Multi-drug resistance efflux pumps confer additional resistance against host innate immune defense via induction of genes for biofilm formation and virulence (MPF3P.803)

Abstract Multi-drug resistance, resistance-nodulation-differentiation efflux pumps in gram-negative bacteria are membrane protein complexes that extrude a wide variety of drugs before they can act on their bacterial target. However, they are not merely pumps for physical transport of drugs but their expression level is also up-regulated by the presence of drugs inside the bacteria, which, in turn, facilitates the release of quorum-sensing molecules and subsequent induction of genes responsible for biofilm formation and virulence. It is our hypothesis that efflux mediated biofilm formation and virulence expression offer gram-negative bacteria additional resistance not only against drugs but also against host innate immune defense. In order to test our hypothesis, we performed real-time qPCR studies on Fluidigm platform to monitor the expression of (i) the efflux genes and their regulators, (ii) the genes for synthesis of quorum sensing molecules and their regulators, and (iii) the genes for biofilm formation and virulence. For this, we used Pseudomonas aeruginosa and its efflux and quorum sensing mutants. The gene expression studies were performed for planktonic cells and nascent and mature biofilms in the presence and absence of a drug, ciprofloxacin. We were able to show efflux mediated expression of biofilm and virulence genes, which resulted in the abrogation of host innate immune defense in a cellular assay.