Investigation of Effect of 1,8‑cineole on Antimicrobial Activity of Chlorhexidine Gluconate

Background: Chlorhexidine belongs to a group of medicines called antiseptic antibacterial agents. Chlorhexidine is commonly used for the care and clean off the skin, hands, and wounds. In recent years, medicinal and aromatic plants have been used for prevention of disease, maintaining health, and improving disease in traditional and modern medicine as a medicament. According to recent research, cineole is the isolated active agent of eucalyptus oil and possesses antimicrobial activity. It was demonstrated that cineole could enhance the antimicrobial effects of the other antiseptics. Objective: The aim of this study was to investigate the efficacy of 1,8‑cineole on the antimicrobial effect of chlorhexidine against some microorganisms. Materials and Methods: The effect of 1,8‑cineole on antimicrobial activity of chlorhexidine gluconate (CHG) was tested using seven different microorganisms. In this study, CHG (128–0.125 mg/l) and cineole (512–2 g/l) were analyzed together and separately using checkerboard assay. Interactions between CHG and 1,8‑cineole have been identified as synergistic, indifferent, or antagonistic. Results: Synergistic activity was demonstrated between CHG and 1,8‑cineole against Staphylococcus aureus, methicillin‑resistant S. aureus, Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, and Candida albicans. Indifferent interactions for these compounds were demonstrated against Pseudomonas aeruginosa. Conclusion: CHG antiseptic properties were found to be increased when CHG was used in combination with 1,8‑cineole. In this way, CHG will reveal stronger effect against microorganisms.