Evaluation of the Antimicrobial Activity of Colloidal Silver in Odontopathogenic Bacteria

Objectives: Determine the antimicrobial activity of colloidal silver in three oral bacteria.
Methods: Enterococcus faecalis (ATCC 29212), Fusobacterium nucleatum (ATCC 10953) and Streptococcus mutans (ATCC UA159) were obtained from the American Type Culture Collection. The minimal inhibitory concentration (MIC) was performed in 96-well flat-bottom plates containing 100μL of Colloidal Silver at 20 ppm in TSB supplemented with 10% FBS and 100 μL of 1.0 × 108 CFU / mL of bacterial strains, up to a final volume of 200μL per well; 5μg / mL chlorhexidine was used as a positive control for inhibition of bacterial growth and saline solution (SS) as a negative control. The plates were incubated at 37 ° C for 72h in a microaerobic atmosphere. Subsequently, the percentage of growth inhibition was calculated using the MIC value. Finally, 10 μL of culture were taken from wells without bacterial strains growth and spread on TSA supplemented with 5% DSB. The CFU were counted after seven days of incubation. The minimum bacterial concentration (MBC) value was established as the low-est concentration of colloidal silver that killed the bacterial strains. Data were evaluated using t-student and ANOVA in SPSS v.21
Results: The data obtained show that the antimicrobial activity of the colloidal silver of 20 ppm was 99.9% and therefore showed no microbial growth for the bacterial strains evaluated compared to the control group of chlorhexidine. A statistically significant difference was observed (p< 0.05) between the groups evaluated.
Conclusions: Colloidal silver at a concentration of 20 ppm has antimicrobial activity against odontopathogenic bacteria and could therefore be used as an antimicrobial in the oral cavity.