Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2008
Publication Date: 10/1/2008
Citation: Soto, E., Mauel, M.J., Karsi, A., Lawrence, M.L. 2008. Genetic and Virulence Diversity of Flavobacterium columnare. Journal of Applied Microbiology. 104:1302-1310. Interpretive Summary: A form of DNA fingerprinting (Pulse Field Gel Electrophoresis, PFGE) was optimized to characterize Flavobacterium columnare isolates from channel catfish. The protocol was able to determine that two genetic divisions of F. columnare channel catfish isolates exist, and that isolates in PFGE group A tend to be more pathogenic to channel catfish fingerlings than PFGE group B isolates. Future research should explore the difference between these groups in order to understand the virulence factors that permit group A to cause disease in healthy catfish fingerlings.
Technical Abstract: Aim: To develop a method for conducting pulsed-field gel electrophoresis (PFGE) on Flavobacterium columnare, to use PFGE to characterize F. columnare channel catfish isolates, and to determine whether variation in pathogenic potential exists in F. columnare isolates from channel catfish. Methods and Results: On the basis of PFGE-derived profiles, similarity dendrograms constructed for more than 30 F. columnare isolates showed two major genetic groups with more than 60% similarity. Channel catfish fingerlings challenged with PFGE group A isolates by bath immersion had significantly higher average mortalities (>60%) than fish challenged with PFGE group B isolates (<9%). However, abrasion and skin mucus removal made channel catfish fingerlings susceptible to disease caused by group B isolates following immersion exposure. Conclusion: Our results suggest that two genetic divisions of F. columnare channel catfish isolates exist, and that isolates in PFGE group A tend to be more pathogenic to immunocompetent channel catfish fingerlings than PFGE group B isolates. Significance and Impact of the Study: PFGE is a potentially useful tool for determining whether F. columnare isolates are more likely to be primary or secondary pathogens. Pathogenesis research for columnaris disease in catfish should focus on pathogenic isolates from PFGE group A.