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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03588

    Genetic characterization of Flavobacterium columnare isolates from the Pacific Northwest, USA

    Fernanda de Alexandre SebastiĆ£o, Khalid Shahin, Benjamin R. LaFrentz, Matt J. Griffin, Thomas P. Loch, Kaveramma Mukkatira, Tresa Veek, Christine Richey, Mark Adkison, Richard A. Holt, Esteban Soto*

    *Corresponding author:

    ABSTRACT: Flavobacterium columnare is the causative agent of columnaris disease. Previous work has demonstrated a high degree of genetic variability among F. columnare isolates, identifying 4 genetic groups (GGs), with some host associations. Herein, a total of 49 F. columnare isolates were characterized, the majority of which were collected from 15 different locations throughout the United States Pacific Northwest. Most isolates were collected from 2015–2018 and originated from disease outbreaks in salmonid hatcheries and rearing ponds, sturgeon hatcheries and ornamental fish. Other isolates were part of collections recovered from 1980–2018. Initial identification was confirmed by F. columnare species-specific qPCR. Study isolates were further characterized using a multiplex PCR that differentiates between the 4 currently recognized F. columnare GGs. Multiplex PCR results were supported by repetitive sequence mediated PCR fingerprinting and gyrB sequence analysis. Flavobacterium columnare GG1 was the most prevalent (83.7%, n = 41/49), represented by isolates from salmonids (n = 32), white sturgeon (n = 2), channel catfish (n = 1), ornamental goldfish (n = 1), koi (n = 3), wild sunfish (n = 1) and 1 unknown host. Six isolates (12.2%. n = 6/49) were identified as GG3, which were cultured from rainbow (n = 3) and steelhead trout (n = 3). Two isolates were identified as GG2 (4.1%, n = 2/49) and were from ornamental fish. No GG4 isolates were cultured in this study. The biological significance of this genetic variability remains unclear, but this variation could have significant implications in fish health management. The results from this study provide baseline data for future work developing strategies to ameliorate columnaris related losses in the United States Pacific Northwest.