Co-infection of porcine deltacoronavirus and porcine epidemic diarrhoea virus alters gut microbiota diversity and composition in the colon of piglets

•PDCoV and PEDV co-infection alters the gut microbiota composition at the genus level.•The abundance of mitsuokella was significantly increased in co-infection piglets.•Mitsuokella and pro-inflammatory cytokines secretion existed positive correlation. Porcine deltacoronavirus (PDCoV) and porcine epidemic diarrhoea virus (PEDV) are the main porcine enteric coronaviruses that cause severe diarrhoea in piglets, posing huge threat to the swine industry. Our previous study verified that the co-infection of PDCoV and PEDV is common in natural swine infections and obviously enhances the disease severity in piglets. However, the effects of co-infection of PDCoV and PEDV on intestinal microbial community are unknown. In current study, the microbial composition and diversity in the colon of piglets were analyzed. Our results showed that both of PDCoV and PEDV were mainly distributed in the small intestines and caused severe damage of ileum but not colon in the co-inoculated piglets. Furthermore, we observed that PDCoV and PEDV co-infection alters the gut microbiota composition at the phylum, family and genus levels. The abundance of Mitsuokella and Collinsella at genus level were significantly increased in PDCoV-PEDV co-infection piglets. Spearman's correlation analysis further suggested that there existed strong positive correlation between Mitsuokella and TNF-α, IL-6 and IL-8 secretion, these two factors may together aggravating the small intestine pathological lesions. These results proved there existed obvious correlation between the disease severity caused by PDCoV-PEDV co-infection and intestinal microbial community.