Study of the Effect of Silver Nanoparticles on Biofilms Formation by Staphylococcus epidermidis

Staphylococcus epidermidis produces extracellular polysaccharide which is known as a biofilm. Biofilm is highly effective in establishing of this bacterium infections and can be formed on medical devices that are used in the body. The purpose of this study was to evaluate the effects of silver colloidal nanoparticles on bacterial growth and biofilm formation of Staphylococcus epidermidis. In this empirical and cross-sectional study، experiments were performed on 13 clinical isolated specimens of Staphylococcus epidermidis and a reference strain (ATCC 12228). The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of nanoparticles were determined by the agar dilution method. The experiments of biofilm formation were done by micro titer plate method and stained by Safranin. Data were analyzed using ANOVA. The mean MIC and MBC of nanoparticles for clinical isolated specimens were 350 ± 19. 61 ppm and 707. 69 ± 64. 05 ppm، respectively and nanoparticles had bacteriostatic effect at low concentrations. Nanoparticles showed the anti-biofilm activity at the concentration of 0. 5 ppm and this effect enhanced with increasing concentration up to 4 ppm. Nanoparticles at higher concentrations of 150 ppm had the ability to eliminate the pre-formed biofilm. The results showed that colloidal silver nanoparticles have the ability to inhibit the S. epidermidis biofilm formation. It is offered to use these compounds to coat prosthetic devices which are placed in the body or to cover environmental surfaces in medical centers.