Influence of and on Polymyxin Pharmacodynamics in Pseudomonas aeruginosa and Implications for Quorum Sensing Inhibition with Azithromycin.

The impact of quorum sensing on polymyxin and azithromycin pharmacodynamics was assessed in PAO1 and an isogenic / double knockout. For polymyxin B, greater killing against the / knockout than against PAO1 was observed at 10 CFU/ml (polymyxin B half-maximal effective concentration [EC], 5.61 versus 12.5 mg/liter, respectively; < 0.005). Polymyxin B combined with azithromycin (256 mg/liter) was synergistic against each strain, significantly reducing the respective polymyxin B EC compared to those with monotherapy ( < 0.005), and is a promising strategy by which to combat .