Abstract: This study aimed to screen the Mongolian medicines that have good antibacterial effects against Staphylococcus aureus （S. aureus） and Escherichia coli （E. coli）. The hole-punch method was employed to determine the susceptibility of S. aureus and E. coli to pomegranate rind, Terminalia chebula, Artemisia austriaca, Scutellaria baicalensis, Astragalus mongholicus, Sophora flavescens, and Clematis florida. The minimal inhibitory concentration （MIC） of the seven kinds of Mongolian medicines against S. aureus and E. coli were assessed by using micro-dilution method. Furthermore, the fractional inhibitory concentration index （FICI） of the screened Mongolian medicines that performed good antibacterial effects against S. aureus and E. coli were evaluated via chessboard method. The results showed that the inhibitory zone diameter of pomegranate rind, Terminalia chebula and Scutellaria baicalensis against S. aureus ranged from 23.30 to 32.60 mm, and corresponding MICs ranged from 0.98 to 7.80 mg/mL; the inhibitory zone diameter of pomegranate rind, Terminalia chebula and Scutellaria baicalensis against E. coli ranged from 5.20 to 12.50 mm, and corresponding MICs ranged from 7.80 to 31.50 mg/mL. The FICI of combinative use of pomegranate rind and Terminalia chebula against S. aureus was 1.00, indicating an additive effect; the FICIs of combinative use of Terminalia chebula and Scutellaria baicalensis as well as Terminalia chebula and pomegranate rind against E. coli were both 0.75, indicating an additive effect. In summary, from the perspective of comprehensive antibacterial effects, S. aureus and E. coli are extremely sensitive or highly sensitive to pomegranate rind, Terminalia chebula and Scutellaria baicalensis; pomegranate rind, Scutellaria baicalensis and Terminalia chebula can be given priority in formulas that inhibit S. aureus, while Scutellaria baicalensis, Terminalia chebula and pomegranate rind can be given priority in formulas that inhibit E. coli.

Key words: Mongolian medicines, Staphylococcus aureus, Escherichia coli, minimum inhibitory concentration, fractional inhibitory concentration index