Keywords: 
• traditional Chinese medicine /
• coptidis rhizoma decoction /
• Riemerella anatipestifer /
• inhibitory rate

Abstract: To determine the inhibitory rates for effective ingredients of a coptidis rhizoma（Coptis chinensis） decoction against the bacteria Riemerella anatipestifer and to further the study of drugs acting on the outer membrane of a bacterial protein，extractions were made from a coptidis rhizoma decoction made of coptidis rhizoma，cortex phellodendri（Phellodendron amurense），and licorice root （Glycyrrhiza uralensis） using water extraction and alcohol precipitation methods. First，a standard concentration curve for R. anatipestifer was used. Next，bacteria of 250，190，120，50 and 20 L were added to drug concentrations of 115.0，77.0，57.0，46.0，38.0，33.0 and 29.0 gL－1 with three replications. Then，after oscillating the culture for 12 h，the optical density（OD） values were measured. Afterward，the bacterial content for each drug concentration was calculated，the bacterial inhibitory rate was determined，and an analysis of variance was conducted on the inhibition rate. Results showed that for a drug concentration of 38.0 gL－1 and 20 L of R. anatipestifer，the antibacterial rate was 99.99%，whereas with 50 L the rate was 99.98%. However，for 46.0 gL-1，the antibacterial rate against R. anatipestifer with 120 L was 99.99%，with 190 L it was 99.98%，and with 250 L it was 99.98%. The optimal and critical drug concentration for antibacterial action was 29.0 gL-1. It showed a strong antibacterial effect for this medicine indicating further research would be beneficial.［Ch，1 fig. 3 tab. 14 ref.］