In vitro antibacterial activity of 6 Chinese herbal medicines against 4 pathogens of freshwater fish

In this study,six Chinese herb medicines were tested for their antibacterial activity against 4 pathogens of freshwater fish: Aeromonas sobria,A.hydrophila,Pseudomonas fluorescent biotypeⅠand Flavobacterium columnaris.Using the aqueous extracts of 6 Chinese herbal medicines,Coptis chinensis,Rhem officinale,Forsythia suspensa,Houttuynia cordata,Magnolia officinalis and Folium isatidis,we measured the diameter of the zone of inhibition by a filter paper disc test and determined the minimal inhibitory concentration by concentration gradient method.Results indicate that the aqueous extract of C.chinensis has the strongest inhibitory effect on the 4 pathogens,then come R.officinale and F.suspensa,while H.cordata,M.officinalis and F.isatidis do not have significant inhibitory effects.