Abstract: 【Objective】 The aim of this study was to investigate the in vitro antibacterial and antiviral activity of the compound Shuanghuanglian preparation, and provide a scientific basis for the in-depth development of compound Shuanghuanglian and the rational selection of drugs for poultry and livestock.【Method】 The granules of honeysuckle, scutellaria and forsythia was made into infusion, respectively, and then the drug infusion and Andrographis paniculata were used to make the oral solution of Andrographis paniculata, double forsythia (honeysuckle:scutellaria:forsythia was 1:1:2) and compound double forsythia (honeysuckle:scutellaria:forsythia: Andrographis paniculata was 1:1:2:2) according to the ratio, and the raw drug concentration was 100%, pH was adjusted as 7.0.12 strains of Escherichia coli, Salmonella and Staphylococcus aureus were used for bacterial susceptibility testing, and the sensitive strains were screened by Oxford cup combined with test tube twofold dilution method.The in vitro antibacterial activity was investigated based on the minimum inhibitory concentration (MIC) of the drugs.The drugs were diluted by the twofold dilution method, rhesus monkey embryonic kidney cells (MA-104) and chicken embryonic fibroblasts (DF-1) were cultured, cell viability was detected by CCK-8 method, and the safe concentrations of the three drugs were determined in combination with cytopathic lesions (CPE).The maximum safe concentration of the drug was diluted in three gradients by twofold dilution, Newcastle disease virus (NDV) and Rotavirus were used to test MA-104 and DF-1 in three ways: Drug+virus interactions, drug addition followed by attack, and attack followed by drug addition.The cell viability was detected by CCK-8 method, and the in vitro antiviral activity of the drugs was explored in combination with CPE.【Result】 The antibacterial effect of compound Shuanghuanglian was better than that of Andrographis paniculata and Shuanghuanglian, and its MICs against Escherichia coli, Salmonella and Staphylococcus aureus were 0.20-1.56, 0.20-1.56 and 0.78-1.56 mg/mL, respectively.CPE and cell viability results showed that the safe concentration ranges of Shuanghuanglian, Andrographis paniculata and compound Shuanghuanglian against DF-1 cells were 0-6.25, 0-0.78 and 0-0.78 mg/mL, respectively, and the safe concentration ranges for MA-104 cells were 0-3.13, 0-0.78 and 0-0.78 mg/mL, respectively.The TCID₅₀ of Newcastle disease virus strain 17E on DF-1 cells was 10^-6.19/100 μL, and the TCID₅₀ of yak Rotavirus G6P[1] type SDA2 strain on MA-104 cells was 10^-6.24/100 μL.The effective inhibition rates of compound Shuanghuanglian against Newcastle disease virus by directly inactivating virus (drug+virus interactions), blocking virus adsorption (drug addition followed by attack) and interfering virus replication (attack followed by drug addition) pathways were 28.82%, 55.92% and 42.45%, respectively, and the corresponding effective inhibition rates of Rotavirus were 48.84%, 26.52% and 15.40%, respectively.【Conclusion】 The antibacterial and antiviral effects of the compound Shuanghuanglian were stronger than those of Shuanghuanglian and Andrographis paniculata, and its antibacterial effect on Escherichia coli and Salmonella was better than that on Staphylococcus aureus.The results could provide scientific basis for the clinical application and further development of compound Shuanghuanglian in veterinary medicine.

Key words: compound Shuanghuanglian; antibacterial activity; antiviral activity