Dynamic effects of Aeromonas sobria infection on intestinal morphology, microbiota and goblet cells of rainbow trout (Oncorhynchus mykiss)

Abstract

Aeromonas sobria is an opportunistic pathogen that caused gastroenteritis and septicemia in humans, animals and aquatic species. However, its effects on the intestinal mucosal barrier remains unclear. In this paper, the dynamic effects of A.sobria on intestinal morphology, microbiota and goblet cells of rainbow trout (48 fish, weighing 400 ± 50 g) were revealed by histomorphology, 16S rRNA sequencing, ELISA and Alcian blue-periodic acid sthiff (AB-PAS) staining after isolating A.sobria from diseased rainbow trout during outbreak. The results showed that the expression of penicillin and cephalosporin biosynthesis increased significantly at 12–72 h. The level of Lipopolysaccharide (LPS) in feces and serum increased significantly at 12–72 h and 24–72 h, respectively (P < 0.05). In addition, A.sobria infection induced dysbiosis but never caused significant changes in the relative abundance of Proteobacteria. At 48 h, the richness and diversity of intestinal flora increased significantly (P < 0.001), while the number of goblet cells decreased significantly (P < 0.001). Intestinal villi underwent necrosis, shedding and cellular vacuolar degeneration, resulting in the most severe damage. At 9 d, there was no significant difference in richness, but the diversity was significantly reduced (P < 0.05), indicating that the intestinal flora had recovered its balance but could not return the initial state. The pathological results showed that the intestinal villi became shorter and wider spaced, and the mucosal lamina propria and muscle layer became thinner. At 15 d, the diversity of intestinal flora was still decreasing. Our study indicated that the intestinal dysbiosis and LPS production caused by A.sobria infection may be related to the activation of penicillin and cephalosporin biosynthesis, independent of Proteobacteria. Furthermore, increased diversity of intestinal flora and decreased number of goblet cells were the characteristics of intestinal tissue damage, while sustained decreased diversity and weakened resilience of intestinal flora were the hallmarks of chronic intestinal disease. This will lay a foundation for the study of pathogenic mechanism of A.sobria.