Investigating the ability of edwardsiella ictaluri and flavobac-terium covae to persist within commercial catfish pond sedi-ments under laboratory conditions

Authors: TUTTLE, JAMES - Auburn University; BRUCE, TIMOTHY - Auburn University; BUTTS, IAN - Auburn University; ROY, LUKE - Auburn University; ABDELRAHMAN, HISHAM - Auburn University; Beck, Benjamin; KELLY, ANITA - Auburn University

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2023
Publication Date: 6/25/2023
Citation: Tuttle, J., Bruce, T., Butts, I., Roy, L., Abdelrahman, H., Beck, B.H., Kelly, A. 2023. Investigating the ability of edwardsiella ictaluri and flavobac-terium covae to persist within commercial catfish pond sedi-ments under laboratory conditions. Pathogens. 12(7):871. https://doi.org/10.3390/pathogens12070871.
DOI: https://doi.org/10.3390/pathogens12070871

Interpretive Summary: Two prevalent bacterial diseases in commercial catfish aquaculture are enteric septicemia of catfish and columnaris disease caused by Edwardsiella ictaluri and Flavobacterium covae, respectively. Chronic and recurring outbreaks of these bacterial pathogens result in significant economic losses for producers annually. Determining if these pathogens can persist within sediments of commercial ponds is paramount. Experimental persistence trials (PT) were conducted to evaluate the persistence of E. ictaluri and F. covae in pond sediments. Twelve test chambers containing sterilized sediment from four commercial catfish ponds, were inoculated with either E. ictaluri or F. covae and submerged in 8 L of disinfected water. At 1, 2, 4-, 6-, 8-, and 15-days post-inoculation, a subsample of sediment was removed, and colony forming units (CFU) were counted. E. ictaluri population peaked on Day 3 and correlation analysis revealed no correlation between the sediment physicochemical parameters and E. ictaluri numbers. However, no viable F. covae colonies recovered after two attempts. Future studies are needed to improve understanding of pathogenesis and E. ictaluri persistence and potential and F. covae persistence in pond bottom sediments.

Technical Abstract: Two prevalent bacterial diseases in commercial catfish aquaculture are enteric septicemia of catfish and columnaris disease caused by Edwardsiella ictaluri and Flavobacterium covae, respectively. Chronic and recurring outbreaks of these bacterial pathogens result in significant economic losses for producers annually. Determining if these pathogens can persist within sediments of commercial ponds is paramount. Experimental persistence trials (PT) were conducted to evaluate the persistence of E. ictaluri and F. covae in pond sediments. Twelve test chambers containing 120 g of sterilized sediment from four commercial catfish ponds, were inoculated with either E. ictaluri (S97-773) or F. covae (ALG-00-530) and submerged in 8 L of disinfected water. At 1, 2, 4-, 6-, 8-, and 15-days post-inoculation, 1 g of sediment was removed, and colony forming units (CFU) were enumerated on appropriate selective media using 6 × 6 drop plate methods. E. ictaluri population peaked on Day 3 at 6.4 ± 0.5 log10 CFU g-1. Correlation analysis revealed no correlation between the sediment physicochemical parameters and E. ictaluri CFU g-1. However, no viable F. covae colonies recovered after two PT attempts. Future studies are needed to improve understanding of pathogenesis and E. ictaluri persistence and potential and F. covae persistence in pond bottom sediments.