Nitrate Is Crucial for the Proliferation of Gut Escherichia coli Caused by H9N2 AIV Infection and Effective Regulation by Chinese Herbal Medicine Ageratum-Liquid

Abstract

H9N2 avian influenza virus (AIV) infection in chickens is often accompanied by secondary bacterial infection, but the mechanism is unclear. The aim of the present study was to reveal that mechanism and explore non-antibiotic treatment. 16s rRNA sequencing and metabonomics were performed in the intestinal contents of chickens infected with H9N2 AIV or H9N2 AIV and fed with ageratum-liquid (AL) to reveal the metabolite that promote intestinal Escherichia coli (E. coli) proliferation caused by H9N2 AIV, as well as to determine the regulatory effect of AL. It was found that H9N2 AIV infection led E. coli to become the dominant gut microbe and promoted E. coli translocation from the intestinal tract to the visceral tissue through the damaged intestinal barrier. H9N2 AIV infection induces inflammation in the intestinal mucosa and promotes the secretion and release of nitrate from the host intestinal epithelium. In addition, nitrate promoted E. coli proliferation in the inflamed intestinal tract following H9N2 AIV infection. Furthermore, Chinese herbal medicine AL can restore intestinal homeostasis, inhibit the production of nitrate in the intestinal epithelium and effectively prevent the proliferation and translocation of E. coli in the intestines. This is the first report on the mechanism of E. coli secondary infection induced by H9N2 AIV, where herbal medicine AL was shown to have a good preventive effect on the secondary infection.

Efficacy of recombinant Newcastle disease virus expressing HA protein of H9N2 Avian influenza virus in respiratory and intestinal tract

“…Nitrate metabolism could be used as an index to detect the reproductive level of E. coli in chicken intestinal tract. Previous studies had demonstrated that the level of nitrate metabolism in the intestine was positively correlated with the reproductive level of E. coli ( Zhang et al, 2020b ). In this study, the ileal tissues at the ileocecal junction of chickens in each group were collected for the detection of nitrate content 5 dpc.…”

“…Total RNA of the same quality ileal tissue was extracted with TRIzol (Invitrogen, Carlsbad, CA) according to the manufacturer's instructions. The total RNA was reverse transcribed into cDNA using the Genome Removal Reverse Transcription kit (Tiangen, Beijing, China), and gene expression level of ileum was detected using RT-qPCR as described previously ( Table 1 ; Zhang et al, 2020 b).…”

“…H9N2 AIV has multiple tissue tropisms and can replicate both in the respiratory and gastrointestinal tracts ( Post et al, 2012 ). Numerous studies had shown that H9N2 AIV infection caused intestinal flora disorder and inflammation ( Zhang et al, 2020a , b ; Chrzastek et al, 2021 ). Alterations in the gut microbial composition of chickens led to significantly increased shedding of H9N2 AIV in trachea and cloaca, which was associated with impaired expression of type I interferon ( IFN ) ( Yitbarek et al, 2018a ).…”

The Effect of the Antimicrobial Peptide Plectasin on the Growth Performance, Intestinal Health, and Immune Function of Yellow-Feathered Chickens

“…Intestinal microbes can be divided into intestinal symbiotic bacteria, conditional pathogenic bacteria, and pathogenic bacteria regarding to the relationship between the intestinal tract and host ( 52 ). The intestinal tract concentrations of conditioned pathogens are low, such as E. coli which is facultative anaerobes, but when intestinal homeostasis is disrupted, for instance, when the body is infected by virus, the proliferation of E. coli is rapidly promoted and led to intestinal disorders ( 53 ). In this study, application of the dietary antimicrobial peptide plectasin can significantly reduce the number of E. coli in the ileum and promote an increase in the content of Lactobacillus in the ileum, illustrating that plectasin can inhibit the proliferation of harmful bacteria in the intestine and change the structure of intestinal flora.…”

Transcriptome Analysis of Genes Responding to Infection of Leghorn Male Hepatocellular Cells With Fowl Adenovirus Serotype 4

“…In addition to the three major metabolic processes of host cells described above, we found that steroid biosynthesis and nitrogen metabolism were also altered after infection with FAdV-4. These are important host metabolic pathways that control the process and outcome of virus infections ( 49 , 50 ). Further studies on metabolic genes and signaling pathways associated with FAdV-4 infection may provide some reference value for studying the pathogenesis and new diagnostic methods of FAdV-4.…”