621
Isolation
Homogenates of whole fi sh (prepared in quarter strength Ringer’s buffer; Oxoid)
and, where possible, loopfuls of kidney, liver, spleen, ascitic fl uid and material from
surface lesions were spread over the surface of a variety of media, including blood
agar (5 % v/v bovine blood in Gibco blood agar base), cytophaga agar, KDM2, L-F
medium (Appendix in Chap. 12 ) and TSA, with incubation aerobically at 22 °C for
up to 14 days. Purple-pigmented colonies were apparent after 3 days.
Characteristics of the Pathogen
Pure cultures have been recovered and characterised:
From these traits, the organisms were identifi ed as typical (Table 11.1 ; from
Northern Ireland) and atypical (Table 11.1 ; from Scotland) Janthinobacterium lividum (Sneath 1984 ; Logan 1989 ).
Epizootiology
Typical and atypical forms of J. lividum are regarded as part of the normal microfl ora of fresh water (Sneath 1984 ) and soil (Moss and Ryall 1980 ). Therefore, there
would be a ready inoculum of the pathogen in the environment around fi sh.
Pathogenicity
Injection of 5 × 10
2 cells/fi sh i.m. and i.p. resulted in 100 % mortalities within
14 days. Generally, infected rainbow trout fry and fi ngerlings became lethargic
within 2 days. Moribund and newly dead fi sh displayed pale (almost white) gills,
elongated spleen, pale liver, swollen watery kidney, internal haemorrhaging, pronounced gastro-enteritis, and slight amounts of ascitic fl uid in the peritoneal cavity
(Austin et al. 1992 ).
Box 11.12: Janthinobacterium lividum
Cultures comprise purple-pigmented motile Gram-negative strictly aerobic
rods, which produce arginine dihydrolase, catalase and oxidase, but not
ß-galactosidase, indole or tryptophan deaminase. Nitrates are reduced, and
the Voges Proskauer reaction is positive. Gelatin, but not urea, is degraded.
Growth occurs at 4–30 °C but not 37 °C, and in 0–2 % but not 3 % (w/v)
sodium chloride. Caprate, citrate, malate, maltose, mannitol, mannose and
phenylacetate are utilised, but not N-acetyl glucosamine or adipate.
Oxalobacteraceae Representative
Isolation
Homogenates of whole fi sh (prepared in quarter strength Ringer’s buffer; Oxoid)
and, where possible, loopfuls of kidney, liver, spleen, ascitic fl uid and material from
surface lesions were spread over the surface of a variety of media, including blood
agar (5 % v/v bovine blood in Gibco blood agar base), cytophaga agar, KDM2, L-F
medium (Appendix in Chap. 12 ) and TSA, with incubation aerobically at 22 °C for
up to 14 days. Purple-pigmented colonies were apparent after 3 days.
Characteristics of the Pathogen
Pure cultures have been recovered and characterised:
From these traits, the organisms were identifi ed as typical (Table 11.1 ; from
Northern Ireland) and atypical (Table 11.1 ; from Scotland) Janthinobacterium lividum (Sneath 1984 ; Logan 1989 ).
Epizootiology
Typical and atypical forms of J. lividum are regarded as part of the normal microfl ora of fresh water (Sneath 1984 ) and soil (Moss and Ryall 1980 ). Therefore, there
would be a ready inoculum of the pathogen in the environment around fi sh.
Pathogenicity
Injection of 5 × 10
2 cells/fi sh i.m. and i.p. resulted in 100 % mortalities within
14 days. Generally, infected rainbow trout fry and fi ngerlings became lethargic
within 2 days. Moribund and newly dead fi sh displayed pale (almost white) gills,
elongated spleen, pale liver, swollen watery kidney, internal haemorrhaging, pronounced gastro-enteritis, and slight amounts of ascitic fl uid in the peritoneal cavity
(Austin et al. 1992 ).
Box 11.12: Janthinobacterium lividum
Cultures comprise purple-pigmented motile Gram-negative strictly aerobic
rods, which produce arginine dihydrolase, catalase and oxidase, but not
ß-galactosidase, indole or tryptophan deaminase. Nitrates are reduced, and
the Voges Proskauer reaction is positive. Gelatin, but not urea, is degraded.
Growth occurs at 4–30 °C but not 37 °C, and in 0–2 % but not 3 % (w/v)
sodium chloride. Caprate, citrate, malate, maltose, mannitol, mannose and
phenylacetate are utilised, but not N-acetyl glucosamine or adipate.
Oxalobacteraceae Representative