413
Chemotaxonomy Methods Chemotaxonomic characters, namely whole cell fatty
acid profi les and a commercial system, i.e. MIS – Microbial ID, have been used,
with the dominant fatty acids including 11-methyl-dodecanoic acid, 13-methyl tetradecanoic acid, pentadecanoic acid, 14-methyl-pentadecanoic acid, 3-hydroxy-13methyl tetradecanoic acid, 15-methyl cis 9-hexadecanoic acid, 3-hydroxy 14-methyl
pentadecanoic acid, 15-methyl cis 9-hexadecanoic acid, 3-hydroxy 14-methyl pentadecanoic acid and 3-hydroxy-15-methyl hexadecanoic acid (Shoemaker et al.
2005 ).
Serology Whole cell agglutination is effective for the detection of Fla. columnare
(Morrison et al. 1981 ). A relevant development has been the use of a rapid iFAT to
simultaneously detect two pathogens, i.e. Edw. ictaluri and Fla. columnare using
fl uorochromes with two different spectra properties, Alexa Fluor 488 and 594 emitting green and red fl uorescence, respectively (Panangala et al. 2006 ).
Molecular Methods PCR targeted 16S rRNA has been successful with Fla. branchiophilum, Fla. columnare and T. maritimum (Toyama et al. 1994 , 1996 ; AvendañoHerrera et al. 2004e ; Yeh et al. 2006 ). LAMP was used successfully to diagnose Fla.
columnare (Yeh et al. 2006 ; Suebsing et al. 2015 ). A highly specifi c and sensitive
(2.2 × 10
2 CFU) LAMP assay with the pre-addition of calcein was developed, in
which positivity in gill, gonad, blood, fermilised eggs and water, was recorded as
colour change from orange to green within 45 min at 63 °C (Suebsing et al. 2015 ).
A PCR targeting 16S rRNA has shown promise for the specifi c (negative for other
fl avobacteria) and sensitive (~100 cells) detection of Fla. columnare from culture
and fi sh tissues within 5–8 h. Also PCR based on the 16S-23S rDNA intergenic
spacer region has demonstrated promise for the detection of Fla. columnare from
catfi sh in terms of specifi city and sensitivity (capable of detecting 7 CFU). The
technique was regarded as more sensitive than culturing (Welker et al. 2005 ).
Epizootiology
The consensus is that the disease is problematic only in the warmer periods of the
year. Generally, epizootics occur when the water temperature is in the region of
18–22 °C, and the disease is rarely troublesome at <15 °C (Amend 1970 ). Thus,
most outbreaks of columnaris occur between May and October (Bowser 1973 ; Kuo
et al. 1981 ). To illustrate the dramatic effects of water temperature on the level of
mortalities, the investigation of Holt et al. ( 1975 ) is especially relevant. This team
challenged steelhead trout, chinook salmon and coho salmon with Fla. columnare,
via the water-borne route. At a water temperature of 9.4 °C there were no mortalities
attributable to columnaris. By increasing the temperature to 12.2 °C, 4–20 % mortalities ensued; whereas at 20.5 °C all the steelhead trout and coho salmon died,
together with 70 % of the chinook salmon.
Flavobacterium columnare (=Flexibacter/Cytophaga columnaris)
Chemotaxonomy Methods Chemotaxonomic characters, namely whole cell fatty
acid profi les and a commercial system, i.e. MIS – Microbial ID, have been used,
with the dominant fatty acids including 11-methyl-dodecanoic acid, 13-methyl tetradecanoic acid, pentadecanoic acid, 14-methyl-pentadecanoic acid, 3-hydroxy-13methyl tetradecanoic acid, 15-methyl cis 9-hexadecanoic acid, 3-hydroxy 14-methyl
pentadecanoic acid, 15-methyl cis 9-hexadecanoic acid, 3-hydroxy 14-methyl pentadecanoic acid and 3-hydroxy-15-methyl hexadecanoic acid (Shoemaker et al.
2005 ).
Serology Whole cell agglutination is effective for the detection of Fla. columnare
(Morrison et al. 1981 ). A relevant development has been the use of a rapid iFAT to
simultaneously detect two pathogens, i.e. Edw. ictaluri and Fla. columnare using
fl uorochromes with two different spectra properties, Alexa Fluor 488 and 594 emitting green and red fl uorescence, respectively (Panangala et al. 2006 ).
Molecular Methods PCR targeted 16S rRNA has been successful with Fla. branchiophilum, Fla. columnare and T. maritimum (Toyama et al. 1994 , 1996 ; AvendañoHerrera et al. 2004e ; Yeh et al. 2006 ). LAMP was used successfully to diagnose Fla.
columnare (Yeh et al. 2006 ; Suebsing et al. 2015 ). A highly specifi c and sensitive
(2.2 × 10
2 CFU) LAMP assay with the pre-addition of calcein was developed, in
which positivity in gill, gonad, blood, fermilised eggs and water, was recorded as
colour change from orange to green within 45 min at 63 °C (Suebsing et al. 2015 ).
A PCR targeting 16S rRNA has shown promise for the specifi c (negative for other
fl avobacteria) and sensitive (~100 cells) detection of Fla. columnare from culture
and fi sh tissues within 5–8 h. Also PCR based on the 16S-23S rDNA intergenic
spacer region has demonstrated promise for the detection of Fla. columnare from
catfi sh in terms of specifi city and sensitivity (capable of detecting 7 CFU). The
technique was regarded as more sensitive than culturing (Welker et al. 2005 ).
Epizootiology
The consensus is that the disease is problematic only in the warmer periods of the
year. Generally, epizootics occur when the water temperature is in the region of
18–22 °C, and the disease is rarely troublesome at <15 °C (Amend 1970 ). Thus,
most outbreaks of columnaris occur between May and October (Bowser 1973 ; Kuo
et al. 1981 ). To illustrate the dramatic effects of water temperature on the level of
mortalities, the investigation of Holt et al. ( 1975 ) is especially relevant. This team
challenged steelhead trout, chinook salmon and coho salmon with Fla. columnare,
via the water-borne route. At a water temperature of 9.4 °C there were no mortalities
attributable to columnaris. By increasing the temperature to 12.2 °C, 4–20 % mortalities ensued; whereas at 20.5 °C all the steelhead trout and coho salmon died,
together with 70 % of the chinook salmon.
Flavobacterium columnare (=Flexibacter/Cytophaga columnaris)