Antimicrobial activities of 82 kinds of Chinese herbal medicines against the pathogen of Streptococcus from tilapia in vitro

The antimicrobial activities of 82 Chinese herb aqueous extracts against the pathogen of Streptococcus from tilapia in vitro were screened by the agar Oxford plate diffusion system. Results demonstrated that 20 kinds of Chinese herbs could effectively inhibit the growth of S. agalactiae，Coptis chinensis and Galla chinensis had the best inhibitory effects. In the combined susceptibility test，disc agar diffusion was used to evaluate the combination effects of 12 Chinese herb aqueous extracts in vitro against the pathogen of Streptococcus from tilapia. The results showed that there was synergic effect for the combined inhibition of aqueous extracts from Galla chinensis and Rheum palmatum L. or Artemisia argyi Levl. et Vant. or Salvia miltiorrhiza or Caesalpinia sappan or Schisandra chinensis or Sargentodoxa cuneata or Punica granatum L. or Reynoutria japonica Houtt or Coptis chinensis ；synergic effect for Coptis chinensis and Rheum palmatum L. or Salvia miltiorrhiza or Caesalpinia sappan or Sargentodoxa cuneata；synergic effect for Berberis spp. and Rheum palmatum L. or Salvia miltiorrhiza or Caesalpinia sappan or Sargentodoxa cuneata or Punica granatum L. or Coptis chinensis or Prunella vulgaris Linn or Schisandra chinensis. But the effect of combination of aqueous extracts was inhibitory interaction between Coptis chinensis and Artemisia argyi Levl. et Vant. or Schisandra chinensis or Punica granatum L.，inhibitory interaction between Berberis spp. and Artemisia argyi Levl. et Vant. or Schisandra chinensis or Reynoutria japonica Houtt. Combination of Galla chinensis and Prunella vulgaris Linn or Berberis spp.，Coptis chinensis and Reynoutria japonica Houtt or Prunella vulgaris Linn or Galla chinensis or Berberis spp. showed indifferent interactions.