John, S.; Lee, J.W.; Lamichhane, P.; Dinh, T.; Nolan, T.; Yoon, T. Potential Synergistic Inhibition of Enterococcus faecalis by Essential Oils and Antibiotics. Appl. Sci.2023, 13, 11089.
John, S.; Lee, J.W.; Lamichhane, P.; Dinh, T.; Nolan, T.; Yoon, T. Potential Synergistic Inhibition of Enterococcus faecalis by Essential Oils and Antibiotics. Appl. Sci. 2023, 13, 11089.
John, S.; Lee, J.W.; Lamichhane, P.; Dinh, T.; Nolan, T.; Yoon, T. Potential Synergistic Inhibition of Enterococcus faecalis by Essential Oils and Antibiotics. Appl. Sci.2023, 13, 11089.
John, S.; Lee, J.W.; Lamichhane, P.; Dinh, T.; Nolan, T.; Yoon, T. Potential Synergistic Inhibition of Enterococcus faecalis by Essential Oils and Antibiotics. Appl. Sci. 2023, 13, 11089.
Abstract
Recurrent infections after root canal treatments often involve Enterococcus faecalis, a microorganism closely associated with therapy failures due to its biofilm production, survival in nutrient-deprived conditions, and antibiotic tolerance. Essential oils (EOs), which display anti-inflammatory, antimicrobial, and antibacterial properties, exhibit inhibitory effects on the growth of many microorganisms including E. faecalis. This study assessed the in vitro efficacy of combining antibiotics (Gentamicin 1.5mg/ml, Streptomycin 2.5 mg/ml, Ampicillin 5 mg/ml, and Kanamycin 2.5 mg/ml) with Cinnamon (1.25% to 5%) or Clove (25% to 50%) EOs using disk diffusion tests. Disks were treated with EOs-only, antibiotics-only, or EO-antibiotic combinations, placed on BEA agar plates, incubated for 24 hours, and zones of inhibition were measured against E. faecalis. Results showed robust growth inhibition by cinnamon and clove EOs across all tested concentrations. Furthermore, there were synergistic antimicrobial effects when gentamicin, streptomycin and kanamycin were combined with 2.5% and 50% concentrations of cinnamon and clove EOs, respectively, leading to significant growth inhibition of E. faecalis by 139% to 193% compared to using antibiotics or EOs alone. Clove EO showed positive synergism with three antibiotics (gentamicin, streptomycin, and kanamycin) whereas cinnamon EO showed synergism with two antibiotics (streptomycin and kanamycin). These findings suggest that combining cinnamon and clove EOs with aminoglycoside antibiotics can significantly reduce the expansion of E. faecalis compared to antibiotics alone. Further in vivo studies should determine the safety, efficacy, and treatment duration, with the potential to reduce antibiotic dosages and associated toxicity while preventing recurrent infections.
Medicine and Pharmacology, Dentistry and Oral Surgery
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