Summary Multidrug (MDR) efflux pumps are ancient and conserved molecular machineries with relevant roles in different aspects of the bacterial physiology, besides antibiotic resistance. In the case of the environmental opportunistic pathogen Pseudomonas aeruginosa , it has been shown that overexpression of different efflux pumps is linked to the impairment of the quorum sensing (QS) response. Nevertheless, the causes of such i...