506
which are approximately 1–2 mm in diameter after 72 h (Kusuda and Yamaoka
1972 ). Another approach, which has met with success, has enabled the recovery of
Ph. damselae subsp. piscicida from water in the vicinity of fi sh. The method
involved fi ltering 250 ml volumes of water through 0.45 μm cellulose nitrate fi lters,
before transfer (of the fi lters) to 2216E agar supplemented with 1 % (w/v) mannitol
and 0.5 % (w/v) phenol red. The non-fermenting Ph. damselae subsp. piscicida produced red colonies (Reali et al. 1997 ). With this method, the pathogen was detected
on sea bass 8-days before the outbreak of disease.
Characteristics of the Pathogen
In addition to the articles about pasteurellosis/pseudotuberculosis, there are also
some reports indicating the presence of fi sh pathogenic Pasteurella in Great Britain
(Ajmal and Hobbs 1967 ) and Norway (Håstein and Bullock 1976 ). However, it is
possible that these organisms should have been identifi ed as atypical Aer. salmonicida (see Paterson et al. 1980 ).
Box 10.2: Photobacterium damselae subsp. piscicida
Cultures comprise fairly unreactive, Gram-negative, non-motile, fermentative
rods of 0.5 × 1.5 μm in size, with pronounced bipolar staining. Pleomorphism
may be evident, especially in older cultures. Catalase and oxidase are produced, but not alanine deaminase, ß-galactosidase, H 2 S, indole, lysine or ornithine decarboxylase or phenylalanine deaminase. Nitrates are not reduced.
The methyl red test is strongly positive, whereas the Voges Proskauer reaction
is weakly positive. Arginine and Tween 80 are degraded, but not blood, casein,
chitin, gelatin, starch or urea. Growth occurs at 25–30 °C but not 10 or 37 °C,
in 0.5–3.0 % (w/v) sodium chloride and at pH 5.5–8.0, but not on MacConkey
agar or in potassium cyanide broth. Uniform turbidity is recorded in broth
cultures. Sodium citrate is not utilised. Acid is produced from fructose, galactose, glucose (weak) and mannose, but not amygdalin, arabinose, dulcitol,
inositol, lactose, maltose, mannitol, melibiose, rhamnose, salicin, sorbitol,
sucrose or trehalose. Unfortunately, the G + C ratio of the DNA has not been
determined for any bona fi de strains. So far, only one serotype has been recognised. In general, the organism possesses one heat-stable and four heatlabile somatic antigens, and three heat-labile extracellular antigens
(presumably enzymes) (Kusuda et al. 1978a ). The LPS comprises <1 % protein, 18–24 % sugar and 34–36 % fatty acids. The sugar component includes
hexose, heptose, pentose, 6-deoxyhexose, 2-keto-3-deoxyoctonate and hexosamine. The fatty acids include lauric acid, 3-hydroxy lauric acid, myristic acid
and palmitic acid (Salati et al. 1989a , b ; Hawke et al. 2003 ) .
10 Vibrios
which are approximately 1–2 mm in diameter after 72 h (Kusuda and Yamaoka
1972 ). Another approach, which has met with success, has enabled the recovery of
Ph. damselae subsp. piscicida from water in the vicinity of fi sh. The method
involved fi ltering 250 ml volumes of water through 0.45 μm cellulose nitrate fi lters,
before transfer (of the fi lters) to 2216E agar supplemented with 1 % (w/v) mannitol
and 0.5 % (w/v) phenol red. The non-fermenting Ph. damselae subsp. piscicida produced red colonies (Reali et al. 1997 ). With this method, the pathogen was detected
on sea bass 8-days before the outbreak of disease.
Characteristics of the Pathogen
In addition to the articles about pasteurellosis/pseudotuberculosis, there are also
some reports indicating the presence of fi sh pathogenic Pasteurella in Great Britain
(Ajmal and Hobbs 1967 ) and Norway (Håstein and Bullock 1976 ). However, it is
possible that these organisms should have been identifi ed as atypical Aer. salmonicida (see Paterson et al. 1980 ).
Box 10.2: Photobacterium damselae subsp. piscicida
Cultures comprise fairly unreactive, Gram-negative, non-motile, fermentative
rods of 0.5 × 1.5 μm in size, with pronounced bipolar staining. Pleomorphism
may be evident, especially in older cultures. Catalase and oxidase are produced, but not alanine deaminase, ß-galactosidase, H 2 S, indole, lysine or ornithine decarboxylase or phenylalanine deaminase. Nitrates are not reduced.
The methyl red test is strongly positive, whereas the Voges Proskauer reaction
is weakly positive. Arginine and Tween 80 are degraded, but not blood, casein,
chitin, gelatin, starch or urea. Growth occurs at 25–30 °C but not 10 or 37 °C,
in 0.5–3.0 % (w/v) sodium chloride and at pH 5.5–8.0, but not on MacConkey
agar or in potassium cyanide broth. Uniform turbidity is recorded in broth
cultures. Sodium citrate is not utilised. Acid is produced from fructose, galactose, glucose (weak) and mannose, but not amygdalin, arabinose, dulcitol,
inositol, lactose, maltose, mannitol, melibiose, rhamnose, salicin, sorbitol,
sucrose or trehalose. Unfortunately, the G + C ratio of the DNA has not been
determined for any bona fi de strains. So far, only one serotype has been recognised. In general, the organism possesses one heat-stable and four heatlabile somatic antigens, and three heat-labile extracellular antigens
(presumably enzymes) (Kusuda et al. 1978a ). The LPS comprises <1 % protein, 18–24 % sugar and 34–36 % fatty acids. The sugar component includes
hexose, heptose, pentose, 6-deoxyhexose, 2-keto-3-deoxyoctonate and hexosamine. The fatty acids include lauric acid, 3-hydroxy lauric acid, myristic acid
and palmitic acid (Salati et al. 1989a , b ; Hawke et al. 2003 ) .
10 Vibrios