616
Moritella viscosa (= V. viscosus)
Characteristics of the Disease
Ulcers, of indeterminate cause, appeared on the fl anks of Atlantic salmon in seawater during winter (= winter ulcer disease), principally in Iceland and Norway (Salte
et al. 1994 ; Lunder et al. 1995 ; Benediktsdóttir et al. 1998 ), and more recently in
Scotland. Since its fi rst recognition, a view has emerged that two new vibrios , V.
wodanis and Moritella viscosa, are responsible (Benediktsdóttir et al. 2000 ).
Moritella viscosa was subsequently recovered from two diseased (with skin lesions)
farmed Atlantic cod in Norway (Colquhoun et al. 2004 ).
Characteristics of the Pathogen
Two groups of psychrotrophic bacteria were recovered; one homogeneous group
was determined to be closest to Moritella marina (43 % re-association by DNA:
DNA hybridisation), and hence was initially named as V. viscosus (Lunder et al.
2000 ). However, by 16S rDNA sequencing, the closest match was Moritella HAR
08 and HAR 013 (Lunder et al. 2000 ) and Moritella marina (99.1 % sequence
homology. Hence, the organism was re-classifi ed to Moritella, as Moritella viscosa
(Benediktsdóttir et al. 2000 ). Phenotypic and genotypic variation has been reported
among isolates (Grove et al. 2010 ).
Box 11.10: Moritella viscosa
Colonies on bovine blood agar containing 2 % (w/v) NaCl of up to 1 mm in
diameter after 24 h at 15 °C or 22 °C are viscous (and adhere to the medium),
translucent and grey in colour that contain motile, fermentative Gram-negative
rods that produce alkaline phosphatase, caprylate esterase, catalase, lysine
decarboxylase and oxidase but not arginine dihydrolase, chemotrypsinase,
α-fucosidase, indole, α- or ß-, α-mannosidase or ornithine decarboxylase,
degrade bovine blood (ß-haemolysis), casein, DNA, gelatin, lecithin, starch,
Tween 80 and urea but not aesculin, alginate, produce acid from galactose and
glucose but not L-arabinose, cellobiose, glycerol, inositol, lactose, mannitol,
mannose, melibiose, raffi nose, L-rhamnose or xylose, grow at 15 °C (and also
survive freezing) in 1–4 % (w/v) NaCl, are sensitive to the vibriostatic agent,
O/129, and are negative for the methyl red test and Voges Proskauer reaction.
All isolates examined harbour one or more plasmids. The G + C ratio of the
DNA is 42.5 mol% (Lunder et al. 2000 ).
11 Miscellaneous Pathogens
Moritella viscosa (= V. viscosus)
Characteristics of the Disease
Ulcers, of indeterminate cause, appeared on the fl anks of Atlantic salmon in seawater during winter (= winter ulcer disease), principally in Iceland and Norway (Salte
et al. 1994 ; Lunder et al. 1995 ; Benediktsdóttir et al. 1998 ), and more recently in
Scotland. Since its fi rst recognition, a view has emerged that two new vibrios , V.
wodanis and Moritella viscosa, are responsible (Benediktsdóttir et al. 2000 ).
Moritella viscosa was subsequently recovered from two diseased (with skin lesions)
farmed Atlantic cod in Norway (Colquhoun et al. 2004 ).
Characteristics of the Pathogen
Two groups of psychrotrophic bacteria were recovered; one homogeneous group
was determined to be closest to Moritella marina (43 % re-association by DNA:
DNA hybridisation), and hence was initially named as V. viscosus (Lunder et al.
2000 ). However, by 16S rDNA sequencing, the closest match was Moritella HAR
08 and HAR 013 (Lunder et al. 2000 ) and Moritella marina (99.1 % sequence
homology. Hence, the organism was re-classifi ed to Moritella, as Moritella viscosa
(Benediktsdóttir et al. 2000 ). Phenotypic and genotypic variation has been reported
among isolates (Grove et al. 2010 ).
Box 11.10: Moritella viscosa
Colonies on bovine blood agar containing 2 % (w/v) NaCl of up to 1 mm in
diameter after 24 h at 15 °C or 22 °C are viscous (and adhere to the medium),
translucent and grey in colour that contain motile, fermentative Gram-negative
rods that produce alkaline phosphatase, caprylate esterase, catalase, lysine
decarboxylase and oxidase but not arginine dihydrolase, chemotrypsinase,
α-fucosidase, indole, α- or ß-, α-mannosidase or ornithine decarboxylase,
degrade bovine blood (ß-haemolysis), casein, DNA, gelatin, lecithin, starch,
Tween 80 and urea but not aesculin, alginate, produce acid from galactose and
glucose but not L-arabinose, cellobiose, glycerol, inositol, lactose, mannitol,
mannose, melibiose, raffi nose, L-rhamnose or xylose, grow at 15 °C (and also
survive freezing) in 1–4 % (w/v) NaCl, are sensitive to the vibriostatic agent,
O/129, and are negative for the methyl red test and Voges Proskauer reaction.
All isolates examined harbour one or more plasmids. The G + C ratio of the
DNA is 42.5 mol% (Lunder et al. 2000 ).
11 Miscellaneous Pathogens