515
Isolation
Pure cultures may be readily recovered from blood and kidney samples on TSA
supplemented with 1.5 % (w/v) sodium chloride following incubation at 15 °C for
up to 5 days (Holm et al. 1985 ; Egidius et al. 1986 ). Colonies are small, i.e. ≤1 mm
in diameter, round, raised, entire and translucent. Unexperienced personnel could
easily miss the colonies upon cursory glances at inoculated plates. To some extent,
the organism is fragile, and will quickly die at supra-optimum temperatures or by
failure to carry out regular sub-culturing.
Characteristics of the Pathogen
An organism, named originally as V. salmonicida , was recovered from diseased
salmon (Egidius et al. 1986 ), and the validity and distinctiveness confi rmed (Austin
et al. 1997 ). However, the organism was transferred to the newly created genus
Aliivibrio as Ali. salmonicida on the basis of phylogeny principally involving
sequencing of the 16S rRNA gene (Urbanczyk et al. 2007 ).
Strains have been divided into four different categories on the basis of plasmid
profi les (Wiik et al. 1989 ). The plasmids were 2.6, 3.4 and 24 mDa in size; with the
largest plasmid being common to all four groups. There was no apparent difference
in biochemical traits among these four plasmid groups. In a separate study, Sørum
et al. ( 1990 ) described plasmids of 2.8, 3.4, 21 and 61 mDa from isolates recovered
from Atlantic salmon and cod. These authors reported 11 plasmid profi les for Ali.
Box 10.4: Aliivibrio salmonicida
Cultures contain motile (~9 polar fl agella) fermentative Gram-negative curved
pleomorphic rods of 2–3 × 0.5 μm in size. Catalase and oxidase are produced, but
not arginine dihydrolase, ß-galactosidase, H 2 S or indole. Nitrates are not reduced,
nor is the Voges Proskauer reaction positive. Citrate is not utilised. Neither blood,
chitin, gelatin, lipids nor urea are degraded. N-acetylglucosamine, glucose, glycerol (slowly), maltose, ribose, sodium gluconate and trehalose are utilised, but
not adonitol, amygdalin, D- or L-arabinose, D- or L-arabitol, arbutin,
D-cellobiose, dulcitol, erythritol, D- or L-fucose, inositol, ß- gentobiose, lactose,
D-lycose, D-mannose, melezitose, melibiose, D-raffi nose, rhamnose, salicin,
sorbitol, sucrose, L-sorbose, D-tagatose, D-turanose or D- or L-xylose. Growth
occurs at 1–22 °C, optimally at 15 °C but not at 37 °C, and in 0–4 % but not 7 %
(w/v) sodium chloride. Sensitivity is displayed to the vibriostatic agent, O/129,
but not to novobiocin. The G + C ratio of the DNA is 44 moles % (Holm et al.
1985 ; Egidius et al. 1986 ).
Aliivibrio salmonicida
Isolation
Pure cultures may be readily recovered from blood and kidney samples on TSA
supplemented with 1.5 % (w/v) sodium chloride following incubation at 15 °C for
up to 5 days (Holm et al. 1985 ; Egidius et al. 1986 ). Colonies are small, i.e. ≤1 mm
in diameter, round, raised, entire and translucent. Unexperienced personnel could
easily miss the colonies upon cursory glances at inoculated plates. To some extent,
the organism is fragile, and will quickly die at supra-optimum temperatures or by
failure to carry out regular sub-culturing.
Characteristics of the Pathogen
An organism, named originally as V. salmonicida , was recovered from diseased
salmon (Egidius et al. 1986 ), and the validity and distinctiveness confi rmed (Austin
et al. 1997 ). However, the organism was transferred to the newly created genus
Aliivibrio as Ali. salmonicida on the basis of phylogeny principally involving
sequencing of the 16S rRNA gene (Urbanczyk et al. 2007 ).
Strains have been divided into four different categories on the basis of plasmid
profi les (Wiik et al. 1989 ). The plasmids were 2.6, 3.4 and 24 mDa in size; with the
largest plasmid being common to all four groups. There was no apparent difference
in biochemical traits among these four plasmid groups. In a separate study, Sørum
et al. ( 1990 ) described plasmids of 2.8, 3.4, 21 and 61 mDa from isolates recovered
from Atlantic salmon and cod. These authors reported 11 plasmid profi les for Ali.
Box 10.4: Aliivibrio salmonicida
Cultures contain motile (~9 polar fl agella) fermentative Gram-negative curved
pleomorphic rods of 2–3 × 0.5 μm in size. Catalase and oxidase are produced, but
not arginine dihydrolase, ß-galactosidase, H 2 S or indole. Nitrates are not reduced,
nor is the Voges Proskauer reaction positive. Citrate is not utilised. Neither blood,
chitin, gelatin, lipids nor urea are degraded. N-acetylglucosamine, glucose, glycerol (slowly), maltose, ribose, sodium gluconate and trehalose are utilised, but
not adonitol, amygdalin, D- or L-arabinose, D- or L-arabitol, arbutin,
D-cellobiose, dulcitol, erythritol, D- or L-fucose, inositol, ß- gentobiose, lactose,
D-lycose, D-mannose, melezitose, melibiose, D-raffi nose, rhamnose, salicin,
sorbitol, sucrose, L-sorbose, D-tagatose, D-turanose or D- or L-xylose. Growth
occurs at 1–22 °C, optimally at 15 °C but not at 37 °C, and in 0–4 % but not 7 %
(w/v) sodium chloride. Sensitivity is displayed to the vibriostatic agent, O/129,
but not to novobiocin. The G + C ratio of the DNA is 44 moles % (Holm et al.
1985 ; Egidius et al. 1986 ).
Aliivibrio salmonicida