ORIGINAL RESEARCH article
Front. Bacteriol.
Sec. Pathogenesis, Vaccines, and Immunity of Bacterial Infections
Development of a recombinant live attenuated vaccine to protect channel catfish against motile Aeromonas septicemia
Provisionally accepted
- Mississippi State University, Starkville, United States
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Background/Objectives: Aeromonas hydrophila causes motile Aeromonas septicemia (MAS), which affects farm-raised catfish. Since 2009, outbreaks caused by a clonal genetic group of A. hydrophila (virulent A. hydrophila, or vAh) have caused significant losses of market-size catfish in Alabama and Mississippi. Previously, our group reported that recombinant vAh surface proteins are effective in protecting catfish against MAS. Furthermore, live attenuated Edwardsiella ictaluri vaccine strain ESC-NDKL1 is an efficacious vaccine for enteric septicemia of catfish (ESC). In the current study, we investigated ESC-NDKL1 as a potential vector for expressing vAh antigens. Methods and Results: Genes encoding vAh surface antigens were integrated into the ESC-NDKL1 chromosome by conjugation and homologous recombination. Six recombinant ESC-NDKL1 strains expressing one vAh antigen (ESC-NDKL1::atpase, ESC-NDKL1::fim, ESC-NDKL1:: fimMrfG, ESC-NDKL1::fimA, ESC-NDKL1::tdr, and ESC-NDKL1::ompA) showed significant protection against MAS with relative percent survival (RPS) of 52.10%, 25.67%, 39.99%, 38.93%, 47.83%, and 34.07%, respectively. Eleven recombinant ESC-NDKL1 strains expressing two vAh antigens showed significant protection against MAS and improved protection compared to recombinant ESC-NDKL1 strains expressing one vAh antigen. In particular, four recombinant ESC-NDKL1 strains expressing two vAh antigens (ESC-NDKL1::atpase::fimMrfG, ESC-NDKL1::fim::fimMrfG, ESC-NDKL1::tdr::fimMrfG, and ESC-NDKL1::fim::ompA) showed significant protection (p < 0.05) compared to non-recombinant ESC-NDKL1 with RPS of 55.72%, 60.18%, 61.74%, and 54.81%, respectively. Conclusion: We identified four promising vaccine candidate strains to control MAS in the catfish industry.
Keywords: Aquaculture, Edwardsiella ictaluri, Ictalurus punctatus, Vaccine, virulent Aeromonas hydrophila
Received: 07 Oct 2025; Accepted: 27 Jan 2026.
Copyright: © 2026 Gomaa, Tekedar, Abdelhamed, Lawrence and Karsi. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Mark L. Lawrence
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