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

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.

Flavobacterium covae is the predominant species of columnaris‐causing bacteria impacting the Channel Catfish industry in the southeastern United States

“…2012; Evenhuis and LaFrentz 2016), although columnaris disease cases due to F. davisii have recently been reported in California (de Alexandre Sebastião et al. 2021). Interestingly, these two CCB species are capable of growth at colder temperatures (LaFrentz et al.…”

Shotgun Metagenomic Analyses of Microbial Assemblages in the Aquatic Ecosystem of Winam Gulf of Lake Victoria, Kenya Reveals Multiclass Pollution

“…Gammaproteobacteria are widely distributed and abundant in various ecosystems such as soils, freshwater lakes, and rivers [41].The phylum Bacteroidetes is diverse which includes Flexibacter, Cytophaga, and Bacteroides [42,43]. The Bacteroidetes phylum is made up of four classes: Flavobacteria, Bacteriode, Sphingobacteria, and Cytophaga, with over 7,000 diverse species [44]. The Bacteroidetes phylum found in the Winam Gulf included the Flavobacteria, Bacteriodiia unassigned, and unclassified Bacteriodetes.…”

“…Flavobacteria which is made up of many aquatic species). Falvobacteria contains species of opportunistic human pathogens and antimicrobial-resistant genes [44]. Bacteroidetes species have economic impacts on freshwater fish, which cause infections that may have negative effects on wild and farmed fish [45,46].…”

Diagnosis, isolation and description of a novel amnoonvirus recovered from diseased fancy guppies, Poecilia reticulata

“…(Hossain et al., 2020; Lazado & Zilberg, 2018), Mycobacterium spp. (Pate et al., 2005; Sakai et al., 2005) and columnaris‐causing bacteria (Declercq et al., 2013; de Sebastião et al., 2021). Nonetheless, only a few viruses have been isolated and reported from guppies (Hedrick & McDowell, 1995; Hegde et al., 2003).…”