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Title: PRODUCTION, CHARACTERIZATION AND EVALUATION OF VIRULENCE OF AN ADHESION DEFECTIVE MUTANT OF FLAVOBACTERIUM COLUMNARE PRODUCED BY B-LACTUM SELECTION

Author
item Bader, Joel
item Shoemaker, Craig
item Klesius, Phillip

Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2004
Publication Date: 1/1/2005
Citation: Bader, J.A., Shoemaker, C.A., Klesius, P.H. 2005. Production, characterization and evaluation of virulence of an adhesion defective mutant of flavobacterium columnare produced by b-lactum selection. Letters in Applied Microbiology. Vol. 40: 123-127.

Interpretive Summary: Flavobacterium columnare is the causative agent of columnaris disease. This disease is a cause of great economic loses in cultured catfish in the United States and in a number of other cultured fish species world-wide. Annual loses attributed to columnaris disease are estimated at $50-60 million to the catfish industry. This study reports on the simple and rapid production of mutants of F. columnare by selection on plates containing the antibiotic, ampicillin, and is significant because 1) these are the first mutants to be produced on a selective media for the species, as opposed to mutants selected from a none-selective media, and 2) one of these is a mutant that lacks or has reduced ability to adhere to fish tissues. We have produced two major mutants that are resistant to the antibiotic ampicillin resistant, designated MB and MC, that differed from the parent strain, ARS-1 in colony morphologies and a protein with the apparent molecular weight of 40 kDa. The mutant MB differs from ARS and MC in an additional protein with the apparent molecular weight of 50 kDa. Further MB can not adhere to skin and adheres to the gill less efficiently than does its parent ARS-1. The mutant MB can help to can serve as a tool for the future study of the role of adhesion in the pathogenesis of columnaris disease. In this study, using mutant MB, we have already observed that adhesion is not necessary for the development of columnaris disease, but rather for the initial stages of infection and this infection process can begin on the skin or on the gill.

Technical Abstract: The aim of this study was to develop and evaluate mutants of Flavobacterium columnare, the causative agent of columnaris disease in fish. Serial passage on ampicillin ( -lactam) enriched modified Hsu-Shotts medium resulted in a F. columnare mutant that differed from the parent strain in colony morphology, whole cell proteins, adhesion and virulence. The mutant differed from its parent in virulence during immersion challenge, but not during injection challenge or generation of antibodies. Flavobacterium columnare exposure to ampicillin produces both resistance to that antibiotic and produces mutants that lack or have reduced adhesion characteristics and modified ability to adhere to fish tissue. This is the first description of an adhesion-defective mutant of F. columnare and the effects of altered adhesion on columnaris disease. This mutant has considerable potential as a tool to study the role of adhesion in columnaris disease.