Changes in intestinal microbiota of Northern sheatfish ( Silurus soldatovi ) associated with concurrent infections of Aeromonas veronii and Vibrio cholerae

In human beings and mammals, disorder of the intestinal microbiota was closely with some metabolic and inflammatory diseases. To date, there were few studies focusing on the relationship between intestinal microbiota composition and disease occurrence in fish. Recently, an acute infectious disease of northern sheatfish ( Silurus soldatovi ) emerged in a fish farm in Tianjin, China. Two dominant bacterial strains named S1 and S2 were isolated from the diseased fish and identified as Aeromonas veronii and Vibrio cholerae respectively,   according to their physiological and biochemical characteristics and genotype. Then, 16S rDNA high-throughput sequencing was conducted to compare the intestinal microbiota community of diseased fish with that of healthy fish. The microbial composition analysis showed that the dominant phylum in both diseased and healthy fish were Proteobacteria, Bacteroidetes, and Fusobacteria. At genus level, the differences in bacterial community compositions between diseased and healthy fish were mainly reflected by the changes in the relative abundances of bacterium , Aeromonas , and Vibrio . This was consist with the result of LEfSe analysis. PICRUSt function prediction indicated that the changes in the function of intestinal microbiota of diseased northern sheatfish were mainly reflected by different enrichment of some KEGG pathways such as “membrane transport”, “cellular processes and signaling”, “cell motility”, “signal transduction”, “infectious diseases”, “replication and repair”, “translation”, “nucleotide metabolism”, “folding, sorting and degradation”, and “cell growth and death”. The presented results indicated that the disease occurrence in the northern sheatfish associated with the bacterial infection was closely related to the changes in the composition and function of its intestinal microbiota.