# Study on bacteriostasis of Chinese herbal medicine extracts to avibacterium paragallinarum

## TL;DR

This study investigates the antibacterial effects of Chinese herbal medicine extracts against Avibacterium paragallinarum, a bacteria causing chicken rhinitis, and finds that a specific herbal mixture is effective.

## Contribution

The study identifies a specific herbal mixture (Mixture I) with strong antibacterial and anti-inflammatory effects against Avibacterium paragallinarum in chickens.

## Key findings

- Mixture I had the lowest MIC80 of 1 μg/μL and the largest inhibition zone of 2.16 ±0.15 mm.
- Mixture I improved chick growth and reduced inflammatory factor expression in macrophages.
- Seven herbal extracts showed varying degrees of antibacterial activity against Avibacterium paragallinarum.

## Abstract

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.