Abstract
Flavobacterium columnare is the causative agent of columnaris disease in freshwater fish, implicated in skin and gill disease, often causing high mortality. The aim of this study was the isolation and characterization of Flavobacterium columnare in tropical fish in Brazil. Piracanjuba (Brycon orbignyanus), pacu (Piaractus mesopotamicus), tambaqui (Colossoma macropomum) and cascudo (Hypostomus plecostomus) were examined for external lesions showing signs of colunmaris disease such as greyish white spots, especially on the head, dorsal part and caudal fin of the fish. The sampling comprised 50 samples representing four different fish species selected for study. Samples for culture were obtained by skin and kidney scrapes with a sterile cotton swabs of columnaris disease fish and streaked onto Carlson and Pacha (1968) artificial culture medium (broth and solid) which were used for isolation. The strains in the liquid medium were Gram negative, long, filamentous, exhibited flexing movements (gliding motility), contained a large number of long slender bacteria and gathered into columns'. Strains on the agar produced yellow-pale colonies, rather small, flat that had rhizoid edges. A total of four Flavobacterium columnare were isolated: 01 Brycon orbignyanus strain, 01 Piaractus mesopotamicus strain, 01 Colossoma macropomum strain, and 01 Hypostomus plecostomus strain. Biochemical characterization, with its absorption of Congo red dye, production of flexirubin-type pigments, H2S production and reduction of nitrates proved that the isolate could be classified as Flavobacterium columnare.
Highlights
Flavobacterium columnare the agent of columnaris disease was first described by Davis in 1922 as Bacillus columnaris and it was isolated by Ordal and Rucker (1944) and called Chondrococcus columnaris
Isolation of Flavobacterium columnare strains from tropical fish
From 50 samples, 04 strains of Flavobacterium columnare were isolated from kidney fish with ulcerated skin and discoloration on their caudal fin
Summary
Flavobacterium columnare the agent of columnaris disease was first described by Davis in 1922 as Bacillus columnaris and it was isolated by Ordal and Rucker (1944) and called Chondrococcus columnaris. Epizootics of columnaris are rarely spontaneous and have been troublesome in hatcheries, pen, cage culture and in pond culture, under adverse environmental conditions and factors stressful to the fish. These factors are correlated with rising water temperature, excessive foreign matter in the water, high stocking density or poor conditions (Wood and Yasutake, 1957; Wakabayashi, 1991; Kinnunen et al, 1997; Decostere et al, 1998) which cause enormous economic damage every year in many countries (Foscarini, 1989; Arias et al, 2004). Skin scraping or gill squash preparations from fish with cutaneous columnaris reveal large numbers of long, rodshaped bacteria arranged in columns or hay stacks (Newton et al, 1997)
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