Investigation of the genus Flavobacterium as a reservoir for fish-pathogenic bacterial species: the case of Flavobacterium collinsii

Abstract

Bacteria of the genus Flavobacterium are recovered from a large variety of environments. Among the described species, Flavobacterium psychrophilum and Flavobacterium columnare are causing considerable losses in fish farms. Alongside these well-known fish-pathogenic species, isolates belonging to the same genus recovered from diseased or apparently healthy wild, feral, and farmed fish have been suspected to be pathogenic. Here, we report the identification and genomic characterization of a F. collinsii isolate (TRV642) retrieved from rainbow trout spleen. A phylogenetic tree of the genus built by aligning the core genome of 195 Flavobacterium species revealed that F. collinsii is standing within a cluster of species associated to diseased fish, the closest one being F. tructae which was recently confirmed as pathogenic. We evaluated the pathogenicity of F. collinsii TRV642 as well as of F. bernardetii F-372T, another recently described species reported as a possible emerging pathogen. Following intramuscular injection challenges in rainbow trout, no clinical signs nor mortalities were observed. However, F. collinsii was isolated from the internal organs of wounded fish, suggesting that the bacterium could invade fish under compromised conditions such as stress and/or wounds. Our results suggest that some fish-associated Flavobacterium species should be considered as opportunistic fish pathogens causing disease under specific circumstances.

Experimental challenge of Chinook salmon withTenacibaculum maritimumandTenacibaculum dicentrarchifulfils Koch’s postulates

“…reported thereafter [28,31,54,55]. Assigning disease causation and confirming whether a ubiquitous microorganism is an infectious agent or is commensal flora of the host remains a challenge for diagnostic microbiologists, specifically for topical diseases [38,56,57]. Although most salmonids are susceptible to tenacibaculosis [15], it was reported that Pacific salmon species in the Pacific Northwest were resistant to mouth-rot disease caused by T. maritimum [see 8].…”

Evaluation of prokaryotic and eukaryotic microbial communities on microplastic‐associated biofilms in marine and freshwater environments

“…At the species level, 17 predominant bacterial species are presented in Figure 4B, constituting approximately 50% of the total plastisphere and each exceeding 1% in average abundance in one sample. Recently confirmed as a pathogenic agent, particularly affecting fish, Flavobacterium tructae with an abundance of 9%, was found to be the most prevalent species among the plastisphere community [27]. Arenimonas maotaiensis , a freshwater bacterium, made the second‐largest contribution to the plastisphere community with an abundance of 6%.…”

Fish predation risk alters the microbiota of Daphnia in the process of inducing its life‐history defence traits

“…In agreement with previous reports (Akbar et al., 2020, 2021; Callens et al., 2016; Freese & Schink, 2011), Proteobacteria and Bacteroidetes were the dominant bacterial phyla in D. magna guts in the present study. Among these, Flavobacteriaceae was the main component family of Bacteroidetes phyla, which is an opportunistic pathogen that is commonly found in aquatic animals and is capable of causing disease under specific conditions (Lee et al., 2023). Preiswerk et al.…”