Quantitative determination of the antibacterial activity of licorice (Glycyrrhiza glabra) and tetracycline gel against Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg) and Prevotella intermedia (Pi) - a microbiological in vitro study.

Objectives: The aim of this study was to evaluate and compare the antibacterial efficacy of licorice gel and tetracycline gel against Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia.

Methods: An indigenously prepared 50 μL licorice and tetracycline gel was subjected to antibacterial sensitivity test (thrice) against Aa, Pg, Pi by agar well diffusion method using Brain Heart Infusion media. Colonies of Aa, Pg, Pi were transferred into broth and incubated at 37 °C for 24 h and diameter of inhibition zone was measured.

Results: The drug release profile of licorice gel at six regular intervals was higher when compared to tetracycline. MIC of licorice gel (50 μg/mL) against Aa (14 mg), Pg (7 mg), Pi (7 mg) respectively. The diameter of inhibition zone of licorice gel was significant against Aa when compared to tetracycline gel. However, tetracycline gel exhibited significant diameter of inhibition zone against Pg and Pi when compared to licorice gel. There was a statistical significance difference between licorice and tetracycline gel against Aa (p=0.043*), Pg (p=0.037*), Pi (p=0.046*) while assessing antibacterial sensitivity test.

Conclusions: Licorice gel has anti-inflammatory and anti-microbial properties which can act against periodontal pathogens and can be considered in treating periodontal disease at low concentrations. Therefore, it can be used as an adjunctive local drug delivery agent to non-surgical periodontal therapy (NSPT) in treating periodontal disease.