DAO 63:129-138 (2005)  -  doi:10.3354/dao063129

Transmission and detection of Flavobacterium columnare in channel catfish Ictalurus punctatus

Thomas L. Welker1,*, Craig A. Shoemaker1, Covadonga R. Arias2, Phillip H. Klesius1

1Aquatic Animal Health Research Laboratory, Agricultural Research Service, United States Department of Agriculture, PO Box 952, Auburn, Alabama 36831, USA
2Department of Fisheries & Allied Aquacultures, Auburn University, Auburn, Alabama 36849, USA

ABSTRACT: A specific and rapid PCR detection method for Flavobacterium columnare based on the 16S-23S rDNA intergenic spacer region (ISR) of the ribosomal RNA operon has been developed. The ISR of 30 F. columnare strains and other Flavobacterium species was amplified using universal primers 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 7 colony forming units from pure culture by PCR. The new PCR detection method was applied to experimentally infected channel catfish. Two different experiments in which channel catfish fingerlings were infected by intramuscular injection or by immersion bath showed the advantage of the PCR method over standard culture techniques. F. 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 without fish-to-fish contact. The newly 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.

KEY WORDS: Flavobacterium columnare · Columnaris disease · PCR · Channel catfish · Detection

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