Antibacterial activity and synergistic effects between Machilus thunbergii ethanol extract and antibiotics against oral pathogens

The cortex of Machilus thunbergii, which has been consumed as traditional herbal medicine for treatment of leg edema and abdominal distension and pain for a long period of time. In this study, the combination effect of M. thunbergii ethanol extract (MTEE) was evaluated against oral bacteria, either alone or with antibiotics, via broth dilution method and checkerboard and time kill assay. MIC/MBC values for MTEE against all the tested bacteria ranged between 12.5-50/50-200 microg/ mL, for ampicillin 0.0625-8/0.125-32 microg/mL and for gentamicin 4-128/8-512 microg/mL respectively. Furthermore, the MIC and MBC were reduced to one half-eighth as a result of the combination of MTEE with antibiotics. 1-6 hours of treatment with 1/2 MIC of MTEE with 1/2 MIC of antibiotics resulted from an increase of the rate of killing in units of CFU/mL to a greater degree than was observed with alone. These results suggest that the MTEE is important in the antibacterial actions of oral pathogens agents.