Submitted to: World Aquaculture Society Meeting
Publication Type: Proceedings
Publication Acceptance Date: November 23, 2009
Publication Date: March 1, 2010
Citation: Klesius, P.H., Wei Pridgeon, Y., Aksoy, M., Shoemaker, C.A., Evans, J.J. 2010. The role of the Flavobacterium columnare chemotactic response to skin mucus in virulence. Aquaculture 2010. p. 528. Technical Abstract: Flavobacterium columnare is a Gram-negative pathogen of many species of wild and cultured fish, especially channel catfish (Ictalurus punctatus). This bacterium is responsible for severe economic losses in the aquaculture industry. Flavobacterium columnare isolated from diseased channel catfish belongs to either genomovar I or II. Genomovar II isolates were found to be more virulent than genomovar I isolates. The objective of the present study was to determine if differences exist in the chemotactic response of these genomovars to mucus obtained from the skin, gills and intestines of healthy channel catfish using an in vitro chemotaxis assay. To achieve this objective, the motility (chemotactic response) of F. columnare from both genomovar I and II without mucus and with the presence of mucus from skin, gill and intestine from 15 individual healthy catfish was determined. Mucus from skin and gill induced a greater chemotactic response to F. columnare than mucus from the intestine. Sixty percent of mucus from the skin of individual catfish yielded a positive chemotactic response from F. columnare. Finally, skin mucus induced a greater chemotactic response by genomovar II F. columnare than for genomovar I F. columnare isolates. The data indicates that mucus from channel catfish induced chemotactic response of F. columnare. The chemotaxic response was significantly inhibited by treatment with sodium metaperiodate or D-mannose. The chemotactic response appears to involve the interaction between F. columnare lectin and D-mannose receptor associated with mucus. Although the role that chemotaxis plays in virulence of F. columnare is not fully defined, the chemotactic response of genomovar II isolates suggest that chemotaxis is associated with virulence. The differential gene expression levels of F. columnare genomovar II exposed to skin mucus were studied and their roles in virulence will be discussed.