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Diseases of Aquatic Organisms

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DAO 144:151-158 (2021)  -  DOI:

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

Fernanda de Alexandre Sebastião1,7, Khalid Shahin1, Taylor I. Heckman1, Benjamin R. LaFrentz2, Matt J. Griffin 3, Thomas P. Loch4, Kaveramma Mukkatira5, Tresa Veek5, Christine Richey5, Mark Adkison5, Richard A. Holt6, Esteban Soto1,*

1Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, California 95616, USA
2USDA-ARS, Aquatic Animal Health Research Unit, Auburn, Alabama 36832, USA
3Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Stoneville, Mississippi 38776, USA
4Departments of Fisheries and Wildlife (College of Agriculture and Natural Resources) and Pathobiology and Diagnostic Investigation (College of Veterinary Medicine), Michigan State University, East Lansing, Michigan 48824, USA
5California Department of Fish and Wildlife, Rancho Cordova, California 95670, USA
6Department of Microbiology, Oregon State University, Corvallis, Oregon 97331, USA
7Present address: EMBRAPA Amazônia Ocidental, Fisheries Department, Manaus, Amazonas 69010-970, Brazil
*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 US 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. F. 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 trout (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 for fish health management. The results from this study provide baseline data for future work developing strategies to ameliorate columnaris-related losses in the US Pacific Northwest.

KEY WORDS: Columnaris · Genetic groups · gyrB · Multiplex-PCR · Rep-PCR

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Cite this article as: Sebastião FdA, Shahin K, Heckman TI, LaFrentz BR and others (2021) Genetic characterization of Flavobacterium columnare isolates from the Pacific Northwest, USA. Dis Aquat Org 144:151-158.

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