Antibiofilm Activity of Low-Amperage Continuous and Intermittent Direct Electrical Current

Abstract

Bacterial biofilms are difficult to treat using available antimicrobial agents, so new antibiofilm strategies are needed. We previously showed that 20, 200, and 2,000 A of electrical current reduced bacterial biofilms of Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. Here, we tested continuous direct current at lower amperages, intermittent direct current, and combinations of surface materials (Teflon or titanium) and electrode compositions (stainless steel, graphite, titanium, or platinum) against S. aureus, S. epidermidis, and P. aeruginosa biofilms. In addition, we tested 200 or 2,000 A for 1 and 4 days against biofilms of 33 strains representing 13 species of microorganisms. The logarithmic reduction factor was used to measure treatment effects. Using continuous current delivery, the lowest active amperage was 2 A for 1, 4, or 7 days against P. aeruginosa and 5 A for 7 days against S. epidermidis and S. aureus biofilms. Delivery of 200 A for 4 h a day over 4 days reduced P. aeruginosa, S. aureus, and S. epidermidis biofilms on Teflon or titanium discs. A reduction of P. aeruginosa, S. aureus, and S. epidermidis biofilms was measured for 23 of 24 combinations of surface materials and electrode compositions tested. Four days of direct current delivery reduced biofilms of 25 of 33 strains studied. In conclusion, low-amperage current or 4 h a day of intermittent current delivered using a variety of electrode compositions reduced P. aeruginosa, S. aureus, and S. epidermidis biofilms on a variety of surface materials. The electricidal effect was observed against a majority of bacterial species studied.C hronic infections associated with medical devices such as joint replacements and other types of orthopedic instrumentation, prosthetic heart valves, pacemakers, implantable defibrillators, urinary catheters and stents, peritoneal dialysis catheters, intravascular catheters, cerebrospinal fluid shunts, breast implants, and vascular grafts and stents are common in today's medical practice. When these devices become infected, they must often be removed to successfully cure the associated infection. Device removal is associated with significant morbidity, cost, and, in some cases, mortality. Prosthetic joint removal, for example, may mean that a patient is left without a functional joint for months, along with the requirement for two surgeries (i.e., infected implant removal and eventual replacement) (1). Intrathoracic device infections may require major surgical procedures, involving repeat sternotomy. The removal of some devices, such as vascular graft bypasses, may be impossible, rendering associated infection incurable with current approaches.The pathogenesis of device-associated infections relates to the presence of microorganisms in biofilms. Existence within a biofilm represents a survival strategy for microorganisms, protecting them from environmental influences, the host immune system, and, unfortunately, therapeutic levels of conventional antimicrobial agents. Biofilms exhibit ...

Antibiofilm Activity of Electrical Current in a Catheter Model

“…Detachment promoted by enhanced repulsive forces between microorganisms and surface materials may also play a role (31,(35)(36)(37)(38). Although our results are consistent with previously reported data showing a bactericidal effect of DC on sessile and planktonic cells, previous studies either used different electrode positioning, focusing on biofilms grown on discs placed between two electrodes (22,25,39), or investigated the effects of custom-fabricated, electrically conductive catheters on bacterial colonization in agar plates (40). In this study, electrodes were simply placed into the lumen of commercially available catheters on which biofilms had been grown.…”

“…Biofilms of Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa on Teflon discs were exposed to 20, 200, or 2,000 A direct current (DC) for up to 7 days, which resulted in time-and dose-dependent antibiofilm effects, as measured by decreases in numbers of viable cells (20). Subsequent studies confirmed the microbicidal activity of continuously and intermittently applied electrical current against established biofilms of several bacterial and fungal species in vitro and in animal models (21)(22)(23)(24)(25).A potential avenue to deliver electrical current is to administer it to the lumen of catheters. This location of biofilm formation in CRBSI and CAUTI provides a site targetable by electrical current.…”

Exposure of Bacterial Biofilms to Electrical Current Leads to Cell Death Mediated in Part by Reactive Oxygen Species

“…epidermidis foreign body osteomyelitis exposed to 200 μA DC for 21 days had a decrease in bacterial quantities compared to those that were not exposed to current [11]. To date, we have investigated 33 different bacterial and fungal strains, representing 13 species of microorganisms, and have observed a time and dose-dependent electricidal effect against most isolates tested [12]. We have also demonstrated activity of lower amounts of DC (2, 5 or 10 μA) against most isolates tested [12].…”

“…To date, we have investigated 33 different bacterial and fungal strains, representing 13 species of microorganisms, and have observed a time and dose-dependent electricidal effect against most isolates tested [12]. We have also demonstrated activity of lower amounts of DC (2, 5 or 10 μA) against most isolates tested [12]. Additionally, we have found that the electrical current does not need to be continuously applied; for example, application of 200 μA DC for as little as 2 hours per day over a 4 day period reduces biofilms [12].…”

“…We have also demonstrated activity of lower amounts of DC (2, 5 or 10 μA) against most isolates tested [12]. Additionally, we have found that the electrical current does not need to be continuously applied; for example, application of 200 μA DC for as little as 2 hours per day over a 4 day period reduces biofilms [12]. The next logical step was to determine if the electricidal effect promotes biofilm detachment and/or leads to cell death and to also elucidate the factors that play a role in the observed effect.…”