Diversity of Fish-Associated Flavobacteria of Michigan

Abstract Flavobacteriosis poses a serious threat to wild and propagated fish stocks alike, accounting for more fish mortality in Michigan and its associated state fish hatcheries than all other pathogens combined. Although this consortium of fish diseases has primarily been attributed to Flavobacterium psychrophilum, F. columnare, and F. branchiophilum, herein we describe a diverse assemblage of Flavobacterium and Chryseobacterium spp. isolates recovered from diseased as well as apparently healthy wild, feral, and farmed fish of Michigan. Among 254 fish-associated flavobacterial isolates recovered from 21 fish species during 2003–2010, 211 were identified as Flavobacterium spp., whereas 43 were identified as Chryseobacterium spp. according to ribosomal RNA partial gene sequencing and phylogenetic analysis. Although F. psychrophilum and F. columnare were indeed associated with multiple fish mortality events, many previously uncharacterized flavobacteria were recovered from systemically infected fish showin...