Antimicrobial effect of natural dyeing products upon decaycausing bacteria

Objective: To evaluate the bacteriostatic and bactericidal activities of tinctures of Rosmarinus officinalis (Rosemary), Calendula officinalis (Marigold) and Mikania glomerata (Guaco) upon decay-causing bacteria and compare them to chlorhexidine’s. Methods: The Minimum Inhibitory Concentration (MIC) was determined by microdilution technique, using 96-well microplates. In each well were inserted 10μL of inoculum (108 cells/mL), 100μL of doubly concentrated BHI broth and 100μL of tinctures at concentrations that vary between 100 and 0.78 mg/mL for T1, T2 and T3. As positive control, Chlorhexidine 0.12% was used. Reading was performed after 24 hours, by visual method. The assays were realized in triplicate. Minimum Bactericidal Concentration (MBC) was obtained by seeding of last bacteriostatic and its preceding concentrations, for each product, on Blood Agar. The MBC was considered in the plates that did not present any bacterial growth. Results: Upon Streptococcus mutans, MIC was verified at 6.25mg/mL, for T1, T2, and T3 and MBC at 12.5mg/mL for T1 and T2, and at 6.25mg/mL for T3. Upon Streptococcus oralis, all products presented MIC and MBC at 0.78mg/mL. For Chlorhexidine, the MIC and MBC were 0,04mg/mL, upon S. mutans and S. oralis. Conclusion: The tinctures of Rosemary, Marigold and Guaco showed bactericidal and bacteriostatic activities at low concentrations, upon Streptococcus mutans e Streptococcus oralis. However, the antimicrobial activity of chlorhexidine was superior to the tinctures’