Controlling Pseudomonas aeruginosa persister cells by weak electrochemical currents and synergistic effects with tobramycin

It is well recognized that bacterial populations commonly contain a small percentage of phenotypic variants, known as persister cells, which are dormant and extremely tolerant to antibiotics. When the antibiotic treatment is stopped, surviving persister cells can regenerate the bacterial population with a similar percentage of persister cells. Such persistence presents a great challenge to curing chronic infections, such as those associated with implanted medical devices. In this study, we report that bacterial persister cells can be effectively eliminated by low-level direct currents (DCs); e.g. treatment with 70 μA/cm² DC for 1 h using stainless steel (SS) 304 reduced the number of viable planktonic persister cells of Pseudomonas aeruginosa PAO1 by 98% compared to the untreated control. In addition to persister killing by applying DC alone, synergistic effects were observed when treating persister cells with 70 μA/cm² DC and 1.5 μg/mL tobramycin together using SS304 electrodes. The same level of DC was also found to be cidal to biofilms-associated persister cells of P. aeruginosa PAO1. These results are helpful for developing more effective methods to control chronic infections associated with implanted medical devices.