Effects of twenty traditional Chinese medicine extracts against Streptococcus agalactiae in vitro

【Objective】 Screening for the traditional Chinese medicines which have good antibacterial effects on Streptococcus agalactiae in vitro.【Method】 Using ethanol reflux and ultrasonic method, extracts of 20 different traditional Chinese medicines were obtained. Minimal inhibitory concentration(MIC) and minimal bactericidal concentration(MBC) of Coptis chinensis and other 19 extracts of traditional Chinese medicines on St. agalactiae were detected by macrodilution broth method, and combined antibacterial effects in vitro of them were also observed. 【Result and conclusion】 The MICs of the extracts obtained from Prunus mume, Coptis chinensis, Scutellaria baicalensis, Polygonum cuspidatum and Sanguisorba officinalis against St. agalactiae ranged from 7.80 to 31.25 mg/mL. The MICs of the extracts obtained from Taraxacum mongolicum, Artemisia scoparia, Fraxinus rhynchophylla, Artemisia argyi, Phellodendron chinense, Houttuynia cordata, Violae yedoensis and Pulsatilla chinensis ranged from 62.50 to 125.00 mg/mL. The MICs of the extracts obtained from Po. multiflorum, Sophora flavescens, Andrographis paniculata, Eucommia ulmoides, Forsythia suspensa, Lonicera japonica and Prunella vulgaris ranged from 250.00 to 500.00 mg/mL. The results of joint bacteriostatic test showed that the fractional inhibitory concentration index (FICI) of the extracts obtained from Sc. baicalensis, Po. cuspidatum, Sa. officinalisand C. chinensis was less than or equal to 1. The FICI of Po. cuspidatum, Sc. baicalensis and Sa. officinalis was more than 2. C. chinensis, Sc. baicalensis, Po. cuspidatum and Sa. officinalis showed a good antibacterial effect against St. agalactiae in vitro. The combination of Sa. officinalis and C. chinensis was characterized by a additive effect, whereas the combination of C. chinensis, Sc. baicalensis and Po. cuspidatum was characterized by a synergism effect. The combination of Sa. officinalis and Sc. baicalensis, Po. cuspidatum showed antagonism effect.