614
Isolation
Pure culture growth of round, raised, translucent, mucoid colonies developed in
48 h of incubation at 22 °C of kidney, liver and pancreas tissue on TSA (Baya et al.
1990 ).
Characteristics of the Pathogen
A bacterium was recovered as pure culture growth , and equated with Moraxella
(Baya et al. 1990 ).
Whereas similarities to Moraxella were noted (Juni and Bøvre 2005 ), the organism strongly resembled the Acinetobacter described by Roald and Hastein ( 1980 ).
Indeed, the major differences concerned acid production from maltose. Clearly, the
precise taxonomic position of both organisms must await further study.
Epizootiology
It may be assumed that the organism constitutes part of the aquatic microfl ora.
Pathogenicity
Laboratory-based experiments revealed that the organism was pathogenic to rainbow trout and striped bass, with an LD 50 dose of 10
5 –10
6 cells (Baya et al. 1990 ).
Disease Control
Antimicrobial Compounds The pathogen was susceptible to chloramphenicol,
nitrofurantoin, oxolinic acid, penicillin and tetracycline (Baya et al. 1990 ).
Box 11.8: Moraxella sp.
Cultures comprise non-motile, short (0.8–1.0 × 1.3 μm in size) nonfermentative paired rods with pronounced bipolar staining. Catalase and oxidase are produced, but not so arginine dihydrolase, ß-galactosidase, H 2 S,
indole or lysine or ornithine decarboxylase. Sheep’s blood is degraded, but
not gelatin or urea. Citrate utilisation, nitrate reduction and the Voges
Proskauer reaction are negative. Acid is produced weakly from galactose and
mannose, but not from amygdalin, arabinose, glucose, inositol, lactose, maltose, mannitol, rhamnose, salicin, sorbitol or sucrose.
11 Miscellaneous Pathogens
Isolation
Pure culture growth of round, raised, translucent, mucoid colonies developed in
48 h of incubation at 22 °C of kidney, liver and pancreas tissue on TSA (Baya et al.
1990 ).
Characteristics of the Pathogen
A bacterium was recovered as pure culture growth , and equated with Moraxella
(Baya et al. 1990 ).
Whereas similarities to Moraxella were noted (Juni and Bøvre 2005 ), the organism strongly resembled the Acinetobacter described by Roald and Hastein ( 1980 ).
Indeed, the major differences concerned acid production from maltose. Clearly, the
precise taxonomic position of both organisms must await further study.
Epizootiology
It may be assumed that the organism constitutes part of the aquatic microfl ora.
Pathogenicity
Laboratory-based experiments revealed that the organism was pathogenic to rainbow trout and striped bass, with an LD 50 dose of 10
5 –10
6 cells (Baya et al. 1990 ).
Disease Control
Antimicrobial Compounds The pathogen was susceptible to chloramphenicol,
nitrofurantoin, oxolinic acid, penicillin and tetracycline (Baya et al. 1990 ).
Box 11.8: Moraxella sp.
Cultures comprise non-motile, short (0.8–1.0 × 1.3 μm in size) nonfermentative paired rods with pronounced bipolar staining. Catalase and oxidase are produced, but not so arginine dihydrolase, ß-galactosidase, H 2 S,
indole or lysine or ornithine decarboxylase. Sheep’s blood is degraded, but
not gelatin or urea. Citrate utilisation, nitrate reduction and the Voges
Proskauer reaction are negative. Acid is produced weakly from galactose and
mannose, but not from amygdalin, arabinose, glucose, inositol, lactose, maltose, mannitol, rhamnose, salicin, sorbitol or sucrose.
11 Miscellaneous Pathogens