Antibacterial activity on different extracts of 50 Chinese herbal medicines against Streptococcus suis in vitro

The antibacterial activity of aqueous and 75% alcoholic extracts of 50 Chinese herbal medicines against 5 resistant strains of Streptococcus suis were determined in vitro by Kirby-Bauer and microdilution method. The objective was to screen the most efficient Chinese herbal medicine against resistance isolates through comparing the antibacterial effects. The results showed that only different extracts of Chinese herbal medicine 1 and Chinese herbal medicine 2 had better inhibitory action against resistant strains of Streptococcus suis,and the other extracts of Chinese herbal medicines had no inhibitory action. And the antibacterial activity of 75% alcoholic extracts of Chinese herbal medicine1 and Chinese herbal medicine 2 was better than that of aqueous extracts.