406
Characteristics of the Pathogen
From these characteristics, the 50 isolates from turbot were equated with a new
species of Flavobacterium, as Fla. scophthalmum (Mudarris et al. 1994 ). With subsequent improvements in taxonomy, the species was transferred to the newly established genus Chryseobacterium, as Chrys. scophthalmum (Vandamme et al. 1994 ).
Epizootiology
Chrys. scophthalmum was found in the water, from which it is surmised that spread
to turbot occurred (Mudarris and Austin 1989 ).
Pathogenicity
Intraperitoneal injection of cell-free culture supernatants of Chrys. scophthalmum
resulted in clinical disease in turbot, with swollen oedematous gill lamellae, and
haemorrhaging in the stomach, gastro-intestinal tract, kidney and liver (Mudarris
and Austin 1989 ).
Disease Control
Antimicrobial Compounds Furazolidone, used by i.p. injection at 50 mg/kg body
weight of fi sh or by immersion (50 mg/l for 30 min daily for 10 days) was effective
at controlling mortalities caused by the organism (Mudarris and Austin 1989 ).
Box 7.5: Chryseobacterium scophthalmum
Colonies (2–3 mm in diameter after 48 h at 25 °C) contain orange-pigmented
(fl exirubin pigment) uniformly shaped, short, fermentative Gram-negative
rods of approximately 2.0 × 0.8 μm in size. Gliding movement is exhibited.
Catalase and oxidase are produced, but not H 2 S, indole, or lysine or ornithine
decarboxylase. Nitrates are not reduced. The Voges Proskauer reaction is negative. Aesculin, casein, DNA, gelatin, tributyrin and tyrosine are degraded,
but not chitin or starch. Acid is produced from cellobiose and glucose, but not
arabinose, mannitol, raffi nose, sucrose or xylose. Thin sections reveal the
presence of a thick (43.5 nm) cell envelop, which could be mistaken for an
extracellular layer. The G + C ratio of the DNA is 31.7–34.2 moles % (Mudarris
and Austin 1989 ; Mudarris et al. 1994 ).
7 Flavobacteria and Cytophagas
Characteristics of the Pathogen
From these characteristics, the 50 isolates from turbot were equated with a new
species of Flavobacterium, as Fla. scophthalmum (Mudarris et al. 1994 ). With subsequent improvements in taxonomy, the species was transferred to the newly established genus Chryseobacterium, as Chrys. scophthalmum (Vandamme et al. 1994 ).
Epizootiology
Chrys. scophthalmum was found in the water, from which it is surmised that spread
to turbot occurred (Mudarris and Austin 1989 ).
Pathogenicity
Intraperitoneal injection of cell-free culture supernatants of Chrys. scophthalmum
resulted in clinical disease in turbot, with swollen oedematous gill lamellae, and
haemorrhaging in the stomach, gastro-intestinal tract, kidney and liver (Mudarris
and Austin 1989 ).
Disease Control
Antimicrobial Compounds Furazolidone, used by i.p. injection at 50 mg/kg body
weight of fi sh or by immersion (50 mg/l for 30 min daily for 10 days) was effective
at controlling mortalities caused by the organism (Mudarris and Austin 1989 ).
Box 7.5: Chryseobacterium scophthalmum
Colonies (2–3 mm in diameter after 48 h at 25 °C) contain orange-pigmented
(fl exirubin pigment) uniformly shaped, short, fermentative Gram-negative
rods of approximately 2.0 × 0.8 μm in size. Gliding movement is exhibited.
Catalase and oxidase are produced, but not H 2 S, indole, or lysine or ornithine
decarboxylase. Nitrates are not reduced. The Voges Proskauer reaction is negative. Aesculin, casein, DNA, gelatin, tributyrin and tyrosine are degraded,
but not chitin or starch. Acid is produced from cellobiose and glucose, but not
arabinose, mannitol, raffi nose, sucrose or xylose. Thin sections reveal the
presence of a thick (43.5 nm) cell envelop, which could be mistaken for an
extracellular layer. The G + C ratio of the DNA is 31.7–34.2 moles % (Mudarris
and Austin 1989 ; Mudarris et al. 1994 ).
7 Flavobacteria and Cytophagas