The antimicrobial activities of 153 kinds of Chinese herbal medicines against the pathogen of Streptococcus from tilapia in vitro

【Objective】 The antimicrobial effects of Chinese herbal medicines against the pathogen of Streptococcus from tilapia in vitro were studied.【Method】 The antimicrobial effects of 153 Chinese herbal medicines were screened by disc agar diffusion.Double-dilution method was used to detect the minimal inhibitory concentration and the minimum bactericidal concentration of some herb medicines which had significant inhibitory effects to streptococcus,pathogens from tilapia streptococcusis,Streptococcus iniae and S.agalactiae.【Result】 The results showed that 8 kinds of Chinese herbs including Macleaya cordata,Mahonia fortunei,Lithospermum erythrorhizon,Berberis spp.,Hypericum japonicum,Panax notoginseng,Psoralea corylifolia,and Galla chinensie could effectively inhibit the growth of S.iniae,their minimal inhibitory concentrations and the minimal bactericidal concentrations were among 0.31-20.00 mg/mL and 0.63-20.00 mg/mL,respectively.Macleaya cordata had the best inhibitory effects with the diameter of inhibition zone(DIZ)of(24.3±1.1) mm.Macleaya cordata,Glycyrrhiza uralensi,Lithospermum erythrorhizon,Hypericum japonicum,Panax notoginseng,Flemingia philippinensis,Patrinina villosa,Sophora flavescens,Psoralea corylifolia,Schisandra chinensis,Bidens bipinnata,Selaginella uncinata,Berberis spp,.and Galla chinensis inhibited the growth of S.agalactiae,their minimal inhibitory concentrations and the minimal bactericidal concentrations were 1.25-20.00 mg/mL and 2.50-40.00 mg/mL,respectively.Macleaya cordata had the strongest inhibitory effects with the DIZ of(24.3±1.1) mm.Berberis spp.and Macleaya cordata were the two best medicines against Streptococcus iniae and S.agalactiae.The MIC and MBC of Berberis spp.were 0.31,0.63 mg/mL(Streptococcus iniae)and 1.25,2.50 mg/mL(S.agalactiae)while that of Macleaya cordata were 0.63,1.25 mg/mL(Streptococcus iniae)and 0.94,1.88 mg/mL(S.agalactiae).【Conclusion】 The screening results confirmed the possible use of Chinese herbal medicines as a source of antimicrobial alternatives to control the streptococcus diseases in tilapia production.