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ARS Home » Southeast Area » Auburn, Alabama » Aquatic Animal Health Research » Research » Publications at this Location » Publication #423511
Research Project: Optimizing Aquaponic Production Systems for Production Efficiency and Profitability

Location: Aquatic Animal Health Research

Title: DEVELOPMENT OF RIFAMPICIN AND NOVOBIOCIN RESISTANT Aeromonas salmonicida STRAINS AND THEIR POTENTIAL AS LIVE ATTENUATED VACCINE CANDIDATES

Author
item Ma, Jie
item MYRSELL, VERONICA - University Of Idaho
item DIETRICH, JOSEPH - National Oceanic & Atmospheric Administration (NOAA)
item CAIN, KENNETH - National Oceanic & Atmospheric Administration (NOAA)

Submitted to: Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: 2/12/2025
Publication Date: 3/6/2025
Citation: Ma, J., Myrsell, V., Dietrich, J., Cain, K.D. 2025. Development of rifampicin and novobiocin resistant Aeromonas salmonicida strains and their potential as live attenuated vaccine candidates [Abstract]. Aquaculture American 2025, New Orleans, Louisiana, March 6-10, 2025, p. 718.

Interpretive Summary: Scientists are tackling a fish disease called furunculosis, caused by the bacterium Aeromonas salmonicida. This disease is especially problematic for sablefish in the Pacific Northwest, where it results in high death rates, and currently, there are no commercial vaccines available for non-salmonid fish like sablefish. The goal of this study is to develop a live-attenuated vaccine that can be given to fish through immersion. Researchers created weakened strains of the bacterium using antibiotics (rifampicin and novobiocin) at increasing doses and by growing them at temperatures up to 30'. Tests showed these weakened strains were less harmful to sablefish and rainbow trout. A vaccine trial using one of these weakened strains (called A5) on rainbow trout showed promising results, with the fish producing strong immune responses whether they were vaccinated by immersion or injection. If further tests are successful, this new vaccine could help make fish farming more sustainable by reducing the impact of furunculosis on sablefish and other fish.

Technical Abstract: Aeromonas salmonicida, the causative agent of furunculosis, poses a significant threat to a diverse range of hosts in both fresh and marine fish. Currently, there are no commercial vaccines available to treat furunculosis in non-salmonid fish. Limited vaccine options exist to prevent furunculosis in sablefish specifically. This problem is evident as sablefish aquaculture has intensified in the Pacific Northwest, furunculosis continues to cause high mortality rates during production. The primary objective of this study is to develop a live-attenuated vaccine suitable for immersion administration, aiming to effectively treat furunculosis in sablefish for commercial aquaculture production. Attenuated strains of typical and atypical A. salmonicida were generated using rifampicin and novobiocin through successive passages on TSA with escalating concentrations of the antibiotics, reaching up to 400 mg/ml for both rifampicin and novobiocin. Resulting isolates were cultured at temperatures up to 30' for additional attenuation. Partial and full attenuation of A. salmonicida strains was confirmed through in vivo virulence challenges in sablefish and rainbow trout. Subsequently, an in vivo vaccine trial was conducted with the attenuated typical A. salmonicida Isolate (A5) in rainbow trout. The vaccination trial using the A5 isolate showed significant A. salmonicida specific IgM titers for both immersion and injection vaccination methods. Overall, the proposed live-attenuated vaccine candidates to prevent furunculosis in sablefish and rainbow trout could become an asset to sustainable aquaculture management if proven effective with further vaccination trials.