Antimicrobial activity of colloidal nanosilver 24 ppm in vitro

T. P. Popova, I. Ignatov, F. Huether, T. Petrova


The antimicrobial effect of colloidal nanosilver (AgNPs) at a concentration of 24 ppm against reference strains of Esherichia coli, Salmonella enterica, Staphylococcus aureus, Clostridium perfringens, Candida albicans and two clinical isolates (Pseudominas aeruginosa and Streptococcus pyogenes) was examined. The agar diffusion method, determination of the minimum inhibitory concentrations (MIC) and the time of antimicrobial action of AgNPs were used. In the studies performed by the disc-diffusion method, a very good inhibitory effect of AgNPs 24 ppm was reported in all tested microorganisms. The examined Gram-negative bacteria showed higher sensitivity to colloidal nanosilver in comparison with the Gram-positive microorganisms. In the Gram-positive bacteria, the MIC values of the studied AgNPs were higher than in Gram-negative ones. C. perfringens with MIC50 0.5 μg/ml showed the highest sensitivity to AgNPs 24 ppm, and S. aureus (MIC50 2 μg/ml) - the lowest. AgNPs 30 ppm inactivated all tested Gramnegative bacterial strains within 1 min. In a suspension with a density of 106 cells/ml C. perfringens died within 24 min. However, individual cells of S. aureus remained viable for more than 60 min, and of S. pyogenes and C. albicans - for more than 120 min. In a suspension with a density of 104 cells/ml Gram-positive microorganisms survived for twice as short time - C. perfringens up to 15 min, S. aureus over 30 min, and S. pyogenes and C. albicans - for at least 60 min. These results provide hope for the successful use of AgNPs as disinfectant and antiseptic, as well as for topical therapy of infections involving these microbial species.

Keywords: colloidal nanosilver AgNPs, antimicrobial activity
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