478
intestine full of yellowish exudate. Low level mortalities, albeit in the absence of
external signs of disease, were reported in black spot sea bream in Spain (LópezRomalde et al. 2003 ).
Isolation
Isolation of Ps. anguilliseptica is readily achieved from blood, kidney, liver and
spleen samples by use of nutrient agar supplemented with 10 % (v/v) horse blood or
nutrient agar containing 0.5 % (w/v) sodium chloride, and adjusted to a pH of 7.4.
Incubation should be at 20–25 °C for at least 7 days, when small (≤1 mm in diameter) round, raised, entire, shiny, pale-grey colonies develop (Wakabayashi and
Egusa 1972 ).
Characteristics of the Pathogen
On the basis of phenotypic traits, evidence suggests that isolates are homogenous
(López-Romalde et al. 2003 ). However, other approaches have detected some variation. Thus, a comprehensive examination of 96 isolates indicated the presence of
two antigenic groups. Type I was not agglutinated in unheated antisera (this was
prepared against heat-killed cells), although clumping (agglutination) of the cells
subsequently occurred after the antiserum was heated to 100 °C for 2 h (or 121 °C
Box 9.2: Pseudomonas anguilliseptica
A homogeneous group of Gram-negative asporogenous rods, which are motile
by means of single polar fl agella. Electron microscopy of 18-h-old cultures on
TSA reveal the presence of long, slightly curved rods with rounded ends. The
size of these cells has been estimated as 5–10 × 0.8 μm. In addition, many
bizarre forms have been observed. Fluorescent pigment is not produced.
There is no reaction in the oxidative-fermentative test. Catalase and oxidase
are produced, but not arginine dihydrolase, ß-galactosidase, H 2 S or indole.
Nitrates are not reduced. Gelatin, Tween 20 (variable result) and Tween 80 are
degraded, but not blood, DNA, starch (variable result) or urea. Acid is not
produced from arabinose, fructose, galactose, glucose, glycerol, inositol, lactose, maltose, mannitol, mannose, raffi nose, rhamnose, salicin, sucrose or
xylose. Citrate is utilised by some isolates. Growth occurs at 5–30 °C but not
37 °C, in 0–4 % (w/v) sodium chloride, and at pH 5.3–9.7. The G + C ratio of
the DNA is 56.5–57.4 mol% (Wakabayashi and Egusa 1972 ; Muroga et al.
1977 ; Nakai and Muroga 1982 ; Stewart et al. 1983 ; López-Romalde et al.
2003 ).
9 Pseudomonads
intestine full of yellowish exudate. Low level mortalities, albeit in the absence of
external signs of disease, were reported in black spot sea bream in Spain (LópezRomalde et al. 2003 ).
Isolation
Isolation of Ps. anguilliseptica is readily achieved from blood, kidney, liver and
spleen samples by use of nutrient agar supplemented with 10 % (v/v) horse blood or
nutrient agar containing 0.5 % (w/v) sodium chloride, and adjusted to a pH of 7.4.
Incubation should be at 20–25 °C for at least 7 days, when small (≤1 mm in diameter) round, raised, entire, shiny, pale-grey colonies develop (Wakabayashi and
Egusa 1972 ).
Characteristics of the Pathogen
On the basis of phenotypic traits, evidence suggests that isolates are homogenous
(López-Romalde et al. 2003 ). However, other approaches have detected some variation. Thus, a comprehensive examination of 96 isolates indicated the presence of
two antigenic groups. Type I was not agglutinated in unheated antisera (this was
prepared against heat-killed cells), although clumping (agglutination) of the cells
subsequently occurred after the antiserum was heated to 100 °C for 2 h (or 121 °C
Box 9.2: Pseudomonas anguilliseptica
A homogeneous group of Gram-negative asporogenous rods, which are motile
by means of single polar fl agella. Electron microscopy of 18-h-old cultures on
TSA reveal the presence of long, slightly curved rods with rounded ends. The
size of these cells has been estimated as 5–10 × 0.8 μm. In addition, many
bizarre forms have been observed. Fluorescent pigment is not produced.
There is no reaction in the oxidative-fermentative test. Catalase and oxidase
are produced, but not arginine dihydrolase, ß-galactosidase, H 2 S or indole.
Nitrates are not reduced. Gelatin, Tween 20 (variable result) and Tween 80 are
degraded, but not blood, DNA, starch (variable result) or urea. Acid is not
produced from arabinose, fructose, galactose, glucose, glycerol, inositol, lactose, maltose, mannitol, mannose, raffi nose, rhamnose, salicin, sucrose or
xylose. Citrate is utilised by some isolates. Growth occurs at 5–30 °C but not
37 °C, in 0–4 % (w/v) sodium chloride, and at pH 5.3–9.7. The G + C ratio of
the DNA is 56.5–57.4 mol% (Wakabayashi and Egusa 1972 ; Muroga et al.
1977 ; Nakai and Muroga 1982 ; Stewart et al. 1983 ; López-Romalde et al.
2003 ).
9 Pseudomonads