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Title: Growth and survival of the fish pathogenic bacterium, Flavobacterium columnare, in tilapia mucus and porcine gastric mucin

Author
item Shoemaker, Craig
item Lafrentz, Benjamin

Submitted to: FEMS Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2014
Publication Date: 7/8/2015
Publication URL: http://handle.nal.usda.gov/10113/62197
Citation: Shoemaker, C.A., Lafrentz, B.R. 2015. Growth and survival of the fish pathogenic bacterium, Flavobacterium columnare, in tilapia mucus and porcine gastric mucin. FEMS Microbiology Letters. 362(4):1-5.

Interpretive Summary: Flavobacterium columnare is an economically important gram negative bacterium that infects most freshwater farmed fish worldwide. Flavobacterium columnare colonizes the skin and gills of fish in the initial steps of infection. The fish’s surface is coated with mucus made up of high molecular weight glycoproteins. The objective of this study was to determine if F. columnare isolates of different genetic types (genomovars) could grow and survive in water containing sterilized (autoclaved) tilapia mucus or porcine gastric mucin (mucus purified from pig intestine). We demonstrated the ability of each F. columnare genetic type to grow and survive for at least 21 days and up to 100 days in water containing tilapia mucus as the nutrient source. In three other experiments, isolates were found to grow and survive in water containing tilapia mucus or porcine mucin as compared to water alone. From a practical standpoint, fish handling and/or hauling often results in stress that leads to mucus sloughing with F. columnare infections resulting. Research in trout suggests an increase in the expression of genes involved in mucus production and a reduction in antibacterial activity of mucus following stress which supports our findings. Presence of mucus or mucin proteins may potentially regulate gene expression and virulence of F. columnare on the fish and/or in the aquatic environment.

Technical Abstract: Flavobacterium columnare is an economically important gram negative bacterium that infects most freshwater farmed fish worldwide. Flavobacterium columnare colonizes the skin and gills of fish in the initial steps of pathogenesis. The fish’s surface is coated with mucus made up of high molecular weight glycoproteins. A few studies have described the ability of fish bacterial pathogens to grow and replicate in fish mucus or in media containing fish mucus. The objective of this study was to determine if F. columnare isolates of different genomovars could grow and survive in formulated water (FW) containing autoclaved tilapia mucus or porcine gastric mucin. In replicated flask experiments, we demonstrated the ability of F. columnare genomovars I, II, II-B and III to replicate (2-3 logs) and survive (21 to > 100 days) in FW containing tilapia mucus as the nutrient source. In three other replicated flask experiments, genomovar I and II isolates were found to replicate and survive in FW containing tilapia mucus or porcine mucin as compared to FW only. We further demonstrated differential mucinolytic activity of the isolates against porcine mucin in agar plate assays. From a practical standpoint, fish handling and/or hauling often results in stress that leads to mucus sloughing with F. columnare infections resulting. Flavobacterium columnare utilizes fish mucus as a source of nutrients and studies are underway to determine if growth in mucus or mucin results in differential protein expression and or increased virulence of F. columnare towards fish.