Channel catfish Ictalurus punctatus is one of the most cultured fish in the United States, and enteric septicemia of catfish (ESC), caused by Edwardsiella ictaluri, is the most prevalent disease affecting this species. Romet®, Terramycin®, and Aquaflor® are approved antibiotics for the treatment of bacterial infections in catfish. Effectiveness of these drugs can be limited since fish can show anorexia at early stages of infection, intestinal microbial flora imbalance, and the emergence of antibiotic-resistant E. ictaluri strains can potentially occur. The use of prebiotics has been considered due to the low cost of these components in relation to antibiotics and the effectiveness of supplemented diets that can potentially modify the gut-associated microbiota, enhancing disease resistance and survival of farmed fish. In this study, we evaluated four different commercial prebiotics and their effect on growth, gut microbiome, and the survival of channel catfish after experimental infection with E. ictaluri.
Specific pathogen free channel catfish fingerlings were cultured in a flow-through system. Experimental diets consisted of fish feed supplemented with commercially available prebiotics fructo- (diet One, FOS), isomalto- (diet Two, IMO), xylo- (diet Three, XOS), and galactooligosaccharides (diet Four, GOS) (Table 1). Two control diets were added. After completing the feeding period, fish were challenged with E. ictaluri, euthanized after a two-week period, and dissected for intestinal tissue sampling. Intestinal bacterial communities were determined using next generation sequencing. Edwardsiella ictaluri infection was confirmed by tissue culture, and MALDI-TOF.
Results indicated significant differences among the diets and fish weight (P< 0.05). Survival of fish challenged with E. ictaluri was also significantly different (P< 0.05) (Table 2). Different prebiotic concentration, combinations and microbial manipulation might yield different results.