Mechanism of electrical enhancement of efficacy of antibiotics in killing biofilm bacteria

Abstract

The bioelectric elfect, in which electric fields are used to enhance the efficacy of biocides and antibiotics in killing biofilm bacteria, has been shown to reduce the very high concentrations of these antibacterial agents needed to kill biofilm bacteria to levels very close to those needed to kill planktonic (floating) bacteria Work in many laboratories (16,17,32), including our own (3,12,33), has clearly established that biofilm bacteria are resistant to antibiotics and biocides at levels 500 to 5,000 times higher than those needed to kill planktonic cells of the same species. The mechanism of this inherent resistance of glycocalyx-enclosed biofilm bacteria to antimicrobial agents is not conclusively established but appears to depend on both diffusion limitation (25) and physiological properties associated with low growth rates (8,9,16,17) in biofilm populations. Direct examination of the surfaces of medical devices that have become the foci of device-related bacterial infections shows that these pathogens grow in well-developed adherent biofilms (12), and clinical experience (21) indicates that these chronic infections are highly refractory to antibiotic therapy. Consequently, device-related bacterial infections are aggressively treated with combinations of antibiotics (2, 27), but in many cases, the biofilm-colonized device must still be removed to facilitate the resolution of these infections (21,37).An increasing number of laboratories have begun to examine the effects of electric fields and current densities on biological systems (1,5,15,19,28,31,34,35,38,41), mainly because of interest in the electroporation and electrofusion processes that are very useful in genetic research (31). This body of work has shown that electric fields and currents can be used for electroporation and electrofusion (31), electroosmosis, iontophoresis (6,(13)(14)(15), and the electroinsertion of specific proteins (30). During this work, it has been noted that electric fields and currents can influence the organization of biological membranes (10,28,31,35,40,42) and membrane analogs (1, 18), metabolic and developmental processes within both prokaryotic and eukaryotic cells (19,24,34,38,42) 994-1960. Fax: (406) 994-6098. kilovolt-per-centimeter range, but a significant number (5,13,15,24,36) have also focused on the effects of low-intensity fields and currents on biological systems for which significant effects have been documented, especially embryonic systems (34).We have reported that low-intensity electric fields (field strength of 1.5 to 20 V/cm and current densities of 15 pA/cm2 to 2.1 mA/cm2) can completely override the inherent resistance of biofilm bacteria to biocides (7) and antibiotics (26). This bioelectric effect reduces the concentrations of these antibacterial agents needed to kill biofilm bacteria to 1.5 to 4.0 times those needed to kill planktonic cells of the same species. The present study was undertaken to examine the mechanism of this bioelectric effect, with the working hypothesis that the electric f...

Photodestruction of human dental plaque bacteria: Enhancement of the photodynamic effect by photomechanical waves in an oral biofilm model

“…Ultrasound [51][52][53] and electric fields [54][55][56] have been used to enhance the efficacy of antibiotics in killing biofilm bacteria in sterilization processes. Ultrasonic irradiation enhanced the killing of P. aeruginosa in biofilms by gentamicin by nearly two orders of magnitude [51,52].…”

“…O'Leary et al [53] have shown that statistically significant bactericidal effects of ultrasonic irradiation upon pure cultures of the periodontal pathogens P. gingivalis and A. actinomycetemcomitans were due to the incidental temperature increase [53]. On the other hand, small direct current electric fields achieved a 6-to 8-log increase in killing after 24 hours of exposure to the direct current using biofilms of P. aeruginosa [54][55][56]. An electric current enhanced the efficacy of gentamicin against the oral microorganism Streptococcus gordonii in an in vitro biofilm model [57].…”

Biofilm: the microbial ?bunker? for intravascular catheter-related infection

“…One approach is the use of catheters coated with antimicrobial agents alone, or in combination with the passage of a low voltage electric current [31]. The generation of electrolytes such as protons, hydroxyl anions, reactive oxygen intermediates, oxygen and hydrogen appears to enhance antibiotic killing of bacterial cells attached to the device surface and is termed the bioelectric effect [9].…”

Bacterial Colonization of Ureteral Stents

“…New polymers (e.g. Vivathiane), resorbable biomaterials (polyglycolic and polylactic acid), special coatings (hydrogels, silver, chlorhexidine, antibiotics, surlactin biosurfactant) or the addition of electric current have been shown to reduce bacterial colonization of medical devices in vitro [18, 19, 20, 21, 22, 23, 24, 25, 26, 27]and, alone or in combination, offer a variety of possibilities to eliminate the problem of colonization in future.…”