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Research Project: Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture

Location: Aquatic Animal Health Research

Title: Characterization of atypical Flavobacterium columnare and identification of a new genomovar

item Garcia, Julio
item Lafrentz, Benjamin
item Waldbieser, Geoffrey - Geoff
item WONG, FONG - Merck Animal Health
item CHANG, SIOW - Merck Animal Health

Submitted to: American Fishery Society (Fish Health Section) Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2017
Publication Date: 3/30/2017
Citation: Garcia, J.C., Lafrentz, B.R., Waldbieser, G.C., Wong, F.S., Chang, S.F. 2017. Characterization of atypical Flavobacterium columnare and identification of a new genomovar. In: Annual Meeting of the Fish Health Section, American Fisheries Society, East Lansing, Michigan, April 2-3, 2017. p. 67.

Interpretive Summary:

Technical Abstract: Flavobacterium columnare is the etiological agent of columnaris disease and is the second most prevalent disease in farm-raised channel catfish. This is a Gram-negative bacterium characterized by adherent yellow pigmented rhizoid colonies. It can be further described by gliding motility, growth in the presence of neomycin sulfate and polymyxin B, production of a gelatin degrading enzyme, binding of Congo red and production of an enzyme that degrades chondroitin sulfate A. A group of presumptive F. columnare isolates arrived to our laboratory for analysis and three presented atypical characteristics, prompting further study. Isolates were characterized by phenotypic characteristics, enzymatic analysis, FAME composition, PCR using species specific primers, and 16S-RFLP. Following growth on modified Shieh agar, isolate TI982 formed an uncharacteristic white rhizoid colony, isolate EE923 exhibited typical colonies but produced a diffusible brownish red pigment, and isolate CC1351 exhibited typical colonies. Each isolate grew in the presence of neomycin sulfate and polymyxin B, bound to Congo red dye and produced a diffusible enzyme that degraded chondroitin sulfate. Isolate TI982 was negative for flexirubin-type pigment, while the others were positive. API ZYM enzymatic reactions and FAME analysis results were consistent with previous reports for F. columnare. All isolates were confirmed as F. columnare using species specific primers targeting the 16S-23S rRNA ISR, and 16S-RFLP assigned isolates TI982 and EE923 to genomovar II. RFLP analysis of isolate CC1351 resulted in a unique restriction pattern, not previously observed for F. columnare. The unique restriction pattern was corroborated by cloning and sequencing of the 16S rRNA genes, and this isolate was assigned as a new genomovar, II-A. Here we report on an isolate negative for flexirubin-type pigment and an isolate that produced a brownish red pigment, which are atypical characteristics not previously reported for F. columnare. Additionally we describe a new genomovar, II-A.