Reseach On Inhibitory Effect And Mechanism Of Chinese Herbal Medicine On Pathogenic Vibrio Of Penaeus Vannamei

Chinese herbal medicine has been used in China for thousands of years,and it has the advantages of green,low toxicity,and wide sources.In recent years,the aquaculture industry has developed rapidly,and diseases caused by Vibrio have caused serious troubles in aquaculture.The traditional solution is to use antibiotics,but the disorderly use of antibiotics lead to the emergence of Vibrio resistance.How to use Chinese herbal medicine to effectively prevent and control diseases is an urgent problem to be solved in the aquaculture industry.This study explored the inhibitory effect and mechanism of Chinese herbal medicine on the pathogenic Vibrio of Penaeus vannamei,in order to provide a theoretical basis for the correct use of Chinese herbal medicine in aquaculture.The main research methods and results are as follows:The Oxford cup method was used to study the antibacterial effect of 30 Chinese herbal medicines.Among them,18 Chinese herbal medicines have inhibitory effect on Vibrio;12 Chinese herbal medicines have antibacterial effect on Vibrio parahaemolyticus;14 Chinese herbal medicines have antibacterial effect on Vibrio cholerae,Vibrio harvey and Vibrio alginolyticus have inhibitory effects;5 Chinese herbal medicines have inhibitory effects on Vibrio anguillarum.The antibacterial effect of some two-part Chinese medicines and three-part Chinese medicines on the four strains of Vibrio is stronger than that of single Chinese medicines,and some combinations have antagonistic effects.The minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)of gallnut and Fructus mume extracts against Vibrio parahaemolyticus were 0.49 mg/mL,0.98 mg/mL,3.91 mg/mL,and 31.25 mg/mL,respectively;The MIC and MBC of the extracts of Fructus mume and Stemone to Vibrio alginolyticus were 1.95 mg/mL,3.91 mg/mL,1.95 mg/mL,and 3.91 mg/mL,respectively.On this basis,the drug concentration was set to 0,1/4MIC,1/2MIC,1MIC,and 2MIC to test the antibacterial mechanism of Chinese herbal extracts against Vibrio parahaemolyticus and Vibrio alginolyticus.The results showed that:1/4MIC,1/2MIC gallnut,Fructus mume,and Stemona extract significantly inhibited the growth of Vibrio parahaemolyticus and Vibrio alginolyticus.After treatment of Chinese herbal medicine extracts,the relative conductivity and nucleic acid leakage of Vibrio parahaemolyticus and Vibrio alginolyticus increased significantly(p<0.01).It is speculated that the permeability of the Vibrio’s membrane was increased and the integrity of the membrane was damaged.At the same time,Chinese herbal medicine extracts significantly increased the inhibition rate of biofilm(p<0.01);led to a significant decrease in respiratory chain dehydrogenase activity(p<0.01);Vibrio’s nucleic acid synthesis was inhibited.Scanning electron microscopy(SEM)observation revealed that the bacterial cell was shrunken,some cells were broken,intracellular material flowed out,and the bacterial structure could not be kept intact after the treatment of the Chinese herbal medicine extracts.SDS-PAGE showed that the number of protein bands decreased significantly with the increase of concentration,the intensity and clarity of bands decreased,and the protein synthesis of Vibrio was inhibited after the treatment of Chinese herbal medicine extracts.In summary,Chinese herbal medicine extracts can increase the permeability of Vibrio’s membranes,destroy cell walls and cell membrane structures,inhibit protein and nucleic acid synthesis,and inhibit the formation of biofilms,thereby producing a good antibacterial effect on Vibrio.