Ivacaftor, a Cystic Fibrosis Transmembrane Conductance Regulator Potentiator, Enhances Ciprofloxacin Activity Against Pseudomonas aeruginosa

Background Methods to improve the clinical efficacy of currently available antibiotics against multidrug resistant bacteria in cystic fibrosis (CF) chronic rhinosinusitis (CRS) are greatly needed. Ivacaftor, a cystic fibrosis transmembrane conductance regulator potentiator, was recently identified as having potentially beneficial off-target effects as a weak inhibitor of bacterial DNA gyrase and topoisomerase IV. The objective of the current study is to evaluate whether ivacaftor enhances the antimicrobial activity of ciprofloxacin against Pseudomonas aeruginosa. Methods The planktonic growth of the PAO-1 strain of P. aeruginosa was studied in the presence of ciprofloxacin and/or ivacaftor. Effects were measured according to optical density of cultured PAO-1 at 600 nm. For a static PAO-1 biofilm assay, the PAO-1 strain was inoculated and cultured for 72 h in the presence of the drugs. Formed PAO-1 biofilms were quantified by crystal violet staining and imaged with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Results PAO-1 growth was significantly reduced in the presence of ivacaftor (8 or 16 mu g/mL) and ciprofloxacin (0.02 or 0.05 mu g/mL) compared to ciprofloxacin alone (P < .001). Similarly, ivacaftor (8 or 16 mu g/mL) showed a significant reduction of PAO-1 biofilms when treated with 0.05 mu g/mL of ciprofloxacin. Significant synergism was noted between ciprofloxacin and 16 mu g/mL of ivacaftor (P < .0001) in reducing planktonic growth and biofilm formation. Quantitative measurements with crystal violet staining were correlated to CLSM and SEM images. Conclusion Ivacaftor enhanced ciprofloxacin's antimicrobial activity against P. aeruginosa. Further studies evaluating the efficacy of ivacaftor/ciprofloxacin combination for P. aeruginosa for CF CRS are warranted.