363
Pathogenicity
Laboratory-based studies confi rmed pathogenicity for striped bass (LD 50 = 1 × 10
5
cells) [LD 50 in rainbow trout = 5 × 10
3 cells] with death occurring 1–3 or 1–7 days
following administration of the cells via the i.m. or i.p. route, respectively (Baya
et al. 1992 ). Experimentally infected fi sh displayed muscle necrosis and some signs
of haemorrhagic septicaemia. Further work indicated a role for ECP, which possessed marked proteolytic and phospholipase activity. In fi sh, the ECP caused a
cytotoxic response, with mortality occurring 24–48 h after administration. Here, the
LD 50 dose for rainbow trout and striped bass was 0.4 and 4.8 μg of protein/g of fi sh,
respectively (Baya et al. 1992 ).
Disease Control
Antimicrobial Compounds Isolates were sensitive to fl umequine, oxolinic acid
and potentiated sulphonamides (Baya et al. 1992 ).
Serratia plymuthica
Characteristics of the Disease
During September to December 1987, a new pathogen was associated with diseased
rainbow trout fi ngerlings (average weight = 7 g) in a hatchery in Northwestern
Spain. Progressive low level mortalities (cumulative total = 35 % of the stock) were
reported, with which there appeared to be a correlation with rainfall (Nieto et al.
1990 ). Then in 1992, a similar organism was associated with skin lesions in farmed
rainbow trout in Scotland (Austin and Stobie 1992 ). In this disease outbreak, there
was an association with pollution by domestic sewage, i.e. leakage from a septic
tank. Nieto et al. ( 1990 ) noted that diseased fi sh did not display any external or
internal clinical signs. However in Scotland, the diseased fi sh possessed extensive
skin lesions over the entire fl ank, from the operculum to the tail (Austin and Stobie
1992 ). In Poland, the organism has been recovered from 42 Atlantic salmon, rainbow trout and sea trout farms since 1996 (Grawinski and Antychowicz 2001 ).
Isolation
Pure culture growth was recovered from the kidney and liver following inoculation
of TSA with incubation at 22 °C for 7 days (Austin and Stobie 1992 ).
Serratia plymuthica
Pathogenicity
Laboratory-based studies confi rmed pathogenicity for striped bass (LD 50 = 1 × 10
5
cells) [LD 50 in rainbow trout = 5 × 10
3 cells] with death occurring 1–3 or 1–7 days
following administration of the cells via the i.m. or i.p. route, respectively (Baya
et al. 1992 ). Experimentally infected fi sh displayed muscle necrosis and some signs
of haemorrhagic septicaemia. Further work indicated a role for ECP, which possessed marked proteolytic and phospholipase activity. In fi sh, the ECP caused a
cytotoxic response, with mortality occurring 24–48 h after administration. Here, the
LD 50 dose for rainbow trout and striped bass was 0.4 and 4.8 μg of protein/g of fi sh,
respectively (Baya et al. 1992 ).
Disease Control
Antimicrobial Compounds Isolates were sensitive to fl umequine, oxolinic acid
and potentiated sulphonamides (Baya et al. 1992 ).
Serratia plymuthica
Characteristics of the Disease
During September to December 1987, a new pathogen was associated with diseased
rainbow trout fi ngerlings (average weight = 7 g) in a hatchery in Northwestern
Spain. Progressive low level mortalities (cumulative total = 35 % of the stock) were
reported, with which there appeared to be a correlation with rainfall (Nieto et al.
1990 ). Then in 1992, a similar organism was associated with skin lesions in farmed
rainbow trout in Scotland (Austin and Stobie 1992 ). In this disease outbreak, there
was an association with pollution by domestic sewage, i.e. leakage from a septic
tank. Nieto et al. ( 1990 ) noted that diseased fi sh did not display any external or
internal clinical signs. However in Scotland, the diseased fi sh possessed extensive
skin lesions over the entire fl ank, from the operculum to the tail (Austin and Stobie
1992 ). In Poland, the organism has been recovered from 42 Atlantic salmon, rainbow trout and sea trout farms since 1996 (Grawinski and Antychowicz 2001 ).
Isolation
Pure culture growth was recovered from the kidney and liver following inoculation
of TSA with incubation at 22 °C for 7 days (Austin and Stobie 1992 ).
Serratia plymuthica