Efflux pumps are channels found on the membrane of bacterial cells and actively export substances from inside to outside the cell. They help regulate the internal environment of the cell by expelling harmful substances that have entered the cell to the external environment. Such harmful substances include antibiotics. When these enter the cell, they are detected and pumped out through the efflux pumps. This prevents the amount of intracellular accumulation of the antibiotic necessary to become lethal to the inside of the cell, and the bacteria is therefore not affected by the antibiotic (see Figure 1).
Figure 1. Efflux pump pumping out antibiotics from cell.
Efflux pump inhibitors
Efflux pump inhibitors (EPI’s) inhibit the mechanism of these efflux pumps and therefore prevent the bacteria from exporting harmful substances. This can result in the successful necessary accumulation of antibiotic substances inside the cell, which may lead to critical lethal levels. In effect, EPI’s can reverse the antibiotic resistance the bacteria have developed (Sun et el., 2014) (see Figure 2).
Figure 2. Inhibited efflux pump unable to pump out antibiotics from cell.
Sun J, Deng Z, Yan A, (2014) Bacterial multidrug efflux pumps: Mechanisms, physiology and pharmacological exploitations. Biochemical and Biophysical Research Communications. 453(2):254-267.