Cinnamon oil: A possible alternative for contact lens disinfection

• This is the first time to evaluate the antimicrobial effect of plant essential oil in combination with contact lens disinfectants.
• Combination of cinnamon oil with tobramycin had a synergistic effect against most tested organisms.
• Combination of cinnamon oil and multipurpose contact lens disinfectant succeeded to eradicate all tested microorganisms at all tested concentrations within 2–3 h contact time.

ObjectiveTo investigate the antibacterial activity of cinnamon oil alone and in combination with a multipurpose contact lens disinfectant solution (MPS) as well as tobramycin against multi drμg resistant conjunctival bacteria both in planktonic and sessile forms.MethodsMinimum inhibitory concentrations (MIC) of tobramycin and cinnamon oil against 19 bacterial strains were investigated against planktonic and sessile cells by micro-dilution methods. Synergistic effects were determined by well diffusion and micro-dilution tissue culture plate methods for planktonic and sessile cells respectively. Time kill assay was performed to study the bactericidal effect of cinnamon oil in concentrations ranging from 5% to 0.312% combined with an MPS with respect to time.ResultsMICs of cinnamon oil against planktonic bacteria ranged from 0.04% to 1.25% versus 0.156% to 5% for sessile cells. Combination of cinnamon oil with tobramycin had a synergistic effect against most tested organisms. The MIC values of cinnamon oil in combination with tobramycin was significantly lower than cinnamon oil alone against biofilm production (P = 0.004). Time kill assay revealed that combination of cinnamon oil and disinfectant successfully eradicated the tested microorganisms at all tested concentrations within 2 h contact time except for 0.312% concentration (3 h) versus 24 h for MPS alone.ConclusionCinnamon oil has a promising antimicrobial effect. It could be a probable candidate for contact lens disinfection.