Synergistic effect of fucoidan with antibiotics against oral pathogenic bacteria

Abstract Background Fucoidan is a sulphated polysaccharide that is primarily extracted from brown seaweeds; it has been broadly studied in recent years due to its numerous biological properties, including anticoagulant, antithrombotic, antitumour and antiviral activities. Objective and design In this study, fucoidan was evaluated against oral bacteria, either alone or with antibiotics, via the broth dilution method and chequerboard and time-kill assay. Results Minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) values for the fucoidan against all the tested bacteria ranged between 0.125 and 0.50/0.25 and 1.00 mg ml−1 , for ampicillin 0.125 and 64/0.5 and 64 μg ml−1 and for gentamicin 2 and 256/4 and 512 μg ml−1 , respectively. Furthermore, the MIC and MBC were reduced to one half-eighth as a result of the combination of the fucoidan with antibiotics. One to 3 h of treatment with MIC50 of fucoidan with MIC50 of antibiotics resulted from an increase of the rate of killing in colony forming units (CFUs) ml−1 to a greater degree than was observed with alone. Conclusion These results suggest that fucoidan is important in the antibacterial actions of the agents.