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...

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Contamination of drinking water by microorganisms and arsenic represents a major human health hazard in many parts of the world. An estimated 3.4 million deaths a year are attributable to waterborne diseases. Arsenic poisoning from contaminated water sources is causing a major health emergency in some countries such as Bangladesh where 35 to 77 million people are at risk. The World Health Organization (WHO) has recently recognized point-of-use water treatment as an effective means of reducing illness in developing country households. A new point-of-use water treatment system that is based on flocculation, sedimentation and disinfection was evaluated for the removal of bacterial, viral and parasitic pathogens as well as arsenic from drinking water to estimate its potential for use in developing countries. Tests were conducted with United States Environmental Protection Agency (EPA)-model and field- sample waters from developing countries. Samples were seeded with known numbers of organisms, treated with the combined flocculation/disinfection product, and assayed for survivors using standard assay techniques appropriate for the organism. Results indicated that this treatment system reduced the levels from 10(8)/l to undetectable (<1) of 14 types of representative waterborne bacterial pathogens including Salmonella typhi and Vibrio cholerae. No Escherichia coli were detected post-treatment in 320 field water samples collected from five developing countries. In addition, the water treatment system reduced polio and rotavirus titres by greater than 4-log values. Cyrptosporidium parvum and Giardia lamblia inocula were reduced by greater than 3-log values following use of this water treatment system. Arsenic, added to laboratory test waters, was reduced by 99.8%, and naturally occurring arsenic in field samples from highly contaminated Bangladeshi wells was reduced by 99.5% to mean levels of 1.2 microg/l. This water treatment system has demonstrated the potential to provide improved drinking water to households in developing countries by removing microbial and arsenic contaminants.

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Drinking water systems are known to harbour biofilms, even though these environments are oligotrophic and often contain a disinfectant. Control of these biofilms is important for aesthetic and regulatory reasons. Study of full-scale systems has pointed to several factors controlling biofilm growth, but cause-and-effect relationships can only be established in controlled reactors. Using laboratory and pilot distribution systems, along with a variety of bacterial detection techniques, insights have been gained on the structure and behaviour of biofilms in these environments. Chlorinated biofilms differ in structure from non-chlorinated biofilms, but often the number of cells is similar. The number and level of cellular activity is dependent on the predominant carbon source. There is an interaction between carbon sources, the biofilm and the type of pipe material, which complicates the ability to predict biofilm growth. Humic substances, which are known to sorb to surfaces, appear to be a usable carbon source for biofilms. The finding offers an explanation for many of the puzzling observations in full scale and laboratory studies on oligotrophic biofilm growth. Pathogens can persist in these environments as well. Detection requires methods that do not require culturing.