Antimicrobial effect of licorice root extracts against mutans streptococci isolated from Korean

Abstract

Introduction: The purpose of this study was to analyze optimal concentration of licorice root extracts to inhibit growth of the clinical isolates of mutans streptococci from Koreans. Methods: Minimum inhibition concentration (MIC), minimum bactericidal concentration (MBC) and time-kill kinetic assays were evaluated using the clinical strains of S. mutans (KCOM 1054, KCOM 1111, KCOM 1113, KCOM 1116, KCOM 1126, KCOM 1128, KCOM 1136, KCOM 1197, KCOM 1202, KCOM 1207, KCOM 1217) and S. sobrinus (KCOM 1157, KCOM 1196, KCOM 1221) isolated from Koreans and obtained from the Korean Collection for Oral Microbiology. Results: The MIC values of licorice root extracts against the clinical strains of mutans streptococci ranged from 4 to 8 µg/ml. The MBC values of licorice root extracts against the clinical strains of mutans streptococci ranged from 8 to 16 µg/ml. A time-kill assay indicated that the antimicrobial effects of licorice root extracts mainly result from the bactericidal effects. The all data suggest that regardless of S. mutans or S. sobrinus, the optimal concentration of licorice root extracts over 8 µg/ml can be used in vivo for the prevention of dental caries in Koreans.