484
Characteristics of the Pathogen
To date, there has been only one report of Pseudomonas chlororaphis as a fi sh
pathogen. This involved a heavy mortality among farmed Amago trout
( Oncorhynchus rhodurus ) in Japan (Hatai et al. 1975 ). For the present, it is uncertain whether Ps. chlororaphis represents an emerging problem, or a secondary
(opportunistic) invader of already diseased hosts.
The isolates matched the description of Ps. chlororaphis , insofar as cultures
comprised Gram-negative motile rods, which produced distinctive colonies. These
produced green pigment, which crystallised as needles in the colonies (Stanier et al.
1966 ; Palleroni 1984 ). Other phenotypic traits were not reported, although the
authors inferred that further tests had been carried out, and that these agreed with
the defi nition of Ps. chlororaphis .
Epizootiology
Ps. chlororaphis occurs in water (Palleroni 1984 ), which is assumed to be the reservoir of infection. No other information is available.
Pathogenicity
The isolates from Amago trout and the neotype culture of Ps. chlororaphis were
pathogenic to carp, eels and trout, following challenge by i.m. injection. Total mortalities occurred within 48 h at a water temperature of 22 °C, with disease symptoms
paralleling those on the naturally infected fi sh. However, the pathogenicity mechanism is unknown (Hatai et al. 1975 ).
Pseudomonas fl uorescens
Characteristics of the Diseases
Ps. fl uorescens is a dominant component of the freshwater ecosystem (Allen et al.
1983 ). At various times, Ps. fl uorescens has been considered as a fi sh spoilage
organism (Shewan et al. 1960 ), a contaminant or secondary invader of damaged fi sh
tissues (Otte 1963 ), as well as a primary, but poor pathogen (Roberts and Horne
1978 ). It has been reported to cause disease in a wide range of fi sh species, including silver carp ( Hypophthalmichthys molitrix ) and bighead ( Aristichthys nobilis )
(Csaba et al. 1981 ; Markovic et al. 1996 ), goldfi sh ( Carassius auratus ) (Bullock
9 Pseudomonads
Characteristics of the Pathogen
To date, there has been only one report of Pseudomonas chlororaphis as a fi sh
pathogen. This involved a heavy mortality among farmed Amago trout
( Oncorhynchus rhodurus ) in Japan (Hatai et al. 1975 ). For the present, it is uncertain whether Ps. chlororaphis represents an emerging problem, or a secondary
(opportunistic) invader of already diseased hosts.
The isolates matched the description of Ps. chlororaphis , insofar as cultures
comprised Gram-negative motile rods, which produced distinctive colonies. These
produced green pigment, which crystallised as needles in the colonies (Stanier et al.
1966 ; Palleroni 1984 ). Other phenotypic traits were not reported, although the
authors inferred that further tests had been carried out, and that these agreed with
the defi nition of Ps. chlororaphis .
Epizootiology
Ps. chlororaphis occurs in water (Palleroni 1984 ), which is assumed to be the reservoir of infection. No other information is available.
Pathogenicity
The isolates from Amago trout and the neotype culture of Ps. chlororaphis were
pathogenic to carp, eels and trout, following challenge by i.m. injection. Total mortalities occurred within 48 h at a water temperature of 22 °C, with disease symptoms
paralleling those on the naturally infected fi sh. However, the pathogenicity mechanism is unknown (Hatai et al. 1975 ).
Pseudomonas fl uorescens
Characteristics of the Diseases
Ps. fl uorescens is a dominant component of the freshwater ecosystem (Allen et al.
1983 ). At various times, Ps. fl uorescens has been considered as a fi sh spoilage
organism (Shewan et al. 1960 ), a contaminant or secondary invader of damaged fi sh
tissues (Otte 1963 ), as well as a primary, but poor pathogen (Roberts and Horne
1978 ). It has been reported to cause disease in a wide range of fi sh species, including silver carp ( Hypophthalmichthys molitrix ) and bighead ( Aristichthys nobilis )
(Csaba et al. 1981 ; Markovic et al. 1996 ), goldfi sh ( Carassius auratus ) (Bullock
9 Pseudomonads