Background: Nowadays a great need for an anti-bacterial agent can be used on a daily basis without side effects of antimicrobial chemicals as chlorhexidine. This is study aims to evaluate the microbiologic effect of Gum Arabic against streptococcus cultures. Materials and Methods: Aqueous of Gum Arabic Hashab (Acacia Senegal) and Talha (Acacia Seyal) with different concentration (10%-100%) were used to evaluate the antimicrobial activity by the agar well diffusion method. Streptococcus mutans was placed on the agar. Gum Arabic solution was propelled in the wells made in the agar, after incubation at 370C - for 24 hours in anaerobic incubator. The diameter of inhibition zones formed around wells were measured and compared with control (chlorhexidine 2%). Minimum inhibitory concentration for Hashab and Talha was determined. Results: No significant difference was found between Gum Arabic and chlorhexidine. The antimicrobial effect of Gum Arabic Hashab and Talha was similar to that of chlorhexidine (p-value > 0.05). Gum Arabic Hashab and Talha had same effect against Streptococcus mutans (p-value > 0.05). Minimum inhibitory concentration was 7% for Gum Arabic Hashab and 8% for Gum Arabic Talha. Conclusion: Gum Arabic inhibited the growth of Streptococcus mutans. It highly recommended to be used as preventive measure for cariogenic process.

Keywords: Antibacterial; Gum Arabic; Streptococcus Mutans; Dental Caries.