Estimation of MBC: MIC Ratio of Herbal Extracts against Common Endodontic Pathogens

Herbal extracts have evoked interest owing to the small number of terpenoids and phenolic compounds, which impart antimicrobial, antioxidant, and anti-inflammatory properties. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC) of four herbal extracts (lemon grass oil, basil oil, peppermint oil, and Obicure tea extract) against endodontic pathogens along with the MIC: MBC/MFC ratio were evaluated. The antimicrobial activity by detecting the MIC of three essential oils and tea extract was evaluated against eight common endodontic pathogens by the broth dilution method, while MBC was detected by subculturing onto blood agar from the first -three to five tubes from the MIC dilution tubes (showing no turbidity), which were plated on blood agar. All herbal extracts proved to be effective antimicrobials against tested endodontic pathogens. Basil oil had a bacteriostatic effect on all the organisms (P < 0.05). Mint oil showed bacteriostatic activity on Enterococcus (E.) faecalis and Peptostreptococcus (P > 0.05). Tea extract had a bacteriostatic effect (P > 0.05) against all tested microbes except Actinomyces, Lactobacilli, Staphylococcus (S.) aureus, and Fusobacterium (F.) nucleatum. Lemon grass oil had a bactericidal effect against all the organisms and a bacteriostatic effect against Peptostreptococcus (P > 0.05). It can be concluded that basil oil showed a strong bactericidal effect on the test organisms. The MIC for the organisms ranged from 0.2 to 50 μg/ml.