Screening Of Chinese Herbal Medicine Compounds Against The Main Pathogenic Bacteria From Cultivated Eels

Eel is one of the most important economical aquaculture species in China. In recent years, the eel farming industry grows rapidly. However, the industry has been suffered from tremendous economic loss due to the outbreak of bacterial diseases. In commercially driven, some broad-spectrum antibiotics are sometimes used to control it. Those medicines have some advantages, such as high-efficiency and short-cycle, but the indiscriminate use of antibiotics may destroy the balance of water environment, produce drug-resistant bacterial strains, inhibit the growth of eels, and reduce the quality of eel product. In comparison with antibiotics, Chinese herbal medicines have many advantages, such as: immune-stimulation and low residual toxicity. Therefore more attention has been focused on using Chinese herbal medicines to prevent and treat fish diseases, In this study, Chinese herbal medicine compounds were screened for controling the major pathogenic bacteria from eels. The results are as follows:1. Six Chinese herbal medicines, called CHM1, CHM2, CHM3, CHM4, CHM5 and CHM6, were processed by decocting, grinding into powder ( 50～75μm ) and ultramicro-pulverization (5～10μm)respectively. Bacteriostatic effect of each Chinese herbal by the above different proceesing methods against 16 pathogenic bacteria was assesmented. The results showed that the bacteriostatic effect of each Chinese herbal grinding into ultramicro-powder was the best, followed by those of grinding into powder and decocting.2. The better Bacteriostatic effects of the above six Chinese herbals grinding into ultramicro-powder against 20 pathogenic bacteria (including the above 16 pathogenic bacteria) in turn were CHM1, CHM2, CHM3, CHM4, CHM5 and CHM6.3. 15 combinations of two Chinese herbals designed by Cross-test method were used to examine the bacteriostatic effects against 20 pathogenic bacteria. Of which, five combinations, CHM1+CHM2, CHM1+CHM3, CHM2+CHM3, CHM2+CHM4 and CHM2+ CHM5, show synergism bacteriostatic effects against more than 90% pathogenic bacteria tested according to the FIC index≤0.75.4. Based on the above results, we tested the bacteriostatic effects of the compounds of CHM1,CHM2 and CHM3 against 7 pathogenic bacteria often detected in the ell farms. The results indicated that the compounds have the synergism bacteriostatic effect against all tested pathogenic bacteria according to the FIC index =0.5. The results of this study indicated that the Chinese herbals grinding to ultramicro-pulverization has the better bacteriostatic effects. Six Chinese herbals can inhibit the growth of all 20 pathogenic bacteria tested. Five compounds of two herbals screened in this study showed the synergism effect against more than 90% pathogenic bacteria. The compound of three herbals against the seven common pathogenic bacteria has better bacteriostatic effects than single herbal and the compound of two herbals. The results from this study are of important application and reference values for the prevention and treatment of bacterial disease of cultivited eels as well as other fishes.