492
Characteristics of the Pathogen
The organism matched the description of Pseudomonas (Palleroni 2005 ), and
approximated Ps. pseudoalcaligenes as determined from the probability matrix of
Holmes et al. ( 1986 ). The only discrepancies concerned the degradation of gelatin
and starch, and the production of ornithine decarboxylase.
Epizootiology
Pseudomonads occur in polluted/eutrophic freshwater, which is considered to be the
source of Ps. pseudoalcaligenes (Austin and Stobie 1992 ). Moreover, it was apparent that the fi sh farm waters received sewage from a neighbouring septic tank
(B. Austin, unpublished data).
Pathogenicity
Injection of 10
5 cells by i.p. or i.m. injection into rainbow trout (average
weight = 12 g), held at 15 °C, resulted in total mortalities within 7 days. Moribund
fi sh revealed the presence of haemorrhaging (internal and around the vent) and
ascitic fl uid in the peritoneal cavity (Austin and Stobie 1992 ).
Disease Control
Antimicrobial Compounds Antibiogrammes revealed sensitivity to oxytetracycline, oxolinic acid and potentiated sulphonamides (Austin and Stobie 1992 ).
Box 9.8: Pseudomonas pseudoalcaligenes
The cream-coloured colonies (with a “gummy” consistency) comprise motile
oxidative (alkali is produced) short Gram-negative rods, which produce arginine dihydrolase, catalase, ornithine decarboxylase and oxidase, but not
ß-galactosidase, H 2 S, indole, lysine decarboxylase or tryptophan deaminase,
degrade gelatin, tyrosine (with the production of melanin) and Tween 80, but
not DNA, starch or urea, and grow at 15 and 25 °C, but not at 4 or 40 °C. Acid
is produced from arabinose and glucose, but not from amygdalin, inositol,
mannose, melibiose, rhamnose or sorbitol. Citrate is utilised. The Voges
Proskauer reaction is negative.
9 Pseudomonads
Characteristics of the Pathogen
The organism matched the description of Pseudomonas (Palleroni 2005 ), and
approximated Ps. pseudoalcaligenes as determined from the probability matrix of
Holmes et al. ( 1986 ). The only discrepancies concerned the degradation of gelatin
and starch, and the production of ornithine decarboxylase.
Epizootiology
Pseudomonads occur in polluted/eutrophic freshwater, which is considered to be the
source of Ps. pseudoalcaligenes (Austin and Stobie 1992 ). Moreover, it was apparent that the fi sh farm waters received sewage from a neighbouring septic tank
(B. Austin, unpublished data).
Pathogenicity
Injection of 10
5 cells by i.p. or i.m. injection into rainbow trout (average
weight = 12 g), held at 15 °C, resulted in total mortalities within 7 days. Moribund
fi sh revealed the presence of haemorrhaging (internal and around the vent) and
ascitic fl uid in the peritoneal cavity (Austin and Stobie 1992 ).
Disease Control
Antimicrobial Compounds Antibiogrammes revealed sensitivity to oxytetracycline, oxolinic acid and potentiated sulphonamides (Austin and Stobie 1992 ).
Box 9.8: Pseudomonas pseudoalcaligenes
The cream-coloured colonies (with a “gummy” consistency) comprise motile
oxidative (alkali is produced) short Gram-negative rods, which produce arginine dihydrolase, catalase, ornithine decarboxylase and oxidase, but not
ß-galactosidase, H 2 S, indole, lysine decarboxylase or tryptophan deaminase,
degrade gelatin, tyrosine (with the production of melanin) and Tween 80, but
not DNA, starch or urea, and grow at 15 and 25 °C, but not at 4 or 40 °C. Acid
is produced from arabinose and glucose, but not from amygdalin, inositol,
mannose, melibiose, rhamnose or sorbitol. Citrate is utilised. The Voges
Proskauer reaction is negative.
9 Pseudomonads