The proven antimicrobial efficacy of silver ion technology
RE: Effectiveness of antimicrobial silver ions against Pseudomonas aeruginosa, Klebsiella pneumonia and L pneumophila).
These three bacteria have been experimentally exposed to silver ions in order to determine the antimicrobial efficacy of this biocide. These investigations have been performed in a number of unconnected laboratories interested in a variety of scientific questions concerning antimicrobial silver ions. Notable pieces of laboratory-based research include the following:
Inactivation of Legionella pneumophila and Pseudomonas aeruginosa: evaluation of the bactericidal ability of silver cations. Water Research 2007 41(18):4097-104
In this study, silver cations at various concentrations were exposed to Legionella pneumophila, Pseudomonas aeruginosa (and E. coli) to quantitatively estimate the bactericidal ability of silver. Observed data were analyzed using a newly developed model (Cs x T) that introduced a specific amount of chemisorbed silver onto a bacterial cell (Cs), which represented the chemisorption properties of silver on the bacterial cell body. Silver cations were rapidly chemisorbed onto bacterial cells after injection into samples, and Cs values (initial concentration of silver was 0.1 mg Ag/l) were calculated as 1.810 x 10-6 (L. pneumophila), 1.102 x 10-6 (P. aeruginosa), and 1.638 x 10-6 μg Ag/cell(i) (E. coli) after incubation for 8 h. During that time, the three tested bacteria were completely inactivated under the detection limit (>7.2 log reduction, i.e. 99.99999%). This study shows the successful quantitative estimation of the bactericidal ability of silver.
Inactivation of Pseudomonas aeruginosa and Aeromonas hydrophila by silver in tap water. J Environ Sci Health A Tox Hazard Subst Environ Eng 2007 42(11):1579-84.
This study was conducted to assess the efficacy of silver as a replacement of chlorine utilized in water distribution systems. Pseudomonas aeruginosa and Aeromonas hydrophila are opportunistic pathogens present in drinking water and have been associated with waterborne disease. After 8 hours of exposure to 100 μg/L of silver, there was a >6-log10 reduction (99.9999%) in P. aeruginosa in tap water at room temperature at pH7 For A. hydrophila, a >6-log10 reduction occurred at both pH7 and pH9 within nine hours. The World Health Organization has determined that this amount of silver could be used for water disinfection without health risks.
Persistent silver disinfectant for the environmental control of pathogenic bacteria. Am J Infect Control 2003;31(4):208-14.
Contaminated surfaces can act as a reservoir for pathogenic microorganisms and potentially exacerbate the risk of infection. Surface disinfection and decontamination provide temporary amelioration against bacterial colonization. Disinfected surfaces eventually become contaminated, thus, mitigating the benefit of the initial disinfection. It is hypothesized that to improve on the current state of the art, a disinfectant should not only immediately disinfect a surface but also provide persistent antimicrobial action after the product has been applied. We describe here a silver-based disinfectant technology designed to provide long-lasting sanitization and disinfection to treated surfaces as evaluated on hard surfaces after repeated environmental insults.
Method: A comparative evaluation of 6 disinfectant formulations for residual antimicrobial activity after water rinsing was performed. Log reduction of bacterial populations on disinfectant-treated substrates were measured after 30 minutes to 8 hours of exposure and compared with an untreated control. In a similar study, the residual antimicrobial activity of a silver disinfectant was evaluated against antibiotic- and biocide-resistant bacteria also after water rinsing. Further, residual antimicrobial activity of the silver disinfectant was measured after 5 cycles of rinsing, abrasion, and contamination against representative household and nosocomial pathogens (E. coli, Staph. aureus, Klebsiella pneumoniae, Enterobacter aerogenes, Enterococcus faecium, or Salmonella choleraesuis) after 10-minute exposure times.
Results: In the comparative assay, only the silver disinfectant and a persistent quaternary ammonium compound disinfectant demonstrated significant residual activity (> or =3.0 log(10) reduction (99.9%) to control) against S aureus whereas only the silver disinfectant demonstrated activity against Pseudomonas. No residual activity (< or = 0.5 log reduction to untreated control) was observed for the other disinfectant products. The silver-based disinfectant also showed significant and equivalent efficacy against antibiotic-resistant bacteria. In addition, the silver disinfectant was able to achieve significant residual activity in 10 minutes against all organisms tested after 1, 3, and 5 cycles of water rinse, abrasion, and microbial contamination.
Conclusions: The findings show the ability of silver to reduce bacterial populations that contact treated surfaces within minutes, highlight the potential to interrupt cross-contamination from environmental surfaces, and reduce the risk of infection within the home and health care settings.
