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.

The Electricidal Effect Is Active in an Experimental Model of Staphylococcus epidermidis Chronic Foreign Body Osteomyelitis

“…This would be a potential strategy for overcoming the reduced susceptibility of biofilm microorganisms to conventional antimicrobial agents. The mechanism of the antibacterial activity of electrical current is unknown; however, this activity has been suggested to result from toxic substances produced as a result of electrolysis (e.g., H 2 O 2 , oxidizing radicals, and chlorine molecules) (10,18), oxidation of enzymes and coenzymes, membrane damage leading to leakage of essential cytoplasmic constituents (15), and/or altered bacterial respiratory rate (6). In one study (13), an ionic strength-dependent transfer of electrons during the initial bacterial adhesion mechanism that had to be reversed in order for detachment to occur was proposed.…”

Electrical methods of controlling bacterial adhesion and biofilm on device surfaces

“…It has been widely reported that whilst an electric current enhances the efficacy of the antimicrobial treatment of biofilms, the same electric current without an antimicrobial agent has no significant impact on the numbers of viable biofilm bacteria. However, in the last few years, studies of the long-term exposure of biofilms to a low intensity electrical current have shown that prolonged exposure in the absence of antimicrobial agents resulted in a marked decrease in the viability of a number of biofilm strains [4]. This recent development, known as the electricidal effect, goes contrary to the findings of many previous reports which stated that electric current alone is not effective in killing biofilm bacteria and provides fresh incentive to explore the possibility of designing a new generation of antimicrobial surfaces and devices.…”

“…It is estimated that they are responsible for 65% of all human microbial infections [1][2][3][4] with treatment costs in excess of one billion dollars per year in the USA [5,6]. The key pathogens responsible for device-related infections are…”

“…Such cells will aggregate and enter a reduced metabolic state, exhibiting an altered (or 'biofilm') phenotype and form architecturally complex, structured communities of bacteria encased in a self-produced extracellular polymeric matrix known as a biofilm on virtually any surface with which they come into contact [4,15,16]. The biofilm phenotype also confers the advantage of significantly enhanced tolerance to antimicrobial agents, predation and immune clearance.…”

“…The biofilm phenotype also confers the advantage of significantly enhanced tolerance to antimicrobial agents, predation and immune clearance. In fact, biofilms have been shown to be resistant to antibiotics in concentrations 500 to 5,000 times those required to kill planktonic cells of the same species [4,[16][17][18][19][20][21]. Worse still, small surviving populations known as persister cells [15,22] withstand antibiotic treatment and can rapidly repopulate the surface thus acting as a nidus of recurrent infections, such as UTIs.…”