannii.

Ferulic acid is a cinnamic derivative of phenolic acid and its pharmacophore (catechol) is responsible for antioxidant, prooxidant and antibacterial activities. In this study, we evaluated the influence of ferulic acid on the antibacterial activity of quinolone-based antibiotics against Acinetobacter baumannii. The minimum inhibitory concentration of ferulic acid against Acinetobacter baumannii AB5075 were considerably lowered for ΔsodB and ΔkatG mutants. Checkerboard assay shows synergistic interactions between ferulic acid and quinolones. In a murine sepsis model, ferulic acid potentiated the antibacterial activities of quinolones. Ferulic acid amplified quinolones-induced redox imbalance by increasing superoxide ion generation, NAD+/NADH ratio and ADP/ATP ratio. Conversely, the level of reduced glutathione was significantly lowered. We conclude that ferulic acid potentiates the antibacterial activity of quinolone-based antibiotics against A. baumannii by increasing ROS generation, energy metabolism and electron transport chain activity with a concomitant decrease in glutathione.