Bioelectric effect and bacterial biofilms. A systematic review

Abstract

Bacteria growing in biofilms cause a wide range of human infections. Biofilm bacteria are resistant to antimicrobics at levels 500 to 5,000 times higher than those needed to kill non-biofilm bacteria. In vitro experiments have shown that electric current can enhance the activity of some antimicrobial agents against certain bacteria in biofilms; this has been termed the ''bioelectric effect''. Direct electrical current has already been safely used in humans for fracture healing. Application of direct electric current with antimicrobial chemotherapy in humans could theoretically abrogate the need to remove the device in device-related infections, a procedure associated with substantial morbidity and cost. In this article, we review what has been described in the literature with regards to the bioelectric effect.

Fig. 1

A) Some proposed biofilm-associated resistance mechanisms: (1) antimicrobial agents may be trapped and destroyed by enzymes in the biofilm matrix; (2) antimicrobial agents may fail to penetrate beyond the surface layers of the biofilm; (3) antimicrobial agents may not be active against non-growing microorganisms; (4) expression of biofilm specific resistance genes (e.g., efflux pumps); (5) stress response to hostile environmental conditions. B) Some proposed bioelectric effect mechanisms: (1) reduction of the biofilm capacity for binding to the antimicrobial agent; (2) electrophoretic augmentation of the antimicrobial agent transport; (3) membrane permeabilization; (4) electrolytic generation of oxygen; (5) electrochemical generation of potentiating oxidants.