557
Pacifi c salmon, there is a tendency for the formation of micro-colonies in the skeletal and heart muscle, gill tissue, and in both the anterior and posterior regions of the
gastro-intestinal tract (Ransom 1978 ; Ransom et al. 1984 ). Moreover, bacteraemia
developed much later in the disease cycle than with V. anguillarum. Perhaps, this
accounted for the lower numbers of bacterial cells in the blood. A further difference
concerned the marked decrease in the numbers of leucocytes in the blood, i.e. leucopenia (Ransom 1978 ; Harbell et al. 1979 ; Ransom et al. 1984 ).
Isolation
As with V. anguillarum, isolation involves use of seawater agar and TCBS with
incubation at 15–25 °C for up to 7 days (Ransom 1978 ; Ransom et al. 1984 ).
Characteristics of the Pathogen
The establishment of a new species to accommodate strains previously classifi ed as
V. anguillarum biotype II, i.e. V. ordalii (Schiewe 1981 ; Schiewe et al. 1981 ), generated an awareness that vibriosis could be caused by more than one bacterial taxon.
Box 10.13: Vibrio ordalii
Cultures comprise fermentative Gram-negative curved rods of 2.5–3.0 × 1.0 μm
in size, motile by means of single polar fl agella. Growth occurs quite slowly,
insofar as 4–6 days incubation at 22 °C are required for the production of offwhite, circular, convex colonies of 1–2 mm in diameter on seawater agar. V.
ordalii is, however, is not especially active. Catalase and oxidase are produced, but not arginine dihydrolase, ß-galactosidase, H 2 S, indole, lysine or
ornithine decarboxylase, or phenylalanine deaminase. DNA, chitin (by some
isolates) and gelatin are degraded, but not aesculin, lipids, pectate, starch or
urea. Nitrates are reduced by some isolates. The methyl red test and Voges
Proskauer reaction are negative. Tartrate is utilised. Only a few carbohydrates,
e.g. galactose (variable result), maltose, mannitol and sucrose are attacked
with the production of acid. Negative responses are recorded for adonitol,
arabinose, cellobiose, dulcitol, erythritol, glycerol, inositol, lactose, melibiose, raffi nose, rhamnose, salicin, sorbitol, trehalose and xylose. Growth
occurs at 15–22 °C but not at 37 °C and in 0.5–3.0 % but not 0 % or 7 % (w/v)
sodium chloride. Sensitivity is recorded to the vibriostatic agent, O/129. The
G + C ratio of the DNA is 43–44 moles % (Schiewe 1981 ; Schiewe et al. 1981 ;
Austin et al. 1997 ).
Vibrio ordalii
Pacifi c salmon, there is a tendency for the formation of micro-colonies in the skeletal and heart muscle, gill tissue, and in both the anterior and posterior regions of the
gastro-intestinal tract (Ransom 1978 ; Ransom et al. 1984 ). Moreover, bacteraemia
developed much later in the disease cycle than with V. anguillarum. Perhaps, this
accounted for the lower numbers of bacterial cells in the blood. A further difference
concerned the marked decrease in the numbers of leucocytes in the blood, i.e. leucopenia (Ransom 1978 ; Harbell et al. 1979 ; Ransom et al. 1984 ).
Isolation
As with V. anguillarum, isolation involves use of seawater agar and TCBS with
incubation at 15–25 °C for up to 7 days (Ransom 1978 ; Ransom et al. 1984 ).
Characteristics of the Pathogen
The establishment of a new species to accommodate strains previously classifi ed as
V. anguillarum biotype II, i.e. V. ordalii (Schiewe 1981 ; Schiewe et al. 1981 ), generated an awareness that vibriosis could be caused by more than one bacterial taxon.
Box 10.13: Vibrio ordalii
Cultures comprise fermentative Gram-negative curved rods of 2.5–3.0 × 1.0 μm
in size, motile by means of single polar fl agella. Growth occurs quite slowly,
insofar as 4–6 days incubation at 22 °C are required for the production of offwhite, circular, convex colonies of 1–2 mm in diameter on seawater agar. V.
ordalii is, however, is not especially active. Catalase and oxidase are produced, but not arginine dihydrolase, ß-galactosidase, H 2 S, indole, lysine or
ornithine decarboxylase, or phenylalanine deaminase. DNA, chitin (by some
isolates) and gelatin are degraded, but not aesculin, lipids, pectate, starch or
urea. Nitrates are reduced by some isolates. The methyl red test and Voges
Proskauer reaction are negative. Tartrate is utilised. Only a few carbohydrates,
e.g. galactose (variable result), maltose, mannitol and sucrose are attacked
with the production of acid. Negative responses are recorded for adonitol,
arabinose, cellobiose, dulcitol, erythritol, glycerol, inositol, lactose, melibiose, raffi nose, rhamnose, salicin, sorbitol, trehalose and xylose. Growth
occurs at 15–22 °C but not at 37 °C and in 0.5–3.0 % but not 0 % or 7 % (w/v)
sodium chloride. Sensitivity is recorded to the vibriostatic agent, O/129. The
G + C ratio of the DNA is 43–44 moles % (Schiewe 1981 ; Schiewe et al. 1981 ;
Austin et al. 1997 ).
Vibrio ordalii