Impact of prebiotic and probiotic diets on gut bacterial microbiota and susceptibility to Edwardsiella ictaluri challenge in oxytetracycline-treated channel catfish

Authors: Older, Caitlin; Richardson, Bradley; GRIFFIN, MATT - Mississippi State University; REIFERS, J - Mississippi State University; GOODMAN, PENELOPE - Mississippi State University; WARE, CYNTHIA - Mississippi State University; GATLIN III, DELBERT - Texas A&M University; WISE, DAVID - Mississippi State University; YAMAMOTO, FERNANDO - Mississippi State University

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2024
Publication Date: 12/12/2024
Citation: Older, C.E., Richardson, B.M., Griffin, M.J., Reifers, J.G., Goodman, P.M., Ware, C., Gatlin Iii, D.M., Wise, D.J., Yamamoto, F.Y. 2024. Impact of prebiotic and probiotic diets on gut bacterial microbiota and susceptibility to Edwardsiella ictaluri challenge in oxytetracycline-treated channel catfish. Journal of Fish Diseases. 48(3)e14066. https://doi.org/10.1111/jfd.14066.
DOI: https://doi.org/10.1111/jfd.14066

Interpretive Summary: Antibiotics are often used in response to bacterial disease outbreaks in aquaculture. The nature of aquaculture necessitates a population-based approach to manage disease, which subjects both sick and unaffected fish to antibiotics. For unaffected individuals, antibiotic treatment can disrupt existing microbial gut communities, which may put the individual at risk for subsequent enteric infection due to reductions in numbers of resident microbes, some of which protect the host from infection. Food ingredients that can be used by beneficial microbes, also known as "prebiotics", and beneficial microbes which can be administered to the host, or "probiotics", are thought to enhance recovery of the gut bacterial community. Scientists at the USDA ARS Warmwater Aquaculture Research Unit in Stoneville, MS, in collaboration with researchers from Mississippi State University and Texas A&M University examined the impact of oxytetracycline, one of the few antibiotics approved for use in catfish, on the gut bacterial community, or “microbiota” of channel catfish. Additionally, the research group evaluated the effectiveness of diets containing either a prebiotic or probiotic in facilitating recovery of the gut microbiota and enhancing survival after a challenge with one of the primary bacterial pathogens of catfish, Edwardsiella ictaluri. The results of the study indicated oxytetracycline does not cause strong gut bacterial microbiota disruption. When fish treated with antibiotics were offered a prebiotic-containing diet and then exposed to E. ictaluri, these fish appeared to have slightly reduced survival. Collectively, the results add to the existing knowledge of antibiotic-induced disruption in catfish and warrant further research into the mechanisms which may explain a lack of oxytetracycline-induced disruption, as well as the utility of prebiotics and probiotics for gut health recovery.

Technical Abstract: Antibiotics are often used in response to bacterial disease outbreaks in aquaculture. The nature of aquaculture necessitates a population-based approach to manage disease, which subjects both sick and unaffected fish to antibiotics. Broad-spectrum antibiotics indiscriminately kill or inhibit bacterial growth, including otherwise innocuous commensal or transient microbes. For a sick individual, the benefits of clearing the infection outweigh the potential adverse effects of antibiotic-induced dysbiosis. However, for unaffected individuals, antibiotic treatment can disrupt existing microbial gut communities, which may put the individual at risk for subsequent enteric infection due to reduced competition with commensal microbes. Pre- and probiotics are thought to enhance recovery of the gut microbiota following antibiotic disruption. Oxytetracycline is one of three antibiotics approved for use in US catfish aquaculture. This research examines the impact of oxytetracycline on the gut microbiota of channel catfish, along with the effectiveness of prebiotics and probiotics in facilitating recovery of the gut microbiome and enhancing survival during a subsequent Edwardsiella ictaluri challenge. The results of the study indicated oxytetracycline does not cause strong gut bacterial microbiota dysbiosis. When fish treated with antibiotics were subsequently offered a prebiotic-containing diet and then subjected to a challenge with E. ictaluri, these fish appeared to have slightly reduced survival. Collectively, the results add to the existing knowledge of antibiotic-induced dysbiosis in catfish and warrant further research into the mechanisms which may explain a lack of oxytetracycline-induced dysbiosis, as well as the utility of prebiotics and probiotics for gut health recovery.