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United States Department of Agriculture

Agricultural Research Service

Title: Transmission and Detection of Flavobacterium Columnare in Channel Catfish, Ictalurus Punctatus (Rafinesque)

Authors
item Welker, Thomas
item Shoemaker, Craig
item Arias, Covadonga - AUBURN UNIVERSITY
item Klesius, Phillip

Submitted to: Diseases of Aquatic Organisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 12, 2004
Publication Date: February 28, 2005
Citation: Welker, T.L., Shoemaker, C.A., Arias, C.R., Klesius, P.H. 2005. Transmission and detection of Flavobacterium columnare in channel catfish, Ictalurus punctatus. Diseases of Aquatic Organisms. 63: 129-138.

Interpretive Summary: Flavobacterium columnare, the causative agent of columnaris disease, is known to infect at least 36 species of fish and is second only to Edwardsiella ictaluri in economic impact to the commercial channel catfish industry in the United States. Timely and accurate identification of columnaris disease is important in controlling the spread of the disease and in lessening the impact to farmers. We developed a specific and rapid detection method by polymerase chain reaction (PCR) for Flavobacterium columnare based on the 16S-23S rDNA intergenic spacer region. The method was used to screen thirty F. columnare strains as well as the type strains of other Flavobacterium species. Only F. columnare produced positives by our PCR method. The method is sensitive and able to detect as few as seven colony forming units. The new PCR detection method was applied to experimentally infected channel catfish. In two different infection experiments, Flavobacterium columnare was detected by PCR in both tank water and catfish tissue samples with a higher frequency and in less time than standard microbiological methods. Furthermore, PCR detection confirmed that F. columnare can be transmitted horizontally indirectly through the water column and directly by fish-to-fish contact. Our PCR method is specific, allows detection of F. columnare in less than 8 h from fish and water samples, and is more sensitive than standard culture on bacteriological media.

Technical Abstract: A specific and rapid PCR detection method for Flavobacterium columnare based on the 16S-23S rDNA intergenic spacer region (ISR) of the ribosomic operon has been developed. The ISR sequence of thirty F. columnare strains, as well as the type strains of other Flavobacterium species, was amplified using universal primers, cloned, and sequenced. Once F. columnare specific sequences within the ISR were recognized, specific PCR primers were designed against them (FCISRFL and FCISRR1). The primers were sensitive and able to detect as low as seven colony forming units. The new PCR detection method was applied to experimentally infected channel catfish. Two different experiments, in which channel catfish fingerlings infected by intramuscular injection or by immersion bath, showed the advantage of the PCR method over standard culture techniques. Flavobacterium columnare was detected by PCR in both tank water and catfish tissue samples with a higher frequency and in less time than standard microbiological methods. Furthermore, PCR detection confirmed that F. columnare can be transmitted horizontally indirectly through the water column and directly by fish-to-fish contact. The new developed PCR detection method for F. columnare was more sensitive and rapid than standard culture on bacteriological media for detection of F. columnare in channel catfish tissues and in tank water.

Last Modified: 10/1/2014
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