Study on bacteriostasis of Chinese herbal medicine extracts to avibacterium paragallinarum

To explore the treatment of Chinese herbal medicine extracts on infectious rhinitis caused by Avibacterium paragallinarum, a strain of Avibacterium paragallinarum was isolated from the nasal cavity and infraorbital sinus of chickens suspected of infectious rhinitis, it was biologically identified as Bacillus paracarinus. Extracts of seven kinds of traditional Chinese medicine and traditional Chinese medicine mixtures were explored to determine the minimum inhibitory concentration (MIC) by the microdilution method and the disc diffusion method. The antibacterial activity against pathogenic bacteria of Chinese herbal medicine extracts was determined by the animal infection treatment test. The MIC₈₀ results showed that the Acorus gramineus, Phellodendron chinense and Herba taraxaci were 4 μg/μL, the Sophora flavescens was 16 μg/μL, the Pulsatilla adans was 32 μg/μL, and the Cassia obtusifolia and Polygonum hydropiper were 128 μg/μL, while the minimum MIC₈₀ of Mixture Ⅰ was 1 μg/μL. The results of the drug susceptibility test of the paper diffusion test, while the inhibition zone of Mixture Ⅰ was the largest, with an inhibition zone of 2.16 ±0.15. It shows that the mixture Ⅰ had a strong inhibitory effect on Avibacterium paragallinarum. The results of animal experiments showed that the average daily gain of chicks in the protection group and the treatment group was higher than that in the infection group. A qPCR assay was performed to verify that mixture I could reduce the expression of inflammatory factors. Conclusion: 7 kinds of Chinese herbal medicines, including calamus, dandelion, and phellodendron, exhibited better antibacterial effects against Avibacterium paragallinarum. Additionally, Mixture I showed significant preventive and therapeutic effects on infectious coryza in chickens caused by Avibacterium paragallinarum. Furthermore, Mixture I could effectively reduce the expression of inflammatory factors in macrophages that were stimulated with lipopolysaccharides.