The eficiency of Listeria monocytogenes bacteria efflux pumps

Abstract

Antimicrobial resistance is a constantly growing worldwide problem. A key part of antimicrobial resistance is multidrug resistance efflux pumps. Because of these pumps Listeria monocytogenes is a multidrug resistant pathogen, not sensitive to many antimicrobial compounds. It is very important to understand the mechanisms how could we regulate the activity of efflux pumps, because L. monocytogenes is an opportunistic foodborne Gram-positive pathogen causing serious human infections. It is not easy to develop new antimicrobial compounds which would not be a substrate of efflux pumps in addition the sides effects of new compounds are unknown so the knowledge about the inhibition of antibiotics efflux out of cells could increase the effectiveness of treatment. Materials and methods. We used potentiometric and fluorescence methods to assay the inhibition of L. monocytogenes efflux pumps. We used tetraphenylphosphonium, which is a substrate of these pumps, selective electrode to register the inhibition of efflux. In parallel, the intensity of ethidium fluorescence was determined. We used inhibitors of different families of efflux pumps, such as chlorpromazine, verapamil, reserpine. Also we explored the effect of Phe-Arg-β-naphthylamide (PAβN) and 1-(1-Naphthylmethyl)piperazine which have not yet been used against gram-positive bacteria. The aim. The aim of our studies was to determine the specificities of tetraphenylphosphonium and ethidium interaction with L. monocytogenes cells and to evaluate the efficiency of efflux pumps inhibition. Conclusions. TPP+ strongly inhibits the intensity of respiration of L. monocytogenes cells while ethidium – not. We determined that all of used inhibitors increase the accumulation of efflux pumps substrate. In addition, we observed that PAβN and NMP inhibit the efflux of tetraphenylphosphonium but not ethidium. [...]